Effects of presowing treatment with calcium salts, potassium salts, or water on germination and salt tolerance of Acacia seeds

Seeds of Acacia coriacea DC. and A. tortilis (Forsk.) Hayne were soaked for 10 h in distilled water (DW), or in 10 or 50 mM CaCl2, Ca(NO3)(2), KCl and KNO3. Seeds were air dried and germinated in DW or NaCl at their predetermined LD50, 125 mM for A. coriacea and 375 mM for A. tortilis. No treatments significantly increased final germination in DW but DW treatment significantly increased final germination of A. tortilis in NaCl. Treatment with calcium (Ca) or potassium (K) salts did not give a significantly greater final germination than treatment with DW. The rate of germination both in DW and NaCl increased with all treatments. There were significant differences in the Ca and K contents of seeds after treatment, and in the net loss of Ca and K during subsequent soaking in NaCl. In this study seeds treated with CaCl2 absorbed the same amount or less sodium (Na) from NaCl solutions as did DW-treated seeds, while KCl-treated seeds took up as much or more Na as did DW-treated seeds. However, these differences do not appear to be related directly to the effectiveness of presowing seed treatments in increasing germination and germination rate. Treatment with DW and drying is a rapid and simple method for improving germination in saline conditions. Such a strategy may aid the establishment of species that are susceptible to salinity at germination but more tolerant at later growth stages. No added advantage was obtained by including Ca or K salts in the treatment solutions.