Plant growth inhibitor in the seeds of catchweed.

The substance which inhibits the growth of plants was isolated from catchweed seeds and identified as asperuloside of monoterpene lactone glucoside. The material showed an inhibitory effect on the germination of lettuce seeds and on the lengths of the hypocotyl, radicle and cotyledon in seedlings. Radicle length was most affected.Asperuloside also strongly inhibited the growth of large crabgrass and alfalfa. In white clover and catchweed, however, only an inhibition of germination was noticed but no affect at all on the elongation of hypocotyls, radicles or cotyledons. This substance also showed an inhibitory effect on seedling elongation, particularly of the radicles even in the presence of plant hormones such as GA3, kinetin or IAA.