中文摘要：

根据东北林区森林凋落物淋洗液中草酸、柠檬酸和苹果酸的浓度范围,用不同浓度的上述3种外源有机酸溶液叶面喷施长白落叶松幼苗,再置于4℃下进行低温胁迫,研究有机酸对低温逆境条件下长白落叶松幼苗多种生理生化指标的影响,探讨低温胁迫下外源有机酸对苗木抗寒性的调控机制。结果表明：适当浓度的3种有机酸均降低低温胁迫后长白落叶松的质膜透性和MDA含量,不同程度提高SOD,POD,APX和CAT等多种抗氧化酶活性及脯氨酸和可溶性蛋白含量,减缓叶绿素的下降趋势。外源有机酸能通过促进长白落叶松体内保护酶活性提高,降低膜脂过氧化程度,增强渗透调节能力和细胞清除活性氧的能力,最终明显提高其低温抵御能力。3种有机酸对上述生理生化特性的影响强弱表现为：柠檬酸〉苹果酸〉草酸,适宜的最佳使用浓度为5.0mmol.L^-1。

英文摘要：

According to the concentration scale of oxalic acid,citric acid and malic acid in forest litter leachates of northeast China,Larix olgensis seedlings were foliar-sprayed with organic acids of different concentrations,and then subjected to low temperature（4 ℃）.Effects of organic acids on physiological and biochemical characteristics of the seedlings were studied to investigate the regulation mechanism of exogenous organic acids on cold resistance of L.olgensis.The results showed that the organic acids of appropriate concentrations decreased electrolytes leakage and MDA content of the seedlings under low temperature stress.Activities of SOD,POD,APX and CAT,and concentrations of praline and soluble protein were enhanced to some extent with treatment of the acids.The chlorophyl contents were also increased.It is concluded that,exogenous organic acids could enhance the protective enzyme activity,reduce membrane lipid peroxidation,and increase osmoregulation and scavenging active oxygen abilities of L.olgensis seedlings under low temperature stress,resulting in an increase in the cold resistance of L.olgensis seedlings.The order of effects of the three organic acids on physiological and biochemical characteristics was：citric acidmalic acidoxalic acid,and the optimum concentration of the organic acid was 5.0 mmol·L^-1.