Plant and Cell Physiology · 1967 · 11 citations · 0 references
Life SciencesBotanyPlant SciencesPlant BiochemistryPlant Hormone BiologyPlant PhysiologyAbscisic Acid BiologyPlant EnzymesPlant Hormone PhysiologyPlant Hormone SignalingCell Division ControlDecapitation ResponseMitosis ArrestMitosis RegulationMitosis TransitionMitotic Chromatin CondensationPhytohormone ProductionPhytohormone Regulation
Herbicidal phenylurethanes (phenyl-NH-CO-O-alkyl) and synthetic phytokinins (phenyl-NH-CO-NH-phenyl or 6-N-substituted adenine) produce essentially identical results in a variety of assays. The induction by gibberellic acid of α-amylase formation in barley endosperms is inhibited, as is the decapitation-induced increase in rate of amino acid incorporation by excised hypocotyls of Sesbania exaltata. The loss of chlorophyl in barley leaf disks, and the loss of ability to N-methylate tyramine in barley seedling roots, are prevented or retarded by both phytokinins and phenylurethanes. Both groups of compounds cause severe contraction of mitotic chromosomes and eventually produce granulated interphase nuclei. But phytokinins are known to promote cell division, phenylurethanes to inhibit it. It is postulated that phytokinins at low concentrations permit an essential orderly contraction of chromatin, thus allowing normal mitosis, wherease high concentrations produce abnormal chromatin condensation and thus prevent initiation or completion of RNA transcription from hitherto-inactive genes.