Variation characteristics of color parameters and pigment content in bracts at different flowering stages among various cultivars of Bougainvillea spectabilis
[Objective]The research was conducted to explore the variation characteristics of color parameters and pigment content and the mechanism of color dilution of bracts at different flowering stages in Bougainvillea spectabilis cultivars with different flower colors.[Method]Five varieties of B.spectabilis with obvious degree of bracts color dilution in orange and pink series were used as materials.The color parameters of bracts at bud stage(S1),fully blooming stage(S2)and final flowering stage(S3)were measured using the Royal Horticultural Society Colour Chart(RHSCC)of the United Kingdom and color difference instrument.The pigment content of bracts during flowering was determined by spectrophotometer,and the correlation between the color parameters and the pigment content of bracts was analyzed.[Result]During the flowering process,the bract color of five varieties of B.spectabilis showed varying degrees of dilution.Among them,orange varieties'Chameleon'and'Golden Glow'had relatively large degree of dilution of the bract color,while pink varieties'China Beauty','Jinbian Chongfen'and'Blonde Girl'had a relatively small degree of dilution of the bract color.The results of quantitative analysis showed that the total flavonoid content in the bracts of'Chameleon'was higher than that of sugar beet pigment during the flowering process,and the pigment content in the bracts of the other four varieties was in the order of sugar beet pigment,total flavonoids,chlorophyll and carotenoid from high to low.The correlation analysis between the color parameters and the pigment content of bracts showed that the sugar beet pigment was the main pigment that affected the color change of the bracts of B.spectabilis,and the influence of betacyanin was the largest.Total flavonoids and betaxanthin were the main pigments that affect the color fading of the bracts of orange B.spectabilis,while betacyanin and total flavonoids were the main pigments that affect the color fading of the bracts of pink B.spectabilis.[Conclusion]There are certain differences in the color changes of bracts during the flowering process of different varieties of B.spectabilis.There is a certain correlation between the color parameters and the pigment content of B.spectabilis bracts.The changes in the pigment composition of the bracts are the key factors affecting the color and fading of B.spectabilis bracts.
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