Tree physiology最新文献

Albinism is typically lethal in autotrophic plants due to the absence of photosynthetic pigments and functioning chloroplasts. Yet, rare exceptions occur where achlorophyllous individuals persist in natural ecosystems. We investigated the physiological, anatomical and isotopic characteristics of naturally occurring albino European beech (Fagus sylvatica L.) trees in the Moravian Karst, Czechia. One albino individual, estimated to be ~30 years old, represents an unprecedented case of long-term survival without photosynthesis in a woody angiosperm. Using a multi-parameter approach-including stable isotope analysis (δ13C, δ15N), pigment quantification, saccharide profiling, gas exchange, leaf anatomy, stomatal traits and microsatellite genotyping-we confirmed the absence of photosynthetic capability, explored potential mechanisms of carbon acquisition and assessed clonal affiliation of the albino to its neighbouring trees. An albino individual exhibited almost absent photosynthetic pigments and lacked differentiated thylakoids, and showed significantly reduced stomatal conductance and density. The CO2 release from albino leaves indicated predominant mitochondrial respiration even under the light conditions. Intriguingly, albino leaves accumulated higher concentrations of soluble sugars (notably glucose and fructose) and were enriched in δ13C, similar to mixotrophic orchids, suggesting heterotrophic carbon uptake. Microsatellite genotyping revealed that the albino individual is not genetically identical to any of the surrounding green trees, thus making root suckering unlikely. While partial mycoheterotrophy cannot be entirely excluded, the data strongly support a trophic strategy based on carbon translocation from an autotrophic donor through root connectivity. This study offers novel physiological insights into albino tree survival and illustrates the complexity of belowground integration in forest ecosystems.

The karst peak-cluster depression landscape is characterized by pronounced topographic and edaphic heterogeneity, resulting in a high degree of spatial variability in resource availability. Such a complex environmental mosaic influences plant functional traits and their adaptive strategies. However, the patterns of trait variation and their underlying environmental drivers in karst peak-cluster depressions remain poorly understood. In this study, we investigated a 15-ha forest dynamics plot in the Nonggang Nature Reserve, Guangxi. We used linear mixed models to partition variance, principal component analysis to examine trait covariation, and redundancy analysis combined with hierarchical partitioning to evaluate the effects of topographic and edaphic factors on leaf functional traits at the community, species and intraspecific levels. The results showed that trait variation was mainly driven by interspecific differences, with part of the variation attributable to evolutionary history. Morphological traits and physiological traits exhibited relatively higher intraspecific and interspecific variation, respectively. The trait covariation patterns revealed that several leaf chemical traits exhibited atypical modes of coordinated variation. The explanatory power of topographic and edaphic factors for trait variation differed among ecological levels, being highest at the species level, followed by the community and intraspecific levels. Among these, the soil carbon-to-nitrogen ratio and slope were identified as the main drivers of species-level variation. Overall, our findings reveal functional shifts in plant ecological strategies in complex karst landscapes and emphasize the differential influence of topographic-soil factors across hierarchical levels, providing empirical evidence for understanding plant adaptive mechanisms along multidimensional environmental gradients.

Populus trees are commonly used in the construction of shelter forests in water-limited areas of China; however, different poplar species are facing various levels of dieback risks under the increased drought associated with climate change. The objective of this study was to explore whether crown height affects the xylem hydraulics and to evaluate the suitability of different Populus species for constructing sustainable shelterbelt in water-limited regions. Xylem hydraulics and water relations of branches at upper and lower positions of tree crown, alongside radial growth rate, were compared between two species that are commonly used in shelterbelt construction but have contrasting crown types, i.e., Populus simonii Carrière with short oval crowns and Populus pioner Jabl. with tall columnar crowns. The results showed that as height increases, P. simonii exhibited enhanced hydraulic efficiency and safety, while no significant differences in these hydraulic traits across canopy layers were observed in P. pioner. In addition, the upper branches of P. pioner have lower water potential and longer water flow paths, resulting in lower hydraulic safety margin, which means that the species was more prone to hydraulic limitation and eventually dieback. Adjustments of vessel sizes and leaf mass per area along the crown of P. simonii contributed to the increase in xylem hydraulic capacity in upper branches and the homeostasis of leaf water potential within the crown. Although the adjustment of using water more conservatively potentially compromised the whole-tree carbon assimilation and thus growth rate, P. simonii seemingly showed stronger adaptability to projected drought intensification by shedding part of branches at the crown bottom and might thus be a more suitable species for establishing stable shelterbelt in water-limited areas. This study, from perspectives of tree physiology, provides an important reference for afforestation species optimization and thus the sustainable management of shelterbelts in water-limited areas of northern China.

