TITLE:
Supplemental UV-A and UV-B Affect the Nutritional Quality of Lettuce and Tomato: Health-Promoting Phytochemicals and Essential Nutrients
AUTHORS:
Myungjin Lee, Cary Rivard, Eleni Pliakoni, Weiqun Wang, C. B. Rajashekar
KEYWORDS:
Greenhouse, Lettuce, Micronutrients, Nutritional Quality, Phytochemicals, Spectral Quality, Tomato, UV-A and UV-B
JOURNAL NAME:
American Journal of Plant Sciences,
Vol.12 No.1,
January
28,
2021
ABSTRACT: UV radiation plays an important role not only in
plant growth and development but also in the
accumulation of essential nutrients and health-promoting phytochemicals
in plants. The main objective of this study was to examine the effects of
supplemental UV-A, UV-B, and UV-AB on the nutritional quality of lettuce (Lactuca sativa, cv. red leaf “New Red Fire” and green leaf “Two Star”) and tomato (Solanum lycopersicum L., cv. BHN-589) grown in a greenhouse. Supplemental UV radiation was
provided by UV lamps 5 - 6 days prior to harvest. Supplemental UV-A produced higher accumulation of total phenolic compounds
and higher antioxidant capacity in red leaf lettuce compared to other
treatments. Overall, supplemental UV-A produced a stronger response than other
UV treatments and control in the accumulation of many phenolic compounds
including luteolin-7-glucoside, quecetin-3-glucoside,
and apigenin-3-glucoside in red leaf lettuce. However, UV-B and UV-AB had a
negative response in the accumulation of many phenolic compounds including
chlorogenic acid, luteolin-7-glucoside, quercetin-3-glucoside, and
apigenin-3-glucoside in both red and green leaf lettuce varieties. In tomato
fruits, supplemental UV-A had no effect on
their total phenolic concentration. However, supplemental UV-B radiation for 3
h or UV-AB radiation for 9 h exposure produced higher total phenolic
concentration in the fruits compared to other supplemental UV treatments.
Supplemental UV-AB (3 hexposure) was
generally more effective than other UV treatments in increasing the
accumulation of a number of phenolic
compounds including chlorogenic acid, caffeic acid, chicoric acid, luteolin-7-glucoside, and other flavonoids in ripe
tomato fruits. Supplemental UV-A produced higher
accumulation of carotenoids including lutein and β-carotene than other supplemental UV treatments, while supplemental UV-AB
increased the accumulation of lycopene in fully ripe tomatoes. With regard to the essential nutrients, green
leaf lettuce was more responsive to the supplemental UV treatments than red
leaf lettuce. All the supplemental UV treatments produced an increase in
protein concentration in the leaves of green leaf lettuce. However,
supplemental UV-AB produced a stronger response compared to the control and
other UV treatments in increasing the accumulation of many nutrients including
protein, phosphorus, potassium, sulfur, and zinc in green leaf lettuce “Two Star”. Supplemental UV-treatments
did not affect the accumulation of any essential nutrients in fully ripe tomato
fruits. The results show that supplemental UV enhances the nutritional quality
of lettuce in relation to both
health-promoting phytochemicals and essential nutrients. Similarly,
supplemental UV enhances nutritional quality in tomato fruits with higher accumulation of both phenolic compounds
and carotenoids than does the control treatment.