Allelopathic potential of Tetrapleura tetraptera leaf extracts on early seedling growth of five agricultural crops

Interference of allelochemicals present in some multipurpose trees on growth and development of adjoining crops necessitate the evaluation of the compatibility of the tree with various crops before integration into an agroforestry system. The allelopathic potential of Tetrapleura tetraptera (Schum and Thonn.)Taub, a multipurpose tree, considered as a potential agroforestry species, was examined using aqueous leaf extracts at different concentrations in laboratory bioassays. The extractions were done for 24 h and 48 h durations. The extracts stimulated production of lateral roots in Lycopersicon esculentum Mill. but inhibited it in Abelmoschus esculentum L. The 24 h extract significantly reduced shoot length at 25% concentration and above in Amaranthus spinosus L. while the 48 h extract significantly stimulated it at the same concentrations in L. esculentum and A. esculentum. However, both shoot and root lengths of Capsicum annum L. were significantly inhibited at all extract concentrations up to 79 and 73% respectively. Significant inhibition of root length at almost all concentrations in all the bioassay species showed that root length is a more sensitive indicator of phytotoxic activity. The degree of inhibition increased with increasing concentration of the 24 h extract.