Spatial variations in stomatal traits and their coordination with leaf traits in Quercus variabilis across Eastern Asia

Relationships between leaf morphologies and stomatal traits of Achnatherum splendens under different soil moistures in semiarid Northern China

The interplay between leaf and stomata is fundamental for the exchange of carbon and water between plants and the atmosphere. This relationship is pivotal for comprehending the connections between the physical structure and physiological metabolism of plant leaves under various conditions. A study examining the relationship between leaf morphological traits and stomatal traits of the Achnatherum splendens under varying natural soil moisture conditions was conducted along the southern shore of Hulun Lake in Inner Mongolia. In our study, stomatal density (SD) and stomatal relative area (SRA) significantly decreased, while stomatal width (SW), leaf length (LL), leaf area (LA) and leaf dry weight (LDW) increased correspondingly with rising soil moisture. A significant positive correlation between the stomatal traits and leaf morphological traits was observed through principal component analysis (PCA) and permutation test, indicating that the functional traits of leaf morphologies and stomata of A. splendens exhibit a positive relationship. The results reveal the resource utilization strategies of A. splendens in response to varying soil water conditions, offering a scientific data foundation and theoretical support for the management of A. splendens grassland, ecological restoration, and the strategic planning of animal husbandry in Inner Mongolia.

Reprogramming of Metabolome and Transcriptome Shaped the Elevational Adaptation of Quercus variabilis by Regulating Leaf Functional Traits

Exploring how plants adapt to environmental changes is key to plant survive and protection under accelerating climate change. Quercus variabilis is widely distributed in China with high economic and ecological value, yet its elevational adaptation mechanism remains unclear. Here, we investigated the leaf functional traits, metabolome and transcriptome of Q. variabilis along an elevational gradient (800-1400 m) in Mt. Li, China. Results showed that leaves at higher elevations became smaller, narrower, thicker, with smaller and denser stomata, and maintained higher levels of nitrogen, soluble sugar, total phenol, lignin and soluble sugar-to-starch ratio. With increasing elevation, Q. variabilis underwent a metabolic shift from being dominated by primary metabolism to secondary metabolism, and 1300 m could be identified as the transition point. Particularly, phenylpropanoid metabolism and its metabolites (flavonoids and phenolic acids) played crucial roles in its adaptation to elevations. Moreover, 24 hub transcription factors (TFs) were screened through WGCNA and verified by RT-qPCR. Environmental factors not only directly influenced leaf functional traits, but also affected metabolite accumulation through TF-mediated gene expression, which in turn influenced leaf functional traits. This study highlights that integrating plant functional traits, metabolome and transcriptome simultaneously provides novel insights into the mechanisms for shaping plants' adaptability.

The Role of Plant Evolutionary History in Shaping the Variation in Specific Leaf Area Across China

Specific leaf area (SLA, leaf area per unit leaf dry mass) occupies a central position in both community assembly and ecosystem functioning. Although SLA has significant phylogenetic signals, how and to what extent the evolutionary history influences the variation in SLA remain poorly understood. In this study, based on a dataset containing 1264 plant species belonging to 549 genera and 141 families in gymnosperms, monocots, and eudicots across China, we analyzed the influences of climatic conditions and soil properties on SLA, calculated the phylogenetic signals of SLA, and quantified the relative contributions of evolutionary history (represented by interspecific relatedness and intraspecific variation) to the variation in SLA. The results showed that the interspecific relatedness accounts for 50.46% of the total variance in SLA, followed by the intraspecific variation (36.12%), climatic conditions (30.68%), and soil properties (24.74%). Along the phylogenetic tree, the split between angiosperms and gymnosperms had the largest contribution to the variation in SLA. Other detailed splits (e.g., the split between monocots and eudicots, the splits within Rosidae, and etc.) had significant but much smaller contributions. The relationship between SLA and environmental variables (climatic conditions and soil properties) was different between angiosperms and gymnosperms, with the climatic conditions having larger influences on SLA than the soil properties, implying interactive effects between environment and evolutionary history on SLA. Within the woody angiosperms, deciduous and evergreen species exhibited differential responses of SLA to climatic and soil factors, suggesting a non-negligible role of leaf longevity in explaining the variation in SLA. Our results highlighted a much more important role of evolutionary history in the variation in SLA than previous studies. Neglecting such a great contribution could lead to biased conclusions if the evolutionary rate does not keep pace with the rapidly changing environments in the future.

