Nutrient translocation pattern and accumulation of free amino acids in rice coleoptile elongation under anoxia

Abstract

Comparing nutrient translocation to the rice (Oryza sativa L. var. Arborio) shoot during anoxia with the aerobic situation, it was found that anoxia reduced the translocation of K+, phosphorus, Mg2+ and Ca2+ with progressive intensity; Ca2+ translocation was practically zero in the absence of oxygen. The translocation of K+ and phosphorus under anoxia was still considerable and contributed to the maintenance of a high osmotic potential while the blocking of Ca2+ translocation caused a decrease in its concentration in the anoxic coleoptile, possibly favouring high cell wall plasticity in that organ. As anoxia proceeded, amino acids, no longer employed in protein synthesis, accumulated in the coleoptile, reaching spectacular levels [51 mmol kg of tissue‐water)−1] and, after 48 h of anoxia, their contribution to the osmotic potential was 80% of that of K+, as against less than 20% in all aerobic treatments. Anoxia caused a reduction in soluble hexose concentrations which, however, were more than compensated osmotically by the accumulation of amino acids.