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Proceedings Paper

Effect of supplemental ultraviolet radiation on the concentration of phytonutrients in green and red leaf lettuce (Lactuca sativa) cultivars
Author(s): Steven Britz; Charles Caldwell; Roman Mirecki; James Slusser; Wei Gao
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Paper Abstract

Eight cultivars each of red and green leaf lettuce were raised in a greenhouse with supplemental UV radiation, either UV-A (wavelengths greater than ca. 315 nm) or UV-A+UV-B (wavelengths greater than ca. 290 nm; 6.4 kJ m-2 daily biologically effective UV-B), or no supplemental UV (controls). Several phytonutrients were analyzed in leaf flours to identify lines with large differences in composition and response to UV-B. Red leaf lettuce had higher levels of phenolic acid esters, flavonols and anthocyanins than green lines. Both green and red lines exposed to UV-B for 9 days showed 2-3-fold increases in flavonoids compared to controls, but only 45% increases in phenolic acid esters, suggesting these compounds may be regulated by different mechanisms. There were large differences between cultivars in levels of phenolic compounds under control conditions and also large differences in UV-B effects. Among red varieties, cv. Galactic was notable for high levels of phenolics and a large response to UV-B. Among green varieties, cvs. Black-Seeded Simpson and Simpson Elite had large increases in phenolics with UV-B exposure. Photosynthetic pigments were also analyzed. Green leaf lettuce had high levels of pheophytin, a chlorophyll degradation product. Total chlorophylls (including pheophytin) were much lower in green compared to red varieties. Lutein, a carotenoid, was similar for green and red lines. Total chlorophylls and lutein increased 2-fold under supplemental UV-B in green lines but decreased slightly under UV-B in red lines. Lettuce appears to be a valuable crop to use to study phytochemical-environment interactions.

Paper Details

Date Published: 10 September 2005
PDF: 8 pages
Proc. SPIE 5886, Ultraviolet Ground- and Space-based Measurements, Models, and Effects V, 58860W (10 September 2005); doi: 10.1117/12.625576
Show Author Affiliations
Steven Britz, USDA Phytonutrients Lab. (United States)
Charles Caldwell, USDA Phytonutrients Lab. (United States)
Roman Mirecki, USDA Phytonutrients Lab. (United States)
James Slusser, Colorado State Univ. (United States)
Wei Gao, Colorado State Univ. (United States)

Published in SPIE Proceedings Vol. 5886:
Ultraviolet Ground- and Space-based Measurements, Models, and Effects V
Germar Bernhard; James R. Slusser; Jay R. Herman; Wei Gao, Editor(s)

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