水分变化对胡杨异形叶性时空变化的调节机制

The heterophylly of Populus euphratica is defined by appearing of heteromorphic leaves regularly at different stages of tree development and different vertical spaces, and the heteromorphic leaves are differ in morphological structure and physiological function. Based on previous studies and our research, we can speculate that the heterophylly of P.euphratica is related to the water supply variation during trees’ development, and it is an adaptive adjustment to water changes. To address this scientific hypothesis, this project study on temporal and spatial characteristics of P.euphratica heteromorphic leaves under different water conditions, the regularity of structural characters, functional traits, anatomical features, and osmotic adjustment ability of heteromorphic leaves at different developmental stages along with changes in leaf shape, and stem and leaf water potential, as well as their mutual relationship, to clarify the influence of water change on the occurrence and distribution of P.euphratica heteromorphic leaves, and the regulating mechanism of coordination of space-time changes among leaf shape, leaf traits, and water potential changes in stem and leaves, as well as the their differences caused by different water conditions. By comparing the difference in the distribution, morphological structure and physiological and biochemical characteristics of P.euphratica heteromorphic leaves at different developmental stages under different water conditions, to reveal the regulation mechanism of water change on the temporal and spatial variation of heteromorphic leaves of P.euphratica. This research will facilitate to a comprehensive understanding of survival strategy for P.euphratica to adapt to environmental water changes based on the biological characteristics of their heteromorphic leaves, and lay a theoretical foundation for the further study on the molecular regulation mechanism of P.euphratica drought adaption.

胡杨的异形叶性表现为各类异形叶在其个体发育的不同阶段以及树冠的不同垂直空间有规律的出现，还表现在它们形态结构和生理功能上的差异。基于本课题组和前人研究我们推测，胡杨的异形叶性可能与其个体发育过程水分供应有关，异形叶性是胡杨适应水分变化的调节形式。针对这一科学假设，本项目拟研究不同水分条件下胡杨异形叶发生的时空特征，以及各发育阶段异形叶结构性状、功能性状、解剖结构特征和渗透调节能力随叶形、茎叶水势变化的规律及其相互关系，阐明水分变化对胡杨异形叶发生分布的影响，以及叶形、叶片各性状、茎叶水势在时空上协同变化的调节机制及其水分条件不同带来的差异。通过比较不同水分条件下异形叶发生分布、异形叶形态结构、生理生化特性在各发育阶段的差异，揭示水分变化对胡杨异形叶性时空变化的调节机制，以期全面了解胡杨以异形叶性的生物学特性适应环境水分变化的生存策略，为进一步研究胡杨适应干旱的分子调控机制奠定理论基础。

本文研究不同水分条件下胡杨和灰杨异形叶结构性状、光合水分生理特性、茎叶解剖结构、异形叶渗透调节能力随胸径、树高、叶形指数和茎叶水势变化的规律及其相互关系，阐明水分变化对胡杨和灰杨异形叶发生分布的影响，以及叶形、叶片各性状在时空上的协同变化。结果如下：.（1）适宜水分条件下胡杨异形叶，叶片宽度、叶面积、栅栏组织厚度等随径阶和取样高度的增加而增加，净光合速率、蒸腾速率和丙二醛含量等也均随径阶、取样高度的增加而增加。异形叶形态结构及生理指标参数在不同径阶和同一径阶不同树冠高度上差异明显，不同径阶的同一树冠高度异形叶形态、结构和生理特征存在差异。.（2）在两种土壤水分条件下，随着树高的增加，胡杨叶面积等呈增加趋势，叶形指数和ABA含量呈减小趋势。异形叶所在树高的增加对土壤适宜水分条件下异形叶形态的影响较大，对土壤干旱条件下异形叶解剖结构、光合能力、生理特性及激素含量的影响相对较大。.（3）适宜水分条件下各径阶灰杨叶面积、主脉维管束面积、叶厚、净光合速率、脯氨酸、内源激素GA3含量等均随树高的增加显著增加，异形叶形态结构及生理特征在各径阶都具有明显的树高梯度差异，叶片形态结构和生理特征随胸径、树高梯度增加表现出更加明显的旱生结构特征和更高的光合能力、水分利用效率及抗旱保水能力。.（4）两种土壤水分条件下，灰杨异形叶光合能力与发育阶段以及异形叶所在的树冠高度有关。在适宜水分条件下，灰杨树冠上部叶片水分环境优于下部；在土壤干旱条件下，灰杨8径阶的水分环境优于16径阶，灰杨高度间生理特性指标存在差异，树冠上部的叶片抗逆性强于下部。.（5）胡杨、灰杨的异形叶随着树高的增加，叶面积等呈增加趋势，与树高呈显著正相关；胡杨、灰杨叶激素IAA分别主要影响着主脉木质部面积和栅栏组织。胡杨IAA通过影响主脉的水分运输效率进而保证正常的光合生理，灰杨IAA通过影响栅栏组织来保证。