Journal Article

Correlated responses of root growth and sugar concentrations to various defoliation treatments and rhythmic shoot growth in oak tree seedlings (<i>Quercus pubescens</i>)

Magali Willaume and Loïc Pagès

in Annals of Botany

Published on behalf of The Annals of Botany Company

Volume 107, issue 4, pages 653-662
Published in print April 2011 | ISSN: 0305-7364
Published online January 2011 | e-ISSN: 1095-8290 | DOI: http://dx.doi.org/10.1093/aob/mcq270
Correlated responses of root growth and sugar concentrations to various defoliation treatments and rhythmic shoot growth in oak tree seedlings (Quercus pubescens)

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  • Ecology and Conservation
  • Evolutionary Biology
  • Plant Sciences and Forestry

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Background and Aims

To understand whether root responses to aerial rhythmic growth and contrasted defoliation treatments can be interpreted under the common frame of carbohydrate availability; root growth was studied in parallel with carbohydrate concentrations in different parts of the root system on oak tree seedlings.

Methods

Quercus pubescens seedlings were submitted to selective defoliation (removal of mature leaves, cotyledons or young developing leaves) at appearance of the second flush and collected 1, 5 or 10 d later for morphological and biochemical measurements. Soluble sugar and starch concentrations were measured in cotyledons and apical and basal root parts.

Key Results

Soluble sugar concentration in the root apices diminished during the expansion of the second aerial flush and increased after the end of aerial growth in control seedlings. Starch concentration in cotyledons regularly decreased. Continuous removal of young leaves did not alter either root growth or apical sugar concentration. Starch storage in basal root segments was increased. After removal of mature leaves (and cotyledons), root growth strongly decreased. Soluble sugar concentration in the root apices drastically decreased and starch reserves in the root basal segments were emptied 5 d after defoliation, illustrating a considerable shortage in carbohydrates. Soluble sugar concentrations recovered 10 d after defoliation, after the end of aerial growth, suggesting a recirculation of sugar. No supplementary recourse to starch in cotyledons was observed.

Conclusions

The parallel between apical sugar concentration and root growth patterns, and the correlations between hexose concentration in root apices and their growth rate, support the hypothesis that the response of root growth to aerial periodic growth and defoliation treatments is largely controlled by carbohydrate availability.

Keywords: Apex; carbohydrate; defoliation; hexose; organ removal; Quercus pubescens; rhythmic growth; root growth; starch

Journal Article.  6442 words.  Illustrated.

Subjects: Ecology and Conservation ; Evolutionary Biology ; Plant Sciences and Forestry

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