Fluxes and compartmentation of K(+), Na (+) and Cl (-), and action of auxins in suspension-cultured Petroselinum cells.

Transport of (86)Rb(+)/K(+), (22)Na(+), (36)Cl(-), and [(3)H]indole acetic acid (IAA) has been studied on suspension-cultured cells of the parsley, Petroselinum crispum (Mill) Nym. By compartmental analysis two intracellular compartments of K(+), Na(+), and Cl(-) have been identified and ascribed to the cytoplasm and vacuole; half-times of exchange were around 200 s and 5 h, respectively. According to the Ussing-Teorell flux equation, active transport is required for the influx into the cytoplasm at the plasmalemma (K(+), Cl(-)) and the tonoplast (K(+), Na(+), Cl(-)). The plasmalemma permeability pattern, PK:PNa:PCl=1.00:0.24:0.38, features an increased chloride permeability compared with cells from higher plant tissues. IAA uptake showed an exponential timecourse, was half-maximal after 10 min, and a linear function of the IAA concentration from 10(-9) to 10(-5) M. IAA and 2,4-dichlorophenoxy acetic acid reduce the apparent influx of K(+), Na(+), Cl(-) during the initial 30 min after addition and subsequently accelerate both in- and efflux of these ions. We discuss that auxins could affect the ion fluxes in a complex way, e.g. by protonophorous activity and by control of the hypothetical proton pump.