Calcium increases sodium exclusion in olive plants

'Picual' olive cuttings were grown in a greenhouse under saline conditions in 2 L plastic pots containing perlite. Plants were irrigated with a nutrient solution plus 75 mM NaCl and 0, 2.5. 10 or 40 mM CaCl2. Vegetative growth, leaf and root Na+ and Ca2+ concentrations were measured. Na+ toxicity symptoms were observed in plants non-treated with Ca2+. Shoot length was higher in Ca2+ treated plants. although shoot growth was reduced at 40 mM CaCl2, probably due to the high total ion concentration reached in the external solution. Ca2+ supply linearly increased leaf and root Ca2+ concentration and decreased leaf Na+ concentration. However. there were no differences in root Na+ concentration. Results indicate Ca2+ may take part in the Na+ exclusion mechanism, mainly preventing Na+ transport to the shoot. that may be an important ability for survival under saline conditions. (c) 2006 Elsevier B.V. All rights reserved.