The allelopathic effects of dry and fresh aqueous leaf extracts of Mangifera indica at 5, 10, 15 and 20% were investigated on the seed germination percentage and seedling growth rate of Cassia occidentalis seeds in a greenhouse experiment. Both dry and fresh leaf extracts exhibited different degrees of inhibition in C. occidentalis germination percentage and growth rate of seedlings at varying concentration. Dry leaf extract at 15 and 20% completely inhibited the emergence of C. occidentalis while the aqueous fresh leaf extract at these concentrations yielded some degree of seed germination and growth rate. The seedling radicle and plumule length were adversely affected as the treatment level increases in both extracts. The concentration dependent responses of C. occidentalis to both dry and fresh leaf extracts confirmed that both extracts contain allelochemicals which are likely to be phenolic compounds. On the basis of overall toxicity potency of M. indicaleaves, our result showed that 15 and 20% dry leaf extract exerted the highest germination percentage and growth inhibition on C. occidentalis seeds. The result from our study suggests that compounds from M. indicaleaves especially the dry ones possess a strong phytotoxic potential and can serve as lead molecules for the synthesis of bioherbicides.
Key words: Allelochemicals, phytotoxic, radicle, growth inhibition, bioherbicides.
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