Regulation of Glutamine Synthetase Level in Isolated Pea Roots. II. The Effect of Exogenously Supplied Acids and Bases in Sugar-supplied and Sugar-starved Roots

Abstract

Summary Exogenously supplied inorganic acids depress GS level in isolated pea roots cultivated in media containing sucrose but do not enhance the decrease in GS level caused by sugar starvation. The negative influence in sugar-supplied roots is not proportional to acid concentration. Bases incl. NH 4 OH counteract the negative effect of acids in sugar-supplied roots as well as the negative effect of NH 4 Cl. When applied alone, NH 4 OH does not influences GS level in sugar-supplied roots differently from KOH with the exception cf low concentrations, however in sugar-starved roots KOH does not affect GS level whereas NH 4 OH enhances the decrease caused by lack of sugar. There is no substantial difference between the effects of NH 4 Cl and (NH 4 ) 2 HPO 4 in sugar-starved roots; both salts significantly enhance the decrease in GS level with the depressing effect being accompanied by a decrease in the content of reducing sugars. These results confirm our earlier finding that the negative effect of ammonium salts of strong inorganic acids is in sugar-supplied roots mediated by increased H + concentration in the cells which counteracts the positive effect of sugars and simultaneously suggest that in sugar starved roots ammonium salts and ammonia enhance the decrease in GS level by enhaning sugar consumption. The results also indicate that some unknown factor(s) with positive effects on GS may be released in pea roots by increased H + concentration.