胡杨的异形叶性与生长转变的关系及其生理调控机制研究

Heterophylly of populus euphratica is expressed by the regularly appearance of linear leaves, lanceolate, ovate leaves and broadly ovate leaves at the different stages of ontogeny and the different vertical space of crown. In addition ,the flowers often appears on the position where the broad ovate leaves born on the crown. Aims at the key scientific issues that whether there is a correlation between the heterophylly of P.euphratica and its growth transition, this project take P.euphratica individuals at different developmental stages under the same site as the research object, the leaf shape changes in the vertical space of crown of individuals at different developmental stages as contact point, the first occurrence of flower bud as the core, research on the relationship between the occurrence of flower bud, heterophylly and their spatial distribution during the growth transition of P.euphratica and the individual developmental stages,to clarify the time node of flower buds occurrernce and its corresponding heterophylly type; research on the morphology and physiology changes of branches and leaves before and after the occurrence of flower bud, as well as the relationships between the morphology and physiological changes of the branch and leaf and the individual developmental stages, to clarify the morphology and physiology turning point of P.euphratica when it transition to adulthood, though the the time and space overlap analysis of heterophylly morphological and physiological changes transition and the flower buds occurrernce, to reveal the internal relationship between the leaf shape change and growth transition of P.euphratica and its physiological mechanism, to lay the foundation for the further research on the coordinate regulation mechanism of P.euphratica leaf shape changes and flower bud occurrernce from the molecular level.

胡杨的异形叶性表现为条形叶、披针形、卵形到阔卵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。另外发现，树冠上有阔卵形叶着生的部位有花的出现。针对胡杨的异形叶性是否与生长转变存在相关性这一关键科学问题，项目以同一立地条件下不同发育阶段的胡杨为研究对象，以叶形在不同发育阶段个体树冠垂直空间的变化为切入点，以花芽首次发生为核心，研究胡杨生长转变过程异形叶和花芽发生及空间分布规律及其与个体发育阶段的关系，阐明花芽发生的时间节点及其对应的异形叶类型；研究花芽发生前后枝叶形态生理变化规律，以及枝叶形态变化、生理变化和个体发育阶段间的相互关系，阐明胡杨个体发育过程获得开花能力的枝叶形态和生理转折点。通过异形叶形态生理变化的转折与花芽发生在时间空间上的重叠度分析，揭示胡杨叶形变化与生长转变的内在关系及其生理调控机制，为进一步从分子水平上探究胡杨叶形变化和花发生的协同调控机制奠定基础。

（1）胡杨阶段转变过程，枝叶和花芽形态各指标间及其与径级和冠高间存在显著或极显著正/负相关性。枝叶养分、可溶性糖、淀粉和可溶性蛋白、内源激素含量与径级或冠高存在显著或极显著正/负相关性。表明枝叶和花芽形态数量、枝叶养分、可溶性糖、淀粉和可溶性蛋白、内源激素含量随个体发育阶段变化而变化。.（2）叶片养分、可溶性糖、淀粉、可溶性蛋白、GA3、IAA、ZR含量及IAA/ABA、GA3/ABA、ZR/ABA 、ZR/IAA比值与叶形态指标间存在显著/极显著正/负相关，枝条全氮、全磷、有机碳、可溶性糖、淀粉、可溶性蛋白含量、GA3/ABA比值与枝条形态形态指标间存在显著/极显著正/负相关，表明枝叶养分、可溶性糖、淀粉、可溶性蛋白、内源激素含量变化对枝叶形态变化有影响。.（3）胡杨阶段转变过程花和阔卵形叶从4径级开始出现；在4-18径级内花分布区均位于阔卵形叶分布区内，花与阔卵形叶占冠高比例呈极显著正相关。依据花芽出现，胡杨个体发育阶段可分为童期（没有花芽出现的2径级及以下阶段）和成年期（起始于4径级，花芽数量极少的4-8径级阶段，花芽形态数量有明显增加并趋于稳定的10-18径级阶段）4径级是胡杨童期向成年期的转折点，形态和生理上表现为枝条长度、每枝叶片数、枝叶碳氮比、枝叶可溶性蛋白含量显著减少，枝叶ZR/IAA比值、叶片全氮和ZR含量显著增加；10径级是胡杨成年期花芽数显著增加的转折点，形态和生理上表现为叶形指数、叶片IAA含量和IAA/ABA比值含量显著减少，叶柄长、枝条粗度、每枝花芽数、枝条有机碳含量显著增加。在树体发育区上，第2层是胡杨童区向成年区的转折点，形态和生理上表现叶形指数显著减少，枝条淀粉含量显著增加；第4层是胡杨成年区花芽数少到多的转折点，形态和生理上表现为叶面积、叶柄长、每枝花芽数、枝叶有机碳含量、叶片淀粉含量显著增加。胡杨异形叶性与个体发育的阶段转变有关，阔卵形叶出现是胡杨进入生殖生长的形态特征和标志。