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Premise of study:
The mechanisms by which plants tolerate water deficit are only just becoming clear. One key factor in drought tolerance is the ability to maintain the capacity to conduct water through the leaves in conditions of water stress. Recent work has shown that a simple feature of the leaf xylem cells, the cube of the thickness of cell w...
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... correction ( Table 4 ). Warm season precipitation (represented by PWmQ; Table 4 ) was also strongly associated with ( t / b ) 3 , but dry season precipi- tation showed no relationship. There was no signifi cant rela- tionship between MAP and lumen diameter (uncorrected r = −0.03; P > 0.05; phylogenetically corrected r = 0.16; P > 0.05; Fig. 5A ). However, lumen diameter was very strongly corre- lated with wall thickness ( r > 0.88; Table 4 ), implying strong coordination of these traits. Xylem wall thickness showed a weak negative correlation with MAP ( r = −0.27), although this became insignifi cant when phylogenetically adjusted. Although ( t / b ) 3 was signifi cantly ...
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... of the pairs showed positive slopes for the relationship between b and MAP ( P < 0.001; Fig. 5B ...
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... weakness of the association between MAP and either lumen diameter ( b ) or wall thickness ( t ) at the higher phylogenetic level ( Fig. 5A ), combined with strong correlations between t , b and ( t / b ) 3 , implies that the relationship between ( t / b ) 3 and pre- cipitation involves precise adjustment of both lumen diameter and wall thickness. At the within-genus level, that is, over rela- tively short periods of evolutionary time, this is mainly attained by adjusting lumen diameter ( Fig. 5B ). ...
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... weakness of the association between MAP and either lumen diameter ( b ) or wall thickness ( t ) at the higher phylogenetic level ( Fig. 5A ), combined with strong correlations between t , b and ( t / b ) 3 , implies that the relationship between ( t / b ) 3 and pre- cipitation involves precise adjustment of both lumen diameter and wall thickness. At the within-genus level, that is, over rela- tively short periods of evolutionary time, this is mainly attained by adjusting lumen diameter ( Fig. 5B ). However, both lumen diameter and wall thickness show strong phylogenetic correla- tions with ( t / b ) 3 ( Table 4 ). ...
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Grevillea robusta (Proteaceae) is an economically important plant species. In Sri Lanka, G. robusta is a popular high shade tree in tea plantations and is widely grown in high and mid-elevations (> 600 m mean sea level). Incidences of canker and associated die-back of G. robusta are increasing on tea lands of Sri Lanka. The symptoms started from ye...
Citations
... The thickness of the double-wall (t) divided by the width of the lumen (b) is widely applied to reflect the mechanical resistance against tracheid implosion due to increased negative pressure during drought (Hacke et al., 2001;Jansen et al., 2009), relating to woody density (Lachenbruch and McCulloh, 2014) and hydraulic vulnerability (Blackman et al., 2010;Jordan et al., 2013). Interestingly, in L. sibirica, no significant (all p > 0.05) relations were found between E(t/b) 2 , L (t/b) 2 , Leaf(t/b) 2 and RGR branch (Fig. 7a, 7b and 7c), suggesting that hydraulic vulnerability is not coupled with performance in field, consistent with some studies (Martínez-Vilalta et al., 2009), probably due to the pit-margo structural regulation (Domec and Gartner, 2003;Isasa et al., 2023) in sapwood, and the reversible tracheid's collapse when drought occurred in pine needles (Cochard et al., 2004;Wolfe et al., 2023;Zhang et al., 2023). ...
