UV-Stimulated K Efflux from Rose Cells: Counterion and Inhibitor Studies

Irradiation of a washed suspension of cultured rose (Rosa damascena var. Gloire de Guilan) cells with about 1,680 joules per square meter of short wave ultraviolet (UV) light (254 nanometers) caused K(+) to appear in the external medium. Short-term tracer ((86)Rb(+)) experiments confirmed the earlier suggestion (Wright, Murphy 1978 Plant Physiol 61: 434-436) that UV increases the efflux of K(+); there was also a small decrease in influx of K(+). There was a partial recovery of fluxes from the effects of UV radiation, but no net accumulation of K(+) within 16 to 18 hours after the irradiation. The K(+) appearing in the medium was matched by an equivalent amount of HCO(3) (-); it was suggested that HCO(3) (-) was the principal counterion for the K(+) flux induced by UV. Inhibitors of ATP synthesis (10(-5) molar carbonyl cyanide m-chlorophenyl hydrazone; 0.05 millimolar KCN plus 0.75 millimolar salicylhydroxamic acid) strongly reduced the UV-stimulated K(+) leakage, suggesting that the leakage was dependent in some way on ATP concentration inside the cells. The UV-induced K(+) leakage was also dependent on temperature and the presence of Ca(2+) in the external medium.