Tree physiology最新文献

None declared.Conflict of interestSoil salinization has become a global problem and high salt concentration in soil negatively affects plant growth. In our previous study, we found that overexpression of PsAMT1.2 from Populus simonii could improve the salt tolerance of poplar, but the physiological and molecular mechanism was not well understood. To explore the regulation pathway of PsAMT1.2 in salt tolerance, we investigated the morphological, physiological, and transcriptome differences between the PsAMT1.2 overexpression transgenic poplar and the wild type (WT) under salt stress. The PsAMT1.2 overexpression transgenic poplar showed better growth with increased net photosynthetic rate and higher chlorophyll content compared with WT under salt stress. The overexpression of PsAMT1.2 increased the catalase, superoxide dismutase, peroxidase, ascorbate peroxidase activities and therefore probably enhanced the reactive oxygen species clearance ability, which also reduced the degree of membrane lipid peroxidation under salt stress. Meanwhile, the PsAMT1.2 overexpression transgenic poplar maintained a relatively high K+/Na+ ratio under salt stress. RNA-seq analysis indicated that PsAMT1.2 might improve plant salt tolerance by regulating pathways related to the photosynthetic system, chloroplast structure, antioxidant activity, and anion transport. Among the 1056 differentially expressed genes, genes related to photosystemIand photosystemIIwere up-regulated and genes related to chloride channel protein-related were down-regulated. The result of the present study would provide new insight into regulation mechanism of PsAMT1.2 in improving salt tolerance of poplar.

Climate change is raising concerns about how forests will respond to extreme droughts, heat waves and their co-occurrence. In this greenhouse study, we tested how carbon and water relations relate to seedling growth and mortality of northeastern US trees during and after extreme drought, warming, and combined drought and warming. We compared the response of our focal species red spruce (Picea rubens Sarg.) with a common associate (paper birch, Betula papyrifera Marsh.) and a species expected to increase abundance in this region with climate change (northern red oak, Quercus rubra L.). We tracked growth and mortality, photosynthesis and water use of 216 seedlings of these species through a treatment and a recovery year. Each red spruce seedling was planted in containers either alone or with another seedling to simulate potential competition, and the seedlings were exposed to combinations of drought (irrigated, 15-d 'short' or 30-d 'long') and temperature (ambient or 16 days at +3.5 °C daily maximum) treatments. We found dominant effects of the drought reducing photosynthesis, midday water potential, and growth of spruce and birch, but that oak showed considerable resistance to drought stress. The effects of planting seedlings together were moderate and likely due to competition for limited water. Despite high temperatures reducing photosynthesis for all species, the warming imposed in this study minorly impacted growth only for oak in the recovery year. Overall, we found that the diverse water-use strategies employed by the species in our study related to their growth and recovery following drought stress. This study provides physiological evidence to support the prediction that native species to this region like red spruce and paper birch are susceptible to future climate extremes that may favor other species like northern red oak, leading to potential impacts on tree community dynamics under climate change.

Dormancy in temperate fruit trees is a mechanism of temporary growth suspension, which is vital for tree survival during winter. Studies on this phenomenon frequently employ scientific methods that aim to detect the timing of dormancy release. Dormancy release occurs when trees have been exposed to sufficient chill, allowing them to resume growth under conducive conditions. This study investigates dormancy dynamics in two apple (Malus × domestica Borkh.) cultivars, 'Nicoter' and 'Topaz', by sampling branches in an orchard over 14 weeks (2019-2020) and over 31 weeks (2021-2022) and subjecting them to a 42-day budbreak forcing period in a growth chamber. Temporal changes in budbreak percentages demonstrated dormancy progression in the studied apple cultivars and allowed distinguishing the three main dormancy phases: paradormancy (summer dormancy), endodormancy (deep dormancy), and ecodormancy (spring dormancy), along with transition periods between them. Using these data, we explored the suitability of several alternative methods to determine endodormancy release. Tabuenca's test, which predicts dormancy release based on the differences in dry weights of buds with and without forcing, showed promise for this purpose. However, our data indicated a need for considerable adjustments and validation of this test. Bud weight and water content of buds in the orchard did not align with budbreak percentages under forcing conditions, rendering them unsuitable for determining endodormancy release in 'Nicoter' and 'Topaz'. Shoot growth cessation did not seem to be connected with either dormancy progression or dormancy depth of the studied cultivars, whereas leaf fall coincided with the beginning of the transition from endo- to ecodormancy. This work addresses methodological limitations in dormancy research and suggests considering the mean time to budbreak and budbreak synchrony as additional criteria to assess tree dormancy status.