Despite inter-specific differences in hydraulic traits at broad scale have been comprehensively studied, intra- specific hydraulic variability in situ is less well known. Which hydraulic traits can better predict whole-plant performance in field both within and across species remains largely ambiguous. In the study, we conducted a field investigation on branch radial growth, leaf and branch anatomical traits related to hydraulics, as well as leaf pressure–volume curve parameters of two dominant conifer species (Larix sibirica and Picea obovata) at four sites over an aridity gradient across the Altay Mountain range, which locates at the southern edge of Taiga ecosystem, one of the largest and the most sensitive terrestrial biomes to climate change. L. sibirica is a generalist deciduous conifer species, while P. obovata is a specialist evergreen conifer species. It was found that: 1) P. obovata showed ten times higher slope of branch radial growth (RGRbranch) fitted to aridity than L. sibirica; 2) the hydraulic distance from the bundle sheath to the stomata (DMC) can predict the growth rate both within and across species; 3) earlywood and latewood anatomies showed different relations to RGRbranch within and across species; 4) leaf saturated osmotic potential (Ψsat) but not turgor loss osmotic potential (Ψtlp) was significantly and positively related to RGRbranch within species. Our results support the hypothesis that specialists are more sensitive in growth to climate change than generalists. Further, the results highlight DMC as a pivotal role in water transport and associated carbon assimilation both within and across species in Taiga ecosystem, therefore at the core of the structural adjustments to climate change in this largest and the most sensitive terrestrial biome.
... To generate a broad, phylogenetically diverse dataset of angiosperm leaf anatomical traits, we compiled data from Bongers and Popma (1990), Beaulieu et al. (2008), Coomes et al. (2008), Boyce et al. (2009, 2011, , Sack et al. (2012), , Jordan et al. (2013), Blonder and Enquist (2014), Fridley and Craddock (2015), Carins Murphy et al. (2016), Gleason et al. (2016) and McElwain et al. (2016). Taxonomic names were corrected by querying The Plant List using the R package 'Taxonstand' (Cayuela et al., 2012). ...
Background and Aims
While genome size limits the minimum sizes and maximum numbers of cells that can be packed into a given leaf volume, mature cell sizes can be substantially larger than their meristematic precursors and vary in response to abiotic conditions. Mangroves are iconic examples of how abiotic conditions can influence the evolution of plant phenotypes.
Methods
Here, we examined the coordination between genome size, leaf cell sizes, and cell packing densities, and leaf size in 13 mangrove species across four sites in China. Four of these species occurred at more than one site, allowing us to test the effect of climate on leaf anatomy.
Results
We found that genome sizes of mangroves were very small compared to other angiosperms, and, like other angiosperms, mangrove cells were always larger than the minimum size defined by genome size. Increasing mean annual temperature of a growth site led to higher packing densities of veins (Dv) and stomata (Ds) and smaller epidermal cells but had no effect on stomatal size. Contrary to other angiosperms, mangroves exhibited (1) a negative relationship between guard cell size and genome size; (2) epidermal cells that were smaller than stomata, and (3) coordination between Dv and Ds that was not mediated by epidermal cell size. Furthermore, mangrove epidermal cell sizes and packing densities covaried with leaf size.
Conclusions
While mangroves exhibited coordination between veins and stomata and attained a maximum theoretical stomatal conductance similar to other angiosperms, the tissue-level tradeoffs underlying these similar relationships across species and environments was markedly different, perhaps indicative of the unique structural and physiological adaptations of mangroves to their stressful environments.
... However, functional trait (co)variation and trait-climate associations may change with scale [32,38]. Most theoretical and empirical studies involving the leaf economic and hydraulic traits have focused on higher-level community or species level associations (e.g., [29,31,39]). In trees, attention is increasingly shifting to associations at the intra-specific level [40][41][42], particularly the genetic-based differences and associations between populations [35,43] that provide insights into micro-evolutionary responses to climate variation [44]. ...
... This is consistent with more general expectations that environmental factors that increase transpiration of plants or decrease water availability increase the leaf venation density [47]; although a previous study of wild eucalypt populations found vein densities increased with increasing home-site aridity rather than temperature as in our study [102]. No trends were detectable in E. pauciflora, more consistent with the absence of a vein density-climate association reported among species of the Australian Proteaceae [39]. ...
