Effect of salinity on the germination of three species of the Acacia genus (A. karroo, A. saligna, and A. tortilis)

This scientific paper explores the impact of soil salinity on plant growth, with a particular focus on the relationship between salt tolerance and seed germination. To investigate this, three species of Acacia (Fabaceae), namely A. karroo, A. saligna, and A. tortilis, were selected, and their seeds were collected from Algeria. To overcome seed coat inhibition, seeds were treated with concentrated sulphuric acid, followed by a wash with distilled water before being sown in a culture medium containing varying concentrations of salt, specifically sodium chloride (NaCl) ranging from 0 to 600 mM. The germination tests were conducted over a 21-day period, with measurements taken at intervals of three days, and both the final germination percentage (FGP) and mean germination time (MGT) were calculated. The results showed that at 600 mM NaCl concentration no germination occurred during the experiment. The germination rates exhibited three phases, an initial latency phase, a second exponential phase of accelerated germination, and a third plateau phase. A. karroo seeds demonstrated the highest salt tolerance, germinating under high salinity conditions of 400 mM NaCl, with a FGP of 66%. In contrast, A. tortilis showed significantly lower salt tolerance, with only 20% germination at the same concentration. A. saligna had the lowest salt tolerance, with germination only occurring under 150 mM NaCl concentration and with a FGP of only 18%. Based on these findings, the rank order of the studied species in terms of decreasing tolerance to high salinity conditions, as determined by their respective germination capacities, is as follows: A. karroo > A. tortilis > A. saligna. Although A. saligna was the most sensitive species, it was still categorized as a salt-tolerant glycophyte. Overall, this study provides valuable insights into the impact of salt stress on Acacia species and could contribute to the development of salt-tolerant crops in the future.