Effects of leaf nitrogen availability and leaf position on nitrogen allocation patterns in Vaccinium vitis-idaea and...

Nitrogen allocation patterns from leaves of Vaccinium vitis-idaea (evergreen) and Vaccinium uliginosum (deciduous) were assessed using a foliar application of ¹⁵N labeled ammonium sulfate. These are wild perennial shrubs inhabiting arctic and subarctic regions. More label was transported from labeled leaves of Vaccinium uliginosum then Vaccinium vitis-idaea. In Vaccinium uliginosum, the amount of label transported from the labeled leaf increased as the concentration of nitrogen in the label increased. Current growth in Vaccinium uliginosum was a strong sink for nitrogen because most of the ¹⁵N transported from the labeled leaf was contained in this region. In addition, when greater quantities of nitrogen were applied, larger quantities were retained in current growth. Current growth of Vaccinium vitis-idaea, on the other hand, was not as strong a sink because regardless of the nitrogen available thru various label concentrations, the enrichment of current growth was not affected and was not significantly different from older stems or leaves. Yet, in both species, nitrogen was transported freely from leaves of all positions along the stem to all parts of the plant including roots and rhizomes. The position of the leaf along the stem had no effect on the patterns of allocation to other organs.