Seed germination of two wheat species differing in their sensitivity to NaCl, in response to salt stress

\The germination of two wheat species, Triticum aestivum var. Tanit and Triticum durum var. Ben Bechir, respectively, sensitive and tolerant to salt stress, were studied. In the presence of NaCl in the external medium, the tissue content of W was increased much more than that of Cl-. Proline concentration was increased, and the overall peroxidase activity was decreased. These effects were more pronounced in the salt-sensitive than in the salt tolerant species, and they became apparent in the few hours following the beginning of germination. The PEPC activity was slightly decreased in the salt-sensitive species while it was slightly increased in the salt-tolerant species. Modelling the time course of seed germination and leaf sprouting with a sigmoidal equation, made it possible to distinguish the effect of-NaCl on the three main parameters characteristic of the time courses of germination and of the sprouting of the first leaf: tau (the time lag before germination/leaf sprouting appreciably began), R (the rate of increase of the percentage of germination/leaf sprouting), and M (the maximal value of this percentage). The presence of external NaCl caused M and R to decrease and tau to increase. Again, the effect was more pronounced in the salt-sensitive than in the salt-tolerant species.