升温和氮沉降下川西高原沙棘雌雄植株对干旱胁迫的响应与适应

Western Sichuan Plateau is the one of sensitive zone to global change which brought out environmental changes and had significant impact to local ecosystem. Hippophae shrub which was widely distributed in Western Sichuan Plateau, is the typical vegetation types in the forest steppe ecotone, had important impact to regional flora stability. Hippophae is a dioecious plant, naturally the ratio of male and female individuals maintain 1:1 is good for the continuation of species. However, wild survey had found that the number of female plants was much higher than that in male plants in the forest steppe transition zone. What causes this phenomenon? As a pioneer nitrogen fixing species, is there a gender difference in the root characteristics and whether it is related to the function of the upper leaves? And how does the sex ratio bias change under global change? Thus, in this study, Hippophae rhamnoides L., will be employed as the experimental materials to investigate effects of nitrogen deposition and warming on drought resistance of males and females, the ecophysiological differences of leaves and roots will be studied in male and female plants, to explore the changes in morphological structure, metabolic response, resource utilization strategy, plant-soil ecological petrological relationship. The results will play an important scientific and practical role in the gender differences theory in dioecious plant, and in germplasm resources protection of Hippophae and ecological restoration in degradation region.

川西高原是对全球变化响应较为敏感的区域之一，正面临着诸多环境改变的带来的生态影响。沙棘灌丛林在川西高原分布广泛，为森林-草原过渡带的典型植被类型，对于区域植物群落稳定性具有重要意义。沙棘是雌雄异株植物，自然界中雌雄个体保持1：1的比例有利于维持种群的延续，然而野外调查发现，在森林-草原过渡带雌株的数量远高于雄株，表现出性别比偏雌。这种现象是什么原因引起的？沙棘作为先锋固氮树种，其根特性是否具有性别差异，是否与地上叶功能相关？在全球变化下，沙棘种群性别比偏倚将如何变化？本项目拟以中国沙棘为材料，开展模拟升温和氮沉降下沙棘抗旱性研究，研究雌雄植株地上、地下生长与生理生态特征差异，探讨在形态构建、代谢应答、资源利用策略、植株-土壤生态化学计量学关系等方面的变化规律，为逆境下雌雄异株植物性别比偏倚提供理论解释，也为沙棘种质资源保护和区域退化生态恢复等提供支持。

中国沙棘为胡颓子科沙棘属雌雄异株落叶灌木，广泛分布于我国东北、华北、西北和西南部分地区，具有抗寒旱、耐风沙、对土壤适应性强等特点，作为优良的生态经济固沙树种得到广泛应用。自然界中，雌雄异株植物种群性别比例往往具有一定的偏倚，以杨属植物为模式植物的研究显示，在干旱、盐胁迫、病菌感染、养分匮缺等逆境下，雄株在光合作用、抗氧化、资源利用、细胞亚显微结构等方面显著优于雌株。对中国沙棘而言，在黄土高原地区性别比偏雌，雌株具有更强的适应性和生理调节能力，而在川西卧龙大部分海拔下性别比偏雄，不利环境对雌株的负效应作用更强，表现出在不同区域性别偏倚不同的现象。本研究发现，干旱下雄株叶形态响应更为剧烈，雄株叶片变短变窄，叶面积显著缩小，而雌株光合作用气体交换对干旱的响应更为敏感。干旱下雌雄植株受影响最大的是叶生长，雄株具有较高的根生物量投入。干旱胁迫下雌性和雄性之间有3605个差异表达基因（DEGs），参与了如光合作用、叶绿素生物合成、ABA信号调控过程等，这表明雄性和雌性植物对干旱胁迫的反应可能不同。除此以外，本项目还对中国沙棘雌雄植株开展了氮沉降试验，结果显示氮沉降对叶形态、光合色素、生物量分配等方面的影响也具有性别差异性，氮沉降与干旱具有一定的交互效应。以上结果有利于为逆境下雌雄异株植物性别比偏倚提供理论解释，也可以为进一步的分子调控方面研究打下基础，还能为沙棘种质资源保护和区域退化生态恢复等提供支持。