Coordinated changes in anthocyanins and cuticular wax during leaf color transition in Rosa chinensis

Juvenile leaves exhibit a red coloration due to the presence of anthocyanins, which assist plants resist various environmental stresses. This characteristic is common and visually striking among many woody species across various higher plant families. However, the mechanisms underlying leaf color change during development and the defense mechanisms of mature leaves remain unclear. In this study, we analyzed the mechanism of color transition from red to green in Chinese Rose (Rosa chinensis) leaves and the development of cuticular wax in their natural state. The results show that anthocyanins and cuticular waxes are deposited at different stages of leaf development. During the red and young stage, anthocyanins are abundant in both the adaxial and abaxial epidermal cells of the leaves, while no cuticular wax is observed. As the leaves develop, the content of anthocyanins gradually decreases, leading the leaves to turn green. Anthocyanins first disappear from the adaxial epidermis, while the accumulation of cuticular wax begins at this stage. By the time the leaves are fully differentiated and green, anthocyanins have completely disappeared, and cuticular wax is deposited on both the adaxial and abaxial epidermis. The anthocyanins accumulated in the epidermal cells are primarily cyanidin, which is present in significantly higher content during the early stages of development compared to the later stages. Using gas chromatography-mass spectrometry (GC-MS) to determine the composition and content of leaf waxes, we found that alkanes and esters are the most prominent components present in the leaves. The content of waxes increases significantly in the later stages of development. In summary, our results indicate that anthocyanins and cuticular wax display a sequential developmental pattern on the leaves of Rosa chinensis under natural conditions.