Influence of Abscisic Acid on Phosphorus Metabolism and Respiration in Potato Tuber Discs. Comparison with the Cycloheximide Effect

Ageing of discs of potato tuber by incubation in an aerated medium, produces an increase in the rates of respiration and of phosphate uptake. The presence of cycloheximide (CHM) or abscisic acid (ABA) in the uptake medium, does not change uptake by fresh tissue over 3–4 h. On the other hand, CHM causes an inhibition of the rate of uptake by aged tissue although ABA does not. The addition of CHM or ABA to the ageing medium, prevents totally (CHM) or only partially (ABA) the increase in phosphate uptake. The analysis of ³²P-incorporation into the various phosphorylated fractions after 24 h of ageing with CHM or ABA show that CHM induces a large inhibition of the rate of uptake with an almost complete inhibition of ³²P-incorporation into the various phosphorylated fractions. By contrast, ABA produces equal inhibition of ³²P labelling of all fractions including all acid-soluble components. CHM prevents the increase in the rate of respiration, whereas ABA causes a slight stimulation. In both cases, no important effect on ATP content was observed. These results are discussed in terms of a comparison of ABA and CHM actions. They lead to the hypothesis of a specific effect of ABA on the development of the uptake mechanism.