No full-text available
To read the full-text of this research,
you can request a copy directly from the authors.
Desiccation sensitivity in orthodox and recalcitrant seeds in relation to development.
Abstract
This multi-author book gives a comprehensive account of desiccation and plant survival, and of how plant cells deal with extreme water stress. There is a general introduction on desiccation, and then four sections dealing with: The technical background to desiccation studies; the frequency and levels of dehydration stress tolerance in biological systems; mechanisms of damage and tolerance; and a brief retrospect and prospect. Orthodox and recalcitrant seeds, pollen and spores, vegetative parts, and other plant tissues are covered in detail.
... At maturity (or harvest), they contain no more than 10-15% water and survive drying to very low moisture content (3-5%). They therefore tolerate subsequent storage at sub-zero temperatures [33]. Orthodox seeds acquire desiccation tolerance relatively early during their development and usually before the maturation drying phase. ...
... Orthodox seeds acquire desiccation tolerance relatively early during their development and usually before the maturation drying phase. Several metabolic changes occur with respect to the protection of seed cells against dehydration damage [18,26,[33][34][35]. In particular, carbohydrate metabolism [36,37] and specific proteins (dehydrins, late embryogenesis abundant proteins: LEA, and heat shock proteins: HSPs) [33] seem to be involved in this process. ...
... Several metabolic changes occur with respect to the protection of seed cells against dehydration damage [18,26,[33][34][35]. In particular, carbohydrate metabolism [36,37] and specific proteins (dehydrins, late embryogenesis abundant proteins: LEA, and heat shock proteins: HSPs) [33] seem to be involved in this process. Some soluble sugars, such as sucrose and oligosaccharides (raffinose, stachyose, and verbascose), might also play an important part in this process by facilitating the stabilization of lipids and proteins in cell membranes or by promoting the vitrification of water and then the protection of cytosolic structures [35,37,38]. ...
Seeds are classified as either: orthodox, seeds that tolerate dehydration; recalcitrant, seeds that are high in moisture content and cannot withstand intensive desiccation; or intermediate, seeds that survive dehydration but die during dry storage at low temperatures. Seed lifespan depends on the seed category and also varies from one species to another. The rate of loss of vigor and viability of orthodox seeds depends mainly on temperature and seed moisture content (MC); the lower the MC and storage temperature, the longer the longevity. Ultimately, storage in liquid nitrogen or seed ultra-drying by well-adapted processes should allow for long-term storage. The ageing of orthodox seeds is associated with numerous forms of cellular and metabolic damage (membrane integrity, energy metabolism, and the impairment of DNA, RNA, and proteins) in which reactive oxygen species play a prominent role. Interestingly, priming treatment can reinvigorate aged seeds by restoring the antioxidant systems. The storage of recalcitrant seeds is very difficult since they must be placed in a wet medium to avoid dehydration and at temperatures low enough to prevent germination but warm enough to avoid chilling injury. A better understanding of the mechanisms involved in ageing is necessary to identify markers in order to estimate seed longevity.
... In orthodox seeds, desiccation tolerance is acquired during the three phases of development on the parent plant Vertucci and Farrant, 1995;Pammenter and Berjak, 1999), viz., histodifferentiation, reserve deposition, and maturation drying (Kermode and Finch-Savage, 2002;Bewley et al., 2013;). During the first phase, undifferentiated cells divide and develop into function-specific tissues. ...
... The second phase is when reserves in various forms are accumulated in the endosperm, or ultimately in the cotyledons, providing nutrients that sustain seedling development (Bewley et al., 2013). Dry and fresh mass increase during the first two phases, and while the duration of dry matter accumulation varies across species it always terminates with the vascular connection between the parent plant and seed being severed at physiological maturity (Kermode and Finch-Savage, 2002). This stage coincides with a metabolic shutdown accompanied by the start of water loss (and hence reduction in fresh mass) as part of the maturation drying (third) phase (Vertucci and Farrant, 1995;Kermode and Finch-Savage, 2002). ...
... Dry and fresh mass increase during the first two phases, and while the duration of dry matter accumulation varies across species it always terminates with the vascular connection between the parent plant and seed being severed at physiological maturity (Kermode and Finch-Savage, 2002). This stage coincides with a metabolic shutdown accompanied by the start of water loss (and hence reduction in fresh mass) as part of the maturation drying (third) phase (Vertucci and Farrant, 1995;Kermode and Finch-Savage, 2002). Desiccation tolerance is acquired prior to maturation drying, and seeds are shed from the parent plant, usually upon completion of all three phases, and remain quiescent until water becomes available for germination (Farrant et al., 1993;Vertucci and Farrant, 1995;Kermode and Finch-Savage, 2002). ...
Species producing recalcitrant (desiccation sensitive) seeds are relatively common amongst woody species of tropical moist forests, and they provide a broad range of ecosystem services. In addition to the pressure imposed by forest destruction, these species are under a greater risk of regeneration failure due to the effects of climate change than species with orthodox (desiccation-tolerant) seeds. Orthodox seeds often are dormant and have the ability to form soil seed banks, enabling persistence through extended periods of low rainfall and high temperatures. In contrast, recalcitrant seeds are shed at a relatively high moisture content, generally are nondormant, and do not form a soil seed bank. However, many recalcitrant-seeded species can form a seedling bank, with survival dependent on regeneration under low light levels. The ability of large seeds, which is a common feature of recalcitrant seeds, to germinate in low light is a potentially valuable ecological adaptation associated with the formation of a seedling bank. Nonetheless, little is known about the sensitivity of recalcitrant seeds to germinate in varying light conditions; thus it is unclear how these species will respond to the combined impact of climate change and forest fragmentation. Some recalcitrant-seeded species time propagule dispersal to the main period of rainfall and have seeds that germinate quickly due to relatively thin seed coats (less investment in defense). However, studies on the thermal time for germination show that amongst trees recalcitrant seeds can be slower to germinate than orthodox seeds. Moreover, temperature optima and maxima for germination appear to be similar between the two groups of species. Thus the projected risks of increasing temperature on seed germination may be similar over a broad range of tree species. However, the sensitivity of recalcitrant seeds to drought conditions means that they are at greater risk of regeneration failure under many climate change scenarios than orthodox seeds.
... Many authors have suggested that a continuum between two states, namely, extreme orthodoxy and maximal recalcitrance, may be favored above two or three discretized strategies Pammenter, 1997, 2008;Sun, 1998;Pammenter and Berjak, 1999;Kermode and Finch-Savage, 2002;Berjak et al., 2004). The continuum concept accommodates the documented within-and between-species physiological and morphological variation and effects of seed provenance on seed desiccation tolerance (Daws et al., 2004(Daws et al., , 2006. ...
... Many authors have proposed a general evolutionary trend of increasing embryo size (development) and decreasing endosperm to acquire recalcitrant seeds among angiosperms (Martin, 1946;Berjak and Pammenter, 1997;Sun, 1998;Forbis et al., 2002;Kermode and Finch-Savage, 2002;Berjak et al., 2004). Based on this hypothesis, one would expect that a transition from orthodoxy to maximal recalcitrance among Cape Oxalis species would be a step-by-step assembly of traits associated with recalcitrance, where certain physiological and morphological traits (such as desiccation tolerance and consequently increased embryo size and decreased endosperm) are lost or acquired. ...
... Recalcitrant seeds have the ability to germinate immediately or soon after shedding, which may be advantageous in particular scenarios. If the seeds are shed under predictably favorable environmental conditions, such as the wet winter months of the Cape, germination success immediately after seed dispersal will be highly likely and loss of quiescence may become favorable (Kermode and Finch-Savage, 2002). These seeds are metabolically active when shed, which enables them to germinate, establish, and reach maturity much more rapidly than orthodox seeds (Kermode and Finch-Savage, 2002). ...
Premise:
Seed germination strategy has profound ecological and evolutionary consequences, with transitions between germination strategies receiving renewed recent attention. Oxalis from the Cape Flora, South Africa, has seeds with two contrasting germination strategies: orthodox and recalcitrant. The morphological gulf between these strategies (and potential intermediate morphologies) has been poorly quantified, with questions regarding their ecological function and evolution. We reconsidered this binary classification, emphasizing potential intermediate states.
Methods:
Seed physiological traits were used to assign strategies to 64 Oxalis species. We tested for morphological/phenological signal corresponding to defined strategies with cluster, principal component, K-means clustering and discriminant analyses.
Results:
We showed that an intermediate germination strategy does exist among Cape Oxalis, with two possible morphological groups within each strategy. These could reflect a continuum of germination states, where an ancestral orthodox strategy evolved toward a maximally recalcitrant peak, with a mosaic of intermediate states reflected in extant taxa.
Conclusions:
Environmental factors may affect germination strategy and distribution throughout the Cape because recalcitrant and intermediate species are confined to the winter rainfall region. They occupy specialized niches and may face adverse impacts under predicted climate change (hotter and drier winters), meriting focused future conservation.
... functional integrity of mitochondria in seeds during the desiccation process [3]. Furthermore, alterations in metabolic pathways, such as sugar metabolism, lipid metabolism, and dehydrins metabolism, have been reported to contribute to the desiccation sensitivity of various plant species [10,11]. ...
... Robert grouped seeds into orthodox and recalcitrant seeds according to their storage properties [2]. Orthodox seeds produce desiccation tolerance at late developmental stages [3]. Due to desiccation tolerance, the orthodox seeds can be stored for a long period of time under extreme environmental or artificial conditions [4]. ...
