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Pollen Dispersal by Catapult: Experiments of Lyman J. Briggs on the Flower of Mountain Laurel

Abstract

The flower of Kalmia latifolia L. employs a catapult mechanism that flings its pollen to considerable distances. Physicist Lyman J. Briggs investigated this phenomenon in the 1950s after retiring as longtime director of the National Bureau of Standards, attempting to explain how hydromechanical effects inside the flower’s stamen could make it possible. Briggs’s unfinished manuscript implies that liquid under negative pressure generates stress, which, superimposed on the stress generated from the flower’s growth habit, results in force adequate to propel the pollen as observed. With new data and biophysical understanding to supplement Briggs’s experimental results and research notes, we show that his postulated negative-pressure mechanism did not play the exclusive and crucial role that he credited to it, though his revisited investigation sheds light on various related processes. Important issues concerning the development and reproductive function of Kalmia flowers remain unresolved, highlighting the need for further biophysical advances.

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Notes

  1. After 1988, the National Institute of Standards and Technology (NIST).

  2. Figure 2 defines “corolla,” “stamen,” and other botanical terms. An anther is the end portion of the stamen, which contains the pollen. Stamens, each of which is the active member of a catapult, are visible in figure 1 as curved filaments about 10 mm in length with their basal ends attached to the center of the flower.

  3. Quantitatively, these properties are represented by the elastic limit, which indicates how much bending can be sustained without damaging the ability to spring back, and Young’s modulus, the amount of bending force associated with a given degree of bend.

  4. Briggs measured the filament length to be 11 mm, the straight-line distance between the fixed and pinned ends of the bent filament 7 mm, the filament width 0.44 mm at midpoint and 0.56 mm near the basal end, and thickness (from abaxial to adaxial edge) 0.25 mm. The pinned filament was bent abaxially 90°; some time after flinging it was bent adaxially 180°.

  5. Unfortunately, this conception of the stamen having a circular cross section and a hollow chamber along its axis does not correspond well with the actual stamen anatomy, as described below.

  6. Additional details are available at http://wwwrcamnl.wr.usgs.gov/uzf/abs_pubs/papers/Nimmo_etal.2014.Pollen_Dispersal_Biomechanics.appendix.pdf.

  7. It may be helpful to note the rigorous definition of stiffness as the ratio of imposed force to resulting displacement of a body, an extensive property based on dimensions as well as an intensive material modulus.

  8. Later renamed the Biophysical Laboratory.

References

  1. Edward R. Landa and John R. Nimmo, “The Life and Scientific Contributions of Lyman J. Briggs,” Soil Science Society of America Journal 67 (2003) (3), 681–693, cover, i.

  2. J. Edwards, D. Whitaker, S. Klionsky, and M. J. Laskowski, “A Record-Breaking Pollen Catapult,” Nature 435 (2005), 164; J. M. Skotheim and L. Mahadevan, “Physical Limits and Design Principles for Plant and Fungal Movements,” Science 308 (2005), 1308–1310.

  3. Marcus J. King and Stephen L. Buchmann, “Bumble Bee–Initiated Vibration Release Mechanism of Rhododendron Pollen,” American Journal of Botany 82 (1995), 1407–1411.

  4. W. J. Beal, “Agency of Insects in Fertilizing Plants,” American Naturalist 1 (1867), 254–260.

  5. A. C. Leopold and P. E. Kreidemann, Plant Growth and Development (New York: McGraw Hill, 1975), 2nd ed.

  6. Massimo Bianchini and Ettore Pacini, “Explosive Anther Dehiscence in Ricinus communis L. Involves Cell Wall Modifications and Relative Humidity,” International Journal of Plant Sciences (1996), 739–745.

  7. P.F. Stevens, J. Luteyn, E. G. H. Oliver, T. L. Bell, E. A. Brown, R. K. Crowden, A. S. George, G. J. Jordan, P. Ladd, and K. Lemson, “Ericaceae,” in The Families and Genera of Vascular Plants, ed. K. Kubitzki (Berlin: Springer, 2004), 6:145–194.

  8. A. C. Crawford, Mountain Laurel, a Poisonous Plant. Bureau of Plant Industry, U. S. Department of Agriculture, Bulletin No. 121, 1908; J. E. Ebinger, “Laurels in the Wild”, in Kalmia: The Laurel Book II, ed. R.A. Jayne (Portland, OR: Timber Press, 1988), 15–42; W. B. Zomlefer, Guide to Flowering Plant Families. (Chapel Hill, NC: University of North Carolina Press, 1994).

  9. Ebinger, “Laurels in the Wild” (ref. 8), 21.

  10. Karl J. Niklas, Plant Biomechanics: An Engineering Approach to Plant Form and Function. (Chicago: University of Chicago Press, 1992), 109–112, describes the flinging biomechanics in the related species Kalmia angustifolia.

  11. B. Rathcke and L. Real, “Autogamy and Inbreeding Depression in Mountain Laurel, Kalmia latifolia (Ericaceae),” American Journal of Botany 80 (1993), 143–146; Beal, “Agency of Insects” (ref. 4); Ebinger, “Laurels in the Wild” (ref. 8).

  12. Landa and Nimmo, “Life and Scientific Contributions of Briggs” (ref. 1).

  13. Lyman James Briggs, The Mechanics of Soil Moisture. USDA Bureau of Soils, Bulletin No. 10, 1897.

  14. John R. Nimmo and Edward R. Landa, “The Soil-Physics Contributions of Edgar Buckingham,” Soil Science Society of America Journal 69 (2005), 328–342.

