Multidisciplinary studies supporting conservation programmes of two rare, endangered Limonium species from Spain

Two local threatened endemics from Valencian salt marshes were analysed from a multidisciplinary perspective combining field studies with experiments performed under greenhouse-controlled conditions. The work aimed to investigate the habitat of the two species but also to explore their limits of tolerance to severe drought and salinity and the mechanisms behind their stress responses. The number of individuals in several populations, climatic conditions, soil characteristics and accompanying vegetation in the natural habitats were analysed in the field study. Plants obtained by seed germination were grown in the greenhouse and subjected to one month of water and salt stress treatments. Growth and biochemical parameters were analysed after the treatments were finalised. No correlation between climatic parameters and the number of individuals censed of the two Limonium species could be established. Although L. dufourii was found in more saline soils in the natural habitats, under controlled greenhouse conditions, this species was more severely affected by salt treatment than L. albuferae, which is more susceptible to water stress. A common biochemical response was the increase of proline under all stress treatments, but mostly in water-stressed plants. Oxidative stress markers, MDA and H2O2, did not indicate significant differences between the treatments. The differences in the two species' responses to the two kinds of stress were correlated with the activation of the antioxidant enzymes, more pronounced in conditions of salt stress in L. albuferae and of water stress in L. dufourii. Although L. albuferae is found in sites with lower salinity in the natural habitats, the greenhouse experiment indicated that it tolerates higher concentrations of salt than L. dufouri, which is more resistant to drought. The two species efficiently mitigate oxidative stress by activation of antioxidant enzymes. The results obtained may be helpful for the conservation management of the two species: whereas salinity is not problematic, as the two species tolerated under controlled conditions salinities far beyond those in their natural environments, water scarcity may be a problem for L. albuferae, which proved to be more susceptible to water deficit.