Comparative Assessment Of 2,4-D Phytotoxicity On Six Green Manure Plants

Pesticides are widely used in various crops and are associated with environmental impacts. The herbicide 2,4-D, for example, can cause phytotoxicity in different plant species, including leguminous plants that can be used for green manure. In this context, the present research aimed to identify the phytotoxicity of 2,4-D during the initial growth of six terrestrial plant species, including Cajanus cajan, Canavalia ensiformis, Crotalaria juncea, Dolichos lablab, Lupinus albus, and Mucuna pruriens. The studied plants were exposed to different concentrations of 2,4-D (from 0.8 to 4.0 mg kg-1) for 14 days after the germination in control treatments. The endpoints were the germination percentage, the shoot and root lengths, and fresh and dry biomass. Fresh and dry biomass results were interpreted in terms of the Tolerance Index (TI), and the concentrations of 50% inhibition effect (EC50) were calculated for germination and shoot and root length. Four species showed germination above 87.5% for all treatments (EC50 > 4.0 mg kg-1), while this endpoint was below 50% for C. cajan and L. albus at the highest concentrations. The growth of all species was impaired when they were exposed to 2,4-D, with an increase in herbicide concentrations leading to a decrease in the lengths of shoots and roots. The effect on shoot length was more pronounced for L. albus, M. pruriens, and C. cajan (EC50 < 2.0 mg kg-1). The root length inhibition was more evident for C. cajan, C. juncea, L. albus, and D. lablab (EC50 < 1.0 mg kg-1). Swollen roots and yellowing of leaves stood out among the qualitative symptoms of phytotoxicity. Among the tested plants, M. pruriens was the most tolerant (TI > 60% in all treatments), standing out as the species with the most significant potential for green manure in crops during the off-season.