Changes in colour during leaf development of Eugenia uniflora (Myrtaceae): different strategies for integrity conservation of the photosynthetic apparatus

Abstract

Leaf development is affected by different amounts of light, leading to structural and physiological gradients. Young leaves are normally more sensitive to high light levels, which may trigger different strategies for light protection. On this basis, the objective of the current study was to determine strategies used by young (1st node, red), in transition (2nd node, starting to become green, and 4th node, almost all green) and mature (6th node, green) leaves of Eugenia uniflora L. (Myrtaceae) to deal with light. Young leaves showed less structural protection from light, which improved after the 2nd node. The reddish colour of young E. uniflora leaves is mainly due the greater production of photoprotective pigments, mainly anthocyanins, although the chlorophyll/carotenoid ratio showed some contribution by the carotenoids. Reactive oxygen species were homogeneously distributed in the young leaves, turning to malondialdehyde only in older leaves. The lower structural protection from light and physiological immaturity of young E. uniflora leaves lead to photoinhibition and reduced quantum yield during at times of highest light intensity of the day, causing lower efficiency in electron transport. The E. uniflora case clarifies the occurrence of different defence strategies against light exposure according to leaf developmental stages.