Content uploaded by Pablo Ferrandis
Author content
All content in this area was uploaded by Pablo Ferrandis on Feb 22, 2017
Content may be subject to copyright.
Influence of heat on seed germination of seven Mediterranean Leguminosae species
Abstract
The influence of high temperatures (dry heat and hot water) on germination of seven Mediterranean Leguminosae species typical of fire-prone ecosystems in southern Spain is analyzed, in order to know the response of seeds to wildfires and the possible implications in their regeneration after this disturbance. Seeds were heated to a range of temperatures (50 –150 C) and exposure times (1–60 min) similar to those registered in the upper soil layers during wildfires. Germination tests were carried out in plastic Petri dishes over 60 days. In general, the degree of seed germination promotion by dry heat treatments showed a wide interspecific variation, although the final germination level was increased in all the studied species except for Scorpiurus muricatus. The thermal pretreatment of 50 C, however, was not effective for germination in any species, and rising the temperature to 70 C only slightly enhanced the germination in Cytisus patens. The preheatings of 90 C (5 and 10 min), 120 C (5 and 10 min), and 150 C (1 min) were the most effective in promoting seed germination. Hot water (100 C) scarification also increased the final germination level in all cases, with the exception of C. patens. The germination rates after preheating were much lower than in mechanically scarified seeds and closely resembled those of the untreated seeds, except for C. reverchonii, whose seed germination rate decreased with heat. The response of species to heat shock had no clear relationship with life trait or with the specific post-fire regeneration strategy (obligate seeder or facultative resprouter). Those species coexisting in the same habitats had different heat optimal requirements for seed germination, an strategy suggested by some authors as minimizing interspecific competition in the secondary succession started after fire.
... The temperatures experienced by soil seed banks during fires determine whether buried seeds survive and germinate after fires, and complex mosaics of spots exposed to a broad range of temperatures have been recorded (Auld and O'Connell 1991;Odion and Davis 2000). In leguminous species, heat breaks the innate seed dormancy by disruption of the seed coat, thereby allowing subsequent imbibition and germination (Gama-Arachchige et al. 2013) and several studies indicate that the high temperatures (50-150°C) generated in the superficial layers of soil promote germination (Tarrega et al. 1992;Herranz et al. 1998). Thus, legumes are considered important components of post-fire successional communities in Mediterranean climate regions (Huerta et al. 2022). ...
... -Another set of seeds was subjected to mechanical scarification by abrasion between two pieces of sandpaper (Tarrega et al. 1992; Kimura and Islam 2012) as a reliable reference to compare the effectiveness of thermal treatment in promoting seed germination (Herranz et al. 1998). -An additional scarification treatment with hot water was tested. ...
... Seeds were immersed in a glass containing 100 mL of hot distilled water (100°C) and then left to cool to room temperature for 4 h, before placing the seeds in Petri dishes. This scarification technique has been used in previous studies to remove hard-seededness in legumes (Cushwa et al. 1968;Herranz et al. 1998). -The set of scarification trials also included a dry heat treatment. ...
Background Many studies have focused on the dormancy-breaking response to heat treatment of freshly matured seeds and immediately after thermal shock. Aims We evaluated whether the full effect of dry heat scarification in freshly matured seeds could be delayed over time and the possible influence of previous storage in the soil. Methods Adenocarpus argyrophyllus was the model species selected to explore our hypotheses by analysing the: (a) influence of scarification treatments; (b) seedling emergence during 5 years after dry heat scarification of freshly matured seeds, and evaluating intrapopulation variation; (c) seedling emergence after dry heat scarification of seeds rescued from soil; and (d) ability to form persistent soil seed banks. Key results Dry heat scarification of freshly matured seeds only resulted in 22.5% germination. However, exposure to pre-sowing thermal shock stimulated seedling emergence during the first few years post-planting, with high intrapopulation variation. In seeds recovered from soil, thermal shock before reseeding increased the seedling emergence rate. Conclusions and implications Our results show that, to avoid incomplete interpretation, studies of thermal treatment on the breaking of physical seed dormancy should allow the seeds sufficient time to exhibit the complete effects of high temperature treatment, thereby preventing underestimation.
