Effects Of Methanol On Photosynthesis Of Cotton At Flowering And Boll-forming Stage

Numerous studies have shown that exogenous application of methanol can enhance the growth of C3plants and methanol can be used to promote plant growth, especially under high light intensity and hightemperature. However, methanol metabolic pathways in plants are not clear and how to regulatephotosynthesis has not been reported. To proof the effect on Rubisco and photosynthetic diurnal variationcharacteristics, the aqueous methanol was sprayed on foliar of cotton (Gossypium hirsutum L.) under thehigh temperature and light in Xinjiang summer. Researching about the mechanism of methanol to enhancephotosynthisis of cotton can help to reveal the methanol to enhance plant growth mechanisms. Meanwhile,those can provide theoretical basis for widely use in agriculture. The experimental results are as follows:Compared with the control group, the Rubisco carboxylation activity was increased by40%~60%during7d~56d after methanol treatment; Rubisco contents and soluble protein contents were enhanced10%~20%in cotton foliage. Methanol and its possible metabolites enhanced the efficiency ofphotosynthetic carbon fixation in the process of carbon assimilation by the increase of carboxylationreaction rate. Rubisco carboxylase activity was not directly proportional to the increase of Rubisco contents.So methanol increased Rubisco carboxylase activity may be related to other factors.In pot experiments, the net photosynthetic rate (Pn), stomatal conductance (Gs), intercellular CO2concentration (Ci) and transpiration rate (E) of cotton main stemleaves had different rates of increase after1d~3d of methanol treatment. And the results also showed that the net photosynthesis rate and theintercellular CO2concentration were increased by15%and20%, respectively, it is significantly higher thancontrols during7d~56d after spraying. In treatment tests, the transpiration rate diurnal variation curvespresented no two peaks, no valley and no midday depression. The intercellular CO2concentration ofmethanol group showed continued to decline from8:00to17:00comparing with control, and this changewas negatively correlated with changes in the photosynthetic rate before14:00.In field experiments, exogenous methanol treatment increased Chlorophyll a, Chlorophyll b content and Carotenoid content of cotton foliage at Flowing and Boll-forming Stage. There was a correspondingrelation of time between the changes of total Chlorophyll content and Rubisco carboxylation activity ingeneral.