Rising CO2 and pollen production of common ragweed (Ambrosia artemisiifolia), a known allergy-inducing species: implications for public health

Although environmental factors such as precipitation and temperature are re cognized as influencing pollen production, the impact of rising atmospheric carbon dioxide concentration ([ CO2]) on the potential growth and pollen p roduction of hay- fever- inducing plants is unknown. Here we present measur ements of growth and pollen production of common ragweed (Ambrosia artemisi ifolia L.) from pre- industrial [CO2] (280 mu mol mol(-1)) to current conce ntrations (370 mu mol mol(-1)) to a projected 21st century concentration (6 00 mu mol mol(-1)). We found that exposure to current and elevated [CO2] in creased ragweed pollen production by 131 and 320%, respectively, compared t o plants grown at pre- industrial [CO2]. The observed stimulations of polle n production from the pre- industrial [CO2] were due to an increase in the number (at 370 mu mol mol(-1)) and number and size (at 600 mu mol mol(-1)) of floral spikes. Overall, floral weight as a percentage of total plant wei ght decreased (from 21% to 13%), while investment in pollen increased (from 3.6 to 6%) between 280 and 600 mu mol mol(-1) CO2. Our results suggest tha t the continuing increase in atmospheric [CO2] could directly influence pub lic health by stimulating the growth and pollen production of allergy- indu cing species such as ragweed.