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ARS Home » Southeast Area » Stuttgart, Arkansas » Dale Bumpers National Rice Research Center » Research » Publications at this Location » Publication #166332
Title: NON-DESTRUCTIVE MEASUREMENT OF CAROTENOIDS IN PLANT TISSUE BY FLUORESCENCE QUENCHING

Author
item MILLER, HELEN
item MILLER, GORDON
item RUTGER, J

Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/30/2005
Publication Date: 9/30/2005
Citation: Miller, H.B., Miller, G.H., Rutger, J.N. 2005. Non-destructive measurement of carotenoids in plant tissue by fluorescence quenching. Crop Science. 45:1786-1789.

Interpretive Summary: Rice kernels, as well as most other plant tissues will fluoresce when they are illuminated with the right color of light. Carotenoids, nutritive pigments responsible for color in carrots, watermelon, etc., are very effective at absorbing light. We used synchronous fluorescence spectroscopy to measure the absorption by carotenoids of the fluorescent light in plant tissues. The technique is valuable because it doesn't destroy the plant material. Also the technique only needs a very small sample - a single rice kernel will suffice. If bran, an outer layer of rice, is not milled off to make white rice, you have "brown" rice. The carotenoids in bran were measured by fluorescence spectroscopy and confirmed by a standard technique for measuring carotenoids. Fluorescence quenching was also used to see changes in carotenoid levels in living plants. The sensitivity of the technique also enabled the measurement of carotenoids within the different colors of a variegated leaf.

Technical Abstract: Rice (Oryza sativa L.) endosperm, and most other plant tissues, are highly autofluorescent, and carotenoids have a high absorptivity which allows them to quench this natural fluorescence. Synchronous fluorescence spectroscopy provides the specificity and sensitivity needed to detect the changes in fluorescence in a single rice kernel that occur when carotenoids are present. The spectrum from 505 nm to 565 nm was integrated from a synchronous scan using a wavelength difference of 10 nm. Rice bran has the potential for being a nutritious food source. Genetic selection minimizing anti-nutritional factors for improved brown (unmilled) rice can be coupled with selection for the anti-oxidant benefits of carotenoids. The fluorescence quenching technique allowed us to non-destructively screen single kernels of brown rice. The bran of two red rices (LA3 and AR-StgS) were determined to have consistently high levels of carotenoids. These results were confirmed by standard extraction of carotenoids from the bran. Fluorescence quenching was also used to monitor changes in carotenoid levels in living plants. The sensitivity of the technique enabled the measurement of carotenoids in thin tissue layers and within the different colors of a variegated leaf.