Tree physiology最新文献

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.

Drought-induced tree mortality and dieback is expected to become an increasingly significant issue as climate change increases the frequency, severity and duration of droughts. The primary proposed mechanism of drought-induced decline is hydraulic failure, which is mechanistically linked to xylem architecture. However, annual variation of xylem anatomical traits has largely been overlooked as a possible driver of tree decline, with a focus instead on traditional ring-width based dendrochronological methods. Here, we employ a quantitative wood anatomy approach to examine whether differences in xylem vessel lumen area were related to decline risk during a recent drought-induced decline of chestnut oak (Quercus prinus) from Southern Indiana, USA. Our results show that over at least the past 60 years, healthy trees built consistently wider vessels than those that succumbed. This phenomenon has now been observed across three continents, and in both tracheid- and vessel-bearing species, indicating that conduit size may be related to drought survival, likely as an indicator of long-term stress. Moreover, an analysis of the sensitivity of vessel lumen area to climate variables suggests that early winter warming may promote the production of wider vessels in the following year. In contrast, a negative correlation between prior year growing season length and vessel lumen area suggests that extended growing seasons may lead to narrower, potentially more vulnerable xylem vessels. These effects were less pronounced in the declining trees, hinting that already-stressed trees were less sensitive or physiologically unable to respond to climatic variability. Designing studies aimed at understanding the drivers of intra-specific variation in xylem conduit architecture could improve our ability to predict tree dieback and mortality under future climate scenarios.

Water uptake and distribution are critical for drought recovery, yet previous drought conditions have been shown to impair water transport by affecting soil-root contact and xylem conductivity. In order to investigate these dynamics, the approach of applying δ2H-labeled water as a controlled irrigation was adopted, with this irrigation being administered to a mixed stand of mature European beech (Fagus sylvatica (L.)) and Norway spruce (Picea abies Karst. (L)) trees in control (CO) and throughfall exclusion (TE) plots following 5 years of experimental summer drought. The δ2H concentrations were measured in soil, stem, twig and leaf water before and after rewetting to assess water pool turnover. The labeled water infiltrated the upper 70 cm of soil in both treatments within 48 h. However, a notable delay in water uptake and distribution was exhibited by TE trees in comparison with CO trees, where the label was detected in stems and leaves within 24 h. The TE beech demonstrated water uptake after 4 days, while TE spruce exhibited a more pronounced delay of 7 days. Despite this delay, TE trees exhibited a higher turnover of stem water pools (>75%) compared with CO trees (<50%), while leaf water turnover remained similar between treatments. The delayed uptake in TE trees may be attributed to fine root loss in both species and the suberization of surviving fine roots in spruce, which likely reduced water absorption efficiency. Additionally, the depleted stem water reserves in TE spruce may have delayed internal redistribution. These findings underscore the importance of considering species-specific recovery dynamics and provide valuable insights into the long-term impacts of drought on tree water relations.

Root and leaf traits are expected to converge on the plant economics spectrum (PES). Some studies have focused on correlation between specific root length (SRL) and specific leaf area (SLA), which reflect resource acquisition per invested mass in root and leaf, respectively. However, the results have been inconsistent amongst previous studies. We hypothesized that this discrepancy was due to overlooked variations in root traits depending on mycorrhizal types because SRL can be influenced by not only PES but also mycorrhizal types. To assess how mycorrhizal type inherently mediates the coordination of root and leaf traits, we determined the leaf and root traits of current-year seedlings of 33 species encompassing different leaf habits and mycorrhizal types, AM (arbuscular mycorrhizal) and ECM (ectomycorrhizal) species, grown under a common condition. Root and leaf traits correlated with the first axis of the principal component analysis, and this axis represented PES. Root diameter (RD) also correlated with the second axis, which differed between mycorrhizal types. Specific root length (SRL) and SLA were correlated positively to each other, but ECM species had higher SRL than AM species when compared at the same SLA. This was because (i) SRL is negatively related to root tissue density (RTD) and RD, (ii) RTD was negatively correlated with SLA and (iii) RD was smaller in ECM. Leaf and root traits are tightly coordinated with each other across species, but the relationship shifts between the mycorrhizal types.

Climate change is intensifying drought conditions in the Eastern Mediterranean, posing a significant threat to its unique forest ecosystems. While residual water loss from leaves (i.e., minimal leaf conductivity) after stomatal closure has been identified to play an important role in drought susceptibility across different tree species worldwide, the role of bark as an additional source of residual transpiration (i.e., bark conductivity-gbark) still remains largely underexplored. This study investigates gbark and bark structural traits in two co-occurring Mediterranean pine species, Pinus brutia Ten. and P. nigra Arnold, in Cyprus. Since P. brutia typically occurs in hotter and drier areas, we expected a lower gbark associated with thicker outer bark. Contrary to our initial hypothesis, P. brutia exhibited significantly higher gbark and thinner outer bark than P. nigra on branches of similar diameter (~1 cm). Along with its higher gbark, P. brutia also showed traits associated with an acquisitive growth strategy, including thicker inner bark and potentially greater bark photosynthetic capacity. Contrary to species-specific relationships, gbark showed a negative relationship with outer bark thickness across the species level. These findings suggest that bark structure and function are intricately linked to species-specific growth strategies.