GLYCINEBETAINE APPLICATION ALLEVIATES SALINITY DAMAGE TO ANTIOXIDANT ENZYME ACTIVITY IN ALFALFA

We investigated whether glycinebetaine (GB) application could alleviate salinity-induced damage in alfalfa (Medicago sativa L.). A hydroponic culture experiment was employed, and thirty-day-old alfalfa seedlings were subjected to 0, 5, 10, and 20 mM GB and exposed to a 1% salt regime, with a nutrient solution as the control. Marked decrease was detected in the vertical shoot growth rate (VSGR), vertical root growth rate (VRGR), plant biomass, and normalized relative transpiration (NRT) due to the salinity stress, and significant increase was also detected in MDA, soluble protein content, and SOD, CAT, and POD activities. The application of GB increased VSGR, VRGR, SOD activity, and decreased the MDA, soluble protein content, and Na+/K+ ratio compared to the treatment without GB application. Alfalfa treated with 5 mM GB exhibited higher VSGR, VRGR, plant biomass, NRT, SOD, POD, and lower CAT activity when compared to other levels of GB application. Moreover, lower MDA and soluble protein contents were also observed in the 5 mM GB application treatment relative to the non-GB treatment. These results indicated that the GB-enhanced salinity tolerance in alfalfa was attributed to the elevation in SOD and POD activities, and the decrements in the MDA and soluble protein contents. It could be concluded that the 5 mM GB application was the proper concentration to ameliorate the damage of salt on alfalfa.