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Incubation of 3-d-old seedlings of Oryza sativa L. cv Arborio under anaerobic conditions, leads to a large increase in the titer of free putrescine while aerobic incubation causes a slight decrease. After 2 days, the putrescine level is about 2.5 times greater without oxygen than in air. The rice coleoptile also accumulates a large amount of bound putrescine and, to a lesser extent, spermidine and spermine (mainly as acid-soluble conjugates). Accumulation of conjugates in the roots is severely inhibited by the anaerobic treatment. Feeding experiments with labeled amino acids showed that anoxia stimulates the release of (14)CO(2) from tissues fed with [(14)C]arginine and that arginine is the precursor in putrescine biosynthesis. After 2 d of anoxia, the activity of arginine decarboxylase was 42% and 89% greater in coleoptile and root, respectively, than in the aerobic condition. The causes of the differences in polyamine metabolism in anoxic coleoptiles and roots are discussed.

Menegus, E, Brambilla, I. and Bertani, A. 1984. Nutrient translocation pattern and accumulation of free amino acids in rice coleoptile elongation under anoxia -Physiol. Plant. 61: 203-208.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 Ca-+ with progressive intensity; Ca^* 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 Cn--^ 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)-'] 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.