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Effect of Temperature on Photosynthesis and Photorespiration of Wheat Leaves

A. J. KEYS, E. V. S. B. SAMPAIO, M. J. CORNELIUS and I. F. BIRD
Journal of Experimental Botany
Vol. 28, No. 104 (June 1977), pp. 525-533
Published by: Oxford University Press
Stable URL: http://www.jstor.org/stable/23689582
Page Count: 9
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Effect of Temperature on Photosynthesis and Photorespiration of Wheat Leaves
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Abstract

Wheat plants were grown in a controlled environment with day temperatures of 18 °C and with 500 μEinsteins m-2 s-1 of photosynthetically active radiation for 16 h. Before anthesis and 2 to 3 weeks after, rates of net photosynthesis were measured for leaves in 2 or 21% O2 containing 350 vpm CO2 at 13, 18, 23, and 28 °C and with 500 μEinsteins m-2 s-1 of photosynthetically active radiation. Also, under the same conditions of light intensity and temperature, the rates of efflux of CO2 into CO2-free air were measured and, for mature flag leaves 3 to 4 weeks after anthesis, gross and net photosynthesis from air containing 320 vpm 14CO2 of specific activity 39.7 nCi μmol-1. When the O2 concentration was decreased from 21 to 2% (v/v) the rate of net photosynthesis increased by 32 per cent at the lowest temperature and 54 per cent at the highest temperature. Efflux of CO2 into CO2-free air ranged from 38 per cent of net photosynthesis at 13 °C to 69 per cent at 28 °C. Gross photosynthesis, measured by the 14C assimilated during 40 s, was greater than net photosynthesis by some 10 per cent at 13 °C and 17 per cent at 28 °C. These data indicate that photorespiration was relatively greater at higher temperatures.

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