Effects of Silica Application on Transpiration from Rice Panicle under Elevated CO2 Concentration

Rice yield is sensitive to water stress at the flowering stage, and it is particularly important to study the water status of the panicle due to their sensitivity to water stress. In the panicle, water loss is primarily controlled through the cuticle layer, which contains silica. This suggests that the main role of silica is to suppress transpiration from the leaves. Under ambient atmospheric carbon dioxide concentrations ([CO2]), the role of silica is thus known, but it is unclear how elevated [CO2] affects the role of silica in transpiration. We studied the effects of elevated [CO2] (700 µmol mol-1) on transpiration from the rice panicle, and investigated the combined effects of elevated [CO2] and the presence of silica in the culture solution on transpiration from the rice panicle during the flowering stage. Rice plants were grown hydroponically in two artificially illuminated chambers. The transpiration from the rice panicle was measured using the “temperature wave method”. The transpiration from rice panicles decreased under elevated [CO2] and addition of silica to the culture solution reduced transpiration from the panicle regardless of [CO2]. This result suggested that silica may thus contribute to conserving water content in the rice panicle under elevated [CO2].