... Sprouting and nonsprouting Fabaceae species show different post-fire regeneration strategies, but in the Cerrado open savannas resprouting is the most common strategy (Daibes et al., 2019;Schutte, Vlok & Van Wyk, 1995;Venier, Cabido & Funes, 2016;Satana et al., 2010;Zupo et al., 2021). In spite of this, fire effects on seed germination in Fabaceae are not related to the regeneration form of the species (Herranz, Ferrandis & Martínez-Sánchez, 1998). In addition, optimal heat requirements for seed germination vary among coexisting species, such as minimizing interspecific competition in secondary succession initiated after the fire (Herranz, Ferrandis & Martínez-Sánchez, 1998;Carter, Lesh & Mogush, 2000;Tarrega, Calvo & Trabaud, 1992;Venier, Cabido & Funes, 2016). ...
... In spite of this, fire effects on seed germination in Fabaceae are not related to the regeneration form of the species (Herranz, Ferrandis & Martínez-Sánchez, 1998). In addition, optimal heat requirements for seed germination vary among coexisting species, such as minimizing interspecific competition in secondary succession initiated after the fire (Herranz, Ferrandis & Martínez-Sánchez, 1998;Carter, Lesh & Mogush, 2000;Tarrega, Calvo & Trabaud, 1992;Venier, Cabido & Funes, 2016). ...
... Addressing these challenges requires knowledge of functional seed traits across this region (Tavşanoǧlu & Pausas, 2018). However, while many Mediterranean countries have a long tradition of seed ecological research (e.g., Herranz et al., 1998;Thanos et al., 1991;Thanos et al., 1989), data syntheses of germination traits at large scales are yet to be attempted. Such synthesis is critical to improve wild species use in seed-based conservation and restoration activities (Merritt & Dixon, 2011). ...
Seed germination is a crucial phase of plant responses in early life to current and future environmental conditions. However, germination data are still scarce or disaggregated for many plant lineages and regions, including global biodiversity hotspots such as the Mediterranean Basin. We present MedGermDB, the first germination database for characteristic species of Mediterranean habitats, as defined by the EUNIS classification. We also present a systematic approach to build germination databases using automatic and semi‐automatic data extraction from the literature. MedGermDB contains germination data for 4680 laboratory tests performed with 236 angiosperm species from 43 families, extracted from 125 literature sources (2837 sources screened). Each test is associated to a seed lot (i.e., a seed collection of a plant species obtained from a specific location at a specific time) and its metadata, recording geographical information and experimental conditions (storage, dormancy‐breaking treatments, incubation temperature, and photoperiod). MedGermDB is available as a csv file, and through a web app: https://dianamariacruztejada.shinyapps.io/medgermdb/ . MedGermDB can be used to explore eco‐evolutionary questions and provides a backbone data set for informing effective seed‐based conservation and ecological restoration activities targeting EUNIS habitats. Our methodological approach to data extraction can be extended to other study systems, contributing to global efforts to mobilize germination data.
... Impermeable seed coats can avoid early imbibition and shift seed germination to a more appropriate time for seedling recruitment [9][10][11]. In addition, these types of coats may contribute to protecting embryos from the harmful effects of the high temperatures reached during a fire event [12,13]. Indeed, fire can significantly impact the reproductive capacity of plants by affecting the soil seed bank [14][15][16][17]. ...
