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Do mature leaves provide a net source of nitrogen supporting shoot growth in Rhododendron ferrugineum ?
Author(s) -
Pasche F.,
Por A.,
Lamaze T.
Publication year - 2002
Publication title -
new phytologist
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.742
H-Index - 244
eISSN - 1469-8137
pISSN - 0028-646X
DOI - 10.1046/j.1469-8137.2002.00370.x
Subject(s) - shoot , nitrogen , botany , biology , labelling , nitrogen cycle , horticulture , chemistry , biochemistry , organic chemistry
Summary• Nitrogen transfers in mature ( c . 40‐yr‐old) Rhododendron ferrugineum plants from mature leaves to growing shoots (Sh0) were estimated in the field at the branch scale. • Before bud break, the N pool of either 1‐yr‐old (L1) or 2‐yr‐old (L2) leaves of selected branches was labelled with 15 NH 4 Cl. The N dynamics were then investigated on three occasions during shoot growth. Mineral N uptake by roots was estimated by supplying seedlings with 15 NH 4 + or 15 NO 3 − (glasshouse) and mature plants with 15 NH 4 + (field). • Approximately 60% of the 15 N supplied was recovered in the labelled branches (40% in L1 leaves and 19% in Sh0) 78 d after L1 labelling. A similar pattern was observed for L2 labelling. Only traces of 15 N were detected in 1‐ and 2‐yr‐old‐stems. Although changes in the isotopic contents showed the occurrence of N transfer from mature leaves to the shoot, total L1 and L2 leaf N content was not modified. Simultaneously, exogenous 15 N uptake by the roots was very low. • We conclude that, despite the internal N cycling, mature leaves do not constitute a net source of nitrogen supporting shoot growth. The latter depends mainly upon endogenous nitrogen stored in woody stems and roots.