MINERAL-COMPOSITION OF YOUNG RABBITEYE AND SOUTHERN HIGHBUSH BLUEBERRY EXPOSED TO SALINITY AND SUPPLEMENTAL CALCIUM

'Tifblue' and 'Brightwell' rabbiteye blueberry (Vaccinium ashei Reade) and 'Sharpblue' southern highbush blueberry (primarily V. corymbosum) were treated with 0, 25, and 100 mM Na+ as Na,SO, or NaCl, and 0, 1, 3, and 10 mM supplemental Ca2+ in sand culture in the greenhouse. For rabbiteye plants salinized with Na,SO,, leaf Na+ concentrations increa sed 54-fold and the percentage of total plant Na+ found in the leaves increased from 9% to 63% with increasing external Na+. Calcium supplem entation reduced the Na+ concentrations in leaves by up to 20%. Leaf C a2+ concentrations increased with Ca2+ supplementation, but accounted for a decreasing percentage of the total Ca2+ found in the plant, sinc e root Ca2+ concentrations were much higher. Root Nae concentrations i ncreased with increasing Na+ treatments to a smaller extent than in th e leaves and were also reduced by Ca2+ supplements. Potassium concentr ations in leaves and roots decreased with increasing Na+ treatment lev els, particularly in roots, where K+ concentration was about half at 1 00 mM Na+ (as Na2SO4.) Leaf Na+ concentrations were up to two times gr eater when Na+ was supplied as NaCl compared to Na2SO3. For plants sal inized with NaCl, leaf Na+ levels increased to 1.1% and did not decrea se when supplemental Ca2+ was applied. Leaf Cl- concentrations also in creased greatly with NaCl, reaching >1.0% (dry weight basis.). Root Cl (-)concentrations also increased with increasing salinity and were not affected by Ca2+ supplements. Ca2+ supplementation led only to a grea ter Ca2+, concentration in leaves and roots, but this did not alter Na f concentrations. Nutrient concentrations in 'Sharpblue' leaves, stems , and roots were greater than those of the rabbiteye cultivars, but we re influenced by salinity and Ca2+ in essentially the same way. Excess Na+, Cl-; or both, together with lowered K+, were likely the cause of extensive leaf necrosis and may be indicative of a lack of a mechanis m to control Nac influx into blueberry leaves.