Influence of shade on leaf senescence of soybean
Date
1993
Authors
Christensen, Thomas Eugene
Major Professor
Advisor
Shibles, Richard
Committee Member
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Abstract
This study was undertaken with interest both in ultimately increasing soybean yield potential and with contributing to the scientific understanding of leaf senescence. The objectives of this study were to determine if shade, either constant or intermittent, influenced the senescence decline in lower and mid-canopy soybean leaves by: (1) Initiating the senescence photosynthetic decline or by (2) accelerating the rate at which the senescence decrease in photosynthetic capacity occurs. Understanding the physiological and biochemical alterations associated with shading lower leaves also was of interest. Intermittent shade is much less limiting on canopy photosynthetic rate than constant shade. Intermittent shade, especially sunflects separated by only short periods of shade, may allow maximal induction states to be reached and PAR to be utilized efficiently. Shade that does not result in leaf death from carbon starvation likely results in only an acclimation response and not initiation of senescence. A 70% rate of shade on soybean leaves does not alter the rate or pattern of photosynthetic decline except immediately after shading and just prior to leaf death.
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thesis