Results of Changing Light and Temperature Regimes in a Corn Field and Temperature Effects on the Apparent Photosynthesis of Individual Leaves1

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Abstract
Irrigated, heavily fertilized corn (Zea mays L.) was grown in varying light and temperature regimes at Urbana, Ill., in 1967. The corn plants were subjected, during certain developmental stages, to a light and temperature “rich” field environment created with large aluminum reflectors. In addition, the effects of temperature on apparent photosynthesis were studied.Light and temperature (“radiation”) enrichment greatly increased grain yields. Per plant grain yields for a normal planting, a border row planting, and three “radiation rich” border row plantings (radiation rich from 1.5 m tall to pollination, pollination to maturity, and 1.5 m tall to maturity) were 42.4, 173.7, 206.8, 249.5 and 265.8 g/plant, respectively. Plants in a radiation rich regime, which were cooled by a water mist whenever the air temperature exceeded 29.4 C, yielded 22.2 g/plant (243.6 vs. 265.8 g/plant) less than radiation rich uncooled plants. Therefore, part of the yield increase in the radiation rich regime is apparently due to the increase in temperature caused by the additional radiation.Investigations of the effect of temperature on the apparent photosynthesis of attached ear leaves in bright sunlight near solar noon indicated optimum leaf and air temperatures of 40.5 and 32 C, respectively. The optimum temperature under ordinary field conditions might well be lower due to any one of several environmental limitations such as inadequate light, water stress, or perhaps inadequate carbon dioxide.

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