AOBPreview originally published online on November 18, 2005
Annals of Botany 2006 97(1):3-10; doi:10.1093/aob/mcj009
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A Role for Shoot Protein in Shoot–Root Dry Matter Allocation in Higher Plants
1 School of Sciences, University of Sunderland, Sunderland SR1 3SD, UK, 2 University of Dundee at SCRI, Scottish Crop Research Institute, Invergowrie, Dundee DD2 5DA, UK, 3 Department of Biological Sciences, Lancaster University, Lancaster LA1 4YQ, UK and 4 Division of Environmental and Applied Biology, University of Dundee, Dundee DD1 4HN, UK
* For correspondence. E-mail mitchell.andrews{at}sunderland.ac.uk
Received: 2 July 2005 Returned for revision: 1 August 2005 Accepted: 29 September 2005 Published electronically: 18 November 2005
• Background and Aims It is stated in many recent publications that nitrate (
) acts as a signal to regulate dry matter partitioning between the shoot and root of higher plants. Here we challenge this hypothesis and present evidence for the viewpoint that and other environmental effects on the shoot : root dry weight ratio (S:R) of higher plants are often related mechanistically to changes in shoot protein concentration.
• Methods The literature on environmental effects on S:R is reviewed, focusing on relationships between S:R, growth and leaf and protein concentrations. A series of experiments carried out to test the proposal that S:R is dependent on shoot protein concentration is highlighted and new data are presented for tobacco (Nicotiana tabacum).
• Key Results/Evidence Results from the literature and new data for tobacco show that S:R and leaf concentration are not significantly correlated over a range of environmental conditions. A mechanism involving the relative availability of C and N substrates for growth in shoots can explain how shoot protein concentration can influence shoot growth and hence root growth and S:R. Generally, results in the literature are compatible with the hypothesis that macronutrients, water, irradiance and CO2 affect S:R through changes in shoot protein concentration. In detailed studies on several species, including tobacco, a linear regression model incorporating leaf soluble protein concentration and plant dry weight could explain the greater proportion of the variation in S:R within and between treatments over a wide range of conditions.
• Conclusions It is concluded that if can influence the S:R of higher plants, it does so only over a narrow range of conditions. Evidence is strong that environmental effects on S:R are often related mechanistically to their effects on shoot protein concentration.
Key words: Dry matter partitioning, nitrate signalling, nitrogen, protein, Nicotiana tabacum, tobacco, shoot : root ratio
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