Tree physiology最新文献

Tree species mixing has been widely recognized as an effective silvicultural strategy for enhancing both stand productivity and biodiversity. Nevertheless, its effects on branch radial growth and the underlying physiological mechanisms remain inadequately understood. In this study, we measured branch ring widths and 22 functional traits of pure and mixed plantations of Pinus massoniana Lamb. and Castanopsis hystrix Hook. f. & Thomson ex A. DC. to investigate the effects of species mixing on branch radial growth, to assess potential variations between even- and uneven-aged forest mixtures, and to elucidate the underlying physiological mechanisms. Our results demonstrated that tree species mixing generally promoted branch radial growth, as indicated by the basal area increment for both studied species. The effect of species mixing on branch radial growth was not significantly different between even- and uneven-aged mixtures for C. hystrix; however, it diminished with increasing age of P. massoniana. Our findings indicated that the radial branch growth of P. massoniana was related to larger tracheid radial diameter and higher hydraulic conductance. In contrast, increased branch radial growth of C. hystrix was more related to higher specific leaf area and thinner leaves in mixed plantations, which potentially improved the light capture efficiency and leaf carbon turnover rate. Our results also indicated that tree species mixture is an effective strategy for enhancing branch growth. The positive mixing effect could diminish as P. massoniana reaches an over-mature age in the mixed-species stand, implying that species mixing practices during the early stages of stand development provide more benefit. The findings provide valuable insights for formulating reasonable forest management strategies and improving the understanding of the eco-physiology of species mixing effects on tree growth.

Species from the genus Salicaceae are typically dioecious, yet a complex sex structure might be observed in natural populations. So far, the divergence in environmental adaptability between monoecious (either andromonoecious or gynomonoecious) and dioecious individuals (males and females) has been little studied. We investigated differences in growth, photosynthesis, nutrient-use efficiency, cadmium (Cd) accumulation and allocation among male, female and andromonoecious individuals of Populus schneideri (Rehder) N. Chao under nitrogen (N)-deficiency, Cd pollution and their combination. Compared with the control, N-deficiency alone and the combined stress reduced growth, photosynthesis, dry mass accumulation, photosynthetic N-use efficiency and phosphorus-use efficiency in all sexes, while inhibiting ascorbate peroxidase and glutathione reductase activities and inducing membrane lipid peroxidation. Males were the least affected by N-deficiency, followed by females, while andromonoecious plants were the most severely impacted. Under Cd addition treatments, the youngest (the first and second order) roots were the main organs of Cd accumulation across all sexes. Andromonoecious plants had the highest Cd content in leaves, while it was the lowest in males. Nitrogen-deficiency decreased Cd bioconcentration factor in female and andromonoecious plants, but not in males. Taken together, these results indicate that females and, in particular, andromonoecious plants are more negatively affected by N-deficiency and the combined stress, whereas males exhibit a greater adaptability. We argue that divergent responses of andromonoecious plants need to be considered in predicting the performance of ecosystems with complex sex structure.

Ectomycorrhizal (ECM) fungi, as major carbon (C) sinks, are critical to plant-soil C cycling. Although C allocation between plants and ECM fungi has been studied extensively, C transport time, the key component of C cycling, remains poorly understood. To address this, we collected new needles (weekly), roots (monthly) and ECM fungi (sporocarps and hyphae) of three genera (Cortinarius, Lactarius and Russula) in a boreal Scots pine (Pinus sylvestris L.) forest in Finland. We analysed the natural abundance C isotope composition (δ13C) of sugars or organic matter and observed a strong vapour pressure deficit (VPD) signal in needle sucrose δ13C. We coupled VPD with the δ13C of water-soluble carbohydrates (WSC, δ13CWSC) in sporocarps to determine C transport times. We found Lactarius and Russula, with short hydrophilic mycelia that enable efficient solute uptake, had transport times of 6-13 days, peaking at 8 days. In contrast, Cortinarius, with extensive hydrophobic mycelia that limit water and solute movement, showed slower transport times of around 18 days. The different transport time is likely attributable to a more extensive mycelial network and potentially higher C demand in Cortinarius compared with Lactarius and Russula. The three genera also showed a marginally significant effect on δ13CWSC in sporocarps (P = 0.06, analysis of covariant). This study highlights that natural abundance δ13C analysis offers a practical alternative to pulse-labelling for estimating C transport time in complex plant-fungal interactions, where the latter is difficult to implement. The longer transport time of Cortinarius compared with Lactarius and Russula is critical during periods of reduced photosynthesis, when limited C supply makes fast allocation essential for sustaining belowground metabolism. Slower transport may weaken its role and reduce forest productivity in boreal forests with short growing seasons. As global warming favours Cortinarius, its longer C transport time may impede soil C cycling and nutrient turnover.

