© 2006 Heron Publishing—Victoria, Canada
The importance of being red when young: anthocyanins and the protection of young leaves of Quercus coccifera from insect herbivory and excess light
Panagiota Karageorgou (1) and Yiannis Manetas (1, 2)
1. Laboratory of Plant Physiology, Department of Biology, University of Patras, GR-26500 Patras, Greece / 2. Corresponding author (y.manetas@upatras.gr) / Received May 25, 2005; accepted August 18, 2005; published online February 1, 2006
Summary
Young leaves of many plants are transiently red because of the accumulation of anthocyanins, with the redness disappearing
as leaves mature. Among the many hypothetical functions of foliar anthocyanins, two are tested in this field study: the sunscreen
photoprotective function against excess visible light and the handicap signal against herbivory. We took advantage of intraspecies
variation in anthocyanin concentrations of young leaves of Quercus coccifera L. to compare in vivo chlorophyll fluorescence parameters, reflectance spectra, total phenolics and the extent of herbivory
of leaves of red- and green-leaved phenotypes occupying the same habitat. Photosystem II (PSII) photochemical efficiencies
obtained at various photon fluence rates of red light were similar in green and red leaves. In white light, PSII efficiencies
were slightly higher in red leaves than in green leaves, indicating a slight photoprotective role of anthocyanins in the field.
However, compared with red phenotypes, green phenotypes suffered greater herbivore damage, as judged by the number of leaves
attacked and the area lost to herbivory. In addition, there was a positive correlation between the concentrations of anthocyanins
and total phenolics. We suggest that the importance of a photoprotective anthocyanic screen is low in thin, young leaves with
low chlorophyll concentrations because the green light attenuated by anthocyanins is less significant for chlorophyll excitation.
However, the decreased reflectance in the green spectral band and the concomitant leveling of reflectance throughout the 400–570
nm spectral range may either make red leaves less discernible to some insect herbivores or make insect herbivores more discernible
to predators, or both. Moreover, excessive herbivory may be additionally discouraged by the high phenolic concentrations in
red leaves.
Keywords:
handicap signal, herbivory, insect vision, phenolics, photoinhibition.