With climate change impacting trees worldwide, enhancing adaptation capacity has become an important goal of provenance translocation strategies for forestry, ecological renovation, and biodiversity conservation. Given that not every species can be studied in detail, it is important to understand the extent to which climate adaptation patterns can be generalised across species, in terms of the selective agents and traits involved. We here compare patterns of genetic-based population (co)variation in leaf economic and hydraulic traits, climate–trait associations, and genomic differentiation of two widespread tree species (Eucalyptus pauciflora and E. ovata). We studied 2-year-old trees growing in a common-garden trial established with progeny from populations of both species, pair-sampled from 22 localities across their overlapping native distribution in Tasmania, Australia. Despite originating from the same climatic gradients, the species differed in their levels of population variance and trait covariance, patterns of population variation within each species were uncorrelated, and the species had different climate–trait associations. Further, the pattern of genomic differentiation among populations was uncorrelated between species, and population differentiation in leaf traits was mostly uncorrelated with genomic differentiation. We discuss hypotheses to explain this decoupling of patterns and propose that the choice of seed provenances for climate-based plantings needs to account for multiple dimensions of climate change unless species-specific information is available.
... In these studies, the authors analysed single or a few species, but here we show that the same trend occurred when a larger group of species is considered. It is known that longer petioles can only maintain larger leaves with wider vessels (Coomes et al., 2008;Levionnois et al., 2020) as the reduction of vessel diameter would represent a diminished efficiency of water transport to the leaves (Sack et al., 2003;Brodribb, 2009;Jordan et al., 2013;Scoffoni et al., 2016;Levionnois et al., 2020). This is in line with previous observations of vessels widening within the leaf, from the very narrow vessels at the end of the sap path close to the stomata towards the wider vessels at the base of the leaf (Rosell et al., 2017(Rosell et al., , 2019. ...
Background and Aims
Petioles are important plant organs connecting stems with leaf blades and affecting light-harvesting ability of the leaf as well as transport of water, nutrients and biochemical signals. Despite the high diversity in petiole size, shape and anatomy, little information is available about their structural adaptations across evolutionary lineages and environmental conditions. To fill our knowledge gap, we investigated the variation of petiole morphology and anatomy of mainly European woody species to better understand drivers of internal and external constraints in an evolutionary context.
Methods
We studied how petiole anatomical features differed according to whole-plant size, leaf traits, thermal and hydrological conditions, and taxonomical origin in 95 shrubs and trees using phylogenetic distance-based generalized least squares models.
Key Results
Two major axes of variation were related to leaf area and plant size. Larger and softer leaves are found in taller trees of more productive habitats. Their petioles are longer, with a circular outline and anatomically characterized by the predominance of sclerenchyma, larger vessels, interfascicular areas with fibers and indistinct phloem rays. In contrast, smaller and tougher leaves are found in shorter trees and shrubs of colder or drier habitats. Their petioles have terete outline, phloem composed of small cells and radially arranged vessels, fiberless xylem and lamellar collenchyma. Individual anatomical traits were linked to different internal and external drivers. The petiole length and vessel diameter increase with enlarging leaf blade area. Collenchyma becomes absent with increasing temperature, and petiole outline becomes polygonal with increasing precipitation.
Conclusions
We conclude that species temperature and precipitation optima, plant height, leaf area and thickness exerted a significant control on petiole anatomical and morphological structures not confounded by phylogenetic inertia. Species with different evolutionary histories but similar thermal and hydrological requirements have converged to similar petiole anatomical structures.
... Based on the fact that many of these structures are associated with the leaf surface exposed to direct light, Jordan et al. (1998) [85] proposed that they protect the mesophyll from excess solar radiation, including the photosynthetically active, UV, and possibly the infrared spectral band as well. These structural elements increase the path through which photons must travel and thus increase the attenuation of UV and PAR before reaching the mesophyll [85][86][87] (Figure 1e). ...
