Author
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EARL, HUGH - UNIVERSITY OF GEORGIA |
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Davis, Richard |
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Submitted to: Agronomy Journal
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 6/18/2002 Publication Date: 5/1/2003 Citation: Earl, H.J., Davis, R.F. 2003. Effect of drought stress on leaf and whole canopy radiation use efficiency and yield of maize. Agronomy Journal. 95:688-696. Interpretive Summary: Drought stress reduces yield of corn by reducing the amount of light that leaves intercept (due to smaller plants), reducing the efficiency with which plants use light they do intercept (radiation use efficiency, or RUE), and reducing the proportion of final plant weight comprised of grain (harvest index). Our primary objective was to determine how much of the observed yield losses were attributable to each of these components for corn grown under moderate and severe drought stress. A secondary objective was to develop a rapid method of estimating RUE in corn. RUE of corn is calculated by weighing above-ground plant material and measuring how much light plants absorb to determine how much weight is produced from a specified amount of light. That method requires destroying test plants and does not allow evaluation of RUE over short periods of time (hours or days) because changes in plant weight can only be measured over longer periods. Measuring chlorophyll activity (chlorophyll fluorometry) may provide an accurate estimate of RUE at any given moment without damaging the plants, and hundreds of measurements can be made per day since each measurement takes only a few seconds. Two levels of drought stress and an unstressed control treatment were established using drip tape irrigation in 2000 and 2001. Mild and severe drought stress treatments reduced yield by 63 and 85% in 2000 and by 13 and 26% in 2001. Stressed plants were smaller and intercepted less light, but that was responsible for very little yield loss. Reduced RUE and reduced harvest index both caused significant yield losses and were generally of similar importance in causing yield loss. Chlorophyll fluorescence measurements allowed quick and accurate estimates of RUE without damaging plants, so we were able to improve on previous methods. Technical Abstract: Drought stress reduces yield of corn by reducing canopy absorptance of incident photosynthetically active radiation (PAR), reducing radiation use efficiency (RUE), and reducing harvest index (HI). The primary objective of this work was to quantify yield losses attributable to each of these components for corn exposed to two levels of drought stress. A second objective was to examine the relationship between RUE estimated using chlorophyll fluorescence techniques and RUE estimated from crop dry matter determinations and weekly measurements of canopy PAR interceptance. Two levels of soil water deficit and a control treatment were established using drip tape irrigation, and dry matter harvests were taken at mid-season and at physiological maturity. Mild and severe water stress treatments reduced grain final yield by 63 and 85% respectively in 2000, and by 13 and 26% respectively in 2001. Reduced canopy absorptance of PAR was generally a very minor yield loss component. Yield losses attributable to reduced RUE and reduced HI were of similar magnitude. Weekly chlorophyll fluorescence measurements were used to estimate the average quantum efficiency of photosystem II at a photosynthetic photon flux density of 1200 µmol m-2 s-1 (FII1200) for each plot. Water stress treatments strongly reduced FII1200, but it recovered completely upon rewatering. Crop dry matter accumulation was not linearly related to PAR interceptance, due to decreased RUE in the water stress treatments. However, the linear relationship was restored when daily intercepted PAR was adjusted by the current estimate of FII1200, suggesting that FII1200 can be used as a meaningful indicator crop RUE. |
