Comparative effects of CGA-92194, cyometrinil, and flurazole on selected metabolic processes of isolated soybean leaf cells

Abstract

The potential adverse phytotoxic effects of the herbicide safeners CGA-92194 {α-[1,3-dioxolan-2-yl-methoxy)imino]benzeneacetonitrile}, cyometrinil [α-(cyanomethoxy)imino-benzeneacetonitrile] and flurazole [phenylmethyl 2-chloro-4-(trifluoromethyl)-5-thiazole-carboxylate] on selected metabolic processes of enzymatically isolated leaf cells of soybean [Glycine max (L.) Merr.] were compared in time- and concentration-course studies. CO₂ fixation, protein synthesis, RNA synthesis, DNA synthesis, and lipid synthesis were assayed by the incorporation of NaH¹⁴CO₃, [¹⁴C]-leucine, [¹⁴C]-uracil, [³H]thymidine, and [¹⁴C]-acetate, respectively, into the isolated cells. CGA-92194 and cyometrinil behaved similarly, and at low concentrations (0.1, 1, and 10 μM) they stimulated rather than inhibited the five metabolic processes assayed, following incubation periods of up to 2 h. At the highest concentration of 100 μM, both safeners inhibited all metabolic processes of the soybean leaf cells but neither compound exhibited rapid and distinct inhibitions as might be expected in the case of inhibition of a primary target site by a potent inhibitor. At low concentrations and early incubation periods (30 and 60 min), flurazole effects on all metabolic processes were also stimulatory rather than inhibitory. However, the stimulation of CO₂ fixation by 0.1 and 1.0 μM was highly significant. At 100 μM flurazole was extremely potent on all metabolic processes of soybean leaf cells examined. At the 2-h incubation period, flurazole also inhibited all metabolic processes at concentrations lower than 100 μM. The sensitivity of the five metabolic processes to flurazole decreased in the following order: photosynthesis = lipid synthesis >DNA synthesis>protein synthesis>RNA synthesis.