Effects Of High-temperature And Weak-light On Lipid Metabolism During Rice Grain-filling Stage

This article was focus on four kinds of rice varieties in experiment, they were Akitakomachi(Japonica), Koshihikari(Japonica), IR72(Indica) and Gangyou527(Hybrid rice). Put these four kinds of varieties under the condition of high-temperature and weak-light during heading stage to mature period, and took the natural environment as control group, analyzed the influence and mechanism of high-temperature and weak-light on lipid metabolism during rice grain-filling stage. The experiment results were as follows.1 The effects of high temperature and weak light on lipid synthesis1.1 The effects of high temperature and weak light on crude fat content accumulationThe crude fat (CF) content showed a single-peak changing. The CF content of Koshihikari, IR72 and Gangyou527 under high temperature and weak light was less than the control, respectively. The differences between the three varieties reached a significant level. But the CF content of Akitakomachi was higher than control. It illustrated that the responses were different of the four varieties under high temperature and weak light.1.2 The effects of high temperature and weak light on unsaturated fatty acidThe contents of Akitakomachi, IR72 and Gangyou527 under high temperature and weak light were higher than control, but the differences were not reached significant levels. The content of Koshihikari during early rice grain filling stage was lower than control, but it was higher than control after 18 days of heading to maturity. It illustrated that the environment of high temperature and weak light was benefit for accumulation of unsaturated fatty acid.1.3 The effects of high temperature and weak light on fatty acid compositionAkitakomachi, Koshihikari and IR72 were detected 10 kinds of fatty acid components, and Gangyou527 was detected 13 components. The highest content of fatty acid in the four varieties was all OA, LA and PA.The fatty acid contents of the four varieties under high temperature and weak light were different compared to control. The OA contents of Akitakomachi and 1R72 were higher than control; Koshihikari and Gangyou527 were lower than control. The LA contents of the four varieties were lower than control. The PA contents of Akitakomachi and Koshihikari were lower than control, but IR72 and Gangyou527 were higher than control.1.4 The effects of high temperature and weak light on PPase activityThe PPase activity of the four varieties showed a single-peak changing. The PPase activities of the three varieties were greater than control except Akitakomachi. The PPase activity of Akitakomachi was significant higher than control, and the other three varieties were very significant less than control. The PPase activity was reduced under high temperature and weak light. It illustrated that the responses were different of the four varieties under high temperature and weak light.2 The effects of high temperature and weak light on lipid decomposition2.1 The effects of high temperature and weak light on lipase activityThe lipase activity showed a single-peak changing during rice grain-filling stage. The lipase activities of the four varieties were lower than control, Akitakomachi and IR72 was significant less than control and Gangyou527 was very significant less than control.2.2 The effects of high temperature and weak light on LOX activityThe LOX1 was not detected in Koshihikari and IR72. Akitakomachi was lower than control and Gangyou527 was higher than control. It showed that the different reactions of different varieties under such factors.The LOX2 activity was not detected of the four varieties.The LOX3 activities of the three varieties were very significant higher than control apart from Akitakomachi which was very significant lower than control. It indicated that the responses were also different of the four varieties under high temperature and weak light.2.3 The effects of high temperature and weak light onβ-oxidationThe acetone contents of the four varieties showed a single-peak changing. Theβ-oxidation of the four varieties was higher than control and Gangyou527 was significant higher than control. It indicated that theβ-oxidation was promoted under such factors.3 Correlation analysis3.1 Correlation analysis between Ppase activity and crude fat contentThe PPase activity was positively correlated with crude fat content (the correlation coefficient was 0.77**) of Akitakomachi under high temperature and weak light, the control reached a positive level (the correlation coefficient was 0.71). The PPase activities of Koshihikari, IR72 and Gangyou527 under treatments and controls are all positively correlated with crude fat content (the correlation coefficient was 0.79* and 0.80*,0.76* and 0.85*,0.86* and 0.93*, respectively). It illustrated that PPase played an important role in the accumulation of crude fat content.3.2 Correlation analysis between lipase activity and FFA contentThe lipase activities of Akitakomachi, Koshihikari and IR72 under treatments and controls are all positively correlated with FFA formation rate (the correlation coefficient was 0.83* and 0.89*,0.90* and 0.81*,0.90* and 0.80*, respectively). The lipase activity was significant positively correlated with FFA formation rate (the correlation coefficient was 0.96**) of Gangyou527 under high temperature and weak light, the control reached a positive correlation (the correlation coefficient was 0.91*). It illustrated that lipase activity played a key role in the accumulation of FFA.