Potassium transport in Actinidia deliciosa calluses cultured in the presence of 3-O-methylglucose

Calluses of Actinjdia dsliciosa were grown for successive subcultures on Gamborg B5 medium supplemented with l0 g/l. sucrose and 40 g/l. 3- 0 - melhylglucose (MEG). MEG was absorbed with a kinetics similar to that of glucose; its concenrration in the tissue rose quickly to a value similar to that of tbc medium. A tropilic utilization of MEG was excluded because no degradation to CO2 .was observed, even if some metabolization of MEG look piace in the; calluses, as suggested by the finding data, when 144C-MEG was administered to the callus,, about haif of the ratdioactiivity was incorporated into a more polar than MEG. not phosphorilated compound. Calluses grown in MEG showed water osmotic potenlials more negative than those of the contro!, togheter with higher organic osmolyte (sucrose and amino acids) conlents, while no change in malate and gIucosc-6-phosphate levels was observed. 31p_ NMR shows that in MEG there was a grueat l incruse in a phosphorylated mtabolile with a chemical shift similar to that of monophosphoesters Altbough. far its permeabilily, MEG cannot be considered a classic osmotic agent. il induces metabolic changes similar to those described for 0smotic adaptation. The dala suggest thal the observed adaptations might be due to a physical or rnelabolic effect of MEG not linked to difference between cell and medium 05motjc potential.