© 2007 Heron Publishing—Victoria, Canada
Leaf morphological and physiological adjustments to the spectrally selective shade imposed by anthocyanins in Prunus cerasifera
A. Kyparissis (1), G. Grammatikopoulos (2) and Y. Manetas (2,3)
1. Laboratory of Botany, Department of Biological Applications and Technology, University of Ioannina, 45110, Ioannina, Greece / 2. Laboratory of Plant Physiology, Department of Biology, University of Patras, 26500 Patras, Greece / 3. Corresponding author (y.manetas@upatras.gr) / Received May 16, 2006; accepted June 13, 2006; published online March 1, 2007
Summary
Prunus domestica L. has green leaves, whereas Prunus cerasifera Ehrh. var. atropurpurea has red leaves due to the presence of mesophyll anthocyanins. We compared morphological and photosynthetic characteristics
of leaves of these species, which were sampled from shoots grafted in pairs on P. domestica rootstocks, each pair comprising one shoot of each species. Two hypotheses were tested: (1) anthocyanins protect red leaves
against photoinhibition; and (2) red leaves display shade characteristics because of light attenuation by anthocyanins. Parameters
were measured seasonally, during a period of increasing water stress, which caused a similar drop in shoot water potential
in each species. As judged by predawn measurements of maximum PSII yield, chronic photoinhibition did not develop in either
species and, despite the anthocyanic screen, the red leaves of P. cerasifera displayed lower light-adapted PSII yields and higher non-photochemical quenching than the green leaves of P. domestica. Thus, it appears that, in this system, anthocyanins afford little photoprotection.
As predicted by the shade acclimation hypothesis, red leaves were thinner and had a lower stomatal frequency, area- based
CO2 assimilation rate, apparent carboxylation efficiency and chlorophyll a:b ratio than green leaves. However, red leaves were
similar to green leaves in conductivity to water vapor diffusion, dry-mass-based chlorophyll concentrations and carotenoid:chlorophyll
ratios. The data for red leaves indicate adaptations to a green-depleted, red-enriched shade, rather than a neutral or canopy-like
shade. Thus, green light attenuation by anthocyanins may impose a limitation on leaf thickness. Moreover, the selective depletion
of light at wavelengths that are preferentially absorbed by PSII and chlorophyll b may lead to adjustments in chlorophyll
pigment ratios to compensate for the uneven spectral distribution of internal light. The apparent photosynthetic cost associated
with lost photons and reduced leaf thickness, and the absence of a photoprotective advantage, suggest that there are other,
yet to be identified, benefits for permanently anthocyanic leaves of P. cerasifera.
Keywords:
chlorophyll fluorescence, CO2 assimilation, internal light environment, non-photochemical quenching, photoprotection, pigments, PSII yield, red leaves.
