Changes in Antioxidative Enzymes of Young and Mature Leaves of Tomato Seedlings under Drought Stress

The effects of exogenous abscisic acid (ABA) on antioxidant enzymes of young and mature leaves of 4-week old Lycopersicon esculentum cv. Ailsa Craig and ABA-deficient mutant, notabilis, were investigated under drought stress. Although ABA induced increases in ascorbate peroxidase (APX), glutathione reductase (GR) and catalase (CAT) activities in drought-stressed young leaves of notabilis, CAT activities remained unchanged in both ABA-treated young and mature leaves of Ailsa Craig under drought.Superoxide dismutase (SOD) activity did not substantially increase in notabilis or Ailsa Craig in all treatments. APX activity significantly increased in ABA-, drought- and drought+ABA- treated young leaves of notabilis. These results indicated that the antioxidant enzyme activities in drought-stressed and ABA-treated leaves might change with the production of active oxygen species(AOS) depending on the ABA content, and the developmental stages of leaves might contribute to the differential prevention of oxidative damage in plants exposed to drought.