Tree physiology最新文献

Grapevine health and resilience under climate change demand an understanding of how multiple stress interact. Climate change has led to more frequent and intense droughts and heat waves, which often occur together and may affect disease pressure. Here, we explored a complex multi-stress framework by combining drought and heat stress with downy mildew infection in grapevine, determining their possible interactions (synergistic or antagonistic) on pathogenesis, and detailing their effects on grapevine leaf physiology. We subjected grapevines to drought, heat stress, or a combination of both, subsequently inoculating leaves with Plasmopara viticola. In these same leaves we quantified their physiological responses and changes in defense-related metabolite (H2O2 and phenols) concentrations. Our results revealed common and distinct responses to the multi-stress interactions. Drought and drought-heat treatments led to low stomatal conductance (a reduction in stomatal aperture), which acted as a biophysical mechanism restricting P. viticola entry and resulting in a lower P. viticola sporulation rate. Defense-related metabolites were differentially regulated according to the stress combination and suggesting a role in the biochemical mechanism against the P. viticola infection. Stilbene concentration increased by 36, 57 and 113% in response to drought, heat, and drought-heat, respectively. Flavonoids and phenolic acids exhibited distinct patterns in response to different stress treatments. These results shed light on the mechanisms that drive complex interactions between abiotic and biotic stressors, enhancing our understanding of multi-stress resilience and allowing us to better predict how grapevines will respond to the changing climate.

Plants deploy complex transcriptional responses to herbivores yet differences in the responses to generalist versus specialist insects, especially in long-lived tree species, are still poorly understood. Here, we analysed the transcriptional responses in Quercus robur L. leaves to infestation by two chewing insect species: the specialist moth Tortrix viridana L. and the generalist moth Lymantria dispar L. Regardless of insect species, we observed extensive gene induction. Key regulators such as the transcription factors MYC2, JAZ and ERF1, primarily activate defence gene expression via jasmonate and ethylene pathways after feeding by the generalist or the specialist. A total of 1591 genes were differentially expressed between the two herbivore treatments. Feeding by L. dispar triggered a broader transcriptional response, stronger activating pathways related to jasmonate, abscisic acid, auxin and ethylene signalling, as well as genes involved in terpene synthesis, monooxygenase activity and phloem development. In contrast, T. viridana induced a more specialized profile, including genes associated with serine-type endopeptidase activity, cell wall and cell wall organization, such as those encoding hydroxyproline-rich glycoproteins or pectin esterase inhibitors. This suggests a role of cell wall-related defences in response to specialist herbivores. Network analysis of Arabidopsis thaliana (L.) Heynh. homologues highlighted MYC2 as a central regulatory hub in both responses. Activation of MYC2 triggers downstream responses, including the induction of secondary metabolism genes, e.g., QrTPS1 encoding a functional sesquiterpene synthase, with germacrene D as its primary product. Transcriptional differences between resistant and susceptible oak genotypes were more pronounced following specialist than generalist herbivore feeding. These results provide insights into genome-scale herbivore-specific and genotype-mediated defence programmes at the transcriptome level and highlight promising gene targets for future functional genomics and natural variation studies in a keystone forest tree.

Convergence in strategies and traits that minimise drought damage and promote recovery have been shown to explain favourable drought responses in trees (Choat et al. 2012). Conversely, diversity and variation, in many ways, underpin biological resilience. Biodiversity can be a marker of ecosystem resilience, particularly in the face of climate extremes (Isbell et al. 2015) and diversity in hydraulic traits has been shown to increase forest resilience to drought (Anderegg et al. 2018). Additionally, high variation in traits, even within individual trees, has been linked to species' drought survival and recovery (Rodriguez-Dominguez et al. 2018, Cardoso et al. 2020, Johnson et al. 2022). Skelton et al. (2025) use six tree species from a South-African plant community to assess the power of commonly measured traits and metrics to predict drought responses. They also assess whether there is evidence for species convergence around strategies that promote drought survival and recovery. A natural drought during the experiment provided the ideal opportunity to test whether measured and calculated markers for drought resistance can accurately predict the extent of damage and recovery in the trees residing in this unique drought-prone biome.

The effect of ectomycorrhizal (ECM) fungi on the absorption and transport of heavy metals by host plants remains elusive. We experimentally assessed rapid cadmium (Cd) diffusion by two species of Suillus mycelium. Furthermore, we evaluated Cd absorption by ECM Pinus thunbergii Parl. and used transcriptomics to study the gene expression of P. thunbergii under Cd stress. In vitro experiments revealed that Cd2+ was transported through the apoplastic space more rapidly than through the mycelial symplast. The net Cd2+ influx rates in epitaxial hyphae were the highest, followed by those in the mantle of P. thunbergii inoculated with Suillus, whereas the lowest influx rate was found in the ECM-free fine root portions. Under Cd stress, the expression levels of PtZnTs, PtZIPs and PtHMA2 in ECM P. thunbergii roots were significantly higher than those in non-mycorrhized P. thunbergii. The assessment of Cd distribution in P. thunbergii revealed that Cd was transported to the needles of ECM P. thunbergii after 48 h; however, it was not detected in non-mycorrhized P. thunbergii. The essential element Cu exhibited similar results as the non-essential element Cd. Furthermore, two species ECM fungi Suillus accelerates the uptake and transport of Cd in the host plant P. thunbergii.