Leaves have evolved to effectively harvest light, and, in parallel, to balance photosynthetic CO2 assimilation with water losses. At times, leaves must operate under light limiting conditions while at other instances (temporally distant or even within seconds), the same leaves must modulate light capture to avoid photoinhibition and achieve a uniform internal light gradient. The light-harvesting capacity and the photosynthetic performance of a given leaf are both determined by the organization and the properties of its structural elements, with some of these having evolved as adaptations to stressful environments. In this respect, the present review focuses on the optical roles of particular leaf structural elements (the light capture module) while integrating their involvement in other important functional modules. Superficial leaf tissues (epidermis including cuticle) and structures (epidermal appendages such as trichomes) play a crucial role against light interception. The epidermis, together with the cuticle, behaves as a reflector, as a selective UV filter and, in some cases, each epidermal cell acts as a lens focusing light to the interior. Non glandular trichomes reflect a considerable part of the solar radiation and absorb mainly in the UV spectral band. Mesophyll photosynthetic tissues and biominerals are involved in the efficient propagation of light within the mesophyll. Bundle sheath extensions and sclereids transfer light to internal layers of the mesophyll, particularly important in thick and compact leaves or in leaves with a flutter habit. All of the aforementioned structural elements have been typically optimized during evolution for multiple functions, thus offering adaptive advantages in challenging environments. Hence, each particular leaf design incorporates suitable optical traits advantageously and cost-effectively with the other fundamental functions of the leaf.
... The question whether sclerophylly first developed in response to low nutrient sites or rather to drought has figured large in discussion of Australian vegetation history, with interpretation of leaf features in Proteaceae often central (e.g. Hill 1998Hill , 2004Jordan et al. 2013Jordan et al. , 2014Carpenter et al. 2014;Onstein et al. 2016). Cornwell et al's (2014) mapping of ecological strategy traits onto phylogeny across more than 48,000 species identified Proteaceae as the most distinctive lineage for low leaf nutrient concentration within the whole of seed plants. ...
Scope
Proteaceae are an ecologically distinctive family, with largest radiations in the sclerophyll vegetation types of Australia and South Africa. This brief paper comments on Hayes et al. (2021), who have mapped leaf phosphorus concentration on to the phylogenetic tree for the family.
Conclusions
Considered across all seed plants worldwide, Proteaceae contribute most of the lowest leaf nitrogen (N) and phosphorus (P) concentrations known. Hayes et al. concluded that they have used low-phosphorus strategy from their origins ca. 100 My ago. Occasional excursions into higher leaf P have been relatively recent and have not produced many species. The family as a whole is an instance of phylogenetic niche conservatism. The conservatism arises not from trait inertia but from the intensity of competition in continental vegetation, giving Proteaceae competitive advantage within distinct niches and inhibiting them from radiating into other ways of life. When a distinct niche is concentrated into a single clade in this way, quantitative methods that test for replicate patterns across multiple clades will not detect strong signal. However, niche-conservative clades make important and distinctive contributions to the world’s ecology.
... Individuals that produced larger xylem vessels (X A ) had decreased bulliform area (B A ) (Fig. 4A), enabling a larger potential for water and mineral transport while decreasing the potential for water storage (Carmo-Silva et al., 2009;Gibson, 2009). However, variation (CV) in interveinal distance (IVD) across sites was strongly associated with variation in resistance (t/b) (Fig. 4B), equating to greater flexibility in the amount of transport vessels (IVD) and the capability of those vessels to withstand decreased water availability (t/b) (Jordan et al., 2013). These strategies may allow populations of A. gerardii to respond to climate fluctuations (temperature and rainfall) within a growing season. ...
Background and aims:
Andropogon gerardii is a highly productive C4 grass species with a large geographic range throughout the North American Great Plains, a biome characterized by a variable temperate climate. Plant traits are often invoked to explain growth rates and competitive abilities within broad climate gradients. For example, plant competition models typically predict that species with large geographic ranges benefit from variation in traits underlying high growth potential. Here, we examined the relationship between climate variability and leaf-level traits in A. gerardii, emphasizing how leaf-level microanatomical traits serve as a mechanism that may underlie variation in commonly measured traits, such as SLA.
