UV Light Boosts Lettuce Carotenoids

Ultraviolet light can boost levels of carotenoids in some types of green-leaf lettuce, according to an Agricultural Research Service (ARS) study.

In the field, plants express beneficial chemical compounds that are thought to be a means of protecting themselves from the effects of UV radiation. Plant physiologists Charles Caldwell and Steven Britz with the ARS Beltsville Human Nutrition Research Center in Beltsville, Md., examined the role of light exposure and cultivar selection on the relative content of several of these compounds. They studied eight green and eight red leaf lettuce varieties, each receiving either supplemental ultraviolet-A (UV-A) light, both UV-A and ultraviolet-B (UV-B) light, or no UV (receiving only regular light).

Supplemental UV-A plus UV-B greatly increased the carotenoid and chlorophyll concentrations of the green leaf lettuce varieties, while slightly but significantly reducing the levels of those compounds in the red varieties. Significantly higher levels of other phenolic phytochemicals were produced in the red leaf lettuce varieties, compared to the green leaf lettuce varieties under the same UV treatment conditions.