The effects of salinity on growth, nodulation and nitrogen fixation of Casuarina equisetifolia

The growth, nodulation and nitrogen fixation of Casuarina equisetifolia were compared at six levels (0-500m M NaCl) of salinity in sand culture. Dry weight of nodules, shoots and roots and N content of shoots increased at intermediate levels of salinity (50-100 m M) but decreased at 500 m M NaCl. Nodulation occurred at all NaCl levels, but at 500m M NaCl level, the nodule dry weight declined by 50% from the control. Increasing NaCl concentration of up to 200m M had little effect on the N2-fixation rate, but at 500m M NaCl level the rate decreased to 40% of the control value