The Changing Distribution of Anthocyanin in Mikania micrantha Leaves as an Adaption to Low-Temperature Environments

Anthocyanins, a protective substance in plant leaves, can accumulate in large quantities under low-temperature induction. In order to explore the effect of anthocyanins in Mikania micrantha leaves, the Rubisco, photosynthesis, pigments, and antioxidative capacity in mature leaves (ML) and young leaves (YL) of M. micrantha were investigated in winter. YL were red on both the adaxial and abaxial surfaces, while ML was red on the abaxial surfaces and green on the adaxial surfaces. Compared with ML, the relative expression of the genes related to anthocyanin synthesis and anthocyanin content were significantly higher in YL. Antioxidants such as flavonoids and total phenols were found in higher quantities, and the total antioxidant capacity was also significantly higher in YL. However, in ML, the Rubisco and chlorophyll content related to photosynthesis were significantly higher. The stomata of ML displayed a larger aperture than YL, and the stomatal conductance and photosynthetic rate were significantly higher in ML. The results suggested that M. micrantha leaves could better adapt to the winter environment through changing the distribution of anthocyanins in leaves of different maturity.