Reactive exhaust gases change or destroy odor profiles of flowers
By Summit Voice
Bees use floral odors to help locate, identify and recognize the flowers from which they forage, but diesel fumes are highly reactive and can change the profile of floral smells, according to University of Southhampton researchers Dr. Tracey Newman and Professor Guy Poppy.
For the study (published Oct. 3 in Scientific Reports), the scientists mixed eight chemicals found in the odor of oil rapeseed flowers with clean air, and with air containing diesel exhaust. Six of the eight chemicals reduced (in volume) when mixed with the diesel exhaust air and two of them disappeared completely within a minute. The odour that was mixed with the clean air was unaffected.
When the researchers used the same process with NOx gases (nitric oxide and nitrogen dioxide), which is found in diesel exhaust, they saw the same outcome, suggesting that NOx was a key facilitator in how and why the odor’s profile was altered. The altered chemical mix was then shown to honeybees, which could not recognize it.
“Honeybees have a sensitive sense of smell and an exceptional ability to learn and memorize new odours,” said Newman. “NOx gases represent some of the most reactive gases produced from diesel combustion and other fossil fuels, but the emissions limits for nitrogen dioxide are regularly exceeded, especially in urban areas,” Newman said.
“Our results suggest that that diesel exhaust pollution alters the components of a synthetic floral odour blend, which affects the honeybee’s recognition of the odor. This could have serious detrimental effects on the number of honeybee colonies and pollination activity,” he said.
“Honeybee pollination can significantly increase the yield of crops and they are vital to the world’s economy … However to forage effectively they need to be able to learn and recognize the plants,” Poppy said. “The results indicate that NOx gases — particularly nitrogen dioxide — may be capable of disrupting the odor recognition process that honeybees rely on for locating floral food resources.
“Honeybees use the whole range of chemicals found in a floral blend to discriminate between different blends, and the results suggest that some chemicals in a blend may be more important than others,” Poppy concluded.