Impaired germination is common among halophyte seeds exposed to salt stress, partly resulting from the salt-induced reduction of the growth regulator contents in seeds. Thus, the understanding of hormonal regulation during the germination process is a main key: (i) to overcome the mechanisms by which NaCl-salinity inhibit germination; and (ii) to improve the germination of these species when challenged with NaCl. In the present investigation, the effects of ABA, GA 3 , NO − 3 , and NH + 4 on the germination of the oilseed halophyte Crithmum maritimum (Apiaceae) were assessed under NaCl-salinity (up to 200 mM NaCl). Seeds were collected from Tabarka rocky coasts (N-W of Tunisia). The exogenous application of GA 3 , nitrate (either as NaNO 3 or KNO 3 ), and NH 4 Cl enhanced germination under NaCl salinity. The beneficial impact of KNO 3 on germination upon seed exposure to NaCl salinity was rather due to NO − 3 than to K + , since KCl failed to significantly stimulate germination. Under optimal conditions for germination (0 mM NaCl), ABA inhibited germination over time in a dose dependent manner, but KNO 3 completely restored the germination parameters. Under NaCl salinity, the application of fluridone (FLU) an inhibitor of ABA biosynthesis, stimulated substantially seed germination. Taken together, our results point out that NO − 3 and GA 3 mitigate the NaCl-induced reduction of seed germination, and that NO − 3 counteracts the inhibitory effect of ABA on germination of C. maritimum.

Salinity and low nitrogen availability are important growth‐limiting factors for most plants. Our objective was to assess the influence of nitrogen (N) and salt levels on the growth and mineral nutrition of three forage grasses of varying salt resistance which are widely found in Tunisian salt lands, Aeluropus littoralis, Catapodium rigidum, and Brachypodium distachyum. Their response to salt and N interaction has not been studied and further investigations are necessary. Twenty day–old plantlets were hydroponically cultivated in Hewitt's nutrient solution. Half the plants were then exposed to 100 mM NaCl and the other half to no NaCl, and N was supplied at 0.5 or 5.0 mM N as NH4NO3. Plants were harvested after 60 d growth. Saline treatment (100 mM NaCl) decreased growth of B. distachyum (a relatively salt‐sensitive plant), but no significant effect was noted for A. littoralis (a relatively salt‐resistant plant) in both low– and high–N availability treatments. However, the effect of 100 mM NaCl on growth of C. rigidum (a moderately salt‐resistant plant) depended on N level. Increasing N availability and NaCl did not influence phosphate, sulfate, calcium, and magnesium concentrations in both A. littoralis and C. rigidum, but increased N supply reduced shoot sodium and chloride (Cl–) accumulation. Potassium acquisition in A. littoralis and C. rigidum plants was severely depressed by increasing N availability under saline and nonsaline conditions, respectively. In these species, the increase of nitrate accumulation via N was attenuated by salinity. In contrast, total N content and allocation toward shoots were enhanced in these conditions, especially in A. littoralis, the most resistant species. It appears that increasing N availability at moderate salt levels has a beneficial effect on growth of species with high and moderate salt resistance, but not on species with low resistance to salinity.

Despite seeds and fruits of several halophytes being rich in essential oils and other bioactive substances, the histochemical characterization of these compounds has not received much attention. The aims of the present investigation were to localize the essential oils and the bioactive substances in the seed coat of the oilseed halophyte Crithmum maritimum L. Fruits were collected from the rocky coasts of Tabarka (NW of Tunisia, 36°57′ 12″ N, 08°45′18″ E). C. maritimum L. seed is shown to be surrounded by two envelopes: The first structure is a secretory envelope, consisting in about 20 canals. The second layer represents the endocarp. As revealed by fluorescence and light microscopy, the essential oils, O-dihydroxyphenols and flavonoids, known as bioactive compounds, were accumulated in the canals. The endocarp layer accumulated polysaccharides, O-dihydroxyphenols, and flavonoids. As a whole, these findings highlight the histochemical features and confirm the valuable quality of C. maritimum L. seeds.

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