Tree physiology最新文献

Iron plaque, a phenomenon widely found in wetland plants, is an accumulation of metal (hydr)oxides precipitated on root surfaces primarily driven by rhizosphere oxidation. However, the potential function of iron plaque on plant hypoxia tolerance is largely ignored. Thus, the effects of iron plaque on root O2 dynamics and respiratory metabolism were investigated using the seedlings of Aegiceras corniculatum. O2 microelectrodes were applied to determine partial pressure of oxygen (pO2) within roots, while respiratory metabolism was analyzed using enzyme activity assay kits, transcriptomics, and qRT-PCR. Visible reddish plaques were observed on the roots of field-collected A. corniculatum seedlings, forming a coating that appeared to penetrate the intercellular spaces of the outer 1-2 cell layers. The data further revealed a significant role of iron plaque in elevating pO2 within roots, which can mitigate hypoxic inhibition and benefit plant performance under hypoxic stresses. Compared to non-plaque roots, roots with iron plaque exhibited significantly higher adenosine triphosphate (ATP), elevated tricarboxylic acid (TCA) respiration rates, and upregulated TCA cycle-associated enzymes and genes. Besides, suppressed anaerobic fermentation-associated byproducts (e.g., ethanol) and enzymes/genes (e.g., alcohol dehydrogenase and its encoding gene AcADH1) were simultaneously observed in the roots with iron plaque due to enhanced root internal pO2. Suppressed glycolysis pathway was also observed in the roots with iron plaque, indicating less consumption of carbon resources under hypoxic stresses. In conclusion, this study provided evidence for an interesting link between iron plaque and increased O2 retention within roots, which improved the efficiency of ATP yield through respiratory metabolism.

Traditional cultivation of medicinal Cyclocarya paliurus has consistently failed to resolve the growth-secondary metabolism trade-off, affecting yield and quality. Utilizing dark septate endophyte, which induces host plant endogenous hormone synthesis and enhance stress resistance, offers a feasible and effective method to balance this trade-off relationship. In this study, sterile Cyclocarya paliurus seedlings were subjected to dark septate endophyte inoculation, jasmonic acid spraying, and jasmonic acid inhibitor treatments. We demonstrated that dark septate endophyte inoculation increased seedling height by 59.46% and biomass by 15.94%. This treatment established an antioxidant barrier in plants, maintained reactive oxygen species homeostasis, and alleviated membrane lipid peroxidation, thereby boosting plant stress resistance. ITS gene sequencing confirmed that dark septate endophyte enhanced root fungal diversity. Integrated multi-omics analysis revealed that dark septate endophyte promoted flavonoid biosynthesis (total flavonoids increased by 15.30%) through triggering the jasmonic acid signaling pathway to activate MYC2-mediator complex subunit 25, significantly increasing vitexin content. Our results identify dark septate endophyte as a pivotal metabolic checkpoint for synergistically enhancing medicinal plant yield and quality. This study provides novel insights into eco-efficient cultivation strategies and lays the foundation for the broader application of beneficial dark septate endophyte in agroforestry practices.

Tea plant (Camellia sinensis) is an important thermophilic crop in China. Understanding the cold response mechanisms will be helpful to improve the yield and tea quality against cold stress. Orphan genes, which lack homologs in other lineages, play critical contributions in plant environmental adaptability, yet the characteristics and roles of orphan genes in tea plants, particularly regarding cold tolerance, remain largely unexplored. In the current study, we systematically identified 2,793 orphan genes of tea plant using both genomic and transcriptomic datasets. These orphan genes exhibited simpler gene structures, shorter lengths, fewer introns, higher isoelectric points and lower expression abundance compared with the evolutionarily-conserved genes. We further characterized an orphan gene named CsOG3 that may play roles in tea plant cold resistance. Silencing of CsOG3 reduced the cold tolerance level of tea plant seedlings, while overexpression of CsOG3 significantly enhanced the cold resistance of tobacco and tea plants. By regulatory elements and expression correlation analysis, we identified a cold-induced MYB transcription factor-CsMYB44, which is involved in regulating CsOG3. Functional validation using dual-luciferase reporter and yeast one-hybrid assays reveal that CsMYB44 could bind to the promoter and directly activate the expression of CsOG3. In vivo repression of CsMYB44 also significantly reduced the cold tolerance of tea plants. This report comprehensively presented the architecture of tea plant orphan genes and highlighted the contribution of CsOG3 modulated by CsMYB44 against the cold stress in tea plants, broadening our understanding of plant orphan genes and the contribution in environmental adaptation.

