Although neither of them is allergic to ragweed, the students know how easily it can trigger a response among those who are. Concentrations of fewer than 10 pollen grains per cubic meter can cause an allergic reaction in people who are sensitive to ragweed, said Martin, who is from Lafayette, La. During our field research, we found concentrations of 10,000 grains per cubic meter in the air above the plants. My clothes were stained yellow with pollen.
Although ragweed is not new to North America, other scientists have determined that it has spread significantly throughout the continent since the arrival of European settlers. The newcomers cleared shady forest areas to create farmland, enabling ragweed to flourish in the sunny new open spaces. Im trying to develop a detailed description of the recent evolution of ragweed populations, Martin said. I want to know how the plants structure and behavior have influenced its success as an invasive weed. If we can understand how ragweed was adapted to its prehistoric environment, we may find better ways to control its harmful effects in the present day by predicting when the pollen will be released and where it will end up.
His fellow researcher has somewhat different aims. My main interest is learning how the wind spreads the pollen under different turbulence and temperature conditions, said Chamecki, who is from Curitiba, Brazil. I want to use the data from our field experiments to develop and calibrate a computer model. This model could be used to predict how pollen grains are likely to spread under different topographic and atmospheric conditions. If the computer model works for ragweed, it should also work for other types of pollen and other tiny airborne particles and organisms like bacteria, soot and even snowflakes.
In the immense ragweed field, the graduate students gathered data by first marking off 25 randomly selected study sites, each m
|Contact: Phil Sneiderman|
Johns Hopkins University