![]() UVC is very hazardous to organisms however, the stratospheric ozone layer filters out most of this UV radiation. UVB can cause a variety of damaging effects in plants and it represents approximately 1.5% of the total spectrum. UVA represents about 6% of the total solar radiation and is the least harmful part of UV radiation. UV radiation can be divided into three parts: UVA (320–400 nm), UVB (280–320 nm), and UVC (200–280 nm). Several studies have reported that UV radiation may trigger the phenylpropanoid metabolism in plant tissues. Likewise, previous reports have demonstrated that when wounding stress is applied in combination with other stresses such as exogenous phytohormones, hyperoxia, glyphosate and water-loss, the accumulation of phenolic compounds in carrots is affected. ![]() These changes in phenolic content are triggered by ROS and ethylene, which are signaling molecules that activate the phenylpropanoid pathway in wounded-plants. It has been previously reported that the phenolic content and antioxidant capacity (AOX) in carrots increases with wounding intensity. A reactive oxygen species (ROS) mediated hypothetical mechanism explaining the synergistic effect of wounding and different UV radiation stresses on phenolics accumulation in plants is herein proposed. In general, total phenolics correlated linearly with AOX for all treatments. Chlorogenic acid was induced by all UV radiations but mostly by UVB and UVC, ferulic acid was induced by all UV lights to comparable levels, while isocoumarin and 4,5-diCQA was induced mainly by UVB and UVC compared to UVA. The type of UV radiation affected phenolic profiles. The major phenolics were chlorogenic acid and its isomers, ferulic acid, and isocoumarin. Phenolics, AOX, and PAL activity also increased in cut carrots exposed to UVA or UVB. Carrot pies showed a higher increase compared to slices and shreds. Accordingly, phenolic content, AOX, and PAL activity increased in cut carrots with the duration of UVC radiation, whereas whole carrots showed no increase. Here, we determined the combined effect of wounding intensity and UV radiation on phenolic compounds, AOX, and the phenylalanine ammonia-lyase (PAL) activity of carrots. It was also reported that UV radiation may trigger the phenylpropanoid metabolism in plant tissues. Previously, we found that phenolic content and antioxidant capacity (AOX) in carrots increased with wounding intensity.
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