Submitted to: Journal of Experimental Botany
Publication Type: Peer reviewed journal
Publication Acceptance Date: 6/10/2013
Publication Date: 7/20/2013
Citation: Slattery, R.A., Ainsworth, E.A., Ort, D.R. 2013. A meta-analysis of responses of canopy photosynthetic conversion efficiency to environmental factors reveal major causes of yield gap. Journal of Experimental Botany. DOI:10.1093/jxb/ert207. Interpretive Summary: Improving crop yields to meet the demands of the expanding population with increasing economic capacity is growing increasingly difficult. The human population is expected to reach almost nine billion people by the middle of this century. The rise in population coupled with improving living standards in China and India necessitate that yields double in less than 40 years yet rates of yield increase in some major crops have slowed in the most recent decades compared to rates of the seventies and eighties. Meeting food and feed demands for the middle of the twenty-first century poses a formidable challenge to researchers and growers. The purpose of this study was to use a meta-analysis to a) determine the percent change in energy conversion efficiency due to elevated [CO2], elevated [O3], water stress, temperature stress, nitrogen application, phosphorus application, shade, plant damage, and intercropping, and b) identify the effect of within treatment variability due to treatment type and dosage, plant characteristics, and growth environment on energy conversion efficiency. In doing so, we examined the sensitivity of energy conversion efficiency to common treatments that affect the capacity of crops to close the yield gap between average and potential yields.
Technical Abstract: Improving plant energy conversion efficiency is crucial for increasing food and bioenergy crop production and yields. This study statistically quantifies the effects of climate/weather factors and management techniques on energy conversion efficiency from 140 published studies and provides a quantitative comparison of where improvements would have the largest impact on closing yield gaps. A meta-analysis was used to determine the effects of elevated [CO2], elevated [O3], water stress, temperature stress, nutrient (nitrogen, phosphorus) addition, shade, intercropping, and foliar damage on energy conversion efficiency. Variation in the response of energy conversion efficiency to treatment type and dosage, plantcharacteristics, and growth conditions were also examined. Significant mean increases in energy conversion efficiencywere caused by elevated [CO2] (20%), shade (18%), and intercropping (15%). Energy conversion efficiency increased curvilinearly up to 55% with nitrogen additions whereas phosphorus application was most beneficial at low levels. Significant decreases in energy conversion efficiency of -8.4% due to elevated [O3], -16.8% due to water stress, and -6.5% due to foliardamage were found. A non-significant decrease in energy conversion efficiency of -17.3% was caused by temperature stress. Studies conducted in conditions other than the field often produced significantly different responses in energy conversion efficiency as compared to field studies.