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This experiment was carried out to study the effects of foliar sprays of some growth regulators, NAA (20 ㎎ 1^(-1)), paclobutrazol(50 ㎎ 1^(-1)) and daminozide (2,500 ㎎ 1^(-1)), on ^(45)Ca mobility and 4 fractionated calcium concentrations in 11 week-old `Fuji´ apple seedlings (Malus domstica Borkh.) grown under two different calcium conditions, 2 and 200㎎ 1^(-1), for 4 weeks. At 3 weeks after foliar spray treatments, leaf Ca concentrations of the trees in all growth regulator treatments were significantly higher than that in the unsprayed trees, regardless of calcium conditions in the nutrient solution. No differences were noted in leaf Ca concentrations of the trees grown under high Ca level among growth regulator treatments, but the leaf Ca concentrations of the trees grown under low Ca level showed a higher tendency in the order of paclobutrazol, daminozide and NAA. Leaf Ca concentration of -the trees supplied with low Ca level was significantly lower than that of the trees supplied with high Ca level in the same growth regulator treatments. Of the total Ca, distributions of Ca extracted with water-soluble and sodium nitrate-exchangeable Ca, physiologically active forms, were higher in the trees sprayed with NAA than in the trees sprayed with other growth regulator treatments. The tendency was more clear in the trees grown under low Ca level than in the trees grown under high Ca level. No differences were observed in uptake and traslocation of root-applied ^(45)Ca at the time of foliar spray treatments between the growth regulator sprayed trees and the unsprayed trees. In all treatments of foliar spray with growth regulators, accumulation of ^(45)Ca was higher in stem and root parts of the trees grown under low Ca level than those grown under high Ca level. The facts suggest that foliar sprays of paclobutrazol, daminozide and NAA may enhance retranslocation of previously deposited Ca in the young apple seedlings, but may exert no influence on uptake and translocation of root-supplied Ca at the time of foliar spray treatments. And the facts reconfirm that Ca mobility in the apple tree may be changed according to the Ca-nutritional status.
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