Glimpse of rice productivity in the future

Anthropogenic activities have increased the concentration of atmospheric CO2 continuously from about 280 parts per million at the beginning of the industrial revolution to 390 ppm at present time. Future estimations on the atmospheric CO2 concentration ranges between 450 ppm and 600 ppm by the year 2150 and is expected to rise continuously as a result of human activities and climate change. This change in the atmospheric CO2 concentration is believed to affect crops like rice in terms of its productivity and quality. How rice behaved millions of years ago and how it would respond to increase in CO2 concentration in the atmosphere in the future are not yet well understood. What type of rice plant should we cultivate under elevated CO2. Since CO2 is the one being utilized by plants to make food; can rice plants take advantage of this extra photosynthate to increase its grain yield? Could rice exposed to high CO2 produce grains of high quality? In this study rice plants were grown in paddy conditions within growth chambers at a range of CO2 concentrations from preindustrial levels (195 ppm) to those expected in the bundle sheath of C4 plants (1560 ppm). Photosynthetic parameters in terms of photosynthetic rate, oxygen sensitivity and rubisco protein content remained largely constant as a function of light intensity and CO2 concentration. Photosynthetic rates measured at ambient CO2 conditions were therefore enhanced as the growth of CO2 concentration increased. Leaf anatomy was not altered and there was no evidence of sink-limitation or feedback inhibition of photosynthesis at elevated CO2. This was further supported by enhanced biomass production and grain yield at increased growth CO2 concentration compared to rice grown in the field. The physical and cooking traits of rice grains were not affected but chalkiness was reduced and protein content was increased at elevated CO2.