Intercellular CO2 concentration and stomatal or non-stomatal limitation of rice under water saving irrigation

In order to investigate stomatal and non-stomatal limitation on rice leaf photosynthesis rate under water saving irrigation, diurnal variations of intercellular CO2 concentration for rice leaves under water saving irrigation was analyzed. Then stomatal and non-stomatal limitation on rice leaf photosynthesis rate caused by water deficit under controlled irrigation was discussed based on the intercellular CO2 concentration variation. Intercellular CO2 concentration varied in v-style and got the daily minimum value at 12:00-14:00, but non-stomatal limitation index Ci /C varied the other way round with stomatal limitation index Ls. Moderate water stress under water saving irrigation did not result in change in relationships between intercellular CO2 concentration and photosynthesis rate. Stomatal limitation index Ls was found higher than flooding rice when soil moisture was lower in controlled irrigation paddy. But non-stomatal limitation index Ci /C and photosynthesis rate Pn made no difference when compared with flooding paddy rice. It indicates that stomatal limitation index Ls overestimated the stomatal limitation on photosynthesis. So, variation pattern of intercellular CO2 concentration and it correlations with environmental factors under controlled irrigation are same to those under flooding irrigation. Stomatal limitation is increased under controlled irrigation, but photosynthesis rate not.