The paper reports the changes of relative plasma membrane permeability and the contents of some osmotic regulation substances such as soluble sugar,soluble protein and proline in leaves and the evaluation of drought resistance of poplar‘2025 ’and its two bud mutation varieties under continuous drought stress of soil.The results showed that with continuous drought stress,the relative plasma membrane permeability all increased obviously,and the‘Quanghong’poplar were always higher than‘Zhonghong’and ‘2025 ’.The total soluble protein and free proline in leaves of the 3 varieties had a tendency to reduce,but the soluble sugar content kept in a higher level.There was a significant positive correlation between the soluble sugar content and the relative plasma membrane permeability(1 >|r|≥0.7 ),which was good for the plants to adapt to drought stress and obtain drought-resistant ability.There was a significant positive correlation between the change of proline content in leaves of poplar‘2025’and the permeability of plasma membrane(1 >|r|≥0.7),and the membrane system was relative stable.There were extremely significant differences between the control group and the treatment group of the 3 varieties(P<0.01 ).It was concluded that the drought resistant ability was poplar ‘2025 ’>‘Zhonghong’>‘Quanhong’by membership function method,and there were no significant difference (P>0. 05) among the 3 varieties.The sensitivity of each index to drought stress was analyzed by the grey correlation method, results showed that the free proline was the main index reflecting the drought resistant ability of 3 poplar varieties.%在土壤持续干旱胁迫下，研究了杨树品种‘2025’及其2个芽变品种‘全红杨’、‘中红杨’当年生嫁接苗叶片的质膜相对透性及渗透调节物质可溶性糖、脯氨酸和可溶性蛋白质含量的变化及关系，并进行了抗旱性评价。结果表明：随干旱胁迫的持续，三者叶片质膜相对透性明显增大，‘全红杨’始终高于‘中红杨’和‘2025’。三者叶片可溶性蛋白质和游离脯氨酸总量有减少的趋势，但可溶性糖含量均能保持在较高的水平，与质膜相对透性成显著正相关（1＞｜r｜≥0.7），这有利于植株适应干旱胁迫和抗旱能力的获得；‘2025’叶片脯氨酸的变化与质膜相对透性呈显著正相关（1＞｜r｜≥0.7），膜系统相对稳定。3个品种各生理指标对照组和处理组均有极显著差异（P＜0.01），经隶属函数法分析得出：抗旱能力为‘2025’＞‘中红杨’＞‘全红杨’，但差异不显著（P＞0.05）；通过灰色关联法分析各指标对干旱胁迫的敏感性可知：游离脯氨酸是反映3个杨树品种抗旱能力的主要指标。
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