Herbicidal potential of sweet orange (Citrus sinensis L.) Peel extracts on the germination and seedling growth of coffee senna (Senna occidentalis)

Abstract

This study was carried out to evaluate the effects of sweet orange (Citrus sinensis L.) Peels’ extract on the germination, growth and biochemical parameters of Senna occidentalis (coffee senna). Four concentrations (0, 10, 100 and 1000mg/L) of ethanol, N-buthanol, aqueous, ethyl acetate, chloroform and petroleum ether extracts were applied to petri dishes, each  containing 15 seeds of S. occidentalis in replicates. Parameters such as percentage germination, plumule and radical length were assessed every day, while dry weight and antioxidant enzyme activity were assessed six days after planting. All the extracts at different concentrations showed no significant (P<0.05) effect on percentage germination of S. occidentalis. Lowest percentage germination of 24.47% was observed in chloroform extract at 100mg/L. Radicle and plumule lengths as well as the dry weights of the seedlings of S. occidentalis were greatly reduced by chloroform and ethyl acetate extracts. Biochemical responses in seedlings of S. occidentalis showed increase in peroxidase activity while no significant (P<0.05) increase was observed in the activity of catalase compared to the control. This study suggests that the chloroform extract of orange peel has potential in the development of post emergence bioherbicides for weed control.