Tree physiology最新文献

Woody plants have garnered significant attention in recent years for their essential ecological and economic contributions. Protoplasts, isolated from plant cells, have exhibited remarkable totipotency and offered immense potential in a broad array of biological and biotechnological fields. These include, but are not limited to, protein gene expression regulation, functional gene analysis, subcellular localization, interaction studies, gene editing and single-cell sequencing. This review offers a comprehensive overview of protoplast isolation methods, key influencing factors, purification techniques and viability assessment. It further explores the use of protoplast transient expression systems for gene function characterization, while highlighting the diverse applications of protoplast-based technologies, such as fusion, regeneration, genome editing and single-cell sequencing. With technological advancements, future breakthroughs in these areas will be poised to create new avenues for research, genetic improvement and biotechnological innovations in woody plants.

Fine root carbon (C), nitrogen (N) and phosphorus (P) stoichiometric characteristics are key indicators of plant nutrient acquisition strategies and environmental adaptation. Yet, their responses to long-term N deposition, especially the hierarchical variations across root orders, remain unclear, hindering a mechanistic understanding of root system plasticity. To assess root-order-specific responses of fine root C, N and P concentrations and stoichiometric ratios to long-term N fertilization, a field experiment was initiated in 2014 in coastal Metasequoia glyptostroboides Hu & W.C. Cheng plantations in Jiangsu Province, eastern China, involving five N fertilization levels (0, 56, 168, 280 and 336 kg ha-1 year-1). The results showed that N fertilization generally increased fine root N concentration, C/P and N/P ratios, and decreased P concentration and C/N ratio across root orders. Except for fine root C concentration, the absolute response ratios of fine root stoichiometric traits to N fertilization exhibited an increasing trend across root orders. The direct effects of N fertilization on the fine root stoichiometric characteristics were obviously higher than the indirect effects whether at the scale of the entire root system, functional module or individual root order. Significant associations between fine root functional traits and stoichiometric characteristics were observed at the scale of the entire root system, whereas such relationships were not evident at the scale of individual root order or functional module. Overall, the fine root stoichiometric characteristics responded more strongly with increasing root order under N fertilization, and interpretations of the drivers of these characteristics should be scale-explicit.

Understanding the factors and processes of tree water use at night is critical for sustainable fruit production and ecological protection within the context of increasing global climate extremes. A long-term experiment was set up in China's Loess Plateau region on rainfed fruit trees-jujube (grown under arid, semi-arid conditions) and apple (grown under semi-humid, drought-prone conditions). Data were collected under both wet and dry conditions and then analyzed for total sap flow (Q), daytime sap flow (Qd), nighttime sap flow (Qn) and the related components of nighttime canopy transpiration (QTn) and nighttime water recharge (QRn). The results showed that the percentage fraction of Qn to Q was 27.6% for jujube and 20.9% for apple. For jujube, QTn/Qn was 67.5%, which was higher than that of apple (56.9%), a species that was under relatively humid conditions. At annual scale, higher annual precipitation (P) resulted in higher Qd but lower Qn. At the daily scale, the components of Qn were positively correlated with leaf area index (LAI) but negatively correlated with solar radiation (Rs) and vapor pressure deficit (VPDn) for jujube at Mizhi Station. Under low LAI/Rs conditions, Qn components of jujube trees had negative correlation with soil water content (SWC). The components of Qn are positively correlated with SWC for apple at Luochuan Station. Under adequate SWC, QRn increased with increasing Qd for apples. Structural equation modeling suggested that the main drivers of nighttime water use were similar for the two fruit trees, but with stronger direct effect of LAI on Qn for jujube. Moreover, Rs mainly affected Qn/Q and QTn/Q through an indirect pathway in jujube, while both its direct and indirect effects were strong and almost equivalent in apple. The findings are critical for the management of fruit trees in ecological environments under worsening environmental conditions.

In subtropical regions, frequent rainfall induces periodic anaerobic conditions in the soil which triggers redox reactions of iron (Fe) and alters the bioavailability of phosphorus (P). While the effects of rainfall events on these processes are well understood in agricultural ecosystems, their influence remains unclear on rhizosphere soil P availability and the P content of Chinese fir (Cunninghamia lanceolata (Lamb.) Hook.) seedling tissues. Therefore, we conducted a greenhouse pot experiment, simulating a short-term (111 days) alternating anaerobic soil environment (95% field capacity) to investigate the dynamics of rhizosphere soil inorganic P in Chinese fir seedlings. The anaerobic treatments (denoted by N) were applied in three stages (S1, S2, S3) to seedlings of two varieties: 'Yang 061' (A-hygrophilous) and 'Yang 020' (B-drought-tolerant). A control group maintained at 70% field capacity was fully replicated for all treatments. Our results show that the anaerobic environment, coupled with increased root exudation of scopoletin, directly or indirectly promoted Fe reduction in the soil. Concurrently, available P concentrations increased by 42.8% and 66.3% in the AN1 and AN3 treatment groups, respectively, leading to increased total P content in seedling leaves and roots compared with the controls. Partial least-squares path models and random forest analyses indicated that the key drivers of inorganic P availability under anaerobic conditions differed between seedling varieties. For variety A, alpha and beta diversity, along with the dominant phylum (Proteobacteria), of the phosphate-solubilizing bacterial community were the dominant drivers, while dehydrogenase enzyme activity was an additional driver for variety B. These findings provide a scientific basis for understanding P cycling processes in the Chinese fir rhizosphere under changing rainfall regimes in subtropical areas.

Plantations are an important component of global forest coverage, but their performance is increasingly affected by water limitation due to climate change. Employing a rainfall exclusion facility, we report on the impacts of reduced rainfall on leaf water relations and organ morphological traits, in six Populus varieties commonly used for afforestation across North China. We exposed trees to 2 years of 50% rainfall exclusion and found that leaf hydraulic traits conferring drought resistance, including water potential thresholds triggering xylem embolism, leaf pressure-volume characteristics and metrics quantifying the risk of hydraulic dysfunction (i.e., hydraulic safety margin), were not improved, despite slightly but significantly decreased predawn leaf water potential and growth rate. Interspecific variation in response to rainfall exclusion was observed for some morphological traits, yet the adjustments were unlikely to benefit drought resistance. Overall, our results demonstrate an overall lack of physiological adaptive adjustments for leaves in response to rainfall reduction at early growth stage for these trees. If this response persists as trees age, the function of these trees will be potentially reduced due to increased risk of hydraulic failure, if the drying trend continues in their planting region.

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.