Many Astragalus species exhibit seeds with physical dormancy (PY), but little is known about the ecological context of this dormancy. We focused on A. maritimus and A. verrucosus, two threatened Sardinian endemic species inside the subgenus Trimeniaeus Bunge. Fresh seeds collected from the only two respective known populations were used to investigate the effect of mechanical scarification, heat shock, and water imbibition processes on PY release and germination. PY can be overcome through mechanical scarification of the water-impermeable seed coats, while no dormancy break was detected, nor a subsequent increase in seed germination due to fire-induced heat. This suggests that fire does not trigger dormancy release and seed germination in these species. The seeds tolerate relatively high heat shock temperatures (up to 120 and 100 °C for A. verrucosus and A. maritimus, respectively), but after 120 °C for 10 min, the number of dead seeds increases in both species. These facts suggest the capacity to develop a soil seed bank that can persist after fires and delay germination until the occurrence of optimal conditions. As regards water imbibition, both Astragalus species did not show the typical triphasic pattern, as germination started without further water uptake. This study emphasizes the significance of understanding germination processes and dormancy in threatened species. In fire-prone ecosystems, PY dormancy plays a crucial role in soil seed bank persistence, and it may be selectively influenced by post-fire conditions. Understanding such adaptations provides useful insights into conservation strategies.
... As a common feature amongst the Fabaceae family, M. citrina exhibits tegumentary dormancy (Tarrega et al. 1992;Herranz et al. 1998;Silva et al. 2014;Ribeiro et al. 2021) and so, previous trials showed lack of germination if scarification treatment was not applied. To ensure that this did not interfere with the value of the tests, germination tests were carried out at 18 °C with seeds treated with 98% sulphuric acid for 10, 20, 30, 40, and 60 min and then washed several times with distilled water. ...
Medicago citrina and Euphorbia margalidiana are two microinsular species from the Western Mediterranean which are amongst the top 50 most threatened species of the Mediterranean. Conservation plans for both taxa involve translocation and ex situ seedling growth, yet salinity tolerance remains unknown for both species. The main objective of this work was to analyse how germination is modulated by salinity and to evaluate the seed buoyancy of both species to give light to their sea-dispersal capabilities. Salinity tolerance tests were performed using increasing concentrations (100, 200, 300, and 400 mM) solutions of different salts (NaCl, MgCl2, MgSO4, and Na2SO4). Recovery tests were carried out to analyse the potential ionic toxicity of salts. Seed buoyancy was also evaluated in sea and distilled water for each species. M. citrina was the most salt tolerant, germinating at values below 35.6 mS/cm, whilst E. margalidiana only germinated below 21.4 mS/cm. Na2SO4 and MgCl2 are the salts with the strongest inhibitory effect, whilst MgSO4 is the least inhibitory salt. In both species, buoyancy is very limited, being higher in M. citrina (up to 15 days) compared to E. margalidiana (4 days). The higher salinity tolerance and buoyancy allows M. citrina to colonise a broader range of islets than E. margalidiana, which requires moderate altitudes to keep populations away from salt impact. Both species cannot be considered as halophytes and so in situ and ex situ conservation measures should be carried out avoiding high salinity areas to ensure seedling development.
... The germination criterion is defined by the emergence of the cotyledon or the appearance of a radicle measuring at least 2 mm in length. Seeds that do not exhibit these specific characteristics by the end of the designated development period will not be considered when calculating the germination degree (G), calculated according to Equation (1) [58,59]. ...
Environmental pollution with heavy metals has become a problem of major interest due to the harmful effects of metal ions that constantly evolve and generate serious threats to both the environment and human health through the food chain. Recognizing the imperative need for toxicological assessments, this study revolves around elucidating the effects of Pb(II) and Cu(II) ions on three plant species; namely, Medicago sativa L., Triticum aestivum L., and Zea mays L. These particular species were selected due to their suitability for controlled laboratory cultivation, their potential resistance to heavy metal exposure, and their potential contributions to phytoremediation strategies. The comprehensive phytotoxicity assessments conducted covered a spectrum of critical parameters, encompassing germination inhibition, seedling development, and broader considerations regarding ecosystem health. The key metrics under scrutiny included the germination rate, the relative growth of root and stem lengths, the growth inhibition index, and the tolerance index. These accurately designed experiments involved subjecting the seeds of these plants to an array of concentrations of PbCl2 and CuCl2 solutions, enabling an exhaustive evaluation of the phytotoxic potential of these metal ions and their intricate repercussions on these plant species. Overall, this study provides valuable insights into the diverse and dynamic responses of different plant species to Pb(II) and Cu(II) metal ions, shedding light on their adaptability and resilience in metal-contaminated environments. These findings have important implications for understanding plant–metal interactions and devising phytoremediation strategies in contaminated ecosystems.
