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A comparative analysis of phenylpropanoid metabolism, N utilization, and carbon partitioning in fast- and slow-growing Populus hybrid clones.

Harding SA, Jarvie MM, Lindroth RL, Tsai CJ - J. Exp. Bot. (2009)

Bottom Line: Carbon partitioning within phenylpropanoid and carbohydrate networks in developing stems differed sharply between clones.The results did not support the idea that foliar production of phenylpropanoid defence chemicals was the primary cause of reduced plant growth in the slow-growing clone.The findings are discussed in the context of metabolic mechanism(s) which may contribute to reduced N delivery from roots to leaves, thereby compromising tree growth and promoting leaf phenolic accrual in the slow-growing clone.

View Article: PubMed Central - PubMed

Affiliation: School of Forestry and Natural Resources, University of Georgia, Athens, GA 30602, USA. sharding@uga.edu

ABSTRACT
The biosynthetic costs of phenylpropanoid-derived condensed tannins (CTs) and phenolic glycosides (PGs) are substantial. However, despite reports of negative correlations between leaf phenolic content and growth of Populus, it remains unclear whether or how foliar biosynthesis of CT/PG interferes with tree growth. A comparison was made of carbon partitioning and N content in developmentally staged leaves, stems, and roots of two closely related Populus hybrid genotypes. The genotypes were selected as two of the most phytochemically divergent from a series of seven previously analysed clones that exhibit a range of height growth rates and foliar amino acid, CT, and PG concentrations. The objective was to analyse the relationship between leaf phenolic content and plant growth, using whole-plant carbon partitioning and N distribution data from the two divergent clones. Total N as a percentage of tissue dry mass was comparatively low, and CT and PG accrual comparatively high in leaves of the slow-growing clone. Phenylpropanoid accrual and N content were comparatively high in stems of the slow-growing clone. Carbon partitioning within phenylpropanoid and carbohydrate networks in developing stems differed sharply between clones. The results did not support the idea that foliar production of phenylpropanoid defence chemicals was the primary cause of reduced plant growth in the slow-growing clone. The findings are discussed in the context of metabolic mechanism(s) which may contribute to reduced N delivery from roots to leaves, thereby compromising tree growth and promoting leaf phenolic accrual in the slow-growing clone.

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Lignin UV autofluorescence of primary–secondary transitional stem internodes. Shown are internode 3 from FG (A) and SG (B), and internode 6 from FG (C) and SG (D). Images were obtained from 75 μm vibratome sections using an excitation wavelength of 365 nm. Scale bar=500 μm. The arrow placed across the xylem is to facilitate a comparison of secondary xylem width which was wider in FG than in SG. pf, phloem fibre; xy, xylem.
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fig5: Lignin UV autofluorescence of primary–secondary transitional stem internodes. Shown are internode 3 from FG (A) and SG (B), and internode 6 from FG (C) and SG (D). Images were obtained from 75 μm vibratome sections using an excitation wavelength of 365 nm. Scale bar=500 μm. The arrow placed across the xylem is to facilitate a comparison of secondary xylem width which was wider in FG than in SG. pf, phloem fibre; xy, xylem.

Mentions: Lignin content reached a sustained maximum with respect to stem biomass much earlier in FG than in SG (Fig. 4A). A histological approach was used to compare lignification and vascular development of primary–secondary transitional internodes 3–6. UV autofluorescence of stem cross-sections revealed that fibre development and lignification were comparatively slow in xylem, but not phloem, of SG relative to FG (Fig. 5). The production of lignifying cells, based on the width of the autofluorescing zone in the xylem at both stages of internode growth, was more rapid in the FG clone (Fig. 5, arrows). Together, the Klason lignin and histological data were consistent with slowed xylem development relative to diameter growth of young internodes in SG. Lignin concentration increased between internode ∼10 and mid-stem internodes 20–25 in SG, but not FG (Fig. 4A).


