Physiological and antioxidant responses of the sabkha biotope halophyte Limonium delicatulum to seasonal changes in environmental conditions.

In saline biotopes, different mechanisms may contribute to the tolerance of halophytes to high soil salinity and temperature, drought and other abiotic stresses, but their relative responses and their ecological plasticity for a given species remain unknown. In this study, we examined the responses of the salt marsh halophyte Limonium delicatulum to changing environmental conditions of its natural habitats (Sabkha "El Kalbia", Tunisia). The specific aim of the work was to check whether statistically significant correlations could be established between particular stress response mechanisms (ion uptake, activation of antioxidant systems) and soil parameters and climatic data associated with environmental stress. The results showed that the salinity of the soil increased during the months of June, July and August (dry period), concomitantly with a strong accumulation of salt ions in the aerial parts of the plant. Moreover, the highest antioxidant capacity of this halophyte (enzymes and antioxidant molecules) was reached during the same period of the year. The remaining periods (corresponding to the rainy season) did not show a significant difference in enzymes activities and level of antioxidants, with a minimum observed in the months of January and February. These results show a remarkable effect of salinity in the natural habitat on the activity of enzymes and antioxidant molecules. Other edaphic and climatic factors could also be involved to increase antioxidant capacity, such as nutrient deficiency, temperature and precipitation.