Casuarina equisetifolia, a key pioneer species in tropical and subtropical coastal shelterbelts, suffers from ecological decline owing to recurrent infestations by Lymantria xylina. To address this, we deciphered the molecular defence mechanisms and identified reliable biomarker metabolites for resistance breeding. Phenotypic analyses suggesting that the resistance to L. xylina was jointly mediated by antixenosis and antibiosis, and three resistant half-sib families (3-52, 5-80, and 5-218) were preliminarily identified. Integrated transcriptomic and metabolomic profiling of L. xylina herbivory demonstrated significant enrichment of differentially expressed genes (DEGs) in the circadian rhythm - plant, jasmonic acid (JA) signaling, and phenylpropanoid biosynthesis pathways, which may mediate the optimization of defence responses. In parallel, differential accumulation metabolites (DAMs) were predominantly enriched in α-linolenic acid metabolism. In particular, the content of α-linolenic acid strongly correlated with resistance, while flavonoids and tannins also exhibited significant positive correlations, confirming their roles in the defence response. These results suggest that the α-linolenic acid to phenylpropanoid cascade may function as a core defence axis in C. equisetifolia against L. xylina. Collectively, α-linolenic acid, flavonoids, and tannins serve as candidate biomarkers for breeding insect-resistant C. equisetifolia genotypes.

Reactive nitrogen (N) deposition has increased in southern China, potentially influencing forest carbon and water exchange processes. Cunninghamia lanceolata dominates as the most extensively planted and economically fast-growing timber species in subtropical China, but how C. lanceolata would respond to increased N deposition remains incompletely understood. In this study, we analyzed the responses of water utilization to increased N deposition at a manipulative experiment with N addition in a C. lanceolata plantation. Four treatments were established including N addition of 25 kg ha-1 yr-1 (N1; low concentration), 50 kg ha-1 yr-1 (N2; medium concentration), 100 kg ha-1 yr-1 (N3; high concentration) applied as NH4Cl solution, and control treatment (CK). Results showed that N3 treatment significantly increased leaf N content. N3 treatment enhanced intrinsic water use efficiency as evidenced by leaf carbon isotope composition (δ13C), and leaf-level stomatal conductance as indicated by leaf oxygen isotopic composition (δ18O). Similarly, N3 treatment enhanced sap flux density (Js) and canopy stomatal conductance (Gc) of C. lanceolata during growing season. However, N1 and N2 treatments exerted minimal impacts on Js and Gc, suggesting there existed a dose-response relationship between external N input amount and Js (or Gc). Moreover, high-level N addition enhanced the sensitivity of Js and Gc to vapor pressure deficit and photosynthetically active radiation. Overall, C. lanceolata are more likely to enhance resource acquisition ability, and exhibit higher water consumption under future scenarios of increased nitrogen deposition.

In the context of global warming and increasing drought, clarifying intraspecific variation in plant xylem hydraulic traits and their ecological adaptation strategies is crucial for predicting vegetation stability and functional maintenance in arid ecosystems. This study investigated Reaumuria songarica, a widely distributed and highly drought-tolerant shrub native to the desert regions of northwestern China. By integrating quantitative anatomical analyses of xylem vessels and inter-vessel pits with trait network modelling, we systematically assessed the variation patterns and environmental responses of its hydraulic structural traits along an aridity gradient. The results demonstrated that: (1) R. songarica exhibits substantial intraspecific variation in hydraulic traits, with individuals in hyper-arid regions possessing larger pit aperture areas and higher pit densities, indicative of an "opportunistic" water-use strategy that facilitates rapid responses to episodic rainfall events; (2) different traits exhibited distinct responses to temperature, precipitation, and soil conditions, with tissue-level traits being more responsive to temperature, while pit-level traits were primarily influenced by precipitation and soil factors; (3) vessels and pits displayed significant coordinated variation at the anatomical level. Trait network analysis further revealed that the topological structure of hydraulic traits was substantially reorganized along the aridity gradient, transitioning from a highly coordinated strategy centered on embolism resistance in arid regions to a structure-stabilization strategy centered on vessel wall thickness in hyper-arid regions. This study provides clear evidence of intraspecific variation in pit structure in R. songarica and uncovers the coordinated regulatory mechanism between pit and vessel structures. These findings offer microstructural insights into hydraulic adaptation strategies in desert plants and contribute theoretical support for drought-tolerant shrub selection and ecological restoration in arid regions.

