Understanding Of Plant Responses Research Articles

Updating the dual C and O isotope-Gas-exchange model: A concept to understand plant responses to the environment and its implications for tree rings.

The combined study of carbon (C) and oxygen (O) isotopes in plant organic matter has emerged as a powerful tool for understanding plant functional responses to environmental change. The approach relies on established relationships between leaf gas exchange and isotopic fractionation to derive a series of model scenarios that can be used to infer changes in photosynthetic assimilation and stomatal conductance driven by changes in environmental parameters (CO2 , water availability, air humidity, temperature, nutrients). We review the mechanistic basis for a conceptual model, in light of recently published research, and discuss where isotopic observations do not match our current understanding of plant physiological response to the environment. We demonstrate that (1) the model was applied successfully in many, but not all studies; (2)although originally conceived for leaf isotopes, the model has been applied extensively to tree-ring isotopes in the context of tree physiology and dendrochronology. Where isotopic observations deviate from physiologically plausible conclusions, this mismatch between gas exchange and isotope response provides valuable insights into underlying physiological processes. Overall, we found that isotope responses can be grouped into situations of increasing resource limitation versus higher resource availability. The dual-isotope model helps to interpret plant responses to a multitude of environmental factors.

Spatiotemporal patterns of wheat response to Pyrenophora tritici-repentis in asymptomatic regions revealed by transcriptomic and X-ray fluorescence microscopy analyses.

Pathogen attacks elicit dynamic and widespread molecular responses in plants. While our understanding of plant responses has advanced considerably, little is known of the molecular responses in the asymptomatic "green" regions (AGR) adjoining lesions. Here, we explore gene expression data and high-resolution elemental imaging to report the spatiotemporal changes in the AGR of susceptible and moderately resistant wheat cultivars infected with a necrotrophic fungal pathogen, Pyrenophora tritici-repentis (Ptr). We show, with improved spatiotemporal resolution, that calcium oscillations are modified in the susceptible cultivar, resulting in "frozen" host defence signals at the mature disease stage, and silencing of the host's recognition and defence mechanisms which would otherwise protect it from further attacks. In contrast, Ca accumulation and heightened defence response was observed in the moderately resistant cultivar in the later stage of disease development. Furthermore, in the susceptible interaction, the AGR was unable to recover post disease disruption. Our targeted sampling technique also enabled detection of eight previously predicted proteinaceous effectors in addition to the known ToxA effector. Collectively, our results highlight the benefits of spatially resolved molecular analysis and nutrient mapping to provide high-resolution spatiotemporal snapshots of host-pathogen interactions, paving the way for detangling complex disease interactions in plants.

Sensitivity of seed germination to water stress in high-altitude populations of a threatened palm species.

Divergence in seed germination patterns among populations of the same species is important for understanding plant responses to environmental gradients and potential plant sensitivity to climate change. In order to test the responses to flooding and decreasing water potentials we germinated and grew seeds of three habitats of Euterpe edulis Mart. occurring along an altitudinal gradient, over a period of three years. Seed germination and root growth were evaluated under different water availability treatments: control, flood, -0.4MPa, -0.8MPa, for 2012, 2013 and 2014 years, and in the last year of the experiment (2014), -1.0MPa and -1.5MPa. Seeds of the montane habitat did not germinate in the flood treatment. Seed germination of all three habitats decreased in the -1.5MPa treatment. Montane habitat had the lowest seed germination at -1.5MPa. Time required for half of the seeds to germinate increased up to -0.8MPa. Seeds of montane habitats germinated slower in all the treatments. The only difference observed in seed germination synchrony was an increase in submontane population in flooding treatment. However, synchrony decreased at the lowest water potential treatments. Roots of montane population were more vigorous in most treatments, except in -0.8 MPa. The unusual ability of seeds to germinate at low water potentials might be related to early seed germination at the onset of the rainy season, potentially decreasing seed predation pressure. Seeds of the montane population were more sensitive to both types of water stress. A predicted increase in the frequency and intensity of extreme high rainfall or drought events may predispose early stages of this population to adverse factors, which might negatively affect population viability along elevational in future climate change scenarios.

