Smithsonian Postdoc Leads Field Demonstration

| September 20, 2011

Being the tallest in the class, Alexis Rukenbrod ’12 was elected to collect a sample to demonstrate what the LI-6400 can do.

Hopping onto a concrete bench in front of Guion Science Center, she stretched to pluck a leaf from as far up the redbud’s canopy as she could reach. The leaf had to be exposed to full sun, because the object of the day’s lab was to compare photosynthesis, transpiration and respiration rates in plants as levels of light and carbon dioxide concentration change.

Before it was over they would collect data points on sun- and shade-adapted foliage from the redbud tree and from ornamental sawgrass to demonstrate how species that use different “photosynthetic pathways” respond to environmental conditions. To do so, they had the favor of using a $60,000 piece of equipment belonging to the Smithsonian Environmental Research Center.

Thomas Mozdzer, a Smithsonian Institution postdoctoral fellow, demonstrated how the device works as a guest lecturer in biologist Zoe Smith’s Conserving Ecological Interaction class. Some of what he hoped to accomplish was to familiarize the students with the sophisticated, but commonly used machines that biologists and environmental scientists use in the field.

LI-COR’s LI-6400 Portable Photosynthesis System uses infrared radiation to measure plant gas exchange from a leaf sample placed in its chamber. The LI-6400 is a souped-up model capable of controlling environmental factors that the plant is being exposed to. By imposing changes in temperature, light and carbon dioxide levels, the machine provides insight into the plant’s metabolic needs — nearly instant readouts indicate when photosynthesis and transpiration rates are optimal, i.e., when the plant is happiest.

One benefit to this feature is understanding how rising carbon dioxide in the atmosphere affects particular species. Through the “miracle of the LI-COR 6400,” Mozdzer said, scientists can predict how well plants will deal with global change years from now.

Category: Environmental Science, Environmental Studies, Uncategorized