Excessive mistletoe proliferation is considered dangerous for the survival of the host stands, as mistletoe increases their sensitivity to drought stress. To better understand this sensitivity, we aimed to explore in depth the hydraulic and gas exchange performance of Viscum album relative to its host, Pinus sylvestris, during summer drought, by integrating a more comprehensive and detailed dataset. We measured hydraulic traits, xylem embolism, water potential, gas exchange, plant conductance and branch transpiration in non-infected pine branches, infected pine branches, and in the mistletoe itself. We concluded that 1) although the two species exhibited similar xylem- and leaf-specific hydraulic conductivity, vulnerability to drought-induced embolism, and plant conductance, V. album displayed higher transpiration rates, resulting in more negative stem water potentials, which indicate a reduced hydraulic safety margin and, consequently, a potentially greater risk of xylem dysfunction; 2) the higher stomatal conductance of V. album may enhance its ability to uptake CO2, compensating for its lower mesophyll conductance and biochemical rates; 3) infected pine branches adjusted stem conductivity to the supported leaf area, that could explain the lack of differences in leaf specific conductivity, gas exchange, water potential and branch conductance with non-infected pine branches; and 4) despite the pine hydraulic adjustment, V. album caused a water uncoupling effect, i.e. a lack of coordination between pine xylem conductivity and branch transpiration, in infected pine branches where mistletoe leaf area exceeds approximately 46% of the total leaf area of the branch; under soil water deficit, this value dropped to around 11%. These findings highlight that mistletoe-induced hydraulic uncoupling compromises the host's water balance, especially under soil drought, potentially accelerating tree decline in dry environments.

Rainfall pulses create brief but critical opportunities for carbon uptake in seasonally dry forests; however, how tree seedlings recover photosynthetic function during the establishment phase following these short-lived rewetting events under field conditions remains poorly understood. In particular, the coordination and timing of hydraulic, stomatal, and biochemical recovery processes during natural rainfall pulse-dry-down cycles are not well quantified, despite their importance for carbon-water coupling and drought resilience. Here, we investigated short-term physiological responses of establishing Eucalyptus seedlings during naturally occurring rainfall pulse-dry-down cycles. We measured leaf water potential (Ψleaf), gas exchange, and photosynthetic capacity (Vcmax, Jmax) before and after rainfall to assess recovery dynamics of diffusional and biochemical processes under contrasting atmospheric demand. Across species, Ψleaf and stomatal conductance improved rapidly following rainfall, reflecting transient hydraulic relief, while net photosynthesis increased by 40-60% within 1-3 days. In contrast, biochemical capacity responded more gradually: Vcmax declined by up to ~15% and Jmax by 20-40% during dry-down and showed limited or partial recovery after rewetting. Limitation partitioning revealed asynchronous recovery, with stomatal limitation relaxing rapidly after rainfall under low vapour pressure deficit (VPD), whereas under high VPD, biochemical recovery preceded full stomatal reopening. The xeric-origin E. cladocalyx sustained assimilation at more negative Ψleaf and exhibited greater biochemical stability, whereas intermediate and mesic species (E. grandis, E. urophylla, E. cloeziana) showed rapid but short-lived post-rain responses. Together, these results demonstrate that photosynthetic recovery during the seedling phase is asynchronous and strongly modulated by atmospheric demand, shaping short-term carbon-water coupling under increasingly pulsed hydroclimates.

Plant adaptation strategies to environmental variability encompass not only climatic factors but also the underlying subsurface structure, which are critical for the sustainability of vegetation restoration. However, the plant water use traits and their relationships across varying soil-rock structure settings for common species remain unclear, undermining the reliability of adaptation assessments in heterogeneous habitats. Current study examined five common tree species from two different bedrock types-limestone and dolomite-within Southwest China. Key plant water use traits, including root water sources, xylem hydraulic traits (P50 and wood density), and leaf stable isotope (δ18O and δ13C) as proxies for stomatal regulation and water use efficiency, were measured. Results revealed that the predominant root water uptake depths of all five species was significantly deeper in the limestone site (P<0.05), with its discontinuous, deep-pocket soil, compared to the dolomite site, where the continuous, thinner soil layer predominated. Besides, species in limestone site exhibited significantly less negative P50, lower wood density and leaf δ18O, more negative δ13C values compared to those in dolomite (P<0.05). The study also identified significant trade-offs between root water uptake patterns, xylem hydraulic traits and leaf isotopic composition (P<0.05). These relationships elucidate two contrasting adaptive strategies: an acquisition strategy with high hydraulic efficiency and carbon demands, supported by a deep and stable water supply in limestone site, and a conservative with high hydraulic safety and strict stomatal response, constrained by a fluctuating shallow water source in dolomite. Our findings underscore the profound influence of lithology on plant water use traits and highlight how the trade-off of root and xylem-leaf traits improves the adaptation assessments in such fragile, heterogenous environments.