Abstract: The contents of K,Ca,Na and Mg in different organs of Bruguiera gymnorrhiza seedlings cultured in sand bases with solutions of 400 mmol·L^-1 NaCl and different concentrations of CaCl₂ were determined.In the treatment of 400 mmol·L^-1 NaCl,Na was largely accumulated in organs,which caused the decrease of K/Na and Ca/Na,and decreased dry matter accumulation in seedlings.Supplemental CaCl₂ decreased the accumulation of Na in seedlings,increased the ratios of K/Na and Ca/Na and the accumulation of dry matter,and thereby,mitigated salt stress.The suitable concentration of CaCl₂ was 10～15 mmol·L^-1.It was concluded that B.gymnorrhiza seedlings cultured at high salinity accumulated more metal ions,which enhanced osmotic adjustment of plants,and kept highly selective absorption of K/Na.These characteristics are the main physiological mechanisms of the adaptation of B.gymnorrhiza to high salinity in estuary and coast,while suitable Ca/Na in soil is one of the important causes that B.gymnorrhiza can survive and regenerate in high salinity coast.

Key words: Mangrove, Bruguiera gymnorrhiza seedlings, Salt stress, Ca effects, root separation, green manure, carbon source, root interaction, microbial diversity