Tree physiology最新文献

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.

Mango (Mangifera indica L.), a leading tropical fruit crop, is a prime candidate for intensification through modern orchard-management techniques, including canopy manipulation to improve light interception. This study investigated how leaf-level acclimation to light gradients within the canopy of a high-yield, dwarfing mango cultivar (Calypso™) could be used to examine integrated canopy-scale responses. We quantified foliar morphological, biochemical and physiological traits across a range of canopy positions using this information to model canopy-scale productivity within digital-twin representations of mango under both conventional (i.e., open-vase) and espalier-trellis training canopy systems. Key findings demonstrated that leaves exposed to higher light exhibited increased leaf mass per unit area, nitrogen content and photosynthetic capacity (Asat), but decreased chlorophyll-to-nitrogen ratios and photochemical reflectance indices, reflecting trade-offs between light capture and photoprotection. Phenolic content increased under high irradiance, indicating investment in photoprotective compounds at the expense of net carbon gain. Modelled leaf-level productivity increased with light availability, following a Michaelis-Menten saturating response, with diminishing returns under high light. Digital modelling of canopy light interception revealed that espalier-trellis training enhanced light distribution efficiency per unit leaf area but resulted in a 6.5% reduction in total canopy productivity due to a smaller total canopy leaf area. However, when normalized by total canopy leaf area, the espalier-trellis system showed a 3.6% productivity advantage over conventional canopies at the time of year modelled. These results highlight the role of canopy structure and light-use efficiency in determining orchard productivity. Integrating spatially explicit mechanistic models with LiDAR-derived canopy data offers a promising pathway for designing high-density, resource-efficient mango orchards. Future work should expand modelling to account for dynamic canopy shape throughout the growing season and evaluate the interaction of modified canopy structures with environmental stressors, particularly under climate variability.

LBD transcription factors play pivotal roles in regulating adventitious root formation in plants, with two key LBD genes, SBRL and BSBRL, constituting the highly conserved superlocus first reported in tomato. However, the members of LBD genes regulating adventitious root formation in peach trees have not yet been identified, and the regulatory mechanisms of the two key LBD genes remain to be elucidated. In this study, through genome-wide analysis of the LBD gene family in peach, we identified nine LBD genes clustered with these reported adventitious root-related LBDs, but only three superlocus-associated LBD genes (PpBSBRL, PpSBRL1 and PpSBRL2) revealed significant upregulation in expression level during the induction phase of peach adventitious rooting. Functional analysis demonstrated that PpBSBRL, PpSBRL1 and PpSBRL2 positively regulate both lateral and adventitious root formation in peach seedlings. Further investigation established a direct interaction between PpBSBRL and PpSBRL2. Notably, PpBSBRL specifically binds to the promoter region of PpSBRL2 (-1021 ~ -516 bp) and transcriptionally activates its expression. This study provides the first evidence of a regulatory mechanism between PpBSBRL and PpSBRL2 during adventitious root development, offering theoretical insights to address the challenge of poor rooting capacity in peach cuttings.

Pine wilt disease, caused by the pine wood nematode (PWN), is a devastating systemic disease with significantly impacts on pine species, particularly Pinus massoniana (Masson pine) in South China. This study integrated transcriptomic and metabolomic analyses to identify differentially expressed genes (DEGs) and differentially accumulated metabolites associated with PWN resistance. By comparing the gene expression and metabolic profiles of healthy, mechanically wounded and PWN-infected Masson pine trees at 28 days post-inoculation, we identified that 1310 DEGs were specifically associated with PWN infection after excluding mechanical damage effects. Notably, combined KEGG analysis of transcriptomic and metabolomic data revealed significant enrichment of the α-linolenic acid metabolism pathway. Within this pathway, genes such as AOS, LCAT3 and DAD1 exhibited differential expression patterns, highlighting its pivotal role in PWN resistance. Metabolomic analysis revealed that key genes involved in jasmonic acid (JA) biosynthesis and plant hormone signaling showing strong regulation. Additionally, Quantitative Real-Time PCR (qRT-PCR) validation of selected DEGs confirmed the expression patterns observed in the transcriptomic data. Physiological assays also validated changes in key hormone levels, such as JA and methyl jasmonate, which are upregulated in the early stages of plant infection. These results highlight the importance of JA-mediated defence responses and provide novel insights for breeding strategies to improve P. massoniana's resistance to PWN infection.

Somatic embryogenesis (SE) is an in vitro mass propagation system widely employed in plant breeding programs. However, its efficiency in many forest species remains limited due to their recalcitrance. Somatic embryogenesis relies on the induction of somatic cell reprogramming into embryogenic pathways, a process influenced by transcriptomic changes regulated, among other factors, by epigenetic modifications such as DNA methylation, histone methylation and histone acetylation. Despite its relevance, epigenetic regulation of SE in forest species is not well understood. In this study, we analyzed histone H4 acetylation during SE in cork oak (Quercus suber L.) and evaluated the effects of suberoylanilide hydroxamic acid (SAHA), a histone deacetylase (HDAC) inhibitor, scarcely used in plants, on the process. Histone H4 acetylation levels progressively increased after SE induction, correlating with enhanced histone acetyl transferase (HAT) enzymatic activity. The HAT gene QsHAM1-like was activated in developing somatic embryos, while HDAC genes QsHDA9, QsHDA19, QsHDA15 and QsHDA2 showed similar expression patterns among them, and opposite profiles to QsHAM1-like HAT gene, suggesting a coordinated interplay of HAT and HDAC activities in modulating global H4 acetylation during SE. SAHA treatment elevated histone H4 acetylation, promoted embryogenic mass proliferation, and induced the expression of QsSERK1-like, an early SE marker. While continuous SAHA exposure inhibited embryo differentiation, its removal restored embryo development, significantly increasing somatic embryo production. Inhibition of HAT activity by butyrolactone 3 decreased histone acetylation levels and reduced somatic embryo formation, providing further evidence that histone acetylation is essential for SE development. These findings highlight the critical role of histone acetylation in the SE of forest trees and propose transient treatments with epigenetic modulators like SAHA as a promising strategy to enhance somatic embryo production in recalcitrant forest species.