Spatial patterns and climatic factors influence the branch xylem anatomical traits of Reaumuria soongarica in the desert region of northwestern China

The xylem is the water transport tissue of vascular plants, and its structure is closely related to the efficiency and safety of water transport. Studying how xylem anatomical traits and related functional traits vary with environmental gradients is important for understanding plant responses to environmental changes and ecological adaptation strategies. In this study, ten populations of the dominant shrub Reaumuria soongarica were selected along a west-east transect using an aridity index (AI, the ratio of annual precipitation to annual potential evapotranspiration) ranging from 0.02 to 0.09 in the desert region of northwest China. Based on AI, the sampling sites were divided into arid regions (0.05 ≤ AI < 0.2) and hyper-arid regions (AI < 0.05). Pearson correlation analysis, linear mixed models, and plant trait networks were used to analyze the spatial variation characteristics and climatic factors of 12 traits in three categories, including xylem anatomical traits, hydraulic functional traits, and mechanical strength. The results were as follows: (1) Vessel diameter contributing 95% hydraulic conductivity (D95) and wood density (WD) significantly differed between arid and hyper-arid regions, whereas the other traits were not significantly different. (2) Mean temperature of the driest quarter was one of the most important climatic factors driving the most trait variation. With the increase in AI and the precipitation of the driest quarter, D95 and the vessel grouping index (Vg) significantly increased, but not WD. The mean temperature of the driest quarter was significantly negatively correlated with D95 and WD but not significantly correlated with Vg. (3) Correlations between most traits were significant, but Vg was not significantly correlated with all other traits. Theoretical hydraulic conductivity was significantly positively correlated with the vulnerability index, indicating a trade-off between the efficiency and safety of the xylem hydraulic system. (4) Coordination among multiple traits differed at the transect and regional climate levels, and the number of edges of the trait network of hyper-arid regions was more than that of arid regions. Moreover, network analyses showed that mean vessel diameter and theoretical hydraulic conductivity are central traits in arid and hyper-arid regions, respectively, because of the number and strength of the relationships with other traits, which could be the important predictor of related hydraulic functions and associations. In conclusion, the xylem anatomical structure of R. soongarica can adapt to changing environments by different combinations of functional traits. Plant trait networks provide a novel approach for exploring the adaptation strategies of desert shrubs along environmental gradients with future climate change.

Nanobionics: A Sustainable Agricultural Approach towards Understanding Plant Response to Heavy Metals, Drought, and Salt Stress.

In the current scenario, the rising concentration of heavy metals (HMs) due to anthropogenic activities is a severe problem. Plants are very much affected by HM pollution as well as other abiotic stress such as salinity and drought. It is very important to fulfil the nutritional demands of an ever-growing population in these adverse environmental conditions and/or stresses. Remediation of HM in contaminated soil is executed through physical and chemical processes which are costly, time-consuming, and non-sustainable. The application of nanobionics in crop resilience with enhanced stress tolerance may be the safe and sustainable strategy to increase crop yield. Thus, this review emphasizes the impact of nanobionics on the physiological traits and growth indices of plants. Major concerns and stress tolerance associated with the use of nanobionics are also deliberated concisely. The nanobionic approach to plant physiological traits and stress tolerance would lead to an epoch of plant research at the frontier of nanotechnology and plant biology.

Mining of Stress-related Genes in Pigmented and Non-pigmented Rice using Gene Co-expression Network and Clustering Approaches

Pigmented rice has been associated with stress-resistant traits, such as resistance to abiotic and biotic stresses, but the genes network that is responsible for such traits remains limited. Hence, this study aims to identify stress-related genes in the pigmented rice using computational approaches. The gene co-expression network was constructed using Pearson Correlation Coefficient (PCC) ≥ 0.9 among differentially expressed genes (DEGs) of trancriptomes between pigmented and non-pigmented rice. The gene co-expression network was clustered using Markov Cluster algorithm (MCL) to identify the functional modules and the hub genes for each module were determined. The functional analyses were performed to each module to determine the related gene ontology (GO) and pathway. Protein-protein interaction (PPI) from STRING database was used to validate the functional analyses. A total of 721 DEGs were used to construct the gene co-expression network of pigmented and non-pigmented rice varieties. Of these, 614 DEGs with 15,259 edges were identified by PCC. Using MCL, 10 clusters were identified in the gene co-expression network of pigmented and non-pigmented rice varieties. Three clusters were enriched with seven GO terms (i.e., response to stress, response to stimulus, transcription factor activity) that are related to stress-resistant traits, indicating the highly correlated genes were the stress-related genes. Interestingly, nine hub genes were found to be related to drought tolerance, disease resistance and hormone biosynthesis. Validation of hub genes using STRING database revealed that 48 hub genes were also connected in the PPI network, suggesting their potential as candidate proteins in stress-related traits. This study demonstrated that the molecular interaction network and the network clustering approach are efficient in identifying the stress-related genes, which could provide new insights in understanding plant responses to abiotic and biotic stresses.