Panax notoginseng (Burk.) F. H. Chen, a species of the genus Panax, radix has been traditionally used to deal with various hematological diseases and cardiovascular diseases since ancient times in East Asia. P. notoginseng produces recalcitrant seeds which are sensitive to desiccation and difficult to store for a long time. However, few data are available on the mechanism of the desiccation sensitivity of P. notoginseng seeds. To gain a comprehensive perspective of the genes associated with desiccation sensitivity, cDNA libraries from seeds under control and desiccation processes were prepared independently for Illumina sequencing. The data generated a total of 70,189,896 reads that were integrated and assembled into 55,097 unigenes with a mean length of 783 bp. In total, 12,025 differentially expressed genes (DEGs) were identified during the desiccation process. Among these DEGs, a number of central metabolism, hormonal network-, fatty acid-, and ascorbate-glutathione-related genes were included. Our data provide a comprehensive resource for identifying the genes associated with the desiccation sensitivity of P. notoginseng seeds.
... Acquisition of desiccation tolerance is associated with events that mostly occur during the reserve accumulation phase (Bewley et al., 2013). In the case of recalcitrant seeds, although they have a similar pattern of development regarding the first two phases, they do not fully develop desiccation tolerance, are dispersed relatively wet (usually >40% water content, fresh weight), and do not present the maturation drying phase (Finch-Savage and Blake, 1994;Kermode and Finch-Savage, 2002). However, there are differences in the level of desiccation tolerated across RS species (Sun, 1999), within genera (Xia et al., 2012Ganatsas and Tsakaldimi, 2013;León-Lobos and Ellis, 2018;de Almeida Garcia Rodrigues et al., 2022), genotypes of the same species (Lamarca and Barbedo, 2015;Ganatsas et al., 2016), and even among seeds from the same genotype (Finch-Savage and Blake, 1994). ...
... In recalcitrant seeds, the level of desiccation tolerance can also vary according to the desiccation rate (Farrant et al., 1985;Ntuli et al., 2011), equilibrium dehydration method, and temperature (Sun and Liang, 2001). Because seeds increase their tolerance to desiccation as they advance in their development and lose water, the degree of maturity that they reach at the time of harvest or dispersal is one of the factors that affect their tolerance to desiccation (Berjak and Pammenter, 1997;Kermode and Finch-Savage, 2002). ...
Recalcitrant seeds are characterized by desiccation and freezing sensitivity, and short storage longevity. These physiological attributes obviate their ex situ conservation in conventional seed banks, where seeds are stored dry at sub-zero temperatures (typically, 15% relative humidity and-20 • C) for extended periods of time. Propagation of plants for field collections (e.g., botanical gardens, nurseries, and arboretums) is a valuable ex situ conservation option. However, these collections are relatively costly, require high maintenance, preserve limited genetic diversity and/or are directly exposed to biotic (e.g., pests) and abiotic (e.g., climatic) threats. Therefore, recalcitrant-seeded (RS) species are dependent on cryopreservation for their safe and long-term ex situ conservation. Different explant sources such as whole seeds, zygotic embryos, dormant buds, shoot tips, and pollen, can be used for plant propagation of RS species in field collections as well as for their cryopreservation. The success of the propagation or the cryopreservation of these explants often depends on their developmental status, vigor, and/or tolerance to desiccation and chilling/freezing. These attributes are modulated by the environment where the donor plant grows and we hypothesize that climate change, by affecting these biological attributes, would impact the success of explant propagation and cryopreservation. To support this hypothesis, we have reviewed how temperature changes and drought, the two main climate change scenarios, affect the main biological attributes that are directly involved in the success of ex situ conservation of tropical and temperate RS species. In general, increases in temperature and drought will negatively affect plant development in field collections and the quality of the explants used in cryopreservation. Consequently, field collections of RS species may need to be moved to more suitable places (e.g., higher latitudes/altitudes). Additionally, we may find a reduction in the success of cryopreservation of RS species germplasm directly harvested from field collections. However, we cannot always generalize these effects for all species since they often depend on the origin of the species (e.g., tropical and temperate species tend to respond to climate change differently), the genotype, the adaptive genetic potential of each population, and the severity of the environmental change. On the other hand, the increase in temperatures and water stress in donor plants at high-latitude areas and also some tropical environments may favor the production of seeds and seedlings better adapted to drying, and hence, increase the success of plant propagation and zygotic embryo cryopreservation.
... These results confirm the damage caused by desiccation in the structure of cells as well as membranes. Membrane integrity is critically important for seed viability, since any improper rupture caused by desiccation can have immediate consequences for seeds during rehydration (Kermode;Finch-Savage 2002). ...
... These results confirm the damage caused by desiccation in the structure of cells as well as membranes. Membrane integrity is critically important for seed viability, since any improper rupture caused by desiccation can have immediate consequences for seeds during rehydration (Kermode;Finch-Savage 2002). ...
... Recently, NAD(P) concentrations and their redox status were reported to be involved in desiccation tolerance in the seeds of the two Acer seeds because Norway maple contained high NADPH concentrations, accumulated NAD + , and displayed a low and constant NAD(P)H/NAD(P) + ratio in contrast to sycamore seeds [53]. Interestingly, during the germination process, desiccation tolerance is progressively lost [62,63]. Thus, it was necessary to determine whether Norway maple seeds are still better protected at germination stages in terms of redox regulation emphasized at the concentrations of NAD(P), Asc, and glutathione redox couples and their redox states. ...
... Distinct strategies of redox regulation displayed in both species throughout germination eventually contributed to equilibrated E GSSG/ 2GSH at the beginning of the early development of sycamore seedlings (Fig 7). Desiccation tolerance is lost in orthodox seeds before the seedling stage [62,63]. Thus, the redox control of plant growth associated with cell proliferation and cell differentiation is putatively more unified at the seedling stage, even originating from initially contrasting seeds. ...
Seed germination is a complex process enabling plant reproduction. Germination was found to be regulated at the proteome, metabolome and hormonal levels as well as via discrete post-translational modification of proteins including phosphorylation and carbonylation. Redox balance is also involved but less studied. Acer seeds displaying orthodox and recalcitrant characteristics were investigated to determine the levels of redox couples of nicotinamide adenine dinucleotide (NAD) phosphate (NADP) and integrated with the levels of ascorbate and glutathione. NAD and NADP concentrations were higher in Norway maple seeds and exceptionally high at the germinated stage, being the most contrasting parameter between germinating Acer seeds. In contrast, NAD(P)H/NAD(P) ⁺ ratios were higher in sycamore seeds, thus exhibiting higher reducing power. Despite distinct concentrations of ascorbate and glutathione, both seed types attained in embryonic axes and cotyledons had similar ratios of reduced/oxidized forms of ascorbate and half-cell reduction potential of glutathione at the germinated stage. Both species accomplished germination displaying different strategies to modulate redox status. Sycamore produced higher amounts of ascorbate and maintained pyridine nucleotides in reduced forms. Interestingly, lower NAD(P) concentrations limited the regeneration of ascorbate and glutathione but dynamically drove metabolic reactions, particularly in this species, and contributed to faster germination. We suggest that NAD(P) is an important player in regulating redox status during germination in a distinct manner in Norway maple and sycamore seeds.
... Hydration allows desiccation-tolerant seeds to gradually acquire the high metabolic rate required for germination (Kermode and Finch-Savage 2002). Contrarily, the high metabolic rate of the desiccation-sensitive seeds generally leads them to germinate soon in a high-humidity environment without extra uptake of water (Berjak and Pammenter 2013;Kermode and Finch-Savage 2002). ...
... Hydration allows desiccation-tolerant seeds to gradually acquire the high metabolic rate required for germination (Kermode and Finch-Savage 2002). Contrarily, the high metabolic rate of the desiccation-sensitive seeds generally leads them to germinate soon in a high-humidity environment without extra uptake of water (Berjak and Pammenter 2013;Kermode and Finch-Savage 2002). The seeds of these species are generally indifferent to light; hence, their prompt germination produces a seedling bank rather than a seed bank (Long et al. 2015;Vázquez-Yanes and Orozco-Segovia 1993). ...
Seed priming increases the vigor of seeds and seedlings through metabolic and biochemical processes occurring during controlled hydration, followed by dehydration. In the field, seeds are exposed to hydration-dehydration events in and on the soil after dispersal, as in seed priming. Nevertheless, seed priming has been sparsely tested on desiccation-sensitive seeds, which are vulnerable to climate change effects. We evaluated the effect of two priming methods on seeds from two tropical rainforest species: Cupania glabra and Cymbopetalum baillonii. For hydropriming, the seeds were fully hydrated and then dehydrated to three dehydration levels. For natural priming, the seeds were buried for 12 days in either closed forest or forest gap. Primed seeds were sown in 1% agar medium and placed in an environmental chamber. The growth of the seedlings from the highest germination priming treatments was evaluated for 1 year in the field. Our results showed that for C. glabra and C. baillonii, hydroprimed seeds varied in their germination response, depending on the degree of their dehydration. However, for C. baillonii, hydropriming seems to invigorate seeds, compared to non-imbibed seeds of the same dehydration level. Natural priming increased germination speed in both species without any difference between closed forest and forest gap. Moreover, seeds with natural priming had a higher final germination percentage than seeds with hydropriming. Seedlings from seeds with natural priming showed a higher growth rate than the controls in both species, whereas hydropriming produced a similar effect in C. glabra. Both priming methods could be used for restoration practices with the studied species, natural priming being a novel method. The ecological implications of priming in desiccation sensitive seeds are discussed in this study.
... Desiccation is a phase between seed maturation and germination and is associated with a major loss of water in preparation of the dormancy period and, later, of the germination stage [1,2]. Based on their desiccation tolerance, seeds are classified as either orthodox (resistant) or recalcitrant (sensitive) [3]. ...
... The accumulation of H2O2 to ranges of desiccation that cause oxidative stress predominantly contributes to the loss of viability of recalcitrant seeds [1,15,16]. In contrast, desiccation-tolerant seeds survive extreme desiccation and further rehydration by applying a set of mechanisms to avoid cellular damage [26,65]. ...
