Abstract:In order to explore the physiological basis of the leaf color variation in Cymbidium hybrid, we used ‘Purple Element’ (K21) and its three new strains (K211,K212,K213) as materials to analyze the changes of leaf photosynthetic pigment content, chlorophyll synthesis precursor substance content, chlorophyll synthesisrelated enzyme activities and chlorophyll fluorescence parameter. Furthermore, their microstructure and ultrastructure were observed in this study. The results showed that: (1) the contents 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 K211 and K212 and PBG were abundant in the variegation leaves of K213. The maximum photochemical efficiency of photosystem Ⅱ (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 an inverse state. (2) 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 K213 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.