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ELECTROSTATIC FORCES IN WIND-POLLINATION: PART 1: MEASUREMENT OF THE ELECTROSTATIC CHARGE ON POLLEN
Citation:
BOWKER, G. E. AND H. C. CRENSHAW. ELECTROSTATIC FORCES IN WIND-POLLINATION: PART 1: MEASUREMENT OF THE ELECTROSTATIC CHARGE ON POLLEN. ATMOSPHERIC ENVIRONMENT. Elsevier Science Ltd, New York, NY, 41(8):1587-1595, (2007).
Impact/Purpose:
The objective of this task is to improve the ability to model emissions from selected environmentally-dependent sources, test the performance of the models, incorporate them into a larger emission-modeling framework, and evaluate the effect of the emission models in support of improving the performance of CMAQ at all spatial and temporal scales. Evaluation will be with respect to previous CMAQ modeling results and ambient concentration data. In addition, the task will provide ADP and GIS contractor support for the generation and application of emission data in support of CMAQ development and evaluation as well as emission research.
Description:
Under fair weather conditions, a weak electric field exists between negative charge induced on the surface of plants and positive charge in the air. This field is magnified around points (e.g. stigmas) and can reach values up to 3x106 V m-1. If wind-dispersed pollen grains are electrically charged, the electrostatic force (which is the product of the pollen's charge and the electric field at the pollen's location) could influence pollen capture. In this article, we report measurements of the electrostatic charge carried by wind-dispersed pollen grains. Pollen charge was measured using an adaptation of the Millikan oil-drop experiment for seven anemophilous plants: Acer rubrum, Cedrus atlantica, Cedrus deodara, Juniperus virginiana, Pinus taeda, Plantago lanceolata and Ulmus alata. All species had charged pollen, some were positive others negative. The distributions (number of pollen grains as a function of charge) were bipolar and roughly centered about zero although some distributions were skewed towards positive charges. Most pollen carried small amounts of charge, 0.8 fC in magnitude, on average. A few carried charges up to 40 fC. For Juniperus, pollen charges were also measured in nature and these results concurred with those found in the laboratory. For nearly all charged pollen grains, the likelihood that electrostatics influence pollen capture is evident.