Effects of Na_2SO_4 Stress on Growth and Photosynthetic Physiology of Elaeagnus angustifolia Seedlings

A pot experiment was conducted to investigate the effects of salt stress( 0,60,120 and 180 mmol·L- 1 Na2SO4) on the growth and photosynthetic characteristics of Elaeagnus angustifolia seedlings. The results showed that:( 1) the plant growth was significantly inhibited by salt treatment. The tree height,number of branches,specific leaf area,total leaf area,leaf number per plant,and the biomass accumulation of stem,leaf,shoot and wholeplant of Na2SO4-stressed seedlings were all significantly lower than those of the control( no salt-stressed). With the salt concentration elevated,the above-mentioned growth parameters generally exhibited a decreasing trend,while the root-shoot ratio increased significantly from control's 0. 153 1 to 180 mmol·L- 1Na2SO4-stressed seedlings' 0. 348 7.( 2) The photosynthetic capacity decreased by salt stress significantly. The net photosynthetic rate( Pn), stomatal conductance( Gs),intercellular CO2content( Ci) and transpiration rate( Tr) of seedlings treated by 180mmol·L- 1Na2SO4were only 71. 57%,30. 85%,67. 15% and 51. 65% of the corresponding control,while the stomatal limitation value( Ls) and water use efficiency( WUE) of 180 mmol·L- 1Na2SO4-stressed seedlings were 1. 91 and 1. 38 times that of the control seedlings,respectively. With the salt stress aggravated,the Pn,Gs,Ciand Tr,and Lsand WUE generally exhibited a decreasing,and increasing trend,respectively. The decreased Pnof stressed seedlings was mainly attributed to stomatal restrictions.( 3) The various growth parameters of height,total leaf area,leaf number per plant,specific leaf area,stem biomass,leaf biomass and whole-plant biomass accumulation,and photosynthetic parameters of Pn,Gs,Ciand Trhad all extremely significant and negative correlation with salt stress intensity. The total leaf area and leaf number per plant were significantly or extremely significantly correlated with leaf photosynthetic parameters. There was also significant or extremely significant correlation between parameters of growth and photosynthesis and parameters of seedling height and biomass accumulation.