Norway maple and sycamore produce desiccation-tolerant (orthodox) and desiccation-sensitive (recalcitrant) seeds, respectively. Drying affects reduction and oxidation (redox) status in seeds. Oxidation of methionine to methionine sulfoxide (MetO) and reduction via methionine sulfoxide reductases (Msrs) have never been investigated in relation to seed desiccation tolerance. MetO levels and the abundance of Msrs were investigated in relation to levels of reactive oxygen species (ROS) such as hydrogen peroxide, superoxide anion radical and hydroxyl radical (•OH), and the levels of ascorbate and glutathione redox couples in gradually dried seeds. Peptide-bound MetO levels were positively correlated with ROS concentrations in the orthodox seeds. In particular, •OH affected MetO levels as well as the abundance of MsrB2 solely in the embryonic axes of Norway maple seeds. In this species, MsrB2 was present in oxidized and reduced forms, and the latter was favored by reduced glutathione and ascorbic acid. In contrast, sycamore seeds accumulated higher ROS levels. Additionally, MsrB2 was oxidized in sycamore throughout dehydration. In this context, the three elements •OH level, MetO content and MsrB2 abundance, linked together uniquely to Norway maple seeds, might be considered important players of the redox network associated with desiccation tolerance.
... The heat and mass transfer in biological materials subjected to electromagnetic radiation (EMR) has been well documented. Consequently, microwave drying is widely considered one of the best methods for the intensification of these processes [6][7][8]. However, there are divergent opinions on the influence of EMR on biological materials, as it depends on numerous factors, including the moisture content, structure and composition of the material, as well as the frequency and length of the electromagnetic waves used [9][10][11]. ...
... According to studies by Załęski and Aniśko [5] and Aniśko et al. [41], the viability of seeds in drying is reduced not only by high temperatures, but also by intensive tissue dehydration. Furthermore, the seeds of various tree species react differently to drying [8,40]. The minimum admissible moisture content for Scots pine seeds is 3.5%, and the same applies to black alder and common birch; the maximum drying temperature for Scots pine, as well as black alder and common birch seeds, is 45 °C [5]. ...
To improve the process of seed extraction, new solutions have been investigated in an attempt to develop guidelines for the construction of small seed extraction equipment. One of the solutions proposed in this field is the use of electromagnetic radiation in the first stage of hulling cones, reducing their initial moisture content, which will result in quicker scale opening. It is proposed that cones should be irradiated for a relatively short period in the first stage. This operation will allow a quicker loss of moisture from the cones that are still closed, which will result in a more intensive opening of cone scales and will also positively affect the exposure of seeds for the next phase of hulling. The aim of the study was to evaluate the effect of microwave irradiation of pine cones on the quality of the seeds obtained. Cones were exposed to microwaves produced by an 800 W generator. The research was performed in several modes, in which the variable parameters were the duration of microwave irradiation, arrangement of cones with the apex pointed towards either the inner or outer part of the turntable, and the number of cones. The temperature distribution on the surface of and inside the cones was determined using the THERM v2 (Vigo System SA, Ożarów Mazowiecki, Poland) thermal image processing software. We also assessed the energy (vitality) and germinability (quality class) of seeds that were not exposed and those after microwave treatment. The results of the research allowed us to state that, with the assumed parameters of the process, it is possible to obtain second quality class seeds after exposure to microwaves for 5 s. This result was comparable to the quality of seeds obtained without the use of microwaves. When the irradiation time was increased above 5 s, the vitality of seeds decreased and their quality was not satisfactory.
... Outra explicação para redução da viabilidade dos embriões deve-se ao fato de que o processo de secagem pode causar diversos danos às sementes, dentre eles a desnaturação de proteínas e danos às membranas (BLACK; PRITCHARD, 2002). Outrossim, a integridade do sistema de membranas é essencial para a manutenção da viabilidade e caso haja qualquer ruptura indevida, gerada pela perda de água durante o processo de secagem ou durante a fase de embebição após a secagem (KERMODE;FINCH-SAVAGE, 2002), podem ocorrer alterações no metabolismo celular das sementes, processos oxidativos e anomalias devido à perda de estruturas macromoleculares (PAMMENTER; BERJAK, 1999). ...
... Outra explicação para redução da viabilidade dos embriões deve-se ao fato de que o processo de secagem pode causar diversos danos às sementes, dentre eles a desnaturação de proteínas e danos às membranas (BLACK; PRITCHARD, 2002). Outrossim, a integridade do sistema de membranas é essencial para a manutenção da viabilidade e caso haja qualquer ruptura indevida, gerada pela perda de água durante o processo de secagem ou durante a fase de embebição após a secagem (KERMODE;FINCH-SAVAGE, 2002), podem ocorrer alterações no metabolismo celular das sementes, processos oxidativos e anomalias devido à perda de estruturas macromoleculares (PAMMENTER; BERJAK, 1999). ...
A germinação de erva-mate tem sido apontada como baixa, irregular e lenta, com diferentes graus de dormência, tornando a produção de mudas um grande desafio. Estudos destinados a esclarecer os principais mecanismos de dormência presentes em sementes de erva-mate são de grande importância, porém, escassos. Diante disso, objetivou-se avaliar os efeitos da secagem na viabilidade e no desenvolvimento embrionário de sementes da espécie. A avaliação do efeito da secagem foi realizada mediante determinação do teor de água, teste de tetrazólio e desenvolvimento embrionário. Para avaliar a tolerância à dessecação, as sementes foram acondicionadas em uma bandeja plástica sem tampa, colocada em prateleira de câmara fria e seca (CFS), regulada com 25 ± 3% de umidade relativa do ar e temperatura de 10 ± 1°C, por 70 dias. A cada sete dias, as sementes foram retiradas da CFS e submetidas ao teste de tetrazólio e à avaliação do teor de água. O desenvolvimento embrionário foi avaliado a partir dos embriões excisados, oriundos do teste de tetrazólio. O teste de germinação foi conduzido no substrato areia, em caixas gerbox, acondicionadas em câmara de germinação regulada a 25°C e fotoperíodo de 12 horas. Das sementes que não foram submetidas à secagem, apenas 8% germinaram, resultado da imaturidade embrionária das sementes recém-colhidas. A secagem por 70 dias promoveu o desenvolvimento embrionário, mas afetou a viabilidade das sementes, sendo recomendada, portanto, sua secagem por até 49 dias para melhorar a germinação e posterior produção de mudas.
... Desiccation-tolerant (DT) or orthodox seeds, dispersed at low moisture content (MC), can tolerate drying to 3%-7% MC and are amenable to ex situ conservation [1]. DT seeds can withstand desiccation, enabling post-dispersal survival in diverse ecosystems, establishing soil seed banks and synchronizing germination with the growing season through dormancy mechanisms [2]. ...
Ecological significance of dormancy in desiccation-sensitive seeds is poorly understood. Quercus exhibits mutually exclusive occurrence of physiological (PD) and epicotyl dormancy (ePD), with no reported co-occurrence or dormancy class in other genera. We aimed to understand the dormancy in three Castanopsis species and document desiccation sensitivity and germination patterns concerning the embryonic axis position. We hypothesized that Castanopsis acorns are recalcitrant and potentially dormant. Fresh and cold-stratified acorns of Castanopsis chinensis, Castanopsis purpurella, and Castanopsis sclerophylla were subjected to desiccation and germination. Seedling emergence and internal morphology was monitored following cold (CS) and warm (WS) stratification. Fresh acorns had radicles emerge only after CS but require WS for shoot emergence. Drying to 20% moisture content led to complete death. In C. purpurella and C. sclerophylla, the embryonic axis was near the scar, and germination occurred by cracking the pericarp near the scar, which contrasts with C. chinensis. Moderate drying relieved dormancy due to the mechanical resistance of the pericarp. All three acorns were desiccation-sensitive and dormant. This is the first explicit report on PD and ePD co-occurrence in desiccation-sensitive seeds, but literature surveys allow for inference of such coexistence. CS alleviated PD and WS relieved ePD. Winter temperatures break PD, and acorns germinate during spring, but shoot emergence is delayed until summer. Our results are instructive for research on the dormancy of desiccation-sensitive species and the reproduction of Fagaceae species in subtropical forests.
... Recalcitrant seeds, on the other hand, have no pre-desiccation process during maturation and usually have high water content and metabolic levels when they fall off. Throughout development and postharvest storage, recalcitrant seeds of tropical origin are sensitive to desiccation and easily lose viability after desiccation [11]. In general, viability is significantly reduced when water content is less than 10%-15% [10]. ...
The deciduous tree species Sassafras tzumu (Hemsl.) Hemsl., unique to China, holds significant economic and ecological value. However, its seeds exhibit poor storage tolerance and rapid decline in seed vigor. This study primarily investigates the desiccation tolerance of S. tzumu seeds. The results show that S. tzumu seeds have recalcitrant seed characteristics, with a semi-inactivation water content (at which point half of the seeds lose viability) of 20.7%. As desiccation progresses, seed viability decreases significantly; at a reduced water content of 11.93%, only 18.3% of the seeds remain viable, while most lose their viability completely. Relative electrolytic leakage (REC) and H2O2 content gradually increase during this process, while MDA content initially decreases before increasing again, exhibiting distinct trends compared to antioxidant enzyme activities such as superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT). SOD and POD activities exhibit an initial increase followed by a rapid decrease, whereas CAT activity shows a decline followed by a rapid increase. Dehydration to 15% water content in seeds is a key turning point in the process of seed desiccation in S. tzumu, and CAT is an enzyme key to maintaining seed viability. Both the accumulation of toxins and the decline in the activity of the antioxidant system contribute to the susceptibility of S. tzumu seeds to drought stress, a characteristic common to all recalcitrant seeds. To maintain high seed viability above 70% during storage, it is crucial to ensure water content above 23.58%.
... When embryos are used, their maturity stage is a significant factor that affects the success of cryopreservation. Previous studies on orthodox species showed that mature embryo is the best stage for cryopreservation (Kermode and Finch-Savage 2002;Wen and Song 2007;Vineesh et al. 2015). However, the embryo stage for cryopreservation varies depending on the species in recalcitrant plants. ...