Priestia sp. B6 (strain B6) enhances lead (Pb) translocation from the roots to the aerial parts in Salix integra, nearly doubling its Pb translocation capacity. This study aims to elucidate the mechanism by which strain B6 facilitates Pb entry into the root xylem via the apoplastic pathway. Priestia sp. Strain B6 was capable of colonizing the roots, branches, and leaves of S. integra. It migrated from the roots to the branches via the xylem, and subsequently moved to the epidermis of the branches and leaves through intercellular spaces. The deposition sites of strain B6 and Pb were primarily located in the cell walls and intercellular spaces. Inoculation with strain B6 resulted in a maximum 70.22% increase in Pb concentrations in the root cell walls, and this was associated with reduced pectin methylesterase (PME) activity and enhanced the number and migration activity of functional groups. Additionally, Pb desorption capacity was increased, allowing Pb to re-enter the intercellular spaces. Besides, abscisic acid (ABA), and gibberellin A3 (GA3) concentrations and phenylalanine ammonia-lyase (PAL) activity were reduced by 40.48%, 52.78%, and 62.23%, respectively. Consequently, the Casparian strip formed further from the root tip, and both the Casparian strip and suberin lamellae developed incompletely, which facilitated Pb entry into the root xylem via the apoplastic pathway. Simultaneously, the Pb detoxification capacity of S. integra was enhanced by reducing the H2O2, OH- and increasing the concentrations of chelating agents glutathione (GSH) and metallothionein (MT), as well as the activities of superoxide dismutase (SOD) and peroxidase (POD). These findings indicate that strain B6 enhances Pb translocation through the apoplastic pathway while promoting Pb detoxification in the roots of S. integra.

Stable isotopes of carbon, oxygen and hydrogen in tree rings provide a record of plant physiological processes and environmental variability. Although an increasing number of studies now apply triple-isotope approaches, no investigation has yet tested their temporal stability over millennial timescales or assessed the relative impacts of physiology versus climate on long-term isotopic signals. Here, we used 9000 years of multi-isotope records from co-occurring deciduous larch (Larix decidua) and evergreen cembra pine (Pinus cembra) at the Alpine treeline. We found a high interspecies coherence for δ18O throughout the Holocene with a robust summer hydroclimate sensitivity, confirming its dominance by environmental drivers. In contrast, δ13C and δ2H show weaker and less stable coherence, reflecting species-specific physiology. Larch exhibits tight δ2H-δ18O and δ2H-δ13C correlations and stronger climate sensitivity, consistent with its reliance on freshly assimilated carbon. Pine, by contrast, shows weaker δ2H-climate relationships and frequent decoupling from δ13C and δ18O, reflecting potential storage use and metabolic fractionations. Thus, inter-isotope relationships reveal that δ18O is a robust long-term climate proxy, while δ13C and δ2H encode contrasting carbon-use strategies and metabolic processes across species that may vary over time. Together, these findings demonstrate that multi-isotope, multi-species approaches not only strengthen climate reconstructions but also provide a physiological dimension to long-term isotope records.

Manganese (Mn), a critical component of the photosystem II oxygen-evolving complex, chlorophyll biosynthesis pathway, and antioxidant systems, manifests functional mechanisms that remain inadequately elucidated in the context of arbuscular mycorrhizal fungi (AMF)-mediated plant tolerance to water deficit. This study examined how Funneliformis mosseae inoculation enhances water deficit (55% maximum of the maximum field water capacity for 10 weeks) tolerance in Poncirus trifoliata by modulating Mn chemical forms and key physiological processes. AMF inoculation significantly improved various growth parameters irrespective of soil moisture. AMF inoculation significantly enhanced photosynthetic efficiency, various chlorophyll levels, and photosystem stability under water deficit. In leaves, AMF inoculation significantly increased levels of inorganic, bound, and residual Mn fractions under varying moisture conditions, while concurrently reducing oxalate-bound Mn, in addition to an increase in phosphate Mn under water deficit. AMF colonization upregulated the expression of PtHEMG1 and PtMnSOD under water deficit, and it also modulated the expression of PtMTPs, as evidenced by the enhancement of specific PtMTP members (PtMTP4/5/7/9) under normal watered and the suppression of PtMTP3/9 under water deficit. Correlation analysis demonstrated coordinated regulation among photosynthetic efficiency, Mn levels, PtMTPs, and PtHEMG1. In conclusion, the AMF-induced shift in Mn chemical forms (e.g., pectate-/protein-bound Mn) coordinated with enhanced chlorophyll biosynthesis and photosynthetic performance in plants under water deficit.

Subalpine forests are one of the regions where the adjustment of fine-root water uptake becomes important for tree adaptation; however, this process has not been adequately investigated. Here, we aimed to detect species-specific elevational variation in fine-root water uptake and its relationship with the variation in fine-root functional traits in subalpine forests. Fine-root water flux (WFsoil-root) was evaluated from direct measurement of the water potential difference between the soil and fine roots, and the hydraulic conductivity of fine roots of Abies mariesii and Betula ermanii. Additionally, we measured the average diameter, specific root length, and root tissue density (RTD) as morphological traits, and nitrogen content (N) as a chemical trait. These traits were compared at different elevations (2,000, 2,300, and 2,500 m), and the relationships between WFsoil-root and root morphological and chemical traits were evaluated. The WFsoil-root of A. mariesii was highest at 2,500 m compared to the WFsoil-root value of B. ermanii at 2,300 m. These results suggest that the limiting factors of fine-root water uptake differ between A. mariesii and B. ermanii in subalpine forests. Additionally, WFsoil-root covaried with the RTD-N axis along the elevational gradient, and trees increased WFsoil-root with increasing RTD. This result brings the new insight that higher RTD of fine root could function as the acquisitive traits for water uptake in subalpine forests. However, covariation of WFsoil-root with RTD-N axis was less obvious in A. mariesii than B. ermanii indicating different driving mechanisms of WFsoil-root between the species. Trees must cope with several factors limiting their growth in subalpine forests. Adjustment of WFsoil-root may contribute to the species-specific strategy, which compensates for their physiological processes and growth, and coordination with the RTD-N axis would be important for effective water uptake in cold and carbon-limited environments.

