Cytological Effect of the Herbicide Garlon-4 on Root Mitosis of Allium cepa

Abstract

The effect of the herbicide (Garlon-4) has been studied on root mitosis of Allium cepa (v. Giza-6). It contains triclopyr as an active ingredient and its chemical formula is 3, 5, 6 trichloro-2-pyridinyloxy-acetic acid. Root tips of Allium cepa were treated with a series of concentrations, ranging from 28ppm to 38400ppm for 3, 6, 12 and 24 hours. Examination of the roots was done in permanent root tip squash preparations stained by the Feulgen technique. Garlon affects the relative duration of each mitotic stage as compared with the control. It also caused reduction in mitotic index, indicating mitotic inhibition, and increase in the frequency of abnormal mitoses, the precentages of which are highly significant, except the lowest concentration (28ppm) which had no significant effect after 6 hours and induced a statistically significant percentage of abnormal mitoses from the control after 12 hours of the treatment.
The types of abnormalities induced included: chromosome stickiness, c-metaphase, canaphase, tetraploid and restitution nucleus, star metaphase, laggards, bridges, tripolar, and disturbed meta- and anaphases. Micro- and binucleate cells as well as multinucleated cells at the interphase stage were also observed.
The effect of Garlon-4 on root mitosis simulates that of colchicine in the type of abnormal meta- and anaphases (c-metaphase and c-anaphase) and the induction of polyploid cells as well as accumulation of metaphases.