The influence of ultraviolet radiation on growth, photosynthesis and phenolic levels of green and red lettuce: potential for exploiting effects of ultraviolet radiation in a production system

Abstract

Studies have shown that natural ultraviolet (UV) radiation increases secondary products such as phenolics but can significantly inhibit biomass accumulation in lettuce plants. In the work presented here, the effect of UV radiation on phenolic concentration and biomass accumulation was assessed in relation to photosynthetic performance in red and green lettuce types. Lettuce plants in polythene clad tunnels were exposed to either ambient (UV transparent film) or UV‐free conditions (UV blocking film). The study tested whether growth reduction in lettuce plants exposed to natural UV radiation is because of inhibition of photosynthesis by direct damage to the photosynthetic apparatus or by internal shading by anthocyanins. Ambient levels of UV radiation did not limit the efficiency of photosynthesis suggesting that phenolic compounds may effectively protect the photosynthetic apparatus. Growth inhibition does, however, occur in red lettuce and could be explained by the high metabolic cost of phenolic compounds for UV protection. From a commercial perspective, UV transparent and UV blocking films offer opportunities because, in combination, they could increase plant quality as well as productivity. Growing plants continuously under a UV blocking film, and then 6 days before the final harvest transferring them to a UV transparent film, showed that high yields and high phytochemical content can be achieved complementarily.

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

“…Tsormpatsidis, Henbest, Battey, and Hadley (), studying lettuce plants in polyethylene clad tunnels exposed to either ambient or UV‐free conditions, reported high yields and high phytochemical content if the plants are exposed to UV before the harvest.…”

Non-destructive Phenotyping of Lettuce Plants in Early Stages of Development with Optical Sensors

“…While anthocyanin production in the red oak cultivar was negatively correlated with increasing temperature, the correlation was positive in the two Batavia cultivars (Marin et al, 2015). Nevertheless, it is problematic to compare results of temperature treatments from diverse studies, because several factors, including radiation (Tsormpatsidis et al, 2008, 2010; Marin et al, 2015), relative humidity (Marin et al, 2015), water availability (Rajabbeigi et al, 2013), light source (Park et al, 2012), CO 2 availability (Park et al, 2012), and plant growth stage (Becker et al, 2014b) affect biosynthesis of anthocyanin in lettuce either directly or in interaction. It is possible, that supra-optimal temperature (HOT) in our experiments caused a drought stress, despite regular watering.…”

Light signaling and plant responses to blue and UV radiations—Perspectives for applications in horticulture

“…Nevertheless, UV-B exposure does not induce accumulation of flavonoids in pepper (Hoffmann et al, 2015), and even strongly decreases (À27%) flavonoid content in Alnus incana (Kotilainen et al, 2008) (Table 2). Accumulation of anthocyanins is promoted by supplementation with UV-A or UV-B or blue wavelengths (Carvalho and Folta, 2014;Kubota, 2009Tsormpatsidis et al, 2008;Tsormpatsidis et al, 2010), even when UV-B irradiation is only applied over a short period (6 days) before harvest to avoid a depressive effect of UV-B on growth (Tsormpatsidis et al, 2010).…”