na, k and ca contents in roots and leaves of three glycine species differing in response to nacl treatments

It has been shown that three wild soybean species, Glycine soja, G. tomentella and G. tabacina, in Taiwan had different response to root-zone salinity and differences in leaf accumulation of Na and K might be responsible for the response. To further understand the mechanisms in relation to the differences among species in leaf accumulation of Na, K and Ca, in this study I compared the distribution of Na, K, and Ca not only in leaves but also in roots and calculated the sum of the ion contents in leaf and root (= ion content in roots + ion content in leaves) of the three soybean species receiving four different levels of NaCl treatments, 0, 17, 51 and 85 mM. Analysis of contents of K and Na in leaves and roots revealed that G. soja, the most sensitive species, and G. tomentella, the most tolerance species had similar sum of root and leaf Na contents under the same NaCl treatment, however, the former had significantly high leaf Na content than the later. G. tabacina, the medium sensitive species, had the least sum of root Na and leaf Na contents and medium leaf Na content. In G. soja, increasing accumulation of Na in leaves with increasing treatment NaCl concentration might hamper the uptake of K in roots resulting in decreases in the sum of K contents in roots and leaves. There is no evidence that salinity could impair Ca uptake in the three wild soybean species. These results suggest that differential sensitivity to root-zone salinity among the three species is mainly due to their differential ability to control the allocation of salt away from leaves and to some extent restrict Na uptake at root level.