Ultraviolet-Stimulated KHCO3 Efflux from Rose Cells

Abstract

Suspension-cultured cells of R. damascena that were irradiated with UV light (254 nm, 2.1 .times. 104 J/m2) rapidly lose K+ and HCO3- ions to the medium. If the HCO3- is derived from respiratory CO2 inside the cell, then loss of HCO3- should be accompanied by an acidification of the cytoplasm. Estimates of the pH of control and UV-irradiated cells by 31P-nuclear magnetic resonance spectroscopy indicated that, following irradiation, the pH of both cytoplasm and vacuole dropped by 0.2-0.3 units. This change was not as great as was predicted from the observed HCO3- loss. Analysis of nitrogenous compounds in the cell suggested that reduction of nitrate and synthesis of .gamma.-aminobutyric acid absorbed some of the protons formed by the synthesis and dissociation of bicarbonate.