Abstract:The leaves of cucumber (Cucumis sativus) seedlings were sprayed with 0.1 % - 0.6% thiodan, and after 4 days the contents of total chlorophyll, chlorophyll a, chlorophyll b,protochlorophyll and carotenoids were decreased by 21 .00% - 38.57%, 21 .27% - 38.69%, 20.22% - 38.24%, 6.60% - 49.24% and 13.54% - 68.85%, respectively. Thiodan at 0.1% -0.6% concentrations caused the promotion of chlorophyllase activity by 16.51 % - 72.80%, and decreased the activities of δ-aminolevulinate synthase and δ -aminolevulinat...