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

Abstract

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.

Modulation of glycerophosphorylcholine and glycerophosphorylethanolamine in rice shoots by the environment oxygen level

“…It has been shown that rice coleoptiles steadily accumulate soluble organic phosphates throughout a 48 h period of anoxia [3]. Following the 3'P NMR study of extracts of these compounds from rice shoots, we can report that anoxia induces significant changes in the phosphodiester region of the 31P NMR spectrum, with a marked increase of the GPC level.…”

“…It has been shown that growth, in the anoxic rice shoot, is confined to the coleoptile and is due to enlargement of existing cells along the shoot axis [3,15]; in that situation cells may be considered as oblate spheroids. For solids of this type the increase in surface area, after a major axis increase, is linearly correlated with the volume increase and is maximal for a given increase in volume, as compared to the case of spherical solids [16].…”

“…Operations were as reported in [3] with the following differences: seeds were germinated in large (0 = 22 cm) petri dishes with 100 seeds and 40 ml water per petri dish; anoxic treatments were carried out in an anoxic chamber and shoot dissection was performed under anoxia in the same chamber; dissected shoots were immediately frozen in liquid nitrogen and kept at -80°C until extracted.…”

“…Oxygen removal blocks growth of roots and leaves in rice seedlings while stimulating elongation and tapering of the coleoptile [1,3]. It has been shown that rice coleoptiles steadily accumulate soluble organic phosphates throughout a 48 h period of anoxia [3].…”

Expression ofα-Amylase Isoforms and theRAmylAGene in Rice (Oryza sativaL.) during Seed Germination, and its Relationship with Coleoptile Length in Submerged Soil

“…Coleoptile elongation is sustained by the continuous translocation of carbohydrates, amino acids, and salts from the endosperm (Menegus et al, 1984;Reggiani et al, 1995;Bertani et al, 1997). Perata et al (1992) reported that rice is able to germinate in anoxic conditions because it successfully produces a-amylase even under anaerobic conditions.…”