In the saline depressions (Sebkhas) of Tunisia, Sulla carnosa expresses anarchic distribution, sometimes in association with halophytes sometimes individually. In order to explain this distribution, we investigated the effects of salinity on seed germination, the osmotic and toxic limiting factors, and the importance of some stimulating agents (priming agents) in the improvement of the tolerance to salinity at the germinating stage. A study was conducted on seeds harvested from the natural biotope Sebkha d'El Kelbia (35°50'34″N, 10°16'18″E), and an increasing concentration of NaCl (0, 5, 10, 15, and 20 g L-1) was applied. Some priming agents were used to propose efficient, rapid, and low-cost tools to improve the seed germination and tolerance of Sulla carnosa (Desf.) in saline depression. Salinity stress significantly decreased germination capacity and rate and delayed its initiation and maximum. Until 15-g L-1 NaCl, the most limiting factor of seed germination is the osmotic effect. At 20-g L-1 NaCl, the toxic effect dominates, and germination is irreversibly inhibited. Some priming agents have shown their efficiency in improving the germination capacity at 10-g L-1 NaCl and conferring a salt tolerance of up to 15-g L-1 NaCl.
Keywords: Sulla carnosa; germination; osmotic effect; priming; salinity; toxic effect.
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