Tree physiology最新文献

Water uptake depth is often coordinated with leaf morphology, nutrient and water-use traits across dryland plant species, but such trait coordination remains largely unexplored in plants from more humid but nutrient-poor habitats. We assessed how the year-round water uptake pattern influences the leaf economics spectrum (LES) and isotopic water-use traits across five representative native tree species inhabiting limestone soils and sandstone-derived yellow soils in humid subtropical SW China. We used xylem water isotopes (δ18O, δ2H) to infer water uptake depth; leaf δ13C and Δ18O as proxies for time-integrated water-use efficiency and stomatal conductance, respectively; and key LES traits (specific leaf area, Nmass and Narea) as indices of carbon-nutrient economy. Soil water uptake depth strongly influenced the inter-specific variations in leaf economic and water-use traits, especially during the dry winter-spring period. Shallow-rooted species using water stored in fertile topsoil layers exhibited lower carbon investment per leaf area, higher leaf N and water contents, and higher δ13C values. Conversely, deep-rooted species using deeper soil/bedrock water exhibited thicker and more sclerophyllous leaves combined with lower leaf N, water contents and δ13C values. Across species, leaf δ13C increased with N content, revealing that N-induced differences in photosynthetic capacity are the dominant control over interspecific variation in intrinsic water-use efficiency. Shallow-rooted species exhibited lower foliar Δ18O values (indicative of looser stomatal regulation and water-spender strategy), potentially facilitating nutrient uptake from fertile topsoil. Specifically, Zanthoxylum bungeanum played a central role in shaping the broad water-spender-to-water-saver continuum observed across the target species. Our findings highlight how shallow-rooted tree species can adopt a resource-acquisitive strategy through coupled enhancement of soil water and nutrient capture, stomatal conductance, photosynthetic capacity and water-use efficiency. We provide novel insights into key ecophysiological mechanisms that may help maintain tree species diversity and coexistence in humid but nutrient-poor subtropical habitats.

Cadmium (Cd) contamination has pronounced negative effects on plant physiological processes, while phosphorus (P) as an essential macronutrient might mitigate Cd toxicity by modulating plant adaptivity. This study employed Salix caprea as a model to assess the effects of P on physiological and anatomical characteristics under Cd stress. The results demonstrated that plant growth, e.g., height, basal diameter and biomass, photosynthetic pigment content and net photosynthetic rate were all significantly inhibited by Cd stress. However, adequate P could alleviate these inhibitory effects in contrast to the P deficiency treatment under Cd stress. Phosphorus sufficiency significantly reduced the levels of reactive oxygen species (O₂˙- and H₂O₂) and malondialdehyde (MDA) in roots under Cd stress, while enhancing the activities of antioxidant enzymes such as superoxide dismutase and ascorbate peroxidase, and increasing the contents of non-enzymatic antioxidants, including ascorbic acid and glutathione. These findings indicate that P reduces Cd-induced oxidative damage by adjusting the antioxidant defense system. Furthermore, P sufficiency enhanced the accumulation of phytochelatins and non-protein thiols in roots, thereby promoting complexation and sequestration of Cd into vacuoles. Adequate P enhanced root mineral uptake, which resulted in higher concentrations of magnesium and manganese in roots. Anatomical analysis revealed that P sufficiency significantly increased the stele-to-root area ratio, thereby enhancing transport efficiency and promoting Cd accumulation in aboveground tissues. Moreover, adequate P significantly increased the levels of abscisic acid, indole-3-acetic acid and gibberellic acid under Cd stress, suggesting a mediated role of hormones in the improved tolerance capacity to Cd by P. In summary, P sufficiency conditions enhanced Cd tolerance in S. caprea by coordinating antioxidant defense, metal chelation, root development and hormonal regulation.

Pine wilt disease, instigated by the Bursaphelenchus xylophilus (also called pine wood nematode [PWN]), poses a significant threat to coniferous forests across the globe, leading to widespread tree mortality and ecological disruption. While Japanese larch (Larix kaempferi) is a natural host of PWN, the molecular basis of its responses remains poorly understood. Here, we developed a callus-based parenchymal sentinel (CaPS) system mimicking xylem parenchyma-nematode interactions to bypass multi-tissue interference in traditional sapling studies. After 5 days of PWN inoculation, nematode proliferated 2.85-fold, while the callus exhibited water-soaked lesions and reduced cell viability, indicating a rapid defense activation. (i) Transcriptome analysis revealed 8515 differentially expressed genes related to chitinase signaling, calcium-regulated immunity and antimicrobial compound synthesis. (ii) Metabolomic analysis identified 389 defense-related metabolites (e.g., alkaloids). (iii) Integration of omics data uncovered 71 coordinated pathways categorized into eight functional groups, including reactive oxygen species burst and mitogen-activated protein kinase, and they formed a multi-layered defense network. Importantly, this CaPS system enabled 5-day phenotyping cycles of transgenic callus, significantly accelerating evaluation compared with traditional sapling methods. Our work reveals early-stage conifer immunity against PWN and establishes an accelerated evaluation program for future screening of transgenic callus and breeding resistant larch varieties.