Sexual dimorphism in dioecious species can shape divergent hydraulic strategies in response to environmental stress, yet integrative studies linking anatomical and physiological traits across different plant organs remain scarce. We investigated sex-specific water-use strategies in two Mediterranean shrubs, Pistacia lentiscus L. and Rhamnus alaternus L., by analyzing leaf and wood anatomy, leaf functional traits, gas exchange and chlorophyll fluorescence. Male plants of both species exhibited conservative morpho-anatomical traits, including smaller, thicker leaves, lower specific leaf area (SLA), higher dry matter content and reduced intercellular spaces, traits typically associated with drought resistance strategies. In P. lentiscus, these traits correlated with higher photosynthetic rates and Fv/Fm values, alongside greater stomatal density and vessel frequency, suggesting coordinated investment in carbon gain and hydraulic efficiency/safety. Conversely, females displayed acquisitive traits (higher SLA, wider intercellular spaces, lower vessel frequency), potentially enhancing photosynthesis under mesic conditions but increasing vulnerability to drought-induced embolism. In R. alaternus, female individuals maintained higher net photosynthesis and instantaneous water- use efficiency, while males exhibited greater Fv/Fm and a decoupled leaf-wood coordination. These findings suggest that males may adopt safer hydraulic architectures, while females, potentially constrained by reproductive demands, pursue efficiency-driven strategies, still maintaining vessel redundancy in wood. As aridity intensifies in Mediterranean regions, such dimorphism may influence population dynamics, sex ratios and species resilience. Our results underscore the ecological significance of species-specific sex-based hydraulic variation and the necessity of incorporating sex into trait-based models of plant responses to climate change.

Drought stress severely impacts the growth, yield and quality of apple (Malus domestica). Abscisic acid (ABA) and basic helix-loop-helix (bHLH) transcription factors play crucial roles in regulating the drought response in many plants, but the potential interactions between bHLH and ABA in response to drought in apple still need to be discovered. Herein, we identified a bHLH transcription factor, ORG2 (OBP3-responsive gene 2), from M. hupehensis, and the expression of which is induced by drought and ABA. Apple plants that overexpressed MhORG2 were more sensitive to drought stress, while silencing MhORG2 caused the opposite phenotype. Specifically, we found that MhORG2 could directly bind to the DRE element in the MhAAO3 promoter and repress its expression, thereby ultimately reducing drought tolerance. Furthermore, MhORG2 represses the expression of antioxidant enzyme genes (MhSOD, MhAPX1 and MhCAT), leading to the accumulation of reactive oxygen species (ROS) and consequently reducing the drought tolerance of apple plants. Our findings uncover a novel mechanism by which MhORG2 negatively regulates drought tolerance in apple plants, offering a potential target for the development of drought-tolerant crops via biotechnological approaches.

Photosynthesis links terrestrial carbon, water and nutrient cycles. Photosynthetic least-cost theory suggests that plants optimize photosynthesis at the lowest summed investments in nutrient and water use. The theory predicts that increasing nutrient availability should increase nutrient allocation toward photosynthetic enzymes and reduce stomatal conductance, allowing similar photosynthetic rates achieved at a lower ratio of leaf intercellular to atmospheric CO2 concentration (χ) and reduced water loss. The theory suggests similar responses to increasing soil pH in acidic soils due to common correlations between soil pH and nutrient availability. However, empirical tests of the theory outside of environmental gradients are rare. To test this theory experimentally, we measured photosynthetic traits in mature Acer saccharum Marshall trees growing in a 9-year, nitrogen-by-pH manipulation in the northeastern USA. Increasing soil nitrogen availability did not affect net photosynthesis (Anet) or stomatal conductance (gs) rates, but was associated with increased area-based leaf nitrogen content (Narea), increased photosynthetic capacity (Vcmax, Jmax) and decreased χ (i.e, increased water-use efficiency). These patterns strengthened the tradeoff between nitrogen and water use, indicated by steeper slopes of Narea-χ and Vcmax-χ with increasing soil nitrogen availability. When examined across all plots, soil pH had no effect on any traits. However, in plots without nitrogen additions, increasing soil pH increased the slopes of Narea-χ and Vcmax-χ, though did not modify χ. Supporting the theory, A. saccharum maintained Anet across the soil nitrogen availability gradient by trading less efficient nitrogen use for more efficient water use. Additionally, the effects of soil pH on nitrogen-water use tradeoffs appear to occur through indirect pH effects on soil nitrogen availability. These results indicate that elevated nitrogen deposition could stimulate photosynthesis less than commonly expected and instead reduce water losses, and conversely, that reductions in photosynthesis expected from increasing nitrogen limitation in some regions could be lessened if accompanied by increased transpiration.

