Effects of NaCl stress on seedling growth and mineral ions uptake, distribution and transportation of two varieties of Carpinus L.

We studied the seedling growth and the absorption, distribution and translocation of mineral nutrients including Na+, K+, Ca2+ and Mg2+ in different organs of seedlings of two Carpinus L. varieties (C. betulus and C. turczaninowii) at different levels of NaCl stress. The results showed that under salt stress, the growth of seedlings of the two varieties was significantly inhibited. As the salt concentration increased from 0.3% to 0.5%, the mortality of seedlings increased, with that of C. betulus higher than that of C. turczaninowii; the dry weight of different parts decreased with the increasing NaCl concentration, and the rate of reduction of total dry weight of C. betulus was higher than C. turczaninowii. As salt stress increased, the absorption of Na+ was increased for the two seedlings at high concentrations of salt from 0.3% to 0.5%, with the content of Na+ in C. betulus higher than that in C. turczaninowii, and Na+ in C. betulus was concentrated in the stem while that in C. turczaninowii mainly in the roots. K+ in the leaves remained a higher level, but Ca2+ and Mg2+ contents changed little. K+/Na+, Ca2+/Na+ and Mg2+/Na+ ratios in different organs decreased with increasing salt stress, and were significantly lower than the control. In salt-treated groups, ion ratios in the stem and leaves of C. turczaninowii seedlings were higher than in C. betulus. The ion-selective transport capacity from root to stem of C. betulus seedlings decreased, and that from stem to leaves dropped first and then increased with the increasing NaCl stress; however, the ion-selective transport capacity from root to leaves of C. turczaninowii seedlings was significantly higher than that of C. betulus. Comprehensive analysis showed that the seedlings of two Carpinus varieties were adversely affected by severe salt stress, resulting in the accumulation of salt ions in plants, but the ability of C. turczaninowii to keep balance of ion in the plant was higher than that of C. betulus, and the former also had stronger ability than the latter in salt tolerance.