Temperature-dependent metabolic adaptation of Triticum aestivum seedlings to anoxia

Wheat (Triticum aestivum) is considered anoxia intolerant but it shows variance in anoxia responses between genotypes and environmental treatments. We firstly examined 4 day old seedlings of five wheat genotypes in response to anoxia at 15 degrees C and 28 degrees C by assessing growth rate, tissue damage and changes in metabolite abundances. Significant genotypic variations in anoxia tolerance were observed, especially at 28 degrees C. Wheat seedlings grown at 15 degrees C appeared to be more anoxia tolerant and showed less genotypic variation than those at 28 degrees C. To minimize seedling size variations and define the temperature effects, we grew two contrasting genotypes at 15 degrees C for 3.5 d and adapted to 4 different temperatures for 0.5 d before exposing them to anoxia at each adapted temperature. Genotypic variation in abundance of anoxia induced metabolites occurred at 24 degrees C and 28 degrees C but not at 15 degrees C and 20 degrees C. Tissue-and temperature-dependent metabolic adaptations to anoxia were revealed. In roots, the ability to maintain sugar/sugar-phosphate and TCA cycle metabolite levels and the accumulation of amino acids when temperature was below 24 degrees C correlated with anoxia tolerance. Temperatures between 20 degrees C - 24 degrees C are critical for metabolic adaptation and suggest that further assessment of waterlogging/flooding tolerance of wheat seedlings should consider the temperature-dependence of tolerance in evaluations.