Irradiation of UV-B Induces Biosynthesis of Anthocyanins in Flower Petals of Rose, Rosa hybrida cv. ‘Charleston’ and ‘Ehigasa’

The ultraviolet-B radiation (UV-B: 280 to 320 nm) promotes the accumulation of the anthocyanins in rose plants. Open flowers of Rosa hybrida cultivars ‘Charleston’ and‘Ehigasa’ undergo a striking color change from yellow to red over 10-12 days under natural daylight due to the accumulation of the anthocyanins in the petals. The anthocyanin present in the rose petals was identified as cyanidin 3-glucoside (chrysanthemin) and cyanidin 3, 5-diglucoside (cyanin) by using paper chromatography, partial acid hydrolysis, and HPLC. To determine the role of UV-B in the anthocyanin biosynthesis pathway, rose plants were grown under different light conditions supplemented with or without UV-B. Anthocyanin accumulation was suppressed in the treatment without UV-B and the accumulation started following to exposure to UV-B by a gradual increase of cyanin, followed by a dramatically increase of chrysanthemin. Furthermore, it revealed that the unfolding flower stage 3 to 4 (about 50% anthesis) was critical for anthocyanin biosynthesis in rose.