Published online by Cambridge University Press: 12 June 2017
Inhibition of seedling growth and four assays for inhibition of photosynthesis were used to compare karbutilate [tert-butylcarbamic acid ester with 3-(m-hydroxyphenyl)-1,1-dimethylurea] with derivatives of karbutilate in which either the urea or carbamate side chain was missing. Karbutilate was a more potent, more presistent, and more specific inhibitor of photosynthesis than the phenylurea derivative fenuron (1,1-dimethyl-3-phenylurea) that would be formed by removal of the carbamate side chain. However, karbutilate did not exert the growth-inhibiting action observed for the alkyl carbamate derivative phenyl-N-tert-butylcarbamate, formed by removal of the urea side chain, which does not affect photosynthesis at concentrations below 10-3 M.