Fertilizer reduction and biochar amendment promote soil mineral-associated organic carbon, bacterial activity, and enzyme activity in a jasmine garden in southeast China

Reducing chemical fertilizers and biochar amendment is essential for achieving carbon neutrality, addressing global warming, and promoting sustainable agricultural development. Biochar amendment, a carbon rich soil additive produced through biomass pyrolysis, enhances soil fertility, increases crop yield, and improves soil carbon storage. However, research on the combined effect of fertilizer reduction and biochar amendment on soil mineral associated organic carbon (MAOC) in jasmine gardens is limited. This study aims to determine if biochar can reduce industrial fertilizer usage without compromising soil quality. This study focuses on jasmine cultivation in southeastern China, employing four treatments: conventional fertilization (CK), biochar amendment without fertilizer (BA), fertilizer reduction (FR), and fertilizer reduction with biochar amendment (FRBA). The effects on MAOC, microbial abundance, and enzyme activity were investigated. The FRBA treatment significantly increased MAOC content by 19.98 % compared to CK (P < 0.05). The BA and FRBA treatments enhanced the diversity of soil bacteria, including Lactobacillus, Azospirillum, and Cutibacterium, which are associated with soil organic carbon sequestration and nutrient decomposition. The RandomForest model identified β-N-acetyl-glucosaminidase (NAG), electric conductivity (EC), β-1, 4-Glucosidase (BG), soil potential of Hydrogen (pH), soil bulk density (BD), and β-D-cellobiosidase (CBH) as key soil traits promoting MAOC accumulation (P < 0.05). The results indicate that BA and FRBA improve soil bacterial community structure, enzyme activity, and MAOC content, promoting soil carbon accumulation through environmental factors and dominant bacteria. This study encourages future fertilization protocols that enhance fertilizer efficiency and carbon storage in crop soils.

A continental-scale analysis reveals the latitudinal gradient of stomatal density across amphistomatous species: evolutionary history vs. present-day environment

BACKGROUND AND AIMS

Amphistomy is a potential method for increasing photosynthetic rate; however, the latitudinal gradients of stomatal density across amphistomatous species and their drivers remain unknown.

METHODS

Here, the adaxial stomatal density (SDad) and abaxial stomatal density (SDab) of 486 amphistomatous species-site combinations, belonging to 32 plant families, were collected from China, and their total stomatal density (SDtotal) and stomatal ratio (SR) were calculated.

KEY RESULTS

Overall, these four stomatal traits did not show significant phylogenetic signals. There were no significant differences in SDab and SDtotal between woody and herbaceous species, but SDad and SR were higher in woody species than in herbaceous species. Besides, a significantly positive relationship between SDab and SDad was observed. We also found that stomatal density (including SDab, SDad and SDtotal) decreased with latitude, whereas SR increased with latitude, and temperature seasonality was the most important environmental factor driving it. Besides, evolutionary history (represented by both phylogeny and species) explained ~10- to 22-fold more of the variation in stomatal traits than the present-day environment (65.2-71.1 vs. 2.9-6.8 %).

CONCLUSIONS

Our study extended our knowledge of trait-environment relationships and highlighted the importance of evolutionary history in driving stomatal trait variability.

Grass leaf structural and stomatal trait responses to climate gradients assessed over the 20th century and across the Great Plains, USA

Abstract. Using herbarium specimens spanning 133 years and field-collected measurements, we assessed intraspecific trait (leaf structural and stomatal) variability from grass species in the Great Plains of North America. We focused on two widespread, closely related grasses from the tribe Paniceae: Dichanthelium oligosanthes subsp. scribnerianum (C3) and Panicum virgatum (C4). Thirty-one specimens per taxon were sampled from local herbaria from the years 1887 to 2013 to assess trait responses across time to changes in atmospheric [CO2] and growing season precipitation and temperature. In 2021 and 2022, the species were measured from eight grasslands sites to explore how traits vary spatially across natural continental precipitation and temperature gradients. Δ13C increased with atmospheric [CO2] for D. oligosanthes but decreased for P. virgatum, likely linked to increases in precipitation in the study region over the past century. Notably, this is the first record of decreasing Δ13C over time for a C4 species illustrating 13C linkages to climate. As atmospheric [CO2] increased, C:N increased and δ15N decreased for both species and %N decreased for D. oligosanthes. Across a large precipitation gradient, D. oligosanthes leaf traits were more responsive to changes in precipitation than those of P. virgatum. In contrast, only two traits of P. virgatum responded to increases in temperature across a gradient: specific leaf area (increase) and leaf dry matter content (decrease). The only shared significant trend between species was increased C:N with precipitation. Our work demonstrates that these closely related grass species with different photosynthetic pathways exhibited various trait responses across temporal and spatial scales, illustrating the key role of scale of inquiry for forecasting leaf trait responses to future environmental change.

