Antioxidative Levels in Leaves at the Different Nodal Positions of Cucumber (Cucumis sativus L.)

Abstract

Antioxidative levels in cucumber leaves, attached to different nodes of main stems were determined on plants decapitated at the 21st node. Leaf samples were collected from the 4th, 8th, 12th, 16th and 20th nodes. Chlorophyll content was lowest in the 4th node; it peaked at the 12th node. Protein content in leaves decreased with a descending nodal position from the 16th to the 4th node, while malondialdehyde content increased concurrently. Superoxide dismutase and catalase activities were lower on the basal 4th and 8th leaves. Hydrogen peroxide content was highest in leaves of the 12th node; it decreased successively above and below that position. Ascorbate peroxidase and peroxidase activities in the 8th leaf and in the 4th leaf, respectively, were highest. The antioxidative compounds, ascorbic acid, β-carotene and flavonoids were less concentrated below the 12th node. These results indicate that cucumber leaves have different antioxidant levels depending on the nodal position, and therefore, age.