Palms (Arecaceae) contribute remarkable economic and environmental values to human life. However, many elite and commercial palm species are becoming critically endangered and demand immediate action to preserve their genetic resources. Cryopreservation has established itself as the definitive in vitro conservation method for recalcitrant-seeded species, such as those within the Arecaceae. Progress in this area has moved steadily forward over the last three decades with the development of various techniques for different explants and palm genotypes and for molecular testing methods to ensure genetic fidelity is maintained in the regenerants. There remains a key challenge to properly identify the components that will enable the long-term conservation of palms using cryopreservation. This review methodically analyzes the state-of-the-art cryopreservation techniques developed for palms and places them within a practical framework. This framework encompasses four underlying components, namely the tissue culture approaches required, the recalcitrant nature of the palm seed, the cryobiology and cryogenic techniques required, and fidelity assessment after cryopreservation. Through a critical analysis of this framework, further optimization of palm cryopreservation protocols and more fundamental studies on the physiological and molecular changes in cryopreserved palm tissues are recommended. The present review helps to showcase a multi-decade global attempt to preserve these mostly recalcitrant species through ex situ collections. From a conservationist’s perspective, this review hopes to stimulate awareness for further concerted efforts in the conservation of rare and endangered plant families. Meanwhile, from a managerial perspective, this work serves to inform decision-makers of the global research effort underway to improve key components of the cryopreservation program for palm species and to encourage funding bodies to appropriately allocate resources to these much-needed research areas.
... Still, germination responses to drought have been poorly studied in Neotropical Melastomataceae. Two studies addressed seed desiccation tolerance-the ability of seeds to remain viable at low water contents (Kermode and Finch-Savage 2002) . José et al. (2007) and Mayrinck et al. (2016) found that Miconia argyrophylla and M. albicans seeds remained viable after reducing the seed moisture content below 5%, indicating that both seeds tolerate desiccation. ...
We synthesize the current knowledge about the germination ecology of Neotropical Melastomataceae by reviewing the processes that take place between seed dispersal and seedling establishment. Seed viability is highly variable, with some species producing high amounts of embryoless and unviable seeds. Melastome seeds can persist in the soil for long periods, potentially because of their minute, light-demanding seeds, which have high chances of being buried. However, studies assessing seed longevity and germination responses to water availability are scarce. Most species produce non-dormant seeds, but physiological and combinational dormancy evolved independently in multiple taxa from seasonal habitats. Germination responses to temperature suggest that species from tropical savannas can germinate under higher temperatures than those from moist forests. Despite these trends, our current knowledge about Neotropical Melastomataceae germination ecology is highly fragmented, is biogeographically biased, and poorly represents the family phylogenetic diversity. We discuss how the seed ecology of melastomes allows us to explain the success of invasive species outside their native range, assess the feasibility of their conservation via ex situ seed banks, and use in seed-based ecosystem restoration. Finally, we outline avenues for future research to tackle current knowledge gaps and enhance our understanding of the germination of this diverse Neotropical family.
... Based on pollen longevity, the plant taxa are classified into three main groups (Harrington, 1970) such as, long-lived pollen (6 months to 1 year), pollen with a medium life span (approximately 1-3 months) and short-lived pollen (few minutes to few days). Depending on water content, pollen having more than 30 per cent C o n t r i b u t o r s P D F water is classified as partially hydrated like recalcitrant seeds and if it is less than 30 per cent as partially dehydrated like orthodox seeds (Kermode and Finch-Savage, 2002). Jain and Shivanna (1989) reported a positive correlation between the loss of viability and a reduction in the amount of membrane phospholipids irrespective of pollen storage conditions. ...
... Sementes dispersas com maiores conteúdos de água podem ser metabolicamente mais ativas, cumprir etapas que antecedem a germinação e, consequentemente, apresentar germinação mais rápida , Jayasuriya et al. 2012, Hamilton et al. 2013. Isto foi observado em nosso estudo para sementes de P. reticulata de savana úmida, que apresentou maior teor de água inicial (tabela 2) e germinação mais rápida que aquelas de ambiente mais seco (figura 2), uma estratégia relacionada a espécies de baixa tolerância ao dessecamento (Kermode & Finch-Savage 2002). ...
RESUMO O tegumento e conteúdo de água das sementes podem interferir na sua tolerância a choques térmicos, assim como o seu ambiente de origem. Para testar essas possibilidades, sementes de Plathymenia reticulata e Stryphnodendron adstringens foram coletadas no norte do Estado de Minas Gerais (representando savana seca) e no nordeste do Estado do Mato Grosso (representando savana úmida) do bioma Cerrado, e suas respostas a choques térmicos de 110, 140 e 170 ºC por 2,5 minutos foram avaliadas sob diferentes condições; intactas, escarificadas, e embebidas após escarificação. Sementes escarificadas e embebidas germinaram mais rapidamente para ambas as espécies. Sementes de savana seca apresentaram menor teor de água inicial e germinação mais lenta para ambas as espécies, porém maior tolerância a choques térmicos que sementes de savana úmida. Sementes de P. reticulata não sobreviveram após tratamento de 140 ºC, mas sementes de S. adstringens de savana seca suportaram tratamento de 170 ºC, independentemente de estarem escarificadas e/ou embebidas. Conclui-se que sementes de P. reticulata são menos tolerantes a choques térmicos que sementes de S. adstringens, que sementes secas são mais tolerantes a choques térmicos que sementes embebidas, e que sementes de savanas secas são mais tolerantes a choques térmicos que sementes de ambientes úmidos.
... Raffinose and stachyose coexist in some seeds as free sugars. In mature soybean seeds, sucrose, stachyose and raffinose constitute approximately 8%, 5% and 2% of the seed dry weight, respectively, and may contribute to the survival of the seed in the dry state [15,16]. Galactomannans are typically restricted to the endosperm of legumes, but they may also occur in many nonleguminous families, such as Compositae and Convolvulaceae [17][18][19][20]. ...
Carbohydrates are the major storage reserves in seeds, and they are produced and accumulated in specific tissues during the growth and development of a plant. The storage products are hydrolyzed into a mobile form, and they are then translocated to the developing tissue following seed germination, thereby ensuring new plant formation and seedling vigor. The utilization of seed reserves is an important characteristic of seed quality. This review focuses on the seed storage reserve composition, source–sink relations and partitioning of the major transported carbohydrate form, i.e., sucrose, into different reserves through sucrolytic processes, biosynthetic pathways, interchanging levels during mobilization and crosstalk based on vital biochemical pathways that interlink the carbon and nitrogen cycles. Seed storage reserves are important due to their nutritional value; therefore, novel approaches to augmenting the targeted storage reserve are also discussed.
... In the end of seed maturation, seeds start to lose water and become dry, this process is named 'desiccation' (Kermode et al., 2002). During desiccation, seeds enter a glass state and maintain only extreme low levels of metabolic activity (Buitink et al., 2008;Burke, 1986;. ...
... ABA plays a role in the regulation of dehydrin and LEA genes in orthodox seeds (Kermode and Finch-Savage 2002). The transcript levels of TaLEA genes in Triticum aestivum subjected to ABA and abiotic stresses were upregulated while the leaf ABA content increased under the stress treatments (Liu et al. 2019). ...
Key message
Loss of viability of recalcitrant seeds upon dehydration is associated with changes in expression levels of genes associated with seed development, the antioxidant defense system and stress responses.
Abstract
Araucaria angustifolia is a Brazilian conifer species that produces desiccation-sensitive seeds. Conservation of recalcitrant seeds by conventional seed banking has severe limitations as the underlying mechanisms of quick viability loss upon drying remain unclear. The aim of this study was to shed light on these underlying mechanisms in A. angustifolia by analyzing the transcript levels of genes related to seed development, antioxidant systems and stress responses in seeds subjected to dehydration. To be able to perform these expression analyses, an additional aim was to identify candidate reference genes suitable for gene expression analyses in A. angustifolia. Using GeNorm software we analyzed 10 selected candidate reference genes for RT-qPCR analysis of gene expression in embryonic axis and cotyledon tissues of dehydrated seeds. The most stable candidate reference genes for normalization of gene expression data in heterogeneous samples (inter-tissues) were ACT, GAPDH and SAR1. Slight drying (35% water content) had a positive effect on seed viability since radicle protrusion values (84%) did not differ significantly from undried seeds (94%). Seed viability, however, decreased dramatically when seeds were dried down to a water content of 28%. Transcript levels of ABI3, LEC1, SMP, APX, MIPS and XERO1 decreased in embryonic axis and cotyledons during dehydration, whereas transcript levels of CAT and NAC increased. Our study provides information on reference genes that are adequate for gene expression studies in A. angustifolia seeds and shows that loss of seed viability during dehydration appears to be associated with a decrease in transcript levels of genes related to desiccation tolerance.
... Excessive dehydration of seeds beyond the critical moisture content may have severely disrupted the integrity of the cellular membrane of seed tissues, resulting in the uncontrollable rate of solutes leaked. In desiccation-sensitive seeds, cellular membranes are known to be unable to reform completely during imbibitions if previously damaged by dehydration below the critical moisture content (Kernode and Finch-Savage, 2002;Berjak et al., 2007). ...
