Comparative effects of methazole and two of its degradation products in plants on the metabolism of enzymatically isolated leaf cells of velvetleaf (Abutilon theophrasti Medic)

Abstract

Effects of methazole [2-(3,4-dichlorophenyl)-4-methyl-1,2,4-oxadiazolidine-3,5-dione] and of its plant degradation products, DCPMU [3-(3,4-dichlorophenyl)-1-methylurea] and DCPU [3-(3,4-dichlorophenyl)urea], on photosynthesis, protein synthesis, ribonucleic acid (RNA) synthesis, and lipid synthesis of enzymatically isolated leaf cells of velvetleaf (Abutilon theophrasti Medic) were compared. Photosynthesis and protein, RNA, and lipid synthesis were assayed by the incorporation of NaH¹⁴CO₃, [¹⁴C]-leucine, [¹⁴C]-uracil, and [¹⁴C]-acetate, respectively, into the isolated cells. Time-course and concentration studies included incubation times of 30, 60, and 120 min and concentrations of 0.1, 1, 10, and 100 μM of all three chemicals. DCPMU was a more potent inhibitor of the four metabolic processes examined than either the parent herbicide methazole or DCPU. The sensitivity of the four metabolic processes to DCPMU decreased in the order: photosynthesis>lipid>RNA >protein synthesis. Inhibition of all metabolic processes by methazole was time-dependent, increasing in magnitude with concomitant increases in incubation time. It is probable that the observed effects of methazole were caused by DCPMU, formed through metabolism of methazole by the isolated leaf cells of velvetleaf rather than by methazole itself. DCPU was less active than the parent herbicide methazole and DCPMU and seems to be a terminal metabolite of methazole with limited phytotoxicity.