The labelled phosphorus was supplied to the roots of 1-year-old apple trees during dormant period in the green house and the mobilization of stored ^(32)P determined in the following early growing season, ^(32)P was detected in all new root and shoot growth, the level of radioactivity being greatest in the root tissues over the 5-week sampling period. At dormant period, only 2.5% of ^(32)P was found in storage tissues (bark, wood, scion buds) although the accumulation of ^(32)P occurred especially in root tissues. During early growing season, ^(32)P was transported from storage tissues to new growing tissues (new root and scion shoot) Six percent of the initial ^(32)P in storage tissues was transported to new growing tissues. During this period, the ^(32)P in the scion shoot tissues increased about 348 fold.
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