Energy dissipation in photosystem 2 complexes of peanut leaves subjected to light pulses

To increase crop yields, intercropping agricultural cultivation approach (IACA) and relay cropping agricultural cultivation approach (RACA) were introduced into cultivation of peanut (Arachis hypogaca L.), one of the most important oil crops in the world. IACA/RACA improves the yield of the crop per unit area, but rather decreases the yield of a single crop compared with mono-cropping agricultural cultivation approach. In peanut IACA/RACA, peanut plants would grow under low light and high light pulses (HLP) before maize/wheat harvest. Energy dissipation in photosystem 2 (PS2) complexes was evaluated in peanut leaves after being induced by light pulses and continuous light with different light intensities. Actual photochemical efficiency of PS2 (ΦPS2) and non-photochemical quenching induced by light pulses in peanut leaves generally were significantly lower compared with those induced by continuous light. In addition, the degree of PS2 reaction center closure (1-qP) induced by light pulses in peanut leaves was significantly higher compared with those induced by continuous light. Different results were obtained only for ΦPS2 and 1-qP induced by 20 s HLP. In methyl viologen (MV) treated samples, ΦPS2 and the quantum yield of light induced thermal dissipation by non-functional PS2 (Φ_NF) were similar to those observed in non-MV treatments. These results implied that light pulses could induce photoinactivation of PS2 reaction centers but not the xanthophyll cycle to dissipate excess energy.