Seasonality in temperate regions is prominent during the era of increased climatic variability. A hydraulic trait that can adjust to seasonally changing climatic conditions is crucial for tree safety. However, little attention has been paid to the intraspecific seasonality of drought-related traits and hydraulic safety of keystone forest trees. We examined seasonal variations in the key morphological and physiological traits as well as multiple hydraulic safety margins (SMs) at the branch and leaf levels in oriental cork oak (Quercus variabilis Bl.), which is predominant in Chinese temperate forests. Pneumatic measurements indicated that, as seasons progressed, the water potential at which 50% of branch embolisms occur (P50_branch) decreased from -3.34 MPa to -4.23 MPa, with a coefficient of variation (CV) of 9.08%. Sapwood capacitance ranged from 48.19-248.08 kg m-3 MPa-1, peaking in autumn and reaching minimum in winter (CV 60.58%). Rehydration kinetics confirmed higher leaf embolism vulnerability (P50_leaf) in spring and autumn than those in summer, with values ranging from -1.06 MPa to -3.02 MPa (CV 39.85%). All leaf pressure-volume (PV) traits shifted with growth, with CVs ranging from 6.95-46.69%. Sapwood density had significant negative correlations with P50_branch and hydraulic capacitance for elastic water storage, whereas leaf mass per area was linearly associated with PV traits but not with P50_leaf. Furthermore, the branch typical SMs (difference between branch midday water potential and P50_branch) were consistently > 1.84 MPa, and vulnerability segmentation was prevalent throughout, implying a plausible hydraulic foundation for the dominance of Q. variabilis. Diverse hydraulic response patterns existed across seasons, leading to positive safety margins mediated by the aforementioned physiological traits. Although Q. variabilis exhibits a high level of hydraulic safety, its susceptibility to sudden summer droughts may increase due to global climate change.

Atmospheric nitrogen (N) deposition has notably increased since the industrial revolution, doubling N inputs to terrestrial ecosystems. This could mitigate N limitations in forests, potentially enhancing productivity and carbon sequestration. However, excessive N can lead to forest N saturation, causing issues like soil acidification, nutrient imbalances, biodiversity loss, increased tree mortality, and a potential net greenhouse gas emission. Traditional experiments often overlook the canopy's role in N fate, focusing instead on direct N addition to the forest floor. In our study, we applied 20 kg N ha y-1 of labeled 15NH415NO3 solution (δ15N = 30 ‰) both above and below the canopy, maintaining also control plots. We assessed ecosystem components before and after treatment, calculated N stocks, and used mass balance for fertilizer recovery analysis. Findings revealed that the above-canopy N addition intercepted up to 31 ± 4% of added N in foliage, a significant contrast to the negligible recovery in leaves with below-canopy treatment. Overall plant recovery was higher in the above-canopy treatment (43 ± 11%) compared to below (9 ± 24%). Post-vegetative season, about 15 ± 1% of above-canopy added N was transferred to soil via litterfall, indicating substantial N reabsorption or loss through volatilization, stemflow, or throughfall. In contrast, the below-canopy approach resulted in just 4.0 ± 0.6% recovery via litterfall. These results highlight a significant difference in N fate based on the application method. N applied to the canopy showed distinct recovery in transient compartments like foliage. However, over a few months, there was no noticeable change in N recovery in long-lived tissues across treatments. This implies that N application strategy does not significantly alter the distribution of simulated wet N deposition in high C/N tissues, underscoring the complex dynamics of forest N cycling.

