Uncoupling Nitrogen Requirements for Spring Growth from Root Uptake in a Young Evergreen Shrub (Rhododendron ferrugineum)

• Internal cycling of nitrogen (N) was investigated in a subalpine field population of the evergreen shrub Rhododendron ferrugineum during spring growth. • The foliar nitrogen of 5-yr-old-plants was directly labeled with 15 N and subsequently traced to all plant compartments. In addition, 15 N-ammon...

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Veröffentlicht in:The New phytologist 2003-09, Vol.159 (3), p.637-644
Hauptverfasser: Lamaze, T., Pasche, F., Pornon, A.
Format: Artikel
Sprache:eng
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Zusammenfassung:• Internal cycling of nitrogen (N) was investigated in a subalpine field population of the evergreen shrub Rhododendron ferrugineum during spring growth. • The foliar nitrogen of 5-yr-old-plants was directly labeled with 15 N and subsequently traced to all plant compartments. In addition, 15 N-ammonium uptake was estimated in glasshouse experiments. • Before shoot growth, redistribution of 15 N occurred in the plant without net N transfer. During spring development, the decreases in both leaf 15 N and total N were almost identical in terms of percentage, and most of the 15 N withdrawn from the leaf compartments was recovered in the growing shoots. Net changes in the N contents of the various leaf and woody compartments indicate that internal remobilization (especially from 1-yr-old leaves) could have met most of the N needs of new shoot growth. Simultaneously, the rate of mineral N uptake was very low. • Thus, leaves in young plants provide N for new shoots (by contrast with old individuals) and allow, with woody tissues, almost complete uncoupling of N requirement for spring growth from root uptake.
ISSN:0028-646X
1469-8137
DOI:10.1046/j.1469-8137.2003.00830.x