Optimal salt treatment alleviates detrimental effects of severe nutrient deficiencies in Sesuvium portulacastrum

Psammophilic halophytes are subjected in their natural habitats to the interactive effects of salinity and nutrient deficiencies. The aim of the present investigation was to check whether an optimal salt treatment enhances growth and antioxidant responses of the psammophilic obligate halophyte Sesuvium portulacastrum L. Seedlings were grown for 6 weeks on a nutrient medium (C), diluted 50 times (D), or diluted 50 times and added with 200 mM NaCl (DS). Nutrient deficiencies drastically reduced biomass production in both shoots and roots but did not induce a marked oxidative stress as shown by the ‘non-toxic’ levels of hydrogen peroxide (H2O2) and malondialdehyde (MDA). In roots, a marked decrease in catalase (CAT) activity seems to keep a certain level of H2O2 for stress signalling purposes. The detrimental effect on growth was slightly alleviated by the optimal salt concentration in DS treatment. H2O2 and MDA concentrations were higher in DS treatment than in D treatment, but they remained at ‘nontoxic’ levels. The responses of antioxidant enzymes showed the same trend in D and DS treatments but with different magnitudes. Taken together, these results showed that the beneficial effect of salinity on the responses of this psammophilic obligate halophyte to other stresses (i) is limited by the severity of those stresses and (ii) is not mainly based on antioxidant responses.