Effects of NO2 on Inflorescence Length, Pollen/Seed Amount and Phenolic Metabolites of Common Ragweed (Ambrosia artemisiifolia L.)

Ambrosia artemisiifolia (common ragweed) is native to North America; it is a monoecious and wind-pollinated herbaceous annual plant that belongs to the Asteraceae family and has expanded its distribution out of its native range to Europe, Australia, Asia, South Africa and South America. And its pollen is known to be highly allergenic.

Environmental changes may increase the severity of pollen as stimulated atopic disease by influencing the large-scale distribution and local incidence of allergenic species, the flowering time, the pollen production and the allergenicity of individual pollen grains. It has been shown that elevated CO₂ concentrations result in an increase of A. artemisiifolia growth and pollen production.

In this study, the authors altered the gaseous air pollution by linking the pollen and seed production of A. artemisiifolia with elevated NO₂ levels and emphasized that this environmental change affected the pollen amount, as well as phenolic metabolites, which is relevant to human health.

A. artemisiifolia seeds were collected from a single plant at an outdoor stand (Bad Waldsee, Baden-Württemberg, Germany) to prevent epigenetic-caused effects. Seeds were sown in standard soil (Floradur®, Bayerische Gärtnerei Genossenschaft, München, Germany) in small multiflor palettes (6 × 6 cm) and transferred into four Plexiglas sub-chambers (1.1 m × 0.9 m × 0.8 m) that were placed in Phytotron walk-in chambers. All physical parameters, including the wind velocity were identical in the sub-chambers.

The results indicated that regarding morphological parameters, increased NO₂ had no effect on the inflorescence length, whereas elevated CO₂ resulted in an increased length of the main inflorescence; regarding allergenicity, the pollen amount clearly increased in both years of the study by approximately 70% to 80%.

In conclusion, the data on A. artemisiifolia fumigated with elevated NO₂ support the hypothesis that the overall allergenicity might be increased by an increased pollen amount. However, differences in the estimation of allergen exposure between pollen amount and ELISA data must be considered. As the overall seed production decreased under elevated NO₂, the dispersal of A. artemisiifolia should not be affected by this air pollutant.

Article by Feng Zhao, et al, from Germany and Switzerland.

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