Journal Article

Plasticity in relative growth rate after a reduction in nitrogen availability is related to root morphological and physiological responses

Antonio Useche and Bill Shipley

in Annals of Botany

Published on behalf of The Annals of Botany Company

Volume 106, issue 4, pages 617-625
Published in print October 2010 | ISSN: 0305-7364
Published online July 2010 | e-ISSN: 1095-8290 | DOI: http://dx.doi.org/10.1093/aob/mcq144
Plasticity in relative growth rate after a reduction in nitrogen availability is related to root morphological and physiological responses

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

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Background and Aims

To maximize growth and fitness a plant must adjust its phenotype by an amount and speed that matches changes in nitrogen availability. To determine how plastic ontogenetic changes in root physiological and morphological traits interact and whether or not these responses are likely to maximize growth, ontogenetic changes in relative growth rate (RGR, proportional rate of change of plant dry mass), unit root rate (URR, rate of change of plant dry mass per unit root length or area), specific root length (SRL, root length per dry root mass), specific root area (SRA, root area per dry root mass), and other root traits before and after a decrease in nitrogen supply, were studied in ten herbaceous species.

Methods

Plants of each species were grown in hydroponic culture under controlled conditions in a control treatment where the supply of nitrogen remained constant at 1 mm, and in a stress treatment where the nitrogen supply was abruptly reduced from 1 to 0·01 mm during the growth period.

Key Results and Conclusions

In the treatment series the number of bifurcations per root area and per root length, specific root area (SRA) and length (SRL), areal (URRarea) and length-based (URRmass) unit root rate and RGR decreased, and root tissue density increased relative to the control. Species having greater plasticity in the percentage decrease in SRA at the end of the experiment also had smaller reductions in RGR; plasticity in SRA is therefore adaptive. In contrast, species which showed a greater reduction in URRarea and in the number of bifurcations per root area and per root length, showed stronger reductions in RGR; plasticity in URRarea and in the number of bifurcations per root area and per root length is therefore not adaptive. The plastic responses observed in SRA, SRL and in root tissue density constitute a set of plastic adjustments that would lead to resource conservation in response nutrient stress.

Keywords: Nutrient stress; ontogenetic plasticity; root traits; RGR; root physiology; root morphology

Journal Article.  6830 words.  Illustrated.

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

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