The success of CRISPR genome editing studies depends critically on the precision of guide RNA (gRNA) design. Sequence polymorphisms in outcrossing tree species pose design hazards that can render CRISPR genome editing ineffective. Despite recent advances in tree genome sequencing with haplotype resolution, sequence polymorphism information remains largely inaccessible to various functional genomics research efforts. The Populus VariantDB v3.2 addresses these challenges by providing a user-friendly search engine to query sequence polymorphisms of heterozygous genomes. The database accepts short sequences, such as gRNAs and primers, as input for searching against multiple poplar genomes, including hybrids, with customizable parameters. We provide examples to showcase the utilities of VariantDB in improving the precision of gRNA or primer design. The platform-agnostic nature of the probe search design makes Populus VariantDB v3.2 a versatile tool for the rapidly evolving CRISPR field and other sequence-sensitive functional genomics applications. The database schema is expandable and can accommodate additional tree genomes to broaden its user base.

Sulfate-proton co-transporters (SULTRs) mediate sulfate uptake, transport, storage and assimilation in plants. The SULTR family has historically been classified into four groups (SULTR1-SULTR4), with well-characterized roles for SULTR groups 1, 2 and 4. However, the functions of the large and diverse SULTR3 group remain poorly understood. Here, we present an updated phylogenetic analysis of SULTRs across angiosperms, including multiple early-divergent lineages. Our results suggest that the enigmatic SULTR3 group comprises four distinct subfamilies that predate the emergence of angiosperms, providing a basis for reclassifying the SULTR family into seven subfamilies. This expanded classification is supported by subfamily-specific gene structures and amino acid substitutions in the substrate-binding pocket. Structural modeling identified three serine residues uniquely lining the substrate-binding pocket of SULTR3.4, enabling three hydrogen bonds with the phosphate ion. The data support the proposed neofunctionalization of this subfamily for phosphate allocation within vascular tissues. Transcriptome analysis of Populus tremula × Populus alba revealed divergent tissue expression preferences among SULTR subfamilies and between genome duplicates. We observed partitioned expression in vascular tissues among the four SULTR3 subfamilies, with PtaSULTR3.4a and PtaSULTR3.2a preferentially expressed in primary and secondary xylem, respectively. Gene coexpression analysis revealed coordinated expression of PtaSULTR3.4a with genes involved in phosphate starvation responses and nutrient transport, consistent with a potential role in phosphate homeostasis. In contrast, PtaSULTR3.2a was strongly coexpressed with lignification and one-carbon metabolism genes and their upstream transcription regulators. PtaSULTR3.2a belongs to a eudicot-specific branch of the SULTR3.1 subfamily found only in perennial species, suggesting a specialized role in lignifying tissues. Together, our findings provide a refined phylogenetic framework for the SULTR family and suggest that the expanded SULTR3 subfamilies have undergone neofunctionalization during the evolution of vascular and perennial plants.

Understanding the biological mechanisms underlying tree responses to drought is critical for preserving forest biodiversity, as current global climate change is challenging the ability of drought-sensitive trees to cope with water shortage. In this study, we investigate how silver fir (Abies alba Mill.) responds to experimental drought stress, more specifically, atmospheric drought caused by high vapor pressure deficit (VPD), by analyzing the gene expression and DNA methylation profiles of different organs alongside physiological variables under well-watered, drought and recovery conditions. Roots exhibited a stronger transcriptomic response than leaves, with 50 times more altered transcripts, revealing their value for assessing water stress in this species through the expression of genes involved in water transport. In addition, brassinosteroid-related genes can serve as stress markers both in roots and leaves. VPD-induced drought also affected DNA methylation, which, like transcriptomic and physiological variables, begins to normalize once the stress is over, suggesting some resilience to drought. However, A. alba struggles to improve intrinsic water-use efficiency, which raises its vulnerability to VPD-induced drought. Our results suggest that silver fir forests might be able to cope with short drought events, but prolonged periods of water shortage, which are likely to increase with climate change, may surpass their resilience thresholds, increasing the likelihood of hydraulic failure and carbon starvation.

Members of the salicaceous genus Populus are primarily used by plant biologists as a model system for understanding the genetic underpinnings of woody plant growth and development. Beyond their importance to those conducting developmental research, Populus spp. are key members of ecosystems in the Northern Hemisphere and show promise as a vital renewable source of biomass for sustainable biofuel production. This genus also produces a class of signature herbivore-deterring and medicinally significant phenolic glycosides, commonly referred to as salicinoids. Although salicinoids in Populus are primarily associated with defense against biotic disturbances, they have also been implicated in structuring the chemotaxonomy of Populus and Salicaceae, shaping endophytic microbiomes, directing abiotic stress responses and participating in primary metabolism. Despite advancements in understanding these interactions through functional genomics and biotechnological techniques such as CRISPR/Cas9, much about their function and biosynthesis still remains obfuscated. Here, we summarize a global view of progress made in Populus salicinoid research, focusing particularly on studies conducted through a biotechnological lens, to elucidate the distribution, ecological significance, and biosynthesis of these compounds.