Study On The Mechanism Of Flower Color Change During The Flowering Period Of Four Colored Chrysanthemums

Chrysanthemum（Chrysanthemum morifolium）with a rich variety of flower color,is one of the most beautiful and popular cultivated flowers in the world.In this study,the pigment species and content,upper epidermal cell morphology size,metal ion content,cytosol pH,pigment synthesis and pH-related gene expression in the ray florets at each stage of the opening process were determined to reveal the influence of major internal factors on chrysanthemum flower color development during the flowering stage,and the results of the study were as follows:1.The pigment content in the ray florets of the four colors of chrysanthemums changes significantly with the opening process:the total anthocyanins content in red and yellow chrysanthemums changed significantly,the total anthocyanins in red chrysanthemums showed a gradual downward trend,while the yellow chrysanthemums showed a trend of first rising and then declining.The anthocyanin content in pink and white chrysanthemums did not change significantly with petal aging,and the difference was not significant.The carotenoid content in the ray florets of red and yellow chrysanthemums showed a tendency to increase first and then decrease with the opening stage,and the carotenoid content was higher than that of white and pink chrysanthemums.The flavonoid content in the ray florets of yellow chrysanthemums varied obviously with the opening process.2.Chrysanthemum flower color is closely related to the cytosol pH of petals:the cytosol pH of chrysanthemum petals in four colors chrysanthemums was higher in the early stage of opening,and the range was between about 5.4 and 6.4.As flower opening the cytosol pH decreased.The cytosol pH of the petals of red and yellow chrysanthemums varied greatly.3.The morphological size of upper epidermal cells on the ray florets have a certain impact on the color development of chrysanthemum ray florets:as the flowers opening,the area of upper epidermal cells gradually increased,the cell shape changed irregularly,and the morphological changes of epidermal cells on different flower colors of chrysanthemum ray florets were also different.4.Different metal ion changes have different effects:the content of Na⁺between plants at the flowering stage was the largest,Fe³⁺and Mg²⁺were more important for the coloration of red and pink chrysanthemums,and Fe³⁺was necessary for the formation of yellow in the late flowering period.5.The expression of anthocyanin synthesis and cytosol pH-related genes has changed significantly:it can be seen that genes related to anthocyanin synthesis such as Cm ANS and Cm DFR were highly expressed in the flowering process of different colors of chrysanthemums.The expression of six genes was higher in the petals of darker colored chrysanthemums.The expression of pH-related genes in the cytosol was different,but the trend was about the same,with the highest expression in the second or fourth stage.This study revealed that during the opening process of chrysanthemums,different internal influencing factors had different degrees of influence on the formation of ray florets of different colors of chrysanthemums.Exploring the relationship between the influencing factors and flower color of chrysanthemum ray florets can lay a foundation for the use of molecular means to regulate chrysanthemum flower color,in order to provide a theoretical basis for chrysanthemum molecular breeding.