Ultraviolet LEDs have been employed by a team of American plant physiologists to create lettuce that is darker, redder and more nutritious.
Darker colours in leafy vegetables are usually a sign of the presence of antioxidants, which are thought to have a variety of health-giving properties.
Steven Britz of the US department of agriculture and his colleagues used low-power UV LEDs to stimulate the growth of powerful antioxidant polyphenolic compounds in lettuce leaves, giving them a dark red colour.
"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," commented Mr Britz.
It is thought UV LEDs could be used to provide a way to enhance winter crops grown in areas which receive little UVB light and also as a method of preserving the nutrients in vegetables which have already been harvested.
The findings will be presented at this year's CLEO/IQEC conference in Baltimore, due to be held next month, at which research on the world's first laser TV and other emerging technologies in the optoelectronics industry will be showcased.