Salt Tolerance of Trifolium alexandrinum L. I. Comparison of the Salt Response of T. alexandrinum and T. pratense

Trifolium alexandrinum and Trifolium pratense were grown in solution culture at salinity levels of 50, 100, 150 and 200 mM NaCl. Trifolium alexandrinum survived at all salt treatments. Salt-induced growth reductions of 30 and 47% occurred at 50 and 100 mM NaCl, respectively, mostly affecting stems. Plants still survived at 150 and 200 mM NaCl. This species can therefore be considered moderately salt tolerant. Trifolium pratense showed a low survival potential at salt treatments of 100 mM NaCl or higher, and the dry weight production of all plant parts was considerably affected at moderate salt levels. Thus T. alexandrinum is considered more salt tolerant than T. pratense. The distribution and contents of K+, Na+ and Cl- in both species indicate that T. pratense translocates Na+ and Cl- linearly with increasing salt treatment into stems and leaves, whereas low foliar Na+ and Cl- contents in T. alexandrinum suggest some mechanisms that control the ion distribution in the different plant parts. Salt-induced changes of the K+ and Ca2+ contents of the different plant parts of both species are discussed.