title: Activation of carboxylesterases in root cortical parenchymal cells of Pisum sativum during xylem induction in vitro.
abstract: A quantitative cytochemical study of naphthol AS-D esterase activity in explants from roots of Pisum sativum grown on basal medium for 3 or 6 days showed similar levels of activity to those seen in sections of cortex and stele from intact roots of similar ages. Explants grown in the presence of auxins or cytokinin alone showed a threefold or twofold increase in cortical parenchymal activity, respectively. On adding both hormones to initiate xylem element formation, there was also a threefold increase in activity in the cortex. In all three cases, the stimulated activity was totally inhibited by either 10(-4) M diisopropylfluorophosphate (DFP) or 10(-4) M diethyl p-nitrophenylphosphate (E600), indicating carboxylesterase activity. The low level of activity normally present in cortical cells was inhibitor resistant, so indicating acetylesterase activity. Thus, auxins and cytokinins appear to activate mainly similar carboxylesterases during the initiation of xylem elements from cortical parenchyma cells.
mesh_terms: D015084:2,4-Dichlorophenoxyacetic Acid / Q000494:pharmacology; D002265:Carboxylic Ester Hydrolases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D004789:Enzyme Activation; D007210:Indoleacetic Acids / Q000494:pharmacology; D007531:Isoflurophate / Q000494:pharmacology; D007701:Kinetin / Q000494:pharmacology; D063245:Plant Development; D010944:Plants / Q000201:enzymology*
chemical_list: D007210:Indoleacetic Acids; D007531:Isoflurophate; D015084:2,4-Dichlorophenoxyacetic Acid; D002265:Carboxylic Ester Hydrolases; D007701:Kinetin