CO2 Exchange and Chlorophyll Fluorescence of Phospho-enolpyruvate Carboxylase Transgenic Rice Pollen Lines

To elucidate the photosynthetic physiological characteristics and the physiological inherited traits of rice (Oryza sativa L.) hybrids and their parents, physiological indices of photosynthetic CO₂ exchange and chlorophyll fluorescence parameters were measured in leaves of the maize phosphoenolpyruvate carboxylase (PEPC) transgenic rice as the male parent, sp. japonica rice cv. 9516 as the female parent, and the stable JAAS45 pollen line. The results revealed that the PEPC gene could be stably inherited and transferred from the male parent to the JAAS45 pollen line. Moreover, the JAAS45 pollen line exhibited high levels of PEPC activity, manifesting higher saturated photosynthetic rates, photosynthetic apparent quantum yield (AQY), photochemical efficiency of photosystem II and photochemical and non‐photochemical quenching, which indicated that the JAAS45 pollen line has a high tolerance to photo‐inhibition/photo‐oxidation under strong light and high temperature. Furthermore, JAAS45 was confirmed to still be a C₃ plant by δ13C carbon isotope determination and was demonstrated to have a limited photosynthetic C₄ microcycle by feeding with exogenous C₄ primary products, such as oxaloacetate or malate, or phosphoenolpyruvate. The present study explains the physiological inherited properties of PEPC transgenic rice and provides an expectation for the integration of traditional breeding and biological technology. (Managing editor: Ping He)