Application of supplemental UV‐B radiation in pre‐harvest to enhance health‐promoting compounds accumulation in green and red lettuce

Abstract

The plants (green and red lettuce) were exposed to daily doses of UV‐B radiation for 1 hr for two weeks during growth. UV‐B‐treated green lettuces at the second week presented a greater content of quercetin than the control plants. Caffeoyltartaric acid, caffeoylquinic acid and caffeoylmalic acid also showed a significant accumulation in green lettuce after two weeks of UV‐B treatment in comparison to those non‐treated. Regarding carotenoid content, lutein, neoxanthin, and V + A + Z showed significant increased values after two weeks of UV‐B treatment in comparison to the non‐treated green lettuces. However, chlorophylls and carotenoids content did not present significant difference between the analyzed weeks for the red lettuces. In other words, quercetins, as well as caffeoyltartaric acid, caffeoylquinic acid and cyanidin glycoside of red lettuce showed a significant increase after UV‐B treatment at both weeks in comparison with control red lettuces. PRACTICAL APPLICATIONS: The impact of UV‐B on plants depends on the fluency rate, exposure time, wavelength of UV‐B radiation, and the amount of UV‐B relative to photosynthetic active radiation. Since carotenoids, chlorophylls, and flavonoid compounds can be increased by ecologically relevant levels of UV‐B in glasshouse production, this study was designed to verify whether supplemental UV‐B radiation was effective in increasing the concentration of health‐promoting compounds in green and red lettuce.