Chilling-induced Photodamage To Photosystem Of Myrica Rubra Leaves And The Relationship Between The Photodamage And The D1 Protein

In the present study, the potted plants of the two-year-old Myrica rubra were used to study the changes of chlorophyll fluorescence and the level of D1 protein in PS Ⅱ reaction centers in Myrica rubra leaves treated with different temperature (25, 12, 2℃) under irradiance levels (0, 400 μmol·m-2·s-1) for 12 hours, and the possible response mechanisms of effects of chilling stress on photosynthetic apparatus in Myrica rubra leaves were discussed. In addition, we compared the differences of chlorophyll fluorescence parameters between Myrica rubra leaves and Citrus unshiu leaves, another warm-climate plant under low temperature and light (2℃ 400 μmol m-2 s-1), affording academic foundation for cultivation management of Myrica rubra trees in furure. The main results of this study are as follows:1) Compared with 25℃ treatment , 12℃ 0 μmol·m-2·s-1 treatment for 12h had little effect on photosynthesis of Myrica rubra leaves, but exposure to 2℃ 0 μmol·m-2·s-1 resulted in increases in Fo (initial fluorescence), (Fi-Fo)/(Fp-Fo)(amount of inactive PS Ⅱ reaction centers) and the excess light energy E, but decreases in Fv/Fm (maximal photochemical efficiency of PSⅡ), ETR (linear electron transport rate), OPSⅡ(quantum yield of PSⅡ) and qP (photochemical quenching). These results indicated that short-term and low-grade chilling temperature almost had no effect on PSⅡ reaction centers in the dark, but severe chilling temperature (2℃) induced damage to PS Ⅱ reaction centers.2) Compared with 25 ℃ 400 μmol·m-2·s-1 and 12℃ 0 μmol·m-2·s-1 treatment, the Fv/Fm, ETR, OPS Ⅱ and qP decreased, but the Fo, (Fi-Fo)/(Fp-Fo) and the excess light energy E increased after treatment with 12℃ 400 μmol·m-2·s-1, suggesting that chilling temperature induced photoinhibition of photosynthesis of Myrica rubra leaves. The lower the temperature, the more significant effect of the light superposition and the more serious photoinhibition induced by chilling temperature.3) During the course of photoinhibition of photosynthesis of Myrica rubra leaves the excess light energy E and qN (non-photochemical quenching) increased; the photodamage to PSⅡ reaction centers was greatly enhanced in the presence of...