Abstract:A regulation effect of calcium nitrate on clone seedlings of Casuarina equisetifolia under NaCl stress was made in pots, with two NaCl concentrations of 10g, 20g NaCl/kgsoil and three Ca(NO_3)_2 concentrations of 0.7g, 1.4g, 2.1g Ca~(2+)/kg soil, and treatments with pure NaCl without Ca(NO_3)_2 as control. Each pot was watered respectively with 1L corresponding salt solution every 6 days. To avoid too high stress causing the death of seedlings, the salt of each treatment was added into each pot in 30 days r...