Allelopathic activity and movement of water leachate from Mexican sunflower (Tithonia diversifolia (Hemsl.) A. Gray) leaves in soil.

Abstract

Laboratory experiments were conducted to determine the phytotoxic activ- ity of water leachates from Mexican sun- flower [Tithonia diversifolia (Hemsl.) A. Gray] leaves and the effect of water move- ment on efficacy of the leachate in soil. The water leachates from both the green and senescent leaves applied onto soil inhibited root growth of rice seedlings. The phytotox- icity of leaf leachate depended on the concen- tration of phytotoxic substances which was determined by the amount of leaves extract- ed. Mobility of phytotoxic substances from Mexican sunflower leaves in soil was depend- ent on water movement and soil moisture conditions. More downward movement was observed in dry soil than in wet soil. The inhibitory activity of water leachate in soil was well correlated with the concentration in soil-water. The allelopathic potential of Mexican sunflower leaves in natural field was discussed.