Abstract:In order to explore the physiological basis of the leaf color variation in Cymbidium hybrid, ‘Purple Element’ (K21) and its three new strains were used as materials to analyze the changes of leaf photosynthetic pigment content, chlorophyll synthesis precursor substance content, chlorophyll synthesis-related enzyme activity and chlorophyll fluorescence parameter. Furthermore, their microstructure and ultrastructure were observed in this study. The results showed that the content of chlorophyll a, chlorophyll b, carotenoid in the variegation leaves of three different strains were significantly lower than those in the corresponding green leaves. Compared with the corresponding green leaves, UrogenⅢ were accumulated in the variegation leaves of K21-1 and K21-2 and PBG were abundant in the variegation leaves of K21-3. The maximum photochemical efficiency of photosystemⅡ(Fv/Fm) and the actual photochemical efficiency [Y(Ⅱ)] in the variegation leaves of three different strains were significantly lower than those in the green leaves, while their photochemical quenching coefficient(qP)exhibited a inverse state. In the comparison of the microstructure and the chloroplast ultrastructure, the cells in the variegation leaves contained less chloroplasts than that in the green leaves, meanwhile, the mature degree of chloroplast in the variegation leaves was lower, even K21-3 presented a cavity structure. It is speculated that the inhibition of chlorophyll precursor synthesis, the underdevelopment of chloroplast structure and the decrease of chlorophyll content are the reasons for the formation of the leaf art in three new strains. This study preliminarily explained the possible reasons for the formation of the leaf art from the physiological and cellular level, which laid a theoretical foundation for further research on related molecular mechanisms and rational utilization of germplasm resources.