Allelopathic effect by aqueous extracts of different parts of Croton bonplandianum Baill. on some crop and weed plants

Abstract

The present study was conducted to investigate the allelopathic effects of Croton bonplandianum weed on seed germination and seedling growth of crop plants (Triticum aestivum L., Brassica oleracea var. botrytis L. and Brassica rapa L.) and weed plants (Melilotus alba Medik., Vicia sativa L. and Medicago hispida Gaertn). Root, stem and leaf aqueous extracts of Croton at 0.5, 1.0, 2.0 and 4.0% concentrations were applied to determine their effect on seed germination and seedling growth of test plants under laboratory conditions. The aqueous extracts from root, stem and leaf had no effect on seed germination of test plants. The extracts from stem had a stimulatory effect on the shoot length at all concentration levels, as against an inhibitory effect of leaf extracts. Stem extracts at low concentration generally promoted root length but aqueous extracts from leaf and root inhibited root length and dry weight. Root length, shoot length of weed species decreased progressively when plants were exposed to increasing concentration (0.5, 1, 2 and 4%). The pH, osmotic potential and total phenolic contents, the osmotic potential and phenolic content increased with increasing concentrations of aqueous extracts of different parts of C. bonplandianum while pH does not have any major change. Key words: Allelopathy, aqueous leaf extract, aqueous stem extract, aqueous root extract, Melilotus alba, Medicago hispida, Vicia sativa, Croton bonplandianum.