Plants grown with LEDs

Plant physiologists from the USDA have developed a way to use UV LEDs to make lettuce darker and redder, and therefore healthier.

Steven Britz, a plant physiologist from the US Department of Agriculture (USDA), and colleagues have developed a way to make lettuce darker and redder – and therefore healthier with more antioxidants – using ultraviolet LEDs, according to an article posted on the Laser Focus World magazine website.

The research will be presented at the 2009 Conference on Lasers and Electro Optics/International Quantum Electronics Conference (CLEO/IQEC), which takes place May 31 to June 5 in Baltimore, Maryland.

When bombarded with ultraviolet rays from the sun, the lettuce leaf creates UV-absorbing polyphenolic compounds in its outer layer of cells. Some of these compounds are red, and help block UV radiation, which can mutate plant DNA and damage the photosynthesis that allows a plant to make its food.

To create red leaf lettuce plants enriched with these antioxidant compounds, Britz purchased low-power LEDs that shine with UVB light, a component of natural sunlight. In small quantities, this ultraviolet light allows humans to produce vitamin D, which has been cited for its health benefits.

Britz exposed the plants to levels of UVB light comparable to those that a beach goer would feel on a sunny day, approximately 10mW/sq.m. After 43 hours of exposure to UVB light, the growing lettuce plants were noticeably redder than other plants that only saw white light.