Effects Of Exogenous Pas On Photosynthetic Physiology And Ultra Structure Of Muskmelon Seedlings Under Salt Stress

In order to explore sal-tolerance mechanism of muskmelon under salt stress, effects of different concentration PAs on Relative electric conductivity, content of MDA, content of Pro, photosynthetic pigment contents, photosynthetic parameters, fluorescence parameters and ultra structure of Muskmelon Seedlings using soilless culture under salt stress were investigated in PC greenhouse. The results indicate that:(1)In comparison to NaCl stress, the relative conductivity of leaf of1.Ommol/LSpd, Spm, Put were41.64%,61.73%,66.06%, the content of MDA of1.Ommol/LSpd, Spm, Put were50.32%,56.24%,57.12%. Exogenous PAs of different concentrations can reduce increasing electrolyte leakage, MDA content of muskmelon seeding leaves under salt stress. In comparison to NaCl stress, the content of Pro were24.39%,12.93%and14.42%; Exogenous PAs of different concentrations can reduce decreasing Pro content of muskmelon seeding leaves under salt stress;(2) When the concentration of Spd was1.0mmol/L, the content of Chla, Chlb, carotenoids were1.12times,1.37times and1.18times, reached the peak, reached significant level. When the concentration of Spd was1.0mmol/L, the content of Chla, Chlb, carotenoids were1.12times,1.38times and1.17times, it reached the peak and reached significant level. When the concentration of Spd was1.0mmol/L, the content of Chla, Chlb, carotenoids were1.12times,1.36times and1.17times, it reached the peak and reached significant level. Polyamine treatment significantly increased chlorophyll a, b content and carotenoid under salt stress and maintained higher photosynthesis ability;(3)Exogenous PAs can largely increase photosynthetic pigment contents, Pn, Tr, Gs, Ci. When the concentration of Spd, Spm, Put were1.0mmol/L, net photosynthetic rate were increased by80.7%,70.6%,62.1%compared with the control group; Transpiration rate were increased by24.5%,20.6%,18.9%compared with the control group, intercellular CO2concentration were increased by66.7%,73.3%,78.7%compared with the control group, stomatal limitation value were2.69,2.38,2.15times, it maintained higher PS Ⅱ activity;(4) Exogenous PAs can largely increase Fv/Fm, Fv’/Fm’, Fv/Fo,φPS Ⅱand qP, as well as decreasing NPQ. When the concentration of Spd, Spm, Put were1.0mmol/L, the maximal photochemical efficiency of PS II Fv/Fm were1.05,1.04,1.04times, PS II effective photochemical efficiency of Fv’/Fm’were1.04,1.03,1.02times, PS Ⅱ effective photochemical efficiency of Fv/Fo were99.2%,99.3%,99.4%, PS Ⅱ photochemical efficiency test at φp PS II were1.18,1.14,1.12times, photochemical quenching of qp were1.10,1.2,1.08times, non-photochemical quenching of NPQ were97.2%,97.9%,98.2%. It maintained higher PS II activity;(5)Meanwhile PAs maintained morphology and integrity of membrane system structure, delay the disindegration of organella and keep Ultra structure of organella, maintain high optical activity. Exogenous PAs can improve photosynthetic capacity of Muskmelon under salt stress, on the one hand, because it can alleciate the destruction of PS II under salt stress, on the other hand, it maintain the integrity of membrane system, enhance puotosynthetic parameter.1.0mmol/LSpd can best evidently relieve the injury of salt damage. As a result, exogenous Spd enhanced salt tolerance in Muskmelon seedlings and relieved the salt stress damage to PSII activity and maintained rugular growning through protecting ultra structure of chloroplast.