Interaction between increased CO2 and temperature enhance plant growth but do not affect millet grain production

The intergovernmental panel on climate change predicts a progressive increase in atmospheric CO2 concentration and temperature; however, their effects on cereals have been shown for a limited number of species. This study evaluates the effects of increased CO2 concentration and temperature separately and combined on millet growth and grain production in open-top chambers where the microclimate was adjusted to the following conditions: ambient CO2 and temperature; CO2 enriched (~ 800 ppm) and ambient temperature; ambient CO2 and higher temperature (+3ºC); and CO2-enriched and higher temperature. For each treatment, two chambers were used, each containing 15 7 L pots. Each pot received five seeds at the beginning of the experiment and thinning to one plant per pot at 15 days after sowing. Ten plants were harvested from each chamber 65 days after sowing and the plant height, the number of leaves and the longest root length as well as shoot and root biomass were measured. The remaining plants were harvested 130 days after sowing to evaluate grain production. The results indicate that high CO2 levels did not affect plant growth and biomass. On the other hand, plants subjected to high temperature grew 7% taller than those grown under ambient temperature. Contrastingly, plants submitted to both elevated CO2 and temperature were 19% taller and had 22% more shoot biomass than plants under ambient CO2 and temperature. However, grain production did not change in any of the environmental conditions. We provide evidence that millets are tolerant of the predicted climate changes and that grain production potential may not be affected.