Methods:
A. gerardii leaves were collected in August of 2017 from Cedar Creek Ecosystem Science Reserve (MN), Konza Prairie Biological Station (KS), Platte River Prairie (NE), and Rocky Mountain Research Station (SD). Leaves from ten individuals from each site were trimmed, stained, and prepped for fluorescent confocal microscopy to analyze internal leaf anatomy. Leaf microanatomical data was compared with historical and growing season climate data which was extracted from PRISM spatial climate models.
Key results:
Microanatomical traits displayed large variation within and across sites. According to AICc selection scores, the interaction of mean precipitation and temperature for the 2017 growing season was the best predictor of variability for the anatomical and morphological traits measured here. Mesophyll area and bundle sheath thickness were directly correlated with mean temperature (annual and growing season). Tissues related to water-use strategies, such as bulliform cell and xylem area, were significantly correlated with one another.
Conclusions:
The results indicate (1) microanatomical trait variation exists within this broadly distributed grass species (2) microanatomical trait variability appears likely to impact leaf-level carbon and water use strategies, and (3) microanatomical trait values vary across climate gradients, and may underlie variation in traits measured at larger ecological scales.
... There has been sporadic examination of the anatomy of the photosynthetic organs of Australian plants from various environments and for various purposes. Jordan and colleagues (Jordan et al. 2005(Jordan et al. , 2008(Jordan et al. , 2013) examined a range of species with some emphasis on the Proteaceae and some species from dry habitats but many were from very mesic environments as well. Studies of plants from mostly arid environments include those of Wood (1934) who looked at stomatal distribution on leaves of what he called xerophytes. ...
... Carbon dioxide diffusion into the leaf is favoured over water loss if the boundary layer dominates the diffusion limitation (Evans and Loreto 2000) so crypts and furrows that effectively increase the boundary later will improve the plant's water relations under arid conditions. From an ecological perspective it was found that deep encryption of stomata was associated with xeric environments (Jordan et al. 2013). The assimilation rate of CO 2 is closely related to the leaf hydraulic conductance and a short path length from the vascular transport system to the stomata is beneficial for this (Brodribb et al. 2007). ...
... Paradoxically the ability of plants to survive under conditions of water shortage is related to their ability to transport water through their leaves when they are water stressed (Jordan et al. 2013). In xerophytic plants close proximity between the xylem and stomata can enable them to photosynthesise at higher rates under water stress than mesophytic plants (Orians and Solbrig 1977). ...
Plants from arid environments have some of the most diverse morphological and anatomical modifications of any terrestrial plants. Most perennials are classified as xerophytes, and have structures that limit water loss during dry weather, provide structural support to help prevent cell collapse during dry periods or store water in photosynthetic tissues. Some of these traits are also found in sclerophyllous plants and traits that may have developed due to evolution of taxa on nutrient poor soils may also benefit the plants under arid conditions. We examined the morpho-anatomical features of photosynthetic organs of three tree and four shrub species with reduced leaves or photosynthetic stems that occur in arid or semiarid sites in Australia to see if there were patterns of tissue formation particularly associated with xeromorphy. In addition, we reviewed information on succulent and resurrection species. In the tree species (Callitris spp.) with decurrent leaves clothing the stems, the close association between the water transport system and stomata, along with anisotropic physiology would allow the species to fix carbon under increasingly dry conditions in contrast to more broad-leaved species. The shrub species (Tetratheca species and Glischrocaryon flavescens) with photosynthetic stems had extensive sclerenchyma and very dense chlorenchyma. The lack of major anatomical differences between leafless species of Tetratheca from arid areas compared with more mesic sites indicates that quite extreme morphological modifications may not exclude species from growing successfully in competition with species from less arid areas. The sclerophyll flora now characteristic of Australian vegetation from seasonally arid climates may have evolved during mesic times in the past but with relatively minor modifications was able to adjust to the gradually drying climate of much of Australia up to the present time.
