PEROXIDIZING PHYTOTOXIC ACTIVITY OF 1,3,4-THIADIAZOLIDINE-2-THIONES AND 1,2,4-TRIAZOLIDINE-3,5-DITHIONES

Using autotrophic Scenedesmus acutus cells incubated in the light and Echinochloa utilis culture, a series of isomeric compounds, namely 3,4 -tetramethylene-1,3,4-thiadiazoiidine-2-thiones (thiadiazolidine-thion es) and ,2-tetramethylene-1,2,4-triazolidine-3,5-dithiones (triazolidi ne-dithiones), were assayed with respect to growth inhibition, decreas e of chlorophyll contents, protoporphyrin-IX accumulation and light-in duced ethane formation level. The both types of phytotoxic compounds d ecreased chlorophyll contents, caused protoporphyrin-IX accumulation a nd ethane evolution, and inhibited growth of Scenedesmus cells. They i nhibited also protoporphyrinogen-IX oxidase, which led to rapid accumu lation of protoporphyrin-IX, an intermediate of chlorophyll biosynthes is, just like peroxidizing herbicides such as p-nitrodiphenyl ethers a nd cyclic imides. Our comparative data on different sets of the aforem entioned parameters suggest that both the thiadiazolidine-thiones and triazolidine-dithiones are grouped as peroxidizing herbicides, affecti ng a crucial enzyme in the chlorophyll biosynthesis and inducing ethan e formation by cell membrane destruction.