Abstract: In order to explore the effect of melatonin on drought stress of plant seedlings, this experiment applied different concentrations of melatonin (25, 50, 100, 200 and 400 μmol·L^-1) to the leaf surface of the leaves of Lespedeza davurica ‘Jinnong 1’ under drought stress and measured seedling growth and leaf water physiology. Compared to the drought control, the results showed that application of appropriate concentration of exogenous melatonin could significantly increase the above-ground fresh weight, leaf fresh-to-dry weight ratio, relative water content, soluble sugar, soluble protein and free proline contents of L. davurica (P<0.05), and significantly reduced water saturation deficit (P<0.05), so melatonin could promote the drought resistance of L. davurica at seedling stage. Through the analysis of fuzzy membership function, it was further found that the optimal concentration of exogenous melatonin improving drought resistance of L. davurica seedlings was 100 μmol·L^-1.

Key words: Melatonin, Drought stress, L.davurica, Water physiology, Osmotic adjustment

摘要： 为探究褪黑素对植物苗期干旱胁迫的影响，本试验在干旱胁迫下对'晋农1号’达乌里胡枝子（Lespedeza davurica）叶面施加了不同浓度（25，50，100，200和400 μmol·L^-1）褪黑素，并测定了幼苗生长及叶片水分生理指标。结果显示，与干旱对照组相比，施加适宜浓度的外源褪黑素可显著提高干旱胁迫下达乌里胡枝子的地上部鲜重、叶片鲜干比、叶片相对含水量、可溶性糖、可溶性蛋白和游离脯氨酸含量（P<0.05），并显著降低水分饱和亏（P<0.05），表明褪黑素可提高苗期达乌里胡枝子的抗旱性。通过模糊隶属函数分析进一步发现，提高达乌里胡枝子幼苗抗旱性的外源褪黑素最佳浓度为100 μmol·L^-1。

关键词: 褪黑素, 干旱胁迫, 达乌里胡枝子, 水分生理, 渗透调节