Author
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Slattery, Rebecca |
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Ort, Donald |
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Submitted to: Plant Physiology
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 2/10/2015 Publication Date: 3/31/2015 Citation: Slattery, R.A., Ort, D.R. 2015. Photosynthetic energy conversion efficiency: setting a baseline for gauging future improvements in important food and biofuel crops. Plant Physiology. 168:383-392. Interpretive Summary: Radiation Use Efficiency (RU has a broad interest base across agricultural science because it is a core element determining crop yield potential. Increasing demands on the globe’s food production system over the next three to four decades portend a huge burden on the world’s shrinking farmlands. Different studies predict that by mid-century global crop production will need to increase 60 to 120%. What limits crop productivity? For most terrestrial crops it is usually the availability of water but next is the waste of light at mid-day intensities. Thus improving light use efficiency is a key target for improving yield and has become a new funding emphasis of several national funding agencies and foundations in this country and elsewhere in the world. While there is seeming agreement of substantial potential benefit in increasing RUE in major food and biofuel crops, judging the effectiveness of each strategy is difficult without baseline estimates of RUE and rates of gain to date in individual crops. This work provides that baseline using the rigorous statistical tools of a meta-analysis to interpret a collection of individual published studies as opposed to the traditional method of qualitatively integrating research studies. Our analysis shows positive correlations with year of cultivar release were only present in a few food crops, and when present the rates of increase were relatively low, suggesting that RUE will not double in most crops before the middle of the century at the current rate of increase. Our analysis emphasizes the importance of using strategies that improve nitrogen fixation efficiency, canopy light distribution, and tolerance to higher temperatures to increase genetic gains and limit detrimental environmental effects on RUE. Technical Abstract: The conversion efficiency (RUE) of absorbed radiation into biomass (MJ dry matter per MJ absorbed photosynthetically active radiation) is a component of yield potential that has been estimated at less than half the theoretical maximum. Various strategies have been proposed to improve RUE, but a statistical analysis to establish baseline RUE levels across different crop functional types is lacking. Data from 164 RUE studies conducted in relatively unstressed growth conditions were used to determine the means, greatest contributors to variation, and genetic trends in RUE across important food and biofuel crop species. RU was greatest in biofuel crops (0.049-0.066), followed by C4 food crops (0.045-0.048), C3 non-legumes (0.036-0.041), and finally C3 legumes (0.028-0.035). Despite confining our analysis to relatively unstressed growth conditions, total incident solar radiation and average growing season temperature most often accounted for the largest portion of RUE variability. Genetic improvements in RUE, when present, were often <0.6% per year, revealing the unrealized potential of improving RUE as a promising contributing strategy to meet projected future agricultural demand. |