... One way to expand our understanding of plant response to climate within other groups is to investigate leaves at the anatomical (cellular) level, including stomata, mesophyll cell layers, and xylem. Leaf anatomy has been shown to reflect abiotic stressors in the plant's environment and general climate, yet the precise nature of leaf anatomical response to abiotic factors remains poorly understood (Ashton and Berlyn 1994;McElwain and Chaloner 1995;Royer 2001;Oldham et al. 2010;Schubert et al. 2012;Jordan et al. 2013). Similar to leaf physiognomy, anatomical variation with climate is either known from within certain plant groups or documented for various plant groups along climate gradients by sampling across species' entire geographic range (Ashton and Berlyn 1994;Jordan et al. 2013;Ranjbar and Hajmoradi 2016). ...
... Leaf anatomy has been shown to reflect abiotic stressors in the plant's environment and general climate, yet the precise nature of leaf anatomical response to abiotic factors remains poorly understood (Ashton and Berlyn 1994;McElwain and Chaloner 1995;Royer 2001;Oldham et al. 2010;Schubert et al. 2012;Jordan et al. 2013). Similar to leaf physiognomy, anatomical variation with climate is either known from within certain plant groups or documented for various plant groups along climate gradients by sampling across species' entire geographic range (Ashton and Berlyn 1994;Jordan et al. 2013;Ranjbar and Hajmoradi 2016). For example, the anatomy of sun and shade leaves of different Quercus species was variable, demonstrating variability in structure responses (thickness of leaf, epidermis cell, palisade cell, and cuticle; stomatal density and index; and stomatal length measurements), and anatomy in some species (e.g., Quercus velutina) was highly responsive, while in others (e.g., Quercus rubra), it was less responsive to abiotic factors (Ashton and Berlyn 1994). ...
... Comparable scalelike leaves in P. orientalis retained the conventional cellular layer, with development of palisade cells toward the adaxial and spongy mesophyll cells toward the abaxial leaf (Dörken 2013). Across different species within Proteaceae, xylem cell size increased with mean annual precipitation at both a regional scale and a global scale (Jordan et al. 2013). ...
... For instance, Proteaceae species from rain forest have leaves that are very different from closely related taxa from arid environments (e.g. Jordan et al. 2013). Fossil evidence clearly indicates that over geological time climate change has had a very strong influence on current taxon distribution (e.g. ...
Key message
The phylogenetically basal genus of the Casuarinaceae, Gymnostoma, from relatively mesic environments, shows morphological and anatomical structures that are precursors to xeromorphic modifications in the derived genera Casuarina and Allocasuarina.
Abstract
Gymnostoma is the basal genus of the Casuarinaceae with a long evolutionary history and a morphology that has changed little over many millions of years. From a wide distribution in the Tertiary of the southern hemisphere, it is now restricted to islands in the Pacific Ocean, the Malesian region and one small area of northeastern Queensland where it occurs in mesic climates, often on poor soils. The unique vegetative morphology it shares with other more derived genera in the family appears to be xeromorphic. Its distribution combined with the fossil evidence that early Tertiary Gymnostoma occurred with other taxa whose morphology indicated they grew in mesic environments implies that the reduction in the photosynthetic organs was not specifically related to growing in xeric environments. It may be related to evolutionary adaptation to growing on nutrient poor substrates that may also suffer from seasonal water deficit. The foliage reduction then served as a pre-adaptation for derived species to help them cope with the aridity that developed on the Australian continent through the later part of the Tertiary. The fusion of the leaves to the stem to form phyllichnia was a precursor which enabled the development of specific adaptations in the derived genera Casuarina and Allocasuarina to improve water conservation, such as stomata restricted to furrows between the phyllichnia and proliferation of structural sclerenchyma that helps prevent cell collapse under drought conditions.
