Effects of high temperature and CO 2 concentration on spikelet sterility in indica rice

Abstract

The effects of increasing temperature and CO 2 concentration on floral sterility were examined for rice (cv. IR 72) using open-top chambers located at the International Rice Research Institute in Los Banos, Philippines. The field-based open-top chamber system was used to simulate four different environments: ambient temperature and CO 2 concentration (control); ambient temperature, ambient +300 μ1 1 −1 CO 2; ambient +4°C temperature, ambient CO 2 concentration; ambient +4°C temperature, ambient +300 μ1 1 −1 CO 2. High temperature during flowering resulted in increased pollen sterility with the degree of sterility exacerbated if rice was exposed to both high temperature and increased CO 2 concentration. The critical air temperature for spikelet sterility (as determined from the number of germinated pollen grains on the stigma) was reduced by ca 1°C at elevated concentrations of carbon dioxide. We speculate that this downward shift in critical temperature may be due to the observed increase in air temperature within the canopy at high CO 2 concentrations. This increase in air temperature, in turn, may be related to stomatal closure and reduced transpirational cooling in an elevated CO 2 environment. Data from this experiment indicate that increasing CO 2 concentration could limit rice yield if average air temperature increased simultaneously.