Studies on Ion Distribution in White Clover Seedling under Salt Stress

The contents of Na+、K+ and Mg2+ in different organs of salt-tolerant white clover variety 1212 and salt-sensitive variety 83-159 under different salt stresses were measured with ICP-MS.The objective of this study was to elucidate the effects of salt stress on the absorption and distribution of Na+ and K+ in different organs of white clover seedling.The results showed that with the aggravation of salt stresses on white clover seedlings the contents of Na+ in roots,stems and leaves increased.However,the increase of Na+ in roots were much more lower than in stems and leaves so that more Na+ were accumulated in above-ground parts.The content of Na+ in stems of salt-tolerant variety was higher than that of salt-sensitive variety,but in leaves it was lower than salt-sensitive variety.The contents of K+ decreased in different organs of white clover seedlings with salt stress increased.The content of K+ in roots and stems of salt-tolerant variety 1212 were higher than that of salt-sensitive variety 83-159,but in leaves it was lower than salt-sensitive variety.The contents of Mg2+ was not much affected by salt stress,and it changed irregularly.The ratio of K+/Na+ and Mg2+/Na+ decreased with the salt concentration increasing.The ratio of K+/Na+ and Mg2+/Na+ in roots and leaves of salt-tolerant variety were higher than that of salt-sensitive variety,which showed that it was easier for salt-tolerant variety to maintain normal growth by keeping the balance of K+,Na+ and Mg2+ in organs than salt-sensitive variety.With the increase of salt concentration,SK,Na-transport selectivity of root-stem declined and SK,Na-transport selectivity of stem-leave increased which could accumulate more Na+ and less K+ in stem.It showed that stem was an important Na-K bank,and it could alleviate salt stresses through the output of K+ and input of Na+.