... Although other plant species are stimulated by exposure to heat (Wiggers et al. 2017;Herranz et al. 1998) and heat in combination with smoke (Singh and Raizada 2010), pine seed germination has generally been shown to be suppressed by heating. Seeds of seven Spanish pine species, Aleppo pine (Pinus halepensis), stone pine (P. ...
Background
Shortleaf pine is a fire-adapted tree species, and prescribed fire is commonly used to increase its regeneration success, improve wildlife habitat, and reach conservation objectives associated with open forest ecosystems. We studied direct effects of heat and smoke on shortleaf pine germination in a greenhouse study and effects of season of burning on the number of new germinants in a field study. Improved understanding of fire effects on shortleaf pine seed and regeneration success can help refine burn prescriptions to better meet specific management objectives.
Results
Temperatures ≥ 120 °C eliminated germination of shortleaf pine seeds in a greenhouse trial, and exposure of seeds to 60 °C resulted in no reduction in germination compared to the unheated control regardless of duration of exposure. At 80 °C, duration of heat exposure mattered, with exposure for 10 min reducing germination compared to unheated controls. Smoke exposure had no effect on germination. A field experiment showed that fall burns (prior to seedfall) resulted in greater initial germinant counts than early spring burns (after seedfall but before germination) or unburned controls, which both resulted in greater initial germinant counts than late spring burns (after germination).
Conclusions
Season of prescribed burning can affect the success of shortleaf pine germination. Late spring burning resulted in high mortality of young germinants. Burning in early spring likely resulted in direct damage to some seeds due to heating but may have also had indirect benefit by exposing mineral soil. Fall burning, before the dispersal of shortleaf pine seed, yielded the highest germinant count and is recommended if improving natural regeneration from seed is the primary objective.
... An increase in soil temperature occurs naturally due to the high radiation of the sun in some areas and other factors, such as fires (naturally occurring or by humans), which usually cause temperatures similar to those investigated in this study (Fidelis et al., 2016). The results obtained in this research about effect of hightemperature on seed germination of clover species are in agreement with previous studies (Jeffery et al., 1988;Herranz et al., 1998;Fidelis et al., 2016). ...
This research was carried out to evaluate the effect of (1) different methods of breaking seed dormancy (physical and chemical scarification, high temperature, hot water and after-ripening), and (2) environmental factors (temperature, salinity and water stress) on seed germination of Trifolium angustifolium , T. arvense , T. fragiferum , T. fucatum , T. repens , T. subterraneum and Trifolium sp. All experiments were conducted in the Seed Research Laboratory of Gorgan University of Agricultural Sciences and Natural Resources, Iran, in 2021. All the examined clover species were dormant after harvest, with little germination. Mechanical scarification with sandpaper or sulphuric acid resulted in more than 88 and 52% germination, respectively. Seeds were able to germinate between 5 and 35°C, but the highest germination (≥ 98% on average) occurred at 20°C. Fluctuating temperature regimes were more efficient in improving the germination than constant temperatures. Seeds of clover species, in addition to having a hard seed coat, have a non-deep physiological dormancy. Fresh seeds showed a high sensitivity to water stress compared with after-ripened seeds. However, relative resistance to salinity stress was observed. The results obtained in this research can be used to develop effective sowing strategies and support the successful establishment of these clover species.
... The effect of heat on seed germination is highly dependent on temperature and different species have different minimum temperature requirements and different thresholds at which heat may become lethal to them. Moreover, studies on germination responses to heat shock [Herranz et al., 1998;Zida et al., 2008] have revealed that not only the amount of heat reaching the seeds, but also the duration of seeds' exposure to a given temperature is important. ...