Given the pressing challenges posed by climate change, it is crucial to develop a deeper understanding of the impacts of escalating drought and heat stress on terrestrial ecosystems and the vital services they offer. Soil and plant water potential play a pivotal role in governing the dynamics of water within ecosystems and exert direct control over plant function and mortality risk during periods of ecological stress. However, existing observations of water potential suffer from significant limitations, including their sporadic and discontinuous nature, inconsistent representation of relevant spatio-temporal scales, and numerous methodological challenges. These limitations hinder the comprehensive and synthetic research needed to enhance our conceptual understanding and predictive models of plant function and survival under limited moisture availability. In this article, we present PSInet (PSI-for the Greek letter Ψ used to denote water potential), a novel collaborative network of researchers and data, designed to bridge the current critical information gap in water potential data. The primary objectives of PSInet are: (1) Establishing the first openly accessible global database for time series of plant and soil water potential measurements, while providing important linkages with other relevant observation networks. (2) Fostering an inclusive and diverse collaborative environment for all scientists studying water potential in various stages of their careers. (3) Standardizing methodologies, processing, and interpretation of water potential data through the engagement of a global community of scientists, facilitated by the dissemination of standardized protocols, best practices, and early career training opportunities. (4) Facilitating the use of the PSInet database for synthesizing knowledge and addressing prominent gaps in our understanding of plants' physiological responses to various environmental stressors. The PSInet initiative is integral to meeting the fundamental research challenge of discerning which plant species will thrive and which will be vulnerable in a world undergoing rapid warming and increasing aridification.

Yellowhorn (Xanthoceras sorbifolium) is an economically-important tree species in northern China, mainly distributed in arid and semi-arid areas where water resources are scarce. Drought affects its yield and the expansion of its suitable growth area. It was found that the wax content in yellowhorn leaves varied significantly among different germplasms, which had a strong correlation with the drought resistance of yellowhorn. In this study, XsMYB30 was isolated from 'Zhongshi 4' of yellowhorn, a new highly waxy variety. DAP-Seq technology revealed that the pathways associated with fatty acids were significantly enriched in the target genes of XsMYB30. Moreover, the results of the electrophoretic mobility shift assay, the yeast one hybrid assay and the dual-luciferase assay demonstrated that XsMYB30 could directly and $$bind with the promoters of genes involved in wax biosynthesis (XsFAR4, XsCER1, and XsKCS1), lipid transfer (XsLTPG1 and XsLTP1) and fatty acid synthesis (XsKASIII), thus enhancing their expression. In addition, the overexpression of XsMYB30 in poplar promoted the expression levels of these target genes, and increased the wax deposition on poplar leaves leading to a notable improvement in the plant's ability to withstand drought. These findings indicate that XsMYB30 is an important regulatory factor in cuticular wax biosynthesis and the drought resistance of yellowhorn.

Understanding covariation patterns of drought resistance, post-drought recovery and phenotypic plasticity, and its variability at the intra-population level is crucial for predicting forest vulnerability to increasing aridity. This knowledge is particularly urgent at the trailing range edge since, in these areas, tree species are proximal to their ecological niche boundaries. While this proximity increases their susceptibility, these populations are recognized as valuable genetic reservoirs against environmental stressors. The conservation of this genetic variability is critical for the adaptive capacity of the species in the current context of climate change. Here we examined intra-population patterns of stem basal growth, gas exchange and other leaf functional traits in response to an experimental drought in seedlings of 16 open-pollinated families within a marginal population of European beech (Fagus sylvatica L.) from its southern range edge. We found high degree of intra-population variation in leaf functional traits, photosynthetic performance, growth patterns and phenotypic plasticity in response to water availability. Low phenotypic plasticity was associated with higher resistance to drought. Both drought resistance and post-drought recovery of photosynthetic performance varied between maternal lines. However, drought resistance and post-drought recovery exhibited independent variation. We also found intra-population variation in stomatal sensitivity to soil drying but it was not associated with either drought resistance or post-drought recovery. We conclude that an inverse relationship between phenotypic plasticity and drought resistance is not necessarily a sign of maladaptive plasticity but rather it may reflect stability of functional performance and hence adaptation to withstand drought. The independent variation found between drought resistance and post-drought recovery should facilitate to some extend microevolution and adaption to increasing aridity. The observed variability in stomatal sensitivity to soil drying was consistent with previous findings at other scales (e.g., inter-specific variation, inter-population variation) that challenge the iso-anisohydric concept as a reliable surrogate of drought tolerance.

