May 21, 2009

LEDs used to produced plant antioxidants

U.S. scientists say they are experimenting with ultraviolet light-emitting diodes to create darker, redder lettuce that is rich in antioxidants

Plant physiologists led by Steve Britz of the U.S. Department of Agriculture in Beltsville, Md., said spinach has more nutritional value than iceberg lettuce because darker colors in leafy vegetables are often signs of antioxidants that are thought to have a variety of health benefits.

The researchers said the dark red tinges on a leaf of red leaf lettuce are created when the sun's ultraviolet rays strike the plant and the plant creates UV-absorbing polyphenolic compounds to help block the ultraviolet radiation that can mutate plant DNA.

To create red leaf lettuce plants enriched with such compounds, Britz purchased low-power LEDs that shine with UVB light, a component of natural sunlight. Britz said he exposed the plants to approximately 10 milliwatts of UVB light per square meter.

After 43 hours of exposure the growing lettuce plants were noticeably redder than other plants that only saw white light.

We've been pleasantly surprised to see how effective the LEDs are, and are now testing how much exposure is required, and whether the light should be pulsed or continuous, said Britz.

The scientists will present their research June 2 in Baltimore during the Lasers and Electro Optics/International Quantum Electronics Conference.