ANTHOCYANINS IN MODERN ROSES - CHEMICAL AND COLORIMETRIC FEATURES IN RELATION TO THE COLOR RANGE

With respect to intravarietal variability, the petals of 15 rose (Rosa x hybrida) varieties, representative of the colour range expressed by modem roses primarily pigmented with anthocyanins, were investigated from chemical and colorimetric viewpoints. Depending on the variety, the observed colour variations were based on a more or less complex mixture of cyanidin 3,5-diglucoside, pelargonidin 3,5-diglucoside, quercetin and kaempferol glycosides. The total anthocyanin content ranged from 4 to 109 mg g-1 petal dry wt., while the total amount of flavonol glycosides was never less than 8 mg g-1 and could reach 136 mg g-1 petal dry wt. Between cultivars, the pH of the petal outer epidermis varied from 3.6 to 5.4 units. Using a spectrocolorimeter, the petal colour of each variety was measured. In order to allow quantitative comparisons of colours, the reflectance curves were further translated into indices calculated using the CIELab system. In the aggregate, there were good correlations between chemical parameters and colorimetric indices that are lightness (L*), chroma (C*) and hue angle (h). Both of these criteria (chemical and colorimetric) appeared sufficient to explain the visual sense of the petal colour.