Carotenoid composition and photochemical activity of four sandy grassland species |
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Authors: | S Veres V R Tóth R Láposi V Oláh G Lakatos I Mészáros |
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Institution: | (1) Department of Botany, Faculty of Science, Debrecen University, Debrecen, H-4010, Hungary;(2) Department of Applied Ecology, Faculty of Science, Debrecen University, Debrecen, H-4010, Hungary |
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Abstract: | The photosynthetic pigments and photochemical efficiency of photosystem 2 (PS2) were studied in four constitutive species
(Achillea millefolium L., Festuca pseudovina Hack. ex Wiesb., Potentilla arenaria Borkh., and Thymus degenianus Lyka) of a semiarid grassland in South-eastern Hungary. Every species displayed typical sun-adapted traits and substantial
plasticity in the composition and functioning of the photosynthetic apparatus. The contents of chlorophylls (Chls) and carotenoids
(Cars) on a dry matter basis declined from May to July, however, the amount of total Cars on a Chl basis increased. This increase
was the largest in Potentilla (48 %) and the smallest in Achillea (14 %). The pool of xanthophylls (VAZ) was between 25 % and 45 % of the total Car content and was larger in July than in
May. The content of β-carotene increased by July, but lutein content did not change significantly. The Chl fluorescence ratio
Fv/Fm was reduced by 3–10 % at noon, reflecting the down-regulation of PS2 in the period of high irradiance and high temperature.
The occurrence of minimal values of ΔF/Fm’ showed close correlation to the de-epoxidation rate of violaxanthin. Hence in natural habitats these species developed a
considerable capacity to dissipate excess excitation energy in the summer period in their photosynthetic apparatus through
the xanthophyll cycle pool and a related photoprotective mechanism, when the photochemical utilization of photon energy was
down-regulated. |
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Keywords: | chlorophyll dry mass photochemical efficiency photosystem 2 seasonal changes species differences xanthophyll cycle |
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