Phenotypical Temperature Adaptation of Protein Synthesis in Wheat Seedlings

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Abstract
Optimum temperature and temperature coefficient of protein synthesis in young wheat plants exhibit phenotypical temperature adaptation. In plants grown for 2 days at either chilling (4.degree. C), medium (20.degree. C), or high (36.degree. C) temperature the respective values are: 27.degree. C and 14.2 kcal/mol, 31.degree. C and 18.2 kcal/mol, 35.degree. C and 23.6 kcal/mol, based on in vivo [14C]leucine incorporation into total protein. The validity of the [14C]leucine incubation method was confirmed by double-labeling experiments. Readaptation time curves are complex: the optimum temperature parameter readjusts within approximately 4 h to an altered temperature regime, whereas the temperature coefficient needs 4-96 h for complete readaptation, depending on the temperature conditions prior to the temperature shift. Heat-preadapted plants need a recovery period at medium temperature to regain their cold adaptability with respect to optimum temperature. Cycloheximide (30 .mu.g/ml) reduces [14C]leucine incorporation into protein by 85%, indicating that predominantly the cytoplasmic 80S system of protein synthesis is involved in temperature adaptation.