Cola acuminata (Pal. De Beauv.), one of the many forest tree species which are of socio-economic importance in Western and Central Africa, is still exploited in the wild by subsistence farmers because it has not been domesticated yet. As a contribution to its domestication, the present study aimed at determining germination requirements and desiccation tolerance of seeds. Three substrates (forest topsoil, river sand and mixture of forest top soil and river sand), two photoperiods (12 hours/day and continuous darkness) and dehydration were investigated for their effects on seeds germination percentage. To evaluate the seeds’ tolerance to desiccation, fresh seeds were dried at laboratory temperature for 16 days during which seeds moisture content, seeds germination percentage and electrical conductivity of seeds leachate were monitored at two-day intervals. Results showed that the mean germination percentage recorded on the mixture of forest top soil and river sand (97.2 ± 1.0%) was significantly higher than that recorded on forest topsoil (85.5 ± 4.0%), which was in turn higher than that obtained on river sand (70 ± 1.5%). The effect of photoperiod on germination percentage was not significant (p = 0.112). As response to seeds drying, the mean germination percentage slightly decreased as moisture got lost, then drastically dropped when moisture content was below 45.95 ± 4.2%. Seeds failed to germinate when their moisture content fell below 27.1 ± 2.1%. Electrical conductivity of seed leachate exhibited a highly significant negative correlation with both germination percentage (p ˂ 0.01, r = -0.926) and moisture content (p ˂ 0.01, r = -0.931). It is concluded that the best substrate for C. acuminata seeds’ germination is the mixture of forest top soil and river sand in a 1/1 (v/v) ratio. Cola acuminata seeds are desiccation-sensitive and their storage behavior is recalcitrant. This is a significant constraint for conservation that should be addressed in further researches.Keywords: Cola acuminate, seed germination, photoperiod, desiccation tolerance, moisture content, storage behavior.
... Under normal conditions, accumulation of DHNs begin at the onset of seed maturation, especially in the orthodox type of seeds, thereby enhancing the ability of these seeds to withstand desiccation (Delahaie et al. 2013). However, DHNs thus accumulated are quickly disappeared at the time of germination leading to the loss of their ability to withstand dehydration (Kermode and Finch-Savage 2002). Initially, it was presumed that the recalcitrant-type of seeds are intolerant to desiccation because of the absence of DHNs and thus retain high moisture content as compared to the orthodox type of seeds that accumulate DHN proteins. ...
Drought stress-induced crop loss has been considerably increased in recent years because of global warming and changing rainfall pattern. Natural drought-tolerant plants entail the recruitment of a variety of metabolites and low molecular weight proteins to negate the detrimental effects of drought stress. Dehydrin (DHN) proteins are one such class of proteins that accumulate in plants during drought and associated stress conditions. These proteins are highly hydrophilic and perform multifaceted roles in the protection of plant cells during drought stress conditions. Evidence gathered over the years suggests that DHN proteins impart drought stress tolerance by enhancing the water retention capacity, elevating chlorophyll content, maintaining photosynthetic machinery, activating ROS detoxification, and promoting the accumulation of compatible solutes, among others. Overexpression studies have indicated that these proteins can be effectively targeted to mitigate the negative effects of drought stress and for the development of drought stress-tolerant crops to feed the ever-growing population in the near future. In this review, we describe the mechanism of DHNs mediated drought stress tolerance in plants and their interaction with several phytohormones to provide an in-depth understanding of DHNs function.
... Desiccation tolerance (DT) can be defined as the ability of a certain organism to tolerate dehydration and survive extreme water loss without lethal damage [1,2]. A classification of seed DT comprises orthodox, intermediate, and recalcitrant seeds [3,4]. Comparing seeds in different classification is a strategy to study DT; nevertheless, the genetic background is different [5]. ...
Desiccation tolerance (DT) is gradually lost during seed germination, while it can be re-established by pre-treatment with polyethylene glycol (PEG) and/or abscisic acid (ABA). Increasing knowledge is available on several stress-related proteins in DT re-establishment in herb seeds, but limited information exists on novel proteins in wood seeds. This study aimed to investigate the role of metallothionein CkMT4, a protein species with the highest fold increase in abundance in Caragana korshinskii seeds on PEG treatment. The fluctuation in mRNA levels of CkMT4 during seed development was consistent with the changes in DT, and the expression of CkMT4 could be up-regulated by ABA. Besides metal-binding capacity, CkMT4 might supply Cu²⁺/Zn²⁺ to superoxide dismutase (SOD) under high redox potential provided by PEG treatment for excess reactive oxygen species (ROS) scavenging. The overexpression of CkMT4 in yeast results in enhanced oxidation resistance. Experimentally, this study demonstrated the overexpression of CkMT4 in Arabidopsis seeds benefited the re-establishment of DT and enhanced the activity of SOD. On the whole, these findings suggested that CkMT4 facilitated the re-establishment of DT in C. korshinskii seeds mainly through diminishing excess ROS, which put the mechanism underlying the re-establishment of DT in xerophytic wood seeds into a new perspective.
... The wheat experiment demonstrates how NMR sensing can be used to monitor seed filling and dry matter accumulation in the living plant (Figures 6, 7). Many studies presented data on the development of FW, DW and WC during seed filling in wheat (Brenchley and Hall, 1909;Schnyder and Baum, 1992;Altenbach et al., 2003;Yang et al., 2004;Pepler et al., 2006;Xie et al., 2015;Neghliz et al., 2016;Zhang et al., 2017) or on seed filling in general (Kermode and Finch-Savage, 2002), but all used destructive methods. The pattern of development in FW, DW, and WC that we measured (Figure 6) matches well with these studies, but were obtained non-destructively and with a much higher time resolution: 4 min per data point, continuously, vs. ...
Water content (WC) and dry matter content (DMC) are some of the most basic parameters to describe plant growth and yield, but are exceptionally difficult to measure non-invasively. Nuclear Magnetic Resonance (NMR) relaxometry may fill this methodological gap. It allows non-invasive detection of protons in liquids and solids, and on the basis of these measures, can be used to quantify liquid and dry matter contents of seeds and plants. Unfortunately, most existing NMR relaxometers are large, unwieldy and not suitable to measure intact plants or to be used under field conditions. In addition, currently the appropriate NMR relaxometric methods are poorly suited for non-expert use. We here present a novel approach to overcome these drawbacks. We demonstrate that a basic NMR relaxometer with the capability to accept intact plants, in combination with straightforward NMR and data processing methods, can be used as an NMR plant sensor to continuously, quantitatively and non-invasively monitor changes in WC and DMC. This can be done in vivo, in situ, and with high temporal resolution. The method is validated by showing that measured liquid and solid proton densities accurately reflect WC and DMC of reference samples. The NMR plant sensor is demonstrated in an experimental context by monitoring WC of rice leaves under osmotic stress, and by measuring the dynamics of water and dry matter accumulation during seed filling in a developing wheat ear. It is further demonstrated how the method can be used to estimate leaf water potential on the basis of changes in leaf water content.
... The MetO/Msr system was assumed to be involved in the establishment of desiccation tolerance in orthodox Norway maple seeds [64]. Thus, it was necessary to determine whether the MetO/Msr system participates in the regulation of germination, during which Norway maple and sycamore seeds cease to be different in terms of desiccation tolerance [1,65]. Of note, accumulation of MsrB was reported to be related to re-establishment of desiccation tolerance in germinating seeds [66], suggesting that MsrBs might contribute to proper germination. ...
The levels of methionine sulfoxide (MetO) and the abundances of methionine sulfoxide reductases (Msrs) were reported as important for the desiccation tolerance of Acer seeds. To determine whether the MetO/Msrs system is related to reactive oxygen species (ROS) and involved in the regulation of germination in orthodox and recalcitrant seeds, Norway maple and sycamore were investigated. Changes in water content, MetO content, the abundance of MsrB1 and MsrB2 in relation to ROS content and the activity of reductases depending on nicotinamide adenine dinucleotides were monitored. Acer seeds differed in germination speed—substantially higher in sycamore—hydration dynamics, levels of hydrogen peroxide, superoxide anion radicals (O2•−) and hydroxyl radicals (•OH), which exhibited peaks at different stages of germination. The MetO level dynamically changed, particularly in sycamore embryonic axes, where it was positively correlated with the levels of O2•− and the abundance of MsrB1 and negatively with the levels of •OH and the abundance of MsrB2. The MsrB2 abundance increased upon sycamore germination; in contrast, it markedly decreased in Norway maple. We propose that the ROS–MetO–Msr redox system, allowing balanced Met redox homeostasis, participates in the germination process in sycamore, which is characterized by a much higher speed compared to Norway maple.
... Yet, these hypotheses evolved given that desiccation-sensitive and desiccation-tolerant seeds possess the same types, levels, and distribution of important macromolecules. Intracellular glasses also form within cells of sensitive seeds if dried sufficiently (Berjak and Pammenter, 2008;Bewley et al. 2012;Kermode and Finch-Savage 2002;Vertucci and Farrant 1995;Walters 1998;Walters et al. 2005Walters et al. , 2010. If this is the case, then why does seed desiccation sensitivity exist? ...
The attack of pests and diseases represents one of the main limitations for agricultural production in the Neotropical region. The intensification of trade between Latin American countries, the Caribbean, and other regions, among other factors, has resulted in the introduction of a large number of invasive pests in the Neotropical region, affecting crop production and causing large significant losses. Despite efforts to prevent their entry to Latin America and the Caribbean, through the establishment of quarantine systems in the different countries and the implementation of tactics to reinforce phytosanitary surveillance, each year new pests are reported to be introduced in areas where they were not present. This when added to the effects of climate change, represents a challenge for plant protection since it favours the displacement of pests to new areas due to the increase of temperature and changes in the climatic conditions, facilitating the establishment of some introduced species. This chapter presents the use of biological control agents through the implementation of programmes adapted to local conditions as a key strategy for the sustainable management of pests currently present in and potential pests to the region. Initiatives are also presented to strengthen the quarantine system and phytosanitary surveillance in a joint effort with institutions and government agencies of the countries where CABI implements the Plantwise and Action on Invasives programmes, and sustainable production projects with the objective of reinforcing food security in Latin American and the Caribbean countries.
... Yet, these hypotheses evolved given that desiccation-sensitive and desiccation-tolerant seeds possess the same types, levels, and distribution of important macromolecules. Intracellular glasses also form within cells of sensitive seeds if dried sufficiently (Berjak and Pammenter, 2008;Bewley et al. 2012;Kermode and Finch-Savage 2002;Vertucci and Farrant 1995;Walters 1998;Walters et al. 2005Walters et al. , 2010. If this is the case, then why does seed desiccation sensitivity exist? ...
