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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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Leaf expansion and chlorophyll fluorescence. (A) Dry masses of fully expanded leaves that occupied LPI positions +1, –1, and –3, denoted as pre(+1), pre(–1) and pre(–3), respectively, at the start of the 8 week experiment, and of expanding leaves that occupied LPI positions 2, 4, 5, 8, and 10 at the time of harvest. Data represent the means and SD of eight plants. (B) Quantum yield of PSII and variable fluorescence of expanding leaves. Data represent the means and SD of three plants for each LPI position, each derived from the mean of 36 instrument readings.
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fig1: Leaf expansion and chlorophyll fluorescence. (A) Dry masses of fully expanded leaves that occupied LPI positions +1, –1, and –3, denoted as pre(+1), pre(–1) and pre(–3), respectively, at the start of the 8 week experiment, and of expanding leaves that occupied LPI positions 2, 4, 5, 8, and 10 at the time of harvest. Data represent the means and SD of eight plants. (B) Quantum yield of PSII and variable fluorescence of expanding leaves. Data represent the means and SD of three plants for each LPI position, each derived from the mean of 36 instrument readings.

Mentions: During the 8 week monitoring period, shoot incremental height gain was larger in FG than SG (Table 1). Biomass of terminal shoot organs emerging during the monitoring period was greater in FG, primarily due to more rapid leaf growth. In general, leaf expansion was more rapid and of shorter duration in FG (Fig. 1A and Supplementary Table S1 available at JXB online). Photosynthetic chlorophyll fluorescence parameters were measured several times over a 9 d period to compare the development of photosynthetic competence in the clones (Fig. 1B and Supplementary Table S2). The increase in PSII quantum yield and variable fluorescence with leaf development was similar for both clones (Fig. 1B). Dry mass of lower stem internodes did not differ between clones (Table 1), although it is important to note that this was expected since lower stems of SG were 4–6 weeks older than those of FG. The stem biomass trends are consistent with the interpretation that, relative to SG, FG exhibited more rapid height growth in elongating internodes, and more rapid or more sustained radial growth in mature internodes. Root biomass and the root-to-shoot ratio calculated from averaged root and shoot biomass data were higher in FG than SG (Table 1).


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)

Leaf expansion and chlorophyll fluorescence. (A) Dry masses of fully expanded leaves that occupied LPI positions +1, –1, and –3, denoted as pre(+1), pre(–1) and pre(–3), respectively, at the start of the 8 week experiment, and of expanding leaves that occupied LPI positions 2, 4, 5, 8, and 10 at the time of harvest. Data represent the means and SD of eight plants. (B) Quantum yield of PSII and variable fluorescence of expanding leaves. Data represent the means and SD of three plants for each LPI position, each derived from the mean of 36 instrument readings.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

fig1: Leaf expansion and chlorophyll fluorescence. (A) Dry masses of fully expanded leaves that occupied LPI positions +1, –1, and –3, denoted as pre(+1), pre(–1) and pre(–3), respectively, at the start of the 8 week experiment, and of expanding leaves that occupied LPI positions 2, 4, 5, 8, and 10 at the time of harvest. Data represent the means and SD of eight plants. (B) Quantum yield of PSII and variable fluorescence of expanding leaves. Data represent the means and SD of three plants for each LPI position, each derived from the mean of 36 instrument readings.
Mentions: During the 8 week monitoring period, shoot incremental height gain was larger in FG than SG (Table 1). Biomass of terminal shoot organs emerging during the monitoring period was greater in FG, primarily due to more rapid leaf growth. In general, leaf expansion was more rapid and of shorter duration in FG (Fig. 1A and Supplementary Table S1 available at JXB online). Photosynthetic chlorophyll fluorescence parameters were measured several times over a 9 d period to compare the development of photosynthetic competence in the clones (Fig. 1B and Supplementary Table S2). The increase in PSII quantum yield and variable fluorescence with leaf development was similar for both clones (Fig. 1B). Dry mass of lower stem internodes did not differ between clones (Table 1), although it is important to note that this was expected since lower stems of SG were 4–6 weeks older than those of FG. The stem biomass trends are consistent with the interpretation that, relative to SG, FG exhibited more rapid height growth in elongating internodes, and more rapid or more sustained radial growth in mature internodes. Root biomass and the root-to-shoot ratio calculated from averaged root and shoot biomass data were higher in FG than SG (Table 1).

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