Secondary forests (SFs), which dominate tropical regions and account for more than half of the total forest area, play a crucial role as carbon sinks and contribute significantly to climate change mitigation. However, our understanding of how species respond to ongoing climate change in these forests remains limited, particularly because species performance may shift across successional stages in response to changing environmental filters. Therefore, understanding the factors that influence species regeneration and drought tolerance is essential for predicting their resilience in the face of intensifying climate change. In this study, we evaluated intraspecific variation in hydraulic and anatomical traits of three abundant tree species (Eschweilera coriacea, Licania kunthiana and Tapirira guianensis) occurring in a successional gradient of SFs in the Eastern Amazon and their relationships with soil characteristics. We identified intraspecific variation both among individuals within the same plot and across different plots; however, we did not observe a consistent pattern of trait variation along the successional gradient. In some cases, successional age was associated with variation in anatomical and hydraulic traits, but these relationships were not consistent across species. In addition, soil properties were a key determinant of intraspecific variation. Our findings highlight the complexity of intraspecific trait responses in SFs and underscore the need to consider both species-specific strategies and environmental drivers when predicting forest resilience under future climate change.

Foliar water uptake (FWU) capacity of more anisohydric species is significantly higher than that of relatively isohydric species, yet the underlying mechanisms remain unclear. While leaf nutrient elements may modulate the FWU process, this relationship remains understudied. In this study, we investigated four typical species from the arid region of northwest China and measured their FWU parameters along with various associated traits. The results showed obvious differences in FWU capacity and traits along the isohydric-anisohydric continuum, with more anisohydric species exhibiting higher FWU capacity. Structural equation modeling revealed that leaf water storage structures were the primary factor contributing to the high FWU capacity in more anisohydric species (total effect = 0.25), followed by epidermal traits (total effect = 0.18). Leaf phosphorus affected FWU indirectly via leaf water storage structures (standardized path coefficient = 0.35). This study reveals key drivers and mechanisms underlying the FWU capacity of more anisohydric species, providing a theoretical framework for plant water-use strategies in arid environments. It also helps to predict the water adaptation strategies of different plant functional types under future climate change scenarios.

Leaf nutrient resorption represents a vital nutrient conservation strategy for plants. While trace element resorption patterns have been extensively studied in upland terrestrial plants, they remain poorly characterized in mangrove ecosystems. This study investigated the nutrient resorption efficiency (NuRE) of seven trace elements-iron (Fe), manganese (Mn), copper (Cu), zinc (Zn), boron (B), sodium (Na) and aluminum (Al)-in mangroves, comparing them with upland terrestrial plants and evaluating their ecological implications under seasonally dry and wet conditions. Field sampling was conducted in Dongzhaigang National Nature Reserve, China, across dry and wet seasons, and green and senesced leaves from 10 mangrove species were analyzed. Our findings revealed distinct resorption strategies between mangroves and upland terrestrial plants. Compared with upland terrestrial species, mangroves presented net accumulation (negative NuRE) of Na (-29.06 ± 6.87%), Mn (-72.71 ± 11.79%), B (-77.36 ± 14.49%), Fe (-123.63 ± 17.98%) and Al (-164.91 ± 33.21%), demonstrating significantly lower NuRE values for these elements. In contrast, mangroves presented a greater NuRE for Cu (57.80 ± 3.50%) than their upland terrestrial counterparts did, whereas Zn resorption (17.39 ± 4.00%) did not differ significantly between the two systems. Our analysis revealed that Na resorption patterns exhibited strong seasonal variations across ecological gradients. During dry seasons, Na accumulation (more negative NaRE) was significantly greater in low intertidal zones, tree species and isobilateral leaves (characterized by symmetrical mesophyll organization). In contrast, wet seasons completely reversed these patterns, favoring accumulation in high intertidal zones, shrubs and bifacial leaves (with dorsiventral mesophyll organization). Green-leaf nutrient concentrations emerged as the primary driver of NuRE, outweighing soil nutrient availability across dry and wet seasons. These findings highlight mangroves' unique nutrient conservation strategies and underscore the importance of foliar nutrient status in predicting ecosystem resilience under seasonal hydroclimatic variations.