Trait variation and performance across varying levels of drought stress in cultivated sunflower (Helianthus annuus L.)

Drought is a major agricultural challenge that is expected to worsen with climate change. A better understanding of drought responses has the potential to inform efforts to breed more tolerant plants. We assessed leaf trait variation and covariation in cultivated sunflower (Helianthus annuus L.) in response to water limitation. Plants were grown under four levels of water availability and assessed for environmentally induced plasticity in leaf stomatal and vein traits as well as biomass (performance indicator), mass fractions, leaf area, leaf mass per area, and chlorophyll content. Overall, biomass declined in response to stress; these changes were accompanied by responses in leaf-level traits including decreased leaf area and stomatal size, and increased stomatal and vein density. The magnitude of trait responses increased with stress severity and relative plasticity of smaller-scale leaf anatomical traits was less than that of larger-scale traits related to construction and growth. Across treatments, where phenotypic plasticity was observed, stomatal density was negatively correlated with stomatal size and positively correlated with minor vein density, but the correlations did not hold up within treatments. Four leaf traits previously shown to reflect major axes of variation in a large sunflower diversity panel under well-watered conditions (i.e. stomatal density, stomatal pore length, vein density, and leaf mass per area) predicted a surprisingly large amount of the variation in biomass across treatments, but trait associations with biomass differed within treatments. Additionally, the importance of these traits in predicting variation in biomass is mediated, at least in part, through leaf size. Our results demonstrate the importance of leaf anatomical traits in mediating drought responses in sunflower, and highlight the role that phenotypic plasticity and multi-trait phenotypes can play in predicting productivity under complex abiotic stresses like drought.

Response of stomatal density and size in Betula ermanii to contrasting climate conditions: The contributions of genetic and environmental factors

As plant distribution and performance are determined by both environmental and genetic factors, clarifying the contribution of these two factors is a key for understanding plant adaptation and predicting their distribution under ongoing global warming. Betula ermanii is an ideal species for such research because of its wide distribution across diverse environments. Stomatal density and size are crucial traits that plants undergo changes in to adapt to different environments as these traits directly influence plant photosynthesis and transpiration. In this study, we conducted a multi-location common garden experiment using B. ermanii to (1) clarify the contribution of both environmental and genetic factors to the variation in stomatal density and size of B. ermanii, (2) demonstrate the differences in the plasticity of stomatal density and size among B. ermanii populations, and (3) understand how stomatal density and size of B. ermanii would respond to increased temperature and changing precipitation patterns. Genetic factors played a more significant role in stomatal size than environmental factors, suggesting that B. ermanii struggles to adjust its stomatal size in response to a changing environment. Our results also revealed a positive correlation between stomatal size plasticity and original habitat suitability, indicating that in B. ermanii populations in harsh environments exhibit lower adaptability to environmental shifts. Although stomatal density and size of B. ermanii showed the significant responses to increased temperature and shifting precipitation patterns, the response ranges of stomatal density and size to the environmental factors varied among populations. Our findings highlighted the interplay between genetic and environmental factors in determining the intraspecific variation in stomatal density and size in B. ermanii. This indicated that certain populations of B. ermanii exhibit limited stomatal plasticity and adaptability, which could directly affect photosynthesis and transpiration, suggesting potential population-specific fitness implications for B. ermanii under future climate change.

Leaf stomatal traits rather than anatomical traits regulate gross primary productivity of moso bamboo (Phyllostachys edulis) stands

Leaf stomatal and anatomical traits strongly influence plant productivity. Understanding the environmental adaptation mechanisms of leaf stomatal and anatomical traits and their relationship with ecosystem productivity is essential to better understand and predict the long-term adaptation strategies to climate change of moso bamboo forests. Here, we selected 6 sites within the moso bamboo distribution area, measured 3 leaf stomatal traits and 10 leaf anatomical traits of unmanaged moso bamboo stands. We explored the spatial variation characteristics of these traits and their response to environmental changes, assessed the relationships among these traits at regional scales through network analysis, and tested the direct and indirect effects of environmental, leaf stomatal and anatomical traits on gross primary productivity (GPP) of bamboo stands using structural equation modeling (SEM). The results showed that both climate and soil factors significantly affected leaf stomatal and anatomical traits of moso bamboo. Solar radiation (SR) and mean annual precipitation (MAP) out of the climatic factors were the key drivers of variation in leaf stomatal and anatomical traits, respectively. Soil moisture and nutrients out of the soil properties significantly affected both leaf stomatal and anatomical traits of moso bamboo. Network analysis further indicated that there was a significant correlation between leaf stomata and anatomical traits. Stomatal size (SS) showed the highest centrality value at the regional scale, indicating that it plays a key role in adjusting the adaptation of plants to external environmental conditions. SEM analysis showed that environment did not directly but indirectly affect GPP via stomatal performance. The environment explained 53.3% and 39.2% of the variation in leaf stomatal and anatomical traits, respectively, and leaf stomatal traits explained 20.8% of the regional variation in GPP. Our results demonstrate a direct effect of leaf stomatal traits rather than leaf anatomical traits on bamboo ecosystem productivity, which provides new insights into model predictions of bamboo forests under global climate change.

