Photoinhibition of Leaves with Different Photosynthetic Carbon Assimilation Characteristics in Maize (<i>Zea mays</i>)

Abstract

Strong light decreases the rate of photosynthesis and assimilates production of crop plants. Plants with different carbon reduction cycles respond differently to strong light stress. However, variation in photoinhibition in leaves with different photosynthetic characteristics in maize is not clear. In this experiment, we used the first leaves (with an incomplete C 4 cycle) and fifth leaves (with a complete C 4 cycle) of maize plants as well as the fifth leaves (C 3 cycle) of tobacco plants as a reference to measure the photosynthetic rate (P N ) and chlorophyll a parameters under strong light stress. During treatment, P N , the maximal fluorescence (F m ), the maximal quantum yield of PSII photochemistry (F v /F m ), and the number of active photosystem II (PSII) reaction centers per excited cross-section (RC/CS m ) declined dramatically in all three types of leaves but to different degrees. P N , F m , F v /F m , and RC/CS m were less inhibited by strong light in C 4 leaves. The results showed that maize C 4 leaves with higher rates of photosynthesis are more tolerant to strong light stress than incomplete C 4 leaves, and the carbon reduction cycle is more important to photoprotection in C 4 leaves, while state transition is critical in incomplete C 4 leaves.