水力学构造与PIP基因表达对杨树叶导水阻力的调控机制

Soil water shortage is the key limiting factor of forestry ecosystem productivity in semi-arid regions of north China. Plant gas exchange and water transport are known to be linked through stomatal regulation in leaves. But the adaptation mechanism of leaf hydraulic architecture and hydraulic resistance during drought is still unclear. This study plans to use cuttings of typical Populus species as experimental material. By investigating the changes of important leaf traits such as hydraulic architecture among species during drought, the correlations that link leaf hydraulics with gas exchange and leaf structure will be determined. The role of hydraulic architecture such as xylem structure in long-term determined hydraulic resistance regulation could be identified with more details. Effects of aquaporin gating on leaf vein resistance and whole leaf resistance will be determined with HgCl2 as an inhibitor. The relationships between the expression of PIP genes and hydraulic features in leaves will also be investigated during drought and re-watering, to determine the role of aquaporin in short-term regulation of leaf hydraulic resistance. At last, the data of hydraulic driving force, stomatal resistance, and leaf inner resistance will be comprehensively analyzed to reveal the regulation mechanism of leaf hydraulic resistance system. Results could be helpful to understand the physiological basics of water transport processes in leaves, and to clarify the limitation mechanisms of forestry ecosystem productivity by drought in semi-arid regions.

土壤水分不足是我国北方半干旱地区森林生产力提高的主要限制因子。叶器官是联系树木水分消耗和光合固碳的关键部位，但干旱下叶导水阻力的调节适应机制尚不清楚。本项目拟利用不同类型杨树盆栽幼苗为研究材料，通过分析长期干旱下功能叶水力学构造等关键功能性状的适应变化，并比较其种间差异，揭示叶关键功能性状与叶导水阻力间的内在联系，明确导管结构、叶脉密度等水力构造参数对叶导水阻力的“长期粗调”作用；通过研究水通道蛋白(AQP)功能活性对整叶阻力和叶脉阻力的影响，以及干旱及复水下叶质膜水通道蛋白基因(PIP)表达调控与叶导水阻力变化之间关系，明确PIP基因表达和功能在叶导水阻力“短期微调”中的作用；综合分析叶导水驱动力、气孔阻力和叶内水流阻力调节过程，初步阐明杨树叶导水阻力系统的调控机制。研究结果将有助于深入理解植物叶器官水分输导与调控基本生理过程，并为阐明半干旱地区杨树人工林生产力的形成机制提供理论依据。

土壤干旱是限制中国“三北”地区杨树人工林生产力和生态效益的重要因素，深入研究杨树叶片水分运输和光合等功能性状与干旱环境的关系，对阐明杨树高效用水的生物学机制、指导“三北”地区杨树人工林造林实践具有重要意义。本项目以不同抗旱性和生长速率的杨树无性系为研究对象，探讨了土壤干旱条件下杨树存活生长的水-碳-氮耦合机制，明确了影响杨树叶片水分高效利用的重要因素。研究发现：（1）长期土壤干旱下群众杨和碧玉杨的植株生长减缓、叶片变小而厚、叶脉密度(Dvein)增加、叶和根系导水能力显著下降。干旱下群众杨功能叶的Vcmax变化不大，而Pnmax显著降低，而碧玉杨的Vcmax和Pnmax均显著降低。干旱下2种杨树叶脉密度增加可能与其瞬时和长期水分利用效率降低有关，杨树可能主要以避旱机制适应干旱环境。（2）18种杨树无性系在年生长量、叶经济性状、Dvein、叶δ13C值等方面存在显著的种间差异，但生长量与叶面积、LMA、Narea等经济性状间并无显著的相关关系。白杨和青杨派有关无性系的Dvein一般较小，而黑杨背景的杂交杨无性系的Dvein较大。Dvein和δ13C值存在显著负相关，即随着Dvein增加叶片长期水分利用效率有降低趋势。（3）2025杨、中红杨、全红杨和金红杨一年生扦插苗的生长指标均依次显著降低，而叶器官中的干物质分配比例却逐渐增加。中红杨、全红杨和金红杨功能叶的光合碳同化和水分利用能力均逐渐降低，但三者的形成原因及光合生理适应机制并不相同。（4）质膜水通道蛋白（PIP）中的一些成员可能在调节叶肉细胞导度（gm）中发挥关键性作用。我们从速生杨84K中克隆得到2个PIP1;2基因，其可能具有运输CO2的生理功能，构建了其过表达载体并导入农杆菌中，为获得过表达该基因的杨树转基因材料及深入研究PIP1;2基因调节杨树叶片水分利用效率提供研究基础。

内容获取失败，请点击重试