The deposition of calcium in tomato fruit grown at a range of salinities (electrical conductivities between 3 and 17 mS cm-1), with or without IAA-transport inhibitor treatment, was investigated. Calcium (Ca) in the flesh and pulp of tomato fruit was sequentially separated into four fractions: FI soluble in water, FII soluble in 2.5 mol dm-3 NaCl, FIII soluble in 2% acetic acid and FIV soluble in 5% HCl. In mature fruit, grown at 3 mS cm-1, more than half the Ca was in FI, and the Ca concentration was higher in the pulp than in the flesh. FII and FIII each contained less than 20% of the Ca, and the Ca concentration was higher in the flesh than in the pulp. In general, salinity reduced the concentration of Ca in all fractions and slightly altered the proportional distribution of Ca in fractions. The deposition of calcium in young fruit, grown at 3 and 8 mS cm-1, was highest in FII in the flesh or in FI in the pulp. When Ca-45 was supplied to detached fruit, the patterns of Ca-45 distribution in the fractions were similar to that of total Ca. Treatment with an IAA-transport inhibitor, CME, reduced both the uptake and transport of Ca-45. While the amount of Ca-45 in all fractions was significantly reduced by CME, the proportional distribution of Ca-45 among fractions was not affected substantially. Although the proportional deposition of Ca in different fractions was not significantly affected by either salinity or CME, further reduction of the intrinsically low deposition of Ca in FII of distal pulp caused by these factors may be the cause of blossom-end rot in tomato fruit.
