Response of Alfalfa (Medicago sativa L.) Bud Seedling to Saline and Alkaline Stress under Water Culture Conditions

Bud seedlings were used to study short-term effect of different saline and alkaline concentrations on alfalfa root and stem growth. Two neutral salts (NaCl and Na2 SO4) and 2 alkaline salts (NaHCO3 and Na2 CO3) were mixted at 9:1 mole ratio, respectively, to imitate typical saline and alkaline environments. 8 saline concentrations: 0, 10, 20, 40, 60, 80, 100, 120 mmol/L, and 7 alkaline concentrations: 0, 2, 5, 10, 20, 40, 50 mmol/L were selected to determine the stress effects on 5-day, 2-cm bud seedlings. The results indicated that bud seedlings’ root length increased firstly and then decreased as the increase of stress concentrations. On condition of neutral salt stress, 40 mmol/L treatment showed optimum root length, which was 102% times higher than CK, with significant difference (P<0.05). Under alkaline salt stress, 5 mmol/L treatment showed optimum root length, which was 156% times higher than the CK, with significant difference (P<0.05). The effects of the stresses on stem length surpassed root length. And the inhibitory effect of alkaline salt stress on seedlings’ growth in early stage surpassed neutral salt stress.