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 increased 54-fold and the percentage of total plant Na+ found in the leaves increased from 9% to 63% with increasing external Na+. Calcium supplementation reduced the Na+ concentrations in leaves by up to 20%. Leaf Ca2+ concentrations increased with Ca2+ supplementation, but accounted for a decreasing percentage of the total Ca2+ found in the plant, since root Ca2+ concentrations were much higher. Root Nae concentrations increased with increasing Na+ treatments to a smaller extent than in the leaves and were also reduced by Ca2+ supplements. Potassium concentrations in leaves and roots decreased with increasing Na+ treatment levels, particularly in roots, where K+ concentration was about half at 100 mM Na+ (as Na2SO4.) Leaf Na+ concentrations were up to two times greater when Na+ was supplied as NaCl compared to Na2SO3. For plants salinized with NaCl, leaf Na+ levels increased to 1.1% and did not decrease when supplemental Ca2+ was applied. Leaf Cl- concentrations also increased 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 greater Ca2+, concentration in leaves and roots, but this did not alter Naf concentrations. Nutrient concentrations in 'Sharpblue' leaves, stems, and roots were greater than those of the rabbiteye cultivars, but were 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 mechanism to control Nac influx into blueberry leaves.