ABSTRACT
This chapter describes the structure-activity relationships and some biological aspects of the urea cytokinins. In any attempt at molecular superposition of different types of cytokinins, the trans structure should be used for the active conformation of the urea cytokinins. N. P. Kefford et al. reported that the substitution of a benzyl group for the phenyl group of N,N'-diphenylureas converts them from active cytokinins to antagonists in the chlorophyll retention bio-assay. The similar structure-relationships between the adenine cytokinins and the urea cytokinins, the similar biological activity characteristic to cytokinins, and the occurrence of a common, highly specific binding protein indicate that the pheny lurea compounds described possess intrinsic cytokinin properties. The research on phenylurea cytokinins originated from the work of Dr. Torigoe supervised by Professor Okamoto and Professor Isogai. Since the early study, the most extensive work was performed by Dr. Takahashi.
