Nitrogen distribution in young Norway spruce (Picea abies) trees as affected by pedospheric nitrogen supply

Abstract

and Rennenberg, H, 1997, Nitrogen distribution in young Norway spmce (Picea abies) trees as affected by pedospheric nitrogen supply. -Physiol. Plant. 101: 764-769.In numerous locations in Europe spmce trees are exposed to high loads of nitrogen. The present study was performed to characterize the distribution of nitrogen compounds under these conditions. For this purpose Norway spruce (Picea abies [L.] Karst.) trees were cultivated under close-to-natural conditions of a forest understory in soil from an apparently nitrogen-limited field site in the Black Forest either with, or without supplementation of nitrogen as ammonium nitrate. After 11 and 20 months, growth, total nitrogen contents of the biomass, and total soluble non-proteinogenic nitrogen compounds (TSNN, i.e. nitrate, ammonium, soluble proteinogenic and nonproteinogenic amino compounds) in needles, xylem sap and phloem exudate were analysed. After 20 months of growth, N-fertilization had slightly enhanced the biomass of current-, but not of 1-year-old shoots. At both harvests, total N-content of 1year-old needles was increased by N-fertilization, whereas current-year needles were not significantly affected. By contrast, TSNN was elevated by N-fertilization in both current-year and 1-year-old needles. The increase in TSNN was mainly attributed to an accumulation of arginine. Xylem sap analysis showed that the increase in TSNN of the needles was a consequence of enhanced nitrogen assimilation of the roots rather than the shoot. Since also TSNN in phloem exudates was enhanced, it appears that Nfertilization elevates the cycling pool of amino compounds in young Norway spruce trees. However, this pool seems to be subject to metabolic interconversion, since mainly glutamine and aspartate are transported in the xylem from the roots to the shoot, but arginine accumulated in the needles and the phloem.

Metabolic responses of Norway spruce (Picea abies) trees to long‐term forest management practices and acute (NH4)2SO4 fertilization: transport of soluble non‐protein nitrogen compounds in xylem and phloem

“…In the xylem sap of spruce trees at Villingen, ammonium and nitrate were determined in trace amounts only, which is consistent with results of other studies (Dambrine et al, 1995 ;Stoermer et al, 1997 ;Geßler et al, 1998 b). The low ammonium and nitrate contents in the xylem sap indicate that the uptake of inorganic N by the roots might be well adapted to the roots' capacity for nitrate reduction and ammonium assimilation, supporting the idea that in spruce most of the inorganic N taken up from the soil is assimilated in the roots (Yandow & Klein, 1986).…”

Consequences of high loads of nitrogen for spruce (Picea abies) and beech (Fagus sylvatica) forests

“…If xylem and phloem transport constitute part of a cycling pool of organic N, metabolic interconversion of amino compounds is required in the roots and the needles in autumn, since in the xylem Gln and Asp are the main forms transported, whereas in the phloem Arg is predominant . Similar conclusions were drawn from experiments with young spruce trees exposed to different levels of N nutrition under controlled environmental conditions (Stoermer et al, 1997).…”

Absorption of Atmospheric NO2 by Spruce (Picea abies) Trees. III. Interaction with Nitrate Reductase Activity in the Needles and Phloem Transport

“…The present study indicates that the transient nature of induction of NR activity may be due to an export of products of NO z assimilation in the needles and the subsequent transport of these products in the stem. These products may include organic acids (mainly malate) that are produced concomitant with the reduction of nitrate (e.g, see review Touraine et aI., 1994), but also amino compounds (Arg, Gin, Asn, Asp, Glu and Ala) that constitute a cycling pool in spruce trees (Schneider et aI., 1996;Stoermer et al, 1997;GeBler et aI., 1998a). In particular, Gin has previously been shown to interact with NR activity in the shoots (see review Barneix and Causin, 1996) and nitrate uptake by the roots of spruce trees (GeBler et aI., 1998b).…”