Thermoperiodic Effects on the Growth and Photosynthesis of Wheat and Other Crop Plants

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Abstract
The optimal temperatures for growth in dry weight during the vegetative stage of pea [Pisum sativum], bean [Phaseolus vulgaris], tomato [Lycopesicon esculentum] cucumber [Cucurbita sativa], corn [Zea mays], oats [Avena sativa] and wheat [Triticum aestivum] were determined over the range of 15-35.degree. C, at a daylength of 12 h. Alternating the day and night temperature with a spread of 10-20.degree. C did not increase growth, as compared with giving the same optimal mean temperature continuously. A high day temperature and lower night temperature resulted in greater growth than a low day temperature and higher night temperature for the same daily mean temperature. From a detailed analysis of the growth of wheat, the higher rate of growth obtained under a temperature regime of high day temperature was the result of a higher rate of net photosynthesis. The leaf area ratio and other morphological components of growth were similar whether the higher temperature occurred during the day or night.