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ARS Home » Southeast Area » Tifton, Georgia » Crop Protection and Management Research » Research » Publications at this Location » Publication #216787
Title: Preliminary estimates of pollen size, and settling velocity for Amaranthus palmeri

Author
item SOSNOSKIE, L - UNIV OF GA
item Webster, Theodore
item RAINS, G - UNIV OF GA
item DALES, D - UNIV OF GA
item CULPEPPER, A - UNIV OF GA

Submitted to: Weed Science Society of America Meeting Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: 10/10/2007
Publication Date: 2/4/2008
Citation: Sosnoskie, L.M., Webster, T.M., Rains, G., Dales, D., Culpepper, A.S. 2008. Preliminary estimates of pollen size, and settling velocity for Amaranthus palmeri [abstract]. Weed Science Society of America Abstracts. Paper No. 190.

Interpretive Summary:

Technical Abstract: Predictions of long-distance pollen dispersal require a priori knowledge regarding the size and terminal settling velocity of the pollen. Seed from four A. palmeri (AMAPA) populations (representing FL, GA, NC and TN) were planted and grown in a greenhouse. The extruded, but non-dehiscent, anthers were collected from eight male plants per population; pollen size was evaluated using light microscopy at 400X magnification. Pollen diameters ranged from 20 to 38 µm; mean pollen diameter was estimated to be 28 µm (+/- 2.39). There were no differences between populations with respect to pollen size. Our estimate is considerably larger than the previously published value (19.8µm) The settling velocity (Vs) of small, spherical particles (e.g. AMAPA pollen grains) under non-turbulent conditions can be predicted using Stoke's law. Assuming a mean diameter of 28.4µm, we determined the theoretical Vs of AMAPA pollen grains to be 2.9 to 3.9cm/s. Empirical estimates of Vs for freshly harvested pollen were generated in an acrylic settling chamber; a bulk sample of pollen grains were released at the top of a 2m tower and captured at the base using greased microscope slides attached to a rotating wooden disk. Results from the laboratory studies suggest that the mean Vs is ~5.0cm/s. The theoretical value for Vs was established using an equation that assumes particles maintain a constant shape, size, and density. Based on this information, we suspect that AMAPA pollen can likely move beyond field borders, further than initially suspected.