Effect of pretilachlor and fenclorim on carbohydrate and protein formation in relation to their persistence in rice

The persistence of pretilachlor applied to rice singly or in combination with the safener fenclorim was investigated in connection with starch, glucose and protein formation. The addition of fenclorim to pretilachlor did not reduce the accumulation of the latter, but reduced its persistence in rice shoots, while the presence of pretilachlor did not affect the persistence of fenclorim, but significantly increased its accumulation in the shoots. Therefore the safening effect of fenclorim consisted of a more rapid detoxification of pretilachlor. Over the period of pretilachlor and fenclorim detoxification, decreases in starch content, partially counterbalanced by increases of free glucose, and decreases in total protein content were observed in pretilachlor-treated shoots; decreases in both starch and free glucose, as well as in total protein content, were observed in fenclorim -treated shoots compared with the untreated controls. The decreases in starch and total glucose appeared to be a direct consequence of reduced glucokinase and ribulose-1,5-bisphosphate carboxylase activity, and the decrease in total protein an indirect consequence of reduced glutamine synthetase and glutamate synthase activity, in response to pretilachlor and fenclorim treatments.