Sequential development of the ion uptake capacity in ageing potato tubers

Abstract

The development of the uptake capacity for different cations and anions was studied in ageing potato tuber discs. Na⁺, Rb⁺ and Fe²⁺ showed no lag period; leucine, 2–3 h; K⁺, HPO₄ ^2‐, SO₄ ^2‐, 9–10 h; Cl^‐, 35–39 h lag. When uptake was carried out with potato discs previously aged in water the lag period disappeared. Cycloheximide (5 10^‐2 M), added to potato discs before ageing, strongly inhibited the development of the uptake capacity for SO₄ ^2‐, K⁺, HPO₄ ^2‐, Cl^‐, leucine, and to a lesser extent that of Rb and Fe²⁺, while it stimulated that of Na⁺ The same effect was produced by CH on aged potato discs. Methionine, which was shown to inhibit sulfate uptake, inhibited also Cl^‐ and leucine uptake in aged discs, leaving unaffected that of the other ions tested. Ion uptake by potato tuber appears to be supported by multiple transport systems, whose turnover is different for different groups of ions. These show also different sensibility to the action of cycloheximide and methionine.

Key words:

• potato tuber
• ion uptake
• ageing