Changes in Peroxidase and IAA Oxidase Activities in Litchi Leaves under Water Stress

The 2 years old seedlings of two litchi (Litchi chinensis Sonn.) cultivars differing in drought resistance, were used in this study. Chenzi grown in riverside is considered to be drought sensitive, while Dongliu No.1 grown on hills is considered to be drought resistant. Effect of water stress on the activities of cytoplasmic, ionically wall bound and covalently wall bound peroxidase (POD) and IAA oxidase in litchi leaves was studied. The results showed that: (1) The activities of cytoplasmic, ionically wall bound and covealently wall bound POD were 44 20%~44 74%,51 28%~52 15%, and 3 44%~3 65% of the total POD activity, respectively in the leaves. In contrast, the activities of cytoplasmic, ionically wall bound and covealently wall bound IAA oxidase were 88 93%~89 29%,7 32%~7 63%, and 3 39%~3 44% of the total IAA oxidase activity,respectively in the leaves. No significant differences were observed between the two cultivars. (2) Under water stress, the specific activities of cytoplasmic, ionically wall bound and covalently wall bound POD in leaves increased and that the extent of increase was greater in drought resistant cultivar than in drought sensitive one. The results of IAA oxidase were similar.