Study On Physiological Responses And The Expression Of Related Genes Of Alfalfa To Stresses Of Saline-alkali And Iron

Alfalfa(Medicago sativa)is an important perennial forage and one of the north's main forage species.Land salinization limits the yield and quality of alfalfa.Iron(Fe)is one of the important nutrients for majority of biological,iron stress has an adverse effect on plant growth and development.By hydroponic tested,zhaodong alfalfa(Medicago sativa zhaodong),an iron deficiency stress resistance variety was selected to be experimental material to iron mixed salt stress in this study.Medicago sativa zhaodong seedlings was carried on the comprehensive research under normal,iron deficiency,high iron,saline-alkali,saline-alkali with iron deficiency and saline-alkali with high iron for 2d and 3d.Mesure the root length,number of fibrous root,solution pH,activty of superoxide dismutase,catalase,peroxidase,malondialdehyde content,chlorophyll content and iron content,as well as analyze the iron metabolism related genes IRT1,FIT1,NRAMP1,AHA2,OPT1 and VIT1 expression quantity,the results are as follows:1.In four alfalfa varieties,after iron deficiency stress chlorophyll content and total iron content in Medicago sativa zhaodong is the highest,SOD,POD and CAT activity and MDA content increased the most slowly,showed strongest iron deficiency stress resistance of Medicago sativa zhaodong.2.Compared with the control,Medicago sativa zhaodong under iron deficiency and saline-alkali with iron deficiency treatment showed significant difference longer in root length and more in fibrous root.And high iron and saline-alkali with high iron treatment groups had no significant difference,and aline-alkali treatment group Medicago sativa zhaodong root length is short and number of fibrous roots is less.Treament with 2d and 3d,the chlorophyll and iron content is shown as: saline-alkali < saline-alkali with iron deficiency < saline-alkali with high iron < iron deficiency< normal ? high iron.3.The pH value of each treatment group solution with the extension of processing time is reduced,in which the lowest solution pH iron is deficiency treatment group.But the pH value increased in slightly aline-alkali with iron deficiency and saline-alkali with high iron treatnent after 3d.The trend of dyeing results by bromocresol purple is same as the above,show that iron deficiency induced rhizosphere acidification in Medicago sativa zhaodong,and alleviate saline-alkali stress in a certain extent.4.The activity of superoxide dismutase,catalase,peroxidase changes showed that Medicago sativa zhaodong seedlings damage is severe under saline-alkali and saline-alkali with high iron stress for 2d;Medicago sativa zhaodong seedlings is the most serious under saline-alkali with iron deficiency for stress 3d.Malondialdehyde content determination results show that the stress order of on the membrane damage on Medicago sativa zhaodong is: normal < high iron < iron deficiency< saline-alkali < saline-alkali with high iron < saline-alkali with iron deficiency.5.The express of plant iron metabolism related genes is related to its function.The expression of AHA2 directly related to plant rhizosphere acidification ability responsed most rapid,showed that through the rhizosphere acidification and relieve the pressure on iron deficiency,rapid response happened to iron deficiency stress in Medicago sativa zhaodong.The expression of NRAMP1 and VIT1 was induced in iron deficiency for 5d,and the expression of transcription factor FIT1,transporters IRT1,OPT1 was highly induced under iron deficiency for 7d.