Metabolism of Siduron by Barley and Crabgrass

At rates as high as 40 lb/A, 1-(2-methylcyclohexyl)-3-phenylurea (siduron) did not reduce the growth of crabgrass (Digitaria spp.) seedlings although it was highly toxic to germinating seeds. Siduron placed at the 2-inch soil depth reduced root growth but not shoot growth of crabgrass. Barley (Hordeum vulgare L., var. Trail) roots, like crabgrass, were more affected than shoots. Carbonyl labeled siduron-14C was absorbed by both barley roots and shoots. Siduron-14C was translocated from roots to shoots but not from shoots to roots. Analysis of the extracts from plants treated at various times revealed that no metabolites of siduron-14C were present. Siduron must be present at the time of seed germination to effectively reduce plant growth.