Spring mobilization of storage 32P in apple trees

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 32P determined in the following early growing season. 32P 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 32P was found in storage tissues (bark, wood, scion buds) although the accumulation of 32P occurred especially in root tissues. During early growing season, 32P was transported from storage tissues to new growing tissues. During this period, the 32P in the scion shoot tissues increased about 348 fold. (author)