西南地区青杨派不同种古杨树对干旱胁迫的生理及分子响应机制研究

Yunnan is located in Yunnan-Guizhou Plateau, coupled with the role of geography, topography and southwest monsoon, showing distinct wet and dry seasons. Therefore, seasonal drought problem is very prominent. Moreover, in recent years, Yunnan continued to suffer from crippling drought, the agricultural production and the whole ecological environment has been damaged dramatically. Due to climate topography, history, economic and cultural reasons, a number of counties in southwest intrinsic contain abundance ancient poplar resources. These rare old trees have survived in the combined effects of multiple environmental and human factors, undergoing a few centuries or even millennia of the natural environment, which has been adapted to the region's climate, soil and other environmental conditions, exhibit higher resistance to adverse environmental, is the most authentic native species. Therefore, they are valuable for afforestation. From three kinds of geographical types, including dry-hot valley type, warm and humid type, cold and wet type, we will select five typical old poplars species respectively, which DBH> 1m, 300-500 yr old, to study the physiological responses under drought stress, reveal its mechanism of adaptation to environmental stress. Furthermore, the project will describe the genetic basis of old poplar resilience drought stress from the molecular level through explorimg the expression level of abiotic stress-related genes in old poplar under drought stress. The results not only provide the basis for screening drought resistance species in the regional ecological environment construction, but also could have profound effects on exploitation and utilization of local old poplar resource .

云南省地处云贵高原主体，受西南季风影响，加之地理位置和地形的作用，干湿季节分明，季节性干旱问题十分突出，而且近年来云南持续遭受严重旱灾，整个生态环境受到重创。由于气候地形、经济及文化等原因，西南地区蕴藏着丰富的古杨树资源。这些珍稀古树是在多个生态环境因子和人为因子的长期综合作用下生存下来的，适应所处地区的气候、土壤等环境条件，抗逆的能力较强，是最地道的乡土树种，在绿化造林上的潜在推广利用价值十分巨大。我们从干热河谷型、温湿型及寒湿型等3种地理类型杨树中分别选取青杨派5种具有代表性的古杨树，研究它们在干旱胁迫下生理差异响应，揭示其对环境胁迫的适应机理；用分子生物学手段，探讨古杨树抗逆相关基因在干旱胁迫下的表达水平，从分子水平阐述古杨树抗逆的遗传基础，尤其是和抗逆相关基因在古杨树抗旱中的调节机制，为该地区生态环境建设中抗旱性较强树种的筛选提供依据，也对乡土古杨树资源的利用及开发产生深远的影响。

云南地处低纬度高原， 地形地貌复杂，气候复杂，干湿季分明，季节性干旱问题十分突出。由于气候地形、文化等原因，西南地区蕴藏着丰富的古杨树资源。这些珍稀古树是在多个生态环境因子长期综合作用下生存下来的，对所处的地理环境形成了独特的适应机制，均具有较强的抗逆能力。因此，我们从干热河谷型、温湿型及寒湿型等3种地理类型杨树中分别选取青杨派5种具有代表性的古杨树为材料，从形态、生理生化、解剖结构以及基因表达层面上揭示其对干旱逆境胁迫的应对策略和适应机理。研究结果表明，干旱胁迫下，干热河谷型三脉青杨叶片的抗氧酶系统反应迅速，温湿型乡城杨、康定杨渗透调节物质大量积累，同时显著提高抗氧酶活性，寒湿型西南杨和藏青杨在干旱胁迫前期渗透调节物质大量积累，后期抗氧酶活性显著增加，总体上，受旱后三脉青杨在细胞受损程度上最轻，而乡城杨较重。不同地理类型的古杨树叶片的光合系统特性对干旱胁迫处理的响应存在显著差异。受旱后，乡城杨、藏青杨叶片净光合速率（Pn）降幅较小，气孔导度（Gs）响应敏感，叶片胞间CO2浓度（Ci）最低，水分利用效率（WUE）提高，表明乡城杨、藏青杨的光合系统相对于其它树种更为稳定，抗逆能力更强。在叶片解剖结构上，受干旱胁迫后，各处理的叶片、栅栏组织及上下表皮厚度均显著增加，同时，藏青杨的海绵组织及康定杨的角质层也显著上升，表明各树种在应对干旱逆境时对自身形态结构的适应策略上存在差异。在基因水平上，研究结果发现干旱胁迫对相关的抗逆基因表达量均产生重要影响。干旱胁迫下，三脉青杨叶片中的SOD基因表达量先升后降，而乡城杨和康定杨则呈一直上升的趋势；三个树种中 lea2 、DDPK2基因表达量变化基本一致，即干旱处理后开始上升，在处理6-8d时达到最高值，随后呈下降趋势。由此表明，三脉青杨在干旱初期SOD基因调控更强，而两外2个树种则是在后期；三个树种叶片中的 lea2 、DDPK2基因均是在干旱中期调控作用更显著。该研究结果阐明了古杨树对逆境胁迫适应的生理生化机制，也为该地区生态环境建设中抗旱性较强树种的筛选提供依据。