UV-B Exposure of Black Carrot (Daucus carota ssp. sativus var. atrorubens) Plants Promotes Growth, Accumulation of Anthocyanin, and Phenolic Compounds

Abstract

Black carrot (Daucus carota L. ssp. sativus var. atroburens) is a root vegetable with anthocyanins as major phenolic compounds. The accumulation of phenolic compounds is a common response to UV-B exposure, acting as protective compounds and as antioxidants. In the present study, black carrot plants grown under a 12-h photoperiod were supplemented with UV-B radiation (21.6 kj m−2 day−1) during the last two weeks of growth. Carrot taproots and tops were harvested separately, and the effect of the UV-B irradiance was evaluated in terms of size (biomass and length), total monomeric anthocyanin content (TMC), total phenolic content (TPC), and phytohormones levels. The results showed that UV-B irradiance promoted plant growth, as shown by the elevated root (30%) and top (24%) biomass, the increased TMC and TPC in the root (over 10%), and the increased TPC of the top (9%). A hormone analysis revealed that, in response to UV-B irradiance, the levels of abscisic acid (ABA), jasmonic acid (JA), and salicylic acid (SA) decreased in tops while the level of the cytokinins cis-zeatin (cZ) and trans-zeatinriboside (tZR) increased in roots, which correlated with an amplified growth and the accumulation of anthocyanins and phenolic compounds. Beyond the practical implications that this work may have, it contributes to the understanding of UV-B responses in black carrot.

Bioactive Compounds and Antioxidant Capacity in Anthocyanin-Rich Carrots: A Comparison between the Black Carrot and the Apulian Landrace “Polignano” Carrot

“…Our results for the BC on a dry weight basis (13.84 mg. g −1 DW) were consistent with those reported by Kammerer et al [ 8 ] (maximum 17 mg. g −1 DW) but not with those obtained by Mizgier et al [ 29 ], who reported an exceptional total anthocyanin content (154 mg. g −1 DW). Other authors [ 32 , 33 , 34 ] reported different values than those we observed, but different analytical procedures were used (spectrophotometric analysis).…”

“…Additionally, the antioxidant capacity (measured by mean of TEAC and ORAC assays) ranked BC as the highest (Table 2). The FCR values were in accordance with the literature for OC and BC [32,34,38,40]. In particular, the FCR value obtained for BC was very similar to the one reported for cv.…”

Effect of Partial Excision of Early Taproots on Growth and Components of Hydroponic Carrots

“…Enhancement of constituent compounds that foster human health will likely increase the value of crops. Regulation of light, temperature, and hormone treatments has been shown to increase phenol content in carrot taproots [13,39,40]. Therefore, by combining these environmental regulatory efforts, our early root excision method can be a useful tool for efficiently growing high-value carrots.…”

UV-B light and its application potential to reduce disease and pest incidence in crops

“…UV-B light has been shown to induce JA production in many plant species including mung bean, rice, maize, tobacco, broccoli, Antarctic pearlwort, and Arabidopsis (reviewed in Vanhaelewyn et al 46 ) 17 , 65 , 141 , 145 . However, it has also been suggested that UV-B light can reduce JA and JA-Ile levels in e.g., UV-B-resistant soybean genotypes and black carrot 146 , 147 . Both high and low UV-B radiation have been shown to induce JA biosynthesis and JA signaling genes (reviewed in Vanhaelewyn et al 46 , Jenkins 75 , and Ballaré 148 ) 50 , 65 .…”

“… + flavonol content: sinapyl, kaempferol, quercetin (UV-B vs. control; pulsed vs. continuous) + HY5, CHS, F3 ’ H (UV-B vs. control; partially pulsed vs. continuous) 36 Black Carrot – Day L Broadband TL40W/12 RS (Philips) 21.6 6 1 h n.a. + anthocyanin content (only in roots) + total phenolics content (Roots + top) − JA content (top), +/− roots − SA content (top), +/− roots 147 Arabidopsis – Day G Philips TL12 tubes + cellulose acetate filters 7.7; 12.7; 86.4 1.07; 1.77; 6 2 h, 4 h n.a. + changes in morphology, architecture + chlorophyll biosynthesis genes + specialized metabolites Stress induced only at the highest dose 30 Arabidopsis – Day Field + L Broadband TL40W/12 (Philips) +filters 6.3 7 15 min n.a.…”