Ozone masks plants volatiles, plant eating insects confused

April 02, 2013

Increases in ground-level ozone, especially in rural areas, may interfere not only with predator insects finding host plants, but also with pollinators finding flowers, according to researchers from Penn State and the University of Virginia.

"Ozone pollution has great potential to perniciously alter key interactions between plants and animals," the researchers said in a recent issue of Environmental Research Letters.

The animal tested in this case was the striped cucumber beetle, a predator of cucurbits -- cucumber, squash, pumpkin and melons. These insects dine on the plants from the moment they emerge from the ground and when fruit forms, they eat that as well.

"Insects detect odor with olfactory receptors located on their antennae," said Jose D. Fuentes, professor of meteorology, Penn State. "These receptors sense plant-emitted volatile organic compounds in very small amounts -- as low as six molecules hitting an antenna."

However, ozone, which is a very reactive substance, degrades the volatile organic compounds when they mix to the point where they no longer stimulate the olfactory system.

Fuentes, working with John Zenker, Penn State undergraduate in meteorology, and T'ai H. Roulston, research associate professor and curator, Blandy Experimental Farm, University of Virginia, tested the beetles in an enclosed Y-tube apparatus so that the insect could choose which branch to take. Researchers collected the insects from pumpkin and squash plants. They tested the insects using buffalo gourd plants, a naturally growing wild gourd that likes semiarid areas.

Separate air streams flowed into the two branches of the Y-tube. Choices of air in each tube were ambient filtered air, ambient filtered air plus up to 120 parts per million ozone, ambient filtered air plus volatile organic compounds, or air plus up to 120 parts per billion ozone and volatile organic compounds from the plant. To obtain this mix, or only ozone or volatile organic compounds, that branch flowed either to a plant chamber or ozone generator or both.

The researchers tested the insects with all ambient air, with ambient air and ozone, with ambient air and volatile organic compounds, and with ambient air and a mix of ozone and volatile organic compounds. When presented with an ambient air or volatile organic compound airstream, the beetles chose the volatile organic compound tube 80 percent of the time.

"However, as the ozone levels increased, they chose the path to the flower less frequently," said Fuentes. "By the time the mix contained 80 parts per billion ozone, the beetles showed no preference for either tube."

The researchers also tested the beetles with volatile organic compounds and a mix of volatile organic compounds and ozone. At low ozone levels, the insects showed no preference, but as ozone levels increased, the insects increasingly preferred the ozone-free path. At 80 parts per billion, the beetles chose the volatile organic compounds without ozone significantly more often than the ozonized mixture.

While one might think that higher ozone levels in the lower atmosphere would improve crops because predator insects would be unable to find their hosts, the additional ozone would also interfere with mutualistic insect plant responses such as pollination.
-end-
The National Science Foundation supported this research.

Penn State

Related Ozone Articles from Brightsurf:

Investigating the causes of the ozone levels in the Valderejo Nature Reserve
The UPV/EHU's Atmospheric Research Group (GIA) has presented a database comprising over 60 volatile organic compounds (VOC) measured continuously over the last ten years in the Valderejo Nature Reserve (Álava, Basque Country).

FSU Research: Despite less ozone pollution, not all plants benefit
Policies and new technologies have reduced emissions of precursor gases that lead to ozone air pollution, but despite those improvements, the amount of ozone that plants are taking in has not followed the same trend, according to Florida State University researchers.

Iodine may slow ozone layer recovery
Air pollution and iodine from the ocean contribute to damage of Earth's ozone layer.

Ozone threat from climate change
We know the recent extreme heat is something that we can expect more of as a result of increasing temperatures due to climate change.

Super volcanic eruptions interrupt ozone recovery
Strong volcanic eruptions, especially when a super volcano erupts, will have a strong impact on ozone, and might interrupt the ozone recovery processes.

How severe drought influences ozone pollution
From 2011 to 2015, California experienced its worst drought on record, with a parching combination of high temperatures and low precipitation.

New threat to ozone recovery
A new MIT study, published in Nature Geoscience, identifies another threat to the ozone layer's recovery: chloroform -- a colorless, sweet-smelling compound that is primarily used in the manufacturing of products such as Teflon and various refrigerants.

Ozone hole modest despite optimum conditions for ozone depletion
The ozone hole that forms in the upper atmosphere over Antarctica each September was slightly above average size in 2018, NOAA and NASA scientists reported today.

Increased UV from ozone depletion sterilizes trees
UC Berkeley paleobotanists put dwarf, bonsai pine trees in growth chambers and subjected them to up to 13 times the UV-B radiation Earth experiences today, simulating conditions that likely existed 252 million years ago during the planet's worst mass extinction.

Ozone at lower latitudes is not recovering, despite Antarctic ozone hole healing
The ozone layer -- which protects us from harmful ultraviolet radiation -- is recovering at the poles, but unexpected decreases in part of the atmosphere may be preventing recovery at lower latitudes.

Read More: Ozone News and Ozone Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.