Diabetes mellitus is one of the most common endocrine diseases characterized by hyperglycemia due to absolute or relative deficiency of insulin. Chromolaena odorata (CO) has been reported to exhibit normoglycemic potential, however, the mechanisms of action of this plant has not been comprehensively investigated. In this study, the methanolic extract of leaves of Chromolaena odorata was investigated for its antioxidant activity; inhibition of carbolytic enzyme activity and potential to improve glucose uptake in yeast cells. The extraction was carried out by maceration in methanol. The phytochemicals were determined by qualitative chemical tests and spectrophotometric methods. Alpha-amylase and Alpha-glucosidase inhibition was determined in vitro by using the dinitrosalicylic acid and ρ-nitrophenyl-α-D-glucopyranose methods respectively. Theantioxidant activity was monitored by radical scavenging and reducing power assays while the glucose uptake was monitored in yeast cell using glucose oxidase method. The phytochemistry analysis revealed the presence of high level of polyphenols (124.67 mg gallic acid eqv/g of CO, 48.5 mg rutin eqv/g of CO and 72.3 mg tannic acid eqv/g of CO, for total phenolics, flavonoids and tannin respectively). The extract exhibited a moderate inhibition of α-amylase (IC50: 1.858 mg/ml) and higher inhibition of α-glucosidase (IC50: 0.653 mg/ml). The extract also showed a moderate capacity to enhance the uptake of glucose by yeast cells, scavenge DPPH and hydroxyl radicals and high reducing power. In conclusion, the study showed that methanolic extract of Chromolaena odorata leaves has the potential to ameliorate hyperglycemic condition and this may be due to a combination of multiple mechanisms of amelioration of oxidative stress, improved uptake of glucose and reduction of postprandial sugar. Further work should be carried out to further characterize this extract.
In August 2021, very intense fires swept through various forested areas in northern Algeria, particularly in Kabylia. The population dynamics of Cistus salviifolius and Cistus monspeliensis were studied along a post-fire successional gradient during the first nine months (September 2021 – May 2022), in two forest communities: the Cork oak ( Quercus suber ) and the Aleppo pine ( Pinus halepensis ) forests in the coastal zone of Bejaia province. The Cistus spp. germinations were counted monthly in each forest on 10 plots of 1 m ² , evenly distributed along 2 transects of 45 m each. The results showed that the majority of germinations occur in December with 207.5 ± 24.2 seedlings in the Cork oak forest and 171.3 ± 18.0 seedlings in the Aleppo pine forest. Student's t-test does not reveal significant differences for December between the two communities. During the first months following the fire (September and October 2021), germinations were almost absent. The monthly rainfall in September 2021 was estimated at 16.25 mm, an insufficient amount for effective germination. Late germination results in an extension of its period, showed a high rate in January 2022 with 42.2 ± 2.1 and 11.5 ± 0.8 seedlings, respectively, in the Cork oak forest and the pine forest. Beyond January, germination was practically nonexistent in both communities. Therefore, the majority of the seed germination was concentrated in November, December, and January with a unimodal germination pattern.
Cistus albidus L., C. monspeliensis L., and C. salvifolius L. are characteristic obligate seeder shrubs of the southern French garrigue. The three species, which occur at the same sites require heat scarification for their germination. It was hypothesized that heat requirements for germination would be specific for each of these shrubs in order to minimize intraspecific seedling competition. Results of in vitro germination experiments with seedpretreatment over a temperature range from 50 to 150°C and a range of exposure times from 1 to 15 min supported this hypothesis. Cistus monspeliensis L. had the highest temperature requirements for heat scarification.
Although Cistus salvifolius and C. villosus are obligatory seeders, differences in production, migration, dispersal pattern and viability of seeds indicate that they possess distinct dispersion strategies: C. salvifolius disperse in time and C. villosus both in time and space. -from Authors