  15. L. J. Briggs, “Effect of Spin and Speed on the Lateral Deflection (Curve) of a Baseball; and the Magnus Effect for Smooth Spheres,” American Journal of Physics 27 (1959), 589–596.

  16. U. Zimmermann, H. Schneider, L. H. Wegner, and A. Haase, “Water Ascent in Tall Trees: Does Evolution of Land Plants Rely on a Highly Metastable State?” New Phytologist 162 (2004), 575–615; M. B. Kirkham, Principles of Soil and Plant Water Relations. (Burlington, MA: Elsevier, 2005), 518; N. Michele Holbrook and Maciej A. Zwieniecki, “Transporting Water to the Tops of Trees,” Physics Today 61 (1) (2008), 76–77; Harvey R. Brown, “The Theory of the Rise of Sap in Trees—Some Historical and Conceptual Remarks,” Physics in Perspective 15 (2013), 320–358.

  17. Kemmerer, e-mail to Landa, May 7, 2003.

  18. J.M. Frankland, “Book Review: Progress in Solid Mechanics. vol. 1. I. N. Sneddon and R. Hill, eds.,” Science 132 (1960), 1144–1145.

  19. Lyman J. Briggs, “Records Relating to Scientific Work, 1907–1962 Office Files of Lyman J. Briggs,” (College Park, MD: National Archives and Records Administration, 1954–1958) Record Group 167 (National Institute of Standards and Technology), entry 2, box 14, 1954–1958.

  20. See http://www.humboldt.edu/scimus/Instruments/ChainBal-BKH/ChainBal.htm, accessed June 4, 2013.

  21. Lionel S. Marks, Mechanical Engineers’ Handbook (New York: McGraw Hill, 1930), 3rd ed.

  22. Samuel J. Record, The Mechanical Properties of Wood (New York: Wiley, 1914).

  23. W. R. Gardner and C. F. Ehlig, “Physical Aspects of the Internal Water Relations of Plant Leaves,” Plant Physiology 40 (1965), 705.

  24. Paula Hermann de Villamil, “Stamens in the Ericaceae—A Developmental Study,” PhD diss., Rutgers University, 1980.

  25. The specimens were both cultivated (from Horticultural Garden, Rutgers University, NJ) and wild plants (Great Smoky Mountains, NC–TN). The stamens had been kept in formaline-acetic acid-alcohol. They were embedded in Paraplast, sectioned at 7-10 µm, stained with safranin-fast green, and observed under a compound microscope.

  26. This behavior is as observed by Alarich Kress, “Funktion und Verhalten der Staubblätter von Kalmia,” Naturwissenschaftliche Rundschau 45 (1992), 278–279, who found that cut stamens immersed in a water bath continue to curl for a few hours after flinging.

  27. Alarich Kress, private communication, March 24, 2009 referring to “Beobachtungen an Bluten von Kalmia latifolia L. (Ericaceae),” Phytologia 65 (1988) (4), 249–284.

  28. Kress, “Funktion und Verhalten der Staubblätter von Kalmia” (ref. 27).

  29. Paula M. Hermann and Barbara F. Palser, “Stamen Development in the Ericaceae. I. Anther Wall, Microsporogenesis, Inversion, and Appendages,” American Journal of Botany 87 (2000), 934-957, on 940.

  30. Sharon J. Gerbode, Joshua R. Puzey, Andrew G. McCormick, and L. Mahadevan, “How the Cucumber Tendril Coils and Overwinds,” Science 337 (2012), 1087–1091.

  31. L. J. Briggs, “The Living Plant as a Physical System,” Journal of the Washington Academy of Sciences 7 (1917), 89–111.

  32. W. T. Swingle and L. J. Briggs, “Improvements in the Ultra-Violet Microscope,” Science 26 (1907), 180–183.

  33. Allen V. Astin, “Lyman James Briggs 1874–1963,” Cosmos Club Bulletin (1977), 2–6.

  34. See http://www.biophysics.org/AboutUs/Overview/BPSAShortHistory/tabid/2929/Default.aspx, accessed June 4, 2013.

  35. B. S. Meyer and D. B. Anderson, Plant Physiology (New York: D. Van Nostrand, 1952).

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Acknowledgments

We are grateful to Dr. Alarich Kress (Munich Botanical Garden, retired) and to Dr. Richard C. Keating (Missouri Botanical Garden) for detailed information on the flower of Kalmia latifolia.

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Correspondence to John R. Nimmo.

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John R. Nimmo is a Research Physicist with the US Geological Survey and leader of the Unsaturated Flow Processes research group.

Paula M. Hermann (at present retired) was an Associate Professor at the Departamento de Biología, Bioquímica y Farmacia, Universidad Nacional del Sur, Argentina.

M. B. Kirkham is a Professor in the Department of Agronomy at Kansas State University and Fellow of the American Association for the Advancement of Science.

Edward R. Landa is an Adjunct Professor, Department of Environmental Science and Technology, University of Maryland at College Park, and Scientist Emeritus at USGS Reston, Virginia.

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Nimmo, J.R., Hermann, P.M., Kirkham, M.B. et al. Pollen Dispersal by Catapult: Experiments of Lyman J. Briggs on the Flower of Mountain Laurel. Phys. Perspect. 16, 371–389 (2014). https://doi.org/10.1007/s00016-014-0141-9

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Keywords

  • Biomechanics
  • biophysics
  • Lyman J. Briggs
  • Kalmia latifolia
  • elastic properties
  • catapult
  • negative pressure
  • pollen dispersal
  • botany
  • plant-water relations