Identification of ornamental shrubs tolerant to saline aerosol for coastal urban and peri-urban greening

tSalt spray can be an important abiotic stress that strongly influences plant survival and species distribu-tion. Much of the research conducted on salinity tolerance concerns saline soil or saline irrigation, butlittle research focuses on plant exposure to salt spray in the absence of saline irrigation conditions. Theaim of this study was to investigate the effects of seawater aerosol on fifteen ornamental shrubs diffusein the Mediterranean environment. Plants of the fifteen ornamental shrubs were subjected to twice aweek nebulisation treatments with synthetic seawater solution for eight weeks. Among the 15 speciesstudied, four were selected as models, one as a sensitive species (Viburnum tinus), two as intermediatespecies (Murraya paniculata and Polygala myrtifolia), and one as a tolerant species (Raphiolepis umbellata).The following morphological parameters were monitored: the fresh and dry weight of shoots and roots,leaf area, leaf number, leaf damage, specific leaf area (SLA), chlorophyll content and ion content. The rel-ative water content (RWC), leaf gas exchange and chlorophyll a fluorescence were monitored during theentire experimental period. The species exposed to the seawater solution showed different physiologicaland morphological responses. The treatment led to a decrease of biomass, leaf area and number in M.paniculata. The gas exchanges were affected by the stress conditions, indicating the defence mechanismactivated against the salt stress. The leaf damage increased with the exposure to the seawater aerosoland the greatest damage was found in V. tinus. In P. myrtifolia, a decrease in the chlorophyll a fluorescencewas observed. The salt spray treatments enhanced the correlation between chlorophyll a fluorescenceand WUE.