Abstract:

A newly-developed super-high-yielding rice(Oryza sativa L.) cultivar Liangyoupeijiu and a traditional cultivar Shanyou63 (as control) were used to study the effect of low temperature at night on flag leaves by mainly measuring their carotenoids content, lipid peroxidation and fatty acid composition of thylakoid membranes. 20℃ and 15℃ were the two treatment temperatures. The results showed that, for both of the two cultivars, chlorophyll content of 20℃ treatment group was decreased statistically compared with that of field-grown plants, but that of 15℃ treatment group was not decreased significantly. Carotenoids content and chlorophyll a/b ratio were decreased in both cultivars with longer treatment time and lower temperature, but the ratio of carotenoids content to chlorophyll content was increased. With 4 d low temperature treatment, MDA content of the two cultivars was significantly higher than that of field-grown plants, also higher than that with two day’s treatment. O₂^．- content was also increased with the treatment of longer time and lower temperature. The activity of SOD for both cultivars was declined after 4 d low-temperature treatment. The activity of CAT was declined less in Liangyoupeijiu than in Shanyou 63. The main fatty acids in thylakoid membrane of the two cultivars were palmitic acid, stearic acid, oleic acid, linoleic acid and linolenic acid. And the contents of palmitic acid and linolenic acid were higher than other three. The IUFA (index of unsaturated fatty acid) of fatty acids showed a similar changing pattern to that of O₂^．- content in Liangyoupeijiu, but that was greatly increased in Shanyou 63, which might be more sensitive to low temperature. In the chilling conditions, there was a close relationship between the increase of IUFA and the addition of lipid peroxidation, and both of them were relative to the cold adaptation in rice. The IUFA may be an indicator of chilling-resistant. The changes of fatty acid composition and protection system on membranes may be the key factor of cold adaptation, especially the latter, and the ultimate objective is to alleviate the yield decrease under low temperature.

Key words: Low temperature, Oryza sativa L., Lipid peroxidation, Fatty acid