Effect of UV Radiation and Salt Stress on the Accumulation of Economically Relevant Secondary Metabolites in Bell Pepper Plants

Abstract

The green biomass of horticultural plants contains valuable secondary metabolites (SM), which can potentially be extracted and sold. When exposed to stress, plants accumulate higher amounts of these SMs, making the extraction and commercialization even more attractive. We evaluated the potential for accumulating the flavones cynaroside and graveobioside A in leaves of two bell pepper cultivars (Mavras and Stayer) when exposed to salt stress (100 mM NaCl), UVA/B excitation (UVA 4–5 W/m2; UVB 10–14 W/m2 for 3 h per day), or a combination of both stressors. Plant age during the trials was 32–48 days. HPLC analyses proved the enhanced accumulation of both metabolites under stress conditions. Cynaroside accumulation is effectively triggered by high-UV stress, whereas graveobioside A contents increase under salt stress. Highest contents of secondary metabolites were observed in plants exposed to combined stress. Effects of stress on overall plant performance differed significantly between treatments, with least negative impact on above ground biomass found for high-UV stressed plants. The usage of two non-destructive instruments (Dualex and Multiplex) allowed us to gain insights into the ontogenetical effects at the leaf level and temporal development of SM contents. Indices provided by those devices correlate fairly with amounts detected via HPLC (Cynaroside: r2 = 0.46–0.66; Graveobioside A: r2 = 0.51–0.71). The concentrations of both metabolites tend to decrease at leaf level during the ontogenetical development even under stress conditions. High-UV stress should be considered as a tool for enriching plant leaves with valuable SM. Effects on the performance of plants throughout a complete production cycle should be evaluated in future trials. All data is available online.

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

“…This acclimation response has been reported for many different plant species and is driven by UV-B, UV-A, PAR (Latouche et al, 2013;Nybakken et al, 2004;Pollastrini et al, 2011;Rechner et al, 2016;Wang et al, 2020). The adjustments in UV-absorbing compounds in okra began within one day and lasted for 3 days of UV exposure (Figure S1) as previously shown in other species (e.g., grapevine, lettuce, barley, kale, Arabidopsis, common privet) (Agati et al, 2011;Barnes et al, 2013Barnes et al, , 2015Ellenberger et al, 2020;Kolb et al, 2005;Neugart et al, 2014). In grapevine, it was further shown that plants transferred to outdoor environments can increase flavonoids 10-fold over the course of 10 days (Latouche et al, 2013).…”

Comparative Effects of Different Light Sources on the Production of Key Secondary Metabolites in Plants In Vitro Cultures

“…Cynaroside also reduces kidney damage caused by the chemotherapeutic drug cisplatin, which is used to treat cancer [45]. The production of cynaroside has been increased in in vitro culture of Capsicum annum (aka bell pepper plant) by elicitation of UVA/B light for a period of 16 days [30].…”

Natural Variation among Arabidopsis Accessions in the Regulation of Flavonoid Metabolism and Stress Gene Expression by Combined UV Radiation and Cold

“…In the case of mild stresses, pretreatment with drought or UV-B may enhance subsequent tolerance to the other stress treatment. Conversely, combined salt and UV-A + B stress resulted in slightly lower fresh and dry weight of bell pepper plants than either of the single stresses ( Ellenberger et al 2020 ), while in poplar DNA lesions due to UV-B radiation were reduced when plants were simultaneously salt stressed ( Ma et al 2016 ). However, no detailed transcript and metabolite analyses have been published under such conditions.…”