Allelopathic potential of bract leachates of Bougainvillea spectabilis against Cosmos bipinnatus and Ipomoea marginata. Pawar, K.B. and Rawal, A.V. (India)

Bougainvillea spectabilis is a common ornamental plant. It is planted in home gardens, for fencing purpose and along road sides. There is frequent shedding of floral bracts of this plant. An attempt has been made to study the influence of leachates of both red and white bracts on seed germination, seedling growth and pigment content of common flowering plant Cosmos bipinnatus. In Petri plate bioassays, complete inhibition of seed germination and seedling growth with respect to root and shoot lengths, was observed due to leachate (20%) of both red and white bracts. In soil bioassays, seed germination and seedling growth of C. bipinnatus were also reduced due to leachate (diluted at 2%) of red and white bracts. Leachate from white bracts caused more inhibitory effects than red ones. Thus, the influence of leachate of white bract was also assessed for its effect on germination and seedling growth of bindweed Ipomoea marginata. Seed germination and seedling growth, as estimated by root and shoot lengths, were reduced due to leachate of white bracts (20%) in both Petri plate and soil bioassays. Pigment content in both C. bipinnatus and I. marginata had increased due to treatments based on leachates of red and white bracts. This study has been continued to carry out phytochemical analysis of leachates to find out which compounds are responsible for such alterations and whether these compounds can be exploited for the management of weeds. Inhibition in germination potential and seedling growth of both C.bipinnatus and I. marginata may be due to synergistic effect of phytochemicals present in leachates of red and white bracts of B. spectabilis.