EFFECT OF GROWTH REGULATORS, CULITVARS AND ROOTSTOCKS OF APPLE ON RADIOCALCIUM UPTAKE

Spartan and Harrold Red Delicious apple trees on M26, M7, MM106 and MM111 rootstocks were grown in silica sand and then in continuously aerated containers holding 2500 ml of Long Ashton full nutrient solution. The experiment commenced when the trees were placed into the aerated nutrient solution and headed back to 3 basal leaves. Duplicate containers received 23 and 46 μCi of ⁴⁵Ca for each cultivar/rootstock combination. One day later the 3 axillary buds on one half of the trees were painted with a mixture of 0.2% benzyladenine (BA), 5% dimethylsulfoxide and 1% Tween 20. On each of the 2 following days each axillary bud received a few drops of 500 ppm gibberellic acid (GA₃). After 21 days of tree growth in the solutions containing ⁴⁵Ca the following samples were analyzed by scintillation counting: a) root bark; b) low stem bark (below the graft); c) high stem bark (above the graft); d) old leaves; and e) new shoot growth.