Studies On Relationships Between Color Expression And Pigment Content In Color-changing Leaves Of Colorful Foliage Plants

Colorful foliage plants have unique seasonal characteristics,which are widely used in garden configuration design.In order to evaluate the ornamental value of color-leaf plants,the correlation between leaf color expression in color-leaf leaves was studied on the basis of the content of anthocyanin,chlorophyll and carotenoid.By measuring the change trend of pigment content and color parameters during the color conversion period of color-leaf plants,the accurate quantification of leaf color was carried out to reduce the subjective color cognitive error among individuals,and a method for rapid estimation of pigment content by leaf color was established,that provides a better choice for landscape configuration of colorful foliage plants.Taking the leaves of Photinia × fraseri Dress which in spring and summer color conversion period,and the Begonia semperflorens of ‘Super Olympia’(green leaf)as the object of study.To explor the correlation between color change and pigment content in leaf and the composition of pigment in color leaf,the correlation between each pigment and color was analyzed by statistical method,and the linear regression equation was fitted by mathematical model method.Finally the relationship between color parameter and color number content of color leaf was obtained.The content of anthocyanin in the leaves of Begonia semperflorens was determined by chemical separation and analysis for the first time,and the physiological changes of red pigment in the leaves of Begonia semperflorens were revealed at low temperature.The main research results are as follows:(1)At the turn of spring and summer,the new leaves of Photinia × fraseri Dress went through a process of changing from red to green.In the process of the color change of the new leaf,the significant change of the content of anthocyanin plays a very important role,but the pigment content and color parameters of the old leaves did not change significantly compared with the new leaves.The content of chlorophyll and carotenoid in all leaves increased significantly in spring,at the same time the content of anthocyanin decreased significantly.The color parameters were used to fit the content of anthocyanin in new leaves,and the correlation coefficient Rwas 0.999.The correlation coefficients of anthocyanin content,chlorophyll content and carotenoid content in the other ages leaves were also above 0.85.The results showed that the color of leaves could fully explain the pigment content in leaves of Photinia × fraseri Dress,and the change of pigment contents in leaves could be predicted by the change of color.(2)The change of leaves gradually turned bright red color of Begonia semperflorens was caused by the obvious change of anthocyanin content during the low temperature treatment.The change of color parameters was opposite to that of new leaves of Photinia × fraseri Dress in spring and summer,and the change of pigment content in leaves was also contrarily.The equations of anthocyanin content,chlorophyll content and carotenoid content were constructed by color parameters.The content of anthocyanin was significantly correlated with hue(a*),color ratio(H),hue angle(h)and color value(s),the fitting equation is y=-0.981+13.9H+0.037h+0.045a*-4.429 ×10-6s.The chlorophyll content was significantly correlated with hue(a*),hue angle(h)and color value(s),the fitting equation is y=-23.285+0.506a*+0.307h-3.033× 10-5s.The carotenoid content was significantly correlated with lightness(L*),hue(a*),hue(b*),saturation(C)and color value(s),the fitting equation is y=3.708-0.142L*+ 0.505b*-0.356C+0.507a*-1.38×10-4s.The correlation coefficients of these equations are all over 0.95.The color parameters of the leaves of Begonia semperflorens can truly explain the pigment content,and the change of the color parameters can also indicate the transformation of the pigment content.The variety of leaf color of Begonia semperflorens under low temperature stress was similar to that of color leaf plant in autumn and winter.Furthermore,it is suggested that a large number of colored foliage plants turn red in autumn and winter,which may be due to the decrease of ambient temperature.(3)In order to determine the main anthocyanin components in leaves of Begonia semperflorens induced by low temperature,a combination of high performance liquid chromatography(HPLC)and liquid chromatography tandem mass spectrometry(LC-MS/MS)was used to identify the components.The results showed that the anthocyanins in the leaves of the Begonia semperflorens were Cyanidin-3-Ogalactoside,Cyanidin-3-O-glucoside,Pelargonidin-3-O-glucoside and Delphinidin-3-O-glucoside.Among them,Cyanidin-3-O-galactoside and Cyanidin-3-O-glucoside,were the main red substances in the leaves of Begonia semperflorens at low temperature.Above all,there was a significant correlation between color parameters and pigment content in leaves of Photinia × fraseri Dress after changing from red to green and low temperature stress from green to red in Begonia semperflorens hypoglauca.The color change of leaf can directly explain the law of the change of pigment content in leaf.All the equations can reflect the change process of pigment content,which can provide inspiration for the determination of pigment content of other color-leaf plants,and give full play to the ornamental advantage of leaf color of color-leaf plants.The redness of the leaves of colored-leaf plants is closely related to the content of anthocyanin.Understanding the changes of the anthocyanins contents can provide the basis for the regulation and control the leaves color of the colored-leaf plants,and then increasing the ornamental time of the colored-leaf plants.