Efecto alelopático de Tithonia diversifolia(Asteraceae) sobre una especie modelo

Tithonia diversifolia is native from Mexico and Central America. In Cuba, it is invading several regions. Particularly, it covers a large area in a protected area located at Guamuhaya cordillera: Topes de Collantes. Some authors have referred the allelopathic potential of T. diversifolia as the main factor that makes it so dominant in regions where it is exotic, such as Africa and Thailand. In this sense, we aim to assess the allelopathic potential of T. diversifolia in Cuba, through a target species with high germination and seedling emergence of Lactuca sativa. Three experiments were carried out covering germination and emergence of lettuce and Tithonia's leaves and bracts as source of allelopathic compounds. Germination was not significantly affected by T. diversifolia. Radicle length was enhanced by leaf aqueous leachate, whereas hypocotyl was negatively affected. Leaves and bracts did not exerted significant effects on radicle and hypocotyl growth. Only lettuce radicle was negatively affected by T. diversifolia's leaves. The rhizosphere soil and leaf aqueous leachate on soil did not exert noticeable effects on lettuce emergence. Nonetheless, hypocotyl length was slightly enhanced by rhizosphere soil. Tithonia diversifolia did not show strong allelopathic effects on germination and early growth of lettuce. Instead, it showed contrasting light effects depending on the source of allelochemicals and the specific target.