Does particulate matter along roadsides interfere with plant reproduction? A comparison of effects of different road types on Cichorium intybus pollen deposition and germination

The roadside habitat can be challenging for plants, which must maintain normal biological processes despite an influx of airborne pollutants. While the effects of many gases on plants have been quantified, the impacts of particulate pollutants have been relatively less studied. This is especially true of field experiments where particle dispersion may be influenced by meteorology and roadway use. We examined chicory (Cichorium intybus L) along roadsides in the Cincinnati, Ohio metropolitan area to assess particulate influence on plant pollination through stigmatic clogging. We compared flowers collected from plants situated along interstates, U.S. highways, state highways, and county roads as these different road-types vary in motor vehicle usage and thus should have varying levels of particulate deposition on flowers. We examined floral stigmas for total particulates, total pollen, and percentage of pollen tube germination to determine whether particulates may interfere with early reproductive processes. Our results suggest that there was minimal variation of particulate matter found on chicory stigmas among road-types. Furthermore, the deposition of particulates on stigmas based on road-type did not show a strong link to variation in pollen deposition and pollen germination. There was also no significant relationship between total particulate levels and pollen germination rates across all road types. Future studies should investigate other plant species that may be more sensitive to roadside pollution, such as economically important crops. Locations in which vehicle use is increasing and where pollutants are not regulated strictly should also be examined as the effects of airborne particulates in early plant reproduction would be expected to be more substantial in these areas. (C) 2017 Elsevier Ltd. All rights reserved.