Response of sclerophyllous and non-sclerophyllous plant species to saline aerosol

The tolerance to sea spray is an important parameter in the ornamental plant choice in the coastal landscaping. This tolerance is also the result of the characteristics of the structures that protect the leaf that are different among the species. In this frame, the aim of this study was to investigate the morphological and physiological mechanism adopted by two shrubs to overcome salt spray conditions. The two species analyzed were characterized by two types of leaves: Sclerophyllous (Laurus nobilis L.) and non-sclerophyllous (Plumbago auriculata Lam.). These two shrubs were subjected to twice a week-nebulization treatment with synthetic seawater solution for eight weeks. The following morphological parameters were monitored: Fresh and dry biomass of shoots and roots, leaf area and number, leaf damage (percentage of necrotic area), specific leaf area (SLA), and chlorophyll content. During the entire experimental period leaf gas exchange and chlorophyll a fluorescence were also monitored. Salt spray significantly decreased the epigeous dry biomass in Laurus at the end of the experimental period. Gas exchanges were influenced by stress conditions in both species, especially in Laurus, where a significant decrease (by 34%) at the end of the trial was found in aerosol plants compared to the control. Leaf damage increased with exposure to seawater aerosol and the greatest damage was found in Laurus (10%). In conclusion, between them, Plumbago was the ornamental shrub that retained better the ornamental quality even if the physiological processes were slowed down.