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Coordination of anthocyanin decline and photosynthetic maturation in juvenile leaves of three deciduous tree species.

Juvenile leaves in high-light environments commonly appear red as a result of anthocyanin pigments, which play a photoprotective role during light-sensitive ontogenetic stages. The loss of anthocyanin during leaf development presumably corresponds to a decreased need for photoprotection, as photosynthetic maturation allows leaves to utilize higher light intensities. However, the relationship between photosynthetic development and anthocyanin decline has yet to be quantitatively described. In this study, anthocyanin concentration was measured against photopigment content, lamina thickness, anatomical development, and photosynthetic CO(2) exchange in developing leaves of three deciduous tree species. In all species, anthocyanin disappearance corresponded with development of c. 50% mature photopigment concentrations, c. 80% lamina thickness, and differentiation of the mesophyll into palisade and spongy layers. Photosynthetic gas exchange correlated positively with leaf thickness and chlorophyll content, and negatively with anthocyanin concentration. Species with more rapid photosynthetic maturation lost anthocyanin earliest in development. Chlorophyll a/b ratios increased with leaf age, and were lower than those of acyanic species, consistent with a shading effect of anthocyanin. These results suggest that anthocyanin reassimilation is linked closely with chloroplast and whole-leaf developmental processes, supporting the idea that anthocyanins protect tissues until light processing and carbon fixation have matured to balance energy capture with utilization.