Cytological Studies in vivo of Picloram, Pyriclor, Trifluralin, 2, 3, 6-TBA, 2, 3, 5, 6-TBA, and Nitralin

Abstract

By means of in vivo observation, the effects on dividing and nondividing staminal hair cells of Tradescantia and stipular cells of Vicia of the following herbicides were investigated: picloram, pyriclor, trifluralin, 2, 3, 6-TBA, 2, 3, 5, 6-TBA, and nitralin.
At high concentrations, picloram and pyriclor cause coagulation of cytoplasm. At low concentrations, they increase cell elongation in both Tradescantia and Vicia.
Trifluralin, 2, 3, 6-TBA and 2, 3, 5, 6-TBA were more toxic to Vicia than to Tradescantia cells. In fact, trifluralin caused a significant increase in final cell lengths compared to the controls, whereas it had little or no effect on elongation of Vicia leaf cells in isolated pieces of tissue.
Nitralin in very low concentrations caused mitotic aberrations similar to those induced by colchicine. These results confirmed earlier studies on fixed material and further demonstrated that ntralin, like CIPC and IPC, was more toxic to Tradescantia, a monocot, than to Vicia, a dicot. Nitralin should prove to be a valuable tool in relating deviations in the normal pattern of mitosis as observed in the light microscope with changes that take place at the ultrastructural and biochemical level.
The effects of picloram, pyriclor and 2, 3, 6-TBA on chloroplast development are discussed.
Malformation and death of plants treated with herbicides must be explained ultimately on the basis of effects on division, growth, and differentiation of individual cells. These effects, in turn, must be understood in terms of the mechanism of action of the herbicide at the molecular level. Explanations of the selective action of herbicides may reside in differences in absorption or translocation between susceptible and nonsusceptible species. But, if the selectivity is based on differences in tolerances to the herbicide at the cellular level, in vivo studies of this nature provide essential information.