Induction and growth of potato tubers as affected by nitrate

Abstract

Nitrate is well known to inhibit tuber induction; much less is known, however, on its effect on tuber growth. We therefore studied the effect of amount and timing of nitrate supply on tuber induction and growth of potato (Solanum tuberosum var Sava) under controlled conditions. Our results confirm that nitrate has an inhibitory effect on tuber induction but it clearly stimulated tuber growth. It was not nitrate ∼per se∼ (i.e.not the nitrate stored in the tuber) which stimulated tuber growth but it was the nitrate which was supplied to the plant. Under nitrate-limiting conditions many but small tubers were produced and fewer but bigger tubers developed with a high nitrate supply. Nitrate-limitation even resulted in resorption of tubers to sustain growth of the remaining ones. Supplying a high nitrate concentration (to increase tuber size) to previously nitratelimited plants (with many but small tubers) did, however, not result in many big tubers.