Studies On Effects Of Ethephon And Exogenous Spermine On Polyamines Metabolism And Photosynthetic Physiology At Initial Growth Stage In Sugarcane

Sugarcane varieties ROC26 and B8 were employed as the plant materials for the experiments. There were three experiments in this study. The first experiment was to select appropriate concentration of ethephon. The second experiment was to select appropriate concentration of exogenous spermine. In the third experiment, there were three treatments i.e. CK (water), 200 mg/L ethephon (selected from the first experiment) and 0.1 mmol/L exogenous spermine (selected from the second experiment) were sprayed on the sugarcane leaves at the young shoot stage (four to five leaves). The purpose of the study was to investigate the effects of ethephon and exogenous spermine on polyamines metabolism and photosynthetic physiology at initial growth stage in sugarcane, and to research tentatively the mechanism of ethephon affecting photosynthetic physiology in sugarcane. The main results were as follows:In the first experiment, the three concentrations of ethephon treatments i.e. 0 mg/L (control), 200 mg/L and 300 mg/L were designed. The 200 mg/L ethephon treatment promoted photosynthesis as compared with the 300mg/L ethephon treatment and 0 mg/L (control) ethephon treatment in ROC26 and B8.In the second experiment, the three concentrations of exogenous spermine treatments i.e. 0 mmol/L (control), 0.1mmol/L and 0.5 mmol/L were designed. The 0.1 mmol/L exogenous spermine treatment improved chlorophyll fluorescence parameters and gas exchange parameters, and increased the activity of malic- enzyme as compared with the 0.5mmol/L exogenous spermine treatment in ROC26 and B8.In the third experiment, three treatments i.e. CK, 200 mg/L ethephon treatment and 0.1mmol/L exogenous spermine treatment were designed. There were some differences among the three treatments at many aspects, including polyamines metabolism, chlorophyll fluorescence parameter, gas exchange parameter, photosynthesis enzyme, agronomical characters, and so on.1. For the polyamines metabolisms, the 0.1 mmol/L exogenous spermine treatment highly significantly (at 1% level) increased the contents of endogenous spermidine and spermine, and increased obviously the activity of PAO in leaves of ROC26. And the 200 mg/L ethephon treatment increased obviously the activity of PAO in leaves of B8.2. For the chlorophyll fluorescence parameters, both 200 mg/L ethephon and 0.1 mmol/L exogenous spermine treatments promoted the contents of photosynthetic pigments, and accelerated the photochemical efficiency of PSII (Fv/Fm) in ROC26 and B8. The 0.1 mmol/L exogenous spermine treatment increased obviously the effective quantum yield of PSII (Yield) in ROC26. The yield in the 200 mg/L ethephon treatment was higher than that in the 0.1 mmol/L exogenous spermine treatment in B8. Both 200 mg/L ethephon and 0.1mmol/L exogenous spermine treatments promoted the photochemical coefficient (qP) in B8. The 200 mg/L ethephon treatment improved the diurnal variations of ETR in both ROC26 and B8. The diurnal variations of qP in both 200mg/L ethephon and 0.1mmol/L exogenous spermine treatments did not show significant difference from the control.3. For gas exchange parameters, both 200mg/L ethephon and 0.1mmol/L exogenous spermine treatments improved the diurnal variations of photosynthetic rate (Pn), stomata conductance (Gs) and transpiration rate (Tr) in both ROC26 and B8. The effects in the 200 mg/L ethephon treatment were better than those in the 0.1 mmol/L exogenous spermine treatment. Both 0.1 mmol/L exogenous spermine and 200 mg/L ethephon treatments increased the AQY and Pmax, and descended the LCP in ROC26. The 0.1 mmol/L exogenous spermine treatment had the same effects for B8, but the AQY did not show significant difference between the 200 mg/L ethephon treatment and the control in B8. 4. For photosynthetic enzymes, both 200 mg/L ethephon and 0.1 mmoI/L exogenous spermine treatments increased the activities of malic enzyme in both ROC26 and B8. The 1.1mmol/L exogenous spermine treatment increased obviously the activities of Ca²⁺-ATPase and Mg²⁺-ATPase in ROC26. The 200 mg/L ethephon treatment increased obviously the activities of Ca²⁺-ATPase and Mg²⁺-ATPase in B8.5. For plant height, the 200 mg/L ethephon treatment showed higher the 0.1 mmol/L exogenous spermine treatment and the control in B8.