不同种群羊草幼苗对土壤干旱胁迫的生理生态响应

对干旱条件下三个不同种群羊草叶水势、生物量及其分配格局、生理生化反应进行研究．各种群羊草的生长对轻度干旱胁迫不敏感,重度胁迫下羊草生物量均呈下降趋势,但不同种群变化存在差异．重度胁迫下白音锡勒种群生物量显低于对照和轻度胁迫,而达里湖种群和嘎松山种群与对照、轻度胁迫差异不显．随胁迫强度加大,达里湖种群和嗄松山种群地下部分投入比例增加,白音锡勒种群重度胁迫下地下生物量却显减少．三个种群羊草叶水势变化相似,均随胁迫时间的延长和胁迫强度的加大而下降,但轻度胁迫与对照差异不显,重度胁迫处理第6d迅速下降,第8d降到最低,复水后不同种群羊草水势恢复程度不同．三个种群羊草叶片可溶性蛋白含量、可溶性糖含量、游离脯氨酸含量、MDA含量的变化相似,均随干旱胁迫的加剧而增加,复水后逐渐恢复．嘎松山和白音锡勒种群可溶性糖和脯氨酸含量增加的幅度大于达里湖种群,胁迫条件下达里湖种群羊草叶片的MDA含量高于其它两个种群．

PHYSIO-ECOLOGICAL RESPONSES AND THEIR ADAPTATION OF DIFFERENT GEOGRAPHIC LEYMUS CHINENSIS POPULATIONS TO SOIL DROUGHT STRESS

Water stress effects were studied on three Leyrnus chinensis populations from different geographic locations (Dali lake, Baiyinxile Farm, Gasong Mountain) of the Inner Mongolian Plateau. Seedling were maintained under one well-watered (Control, keeping the soil at field capacity) and two different water deficit conditions (T1, mild stress; T2, severe stress). Leaf water potential, dry matter accumulation and allocation, soluble protein content, soluble sugar content, free proline content and MDA content were measured during the onset of stress and after recovery. No significant population differences in dry matter a ccumulation were detected under control (CK) and mild stress (T1). In severe stress (T2), biomass of Baiyinxile plants decreased significantly compared with CK and T1, while there were no significant differences among the treatments in the other two populations. Root/shoot ratio increased with increased stress levels and stress duration in Dali lake and Gasong mountain populations, but below-ground biomass decreased in Baiyinxile population 'under severe stress. Leaf water potential decreased with stress severity in all three populations, but no significant differences between CK and T1 were found. After 6 days of severe water stress, leaf water potential decreased quickly and the lowest value occurred on the 8th day after treatment. After re-watering, water potentials recovered with varied degrees among three different geographic populations of Leymus chinensis. Soluble protein content, soluble sugar content, free proline content and MDA content all increased with water stress severity and recovered after re-watering in the three populations. Gasong Mountain population and Baiyinxile population showed more accumulation of soluble sugar and free proline, while Dali lake population had higher MDA content than the other two populations under stress conditions.