UV-Stimulated K+ Efflux from Rose Cells

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Abstract
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 (86Rb+) 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 HCO3−; it was suggested that HCO3− 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 Ca2+ in the external medium.