Nondestructive measurement of carotenoids in plant tissues by fluorescence quenching

Carotenoids, compounds valuable for their antioxidant properties in humans and animals, are sometimes present in the bran layers of rice (Oryza sativa L.). We developed a nondestructive technique to screen individual rice kernels for the presence of carotenoids in their bran for genetic selection of the carotenoid-containing lines. Most plant tissues are highly autofluorescent. Carotenoids have a high absorptivity for visible light, which allows them to absorb or quench this natural fluorescence. Synchronous fluorescence spectroscopy provides the specificity and sensitivity that allows detection of the changes in fluorescence in a single rice kernel that occur when carotenoids are present. The fluorescence quenching technique identified three rice lines as having carotenoids present in the bran, and three other lines as being carotenoid-deficient. Fluorescence quenching was also used to monitor changes in carotenoid levels in living plants and enabled the measurement of carotenoids within the different colors of a variegated leaf.