Elevated CO2-induced Increases in both Rice and Maize
Paper Reviewed Pingale, B.N., Singh, S.D. and Yadav, A. 2017. Potential impacts of increasing atmospheric carbon dioxide on yield and plant growth of rice (Oryza sativa) and maize (Zea mays) crops. Indian Journal of Agricultural Sciences 87: 1041-1044. Rice is the most consumed staple crop in the world and maize is close behind in rank as the third most important cereal crop. Their annual yields are consumed by billions of persons worldwide. As a C3 and C4 food crop, respectively, rice and maize are expected to respond differently to rising atmospheric CO2 concentrations, given the different pathways they utilize in fixing CO2 and constructing their tissues. One school of thought, for example, contends that C4 crops will not experience significant growth and yield increases under elevated CO2 whereas C3 crops will. In a test of this hypothesis, Pingale et al. (2017) grew rice and maize for two growing seasons under ambient (395 ppm) and enriched (550 ppm) CO2 using Free-air CO2 Enrichment (FACE) technology at the Indian Agricultural Research Institute in New Delhi, India. In discussing their findings, Pingale et al. report that elevated CO2 positively influenced the growth and productivity of both crops. Plant growth and yield parameters such as leaf area, stem dry weight, panicle dry weight, cob dry weight and grain number per cob were all significantly increased under elevated CO2. And the end result of these several enhancements was a CO2-induced increase in both rice and maize grain yield. As shown in the figure below, for the 2011-12 and 2012-13 growing seasons, elevated CO2 stimulated rice grain yields by 14 and 16.2 percent and maize yields by 13.3 and 13.8, respectively, which increases were statistically significant. In light of the above findings, it would appear that C4 crops can and do respond to elevated CO2 in a similar manner to C3 crops, at least in this case for rice and maize.