Abstract
Enhancing crop yield response to elevated CO2 concentrations (E-[CO2]) is an important adaptation measure to climate change. A high-yielding indica rice cultivar “Takanari” has recently been identified as a potential candidate for high productivity in E-[CO2] resulting from its large sink and source capacities. To fully utilize these traits, nitrogen should play a major role, but it is unknown how N levels influence the yield response of Takanari to E-[CO2]. We therefore compared grain yield and quality of Takanari with those of Koshihikari, a standard japonica cultivar, in response to Free-Air CO2 enrichment (FACE, +200 μmol mol−1) under three N levels (0, 8, and 12 g m−2) over three seasons. The biomass of both cultivars increased under E-[CO2] at all N levels; however, the harvest index decreased under E-[CO2] in the N-limited treatment for Koshihikari but not for Takanari. The decreased harvest index of Koshihikari resulted from limited enhancement of spikelet number under N-limitation. In contrast, spikelet number increased in E-[CO2] in Takanari even without N application, resulting in significant yield enhancement, averaging 18% over 3 years, whereas Koshihikari exhibited virtually no increase in yield in E-[CO2] under the N-limited condition. Grain appearance quality of Koshihikari was severely reduced by E-[CO2], most notably in N-limited and hot conditions, by a substantial increase in chalky grain, but chalky grain % did not increase in E-[CO2] even without N fertilizer. These results indicated that Takanari could retain its high yield advantage over Koshihikari with limited increase in chalkiness even under limited N conditions and that it could be a useful genetic resource for improving N use efficiency under E-[CO2].
Highlights
Atmospheric CO2 concentrations ([CO2]) are rising at an unprecedented rate
Soil N mineralized during the flooding period in 2012 was 5–6 times greater than the initial exchangeable ammonium N (EAN) and not significantly different between the CO2 treatments: 8.25± 0.73 g m−2 in A-[CO2] and 10.0 ± 1.45 g m−2 in E-[CO2]
Ample evidence exists that the biomass response to E-[CO2] is limited by soil N availability in various plant species (Reich and Hobbie, 2012; Feng et al, 2015), which are in agreement with the physiological observations that the enhancement of leaf photosynthesis or canopy light use efficiency was decreased owing to poor N status of the leaves (Nakano et al, 1997; Sakai et al, 2006)
Summary
Atmospheric CO2 concentrations ([CO2]) are rising at an unprecedented rate. Global [CO2] surpassed a milestone level of 400 ppm in 2015 and the rate of increase is becoming faster (https://www.esrl.noaa.gov/gmd/ccgg/trends/). Increasing concentrations of CO2 and other greenhouse gases will likely induce global environmental changes such as increases in temperatures, which are projected to have negative effects on food production of the major cereal crops (Zhao et al, 2017) or slow the rate of food production increase that is required to meet increasing demand (Iizumi et al, 2017). Increasing [CO2] will have a direct positive effect on crop photosynthesis and thereby increase grain yield; the size of the CO2 fertilization effect is one of the major sources of uncertainty in the projection of the global crop production (Rosenzweig et al, 2014; Deryng et al, 2016; Schleussner et al, 2018). To exploit the positive effects of E-[CO2] on crop production in the future, the mechanisms by which the CO2 fertilization effects vary must be better understood
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
