© 1986 Heron Publishing—Victoria, Canada
An effect of gravity on bud-burst in balsam fir
J. Worrall (1) and C. H. A. Little (2)
1. Faculty of Forestry, University of British Columbia, Vancouver, B.C., V6T 1W5, Canada / 2. Maritimes Forest Research Centre, Box 4000, Fredericton, New Brunswick, E3B 5P7, Canada / Received December 19, 1985
Summary
Bud-burst on first order lateral branches of Abies bafsamea L. (balsam fir) was delayed when the branches were rotated 180° about their long axis. This was not a consequence of injury
caused by the treatment because buds rotated 180° on inverted plants flushed at the same time as the controls,
whereas flushing of all other buds was delayed. Buds thus appear to be more vigorous when maintained in the same orientation
to gravity in which they are formed and the site of gravitational stimulus perception appears to be the bud itself.
Except on the leading shoot, leaves from inverted buds turned so that their adaxial surface faced upward, unless there was
intense illumination from below. However, both anisophylly and positioning of leaves on lateral shoots were apparently predetermined
because the shorter, more forward pointing leaves appeared below the longer distichous leaves on shoots from inverted buds.
Shoots with normally oriented leaves appeared the next season.
