The use of red species for urban “greening” in the age of climate change

The red/purple colour of some plant species is due to the presence of anthocyanins, a colourful class of flavonoids widely spread in the Plantae kingdom. Beside a doubtless aesthetic value of anthocyanin-rich species, the presence of these pigments confers them peculiar physiological and biochemical properties which make red species usually more tolerant to some environmental stresses, as occur in Mediterranean area. The ability of anthocyanins to partially absorb a proportion of light striking the mesophyll (mainly green and yellow wavebands) represents a useful feature against a condition of excessive light which not only occurs when plants are subjected to high irradiances, but also when other stressors (e.g., high temperature, low water availability) impair the photosynthetic process. The work elucidates as the presence of anthocyanins determines morpho-anatomical, biochemical and physiological effects. In particular, the roles of these pigments are described comparing the leaf ontogenesis of two genotypes of Prunus cerasifera, one with red (var. Pissardii) and one with green leaves (clone 29C). Red-leafed Prunus resulted better protected, especially during the leaf senescence. The presence of anthocyanins also promotes a delayed leaf senescence (4-week-longer leaf lifespan) which is a well-appreciated feature in the context of urban “greening”.