MODE OF ACTION OF HERBICIDES THAT AFFECT CELL DIVISION

Abstract

Sustained growth of plant seedlings requires a constant supply of new cells generated by cell division in the meristematic tissue of roots and shoots. Many herbicides, particularly those that are applied to the soil before weed emergence, affect plant growth by interfering with cell division. Herbicides influence cell division in two ways. In the first, mitotic cells are totally absent in the herbicide treated meristem, thus the overall effect is an inhibition of cell division. In the second, mitotic cells are present after herbicide treatment, but they are abnormal, thus cell division is disrupted. An inhibition of cell division is usually a secondary manifestation of a herbicide induced metabolic change in the plant. Metabolic changes most commonly associated with inhibition of cell division are RNA, DNA, and protein synthesis inhibition or effects on energy metabolism. Disruption of cell division is usually caused by a primary effect on the mitotic spindle apparatus. Herbicides can prevent spindle formation (e.g. trifluralin) or can disrupt spindle function (e.g. propham).