Potential and limits of (mal)adaptive mutation rate plasticity in plants.

Genetic mutations provide the heritable material for plant adaptation to their environments. At the same time, the environment can affect the mutation rate across plant genomes. However, the extent to which environmental plasticity in mutation rates can facilitate or hinder adaptation remains a longstanding and unresolved question. Emerging discoveries of mechanisms affecting mutation rate variability provide opportunities to consider this question in a new light. Links between chromatin states, transposable elements, and DNA repair suggest cases of adaptive mutation rate plasticity could occur. Yet, numerous evolutionary and biological forces are expected to limit the impact of any such mutation rate plasticity on adaptive evolution. Persistent uncertainty about the significance of mutation rate plasticity on adaptation motivates new experimental and theoretical research relevant to understanding plant responses in changing environments.

Multi-stress resilience in plants recovering from submergence.

Submergence limits plants' access to oxygen and light, causing massive changes in metabolism; after submergence, plants experience additional stresses, including reoxygenation, dehydration, photoinhibition and accelerated senescence. Plant responses to waterlogging and partial or complete submergence have been well studied, but our understanding of plant responses during post-submergence recovery remains limited. During post-submergence recovery, whether a plant can repair the damage caused by submergence and reoxygenation and re-activate key processes to continue to grow, determines whether the plant survives. Here, we summarize the challenges plants face when recovering from submergence, primarily focusing on studies of Arabidopsis thaliana and rice (Oryza sativa). We also highlight recent progress in elucidating the interplay among various regulatory pathways, compare post-hypoxia reoxygenation between plants and animals and provide new perspectives for future studies.

Functional traits of riparian trees in the lower Fitzroy River, Western Australia

AbstractRiparian trees are critically important for maintaining the ecological function of freshwater ecosystems. Globally, anthropogenic changes to water regimes are impacting the health and distribution of riparian trees. Understanding the physiological constraints on the distribution of riparian tree species in relation to the water regime is essential for informed water resource management that seeks to limit impacts on riparian trees. To fill an identified knowledge gap for the Fitzroy River, a significant river in the wet–dry tropics of north‐western Australia, we used a trait‐based approach to characterise nine common riparian tree species in relation to their distribution along a hydrological gradient. We assessed key functional traits related to drought and flood flows. Leaf mass per unit area (LMA), leaf dry matter content (LDMC), foliar carbon content (% C) and the ratio of carbon to nitrogen (C:N) are broadly related to plant productivity and durability and may reflect resistance to fluvial stress. Traits related to water availability were stem specific density (SSD), mean xylem vessel diameter and xylem vessel density, as well as foliar δ13C which is related to water use efficiency, and leaf osmotic potential at full hydration (π100) as a measure of drought tolerance. We found that π100, δ13C and SSD values reflected species hydrological habitat preferences, with higher δ13C values and lower π100 for species distributed in the drier floodplain habitats, compared with species constrained to the riverbank. Low SSD values for species close to the riverbank may be indicative of aerenchyma tissue in response to flooding. Differences in leaf trait values were primarily attributed to differences between evergreen Myrtaceous and deciduous non‐Myrtaceous species, rather than hydrological habitat preferences. LMA was greatest for the Myrtaceous study species, with deciduous non‐Myrtaceous species associated with wetter habitats having the lowest values. The physiology of riparian trees in northern Australia is not well described for the majority of species. Our study provides insight into plant functional strategies in response to both flooding and drought and is a critical step in understanding plant responses to future water‐take scenarios to support evidence‐based decision making.

Combined effects of warming and drought on plant biomass depend on plant woodiness and community type: a meta-analysis.

