Effects of calcium on ion absorption and distribution
of virus-free potato seedlings under NaCl stress

【Objectives】Soil salinization seriously affects the growth and development of potato, decreases its yield and quality. In this paper, the influence of different concentrations of CaCl2 on the ion absorption, distribution and transportation of virus-free potato seedlings under the stress of NaCl was studied to explore the regulating mechanism of calcium against the NaCl stress of potato,providing a theoretical basis and technical support for the potato production in saline soil.【Methods】 Tissue culture method was used with ‘Kexin No.1’ as tested potato cultivar. The medium of MS+2mg/L B9+3% sucrose+0.9% agar was chosen and 0,5, 10, 15 and 20 mmol/L CaCl2 and 0, 25, 50 and 75 mmol/L NaCl were added to make treatment mediums. The subcultured virus-free seedlings were cut into single stem segments and inoculated 30 days. The biomass and Na+, Cl-, K+, Ca2+, Mg2+, P accumulation of the virus-free seedlings were measured, and the ratios of Na+/K+, Na+/Ca2+, and Na+/Mg2+ and the SK、Na, SMg、Na and SCa、Na values in root and stem were calculated. 【Results】 The growth of potato seedlings was inhibited under NaCl stress. With the increase of NaCl stress concentration, the fresh and dry weights of seedlings decreased significantly; the Na+ and Cl- contents increased significantly, K+ content decreased significantly, Ca2+ and Mg2+ contents decreased in all the tested parts of seedlings; P contents were reduced in stems and leaves, but increased in roots. Consequently, the ratios of Na+/K+, Na+/Ca2+ and Na+/Mg2+ were increased, the SK、Na, SMg、Na values in roots and stems gradually reduced, and the SCa、Na value increased first and then decreased. Addition of 10 mmol/L of CaCl2 under the NaCl stress of 0, 25, 50 mmol/L, and 15 mmol/L of CaCl2 under 75 mmol/L of NaCl increased the biomass accumulation of potato seedlings obviously. With the addition of CaCl2, the Na+ accumulation in seedlings obviously reduced, Cl- content increased significantly, K+, Ca2+ and Mg2+ contents increased, and P content decreased at first and then increased. Under all the NaCl stress treatments, the addition of suitable amount of CaCl2 could effectively reduce the Na+/K+, Na+/Ca2+, Na+/Mg2+ratios in various organs of seedlings, improve SK、Na, SMg、Na, SCa、Na values, increase the selection of up ground transport of K+, Ca2+ and Mg2+, inhibit that of Na+, maintain intracellular ionic balance and relieve the nutritional deficiency caused by salt stress.【Conclusions】 Adding exogenous calcium under NaCl stress can effectively improve the ion balance of potato virus-free seedlings, promote the absorption of nutrients, reduce the transportation capacity of Na+ to leaves, enhance the selection transport of K+, Ca2+, Mg2+ to aboveground, which is one of the physiological mechanisms for calcium alleviating salt stress.