中文摘要：

促进叶片衰老是植物激素茉莉酸（JA ）的一个重要生物学功能．在植物体内，JA最初经13-脂氧合酶（Lipoxygenase ，LOX）的作用而形成．RT-PCR发现，在发生衰老的叶片中， LOX3、LOX4、LOX6基因转录发生明显上调，而 LOX2在叶片衰老后期明显下调．构建了拟南芥9-LOX活性缺失突变体 lox1/lox5，利用该材料以亚麻酸为底物测定了拟南芥叶片发育不同阶段13-LOX的活性，发现：与幼嫩叶片相比，衰老叶片中 LOX 活性明显增强．推测LOX3、LOX4、LOX6基因在叶片自然衰老中JA的合成中具有重要作用，而 LOX2基因在衰老后期作用减弱．

英文摘要：

Promotion of leaf senescence is one of the most important function of the phytohormone Jas-monic acid （JA ） .In plants ,JA is initially synthesized by the reaction catalyzed by 13-lipoxygenase （LOX） .Four genes are predicted to encode 13-LOX in A rabidopsis genome ,however ,little is known a-bout their role in JA regulated leaf senescence .Expression pattern analysis by RT-PCR showed that LOX3 ,LOX4 and LOX6 genes expression were significantly enhanced in senescing leaves ,while the ex-pression of LOX2 genes decreased in late stage of leaf senescence dramatically .The 9-LOX activity defi-cient mutant lox1/lox5 was acquired and the 13-LOX activities in leaves at different developmental sta-ges were further measured using linolenic acid as substrate .The activity in senescing leaves was signifi-cantly higher than that in developing young leaves .The results indicated that LOX3 , LOX4 , LOX6 might play important roles in JA synthesis during leaf senescence and the importance of LOX2 might be impaired at the late stage of this process .