キクの花色に関する研究 (第3報)

Abstract

1. To understand the quantitative effect of major pigments on flower color variation in chrysanthemum cultivars (Chrysanthemum morifolium), carotenoid and anthocyanin pigments were extracted from the flowers and analyzed both qualitatively and quantitatively.The flower color was also measured with a color difference meter (Model; NDK- 5, Nihondenshoku kogyo) and recorded with L, a, and b values to indicate individual colors. In this study, 68 cultivars were classified into four groups according to the following petal colors: group (1), white; group (2), pink (pink to red-purple); group (3), yellow, and group (4), (i) orange and (ii) red.The relationship between flower color and kinds or content of pigments in these groups was discussed. Also, the results were compared with data obtained from absorption spectra of intact, fresh petals. The detailed results are described below.2. In qualitative analysis by thin layer chromatography, three major spots of anthocyanins were detected in 49 cultivars, all of which showed the same qualitative distribution pattern of anthocyanins, and ten major spots of carotenoids were noticed in 26 cultivars, which also showed the same qualitative pattern.3. Carotenoids were responsible for flower colors of the yellow, the orange and the red groups, and the number of cultivars with high carotenoid content were greater in the red group than in the yellow and the orange groups.On the other hand, anthocyanins were considered to be responsible for the flower color expression of the pink, the orange and the red groups, and the number of cultivars containing large quantities of anthocyanins were greater in the pink, especially red-purple cultivars, and the red groups than in the orange group.4. The content of carotenoids was sufficient, even in low concentration, to reveal a yellowish tone in the yellow, the orange and the red groups, but in the case of anthocyanins, a high concentration was necessary to reveal a pinkish tone in the pink group and reddish tone in the orange and the red groups.5. A method of evaluating the flower color according to the UCS system (Uniform Chromaticity Scale system) made it possible to distinguish slight color differences among the 68 cultivars of chrysanthemum. The classification of flower color by this method coincided with that of the previous experiment, in which the same 68 cultivars were used and the flower colors were derived into four groups according to the absorption curves of intact, fresh petals. Although the difference between deep red and deep red-purple flower colors, in both of which lightness (L) was very low, could be distinguished readily by visual judgement, those flower colors evaluated by UCS system assumed nearly the same position on Hunter′s diagram of chromaticity.6. Carotenoids had no influence on the lightness of flower color determined according to the UCS system, while anthocyanins had an influence on the lightness, which decreased as the content of anthocyanins increased in the pink, the orange and the red groups.7. Correlation was recognized between the content of carotenoids and a, b, or √ (chroma) values obtained in each flower color group. A similar relationship was found also between the content of anthocyanins and color values. The anthocyanins contributed not only to the shift of hue, but also to the shift of chroma, especially in the pink group. The carotenoids exerted a large contribution on the variation of chroma in the yellow, the orange and the red groups.Thus, the methods of spectrophotometric and color difference metric analysis of flower color are very useful to clarify the relationship between flower color variation and the kinds or content of pigments in petals.