Tree physiology最新文献

Soil fungi establish symbiotic associations with plant roots, which provide nutrients in exchange for photosynthate from the host. Despite the recognized importance of fungal symbiosis, how root-associated fungal communities respond to light qualities remains unclear. In this study, we conducted a novel spectral attenuation experiment involving seedlings of two temperate tree species, Quercus mongolica Fisch. ex Ledeb. (ectomycorrhizal [ECM]) and Acer mono Maxim. (arbuscular mycorrhizal [AM]). The experimental design incorporated five spectral treatments, including ambient full-spectrum as control and various attenuations of ultraviolet (UV) and visible light. We quantified tree growth and root traits, and profiled root-associated fungal communities through high-throughput sequencing. Results showed that plant growth and root traits varied depending on tree species and spectral treatments. Blue light significantly promoted total biomass of Q. mongolica, but reduced root exudative carbon, sugar and phenolics. In contrast, A. mono showed no spectral changes in biomass and had the lowest root exudative sugar and phenolics in control. Higher root exudative carbon and phenolics were observed in A. mono than in Q. mongolica. Root-associated fungal communities also showed distinct responses to spectral treatments and tree species. Sob's and Chao 1 indices of Q. mongolica fungal communities were significantly lower than those of A. mono under UV attenuation, and alterations in community structure were more pronounced in A. mono. These changes were strongly associated with root traits, particularly exudative carbon, sugar and total phenolics. Within fungal communities, Q. mongolica was dominated by ECM and saprotrophic fungi, and A. mono by AM and saprotrophic fungi. The relative abundance of ECM fungi in Q. mongolica and that of AM fungi in A. mono was lowest when UV-B radiation was attenuated. In total, these findings highlight the crucial role of root traits and their interaction with fungi when exploring plant adaptation to varying light environments.

Trichoderma is reported to enhance plant salt adaptability, but the mechanisms still need in-depth investigation. This study sought to dissect how Trichoderma asperellum manipulates root ions exchange in salt-stressed wolfberry (Lycium chinense) to satisfy nitrogen acquisition and preserve K+/Na+ homeostasis. Trichoderma agent (TA) was supplemented around the roots of potted plants, and salt stress was conducted by watering with NaCl solution. Salt adaptability of wolfberry was enhanced by T. asperellum, as TA supplement protected photosynthesis, alleviated biomass reduction and increased tissue N accumulation and K+/Na+ under salt stress. Consistently, T. asperellum enhanced root Na+ extrusion and K+ retention in salt-stressed wolfberry, which was related to Na+/H+ antiporter and K+ outward-rectifying channels, as pretreatments with their inhibitors depressed root Na+ efflux but caused K+ efflux. Considering inhibited plasma membrane (PM) H+-ATPase synchronously dampened root Na+ extrusion and K+ retention under salt stress, T. asperellum was inferred to enhance root Na+ extrusion and K+ retention in salt-stressed wolfberry by inducing PM H+-ATPase. Elevated root plasma membrane H+-ATPase activity by T. asperellum was actually observed in salt-stressed wolfberry and had nothing with constitutive transcript expression. The activated H+-ATPase by T. asperellum also provided more driving force for H+/NO3- symporter and increased root NO3- absorption. Trichoderma asperellum prevented salt-induced great root NH4+ efflux and retained mild NH4+ influx likely because NH4+ efflux was not required for restricting Na+ entry. Overall, T. asperellum activated root plasma membrane H+-ATPase to optimizing root ions exchange and then improved nitrogen acquisition and K+/Na+ homeostasis in wolfberry under salt stress. According to the structural equation model analysis, PM H+-ATPase had a positive effect on photosynthesis, root sugar content, root respiration and itself sequentially, highlighting that the activated root PM H+-ATPase by TA supplement enhanced wolfberry salt adaptability by driving a favorable cooperation between roots and aerial part.

Indian sandalwood (Santalum album) is an economically important facultative parasite that develops a specialized multicellular organ, the haustorium, to absorb water and nutrients from its hosts. To elucidate the molecular mechanisms underlying haustorium development, we conducted a transcriptome analysis across six S. album tissues. We found that SaRac1, encoding a functional small GTPase, is specifically expressed in the haustorium. We employed host-induced gene silencing (HIGS) by generating transgenic poplar (Populus alba × P. glandulosa) hosts that express hairpin RNAs to target and downregulate SaRac1 in the parasite. Santalum album grown with SaRac1 RNAi transgenic host plants exhibited significantly suppressed haustorium development compared with those grown with wild-type or empty-vector controls. Mechanistically, SaRac1 interacts with SaRbohA, and this interaction synergistically enhances ROS production. Exogenous H₂O₂ application significantly upregulated key haustorium formation-related genes. In contrast, the Rboh inhibitor diphenyliodonium chloride (DPI) suppressed the expression of SaYUCCA and SaSBT in S. album grown with wild-type and empty-vector control hosts, thereby reducing haustorium formation. In S. album plants grown with RNAi hosts, SaSBT and SaEXPA were also downregulated by DPI application. Our findings identify a crucial mechanism whereby SaRac1 promotes haustorium formation by modulating ROS signaling and provide novel insights into the molecular physiology of plant parasitism.

The growth of boreal trees is expected to benefit from increasing global temperatures through enhanced photosynthetic rates and longer growing seasons. However, since photoperiod is independent of climate change, it may limit the expected growth benefits from a longer growing season and could thus constrain boreal trees' physiological responses to warming. We carried out a growth chamber experiment on 2-year-old Norway spruce (Picea abies) cuttings from two latitudinal origins to investigate the interaction between day length (20/4 h vs 14/10 h light/dark) and enhanced temperatures (25/20 °C vs 15/10 °C day/night) on height growth, bud development and shoot-scale gas exchange. Height growth was greater under longer day length while bud development occurred faster both under longer day length and higher growth temperature. Growth temperature did not have a significant effect on the light-saturated photosynthetic rate but higher growth temperature resulted in lower dark respiration rate. Cuttings in the low-growth temperature treatment exhibited higher apparent quantum yields indicating that lower growth temperature benefited net carbon uptake under low light availability, such as the conditions experienced by seedlings growing in the forest understory. Day length did not influence the thermal acclimation of shoot-scale gas exchange. The two populations from different origins did not differ in the measured parameters, except for a higher dark respiration rate in the high latitude cuttings. Overall, while day length did not affect the thermal acclimation of photosynthetic processes, it appears to constrain height growth and bud development, thereby reducing the potential performance benefit of a warming-induced lengthening of the growing season.

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.