Abstract: In an attempt to explore the relationships between phosphatidylglycerol (PG) molecular species of thylakoid membrane lipids and sensitivities to chilling-induced photoinhibition, PG molecular species, D1 protein, electron transport activities of thylakoid membrane and the potential quantum yield (Fv/Fm) in rice treated under middle and low PFD at 11 ℃ were analysed by high performance liquid chromatography (HPLC), enzyme hydrolysis, gas phase chromatography (GC) and so on. Results showed that the major molecular species of PGs in rice thylakoid membrane were 18:3/16:0, 18:3/16:1(3t), 18:2/16:0, 18:2/16:1(3t), 18:1/16:0, 18:1/16:1(3t), 16:0/16:0, 16:0/16:1(3t). There were large differences in contents of unsaturated PG molecular species such as 18:1~3/16:0~16:1(3t) and saturated PG molecular species like 16:0/16:0~16:1(3t) among japonica cv 9516 (j-9516), japonica-indica hybrid F1 j-9516/i-SY63 (ji-95SY) and indica cv Shanyou 63 (i-SY63). J-9516 containing higher contents of unsaturated PG molecular species was manifest in stable D1 protein contents under chill and tolerant to chill-induced photoinhibition. In contrast to j-9516, i-SY63 with lower contents of unsaturated PG molecular species, exhibited unstable D1 protein contents under chill and was sensitive to chill-induced photoinhibition. ji-95SY containing middle contents of unsaturated PG molecular species between those of j-9516 and i-SY63, exhibited mid extent of sensitivity to chill-induced photoinhibition. The loss in D1 protein has been also accounted for the inhibition in electron transport activity of thylakoid membrane and the observed decline in Fv/Fm. The PG molecular species efficient in raising chilling-resistant capacity were those containing unsaturated fatty acids, namely, unsaturated PG molecular species. These results implied that the substrate selectivity of the glycerol-3-phosphate acyltransferase (GPAT) in chloroplasts towards 16:0 or 18:1 and the activity of fatty acid desaturases displayed greatly difference between japonica and indica rice. It was possible to enhance the capacity of resistance to chilling-induced photoinhibition by improving or modifying GPAT gene.

Key words: chilling-induced photoinhibition, D1 protein, molecular species, phosphatidylglycerol, rice.