Lettuce grown under ultraviolet light better for health

May 19th, 2009 - 1:47 pm ICT by IANS  

Washington, May 19 (IANS) A bunch of spinach packs in more nutritional wallop than a wedge of iceberg lettuce, because darker colours in leafy vegetables signify antioxidants that are thought to have a variety of health benefits. Now a team of plant physiologists has developed a way to make lettuce darker and redder and therefore healthier-using ultraviolet light-emitting diodes (LEDs).
The dark red tinges on a leaf of red leaf lettuce are the plant kingdom’s equivalent of suntan lotion. 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 belong to the same family that gives colour to berries and apple skin. They help block ultraviolet radiation, which can mutate plant DNA and damage the photosynthesis that allows a plant to make its food.

Diets rich in antioxidants provide a variety of health benefits to humans, from improving brain function to slowing the wear and tear of aging.

To create red leaf lettuce plants enriched with these compounds, Steven Britz of the US Department of Agriculture and colleagues, purchased low-power LEDs that shine with UVB (ultraviolet B) 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 10 milliwatts per square metre.

After 43 hours of exposure to UVB light, the growing lettuce plants were noticeably redder than other plants that only saw white light. Though the team has yet to quantify this effect, it appears to increase as the intensity of the light increases.

To cut transportation costs and feed the market in the wintertime, more produce is grown in greenhouses. Crops grown in the winter in northern climes receive very little UVB to begin with, and plants in greenhouses are further shielded from UVB by the glass walls.

Ultraviolet LEDs could provide a way to replace and enhance this part of the electromagnetic spectrum to produce darker, more colourful lettuces, said a release of Department of Agriculture.

Britz will be presenting the study at the Conference on Lasers and Electro Optics/International Quantum Electronics Conference (CLEO/IQEC), between May 31 and June 5 at the Baltimore Convention Centre.

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