CO2 emissions may affect flowering plants

University scientists research crop flowering times

By Francesca Chambers

Friday, November 16, 2007

It’s basic, junior-high science. Carbon dioxide plus water, plus sunlight equals healthy, happy plants. So theoretically, increased amounts of CO2 in the air would yield super plants. But Joy Ward, an assistant professor in the department of ecology and evolutionary biology at the University of Kansas, said sometimes too much of a good thing could be bad.

Ward and Clint Springer, a postdoctoral researcher who works in Ward’s lab, have found that increased levels of CO2 in the atmosphere could cause plants to flower later.

“What we found in this study is there is a lot of variability in the responses. And to generalize those, there is no single factor that dictates whether a plant will have accelerated or delayed flowering,” Springer said. “We uncovered a big question.”

Ward and Springer recently published the study “Flowering time and elevated atmospheric CO2” in the botany journal New Phytologist. Although the review was primarily a synthesis of other researchers’ work, which Springer and Ward said was the most comprehensive synthesis on this subject to date, the two contributed work of their own to the paper as well.

In their papers, Ward and Springer looked at how elevated levels of atmospheric CO2 affect the genetic and molecular mechanisms that control plant flowering. Ward and Springer also acknowledged the implications their work could have on agricultural crops. They hope to incorporate their work into crop breeding in the future. Carbon dioxide is a naturally occurring gas, but additional CO2 is created through the burning of petroleum based fossil fuels and coal.

Ward said people needed to be more aware of the effects that an increase in CO2 emissions were having on the environment.

“People are well aware that global warming is affecting plant development timing,” Ward said. “We’ve ignored the factor of carbon dioxide.”

For their own research, Ward and Springer collected genotypes, or breeds, of the Arabidopsis thaliana, the mouse-ear cress plant, from 10 different geographical regions in the world. They grew the plants in controlled growth chambers at the current atmospheric level of CO2, 380 parts per million, or ppm, and at the level they predict CO2 will be at in 50 to 80 years, 700 ppm.

Consistent with other researchers’ studies, Springer and Ward found that carbohydrates play a role in plant development. Ward said sugars sometimes acted as a signaling molecule for plants to flower. Springer said that inconsistency in the flowering times of the plants suggested that plants of the same species across the world were evolving differently.

In the future, Ward said she would focus on the evolutionary factors affecting plant development in her lab. Springer will focus on the molecular mechanisms in his new lab at St. Joseph’s University in Philadelphia, where he recently accepted a professorship. Springer said they hoped to pinpoint why and how plants were reacting to CO2 and to apply their research to other plants that had a commonality in their make-up.

According to Ward and Springer’s paper, few studies have examined crop flowering-time responses to elevated levels of CO2. In the existing studies, 80 percent of those crops showed accelerated flowering times.

“Once we understand how genetics play a role in this, that will be more for people who are interested in how it affects crops,” Springer said.

But researchers in the department of geography are concerned now. Nate Brunsell, assistant professor of geography, said that plants would have to take in more water to counter the increased amounts of CO2. Brunsell said he expected these environmental issues to begin affecting students’ lives in the near future. He said Georgia already had put restrictions on how much water citizens could use daily.

“You also have a food security issue. If we heat things up and lose more water, what are farmers going to do?” Brunsell said. “Change crops? Use more water? When you use more water for agriculture, then there is less for municipal and recreation uses.”

Kees van der Veen, an associate professor in the department of geography, said he expected another Dust Bowl in Kansas, similar to the one in the 1930s.

In their synthesis, Ward and Springer already found that sorghum showed a delayed development time. Beers such as Guinness and Anheuser-Busch’s Redbridge contain sorghum in its syrup form. According to the National Sweet Sorghum Producers and Processors Association’s Web site, sorghum is a key ingredient in cattle feed and is a major crop in Kansas.

Currently, CO2 emissions are not regulated in the U.S. Kansas already has taken a controversial step in this direction by refusing to allow Westar Energy to build a coal plant in Holcomb. Rod Bremby, secretary of the Kansas Department of Health and Environment, first rejected the plan, and Governor Kathleen Sebelius upheld his decision.

But Springer said his and Ward’s work was not only important to Kansas, but also to the world. “In the developing nations of the world, this will have major impacts,” Springer said. “The U.S. is more buffered because of our wealth.”

— Edited by Elizabeth Cattell

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