Tree species differ in their ability to use light efficiently, affecting carbon gain, establishment and survival in highly heterogeneous environments. This efficiency relies on the maintenance of the photosynthetic induction state, regulated by structural, biochemical, photochemical and stomatal processes that vary along the leaf economics spectrum (LES). Slow return species, such as shade-tolerant species (often late successional), are thought to sustain higher photosynthetic induction state, while quick return species, like light-demanding species (often early-successional) would have lower shade acclimation and shade-tolerant species lower acclimation to high light. Yet, results often deviate from these predictions. Moreover, most LES traits reflect steady state performance, not dynamic responses. Here, we investigated photosynthetic induction responses in four widely distributed Brazilian tree species representing contrasting successional groups and LES positions, grown under 10% light, 50% light and full sun. We quantified induction dynamics in terms of CO2 assimilation, stomatal conductance, electron transport rate, as well as chlorophyll content, and leaf mass per area (LMA). Acclimation to distinct light environments was assessed using a shade adjustment coefficient and a novel metric based on principal component analysis, relative plasticity (RP). Relative plasticity suggests an asymmetrical bell-shaped relationship with LES position: the slow return Hymenaea courbaril L. showed low plasticity and little change in resource allocation (LMA), photosynthetic rates or induction times; the fast-return Schinus terebinthifolia Raddi displayed moderate plasticity but unexpectedly high shade acclimation, showing high induction state and CO2 assimilation rates; and the intermediate strategists Cecropia pachystachya Trécul and Handroanthus impetiginosus (Mart. ex DC.) Mattos exhibited the highest plasticity, with coordinated increases in LMA, CO2 assimilation, stomatal conductance and photosynthetic induction under increasing light conditions. These findings highlight the importance of integrating photosynthetic dynamics into ecophysiological frameworks for species selection in reforestation, particularly in heterogeneous light environments, where adaptive flexibility can play a critical role on the resilience of an ecosystem.

Phosphorus is an essential element for plant growth, but it is often present in the soil in an insoluble form, such as calcium phosphate (Ca₃(PO₄)₂), which greatly limits the efficiency of plant absorption and utilization. In this study, the endophytic fungus Su100 was found to significantly increase the solubilization efficiency of Ca₃(PO₄)₂ by secreting various organic acids, such as oxaloacetic acid, malic acid and fumaric acid. Transcriptomic analysis revealed that Su100 participated in the up-regulated expression of genes involved in glycolysis and tricarboxylic acid cycling in Ca₃(PO₄) - containing medium, thereby promoting organic acids biosynthesis and improving phosphorus solubilization. Further experiments showed that inoculation with Su100 promoted the growth of sweet cherry rootstock Gisela 6 seedlings under Ca₃(PO₄)₂ conditions. Furthermore, Su100 inoculation also promoted plant sugar and lipid metabolism, with increased expressions of related genes, indicating that Su100 enhanced sugar and lipid supply to support both plant growth and fungal activity. Meanwhile, fatty acid profiling confirmed increased levels of lignoceric acid, palmitic acid, heptadecanoic acid, stearic acid and other components. These results highlight the potential of Su100 as a biofertilizer to improve phosphorus uptake and sweet cherry growth under Ca₃(PO₄)₂ conditions. The study provides new insights into the molecular mechanisms of plant-fungus interactions and their role in sustainable agriculture.

Plant drought tolerance frequently results in growth limitations, which has been known as the trade-off between drought tolerance and growth. Heterosis, the phenotypic superiority of hybrids over their parents in many traits, has yet to be applied to overcoming the trade-off between drought tolerance and growth. Here, we demonstrated that the transgressive expression of expansin proteins (PagEXPs) participated in the vigorous cell expansion and leaf enlargement in hybrid, and this process is correlated with the modulation of auxin transporter (PagPIN8), which is also transgressively upregulated in hybrid leaf. Meanwhile, the transgressive expression of PagP5CS1 in hybrid resulted in higher free proline level in hybrid leaf than both parents and contributed to heterosis in drought tolerance. A new transcription factor PagWRKY45 that regulates the transgressive expression of PagP5CS1 in hybrid leaf was identified and characterized by yeast-one-hybrid screen, which directly regulated the expression of PagP5CS1 by binding the W-box motif in promoter of PagP5CS1. These hub genes work in concert to contributes heterosis of drought tolerance in hybrid leaf. The gene-stacking effect resulting from the co-expression of key genes in growth and tolerance pathways enabling the hybrid poplar to overcomes the trade-off between drought tolerance and growth. An integrative model that synergistically overcomes the classic trade-off between growth and drought tolerance in hybrid poplar was proposed. This model provides a guideline for improving capacity of overcoming the trade-off between drought tolerance and growth via cross breeding and molecular breeding.

Seasonal climate warming affects temperate plant phenology differently. Early winter warming can delay dormancy release and budburst due to insufficient chilling, while late winter or spring warming advances budburst. Additionally, the influence of pre-spring non-structural carbohydrate (NSC) availability on leaf phenology remains poorly understood. We explored the effects of previous late-summer defoliation and winter-spring warming on NSC dynamics and spring leaf phenology in two species: deciduous sessile oak with low chilling sensitivity and evergreen Scots pine with intermediate chilling sensitivity. We observed species-specific responses of leaf phenology to warming and defoliation. Winter warming delayed leaf unfolding in pine but not in oak, likely reflecting the greater chilling requirement of the pine. Defoliation significantly reduced pre-spring NSC levels in twigs and roots of both species, and led to earlier needle emergence in pine, with no impact on oak's leaf out date. Our findings indicate a dual dependency of pine leaf unfolding on temperature and internal carbon reserves, suggesting that defoliation, e.g. through herbivory or diseases, affects the following year's spring phenology and leaf growth in evergreen species but not in deciduous trees. These findings are important for understanding the adaptive strategies of different plant functional types under uneven warming conditions.