A comparative analysis of phenylpropanoid metabolism, N utilization, and carbon partitioning in fast- and slow-growing Populus hybrid clones.

Harding SA, Jarvie MM, Lindroth RL, Tsai CJ - J. Exp. Bot. (2009)

Lignin UV autofluorescence of primary–secondary transitional stem internodes. Shown are internode 3 from FG (A) and SG (B), and internode 6 from FG (C) and SG (D). Images were obtained from 75 μm vibratome sections using an excitation wavelength of 365 nm. Scale bar=500 μm. The arrow placed across the xylem is to facilitate a comparison of secondary xylem width which was wider in FG than in SG. pf, phloem fibre; xy, xylem.
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC2724693&req=5

fig5: Lignin UV autofluorescence of primary–secondary transitional stem internodes. Shown are internode 3 from FG (A) and SG (B), and internode 6 from FG (C) and SG (D). Images were obtained from 75 μm vibratome sections using an excitation wavelength of 365 nm. Scale bar=500 μm. The arrow placed across the xylem is to facilitate a comparison of secondary xylem width which was wider in FG than in SG. pf, phloem fibre; xy, xylem.
Mentions: Lignin content reached a sustained maximum with respect to stem biomass much earlier in FG than in SG (Fig. 4A). A histological approach was used to compare lignification and vascular development of primary–secondary transitional internodes 3–6. UV autofluorescence of stem cross-sections revealed that fibre development and lignification were comparatively slow in xylem, but not phloem, of SG relative to FG (Fig. 5). The production of lignifying cells, based on the width of the autofluorescing zone in the xylem at both stages of internode growth, was more rapid in the FG clone (Fig. 5, arrows). Together, the Klason lignin and histological data were consistent with slowed xylem development relative to diameter growth of young internodes in SG. Lignin concentration increased between internode ∼10 and mid-stem internodes 20–25 in SG, but not FG (Fig. 4A).

Bottom Line: Carbon partitioning within phenylpropanoid and carbohydrate networks in developing stems differed sharply between clones.The results did not support the idea that foliar production of phenylpropanoid defence chemicals was the primary cause of reduced plant growth in the slow-growing clone.The findings are discussed in the context of metabolic mechanism(s) which may contribute to reduced N delivery from roots to leaves, thereby compromising tree growth and promoting leaf phenolic accrual in the slow-growing clone.

View Article: PubMed Central - PubMed

Affiliation: School of Forestry and Natural Resources, University of Georgia, Athens, GA 30602, USA. sharding@uga.edu

ABSTRACT
The biosynthetic costs of phenylpropanoid-derived condensed tannins (CTs) and phenolic glycosides (PGs) are substantial. However, despite reports of negative correlations between leaf phenolic content and growth of Populus, it remains unclear whether or how foliar biosynthesis of CT/PG interferes with tree growth. A comparison was made of carbon partitioning and N content in developmentally staged leaves, stems, and roots of two closely related Populus hybrid genotypes. The genotypes were selected as two of the most phytochemically divergent from a series of seven previously analysed clones that exhibit a range of height growth rates and foliar amino acid, CT, and PG concentrations. The objective was to analyse the relationship between leaf phenolic content and plant growth, using whole-plant carbon partitioning and N distribution data from the two divergent clones. Total N as a percentage of tissue dry mass was comparatively low, and CT and PG accrual comparatively high in leaves of the slow-growing clone. Phenylpropanoid accrual and N content were comparatively high in stems of the slow-growing clone. Carbon partitioning within phenylpropanoid and carbohydrate networks in developing stems differed sharply between clones. The results did not support the idea that foliar production of phenylpropanoid defence chemicals was the primary cause of reduced plant growth in the slow-growing clone. The findings are discussed in the context of metabolic mechanism(s) which may contribute to reduced N delivery from roots to leaves, thereby compromising tree growth and promoting leaf phenolic accrual in the slow-growing clone.

Show MeSH