On the red colour of raspberry (Rubus idaeus)

Anthocyanins are the ubiquitous water-soluble pigments that are found in flowers and fruits, and are responsible for their impressive red and blue colours. Many examples of the strategies used by nature to obtain colour in plants are based on co-pigmentation, a phenomenon that stabilises and intensifies colours at pH values where the anthocyanin pigment alone is colourless. Several examples of these strategies were described in the last few years, in particular the structures responsible for colour in Commelina comunnis and Ipomoea tricolor. Here we show an alternative to co-pigmentation, used by nature in the colouring of raspberry (Rubus idaeus). This strategy does not involve co-pigmentation.