Photosynthetic performance of maize hybrids to drought stress

Maintaining photosynthetic activities is a critical function that allows crops to adapt to drought stress. We evaluated drought-induced changes in photosynthetic performance via gas exchange as well as photosynthetic electron transport and carbon assimilation process in two maize (Zea mays L.) cvs. Shaandan 609 (SD609) and Zhengdan 958 (ZD958). Plants were subjected to different intensity of drought stress inside of rain shelter. In both cultivars, moderate and severe drought stress caused a decrease in photosynthetic rate and stomatal conductance, but an increase in the intercellular CO2 concentration. Moreover, chlorophyll a fluorescence transients showed that drought stress significantly increased the positive Land K-band, revealing decreased function of oxygen-evolving complex, and decreased the fluorescence parameters reflecting electron flow from the intersystem carriers to the final reduction of PSI end electron acceptors. Also, moderate and severe drought stresses reduced both total activity and Rubisco activity. These parameters were more affected in ZD958 by drought stress compared to SD609. Based on our results, damaged PSII, reduced electron transport, and inactivation of Rubisco were main non-stomatal limitation of photosynthesis inhibition in both cultivars under moderate and severe drought stress. Photosynthetic apparatus of SD609 was more resistant to drought stress than that of ZD958.