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.

Supplemental UV-B Exposure Influences the Biomass and the Content of Bioactive Compounds in Linum usitatissimum L. Sprouts and Microgreens

“…However, many manuscripts have investigated UV-B-induced effects in several crops, mostly agreeing on the general positive impact of UV-B irradiation on the total phenolic content [16]. In accordance with our results, a pre-harvest UV-B supplementation increased the total phenolic and flavonoid concentration in basil [70,71] and lettuce [72]. UV-B was also effective in enhancing phenolic and flavonoid content, depending on the UV-B dose applied, when exposing plants soon after germination, as observed in rice and wheat seedlings [73,74], and in mung bean and broccoli sprouts [17,18].…”

Regulation of carotenoid and flavonoid biosynthetic pathways in Lactuca sativa var capitate L. in protected cultivation

“…Thus, the UV-shielding flavonoids are mainly found in the plant epidermis and act as UV protectants – a plant’s sunscreen. Studies have reported that flavonoid contents increase in lettuce grown with additional UVA, UVB and UVC light ( Lee et al., 2014 ; Assumpção et al., 2019 ).Using covered systems for crop cultivation, changes in UV light occur due to the reduced transmittance of the materials used. Indeed, UVA and UVB light are reduced by using polytunnels in this study, resulting in lower total and individual flavonoids than seen in cultivation without polytunnels.…”

Anything New under the Sun? An Update on Modulation of Bioactive Compounds by Different Wavelengths in Agricultural Plants

“…The content of the anthocyanin cyanidin-3-malonylglucoside, present only in red lettuce, also accumulated at higher levels after both one and two weeks of UV-B treatment. However, caffeoylmalic acid was negatively affected by both UV-B doses [ 209 ].…”