Abstract:In order to clarify the pigment composition and color mechanism of petals of Melastoma, the anthocyanins in 5 species were determined, the structure and distribution of petal epidermal cells were observed, and the influence of pH value, soluble sugar and soluble protein content on flower color was analyzed. The results showed that the petals of Melastoma had not chlorophyll and carotenoid, violet color mainly contained anthocyanin and flavonoids, and flavonoids in white color. The anthocyanins distributed in upper and lower epidermis of M. candidum and M. sanguinrum petals, and aslo in palisade tissue of M. malabathiricum, but the petals of M. candidum f. albiflorum and M. malabathricum var. alba had no pigment accumulation. The cells in upper epidermis of violet Melastoma show conical protrusions, which in white Melastoma show irregular flat shape, and those in lower epidermis of both colors show irregular flat shape. The brightness (L*) of flower color decreased with the deepening of petal color, which was negatively correlated with the redness (a*) and positively with the blueness (b*). The anthocyanin content had significantly negative correlation with L* and b*, and as well as pH and a*. Therefore, anthocyanin was the main determinant of flower color in genus Melastoma, anthocyanin content, pigment distribution and shape of upper epidermis cells were the main factors that cause color diversity.