Assessment of allelopathic potential of several phenolic compounds on germination and seedling growth of Eleusine indica (L.) Gaertn. and Lemna minor L

Abstract

A series of single and binary action of allelochemicals were assessed under controlled laboratory conditions by applying the Additive Dose Model on two weed species, Eleusine indica (L.) Gaertn and Lemna minor L. to investigate the potential allelopathic effect of five phenolic compounds (gallic acid, vanillic acid, caffeic acid, coumarin and p-vanillin) and the joint action of phytotoxin mixtures on germination and seedling growth of E. indica and degree of leaf discoloration of L. minor. Dose response curves and ED50 values for single or binary mixture of phenolics, along with possible observed inhibitory action were determined. In dose - response experiments, coumarin and p - vanillin was demonstrated as the most phytotoxic inhibitors on germination and seedling growth of E. indica while caffeic acid and vanillic acid exhibited its strong effect on leaf discoloration of L. minor. The action of binary combination of selected phenolic compounds was found to be more synergistic instead of being additive and antagonistic. The mixture ratios which showed synergistic were 30% coumarin + 70% p-vanillin, 50% coumarin + 50% p-vanillin, 60% coumarin + 40% p-vanillin, 70% coumarin + 30% p-vanillin and 100% coumarin + 0% p-vanillin for germination of E. indica; 0% coumarin + 100% p-vanillin, 30%coumarin + 70%p­ vanillin, 40%coumarin + 60%p-vanillin, 50%coumarin + 50%p-vanillin, 60%coumarin + 40%p-vanillin, 70%coumarin + 30%p-vanillin and 100% coumarin + 0% p-vanillin for root growth of E. indica; 30% coumarin + 70% p-vanillin, 60% coumarin + 40% p-vanillin and 100% coumarin + 0% p-vanillin only for fresh weight of germinated E. indica and 0% vanillic acid + 100% caffeic acid, 30% vanillic acid + 70% caffeic acid, 40% vanillic acid + 60% caffeic acid, 50% vanillic acid + 50% caffeic acid, 60% vanillic acid + 40% caffeic acid and 70% vanillic acid + 30% caffeic acid for leaf discoloration of L. minor. The synergistic action observed could reflect that the mixture compounds may contain different sites of action which interact to form more toxic compound. This study has revealed the potential of phenolic mixture for weed control.