Mistletoes are xylem-tapping hemiparasites that rely on their hosts for water and nutrient uptake. Thus, they impair tree performance in the face of environmental stress via altering carbon and water relations and nutritional status of trees. To improve our understanding of physiological responses to mistletoe and ongoing climate change, we investigated radial growth, stable C and O isotopic signals and elemental composition of tree rings in silver fir (Abies alba) and Scots pine (Pinus sylvestris) forests infested with Viscum album. We compared temporal series (1990-2020) of basal area increment (BAI), intrinsic water-use efficiency (iWUE), oxygen isotope composition (δ18O) and nutrient concentrations and stoichiometric ratios between non-infested (NI) and severely infested (SI) fir and pine trees from populations located close to the xeric distribution limit of the species in north-eastern Spain. SI trees showed historically higher growth, but the BAI trend was negative for more than three decades before 2020 and their growth rates became significantly lower than those of NI trees by the mid-2010s. Mistletoe infestation was related to an enhanced sensitivity of radial growth to vapour pressure deficit (atmospheric drought). SI trees showed less pronounced iWUE increases (fir) and lower iWUE values (pine) than NI trees. The lower tree-ring δ18O values of SI trees may be the result of several superimposed effects operating simultaneously, including leaf-level evaporative enrichment, source water isotopic signals, and anatomical and phenological differences. We observed a deterioration of potassium (K) nutrition in tree-ring wood of both species in SI trees, along with accumulation of manganese (Mn). We suggest that such nutritional patterns are driven by the indirect effect of mistletoe-induced drought stress, particularly in pine. The combined analyses of different physiological indicators imprinted on tree rings provided evidence of the progressive onset of carbon, water and nutrient imbalances in mistletoe-infested conifers inhabiting seasonally dry regions.

Drought is a significant global issue affecting agricultural production, and the utilization of beneficial rhizosphere microorganisms is one of the effective ways to increase the productivity of crops and forest under drought. In this study, we characterized a novel growth-promoting dark septate endophytes (DSE) fungus R16 derived from the blueberry roots. Hyphae or microsclerotia were visible within the epidermal or cortical cells of R16-colonized blueberry roots, which was consistent with the typical characteristics of DSE fungi. Inoculation with R16 promoted the growth of blueberry seedlings and the advantage over the control group was more significant under PEG-induced drought. Comparison of physiological indicators related to drought resistance between the inoculated and control groups was performed on the potted blueberry plants, including the chlorophyll content, net photosynthetic rate, root activities, MDA and H2O2 content, which indicated that R16 colonization mitigated drought injury in blueberry plants. We further analyzed the effects of R16 on phytohormones and non-structural carbohydrates (NSCs) to explore the mechanism of increased drought tolerance by R16 in blueberry seedlings. The results showed that except for the GA content, IAA, ZT and ABA varied significantly between the inoculated and control groups. SPS and S6PDH activities in mature leaves, the key enzymes responsible for sucrose and sorbitol synthesis, respectively, as well as SDH, SuSy, CWINV, HXK and FRK in roots, the key enzymes involved in the NSCs metabolism, showed significant differences between the inoculated and control groups before and after drought treatment. These results suggested that the positive effects of R16 colonization on the drought tolerance of blueberry seedlings are partially attributable to the regulation of phytohormone and sugar metabolism. This study provided valuable information for the research on the interaction between DSE fungi and host plants as well as the application of DSE preparations in agriculture.