EFFECTS OF ISOXABEN ON SENSITIVE AND TOLERANT PLANT-CELL CULTURES .2. CELLULAR ALTERATIONS AND INHIBITION OF THE SYNTHESIS OF ACID-INSOLUBLE CELL-WALL MATERIAL

The herbicide isoxaben is selectively phytotoxic to dicotyledonous plants, whereas most monocots are tolerant. We previously selected a soybean cell culture tolerant to isoxaben. Some effects of the herbicide on wild-type soybean cells, tolerant soybean cells, and wheat cells were compared. Cytological observations showed that isoxaben induced some disorganization of sensitive soybean cells, especially at the plasma membrane-cell wall interface. Tolerant soybean cells appeared normal in the presence of isoxaben. The growth of wild-type soybean cells was roughly equally sensitive to isoxaben as to dichlobenil, a cellulose synthesis inhibitor. By comparison, the selected soybean line and a wheat cell culture were less sensitive to isoxaben than to dichlobenil. Glucose incorporation into acid-insoluble cell wall material was more inhibited by isoxaben than by dichlobenil in the wild-type soybean cell culture. In the tolerant soybean cell culture, the incorporation was slightly inhibited by isoxaben, but remained sensitive to dichlobenil. In the wheat cell culture, dichlobenil was also more inhibitory but only at high concentrations. Other compounds, inhibitors of cellulose biosynthesis, of glycosylation of lipids or protein, or of cell division, either had no effect on the synthesis of acid-insoluble cell wall material or exerted apparently unspecific inhibitions. The results are consistent with isoxaben inhibiting the synthesis of a cell wall polysaccharide, which could be cellulose. © 1991.