Unidirectional sodium fluxes in red beet storage tissue (Beta vulgaris L. cv. Platronde Egyptische): effects of the phytohormones indol‐3yl‐acetic acid and abscisic acid

Abstract

Abstract. The influence of indol‐3yl‐acetic acid (IAA) and abscisic acid (ABA) on the capacities of the cytoplasm and vacuole and their effects on unidirectional sodium fluxes across the plasmalemma and the tonoplast of aged red beet storage tissue was investigated. After loading the tissue in a labelled NaCl solution the efflux of radio‐activity was measured in unlabelled NaCl. By means of compartmental analysis the capacities and fluxes were determined and compared with those obtained after loading and elution in the presence of IAA or ABA.It was established that both IAA and ABA affect sodium transport across the principal cell membranes. Both hormones inhibited the efflux across the plasma‐lemma, possibly by affecting a Na+ for H+ exchanging system. Efflux across the tonoplast was stimulated by IAA and influx across the same membrane was enhanced by ABA. It was suggested that IAA stimulated a proton pump at this level while the influence of ABA remained difficult to explain.