Effects Of Exogenous Methanol On Metabolism Of Photorespiration And Antioxidation In Cotton

The recent research findings suggest that exogenous methanol?MeOH? can inhibit glycolate oxidase?GO? in C3 plant such as cotton, and can abate the photorespiration of glycolate pathway, thus improve the photosynthesis of cotton. But, it is unclear that are the effects on downstream metabolize of GO by MeOH-treated in cotton. This test choose summer weather?highlights, high temperature? in upland cotton?Gossypium hirsutum L.? in Xinjiang, sprayied exogenous 30% MeOH on cotton of bud period in a pot experimentin, investigated the related enzyme activity change that are GO downstream enzymes, tested somephotorespiratory intermediates content change in cotton, and studied on photoinhibition that is closely related to photorespiration. To explore the cotton photorespiratory mechanism, the cotton was made by MeOH-treated in the arid zone under the high temperature condition. The results showed that:?1? MeOH treatment resulted in a 17.80% decrease in hydrogen peroxide?H₂O₂? content as compared with the controls in the cotton leaves; In control leaves, the H₂O₂ contents were lower in rainy days than in sunny days, and were decreased as the temperature; the result also showed that the accumulation of H₂O₂ and photoinhibition were inhibited by exogenous MeOH treatment in cotton leaves.?2? The activities of catalase?CAT? were greatly increased in cotton leaves, and CAT activity was changed with temperature; CAT activities increased significantly in MeOH-treated samples compared with the control samples by 53.40%; a correlation between the contents of H₂O₂ and CAT activity was observed.?3? MeOH treatment resulted in a 39.38% increase in peroxidase?POD? activity as compared with the controls; POD activities were influenced by the fluctuations of temperature; the results showed that POD play an important role to alleviate of H₂O₂, to reduce the active oxygen damage in the cotton.?4? We determined the contents of malondialdehyde?MDA? in response to MeOH treatment. Contents of MDA decreased significantly in MeOH-treated samples by 18.99% lower than the control samples; MDA content, which increased in the high temperature condition, significantly inhibited in cotton leaves; the magnitudes of MDA content fluctuation were the same trend with H₂O₂ content change.?5? Anthocyanin content treatment samples increased than the control by 29.83%; whether is on sunny or rainy day, anthocyanin contents treatment group were higher than the control group. The results shown that can increase the anthocyanin content significantly, eliminate H₂O₂ and other active oxygen species, and reduce the photoinhibition damage after MeOH-treated in conditions of high light intensity and temperature.?6? The glutamate:glyoxylate aminotransferase?GGAT? activity was in treatment smaples lower than in the control by 2.82%; although GGAT activity in treatment group were lower than the control group, but MeOH treatment had no significant effect on GGAT activity.?7? Treatment group of serine:glyoxylate aminotransferase?SGAT? activity on average 6.49% lower than the control, the weather has a certain influence on SGAT activity, the results suggests that the activity of SGAT was inhibited by MeOH-treaed.?8? Thehydroxypyruvate aminotransferase?HPR? activity was increasedin treatment smaples than the control by 9.65% on average, the temperature is a bigger influence on the HPR activity.?9? Treatment samples of glycerate content are higher than the control and increased by 22.60%. The results displayed glycerate content increased by weather and MeOH dual function.The experimental results suggest that there may be other photorespiration pathway in cotton plants under highlights and high temperature conditions.