Phenotypical Temperature Adaptation of Protein Synthesis in Wheat Seedlings: Time Curves for Readaptation 1

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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 C), medium (20 C), or high (36 C) temperature the respective values are: 27 C and 14.2 kilocalories per mole, 31 C and 18.2 kilocalories per mole, 35 C and 23.6 kilocalories per mole, based on in vivo [14C]leucine incorporation into total protein. The validity of the [14C]leucine incubation method has been confirmed by double-labeling experiments. Readaptation time curves are complex: the optimum temperature parameter readjusts within approximately 4 hours to an altered temperature regime, whereas the temperature coefficient needs between 4 and 96 hours 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 micrograms per milliliter) reduces [14C]leucine incorporation into protein by 85%, thus indicating that predominantly the cytoplasmic 80S system of protein synthesis is involved in temperature adaptation.

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