Interaction of the Onset of Spring and Elevated Atmospheric CO ₂ on Ragweed ( Ambrosia artemisiifolia L.) Pollen Production

Abstract

Increasing atmospheric carbon dioxide is responsible for climate changes that are having widespread effects on biological systems. One of the clearest changes is earlier onset of spring and lengthening of the growing season. We designed the present study to examine the interactive effects of timing of dormancy release of seeds with low and high atmospheric CO2 on biomass, reproduction, and phenology in ragweed plants (Ambrosia artemisiifolia L.), which produce highly allergenic pollen. We released ragweed seeds from dormancy at three 15-day intervals and grew plants in climate-controlled glasshouses at either ambient or 700-ppm CO2 concentrations, placing open-top bags over inflorescences to capture pollen. Measurements of plant height and weight; inflorescence number, weight, and length; and days to anthesis and anthesis date were made on each plant, and whole-plant pollen productivity was estimated from an allometric-based model. Timing and CO2 interacted to influence pollen production. At ambient CO2 levels, the earlier cohort acquired a greater biomass, a higher average weight per inflorescence, and a larger number of inflorescences; flowered earlier; and had 54.8% greater pollen production than did the latest cohort. At high CO2 levels, plants showed greater biomass and reproductive effort compared with those in ambient CO2 but only for later cohorts. In the early cohort, pollen production was similar under ambient and high CO2, but in the middle and late cohorts, high CO2 increased pollen production by 32% and 55%, respectively, compared with ambient CO2 levels. Overall, ragweed pollen production can be expected to increase significantly under predicted future climate conditions.

Is the recent decrease in airborne Ambrosia pollen in the Milan area due to the accidental introduction of the ragweed leaf beetle Ophraella communa?

“…This is because Ambrosia seeds require moist chilling (stratification) before they can germinate (Pickett and Baskin 1973;Willemsen 1975;Baskin 1977, 1980). Ambrosia plants that emerge earlier have been shown to grow larger, and Ambrosia pollen production is directly correlated with biomass (Rogers et al 2006;Fumanal et al 2007). In addition, lower temperatures in June may facilitate reproductive growth because, as seen with chrysanthemums (close relatives to both Ambrosia), exposure to high temperatures at the beginning of the short-day period results in a notable delay both in initiation and further (Cockshull and Kofranek 1994).…”

Recent warming by latitude associated with increased length of ragweed pollen season in central North America

“…Because of its wellrecognized association with allergic disease, a number of studies have demonstrated a probable role between climate change (i.e., rising CO 2 and temperature), phenology, and pollen production of common ragweed (29)(30)(31). However, these links were established at the laboratory level (30) and as a function of urbanization (27).…”

The toxicology of climate change: Environmental contaminants in a warming world

“…Shifts in plant populations have already been documented as a result of climate change (Rogers et al, 2006;Root et al, 2003;Singer et al, 2005). For example, studies show that increasing concentrations of CO 2 enhance the production of Amb a 1 allergen and pollen from ragweed (Ambrosia artemisiifolia L.) (Rogers et al, 2006;Singer et al, 2005).…”

“…For example, studies show that increasing concentrations of CO 2 enhance the production of Amb a 1 allergen and pollen from ragweed (Ambrosia artemisiifolia L.) (Rogers et al, 2006;Singer et al, 2005). In addition, diesel exhaust, which contains numerous pollutants, including PM, NOx, VOCs, CO, and polycyclic aromatic hydrocarbons (PAHs), has been shown to enhance allergenicity and asthma symptoms in adults and children by acting synergistically with allergens (D' Amato et al, 2002;Diaz-Sanchez et al, 2003;Janssen et al, 2003).…”