Global warming and precipitation extremes (drought or increased precipitation) strongly affect plant primary production and thereby terrestrial ecosystem functioning. Recent syntheses show that combined effects of warming and precipitation extremes on plant biomass are generally additive, while individual experiments often show interactive effects, indicating that combined effects are more negative or positive than expected based on the effects of single factors. Here, we examined whether variation in biomass responses to single and combined effects of warming and precipitation extremes can be explained by plant growth form and community type. We performed a meta-analysis of 37 studies, which experimentally crossed warming and precipitation treatments, to test whether biomass responses to combined effects of warming and precipitation extremes depended on plant woodiness and community type (monocultures versus mixtures). Our results confirmed that the effects of warming and precipitation extremes were overall additive. However, combined effects of warming and drought on above- and belowground biomass were less negative in woody- than in herbaceous plant systems and more negative in plant mixtures than in monocultures. We further show that drought effects on plant biomass were more negative in greenhouse- than in field studies, suggesting that greenhouse experiments may overstate drought effects in the field. Our results highlight the importance of plant system characteristics to better understand plant responses to climate change.

A low cost, low power sap flux device for distributed and intensive monitoring of tree transpiration

Accurate estimation of transpiration in individual trees is important for understanding plant responses to environmental drivers, closing the water balance in forest stands and catchments, and calibrating earth system models, among other applications. However, the cost and power consumption of commercial systems based on sap flow methods still limit their usage. We developed and tested a cost-effective (<$150), simple to construct, and energy efficient sap flux device based on the heat pulse method. Energy savings were achieved by reducing the voltage of heat pulses and using an internal clock to completely shut down the device between pulses. Device accuracy was confirmed by laboratory estimates of sap flow made on excised branches of Acer saccharum and Tsuga canadensis (adjusted R2 = 0.96). In a 174-d field installation of 12 devices, batteries (eight rechargeable Ni-MH AA) needed to be replaced every 14 days. Sap flux measurements in the field tracked expected variations in vapor pressure deficit and tree phenology. The low cost, compact design, reliability, and power consumption of this device enable sap flux studies to operate with more replication and in more diverse ecological settings than has been practical in the past.

Quantification of root water uptake and redistribution using neutron imaging: a review and future directions.

Quantifying root water uptake is essential to understanding plant water use and responses to different environmental conditions. However, non-destructive measurement of water transport and related hydraulics in the soil-root system remains a challenge. Neutron imaging, with its high sensitivity to hydrogen, has become an unparalleled tool to visualize and quantify root water uptake in vivo. In combination with isotopes (e.g., deuterated water) and a diffusion-convection model, root water uptake and hydraulic redistribution in root and soil can be quantified. Here, we review recent advances in utilizing neutron imaging to visualize and quantify root water uptake, hydraulic redistribution in roots and soil, and root hydraulic properties of different plant species. Under uniform soil moisture distributions, neutron radiographic studies have shown that water uptake was not uniform along the root and depended on both root type and age. For both tap (e.g., lupine [Lupinus albus L.]) and fibrous (e.g., maize [Zea mays L.]) root systems, water was mainly taken up through lateral roots. In mature maize, the location of water uptake shifted from seminal roots and their laterals to crown/nodal roots and their laterals. Under non-uniform soil moisture distributions, part of the water taken up during the daytime maintained the growth of crown/nodal roots in the upper, drier soil layers. Ultra-fast neutron tomography provides new insights into 3D water movement in soil and roots. We discuss the limitations of using neutron imaging and propose future directions to utilize neutron imaging to advance our understanding of root water uptake and soil-root interactions.

Salicylic Acid, a Multifaceted Hormone, Combats Abiotic Stresses in Plants.

In recent decades, many new and exciting findings have paved the way to the better understanding of plant responses in various environmental changes. Some major areas are focused on role of phytohormone during abiotic stresses. Salicylic acid (SA) is one such plant hormone that has been implicated in processes not limited to plant growth, development, and responses to environmental stress. This review summarizes the various roles and functions of SA in mitigating abiotic stresses to plants, including heating, chilling, salinity, metal toxicity, drought, ultraviolet radiation, etc. Consistent with its critical roles in plant abiotic tolerance, this review identifies the gaps in the literature with regard to the complex signalling network between SA and reactive oxygen species, ABA, Ca2+, and nitric oxide. Furthermore, the molecular mechanisms underlying signalling networks that control development and stress responses in plants and underscore prospects for future research on SA concerning abiotic-stressed plants are also discussed.

