Biochemical and photosystem characteristics of wild-type and Chl b-deficient mutant in tree peony (Paeonia suffruticosa)

In order to explore the adaptive strategies of tree peony yl1 mutant in response to photooxidative stress, the changes of biochemical parameters, chlorophyll fluorescence, and the modulated 820-nm reflection of yl1 mutant and wild-type plants were compared. We found the activities of superoxide dismutase and catalase, the contents of soluble protein, proline, superoxide radicals, hydrogen peroxide, malondialdehyde, and relative electrical conductivity were significantly higher than those of the wild type. The photochemical efficiency of PSII significantly decreased, while the proportion of heat dissipation of yl1 mutant increased greatly. The donor and acceptor side and electron transfer of PSII were greatly inhibited. Meanwhile, the performance of PSI and coordination of two photosystems decreased markedly in yl1 mutant. The yl1 mutant could reduce the damage caused by photooxidative stress by increasing the activity of antioxidant enzymes, the content of some osmoregulatory substances, and the proportion of heat dissipation.