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Keywords:

  • flavonoid glycosides;
  • fluorescence spectroscopy;
  • gas exchange and photosynthetic performance;
  • hydrolysable tannins;
  • ionic and water relations;
  • leaf morpho-anatomy and leaf optics;
  • lipid peroxidation

Summary

  • • 
    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 tissue-specific accumulation of tannins and flavonoids.
  • • 
    Net carbon gain and photosystem II (PSII) efficiency decreased less in P. lentiscus than in M. communis when exposed to salinity stress, the former having a superior ability 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 be related 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.