Understanding the physiological and biophysical response of urban roadside plantations for assessing adaptation and mitigation mechanisms toward vehicular emissions

The plants follow various strategies for adapting and mitigating climatic and environmental stresses. This offers an opportunity to comprehend adaptation and mitigation mechanisms under changing climate and environment emerging from vehicular emissions. We deployed an approach, i.e., physiological (Phy) and biophysical (Bioph) functional traits (FTs) based approach to understand plant response for assessing adaptation and mitigation potential for offsetting long-term urban climate and environment. We investigated Phy and Bioph FTs of adaptation, especially transpiration rate (E), stomatal conductance (Gs) and resistance (SRes), water use efficiency (WUE), carboxylation efficiency (CE), mesophyll efficiency (ME), leaf thickness (LTh), and mitigation FTs, including CO2 assimilation rate (A), leaf dust retention efficiency (DRE), and cooling impacts (CI) of the roadside plantation (Delonix regia and Callistemon viminalis). The study reported the significant effects of the roadside urban environment on the modulation of FTs, one of the strategies that plants follow to adapt and mitigate the urban climate. The C. viminalis was reported as having a better adaptive nature with higher mitigation potential than the D. regia. It is advocated that the approach deployed in the study could be exploited for identifying more adaptive plantation species to develop urban green belts for mitigating urban climate and environments.

Leaf trait association in relation to herbivore defense, drought resistance, and economics in a tropical invasive plant

Exploring how functional traits vary and covary is important to understand plant responses to environmental change. However, we have limited understanding of the ways multiple functional traits vary and covary within invasive species. We measured 12 leaf traits of an invasive plant Chromolaena odorata, associated with plant or leaf economics, herbivore defense, and drought resistance on 10 introduced populations from Asia and 12 native populations from South and Central America, selected across a broad range of climatic conditions, and grown in a common garden. Species' range and climatic conditions influenced leaf traits, but trait variation across climate space differed between the introduced and native ranges. Traits that confer defense against herbivores and drought resistance were associated with economic strategy, but the patterns differed by range. Plants from introduced populations that were at the fast-return end of the spectrum (high photosynthetic capacity) had high physical defense traits (high trichome density), whereas plants from native populations that were at the fast-return end of the spectrum had high drought escape traits (early leaf senescence and high percentage of withered shoots). Our results indicate that invasive plants can rapidly adapt to novel environmental conditions. Chromolaena odorata showed multiple different functional trait covariation patterns and clines in the native and introduced ranges. Our results emphasize that interaction between multiple traits or functions should be considered when investigating the adaptive evolution of invasive plants.

Close-range hyperspectral spectroscopy reveals leaf water content dynamics

Water plays a crucial role in maintaining plant functionality and drives many ecophysiological processes. The distribution of water resources is in a continuous change due to global warming affecting the productivity of ecosystems around the globe, but there is a lack of non-destructive methods capable of continuous monitoring of plant and leaf water content that would help us in understanding the consequences of the redistribution of water. We studied the utilization of novel small hyperspectral sensors in the 1350–1650 nm and 2000–2450 nm spectral ranges in non-destructive estimation of leaf water content in laboratory and field conditions. We found that the sensors captured up to 96% of the variation in equivalent water thickness (EWT, g/m2) and up to 90% of the variation in relative water content (RWC). Further tests were done with an indoor plant (Dracaena marginate Lem.) by continuously measuring leaf spectra while drought conditions developed, which revealed detailed diurnal dynamics of leaf water content. The laboratory findings were supported by field measurements, where repeated leaf spectra measurements were in fair agreement (R2 = 0.70) with RWC and showed similar diurnal dynamics. The estimation of leaf mass per area (LMA) using leaf spectra was investigated as a pathway to improved RWC estimation, but no significant improvement was found. We conclude that close-range hyperspectral spectroscopy can provide a novel tool for continuous measurement of leaf water content at the single leaf level and help us to better understand plant responses to varying environmental conditions.

Impact of Combined Heat and Salt Stresses on Tomato Plants-Insights into Nutrient Uptake and Redox Homeostasis.

Currently, salinity and heat are two critical threats to crop production and food security which are being aggravated by the global climatic instability. In this scenario, it is imperative to understand plant responses to simultaneous exposure to different stressors and the cross-talk between underlying functional mechanisms. Thus, in this study, the physiological and biochemical responses of tomato plants (Solanum lycopersicum L.) to the combination of salinity (100 mM NaCl) and heat (42 °C; 4 h/day) stress were evaluated. After 21 days of co-exposure, the accumulation of Na+ in plant tissues was superior when salt-treated plants were also exposed to high temperatures compared to the individual saline treatment, leading to the depletion of other nutrients and a harsher negative effect on plant growth. Despite that, neither oxidative damage nor a major accumulation of reactive oxygen species took place under stress conditions, mostly due to the accumulation of antioxidant (AOX) metabolites alongside the activation of several AOX enzymes. Nonetheless, the plausible allocation of resources towards the defense pathways related to oxidative and osmotic stress, along with severe Na toxicity, heavily compromised the ability of plants to grow properly when the combination of salinity and heat was imposed.

