Nitrogen forms in bark, wood and foliage of nitrogen-fertilized Pinus sylvestris

Abstract

Cycling of soluble non-protein N compounds is thought to be indicative of the N-nutritional status of trees. We determined the major N forms in bark, wood and foliage and estimated the dependence of prevalent N forms on N availability in Pinus sylvestris L. trees from northern Sweden. Trees subjected to severe N limitation and trees that had been fertilized with an average 64 kg N ha(-1) year(-1) for 25 years were analyzed. Bark and wood samples were collected by tangentially cryo-sectioning the trunk into 30-microm thick sections, from the bark to the functional xylem. Soluble amino compounds were extracted from the sections for analysis. Sap samples from twigs were obtained by centrifugation, and bark samples from twigs were obtained by tissue extraction. In both needles and bark, arginine dominated the amino-N pool. Because arginine concentrations in needles increased with N fertilization, arginine dominance of the amino-N pool in needles was higher in N-fertilized trees than in control trees. In bark, N fertilization resulted in a large increase in glutamine concentration, so that glutamine accounted for a larger proportion of the amino-N pool in bark in N-fertilized trees than in control trees. Glutamine dominated the amino-N pool in wood of control trees. Nitrogen fertilization resulted in an increased proportion of arginine in the wood amino-N pool. We conclude that the composition of the amino-N pools in bark, wood and foliage is highly sensitive to N supply. The composition of the amino-N pools can contribute to the regulation of tree N-nutritional status, which is mediated by shoot to root signalling by long-distance transport of amino compounds.

Changes of carbon and nitrogen metabolites in white spruce (Picea glauca [Moench] Voss) of contrasted growth phenotypes

“…These results support the occurrence of a transition in nitrogen metabolism in the small spruces when photoperiod neared 14 h. Glutamine is a key amino acid involved in nitrogen assimilation in plants (Forde and Lea 2007), and because of its uncharged properties, it has been hypothesized to be an efficient form of nitrogen transport in Scots pine (Gezelius 1986;Nordin et al 2001). Recent reviews on nitrogen assimilation in woody plants stressed the importance of glutamine as a precursor of tyrosine and phenylalanine, which are involved in the phenylpropanoid pathway leading to the biosynthesis of lignin (Gallardo et al 2003;Suárez et al 2002).…”

“…Arginine was by far the most important nitrogen component in white spruce organs. It is a major form of nitrogen storage in many tree species, including Scots pine (Gezelius 1986;Nordin et al 2001), loblolly pine (Pinus taeda L.) (King and Gifford 1997), black spruce (Bertrand and Bigras 2006;Kim et al 1987), Norway spruce (Manderscheid and Jäger 1993) and deciduous sycamore (Acer pseudoplatanus L.) (Millard and Proe 1991). Durzan (1968) previously reported a peak of arginine in buds and needles of white spruce during growth cessation and bud set period.…”

“…Amino acids such as asparagine, glutamine, arginine and proline, as well as specific soluble proteins harboring characteristics of vegetative storage proteins accumulate during the over wintering period and are readily mobilized during spring regrowth in herbaceaous perennials (Dhont et al 2006). Together with glutamine, arginine was found to be the major storage form of non proteinous nitrogen in bilberry (Vaccinillum myrtillus) rhizome (Lähdesmäki et al 1990) and in needles of Scots pine (Gezelius 1986;Nordin et al 2001). Durzan (1968) also documented that arginine was a major storage form of nitrogen in white spruce needles and buds.…”

Chemical composition and bioavailability of thermally altered Pinus resinosa (Red pine) wood

“…The 18:2 fatty acid accounted for 41% of the total fatty acids, whilst the 18:1 and 18:3 fatty acids each accounted for approximately 23%, suggesting that, on average, the lipid fraction could be represented by linoleic acid, an 18:2 fatty acid. The theoretical ratios for protein were derived from amino acid distributions measured in wood collected from fertilised Pinus sylvestris trees (Nordin et al, 2001). The unheated Pinus resinosa sapwood used in this study and the unheated wood used by Shafizadeh (1984) fall within the bounds of possible wood composition, close to the theoretical composition of carbohydrate and the line linking carbohydrate to lignin.…”

Wood production, wood technology, and biotechnological impacts

“…6 and not shown). Since conifer wood is generally low in nitrogen (Hattenschwiler et al 1996, Nordin et al 2001, Payne 2002, Kostianinen et al 2004, positive effects on growth are seen upon addition of nutrients to PSF-Wood (Fig. 6A).…”