Response of'Zhongmu No.1'Alfalfa Seedlings to Mixed Saline-Alkali Stress
In this study,alfalfa(Medicago sativa cv.Zhongmu No.1)was used as experimental mate-rial under mixed saline-alkali stress at concentrations of 0,40,and 80 mmol/L(NaCl,Na2SO4,Na2CO3 and NaHCO3 molar ratios of 1∶1∶1∶1,pH 9.3).The growth indexes,physiological indexes and the expres-sion levels of key genes of the seedlings were measured,which provided a theoretical basis for revealing the mechanism of response to mixed saline-alkali stress.The results showed that the plant height,photosyn-thetic rate,effective quantum yield of PSⅡ photochemistry and the maximum quantum efficiency of PSⅡphotochemistry(Fv/Fm)in'Zhongmu No.1'alfalfa seedlings were significantly inhibited with the intensi-fication of mixed saline-alkali stress(P＜0.05).The accumulation of hydrogen peroxide,superoxide anion,and malondialdehyde gradually increased,while the activity of peroxidase,proline,and soluble sugar content all significantly increased(P＜0.05).Under 80 mmol/L mixed saline-alkali stress,the expression levels of Na+transporter encoding genes MsSOS1,MsNHX1,and MsHKT1 were significantly induced(P＜0.05).In summary,'Zhongmu No.1'alfalfa may mainly respond to mixed saline-alkali stress through the following pathways:(1)high expression of Na+transporter genes such as MsSOS1,MsNHX1,and MsHKT1,promoting Na+efflux,vacuolar segregation and transfer,and avoiding ion toxic-ity to plants caused by excessive accumulation of Na+;(2)enhance antioxidase activity and alleviate oxida-tive damage caused by high pH value.
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