Phytotoxic effects of Croton bonplandianum Baill. on weedy associates

Abstract

Both extract as well as leachate ofCroton bonplandianum leaves before or after washing are detrimental to at least six weedy associates, viz.Calotropis procera, Chrysopogon aciculatus, Crotalaria saltiana, Cynodon dactylon, Eupatorium odoratum andPolygonum orientale. By adding increasing quantities of decaying leaves to soil, phytotoxic activity is greatly enhanced against at leastCrotalaria saltiana, Cynodon dactylon andEvolvulus nummularius. Soil samples collected in and aroundCroton bonplandianum plants during active growth of the species are more toxic to weedy associates than the soil collection made after accumulation of debris ofCroton plants. The weeds that are mostly affected includeChrysopogon aciculatus, Cynodon dactylon, Eupatorium odoratum, Evolvulus nummularius andMikania cordata. Maximum amount of inhibitory compound fromCroton bonplandianum leaves are extractable in ethanol. The ethanol extract, on further analysis, leads to the finding that two active constituents are involved and that these constituents are probably related to abscisic or phaseic acid. The implications of the above results are discussed.