Allelopathic activity of Sesbania rostrata Brem. before black glume weedy (red) rice (Oryza sativa L.).

Phytochemical analyses of leaves, stems roots and seeds of S. rostrata were carried out, and their allelopathic activity against black glume red rice was determined. In all the plant organs, positive reactions with the reagents used for the identification of triterpenes and steroids, alkaloids, flavonoid and saponin were observed. In addition to these similarities, differences in their composition were recorded. The leaves of the plant contained proanthocyanidins and catechins; the stems contained quinones; the seeds contained phenols; the leaves, stems and roots contained reducing sugars, and the roots and seeds contained amine groups. The results of thin layer chromatography confirmed the results of the phytochemical screening and showed the complexity in the composition of leaf and stem extracts. In the allelopathy experiments, all the extracts inhibited the root growth of red rice seedling and coleoptile, with greater effect on the roots. The extract with higher allelopathic effect was that of the leaves, causing a 93% and 82% reduction on the root and coleoptile growth of rice.