Effects of a Series of Cycles of Alternating Low and High Soil Water Contents on the Rate of Apparent Photosynthesis in Sugar Cane

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Abstract
An in-vestigation of the effects of a series of cycles of alternating low and high soil water contents on the rate of apparent photosynthesis was conducted with sugar cane (Saccharum officinarum Var. 37-1933) plants. There was a progressive increase in the daily cumulative rate of photosynthesis, as the cycles progressed from the first to the fifth cycle, on the day of irrigation, on the first day after irrigation, and on the second day after irrigation. The increase became progressively less marked on the last two of these days and was not clearly apparent on the third day after irrigation. There was also a progressive decrease in the interval of time before the sugar cane plant showed the first increase in rate of photosynthesis following irrigation as the cycles progressed from the first to the fifth cycle. An overnight recovery in the rate of photosynthesis occurred even when the soil water content approached the permanent wilting percentage. An increase in rate of photosynthesis of the plant under moisture stress occurred when there was a brief period of reduced light intensity but did not occur when the water supply was adequate.