Effects of silicon on water metabolism and photosynthetic characteristics of Cucurbita pepo L. seedlings under salt stress

[ Objective ] This study aims to explore the protective mechanism of exogenous silicon on water metabolism and photosynthesis of Cucurbita pepo L. seedlings under salt stress , and to provide theoretical reference for salt resistance of C . pepo L.. [ Methods ] Using “ Hanlu 7042 ” C . pepo L. variety as the test material and hydroponic experiment , four treatments were set : Control , silicon treatment ( 0.3 mmol / L Na 2 SiO 3 · 9H 2 O ), salt stress ( 150 mmol / L NaCl ), salt stress+silicon treatment ( 0.3 mmol / L Na 2 SiO 3 · 9H 2 O+150 mmol / L NaCl ) . After 10 days of treatment , root morphology and activity , leaf water con- tent and water potential , photosynthetic parameters , chlorophyll content , chlorophyll fluorescence param- eters , and expression of aquaporin genes were determined. [ Results ] Salt stress inhibited the growth of C . pepo L. seedling roots , and decreased root activity , leaf water content , and leaf water potential and tran- spiration. Salt stress also affected the photosynthetic system , net photosynthetic rate , stomatal conduct- ance , chlorophyll content , and PSⅡ photochemical efficiency. Exogenous silicon improved the root mor- phology and activity of C . pepo L. seedlings under salt stress , also improved plant water status , and leaf water content , leaf water potential , and transpiration by promoting the expression of genes PIP1 ; 2 , PIP1 ; 3 , PIP1 ; 5 , PIP1 ; 7 , PIP2 ; 1 , PIP2 ; 4 , PIP2 ; 6 , and PIP2 ; 8 , PIP2 ; 9 and PIP2 ; 12 . The exogenous silicon also increased the stomatal conductance , chlorophyll content , net photosynthetic rate , PSⅡ maximum photochemical efficiency , PSⅡ actual photochemical efficiency , and photochemical quenching coefficient , decreased intercellular carbon dioxide concentration and non-photochemical quench- ing coefficient , enhanced the photosynthesis of seedlings under salt stress. [ Conclusion ] 0.3 mmol / L sili- con could improve the water metabolism and photosynthesis of C . pepo L. seedlings under salt stress , and thus enhance the ability of C . pepo L. seedlings to resist salt stress.