Effects of Iso-Osmotic Ca(NO3)2 and NaCl Stress on Ionic Contents in Different Organs of Cucumber Seedlings

A hydroponic experiment was applied to investigate the effects of iso-osmotic Ca(NO3)(2) and NaCl stresses on content and distribution of mineral in cucumber seedlings (Cucumis sativus L. 'Jinchun No. 2'). The results showed that under NaCl stress (84 mmol/L) K+ and Mg2+ contents decreased significantly while Na+ content increased significantly in roots, stems and leaves, the Ca2+ content decreased in leaves while accumulated substantially in roots and stems. But under Ca(NO3)(2) (56 mmol/L) stress, Ca2+ content increased while K+ and Mg2+ contents decreased in the roots, stems and leaves, and the decreased degree of Mg2+ content was greater than that of K+ content. In terms of trace elements, NaCl stress aggravated the accumulation of Fe2+, Cu2+ and Zn2+ in roots, while inhibited the absorption of Mn2+ in roots; Ca(NO3)(2) stress promoted the accumulation of Mn2+ and Zn2+ in roots but inhibited Cu2+ absorption. These results suggested that plant growth was inhibited by NaCl stress through increasing the Na+ content and decreasing the K+, Ca2+ contents of leaves, while isotonic Ca(NO3)(2) stress inhibited plant growth mainly through increasing the Ca2+ content and decreasing the Mg2+ content of leaves.