More frequent and extreme droughts under global climate change pose major threats to plant diversity and ecosystem productivity. Plant growth is constrained by the interplay between hydraulic failure and reduced carbon assimilation; however, how these carbon-water dynamics jointly regulate growth across functional types, particularly under varying drought intensity and duration, remains poorly understood. We conducted a meta-analysis of 249 studies covering 236 species across diverse biomes to examine differences in growth, carbohydrate allocation and hydraulic responses to drought among functional groups (e.g. evergreen vs deciduous, angiosperm vs gymnosperm, adult plants vs seedling, etc.). We also evaluated how carbon-water dynamics mediate plant growth under drought stress. We found that drought stress consistently reduced plant growth, photosynthetic rate, water potentials and the consequent hydraulic conductivity across species. Growth responses were strongly influenced by leaf phenology (evergreen vs deciduous) and drought intensity. Evergreen species showed greater growth resistance to drought than deciduous species, by maintaining photosynthesis and hydraulic function despite faster declines in water potential. Evergreen species exhibited linear reductions in growth, photosynthesis and water potentials with increasing drought intensity, reflecting gradual physiological adjustments indicative of drought resistance. In contrast, deciduous species showed significant limitation of photosynthesis and growth at drought onset. Our findings provide a quantitative framework linking plant traits related to carbohydrates and hydraulic to growth responses under drought. Understanding how drought affects carbon-water strategy based on leaf phenology advances predictive vegetation models of responses to climate extremes, with critical implications for ecosystem management and maintaining species diversity under global change scenarios.

Climate change-induced shifts in plant phenology have substantially impacted terrestrial ecosystem structure and function. While the effects of drought and heatwaves on leaf senescence have been studied, the response of leaf senescence to compound drought and heatwave events remains poorly understood, especially due to a lack of experimental evidence. In this study, we investigated the responses of leaf senescence to varying durations (13, 28, and 43 days) of compound drought and heatwave stress in saplings of three temperate deciduous tree species. We found that prolonged drought and heatwave conditions delayed leaf senescence by 20.2 in Koelreuteria paniculata and 22.4 days Hibiscus syriacus, respectively, potentially as a compensation for stress-induced reductions in growth. However, leaf senescence in the lowly tolerant Acer palmatum shifted from delayed to advanced, indicating a nonlinear response. Total photosynthesis, relative height increment, and basal diameter growth decreased in all three species, with the strongest reductions in Acer palmatum, followed by Hibiscus syriacus and Koelreuteria paniculata. Our findings demonstrate delayed effects of environmental stress on leaf senescence and highlight species-specific variation in response to compound drought-heatwave events, providing insights into how plants respond to climate change.

The phenology and lifespan of fine roots influence plant resource acquisition and fine-root carbon fluxes into soil, yet the extent to which fine-root phenology and lifespan vary across species and plant functional types, as well as the underlying drivers of this variation, remain poorly understood. We observed fine-root lifespan, production and mortality dynamics in 11 temperate forest species for two consecutive years using minirhizotrons, and measured leaf lifespan (LL). We tested the influence of environmental factors on fine-root dynamics and determined whether traits affecting lifespan differed among leaves and roots. Peak fine-root production mainly occurred in early summer followed by the peak of fine-root mortality, occurring mainly in late summer. The median fine-root lifespan (MRL) was negatively and positively associated with root nitrogen concentration and root diameter, respectively. In contrast, the best predictors of LL were leaf tissue density and specific leaf area. The MRL and LL were not related. Our results highlight that, although leaves and fine roots were partly influenced by the same trade-off between high metabolism and long lifespan, MRL is largely noncoordinated with LL, suggesting temporally decoupled ecological strategies above and belowground for maintaining functional resource-acquisition organs. Furthermore, species-specific patterns of root production suggest variable strategies among species to enhance resource acquisition. Such differences also imply variable influences of species on carbon dynamics in temperate forests.

Leaves constitute a vital bottleneck in whole-plant water transport, and their water strategies are key determinants of plant competition and productivity. Nonetheless, our knowledge of leaf water strategies predominantly stems from single perspectives (i.e., hydraulic, stomatal or economic traits), severely limiting our capacity to comprehensively predict plant vulnerability and sustainability, especially under drought-stress conditions. Here, we examined the leaf hydraulic, stomatal and economic traits of three coexisting shrub species (i.e., Haloxylon ammodendron (C.A. Mey.) Bunge., Calligonum mongolicum Turcz. and Nitraria sphaerocarpa Maxim.) in the Badain Jaran desert-oasis ecotone to comprehensively evaluate their water strategies and drought adaptation mechanisms. The results demonstrated that these three shrubs exhibited significant differences in leaf hydraulic vulnerability, osmoregulatory capacity, stomatal behavior and economic traits. Nonetheless, these traits remain tightly related to guarantee their survival. Interestingly, two distinct interaction mechanisms between stomatal and hydraulic regulation were identified among the three shrubs with varying stomatal sensitivity. Specifically, N. sphaerocarpa and H. ammodendron employed relatively lower isohydric stomatal behavior, characterized by a synergistic decrease in vapor-phase water loss as liquid-phase water transport decreased during severe atmospheric drought. Conversely, C. mongolicum adopted higher isohydric stomatal behavior, rapidly reducing vapor-phase water loss during initial drought stress to compensate for its more vulnerable liquid-phase water transport system. Notably, all three shrubs presented risky leaf water strategies with negative hydraulic safety margins. Among them, the hydraulic dysfunction risk was lowest for C. mongolicum, followed by N. sphaerocarpa and H. ammodendron. Overall, our findings are anticipated to offer valuable insights for afforestation initiatives and ecological conservation efforts in desert-oasis ecotones that function as critical shelterbelts.