Morpho-anatomical, physiological and biochemical adjustments in response to root zone salinity stressand high solar radiation in two Mediterranean evergreen shrubs, Myrtus communis L. and Pistacia lentiscus L.

• Salt- and light-induced changes in morpho-anatomical, physiological and biochemical traits were analysed in Myrtus communis and Pistacia lentiscus with a view to explaining their ecological distribution in the Mediterranean basin. • In plants exposed to 20 or 100% solar radiation and supplied with 0 or 200 mM NaCl, measurements were conducted for ionic and water relations and photosynthetic performance, leaf morpho-anatomical and optical properties and tissuespecific accumulation of tannins and flavonoids. • Net carbon gain and photosystem II (PSII) efficiency decreased less in P. lentiscus than in M. communiswhen exposed to salinity stress, the former having a superiorability to use Na+ and Cl– for osmotic adjustment. Morpho-anatomical traits also allowed P. lentiscus to protect sensitive targets in the leaf from the combined action of salinity stress and high solar radiation to a greater degree than M. communis. Salt and light-induced increases in carbon allocated to polyphenols, particularly to flavonoids, were greater in M. communis than in P. lentiscus, and appeared to berelated to leaf oxidative damage. • Our data may conclusively explain the negligible distribution of M. communis in open Mediterranean areas suffering from salinity stress, and suggest a key antioxidant function of flavonoids in response to different stressful conditions.