Anticytokinin activity of substituted pyrrolo[2,3-d]pyrimidines.
Ten substituted pyrrolo[2,3-d]pyrimidines were tested as cytokinins and anticytokinins in the tobacco bioassay. Eight new anticytokinins were identified and two were found to be highly active. The most potent species were 4-cyclohexylamino- and 4-cyclopentylamino-2-methylthiopyrrolo[2,3-d]pyrimidine, of which 0.05 and 0.009 muM concentrations, respectively, were required to produce detectable inhibition of the growth of tobacco callus cultured on a medium containing 0.003 muM 6-(3-methyl-2-butenylamino)purine. The inhibition of growth by moderate (</=6.6 muM) concentrations of these compounds was reversible by equal or higher concentrations of 6-(3-methyl-2-butenylamino)purine, but not by indole-3-acetic acid or gibberellic acid. These substituted pyrrolo[2,3-d]pyrimidines were also found to enhance bud formation at high cytokinin concentrations, suggesting that a cytokinin may act at more than one cellular site in exerting its growth-promoting and morphogenetic effects.
Institute of Plant Development, University of Wisconsin, Madison, Wisc. 53706.
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Skoog
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Schmitz
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Hecht
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Frye