Experiments were conducted to determine how exogenous abscisic acid (ABA) mediates the tolerance of plants to cadmium (Cd) exposure. Cd stress strongly reduced all the growth parameters of mung bean seedlings. Cd significantly increased ascorbate peroxidase (APX) and catalase (CAT) activities in roots and stems, and peroxidase (POD) activities in roots, stems, and leaves of mung bean seedlings. Cd caused remarkable increases in the levels of leaf chlorophyll and carotenoid, root polyphenols, and malondialdehyde (MDA) and proline in the three organs. However, Cd greatly decreased leaf CAT activity, root and leaf ascorbic acid (AsA) levels, and stem and leaf polyphenol levels. Foliar application of ABA partially alleviated Cd toxicity on the seedlings. ABA could restore most of the changed biochemical parameters caused by Cd, suggesting that ABA played roles in the protection of membrane lipid peroxidation and the modulation of antioxidative defense systems in response to Cd stress. Our results also implied the differential physiological and biochemical responsive patterns of roots, stems, and leaves to Cd and ABA in mung bean seedlings. The great changes in many biochemical parameters in roots suggested that roots were the first to be affected by Cd and play pivotal roles in response to Cd, especially in chelating Cd and reducing Cd absorption.

中文翻译：

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脱落酸调节绿豆幼苗的根，茎和叶对镉胁迫的不同生理和生化响应。

进行实验以确定外源脱落酸（ABA）如何介导植物对镉（Cd）暴露的耐受性。镉胁迫强烈降低了绿豆幼苗的所有生长参数。镉显着提高了绿豆幼苗根和茎中的抗坏血酸过氧化物酶（APX）和过氧化氢酶（CAT）的活性，以及​​根，茎和叶片中过氧化物酶（POD）的活性。镉使三个器官的叶绿素和类胡萝卜素，根多酚以及丙二醛（MDA）和脯氨酸的含量显着增加。但是，Cd大大降低了叶片CAT活性，根和叶抗坏血酸（AsA）水平以及茎和叶多酚水平。叶面喷施ABA可以部分缓解Cd对幼苗的毒性。ABA可以恢复Cd引起的大多数生化参数变化，提示ABA在响应Cd胁迫时在保护膜脂质过氧化和调节抗氧化防御系统中发挥作用。我们的结果还暗示了绿豆幼苗的根，茎和叶对Cd和ABA的不同生理和生化响应模式。根中许多生化参数的巨大变化表明，根首先受Cd影响，并且在对Cd的响应中起关键作用，尤其是在螯合Cd和减少Cd吸收方面。