Relationship Of The Cyanide-resistant Pathway And The Photosynthesis Of Arabidopsis Under Chilling Stress And Light-induced Conditions

Plant mitochondria have a respiratory system which is different from the electron transport pathway of the animal’s respiratory system----alternative pathway. To date, the conclusion about the physiological function and physiological significance in plants has not been clear, but it is widespread in plants and plays an important role in them, also, the alternative pathway has been focused on by the research of physiology and biochemistry in plants.With the growth and development of Arabidopsis, we explored the mutual relationship between the alternative pathway and the photosynthesis under different light cycle and light intensity. In this process, with the further growth and development of photosynthetic tissues in light, the alternative pathway increased, the total respiration rate and the photosynthesis rate were also enhanced constantly. Arabidopsis under short photoperiod has a stronger photosynthesis than long photoperiod when Arabidopsis seed were cultured under the different photoperiod of 6h、8h、12h and 16h. Meanwhile, the proportion of the total respiratory which the cyanide-resistant respiration account for has a positive correlation of changes in photosynthesis under different photoperiod. It was also found that the treatment of different photoperiod has no significant effect on the chlorophyll content of Arabidopsis, however, there is a clear difference in leaf morphology of Arabidopsis thaliana treated by different photoperiods.The physiological function of Arabidopsis mutants whose alternative oxidase gene expressed in different levels under stress was studied, it was indicated that the alternative pathway not only contribute to maintain the normal function of cells and tissues, but also can reduce the accumulation of reactive oxygen species of cells body under low temperature and avoid the photosynthetic apparatus from being damaged. Under low temperature stress, the expression of alternative oxidase protein was enhanced and then the operation of cyanide-resistant respiration was strengthened. In this process, the photosynthetic rate of Arabidopsis decreased, the levels of decrease of XX-1 and E-14 whose AOX over expressed was the smallest, whereas AS-12 (anti-sense) was the biggest. After 12h of chilling stress at 6℃, The relative water content、membrane permeability and ROS of XX-1 and E-14 had a smaller range of changes than the wild-type, they also maintained a relatively little generation of ROS and lower oxidative damage, whereas AS-12 generated more ROS and lower oxidative damage than the wild type. From the results mentioned above, we can obtain the conclusion that cyanide-resistant respiration plays an important role in the freezing tolerance of the plants and the protection of the chloroplast.Under the high light stress, the operation of the alternative pathway can regulate the carbohydrate levels in plants, and protect the photosynthetic apparatus from being damaged by the high light. After the high light stress, the content of soluble sugar and starch of XX-1 and E-14 has been increased significantly compared with the control and the starch content of AS-12 increased the most. In the light stress process, in order to dissipate the relatively high excitation energy of the leaves, higher heat dissipation (DIo/CS) of AS-12 started. Meanwhile, decrease of the performance index PIABS which is based on the light absorption is the most obvious.