Germination, Growth and Mineral Ion Concentrations of Casuarina Species under Saline Conditions

Abstract

The response of 11 Casuarina species to salinity (NaCl) at germination (0, 20, 50, 200, 400 mM) and/or as seedlings (0, 75, 150 mM) was studied. Both the final germination percentage and germination rate were reduced in all species by increasing salinity. Treatment of seedlings tended to depress growth, increase the concentrations of Na and Cl in the woody stem and shoot tip and decrease K concentrations in the root and shoot. The species exhibited a wide range of responses to salinity, with some (e.g. C. equisetifolia) showing little growth reduction and no visible injury symptoms, and others (e.g. C. inophloia) showing greatly reduced growth accompanied by shoot tip chlorosis and/or death at 150 mM NaCl. Na and C1 concentrations in the shoot tip in sensitive species treated at 150 mM NaCl were 6-10 times higher than those of controls. In the more resistant species estimated shoot tip concentrations of these ions in plants treated at 150 mM NaCl were approximately the same as or less than those of the external medium. Na and C1 concentrations in the root were higher in these species than in the more sensitive species.