The complex architecture and growth cycle of the grapevine (Vitis vinifera) bud presents a knowledge gap in understanding if or how apical dominance regulators apply to the distinct growth patterns of prompt buds, which regularly burst on the shoot, and latent bud, which remain dormant on the cane until the following spring. Tracking the expression of a grapevine homolog of BRANCHED1 (BRC1), a key regulator of axillary bud outgrowth in annuals, may shed light on this knowledge gap. Previous analyses identified a potential grapevine functional homolog VvBRC1 and suggested that BRC1-dependent apical dominance inhibits outgrowth of prompt bud. However, a detailed analysis of the potential participation of VvBRC1 and apical dominance in regulation of latent buds at any stage of complexed growth cycle is still lacking. Here we attempted to investigate whether and when VvBRC1 is involved in controlling bud break of latent buds-both on the shoot during the growing season and on the cane throughout the dormancy cycle. Our data suggest that while the bud-specific VvBRC1 regulates prompt bud outgrowth, (i) it does not regulate outgrowth of latent buds during their development or endodormancy cycle; and (ii) a VvBRC1-regulated apical dominance mechanism may be established among woody buds upon bud activation.

Camellia oleifera has constantly been threatened by drought and insufficient soil nutrients. Our study used RNA sequencing (RNA-Seq) to investigate the molecular responses to nitrogen application under drought conditions. Concurrently, we also analyzed associated leaf functional traits. The results showed that supplemental nitrogen effectively alleviated drought-induced stress in C. oleifera. Fertilization increased leaf chlorophyll and flavonoid concentrations, restored non-structural carbohydrate balance and enhanced antioxidant capacity under drought conditions under drought, thereby enhancing drought resistance. RNA-Seq identified differentially expressed genes predominantly engaged in drought stress response mechanisms such as light harvesting, starch and sucrose metabolic pathways, and flavonoid biosynthesis. Under drought conditions, nitrogen application activated CoHEMA, CoHEMB, CoCHI and CoLAR while repressing CoSGR, CoUFGT, CoSPS and CoInv expression, thereby enhancing chlorophyll content and maintaining flavonoid-sucrose homeostasis to meet the metabolic demands of C. oleifera survival. Co-expression network analysis revealed two highly interconnected modules (pink and blue), primarily enriched in carbon metabolism, nitrogen metabolism and secondary metabolite metabolism. The two modules strongly correlated with opposite effects on physiological indicators. In addition, nitrogen fertilizer treatment identified numerous transcription factors associated with drought response. Heterologous expression in Nicotiana tabacum confirmed that CoWHY1 promoted chlorophyll accumulation by regulating the expression of HEMA1 and SGR. This study provides molecular insights into the impact of soil nutrients on the drought response of C. oleifera foliage, setting the groundwork for nutrient management in economic trees under drought conditions.

Proanthocyanidins (PAs), or condensed tannins, are widespread plant secondary metabolites common in trees. Proanthocyanidins play roles in plant defense and soil nutrient cycling, and have applications in human medicine and diet. Although PA function in plant shoots is well studied, there is less information on the role of PAs in roots. Proanthocyanidins can act as anti-fungal compounds, suggesting PAs in roots could negatively affect beneficial mycorrhizal fungi, and thus nutrient uptake. Poplars (Populus spp.) are known to produce a wide range of phenolic compounds, and for this work a transformable (P. tremula L. x P. tremuloides Michx.) hybrid was utilized. Transgenic lines with high and low tissue PA concentrations were used to test the hypothesis that high root PA levels would impede mycorrhizal colonization, and consequently, nitrogen uptake. Plants were grown in a sandwich tissue culture system allowing co-culture of the mycorrhizal fungi and roots. Plants from each line were inoculated with either the ectomycorrhizal (EcM) fungus Laccaria bicolor (Maire) P.D. Orton or the arbuscular mycorrhizal (AM) fungus Rhizophagus irregularis (Błaszk., Wubet, Renker & Buscot) C. Walker & A. Schüßler, or were kept as a non-inoculated control. Uptake of ammonium and nitrate by plant roots was measured by 15N-labeling. Successful EcM colonization on poplar roots was confirmed in all the plant lines, while no AM structures were observed. The low-PAs/phenolics line was less colonized by EcM fungi. When inoculated with EcM fungi, plants from all lines tended to have lower root PA concentrations. No significant differences in nitrogen uptake among plant lines were observed, but ammonium uptake was greater than nitrate uptake. Results suggest that PA content is reduced during colonization and that phenylpropanoids may play essential roles in establishing ectomycorrhizal symbioses.