Why are young leaves red?

• Published in: Oikos Vol. 98; no. 1; pp. 163 - 176
• Main Authors: Dominy, N.J. (Chicago Univ., Ill. (USA)), Lucas, P.W, Ramsden, L.W, Riba-Hernandez, P, Stoner, K.E, Turner, I.M
• Format: Journal Article
• Language: English
• Published: Copenhagen Munksgaard International Publishers 01.07.2002; Blackwell Publishers; Blackwell
• Subjects: Animal and plant ecology; Animal, plant and microbial ecology; Autoecology; Biological and medical sciences; BOSQUE TROPICAL; COLOR; Colors; COLOUR; COSTA RICA; COULEUR; ESPECE; ESPECIES; FEUILLE; Forest canopy; Forest regeneration; FORET TROPICALE; Forum; Fundamental and applied biological sciences. Psychology; Greening; Herbivores; HOJAS; LEAVES; MEXICO; MEXIQUE; PANAMA; Plants; Plants and fungi; Receptors; SINGAPORE; SINGAPOUR; SINGAPUR; SPECIES; TROPICAL FORESTS; Understory; Anthocyanin; Microorganism resistance; Animal plant relation; Pest resistance; Biosynthesis; Plant leaf; Tropical forest; Developmental stage; Photoprotection; Adaptation; Coloration
• ISSN: 0030-1299; 1600-0706
• DOI: 10.1034/j.1600-0706.2002.980117.x

According to one general estimate, approximately one-third of plant species in tropical forests delay the greening of their leaves until full expansion. Because young leaves suffer the greatest predation from invertebrate herbivores, this strategy could have high selective value for shade-tolerant tree species possessing long leaf lifespans, particularly if these grow on poor soils. Since there is little colour in the cell wall, it might be assumed that flushing leaves of such species would simply be pale. However, a substantial proportion of forest species that delay leaf greening also have a considerable quantity of anthocyanin pigment in their new leaves, giving them a reddish or, very rarely, a bluish tint. These pigments are generally chemically inactive and are commonly used as colouring agents in the food industry. Several reasons have been advanced to explain the presence of these anthocyanins: they may be fungicidal; they may photoprotect leaves against UV damage, or prevent photoinhibition; their colour could make them cryptic to those herbivores blind to the red part of the spectrum. Here, we survey the literature, attempt to define delayed greening (with and without anthocyanin presence) and demonstrate the use of a simple colourimeter to assess its incidence. We then discuss what these results imply for the three hypotheses given above and the potential role of a large-scale survey.