Physiological Responses Of Broussonetia Papyrifera Seedings To Salt Stress

With the continuous expansion of the salinized land area in the world,salt stress has become one of the main factors restricting the development of agriculture and forestry.Broussonetia papyrifera belongs to the genus Broussonetia in Moraceae,which is widely distributed in China.It is not only tolerant to salt,barren and drought,but also rich in crude protein.Thus,it has important ecological and economic values.In this study,the B.papyrifera was treated with 0,50,75,100,150,200 and 300 mmol·L-1 Na Cl solutions,and the variations of photosynthetic gas exchange parameters,the contents of photosynthetic pigments,organic osmotic regulators,membrane lipid peroxidation and antioxidant enzyme activity under different concentrations of Na Cl were analyzed,and the physiological changes under salt stress were studied,this would provide a theoretical basis for further study on salt tolerance mechanism of B.papyrifera.The main conclusions were as follows:1.The contents of chlorophyll a,chlorophyll b and chlorophyll(a+b)in the leaves of B.papyrifer decreased with the increase of salt concentration,while the net photosynthetic rate(Pn),stomatal conductance(Gs),intercellular CO2 concentration(Ci)and transpiration rate(Tr)of mature leaves also decreased.The results showed that photosynthesis was inhibited under salt stress,and the inhibitory effect increased with the increase of salt concentration.2.The contents of soluble proteins,soluble sugars and free proline in leaves and roots of B.papyrifera increased under salt stress,indicating that under salt stress,soluble proteins,soluble sugars and proline were involved in osmotic stress as osmotic regulators,thereby reducing osmotic stress caused by high salt..3.Under salt stress,the activities of superoxide dismutase,ascorbateperoxidase and glutathione reductase in the leaves of B.papyrifer were increased,indicating that the antioxidant enzyme system was activated and the removal of active oxygen substances in the body was accelerated,thereby reducing the oxidative damage caused by salt stress.4.According to the change of dry weight and fresh weight of B.papyrifera under salt stress,the salt tolerance threshold of B.papyrifera was 6.75~6.90‰.In summary,the organic osmotic regulators,the antioxidant enzymes and non-enzyme antioxidants were increased in B.papyrifera under salt stress,thus the osmotic potential was maintained at a proper level and the peroxidation of membrane lipids was inhibited,thereby enhancing the salt tolerance.