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The biomechanics of Cornus canadensis stamens are ideal for catapulting pollen vertically

  1. D. L. WHITAKER1,*,
  2. L. A. WEBSTER2,
  3. J. EDWARDS3

Article first published online: 7 FEB 2007

DOI: 10.1111/j.1365-2435.2007.01249.x

Issue

Functional Ecology

Functional Ecology

Volume 21, Issue 2, pages 219–225, April 2007

Additional Information

How to Cite

WHITAKER, D. L., WEBSTER, L. A. and EDWARDS, J. (2007), The biomechanics of Cornus canadensis stamens are ideal for catapulting pollen vertically. Functional Ecology, 21: 219–225. doi: 10.1111/j.1365-2435.2007.01249.x

Author Information

  1. 1

    Physics Department, Williams College, Williamstown, MA 01267,

  2. 2

    Physics Department, University of Michigan, Ann Arbor, MI 48109, and

  3. 3

    Biology Department, Williams College, Williamstown, MA 01267, USA

* †Author to whom correspondence should be addressed. E-mail: dwight.l.whitaker@williams.edu

Publication History

  1. Issue published online: 7 FEB 2007
  2. Article first published online: 7 FEB 2007
  3. Received 24 August 2006; accepted 14 December 2006 Editor: James Cresswell

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Keywords:

  • bunchberry;
  • dogwood;
  • plant motion;
  • pollination

Summary

  • 1
    Rapid movements in fungi and plants have evolved in different species to facilitate the dispersal of spores and seeds. The mechanisms of action can differ among species, but the effectiveness of these movements has rarely, if ever, been tested. Here we show through a quantitative biomechanical analysis that the stamens of Cornus canadensis L. (bunchberry) are ideal for catapulting pollen vertically at high speeds.
  • 2
    We develop a biomechanical model to describe the explosive launch of pollen from the flowers of bunchberry. The model determines the equation of motion for the stamens based only on the morphology and measurements of the parts of the stamens. To measure the motion of the stamens to compare with our model, we analysed individual frames of a video taken at 10 000 fps.
  • 3
    The thecae of adjacent stamens dehisce in bud so that the stomia face each other, retaining pollen between neighbouring anthers. As the flowers open, pollen is accelerated vertically as long as the thecae remain in contact. Pollen is released only when the anthers move horizontally and separate.
  • 4
    The observed motion of the stamens matches the results from our model through release of the pollen. The model reveals that pollen release (horizontal movement of the anthers) occurs only after the vertical speed is at its maximum. Thus, for this particular catapult mechanism, the morphology of the stamens is optimal for launching light, dry pollen straight upwards at high speed. Pollen launched vertically at high speed both enhances insect pollination by helping to making pollen stick on visiting insects, and also allows for successful wind pollination by propelling pollen into the air column. Seed set by inflorescences in pollinator-exclosure cages further supports the ability of this flower to use wind as a pollination mechanism.
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