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The aerodynamics and efficiency of wind pollination in grasses
Article first published online: 24 MAR 2010
DOI: 10.1111/j.1365-2435.2010.01704.x
© 2010 The Authors. Journal compilation © 2010 British Ecological Society
Additional Information
How to Cite
Cresswell, J. E., Krick, J., Patrick, M. A. and Lahoubi, M. (2010), The aerodynamics and efficiency of wind pollination in grasses. Functional Ecology, 24: 706–713. doi: 10.1111/j.1365-2435.2010.01704.x
Publication History
- Issue published online: 13 JUL 2010
- Article first published online: 24 MAR 2010
- Received 25 November 2009; accepted 22 February 2010 Handling Editor: Charles Fox
- Abstract
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- References
- Cited By
Keywords:
- Alopecurus pratensis;
- Anthoxanthum odoratum;
- CFD;
- collection efficiency;
- computational fluid dynamics;
- cross-pollination;
- Poaceae;
- pollination
Summary
1. Under natural selection for sexual success, the reproductive organs of plants should evolve to become highly effective pollen receptors. Among wind-pollinated plants, larger reproductive structures appear counter-adapted to accumulate pollen by impaction on their windward surfaces, because airborne particles are less able to penetrate the thicker boundary layer of larger targets. Therefore, it has been proposed that wind-pollinated plants with pollen receptors on relatively large structures, like some grasses (family Poaceae), are architecturally adapted to create downstream vortices in which airborne pollen recirculates before accumulating on leeward surfaces. From this basis, the striking diversity among the grasses in the architecture of their flowering stems has been attributed in part to the existence of these contrasting mechanisms for effecting pollen receipt, namely impact collection and recirculatory collection.
2. We investigated the relative importance of impact and recirculatory collection in grasses by analysing a model system in silico using Computational Fluid Dynamics and by conducting in vivo experiments, both in a wind tunnel and outdoors, using two grass species with compact inflorescences, Alopecurus pratensis and Anthoxanthum odoratum.
3. Irrespective of the experimental approach, we found that although pollen recirculated in the leeward eddies of inflorescences, over 95% of the accumulated pollen was collected by windward surfaces.
4. In A. pratensis, the collection efficiency (proportion of oncoming pollen collected) was between 5% and 20%, depending on wind speed in the range 0·5–1·9 m s−1 and these levels conform to those predicted by a mechanistic model of impact collection.
5. Our results demonstrate that grass species with larger inflorescences are, like those with smaller inflorescences, primarily impact collectors of airborne pollen, which suggests that dissimilar reproductive morphology among species cannot be attributed to differentiation in the mode of pollen capture and, instead, requires reference to other factors, such as the need to produce, protect and disperse seeds of different sizes in different environments.