Stomatal opening ratio mediates trait coordinating network adaptation to environmental gradients

A trait coordination network is constructed through intercorrelations of functional traits, which reflect trait-based adaptive strategies. However, little is known about how these networks change across spatial scales, and what drivers and mechanisms mediate this change. This study bridges that gap by integrating functional traits related to plant carbon gain and water economy into the coordination network of Siberian elm (Ulmus pumila), a eurybiont that survives along a 3800 km environmental gradient from humid forest to arid desert. Our results demonstrated that both stomatal density and stomatal size reached a physiological threshold at which adjustments in these traits were not sufficient to cope with the increased environmental stress. Network analysis further revealed that the mechanism for overcoming this threshold, the stomatal opening ratio, g_ratio , was represented by the highest values for centrality across different spatial scales, and therefore mediated the changes in the trait coordination network along environmental gradients. The mediating roles manifested as creating the highest maximum theoretical stomatal conductance (g_smax ) but lowest possible g_ratio for pathogen defense in humid regions, while maintaining the g_ratio 'sweet spot' (c. 20% in this region) for highest water use efficiency in semihumid regions, and having the lowest g_smax and highest g_ratio for gas exchange and leaf cooling in arid regions. These results suggested that the stomatal traits related to control of stomatal movement play fundamental roles in balancing gas exchange, leaf cooling, embolism resistance and pathogen defense. These insights will allow more accurate model parameterization for different regions, and therefore better predictions of species' responses to global change.

A chromosome-level genome assembly of the Chinese cork oak (Quercus variabilis)

Quercus variabilis (Fagaceae) is an ecologically and economically important deciduous broadleaved tree species native to and widespread in East Asia. It is a valuable woody species and an indicator of local forest health, and occupies a dominant position in forest ecosystems in East Asia. However, genomic resources from Q. variabilis are still lacking. Here, we present a high-quality Q. variabilis genome generated by PacBio HiFi and Hi-C sequencing. The assembled genome size is 787 Mb, with a contig N50 of 26.04 Mb and scaffold N50 of 64.86 Mb, comprising 12 pseudo-chromosomes. The repetitive sequences constitute 67.6% of the genome, of which the majority are long terminal repeats, accounting for 46.62% of the genome. We used ab initio, RNA sequence-based and homology-based predictions to identify protein-coding genes. A total of 32,466 protein-coding genes were identified, of which 95.11% could be functionally annotated. Evolutionary analysis showed that Q. variabilis was more closely related to Q. suber than to Q. lobata or Q. robur. We found no evidence for species-specific whole genome duplications in Quercus after the species had diverged. This study provides the first genome assembly and the first gene annotation data for Q. variabilis. These resources will inform the design of further breeding strategies, and will be valuable in the study of genome editing and comparative genomics in oak species.

Influence of Geographical and Climatic Factors on Quercus variabilis Blume Fruit Phenotypic Diversity

Quercus variabilis Blume is one of the most ecologically valuable tree species in China and is known to have adaptive mechanisms to climate change. Our objective was to quantify the variation pattern in the fruit morphology of Q. variabilis. Fruit samples were collected from 43 natural populations in autumn of 2019. Our results indicated that the coefficient of variation (CV) of the fruit length (FL) and fruit width (FW) were 10.08% and 11.21%, respectively. There were significant differences in the FL, FW, and fruit length-to-width ratios (FL/FW) among the studied populations. Also, there was a significant positive correlation between the FW and FL. The FL decreased with increasing precipitation in the wettest quarter (PWQ). A concave trend was observed in the variations in FL with the equivalent latitude (ELAT), longitude (LON), annual mean air temperature (MAT), and annual precipitation (AP). A similar concave trend was observed for the FL/FW with LON, MAT, and AP. A positive correlation was observed between the FW, FL and FL/FW, and the ELAT. The cluster analysis revealed five groups of the 43 natural populations. Our study findings suggests that Q. variabilis has high levels of phenotypic plasticity for geographical and climatic factors.