The debate on the adoption and development of GMOs continues today. The polarizations on their use have been established and do not seem to change. This polarization has also been established in Latin America, although two countries permit the cultivation of GMOs (Brazil and Argentina). After 30 years of the first GMO plant, what happened in Latin America? What position have your countries taken on the adoption, adaptation, and development of GM crops? It seems that the struggle for the development of these crops originated on other continents, but their consequences had an impact in Latin America. This debate has meant rising revenues in some countries and the delay of others in the use of this powerful technology. Is it ethical? This debate has left some countries in Latin America and the Caribbean in a technological unit, and others have been able to close the gap between the developer countries and them. GMO technology continues to be surrounded by controversial debates involving different actors. This chapter draws attention to the conflicts generated in polarized contexts and shows how, in situations of a wanted polarization, strategies are used only to defend themselves and maintain control of the situation in both positions. The point of view is from the scientific and technological development.
... La viabilidad de las semillas presentó un decaimiento de hasta 0% en cinco meses de almacenamiento. Según García y Di Stefano (2005), el envejecimiento de las semillas de esta especie es muy rápido debido a que son recalcitrantes, y las semillas de este tipo deben mantener un contenido de humedad relativamente alto para mantener su viabilidad (Leprince et al., 1993;Bewley y Black, 1994;Kainer et al., 1999;Kermode y Finch-Savage, 2002;Magnitskiy y Plaza, 2007). Para Floriano (2004), la sensibilidad a la deshidratación y a tempe- Fig. 3. Germinación acumulada de las semillas de Sideroxylon capiri. ...
... Here is demonstrated that germination was not affected by decreasing seed moisture content in the studied species of Puya; on the contrary, GR increased when seeds were at 5 % of MC. This leads to conclude that seeds have an orthodox behavior and are tolerant to low moisture contents (Kermode andFinch-Savage 2002, Nkang et al. 2003). ...
... Orthodox seeds are characterized by high tolerance to dehydration. The tolerance is attributed to the accumulation of protective sugars, generally oligosaccharides (Buitink et al., 2000), synthesis of late embryogenic abundant (LEA) proteins (Kermode and Finch-Savage, 2002) and the ability to minimize cellular metabolism (Leopold et al., 1994). By contrast, recalcitrant seeds do not undergo desiccation and, without development being interrupted, undergo germination. ...
Hardwood species are valuable biological resources that have an important role in the economy and ecology of ecosystems worldwide. Non-zygotic or somatic embryogenesis (SE) is a powerful tool in plant biotechnology as it is a form of clonal propagation, amenable to cryopreservation of valuable germplasm and genetic transformation including gene editing. The SE process involves five steps and includes somatic embryo induction, proliferation, maturation, plantlet conversion, and subsequent plant acclimatization. This review aims to provide a general overview of these steps in different SE systems developed for hardwood species. Factors that influence the induction stage such as the age of the donor plant, genotype and culture media are discussed. The role of different explant types, i.e. zygotic embryos and non-zygotic tissues, such as roots, flower tissues, nodes, internodes, leaves or shoot apices, in SE induction are especially emphasized. Histological studies of the origin of somatic embryos and the sequence of events leading to their development from initial explants are assessed. Maintenance of embryogenic capacity carried out by subculture of embryogenic inocula on semisolid or liquid media through cell suspension cultures or by temporary immersion systems is described. At present, the main concerns associated with the application of SE for large-scale propagation of elite hardwoods are related to the embryo maturation, germination, and plantlet conversion steps, and these are highlighted in this review. Finally, molecular aspects associated with somatic embryo induction and development are also described. Attempts to overcome the hurdles identified in the embryogenic process, and future lines of research are proposed.
... Several bryophyte species from the Antarctic region are more resistant against UVB irradiation when dry Robinson and Waterman, 2014). The high alpine moss Grimmia alpestris and the lichen Xanthoria elegans, both collected at a mountain range at 2000 m a.s.l., resisted high actinic light conditions better when dried (Heber et al., 2000), and desiccation-tolerant moss species such as Tortula ruralis or Grimmia pulvinata even showed better photosynthetic performance after desiccation to a relative water content of 5% (Proctor, 2001;Kermode and Finch-Savage, 2002), which may prevent the formation of free radicals and damage to essential molecules such as nucleic acids, proteins, or membrane integrated lipids (Proctor et al., 2007;Kranner et al., 2008). Radiolysis of intercellular water is the most significant source of free radicals FIG. 2. Decrease of photosynthetic activity as an indicator for viability of the 54 bryophyte samples in total (YIELD) after the irradiation series experiment in EVT2 (UVR 200-400nm, 1370 W $ m -2 doses of 0, 6 · 10 2 , 6 · 10 3 , 1.5 · 10 5 , 3 · 10 5 , and 6 · 10 5 kJ$m -2 ). ...
As a part of the European Space Agency mission "EXPOSE-R2" on the International Space Station (ISS), the BIOMEX (Biology and Mars Experiment) experiment investigates the habitability of Mars and the limits of life. In preparation for the mission, experimental verification tests and scientific verification tests simulating different combinations of abiotic space- and Mars-like conditions were performed to analyze the resistance of a range of model organisms. The simulated abiotic space- and Mars-stressors were extreme temperatures, vacuum, and Mars-like surface ultraviolet (UV) irradiation in different atmospheres. We present for the first time simulated space exposure data of mosses using plantlets of the bryophyte genus Grimmia, which is adapted to high altitudinal extreme abiotic conditions at the Swiss Alps. Our preflight tests showed that severe UVR 200-400nm irradiation with the maximal dose of 5 and 6.8 × 10 ⁵ kJ·m ⁻² , respectively, was the only stressor with a negative impact on the vitality with a 37% (terrestrial atmosphere) or 36% reduction (space- and Mars-like atmospheres) in photosynthetic activity. With every exposure to UVR 200-400nm 10 ⁵ kJ·m ⁻² , the vitality of the bryophytes dropped by 6%. No effect was found, however, by any other stressor. As the mosses were still vital after doses of ultraviolet radiation (UVR) expected during the EXPOSE-R2 mission on ISS, we show that this earliest extant lineage of land plants is highly resistant to extreme abiotic conditions.
... The development of most seeds can be divided into three stages: tissue differentiation, cell enlargement and mature dehydration. At the stage of tissue differentiation, a single-cell zygote forms a young embryo composed of cotyledons by cell division and differentiation [5,6]. Seed development in higher plants is a very complex process involving many expression-dependent physiological changes and regulation of a large number of genes and phytohormones, and the development of tartary buckwheat seeds is no exception. ...
Background: Tartary buckwheat (Fagopyrum tataricum Gaertn.) is a widely cultivated medicinal and edible crop with excellent economic and nutritional value. The development of tartary buckwheat seeds is a very complex process involving many expression-dependent physiological changes and regulation of a large number of genes and phytohormones. In recent years, the gene regulatory network governing the physiological changes occurring during seed development have received little attention.
... Finch-Savage, 1992;Lin and Chen, 1995;Garcia et al., 1998) (Ingram and Bartels, 1996) and oligosaccharide contents (Farrant et al., 1993) in the seed embryo (Pammenter and Berjak, 1999;Farnsworth, 2000). Such storage behaviour is commonly encountered among species adapted to wet or flooded environments (Farnsworth, 2000) and is hypothesized to promote rapid germination as a result of evolutionary trade-offs (Alpert and Oliver, 2002;Kermode and Finch-Savage, 2002). Rapid seedling establishment may indeed minimize seed predation or infection risk and reflect specialized regeneration strategies linked to limited periods of favourable environmental conditions (Tweddle et al., 2003). ...
Seed introduction is a current practice for the conservation and restoration of plant populations and communities. In many cases, however, seeds of target wild species must be collected from natural populations and then stored in proper conditions until re-introduction. Peatland pool margin specialists rarely recolonize their habitat once a peatland is restored following peat extraction and therefore must be actively reintroduced. However, little is known about the storage conditions promoting seed viability. In this context, we investigated the effects of four storage conditions on the seed viability of eight species collected from natural peatland pool margins of eastern Canada: 1) room temperature, dry conditions, 2) cold temperature, dry conditions, 3) cold temperature, moist conditions, and 4) cold temperature, submerged. Seeds stored for one year were periodically (3, 6, 12 months) tested for viability using 2,3,5-triphenyltetrazolium chloride staining. Seed viability decreased after storage for four of the eight species investigated (Carex echinata, C. magellanica, C. oligosperma, and C. pauciflora) and increased for Rhynchospora alba, but did not vary significantly following storage for C. limosa and Scheuchzeria palustris. Furthermore, the viability of Drosera intermedia and Rhynchospora alba seeds was higher when stored in dry conditions relative to moist or submerged conditions. Proper seed storage conditions are thus highly species-dependent. Direct sowing after collection should be preferred for most of the Carex species, while seeds of Scheuchzeria palustris, Drosera intermedia and Rhynchospora alba could be stored, preferably in dry conditions, without impacting introduction success due to reduced seed viability.
... La respuesta en la germinación ante condiciones de humedad alta de D. granadensis así como la alta cantidad de endospermo, revela tentativamente la recalcitrancia de sus semillas. Según Magnitskiy y Plaza (2007) "al contrario de las semillas ortodoxas, las semillas recalcitrantes se diseminan en una condición húmeda y metabólicamente activa (Leprince et al., 1993, Kainer et al., 1999, perdiendo rápidamente su capacidad de germinación al quedar expuestas a condiciones de baja humedad (Kermode y Finch-Savage, 2002)". Con respecto al tipo de semilla y a las condiciones de almacenamiento, para la familia Winteraceae no dispone aún de información (Royal Botanical Gardens -Kew, 2008). ...
... The development of most seeds can be divided into three stages: tissue differentiation, cell enlargement and mature dehydration. At the stage of tissue differentiation, a single-cell zygote forms a young embryo composed of cotyledons by cell division and differentiation [5,6]. Seed development in higher plants is a very complex process involving many expression-dependent physiological changes and regulation of a large number of genes and phytohormones, and the development of tartary buckwheat seeds is no exception. ...
