Experimental studies on plant metabolism. I. Effects of ammonium sulphate either alone or fortified with phosphorus and carbon sources on respiration and metabolic changes in potato slices

Incubation of potato slices in aerated and non-aerated ammonium sulphate media either alone or fortified with carbon and phosphorus sources induced variable losses in the total carbohydrate content. Whereas the content of reducing sugars was, in general, increased by the differrent treatments, those of starch and sucrose were decreased. In tissues fed with ammonium sulphate + ATP, the losses of starch were higher and those of sucrose were lower than the comparable losses in tissues fed with ammonium sulphate alone. Protein breakdown was operative in all ammonium sulphate media with no carbon source but supplemental addition of glucose led to a marked accumulation of protein-N. Aminoand total soluble-N showed different levels in the different media. It is concluded that ammonium sulphate and glucose independently affected the protein content of the tissues and the fraction of proteins synthesized at the expense of glucose was increased in presence of phosphorus sources. Ammonium sulphate either alone or fortified with ATP caused an initial sharp stimulation followed by marked low rates of C02 production by potato slices. When combined with glucose, ammonium sulphate reduced the high rates of C02 output observed in its absence. This reduction of glucose respiration was overcome by the presence of phosphorus sources. The present results are discussed in relation to the action of ammonium sulphate when used either alone or fortified with phosphorus and carbon sources.