Ryan T. McWilliams
Project Topic / Abstract:
"Aerodynamic Implications of Saccate Pollen"
Pollen grains of many wind-pollinated plants have one to
three air-filled sacci; these add considerable surface area,
but minimal weight. With a greater surface area to the wind
at a similar mass, it is thought - although not documented -
that sacci confer greater flight range to the pollen grain.
Using electron microscopy, structurally different saccate
pollen grains of three extant conifers (Pinus, Falcatifolium,
and Dacrydium) have been examined. Several characteristics
have been documented, including overall size, main body
size, saccus size, surface ornamentation, wall thickness,
wall infrastructure, saccus infrastructure, overall mass,
and wall mass. These have been incorporated into a custom
computer model programmed in C that calculates flight
properties for the theoretical grains based entirely on
structural data. The computer model has been tested by
stroboscopic photography of actual Pinus pollen. Using this
model, structural data can be incorporated from fossil
pollen to predict how grains may have flown. As such, the
model has been used to aerodynamically evaluate two fossil
grains, including the monosaccate pollen of Gothania (Cordaitales)
and the small, bisaccate grains of Caytonanthus (Caytoniales).
Although recent studies indicate that sacci have a buoyancy
function once grains reach a pollination drop in some extant
conifers, the present study provides the opportunity to
further evaluate the adaptive significance of saccate pollen
by correlating structural and aerodynamic features.
Presentations:
1997 Truman Undergraduate Research
Symposium (Kirksville, MO)
1998 Missouri Academy of Science (St.
Joseph, MO)
1998 Truman Undergraduate Research Symposium (Kirksville,
MO)
1999 National Conference on Undergraduate
Research (Rochester, NY)
1999 Sigma Xi Student Research Symposium
(Kirksville, MO)
1999 Truman Undergraduate Research
Symposium (Kirksville, MO)
1999 Undergraduate Research Poster Day at
the State Capital (Jefferson City, MO)
1999 International Botanical Congress (St.
Louis, MO)
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