Differences In Xylem Hydraulic Structure And Drought Resistance Of Dioecious Populus Cathayana To Climate Change

Functional characteristics related to xylem hydraulic structure are key factors influencing plant growth and development as well as environmental adaptation,but the mechanisms by which plants regulate xylem hydraulic structure to adapt to climate change are areas that still need to be investigated in depth.The differences in sexually dimorphic responses exhibited by dioecious plants in different survival environments bring a new dimension to this field.In this study,we systematically investigated the differences in xylem hydraulic structure and adaptation strategies of dioecious Populus cathayana by simulating three climate change environments with increasing drought stress intensity,extreme drought events,and increasing nitrogen deposition,respectively,and the main findings are as follows:(1)Females and males exhibited different water use strategies to adapt to drought stress: females retain more leaf number and leaf area in drought stress and maintain higher water potential for carbon accumulation in moderate water stress;male poplars shed more leaves in drought stress to protect the integrity of xylem water transport function to minimize the adverse effects of drought.The differences in vessel diameter,vessel density and vessel wall thickness were the main reasons for the differences in xylem resistance to embolism in dioecious Populus cathayana.(2)Extreme drought events altered the water use strategy and nonstructural carbohydrate use strategy of dioecious Populus cathayana to some extent to improve the security of xylem water transport: drought-trained plants had lower water potential and stomatal conductance during drought stress;drought-trained plant roots consumed more starch to convert soluble sugars with solute effect to alleviate xylem cavitation embolism.In addition,the stronger carbon partitioning capacity of rehydrated females gave it an advantage in xylem cavitation embolism repair.(3)Nitrogen addition enhanced productivity of dioecious Populus cathayana and significantly affected females more than males in terms of leaf area,water potential,xylem-specific hydraulic conductivity,leaf-specific hydraulic conductivity,and mean vessel diameter.However,the dominance of females in leaf area and vessel diameter caused excessive water loss in drought stress,while greater surface tension in vessel exacerbated xylem cavitation embolism.In addition,males showed greater resistance to embolism due to conservative water use strategies and stable xylem anatomy under the interaction of N addition and drought stress.In summary,there is a degree of plasticity in the xylem hydraulic structural characteristics and regulatory mechanisms of dioecious Populus cathayana adapted to heterogeneous environments,and this plasticity is closely synergistic with the xylem anatomy,while the adoption of different water use strategies between sexes is the key to their survival in stressful environments.The results of the study can help further improve the implementation of dioecious plant management measures in climate change and provide a theoretical basis for the introduction and cultivation of Populus cathayana in different regions,which in turn is expected to improve protective forest degradation and land desertification.