The Photosynthetic Characteristics,Ion Homeostasis And The Correlation Between Them In Glycine Soja Under Salt Stress

Wild soybean is a species which is closely related to the cultivated soybean.Because of the strong resistance and high protein content,wild soybean has broad application prospects in breeding of new varieties of soybean cultivation,improving the yield and quality of soybean,so it is an important germplasm resource for cultivated soybean improvement.The research of basic metabolism and physiology in wild soybean has significant importance for the protection and utilization of soybean germplasm resources.In this study,common wild soybean and salt tolerant wild soybean were used as experimental materials.The wild soybean seedlings were cultured in the sand,and under neutral salt stress and alkaline salt stress treatments by artificial simulated.After comparing and analyzing two kinds of seedlings photosynthetic function,ion homeostasis and the relationship between them,and their response to different types of salt stress,we tried to reveal the salt stress adaptation mechanism of salt tolerant wild soybean in physiological metabolism process,to explore the evolutionary process of physiological metabolism in two kings of wild soybean under salt stress and the different effects of two different types of salt stress on the wild soybean seedlings.The results showed that two kinds of salt stress both caused the growth inhibition of wild soybean seedlings and the damage in shoot was more serious;besides,tolerance to saline environment in the salt tolerant wild soybean was stronger than that in the common wild soybean.The gas exchange parameters of the wild soybean seedlings showed that the changes of net photosynthetic rate,transpiration rate,stomatal conductance and intercellular carbon dioxide concentration of the salt tolerant wild soybean were all smaller than that of the common wild soybean.The photosynthetic function of salt tolerant wild soybean was more stable,and its variation range caused by salt stress was significantly smaller than common wild soybean.The photosynthetic rate of two kinds of wild soybean was both inhibited under salt stress,but the reason was significantly different.Salt tolerant wild soybean can maintain life activity through effective ion homeostasis adjustment mechanism,there are strategies that salt tolerant wild soybean against adverse habitat,such as accumulated most of the Na+ and Cl-in roots to reduce ion toxicity in leaves;maintained high absorption capacity of major element as SO₄^2-and NO₃^-and accumulated more oxalate in leaves.After analyzing the correlation between ion contents and photosynthetic function in the leaves of two kind of wild soybean under salt stress,I found that in adapting to saline stress,compared to the common wild soybean,salt tolerant wild soybean can keep more ions and photosynthetic capacity parameters showed a positive correlation,it is namely that salt tolerant wild soybean was able to transport more ions to the leaves to maintain higher photosynthetic capacity.Especially,in the adaptation process of alka-line salt stress,the Cl^-,SO₄^2-,Mg²⁺,B³⁺ and Mn²⁺ contents and photosynthetic function presented negative correlation in the common wild soybean,but in salt tolerant wild soybean showed a positive correlation.It was indicating that in the adaptation process of alkaline salt stress,salt tolerant wild soybean was good at regulating the contents of Cl^-,SO₄^2-,Mg²⁺,B³⁺ and Mn²⁺ to maintain higher photosynthetic capacity than common wild soybean.In addition,the growth characteristics,photosynthetic capacity and ion content of the two kinds of wild soybean were significantly decreased under the alkaline salt stress,and it also showed that the alkaline salt caused more damage to plants than the neutral salt stress.