PHOTOSYNTHETICA

Photosynthetica 2004, 42(4):591-596 | DOI: 10.1007/S11099-005-0018-x

Carotenoid composition of peridermal twigs does not fully conform to a shade acclimation hypothesis

E. Levizou¹, Y. Petropoulou¹, Y. Manetas^1,*

¹ Laboratory of Plant Physiology, Department of Biology, University of Patras, Patras, Greece

The photosynthetic pigments of twigs in five tree and shrub species possessing chlorenchyma under a well developed, stomata-less, and highly photon absorptive periderm were analysed and compared to those of the corresponding canopy leaves. We asked whether the unavoidable shade acclimation of corticular chlorenchyma results in photosynthetic pigment complements typically found in shade leaves. As expected, chlorophyll (Chl) a/b ratios in twigs were consistently low. However, carotenoid (Car) analysis did not confirm the initial hypothesis, since twigs generally contained increased Chl-based pool sizes of the xanthophyll cycle components. The contents of photo-selective neoxanthin and lutein were high as well. Yet, β-carotene content was extraordinarily low. In addition, twigs retained high pre-dawn ratios of the deepoxidized antheraxanthin and zeaxanthin, although environmental conditions were not pre-disposing for such a state. The unexpected Car composition allows the conclusion that other micro-environmental conditions within twigs (hypoxia, increased red to blue photon ratios, and extremely high CO₂ concentrations) are more important than shade in shaping the Car profiles.

Additional key words: Arbutus; chlorophylls; leaves; Pistacia; Populus; Prunus; Quercus; sun, shade acclimation; twig internal microenvironment; xanthophyll cycle

Received: May 31, 2004; Accepted: August 23, 2004; Published: December 1, 2004  Show citation