Nitrogen (N) deposition disrupts mineral element dynamics, exacerbating phosphorus (P) limitation and inducing multiple nutrient imbalances. Although P addition is widely adopted to mitigate these negative effects by enhancing P availability, how multi-mineral elements in tropical trees respond to N and/or P addition remains poorly understood, particularly regarding their tissue-specific concentrations and inter-element relationships. Here, we investigated the effects of a decade-long N, and/or P addition on mineral element concentrations across tissues in two typical plantation tree species, Eucalyptus urophylla (EU) and Acacia auriculiformis (AA), in southern China. We also examined how these additions altered correlations among elements. Our results showed that both EU and AA maintained stable macro-element levels under long-term N addition, yet experienced significant changes in their micro-elements. This was evident by increased root Al and Fe concentrations in EU and decreased leaf Fe concentrations in AA. However, tissue-specific responses differed. EU exhibited significant response ratios in root mineral elements, whereas AA had negative response ratios in leaves and branches. Under long-term P and N+P addition, both species accumulated higher P and Na but lower K, with significant response ratios in leaf mineral elements. Crucially, long-term N or/and P addition altered elemental correlation patterns. Specifically, long-term N addition strengthened S interaction with other elements in both species, whereas long-term P disengaged P from other elements in AA, and long-term N+P addition disrupted P interconnectedness in EU. Moreover, long-term N+P addition simplified mineral element network interactions in both species. These shifts in elemental correlations highlight potential cascading effects on ecosystem structure and function. Our findings demonstrate that tropical trees dynamically adjust mineral element concentrations across tissues and reconfigure inter-element relationships in response to N- and P-induced environmental changes. These adjustments have profound implications for nutrient cycling and ecosystem resilience in tropical forests under global changes.

Although the presence of methanogens in living tree trunks was reported more than 50 years ago, it has recently been suggested that trees in upland forests constitute a net sink for atmospheric CH4, which contradicts other recent or older studies. To clarify the role of tree trunks as net emitters or consumers of CH4, we measured trunk CH4 fluxes of 11 upland species, up to 12 m above ground for some trees, and estimated their ex-situ potential CH4 oxidation capacity. Trees from seven species emitted CH4 from their trunks, some at height well-above 2 m above ground, whereas little CH4 was emitted from the trunks of the other four species. The average rate of CH4 oxidation was an order of magnitude lower than the average trunk CH4 fluxes measured on the same individuals, consistent with the very weak net uptake of CH4 occasionally measured on some trees. CH4 oxidation in the bark could nevertheless mitigate CH4 emissions from tree trunks. Trees in our mountain forest were likely a net source of CH4 to the atmosphere rather than a net sink of atmospheric methane, suggesting that it is premature to conclude that tree surfaces could be a significant sink for atmospheric CH4 globally.

Accelerated drought stress along with global warming has significantly impacted high-elevation ecosystems, causing a massive decline of conifers worldwide, including Korean fir (Abies koreana E.H.Wilson). However, studies on the climate adaptability and underlying physiological mechanisms of coexisting species remain limited, despite their importance for understanding future species composition. To investigate species-specific responses to climate change, a rainfall reduction and heat experiment was implemented by blocking precipitation by 33% and 67% and increasing temperature by 1.5°C for three coexisting high-elevation tree species: Korean fir, Korean pine (Pinus koraiensis Siebold & Zucc.), and Manchurian ash (Fraxinus mandshurica Rupr.). Korean fir exhibited the most sensitive stomatal control to conserve its hydraulic status, which significantly suppressed photosynthesis, depleted root starch reserves, and ultimately reduced growth. In contrast, Manchurian ash showed the highest resistance, with stable stomatal response through active leaf osmoregulation and increased chlorophyll content, which supported the maintenance of photosynthesis and root nonstructural carbohydrate (NSC) reserves. Korean pine exhibited intermediate responses, with the second-most sensitive stomatal and photosynthetic regulation, along with temporarily tolerant traits such as increased leaf sugar and chlorophyll content, while allocating relatively more carbon to growth than to storage. This resulted in the highest mortality in Korean fir, followed by Korean pine and Manchurian ash. This study enhances our understanding of the early stress responses of high-elevation species and provides insights into predicting future forest dynamics.