Comparison Of Physiological Characteristics Of Salt And Alkali Tolerance In Kochia Sieversiana And Lycopersicon Esculentum

One of global problems is soil salt-alkalinization.According to the nature of the salt contained in the soil,stresses which affect plants can be divided into salt stress,alkaline stress and mixed salt-alkaline stress.In nature,soil alkalization and salinization usually co-occur and interweave with each other to form mixed salt-alkaline stress.However.if people want to solve the problem in essence,salt and alkaline stress must be separated to study considering as the two different stresses.A halophyte Kochia sieversiana C.A.Mey.and a non-halophyte tomato {Lycopersicon esculentum Mill.)were chosen as our experimental materials.Seedlings of Kochia sieversiana were applied with salt stress(120mM,NaCl:Na2SO4=1:1,)or alkali stress(120mM,NaHCO3:Na2CO3=1:1),and seedlings of tomato were applied with salt stress(50mM,NaCl:Na2SO4=9:1,)or alkali stress(25mM,NaHCO3:Na2CO3=9:1).The threat change indicators including RGR,water content,inorganic ions and organic solutes were determined to explore and compare characteristics of salt and alkali stress acting on K.sieversiana and L.esculentum and the responses of K.sieversiana and L.esculentum to them from growth,ion transport,osmotic adjustment and ion toxicity and so on.The main results and conclusions were as follows:(1)Cotyledon scar of K.sieversiana had restrictive effects on Na+ transferring towards up,however,cotyledon scar of L.esculentum had not restrictive effects on Na+,which was one of the main reasones that the two plants differed in salt and alkali tolerance.(2)Low salinity stress(50mM salt stress,25mM alkali stress)inhibited the growth of tomato roots and shoots to a certain extent,and 25mM alkali stress significantly reduced water content of tomato leaves;high salinity stress(120mM salt stress,120mM alkali stress)did not inhibit significantly growth of K.sieversiana;salt and alkali stresses reduced significantly the flow rate of xylem sap of the two under low or high salinity stress.(3)The two plants accumulated inorganic ions and organic acids in the vacuoles,and accumulated organic solutes in the cytoplasm.However,different solutes differed in their contributions to osmotic adjustment.For K.sieversiana,Na+,K+ Cl-and OA were all important osmolytes under salt stress;compared to roots,Na+,Cl-contributions were weakened,K+ and organic acids contributions were enhanced in leaves;under alkali stress,Na+,K+ and organic acids were important osmolytes in the vacuoles.The contributions of soluble sugars and proline to osmotic adjustment in roots of K.sieversiana were much greater than those of in leaves.For tomato plant,compared to K.sieversiana,the osmoregulation role of OA was no longer outstanding,and Na+.K+ and Cl-were the main osmolytes under salt stress,but the contribution of K+ in leaves was greater than in roots;under alkali stress,with the exception of Na+ K+,the roles of inorganic anions Cl-and SO42-stood out,while the role of organic acids got smaller,especially in tomato plant roots.(4)Under both stresses.OA was dominant component to maintain ion balance in the tomato plants roots and leaves.With the exception of OA,Cl-was the dominant component for anion compositioI under salt stress;and SO42-was the dominant component to ion forms under alkali stress,which was similar to K.sieversiana.OA was dominant component for anion composition inK.sieversianaplants roots and leaves under alkali stress;however,under salt stress,Cl" played an important role in anion composition in roots of K.sieversiana.