Effects of Sulfite on Metabolism in Isolated Mesophyll Cells from Papaver somniferum

Abstract

Exposure (30 min) of leaf-free mesophyll cells from the C-3 plant, P. somniferum, to concentrations of sulfite (SO2 + HSO3- + SO3=) up to 20 mM stimulated the rate of CO2 incorporation as much as 30%. The sulfite rapidly affects the metabolism of newly incorporated CO2. Ammonia incorporation into glutamine and subsequent transamination reactions were stimulated during the short term exposure periods while glycolate metabolism apparently was inhibited by bisulfite at 2 points in the pathway. The results further indicate that glycolate is the major precursor of glycine in these cells. Prolonged periods of exposure (24 h) to sulfite had somewhat different effects on carbon metabolism: the high concentrations (10-20 mM) severely inhibited all aspects of cellular metabolism while lower concentrations (1 mM) appeared to inhibit ammonia incorporation but stimulated synthesis of sucrose and starch.