Potassium Transport in Non-Growing Corn Root Tissue as Affected by IAA and GA_3

概要

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Experiments were done to determine if the spontaneous recovery of non-growing segments of corn root (Zea mays L.) from excision injury is dependent on auxin. Washing the segments with 5 nM indoleacetic acid (IAA) for 2 to 4 hours gave a small but significant increase in K^+ (^<86>Rb) influx, used here as a parameter reflecting recovery of electrogenic H^+-efflux pumping. This promotive effect was obtained only after an hour of washing, and was sustained by 100 nM gibberellic acid (GA_3). Any early responses to auxin were obscured by an adverse reaction of the root cells to external IAA which resulted in a transitory inhibition of H^+ pumping and K^+ influx. Pretreatment of excised root tips with 10 μM IAA in the grinding medium protected a plasmalemma-enriched fraction of the microsomes during isolation, giving increased uncoupler-sensitive ATPase activity. Non-growing root tissue thus shows three responses to auxin: an adverse reaction at the outer surface of the plasmalemma which blocks H^+ pumping; a protective or restorative effect on the H^+-ATPase; an increased capacity for K^+ influx during the developmental phase of washing, which is augmented by the presence of GA_3.
日本植物生理学会の論文