Our study examines the enzymatic antioxidant defense of plum plants, through the assessment of the activity of the enzymes peroxidase and catalase in the leaves of different plum tree varieties cultivated under irrigated and non-irrigated conditions during the growing season. The importance of these enzymes lies in their participation, with differentiated roles, in the adaptation and resistance of trees to unfavorable environmental conditions, as well as in the processes of growth, development and fruiting. The results of the investigations revealed an intensification of peroxidase activity in the leaves of trees grown under non-irrigated conditions. Compared to irrigated trees, the values were higher by 24.20 % in the Stanley variety, by 32 % in the Udlinionnaia, by 23.53 % in the President and by 3.17 % in the Super Prezident. During the vegetation period, the highest activity of the catalase enzyme in the leaves was observed in trees grown under non-irrigated conditions. Compared to trees grown under optimal humidity conditions (with irrigation), the enzyme activity was higher by 16.59 % in the Stanley variety, by 19.74 % in the Udlinionnaia variety, by 10.58% in the President variety and by 10.10 % in the Super Prezident variety. The research contributes to the completion of knowledge about the mechanisms of plant tolerance to stress. Understanding these mechanisms could serve as a basis for improving antioxidant defense systems, by further developing procedures for targeted management of the functional state and optimization of the production process in fruit trees in the context of climate change, such as the application of various biologically active substances. The dynamics of the activity of the studied enzymes varied during vegetation, being influenced by the developmental stages of the trees, environmental factors, growth conditions and genotype.