Effects of salt stress on seedling growth of alfalfa (Medicago sativa) and ion distribution in different alfalfa organs.

The effects of different concentrations of NaCl(0,0.1%,0.3%,0.5%,0.7%,0.9%) on growth of alfalfa(Medicago sativa)(survival rate,root length,stem length,leaf number) and the contents of Na+,K+,Ca2+,Mg2+ in the different organs were assessed and the ratio of K/Na,Ca/Na,and Mg/Na were analysed.The survival rate,root length,and stem length were all negatively correlated with salt concentration,except when the NaCl concentration was ≤0.1%.The content of Na+ in root,stem and leaves and the content of Ca2+ in roots were all positively correlated with salt concentration.However,the contents of K+ and Mg2+,and the ratios of K/Na,Ca/Na,Mg/Na in roots,stems and leaves significantly decreased with an increase of salt concentration.Salt stress on alfalfa caused significant differences in the comparisons.The reason for salt injury and salt-tolerance in alfalfa are discussed in relation to ion toxicities.