Daytime and nighttime warming has no opposite effects on vegetation phenology and productivity in the northern hemisphere

Over the past 50 years, global land surface air temperature has been rising at a much higher rate at night than during the day. Understanding plant responses to the asymmetric daytime and nighttime warming in the context of climate change has been a hot topic in global change biology and global ecology. It has been debatable whether the asymmetric warming has opposite effects on vegetation activity (e.g., phenology, productivity). Here we settle the debate by scrutinizing the underpinnings of different statistical methods and revealing how the misuse or improper use of these methods could mischaracterize the effects of asymmetric warming with in situ and satellite observations. The use of the ordinary least square (OLS) methods including both daytime (Tmax) and nighttime (Tmin) temperature in the multiple regression models could overlook the multicollinearity problem and yield the misinterpretations that Tmax and Tmin had opposite effects on spring phenology, autumn phenology, gross primary production (GPP), and normalized difference vegetation index (NDVI). However, when the OLS methods were applied with Tmax and Tmin included in separate models or alternatively the ridge regression (RR) method with properly selected ridge parameter was used, the effects of Tmax and Tmin on vegetation activity were generally in the same direction. The use of the RR method with improperly selected ridge parameter could also mischaracterize the effects of asymmetric warming. Our findings show that daytime and nighttime warming has no opposite effects on vegetation phenology and productivity in the northern hemisphere, and properly dealing with the multicollinearity problem is critical for understanding the effects of asymmetric warming on vegetation activity.

Drought and Subsequent Soil Flooding Affect the Growth and Metabolism of Savoy Cabbage.

An important factor of current climate change is water availability, with both droughts and flooding becoming more frequent. Effects of individual stresses on plant traits are well studied, although less is known about the impacts of sequences of different stresses. We used savoy cabbage to study the consequences of control conditions (well-watered) versus continuous drought versus drought followed by soil flooding and a potential recovery phase on shoot growth and leaf metabolism. Under continuous drought, plants produced less than half of the shoot biomass compared to controls, but had a >20% higher water use efficiency. In the soil flooding treatment, plants exhibited the poorest growth performance, particularly after the “recovery” phase. The carbon-to-nitrogen ratio was at least twice as high, whereas amino acid concentrations were lowest in leaves of controls compared to stressed plants. Some glucosinolates, characteristic metabolites of Brassicales, showed lower concentrations, especially in plants of the flooding treatment. Stress-specific investment into different amino acids, many of them acting as osmolytes, as well as glucosinolates, indicate that these metabolites play distinct roles in the responses of plants to different water availability conditions. To reduce losses in crop production, we need to understand plant responses to dynamic climate change scenarios.

Adaptive variation among oaks in wood anatomical properties is shaped by climate of origin and shows limited plasticity across environments

Abstract Climate is a major evolutionary force in driving adaptive differentiation and plasticity in plant function. Xylem anatomy and hydraulic architecture are critical to water use, growth and responses of trees to drought and thus important in delimiting their ecological niches. How wood properties have been shaped through evolution by their climatic origins and the importance of plasticity for species persistence remain open questions critical to understanding plant responses to changing climate. We measured 11 wood anatomical traits for 18 Quercus (oak) species in arboreta that span contrasting climates (California‐US, southwestern France and central England). We investigated coordinate evolution of xylem anatomical properties with climatic niche and intraspecific variation in relation to growth environment. Species originating from climates with drier summers had traits associated with higher resistance to drought—higher density of vasicentric tracheids (VT), lower vessel hydraulic diameter (Dmh) and lower hydraulic conductivity. Species that evolved in climates with drier, hotter summers or colder winters had higher numbers of VT than those from mesic climates, supporting hypotheses that VT are critical for water transport during drought. We found limited intraspecific variation in xylem traits associated with growth environment—only four traits (pit fraction, VT, vessel density and Dmh)—differed among gardens. Xylem traits showed high lability across the phylogeny, consistent with evidence for parallel sympatric adaptive radiation and global diversification of the oaks. Our results provide evidence for the physiological mechanisms that underlie adaptation to changing environments and responses to climate change.