Cytotoxicity of Different Ages of Weed Debris Extract of Ageratum conyzoides (Billy Goat Weed) using Allium cepa L. Assay

Considering the present inhibition of seed germination, reduction in agricultural yields and the unexpected death of plants in the field, an experiment was conducted to evaluate the cytotoxicity of weed debris extract from soaked plants of Ageratum conyzoides (Billy goat weed) on plants using the Allium cepa L. assay. The onion bulbs were first placed in water for 48 hours to initiate root growth, then they were placed in the weed extract got from different soaking periods of all the plant parts of A. conyzoides (which served as the treatments) for 24 hours. Both macroscopic and microscopic parameters show the toxic effect of A. conyzoides. Root length and root number dropped in value with lower soaking period of A. conyzoides. The cells of the 36hrs treatment were charred; those of the 72hrs were not charred, but had their nuclei fallen out of the cells because the cell wall had broken open; while the cells of the 120hrs treatment had intact cells, but with no sign of division. Hence the mitotic index of the treatments could not be ascertained. It was however observed that treatment effect on the cells decreased with increase in soaking period of the weed. This proves that A. conyzoides is allelopathic in nature, and time is required to get rid of its harmful allelochemicals for this weed debris to be useful in enriching the soil.