Effect of seawater aerosol on leaves of six plant species potentially useful for ornamental purposes in coastal areas

Aerosol marine strongly affects the growth and development of urban, garden and landscape plants. Few studies have focused on the effects of sodium chloride on plant growth, which is usually applied through irrigation water or substrate media. Even less information is available on the eco-physiological responses of plants to marine aerosol. The aim of this work was to evaluate the physiological responses of different plant species to seawater nebulisation treatments. Plant species that are commonly used along sea fronts were selected as being potentially useful for the study. Plants were bought from a local nursery and included: Acacia cultriformis, Callistemon citrinus, Carissa edulis microphylla, Gaura lindheimeri, Jasminum sambac, Westringia fruticosa. Plants were placed in a randomised block design in a greenhouse and treated for 5 s with seawater or irrigation water (control) using a nebulisation system once every day for 77 days.In the seawater aerosol-treated plants, the following parameters were monitored: leaf area damage using an image analysis tool, chlorophyll a fluorescence, hormonal changes and cation concentrations. We found that seawater aerosol treatment leads to: (i) leaf necrosis; (ii) chlorophyll loss; and (iii) a decrease in chlorophyll a fluorescence. The ion exclusion mechanism might have played a key role in the tolerance mechanism. Ethylene production increased in all species as a good biomarker and the strong increase in ABA content in the sensitive species may play a role in the plant's adaptation to stress.The chlorophyll a fluorescence parameters such as Fv/Fm and the performance index were the most affected by treatment and led to a screening sensitive (A. cultriformis and G. lindheimeri) and tolerant (W. fruticosa) species.

Research highlights
► Marine aerosol strongly affects the photochemistry of photosystem II.
► Ethylene production and ABA accumulation are related with salt tolerance.
► Chlorophyll a fluorescence and derived parameters seems to be a good marker for screening plants against sea water aerosol tolerance.