UV‐B Resistance of Plants Grown in Natural Conditions

Abstract

Plants protect themselves against potentially harmful effects of solar ultraviolet‐B radiation by a variety of mechanisms conferring UV‐B resistance. The underlying resistance mechanisms of a plant can be acclimated corresponding to the prevailing UV‐B exposure in their habitat such that under natural conditions UV‐B damage does not seem to exist. UV‐B resistance is not only induced by UV‐B radiation but to a large extent also by other environmental factors. Here, we review current evidence on how abiotic variables, e.g. low temperature or water deficit, affect UV‐B resistance mechanisms. We are focusing on acclimation of UV‐B screening through the accumulation of UV absorbing compounds, which is well investigated, and on the removal of UV‐B‐induced DNA damage by repair. Although the latter is a resistance mechanism specifically directed to UV‐B‐induced damage, it is strongly underinvestigated. Interaction of UV‐B radiation and other environmental factors can occur at the level of signal transduction chains, most often leading to cross‐resistance. Additionally, the influence of environmental conditions on physiological reactions may lead either to cross‐resistance or cross‐sensitivity.

Rapid adjustment in epidermal UV sunscreen: Comparison of optical measurement techniques and response to changing solar UV radiation conditions

“…In the present experiment, the diurnal rhythm throughout the day verifies 50% changes of the flavonoid index within a few hours, which is enormously fast. Previously, changes up 18% in UV-absorbing compounds were described in relation to the ozon depletion (Pescheck & Bilger, 2020). It remains unclear if there is a delocalization or a modification of the compounds, for example, an oxidation or a degradation followed by a new synthesis.…”

Improvement of the Quality of Wild Rocket (Diplotaxis tenuifolia) with Respect to Health-Related Compounds by Enhanced Growth Irradiance

“…However, for flavonoids and carotenoids, a temperature dependence opposite to that observed here has been reported. Low temperature enhanced the formation of UV-screening compounds and flavonoids 51,52 and of V-cycle carotenoids. 53 On the other hand, high temperature (28 °C) has been reported to repress in Arabidopsis thaliana anthocyanin accumulation via the transcription factor HY5.…”

Solar UV‐B effects on composition and UV screening efficiency of foliar phenolics in Arabidopsis thaliana are augmented by temperature

“…Both groups of plants had similar amounts and composition of phenolic compounds throughout the study period. One explanation for this similarity could be cross-resistance induced by high PFDs from natural sunlight (reviewed in Pescheck & Bilger 2020). PFD is perceived by, among others, the blue light receptors CRYTOCHROME1/ CRYPTOCHROME2 (CRY1CRY2) and blue-light signalling can partly compensate for absent UVR8 signalling (Rai et al 2019).…”

“…Plants in their natural environment integrate signals from and simultaneously acclimatise to several environmental variables, such as varying temperature, PFD, and UV radiation. The effects of solar UV‐B radiation on phenylpropanoids are therefore completed or superimposed by other factors (reviewed in Pescheck & Bilger 2020). For example, mainly air temperature, and not daily UV‐B dose (or total PFD), controlled the absorbance of leaf extracts at 330 nm and the content of flavonoids in A. thaliana outdoors over the course of a year (Coffey & Jansen 2019; Pescheck & Bilger 2019).…”