Background:
Tartary buckwheat (Fagopyrum tataricum Gaertn.) is a widely cultivated medicinal and edible crop with excellent economic and nutritional value. The development of tartary buckwheat seeds is a very complex process involving many expression-dependent physiological changes and regulation of a large number of genes and phytohormones. In recent years, the gene regulatory network governing the physiological changes occurring during seed development have received little attention.
Results:
Here, we characterized the seed development of tartary buckwheat using light and electron microscopy and measured phytohormone and nutrient accumulation by using high performance liquid chromatography (HPLC) and by profiling the expression of key genes using RNA sequencing with the support of the tartary buckwheat genome. We first divided the development of tartary buckwheat seed into five stages that include complex changes in development, morphology, physiology and phytohormone levels. At the same time, the contents of phytohormones (gibberellin, indole-3-acetic acid, abscisic acid, and zeatin) and nutrients (rutin, starch, total proteins and soluble sugars) at five stages were determined, and their accumulation patterns in the development of tartary buckwheat seeds were analyzed. Second, gene expression patterns of tartary buckwheat samples were compared during three seed developmental stages (13, 19, and 25 days postanthesis, DPA), and 9 765 differentially expressed genes (DEGs) were identified. We analyzed the overlapping DEGs in different sample combinations and measured 665 DEGs in the three samples. Furthermore, expression patterns of DEGs related to phytohormones, flavonoids, starch, and storage proteins were analyzed. Third, we noted the correlation between the trait (physiological changes, nutrient changes) and metabolites during seed development, and discussed the key genes that might be involved in the synthesis and degradation of each of them.
Conclusion:
We provided abundant genomic resources for tartary buckwheat and Polygonaceae communities and revealed novel molecular insights into the correlations between the physiological changes and seed development of tartary buckwheat.
... The protective seed membrane that is located between the tegument and that tightly binds to the endosperm in J. curcas, it carry microorganisms that will hamper the seed germination [26]. Nevertheless the tegument is a major barrier to radicle protrusion for many seeds [43], whose physical properties determine its effect on seed germination [14]. Our results showed that germination percentage of J. macrocarpa seeds with intact tegument was very low (4%). ...
To achieve a good production of a crop, it is essential to know the ability of the species to successfully complete two critical stages in the life cycle such as germination and seedling establishment. In this paper we study in comparative form structure of the seed, the importance of tegument in dormancy, the effect of accelerated aging on seed germination and viability, and the early and late growth in J. curcas and J. macrocarpa. External morphology of the seeds allow difference and internally also the embryos show evident differences. J. macrocarpa germination is around 0%-4%. The total removal of tegument showed a 50% increase and the other treatments between 0%-10%. Aging accelerated by Tetrazolium test allowed a comparative analysis of VP and GP. J. curcas maintains both to 96 h, while J. macrocarpa the seed viability is registered along the all treatment. J. macrocarpa seeds have less synchronicity than those of J. curcas. ABA and JAs were detected in tegument of J. macro-carpa and J. curcas seeds. JA could have a roll in inhibition of germination of J. macrocarpa seeds. Early and late growth, FW and DW of root, hypocotyl, epi-cotyl and leaf of J. curcas were significantly different in both species.
... These are seeds for which internal desiccation is a common phase in inducing dormancy (Tweddle et al. 2003). This allows seeds to survive dry periods until favourable conditions arise (Farnsworth 2000;Kermode & Finch-Savage 2002;Fenner & Thompson 2005). However, recalcitrant seeds (also termed non-orthodox and desiccation-sensitive) cannot tolerate large amounts of water loss, which cause deleterious impacts on cell structure, mitotic growth, and other biochemical and biophysical abnormalities. ...
Although regeneration of recalcitrant‐seeded tree species can be affected by prolonged drought, especially in Mediterranean regions, little is known about the response of such species to varying site conditions. A field experiment was performed to determine the effect of irrigation and leaf litter cover on seed germination and early seedling survival of the vulnerable recalcitrant‐seeded tree Beilschmiedia miersii (Lauraceae). Two levels of irrigation (non‐irrigated and irrigated units) and three levels of leaf litter depth (0, 5 and 12 cm) were applied to 72 groups of 30 seeds along a wet ravine of the Coastal Range of Central Chile, equally distributed across sites with different levels of canopy cover. Seed germination was significantly increased by irrigation only under closed‐canopy cover, and by leaf litter cover (>5 cm) under all canopy conditions. The effect of leaf litter on germination increased with canopy openness, while the effect of irrigation did not show any tendency. Meanwhile, early seedling survival was significantly increased by irrigation under intermediate canopy cover, and by leaf litter (>5 cm) under closed‐canopy cover. As a result of its overall positive effect on germination, leaf litter should be maintained within B. miersii communities, particularly under intermediate to closed‐canopy conditions, where it can also increase early seedling survival, and both seed germination and early seedling survival might be increased through additional water inputs. The presence of leaf litter might help retaining such inputs, prolonging their effect on regeneration of B. miersii communities. We see this as a baseline assessment of regeneration and persistence that needs further testing on species with similar traits, given the expected increase in the frequency and length of dry periods into the future.
... Here is demonstrated that germination was not affected by decreasing seed moisture content in the studied species of Puya; on the contrary, GR increased when seeds were at 5 % of MC. This leads to conclude that seeds have an orthodox behavior and are tolerant to low moisture contents (Kermode andFinch-Savage 2002, Nkang et al. 2003). ...
La conservación ex situ de semillas es una de las formas más efectivas de preservación de la biodiversidad y especialmente de la diversidad genética. En el marco del cambio climático su aplicación es una estrategia importante que se debe fortalecer e integrar con la conservación in situ. El objetivo del presente trabajo fue estudiar la tolerancia a la desecación y la germinación de cuatro especies del género Puya y proporcionar herramientas para su conservación ex situ. Estas especies están distribuidas en el páramo, un ecosistema amenazado a pesar de su valor como reservorio y proveedor de agua para la población urbana. En las semillas se realizó la toma de medidas morfológicas y del contenido de humedad (CH), se realizaron ensayos de germinación en tres contenidos de humedad (semillas frescas, 10–12 % y 3–5 %) y se evaluó el porcentaje de germinación y tiempo medio de germinación. Se registró una germinación superior al 80 % en las cuatro especies y no se encontraron diferencias significativas al disminuir el CH. El tiempo medio de germinación no varió entre especies y la viabilidad fue alta comparada con otras especies de páramo. Los resultados indican que son semillas ortodoxas y las variables morfológicas apoyan esta tendencia. Por tanto, este género presenta un gran potencial para ser conservado en bancos de germoplasma lo que contribuye a la conservación de su diversidad, con las cuales se pueden implementar protocolos de germinación para la propagación y reintroducción en programas de restauración.
... During the development of DT seeds, the orchestration of maturation drying by hormone-induced, as well as hormoneindependent transcription factors includes the accumulation of mechanisms that enable desiccation tolerance through a series of subcellular and physiological processes such as, suppression of metabolism, vacuole filling and cell wall relaxation (Pammenter and Berjak 2000;Kermode and Finch-Savage 2002;Bewley et al. 2012;González-Morales et al. 2016). ...
Desiccation sensitive (DS) seeds do not survive dry storage due to their lack of desiccation tolerance. Almost half of the plant species in tropical rainforests produce DS seeds and therefore the desiccation sensitivity of these seeds represents a problem for and long-term biodiversity conservation. This phenomenon raises questions as to how, where and why DS (desiccation sensitive)-seeded species appeared during evolution. These species evolved probably independently from desiccation tolerant (DT) seeded ancestors. They adapted to environments where the conditions are conducive to immediate germination after shedding, e.g. constant and abundant rainy seasons. These very predictable conditions offered a relaxed selection for desiccation tolerance that eventually got lost in DS seeds. These species are highly dependent on their environment to survive and they are seriously threatened by deforestation and climate change. Understanding of the ecology, evolution and molecular mechanisms associated with seed desiccation tolerance can shed light on the resilience of DS-seeded species and guide conservation efforts. In this review, we survey the available literature for ecological and physiological aspects of DS-seeded species and combine it with recent knowledge obtained from DT model species. This enables us to generate hypotheses concerning the evolution of DS-seeded species and their associated genetic alterations.
... During the germination process, mechanisms of germination are activated, whereas the mechanisms related to desiccation tolerance are deactivated (Kermode and Finch-Savage 2002). An example is the mobilization of reserves such as proteins and oligosaccharides, important in the dry state for the maintenance of cell structure (Wang et al. 2003;Donahue et al. 2010), and necessary for the production of energy and other compounds during the germination process. ...
Abstrac: Eremanthus erythropappus (DC.) MacLeish is an important forest species native to the Brazilian savanna biome, an environment with well-defined rainy and dry seasons. Its seeds are desiccation tolerant, non-dormant and dispersed at the end of dry season. This exposes them to the first sporadic rains that can trigger germination but the subsequent dry days can compromise survival of the newly germinated seed. This study evaluates if the damages caused by drying of germinating E. erythropappus seeds, at the stage when they have lost desiccation tolerance, are lethal. The percentage of normal seedlings was evaluated when seeds with different imbibition times were dried to their initial water content and then pre-humidified and rehydrated. Desiccation tolerance was fully lost after 0.5 mm of hypocotyl-radicle protrusion (approximately 72 h) when the radicle had root hairs, a possible indicator of sensitivity to desiccation. Disintegration of cell contents and ultrastructural damage to the seeds subjected to drying were observed by electron scanning microscope. Root hairs disappeared after drying, reappearing after pre-humidification, possibly an attempt to increase the surface area of the radicle for water uptake. However, the hypocotyl-radicle axis became darkened, probably by antioxidant system failure, causing seed death. © 2018 Northeast Forestry University and Springer-Verlag GmbH Germany, part of Springer Nature
Poncirus trifoliata (L.) Raf., es uno de los portainjertos
más importantes para la producción citrícola de la Argentina,
y se propaga por semillas cuya latencia física dificulta su
germinación. La prueba bioquímica de tetrazolio (TZ) permite
una evaluación rápida de la calidad fisiológica de las semillas.
