The Effect Of Salt Stress On Sugar Beet Growth And Endogenous Osmotic Substances

Sugar beet is one of the strong salt-tolerant crops,and the crop for the development and utilization of saline-alkali land.Two different salt tolerance varieties of sugar beet,T510 and 210 were chosen to be the objects of this study and let them growth in 3concentration of NaCl: control group(CK),140mmol/L(LS),280mmol/L(HS).Salt treatment on beet when it grown to cotyledon stage,a pair of true leaves stage,three pairs of true leaves stage.And then study on their different endogenous osmolytes in beet.Salt stress related physiological and biochemical indexes are also be determined and analysed.The results showed that:(1)The two seedlings under salt stress decreased significantly compared with CK in dry weight;Sugar beet in cotyledon period is most sensitive to salt stress;T510 is significantly higer than 210 in dry weight under salt stress,T510 shows strong resistance to salt.(2)The Gs?Tr?Ci and Pn of beet leaf decreased with the increasing of salt concentration,But the photosynthetic parameters of T510 is higher then 210 under salt stress.The chlorophyll content of beet decreased under salt stress,and the reduction of the 210 larger than T510.In addition,salt stress leads to the decline of the Hill reaction and RuBPcase activity.PEPC and MDH activity is significantly increased under LS stress,and it increased most under salt stress in three pairs of true leaves stage.But PEPC and MDH activity is significantly decreased under HS stress.(3)Analysising on five kinds of osmolytes under salt stress,and it shows that: Quaternary ammonium compounds increased significantly,and Betaine concent increased most among of Quaternary ammonium compounds.Observed that Betaine is producted in old leaf,and then transferred to young leaf;The content of sucrose increased,and the reducing sugar content decreased;In addition to fumaric acid all organic acids are increased,and Malic acid concent increased most among of organic acid;The soluble protein content increased,and T510 is significantly higer than 210 insoluble protein;The amino acids content increased except Asp and Glu,smong of amino acids,Asp,Glu,Asn,Ser,Gln,Thr,Ala,Tyr,Phe,Pro reached significant difference between the two seedlings,and most amino acid accumulated in young leaves of sugar beet.Above all,Beets increased salt tolerance by changing the photosynthetic mechanism under salt stress,and endogenous osmotic substance could protect the photosynthetic system.The difference in growth and salt tolerance between the two seedlings by salt is caused by the difference of endogenous osmotic substance content.Betaine plays an important role on salt tolerance of different strains of sugar beet,and both of soluble sugar,malic acid,citric acid are important for salt-tolerance ability.