Carbon-based secondary metabolites and internal nitrogen pools in Populus nigra under Free Air CO2 Enrichment (FACE) and nitrogen fertilisation

Abstract

The goal of this study was to investigate whether increased nitrogen use efficiency found in Populus nigra L. (Jean Pourtet) under elevated CO 2 would correlate with changes in the production of carbon-based secondary compounds (CBSCs). Using Free-Air CO 2 Enrichment (FACE) technology, a poplar plantation was exposed to either ambient (about 370 µmol mol −1 CO 2 ) or elevated (about 550 µmol mol −1 CO 2 ) [CO 2 ] for 5 years. After three growing seasons, the plantation was coppiced and half of the experimental plots were fertilized with nitrogen. CBSCs, total nitrogen and lignin-bound nitrogen were quantified in secondary sprouts in seasons of active growth and dormancy during 2 years after coppicing. Neither elevated CO 2 nor nitrogen fertilisation alone or in combination influenced lignin concentrations in wood. Soluble phenolics and soluble proteins in wood decreased slightly in response to elevated CO 2 . Higher nitrogen supply stimulated formation of CBSCs and increased protein concentrations. Lignin-bound nitrogen in wood ranged from 0.37-1.01 mg N g −1 dry mass accounting for 17-26% of total nitrogen in wood, thus, forming a sizeable nitrogen fraction resistant to chemical degradation. The concentration of this nitrogen fraction was significantly decreased by elevated CO 2 , increased in response to nitrogen fertilisation and showed a significant CO 2 × fertilisation interaction. Seasonal changes markedly affected the internal nitrogen pools. Soluble proteins in wood were 52-143% higher in the dormant than in the growth season. Positive correlations existed between the biosynthesis of proteins and CBSCs. The limited responses to elevated CO 2 and nitrogen fertilisation indicate that Plant Soil (2008) 304:45-57 growth and defence are well orchestrated in P. nigra and that changes in the balance of both resourcesnitrogen and C-have only marginal effects on wood chemistry.

Will the CO2 fertilization effect in forests be offset by reduced tree longevity?

“…Gayler et al (2008) suggested that in nutrient-limited environments (such as in most terrestrial ecosystems), investment of carbon into defense is not favored, such that most of the extra carbon would be used for growth. Several CO 2 enhancement experiments confirmed this expectation for both deciduous (e.g., Luo et al 2008) and coniferous (e.g., Litvak et al 2002) trees, whereas Lavola and Julkunen-Tiitto (1994) found a slightly increased investment in defenses. Thus, it appears reasonable to assume that enhanced carbon supply via CO 2 fertilization would be invested mostly into enhanced growth rather than defense.…”

A Transcriptomic Network Underlies Microstructural and Physiological Responses to Cadmium in Populus × canescens

“…Soluble phenolics in samples were determined spectrophotometrically by using the Folin-Ciocalteu reagent as reported by Luo et al (2008). A standard curve was prepared using a series of diluted catechin solutions (Sigma).…”

Poplar Wood Rays Are Involved in Seasonal Remodeling of Tree Physiology

“…Since early wood has large vessels and thin cell walls, whereas late wood contains small vessels and thick cell walls , the amount of lignin required for incorporation increases toward autumn. Further increases in lignin occur in poplar wood after growth cessation (Luo et al, 2008) but not throughout winter (Bugos et al, 1991). The observed seasonal changes in PAL expression, therefore, trace these patterns in lignification.…”