The students knew that ragweed reproduces in the late summer and early fall when male flowers release pollen to fertilize female portions of the plant, which release seeds. To study this process, they aimed a video camera at male flowers, using a close-up lens. The camera captured microscopic images of pollen being released in clumps of about 500 grains each. The student researchers later were able to document the way such clumps begin to fall apart and disperse as they move through the air.
To find out how the airborne pollen concentration changes as the clumps move away from the plants, the researchers set up an 18-foot-tall pole equipped with six pollen samplers mounted at different heights. Each sampler spun a rod coated with sticky silicone to capture pollen clumps moving through the air. The students have been able to count and study the pollen grains by placing the samples under a microscope.
To document weather conditions at the time of each sampling, the students assembled a meteorological tower 6 meters tall. The tower was equipped with instruments to measure solar radiation, air temperature, humidity, wind direction, wind speed and turbulence. This information was collected by a datalogger device and stored on a memory card that could be uploaded regularly to a laptop computer. The towers devices were powered by a car battery recharged by solar cells.
The students left the ragweed field with two weeks worth of pollen behavior data that they are continuing to or
|Contact: Phil Sneiderman|
Johns Hopkins University