A pesar de que la prueba se ha aplicado a Poncirus, aún no se
han desarrollado protocolos específicos para esta especie. En el
presente trabajo, se llevó a cabo un ensayo preliminar para probar
la concentración de TZ y el tiempo de incubación recomendado
por las asociaciones de analistas de semillas (1% durante 18
y 24 horas), cuyos resultados se utilizaron para establecer
tratamientos adecuados para la especie. Las concentraciones de
sal de TZ evaluadas fueron de 0,2 y 0,5%, con una exposición
de 3 y 5 horas a TZ, en un diseño factorial 2x2x2. Las
semillas se clasificaron como viables o no viables de acuerdo
con las diferentes tinciones obtenidas. Se determinó como la
metodología más adecuada para realizar la prueba de TZ la
utilización de una concentración del 0,2% de la sal TZ, 5 h de
incubación y semillas sin escarificar de modo de optimizar los
recursos implicados.
curcas L. y J. macrocarpa Griseb. son arbustos perennes cuya mayor importancia principalmente es su potencial como biocombustible. Varios autores consideran que el tegumento de las semillas es uno de los factores que inducen la latencia. El objetivo del trabajo fue estudiar el papel del tegumento y el ácido abscísico (ABA) y el ácido jasmónico (JA) en la latencia y germinación de estas especies. J. macrocarpa presenta latencia ya que no germina por métodos tradicionales. En consecuencia, las semillas de J. macrocarpa fueron sometidas a diferentes tratamientos para romper la latencia de las semillas: T1) Control; T2) Escarificación con papel de lija; T3) Eliminación total del tegumento; T4) Inmersión en agua hirviendo; T5) Alternancia de agua caliente y fría; T6) Inmersión en H2SO4 concentrado durante 15 min; T7) Inmersión en H2SO4 concentrado durante 30 min; T8) Estratificación en papel húmedo y frío; T9) Estratificación en arena húmeda y fría. Después de cada tratamiento, las semillas se colocaron en placas de Petri que contenían agua destilada a 30°C de temperatura. Los porcentajes de germinación (GP) se determinaron durante 30 días. Se utilizaron 20 semillas por tratamiento, con tres repeticiones cada una. El ABA y el JA fueron extraídos y purificados de los tegumentos de ambas especies de Jatropha. Estas hormonas se identificaron y cuantificaron a partir de tejido mediante cromatografía líquida de alto rendimiento (HPLC)-espectrometría de masas (MS) de fase inversa. La eliminación total de tegumento mostró un aumento del 50% en el porcentaje de germinación, con los otros tratamientos se logró entre 0-10%. Los JA fueron el compuesto más abundante detectado en el tegumento. El nivel de ABA fue mayor en J. curcas (628%) que en J. macrocarpa, por esta razón suponemos que el nivel de ABA no está directamente relacionado con la germinación y/o dormancia de estas especies de Jatropha. Por el contrario, el nivel de JAs fue mayor en J. macrocarpa (101%) que en J. curcas. En efecto, el JA podría tener un papel en la inhibición de la germinación de semillas de J. macrocarpa.
Poncirus trifoliata (L.) Raf., es uno de los portainjertos más importantes para la producción citrícola de la Argentina, y se propaga por semillas cuya latencia física dificulta su germinación. La prueba bioquímica de tetrazolio (TZ) permite una evaluación rápida de la calidad fisiológica de las semillas. A pesar de que la prueba se ha aplicado a Poncirus, aún no se han desarrollado protocolos específicos para esta especie. En el presente trabajo, se llevó a cabo un ensayo preliminar para pro-bar la concentración de TZ y el tiempo de incubación recomendado por las asociaciones de analistas de semillas (1% durante 18 y 24 horas), cuyos resultados se utilizaron para establecer tratamientos adecuados para la especie. Las concentraciones de sal de TZ evaluadas fueron de 0,2 y 0,5%, con una exposición de 3 y 5 horas a TZ, en un diseño factorial 2x2x2. Las semillas se clasificaron como viables o no viables de acuerdo con las diferentes tinciones obtenidas. Se determinó como la metodología más adecuada para realizar la prueba de TZ la utilización de una concentración del 0,2% de la sal TZ, 5 h de incubación y semillas sin escarificar de modo de optimizar los recursos implicados.
• We investigated how developmental stage affects seed traits, including the relative level of desiccation tolerance of Quercus serrata. We tested the hypothesis that the relative level of desiccation tolerance is a quantitative trait associated with seed development and that a maximum relative level of desiccation tolerance is reached during development.
• Seed growth and physiological traits of Q. serrata from a subtropical forest were examined in detail during the developmental process.
• During seed development, the relative level of desiccation tolerance and other seed traits of Q. serrata varied. Dry matter accumulation in seed components increased rapidly beginning in mid-August, and moisture content declined. At the peak period of seed dispersal in late September, seeds were fully mature, with 100% germination. Relative level of desiccation tolerance increased up to the point of peak dispersal; however, at this time seeds were still recalcitrant. Post-mature development was accompanied by further increases in seed dry matter and decreases in moisture content, which led to a decrease in seed germination and relative level of desiccation tolerance.
• Our results suggest that in species with recalcitrant seeds, the relative level of desiccation tolerance and other seed traits are quantitative at the intraspecific level. The relative level of desiccation tolerance for recalcitrant seeds does not increase infinitely during phase II of development. There is a maximum relative level of desiccation tolerance in recalcitrant seeds within a species.
The model of loss and re-establishment of desiccation tolerance (DT) in germinated seeds has been well developed to explore the mechanisms associated with DT, but little attention has been paid to the tissue variation in this model. Herein, we investigated DT in different embryo axis tissues of germinated pea seeds and its re-establishment by poly(ethylene glycol) (PEG) treatment and then employed an iTRAQ-based proteomic method to explore the underlying mechanisms. DT varied among the four embryo axis parts of germinated seeds: epicotyl > hypocotyl-E (hypocotyl part attached to the epicotyl) > hypocotyl-R (hypocotyl part attached to the radicle) > radicle. Meanwhile, PEG treatment of germinated seeds resulted in a differential extent of DT re-establishment in these tissues. Proteins involved in detoxification and stress response were enriched in desiccation-tolerant hypocotyls-E and epicotyls of germinated seeds, respectively. Upon rehydration, proteome change during dehydration was recovered in the hypocotyls-E but not in the radicles. PEG treatment of germinated seeds led to numerous changes in proteins, in abundance in desiccation-sensitive radicles and hypocotyls-R, of which many accumulated in the hypocotyls-E and epicotyls before the treatment. We hypothesized that accumulation of groups 1 and 5 LEA proteins and proteins related to detoxification, ABA, ethylene, and calcium signaling contributed mainly to the variation of DT in different tissues and its re-establishment.
We live in an unprecedented time of plant biodiversity loss. Current extinction rates are three orders of magnitude faster than extinction rates measured over geologic time. Similarly, 30% of plants are threatened with extinction. This information is startling when one considers that humans depend on plants for life. Fortunately, several systems exist to conserve plant genetic diversity. Seed storage within genebanks represents the most widely utilized system for plant conservation. One advantage of genebanking is that seed viability can be maintained for decades to centuries. Seeds must tolerate extensive post-harvest drying (5–10% moisture content) and cold (−18 °C) to maintain shelf-life for these periods. However, many important tropical seeds cannot tolerate drying to these levels thus precluding genebank storage. But what separates desiccation-tolerant from sensitive seeds? Previous hypotheses related to protective roles for certain sugars and proteins or the formation of intracellular glasses are insufficient. For instance, desiccation-tolerant and desiccation-sensitive seeds accumulate the same types and levels of protective molecules. Likewise, desiccation-sensitive seeds form intracellular glasses if dried sufficiently. Alternatively, using seeds of a tropical palm as a model, our work identifies a critical minimum level of cellular dry matter accumulation for appropriate desiccation tolerance. Our model suggests that cells must acquire >35% dry matter reserves to avoid lethal desiccation stress prior to genebanking. This level of dry matter accumulation may serve as a reference point for future breeding efforts or manipulation of the seed developmental program to enhance desiccation tolerance.
Bromelia reversacantha is an endemic species of some areas of Cerrado rupestre, Brazil, threatened with extinction and that presents ornamental characteristics quite interesting. This species is still poorly studied and the physiological behavior of its seeds during and after drying and storage is practically unknown. Thus, in this study we aimed to analyze the imbibition pattern of seeds stored over a year (first experiment) and the effects of dehydration on seed germination capacity (second experiment) of B. reversacantha. Ripe fruits were collected and after the seeds were extracted, washed and then dried in the shade. In the first experiment, the treatments were distributed in a completely randomized design in a triple factorial scheme (2 x 7 x 11), with two storage conditions (laboratory and cold room); seven storage periods (time zero, two, four, six, eight, ten and twelve months); and eleven periods of imbibition (time zero, 1, 2, 4, 8, 16, 24, 36, 48, 60 and 72 hours from the beginning of imbibition); in eight replicates of 25 seeds per treatment. In the second experiment seeds were used two months after harvest in a completely randomized design, with four treatments (water contents), 12.8%, 11.1%, 8.7% and 6.8%, in four replications of 50 seeds. It is concluded that the seeds of B. reversacantha absorb water in an average period of time of 29.8 hours for the change from phase I to phase II of the imbibition to occur, evidencing no integumentary dormancy. In addition, it was verified that the seeds of B. reversacantha have orthodox behavior, being able to be dewatered at 40 ° C up to 6.8% moisture without prejudice to their germination capacity.
ResearchGate has not been able to resolve any references for this publication.