Effects Of Molybdenum Application On Compositions Of Thylakoid Membrane In Winter Wheat Under Low Temperature Stress

Based on the advance in plant molybdenum (Mo) nutrition, the pot culture experiments were conducted to investigate the effects of molybdenum on photosynthetic pigment, protein, and fatty acid of thylakoids in winter wheat (Mo efficient cv. 97003 and Mo inefficient cv. 97014) under low temperature stress. The main results are as follows:1. The effects of molybdenum on the contents of photosynthetic pigments in winter wheat (Mo efficient cv. 97003 and Mo inefficient cv. 97014) were investigated under low temperature stress. The results showed that the contents of chlorophyll a, chlorophyll b and total chlorophyll were increased significantly by molybdenum application under low temperature stress, which might mean that the capacity of light absorption and electron transfer were improved by the application of molybdenum.The content of carotenoid increased which may reduce the photoinhibition and enhance the scavenging of reactive oxygen species in winter wheat. The increase rate of carotenoid content in Mo-fertilized winter wheat was the highest than those in chlorophyll a, chlorophyll b, which indicated that the response of Mo to carotenoid was more sensitive. Genotypic differences in the content of photosynthetic pigments were found in Mo efficient cv. 97003 and Mo inefficient cv. 97014. The decrease rates of chlorophyll a, chlorophyll b and total chlorophyll contents in Mo inefficient cv. 97014 were higher than Mo efficient cv. 97003 in Mo-deficient treatment, which indicated that Mo-inefficient cultivar 97014 was more sensitive to be injuried than Mo-efficient cultivar 97003 under cold stress.2. Effects of molybdenum (Mo) on pigment-protein and polypeptide components of thylakoids in winter wheat (Mo efficient cv. 97003 and Mo inefficient cv. 97014) were investigated under low temperature stress. The results indicated that in the two winter wheat cultivars, the protein content of thylakoids in the leaves of Mo-deficient and Mo-fertilized treatment decreased gradually with the prolongation of low temperature stress, whereas the decrease rates of the protein content of Mo-deficient treatment in Mo inefficient cv. 97014 were higher than those in Mo efficient cv. 97003, which further confirmed that Mo-inefficient cultivar 97014 was more sensitive to be injuried than Mo-efficient cultivar 97003 under cold stress. With the prolongation of low temperature stress, the D1/D2 dimer and PsaA/B contents of thylakoids increased at first 2 or 4 days under low temperature stress, and then decreased, whereas no change in the D1/D2 dimer and PsaA/B was detected in Mo treated winter wheat under all the low temperature stress. Two new proteins with a molecular mass about 40 KD and 37 KD appeared at the second day under low temperature stress in thylakoids of Mo-fertilized treatment, whereas the two proteins were found until the 4th day under low temperature stress in Mo-deficient treatments. In addition, the contents for 40 KD and 37 KD proteins in Mo-fertilized winter wheat significantly higher than those in Mo-deficient treatmen of both cultivars under low temperature stress. These results indicated that Mo application might promote the low-temperature-induced synthesis of certain proteins. However 40 KD and 37 KD function is needed to be further studied.3. The effects of molybdenum on fatty acid of thylakoids in winter wheat (Mo efficient cv. 97003 and Mo inefficient cv. 97014) were investigated under low temperature stress using Gas Chromatography analysis. Mo application increased the unsaturated fatty acids, the U/S, the IUFA and decreased the saturated fatty acids in leaf thylakoids of both cultivars under cold stress. These results indicated that Mo application might enhance the conversion of the saturated fatty acids to unsaturated fatty acids which might help to maintain the stability of PSI and PSII under low temperature stress. The 18:3, USFA contents and the IUFA in leaf thylakoids in both winter wheat cultivars increased gradually with the prolongation of low temperature stress. However, the 18:3, USFA content and the IUFA of leaf thylakoids significantly increased in Mo-deficient treatment at the 4 day under low temperature stress, but significant increase was found in Mo-efficient treatment at the 2 day under low temperature stress. Genotypic differences in response of activities of molybdenum on fatty acids of thylakoids were found in Mo efficient cv. 97003 and Mo inefficient cv.97014 under low temperature stress. Throughout the process of low temperature stress, the unsaturated fatty acids, the U/S and the IUFA of thylakoids in Mo inefficient cv. 97014 were less than those in Mo efficient cv. 97003.