AOBPreview originally published online on April 29, 2008
Annals of Botany 2008 101(9):1421-1432; doi:10.1093/aob/mcn054
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Mechanical Stimuli Regulate the Allocation of Biomass in Trees: Demonstration with Young Prunus avium Trees
1 INRA, UMR PIAF- Université Blaise Pascal, 234 avenue du Brézet, 63100 Clermont-Ferrand, France
2 INRA, UMR SYSTEM, Equipe d'Agroforesterie, Bâtiment 27, 2, Place Viala, 34060 Montpellier Cedex 1, France
* For correspondence. E-mail coutand{at}clermont.inra.fr
Received: 24 January 2008 Returned for revision: 25 February 2008 Accepted: 18 March 2008 Published electronically: 1 May 2008
Background and Aims: Plastic tree-shelters are increasingly used to protect tree seedlings against browsing animals and herbicide drifts. The biomass allocation in young seedlings of deciduous trees is highly disturbed by common plastic tree-shelters, resulting in poor root systems and reduced diameter growth of the trunk. The shelters have been improved by creating chimney-effect ventilation with holes drilled at the bottom, resulting in stimulated trunk diameter growth, but the root deficit has remained unchanged. An experiment was set up to elucidate the mechanisms behind the poor root growth of sheltered Prunus avium trees.
Methods: Tree seedlings were grown either in natural windy conditions or in tree-shelters. Mechanical wind stimuli were suppressed in ten unsheltered trees by staking. Mechanical stimuli (bending) of the stem were applied in ten sheltered trees using an original mechanical device.
Key Results: Sheltered trees suffered from poor root growth, but sheltered bent trees largely recovered, showing that mechano-sensing is an important mechanism governing C allocation and the shoot–root balance. The use of a few artificial mechanical stimuli increased the biomass allocation towards the roots, as did natural wind sway. It was demonstrated that there was an acclimation of plants to the imposed strain.
Conclusions: This study suggests that if mechanical stimuli are used to control plant growth, they should be applied at low frequency in order to be most effective. The impact on the functional equilibrium hypothesis that is used in many tree growth models is discussed. The consequence of the lack of mechanical stimuli should be incorporated in tree growth models when applied to environments protected from the wind (e.g. greenhouses, dense forests).
Key words: Prunus avium, growth, mechanical stress, bending, biomass, shoot/root ratio, wind, shelter