ISHS Acta Horticulturae 383: Mineral Nutrition of Deciduous Fruit Plants
INTERNAL CYCLING OF NITROGEN IN TREES |
| Author: | P. Millard |
| Keywords: | Leaf senescence, nitrogen uptake, remobilisation, storage |
| Abstract:
The processes of internal cycling of nitrogen in trees are reviewed and discussed in relation to the management of fruit trees. In deciduous trees nitrogen is stored during the winter, predominantly as protein in the bark, and remobilised in the spring when the buds break. During the summer nitrogen is stored in the leaves and a proportion withdrawn during senescence. The use of isotopes has allowed quantification of these processes and so the contribution they make to the seasonal nitrogen economy of the trees. Remobilisation of nitrogen in spring provides nitrogen for leaf growth before rapid root uptake occurs and so is unaffected by the N supply to the soil. Fertilizing trees, therefore, will increase growth and storage capacity, but have little effect upon the efficiency of remobilization. However, applying fertilizers in the autumn can increase the partitioning of nitrogen to roots and can provide more for internal cycling than when taken up during the summer. Because of our better understanding of the internal cycling of nitrogen in forest trees, these results are discussed in relation to fruit and forestry species. | |
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