Journal
PLANT PHYSIOLOGY AND BIOCHEMISTRY
Volume 93, Issue -, Pages 44-55Publisher
ELSEVIER FRANCE-EDITIONS SCIENTIFIQUES MEDICALES ELSEVIER
DOI: 10.1016/j.plaphy.2015.01.008
Keywords
Anthocyanins; Antioxidative enzymes; High light intensity; Flavonoids; Sugar distribution; UV-B radiation; Variegation
Categories
Funding
- Ministry of Education and Science, Republic of Serbia [III 43010]
- COST Action [FA0906]
- Austrian Science Fund (FWF) [P 22988] Funding Source: researchfish
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We studied the specific effects of high photosynthetically active radiation (PAR, 400-700 nm) and ecologically relevant UV-B radiation (0.90 W m(-2)) on antioxidative and phenolic metabolism by exploiting the green-white leaf variegation of Pelargonium zonale plants. This is a suitable model system for examining source-sink interactions within the same leaf. High PAR intensity (1350 mu mol m(-2) s(-1)) and UV-B radiation induced different responses in green and white leaf sectors. High PAR intensity had a greater influence on green tissue, triggering the accumulation of phenylpropanoids and flavonoids with strong antioxidative function. Induced phenolics, together with ascorbate, ascorbate peroxidase (APX, EC 1.11.1.11) and catalase (CAT, EC 1.11.1.6) provided efficient defense against potential oxidative pressure. UV-B-induced up-regulation of non-phenolic H2O2 scavengers in green leaf sectors was greater than high PAR-induced changes, indicating a UV-B role in antioxidative defense under light excess; on the contrary, minimal effects were observed in white tissue. However, UV-B radiation had greater influence on phenolics in white leaf sections compared to green ones, inducing accumulation of phenolic glycosides whose function was UV-B screening rather than antioxidative. By stimulation of starch and sucrose breakdown and carbon allocation in the form of soluble sugars from source (green) tissue to sink (white) tissue, UV-B radiation compensated the absence of photosynthetic activity and phenylpropanoid and flavonoid biosynthesis in white sectors. (C) 2015 Elsevier Masson SAS. All rights reserved.
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