Response of Casuarina equisetifolia Blancon. seedlings to salinity-flooding stress

Some growth characteristics of Casuarina equisetifolia seedlings affected by salinity-flooding stresses including 0 (freshwater), 50, 100, 150 mili-Molar NaCl and control (without flooding and salinity) treatments were studied in greenhouse as completely randomized design for 120 days. The results showed survival in all treatments was 100%, but in flooding treatment with 150 mM NaCl it decreased to 33.3%. Height growth and diameter growth decreased in various levels of flooding-salinity, and also with increasing salinity. Flooding-salinity stress resulted in decreasing dry biomass of seedlings and creation of adventitious roots in all flooding levels, but the biomass and number of adventitious roots decreased with increasing salinity. Biomass of adventitious roots in flooding levels with freshwater, and flooding with 150 mM NaCl were 6 and 3 times of main roots biomass, respectively. Based on the observations, in all flooding levels, one week after stress, hypertrophy pores were formed in part of the stem located in water. Generally, this research showed that in the studied period in flooding treatment, growth and biomass allocations of organs of C. equisetifolia seedlings decreased with increasing salinity. However, treatments lower than 100 mM NaCl did not display any decrease in survival, but in lower salinity concentrations survival was always 100%. Regarding to creation of abundant adventitious roots and hypertrophy pores showing different resistance aspects to flooding, accomplishment of such a study in next growing seasons can reveal more accurate resistance of C. equisetifoliaseedlings to salinity-flooding stress.