Commercial citrus trees are predominantly grown in acidic soils with low boron (B) and high copper (Cu) concentrations. There are limited data on how B-Cu treatments affect the concentrations and distributions of nutrients in leaf and root subcellular fractions. Citrus sinensis seedlings were exposed to 2.5 (B2.5) or 25 (B25) μM H3BO3 × 0.5 (Cu0.5) or 350 (Cu350) μM CuCl2 for 24 weeks. Thereafter, we assayed the concentrations of Cu, calcium, magnesium, potassium and phosphorus in leaf and root cell wall (CW) fraction, organelle fraction and soluble fraction, as well as the expression levels of genes related to their homeostasis. B25 reduced Cu350-induced damage of CW structure and function via alleviating Cu350-induced increment in the Cu concentration and decrements in the calcium, magnesium, potassium and phosphorus concentrations, as well as Cu350-induced alterations of their distributions in root and leaf subcellular fractions, thereby promoting seedling growth. Also, leaves and roots of B2.5-treated seedlings displayed some adaptive responses to Cu350. Cu350 increased the distribution of Cu in CW fraction to prevent it from entering more sensitive targets, and the distributions of calcium, magnesium and potassium in CW fraction to maintain CW structure and function. However, Cu350 decreased the distribution of phosphorus in CW fraction, but increased the release of phosphate from organic-phosphate compounds and the conversion of pyrophosphate into phosphate to maintain phosphate homeostasis. Therefore, the study provided novel evidence for B alleviating Cu toxicity in citrus via maintaining the Cu, calcium, magnesium, potassium and phosphorus homeostasis in subcellular fractions, and a scientific basis for the rational application of calcium, magnesium, potassium and phosphorus fertilizers in woody crops (citrus) to prevent Cu toxicity.

Forests and grasslands experience shifts in woody plant cover creating a continuum of woody plants across space. Global change accelerates this, causing many ecosystems to experience the redistribution of woody plants. There is growing interest in understanding how these ecological changes influence ecosystem function including climate regulation. Research shows that woody plant expansion generally moderates microclimate but can impact regional macroclimate differently, while the loss of woody plants may lead to hotter regional macroclimates. However, the mechanisms in grasslands are largely speculative. Changes in shade, evapotranspiration and wind associated with woody plants may drive changes in microclimate. Because changes in temperature can impact ecosystem function, it is critical that we understand the mechanisms that drive this to determine how the redistribution of woody plants impacts grassland ecosystems. Our objective was to determine the mechanisms that cause woody plants to moderate microclimate in grasslands by testing specific hypotheses that may drive how individual woody plants influence microclimate. We performed a 2 × 2 × 2 factorial experiment in a fallow field across three independent variables (shade, pan evaporation and no wind) during the summer of 2023 and measured the microclimate. We analyzed the data using a linear-mixed modeling and model selection approach. We determined that the presence of shade alone best described microclimate temperature and vapor pressure deficit. During the daytime, shade moderated temperature, especially during high temperature extremes, and reduced vapor pressure deficit, while during the nighttime shade slightly increased temperature, but largely had little effect on vapor pressure deficit except during conditions with high vapor pressure deficit. Our findings show that ecosystems experiencing woody plant expansion could experience lower temperature and vapor pressure deficit, while ecosystems experiencing a loss in woody plant cover may experience higher temperature and vapor pressure deficit, which could impact ecosystem function.

Mangroves are ecosystems of high ecological and economic importance, particularly due to their capacity to store high amounts of carbon and stabilize soil. However, climate change and rising sea levels are intensifying salinity levels, challenging the survival of plant mangrove species, especially seedlings. Here, we evaluated the effects of different salinity concentrations on the growth and leaf water relations of Avicennia germinans (L.) L. and Rhizophora racemosa G.Mey. seedlings. Specifically, we tested whether A. germinans, due to its broader distribution, higher salinity tolerance and salt-excreting ability, would exhibit more pronounced adjustments and greater resilience to saline stress compared with R. racemosa. To this end, we conducted a greenhouse experiment, exposing 212 11-month-old seedlings (106 of each species) previously grown in freshwater to five salinity treatments over 3 months. These seedlings were analyzed for growth, embolism resistance, leaf water potential, osmotic parameters and gas exchange. Our results showed that A. germinans exhibited greater osmotic adjustment and stomatal regulation, enabling it to maintain leaf hydration and reduce the risk of embolism under high salinity. Conversely, R. racemosa adopted a more conservative strategy, with lower osmotic adjustment and stomatal regulation capacity but a higher hydraulic safety margin. Thus, we demonstrated that these species employ distinct strategies to cope with salinity, reflecting specific adaptations to their ecological distributions and salinity tolerance. These findings contribute to understanding the adaptive responses of mangrove seedlings to varying salinity conditions, with implications for the conservation of these ecosystems under predicted climate change scenarios.