Abstract:

Low chlorophyll b rice mutant and the wild type rice (Zhenhui 249) were used to study the effects of low chlorophyll b on thermostability of photosystemⅡ in mutant by measuring their changes in chlorophyll fluorescence parameters and polyphasic chlorophyll fluorescence transients under different temperature treatments. The results showed that the temperature of Fo rising threshold was shifted 3℃ lower in the mutant (43℃) than in the wild type (46℃). At temperature up to over 40℃, O-J-I-P transient was transformed into O-K-J-I-P transient, a very clear K point appeared, this suggested that high temperature damaged the oxygen evolving complex (OEC), and the degree of damage was severer in mutant than in the wild type. In addition, high temperature led to inactivation of PSⅡ reaction centre. All results indicated that the mutant showed a tendency for higher thermosensitivity, and the decrease of chlorophyll b in LHCII could lead to less thermostability of PSⅡ structure and function.

Key words: Rice, Thermostability, Low chlorophyll b mutant, Chlorophyll fluorescence parameters, PhotosystemⅡ