© 2005 Heron Publishing—Victoria, Canada
Righting response of artificially inclined maritime pine (Pinus pinaster) saplings to wind loading
Stephane Berthier (1, 2) and Alexia Stokes (1, 3)
1. Laboratoire de Rhéologie du Bois de Bordeaux, Mixed Unit: INRA/CNRS/Université Bordeaux I, Domaine de l’Hermitage, 69, rte
d’Arcachon, 33612 Cestas Cedex, France / 2. Forest Research, Northern Research Station, Roslin, Midlothian, EH25 9SY, U.K. / 3. Corresponding author (stokes@lrbb3.pierroton.inra.fr) / Received February 14, 2005; accepted May 3, 2005; published online October 3, 2005
Summary
To determine if trees respond to dynamic and static loading in the same manner, 2-year-old maritime pine (Pinus pinaster Ait.) trees were subjected to different types of mechanical loading in the field. One block of trees (the control) were kept
in pots and planted in the field at an angle of 0 or 45° to the vertical. A similar block of leaning potted trees was planted
nearby and subjected to frequent, unilateral wind loading for a period of 1 s every 2 min. Half the leaning trees were oriented
toward the direction of wind loading and half were oriented along the axis of wind loading. The stem profile was measured
three times during the growing season to quantify the rate of stem straightening. Compression wood formation and stem shape
were measured in all plants.
No differences in mean height or diameter were observed between blocks and all leaning trees straightened, but not at the
same rate. Although no difference in the rate of apical straightening occurred between control and wind-treated trees, the
righting response of the basal part of the stem of leaning trees subjected to wind was four times greater than that of leaning
trees without wind. No differences in the righting response were observed between leaning trees growing toward and trees growing
away from the source of wind. No significant differences in compression wood formation were found between control trees and
wind-treated trees, indicating that other factors must determine the reorientation rate of leaning trees. Results are discussed
with reference to the quality of compression wood in conifers and the mechanotransductive pathway in plants.
Keywords:
compression wood, mechanical stress, stem lean, thigmomorphogenesis.
