Aluminum-induced effects on Photosystem II photochemistry in Citrus leaves assessed by the chlorophyll a fluorescence transient

Seedlings of Citrus grandis (L.) Osbeck cv. Tuyou were irrigated daily for 5 months with nutrient solution containing 0 (control), 0.2, 0.6 or 1.6 mM aluminum (Al) from AlCl3·6H2O. Shoot growth was more sensitive to Al toxicity than root growth, gas exchange, chlorophyll (Chl) concentration, polypha...

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Bibliographic Details
Published in:Tree physiology 2008-12, Vol.28 (12), p.1863-1871
Main Authors: Jiang, Huan-Xin, Chen, Li-Song, Zheng, Jin-Gui, Han, Shuang, Tang, Ning, Smith, Brandon R
Format: Article
Language:English
Subjects:
aluminum
Aluminum - pharmacology
assimilation (physiology)
carbon dioxide
Carbon Dioxide - metabolism
chlorophyll
Chlorophyll - metabolism
Chlorophyll A
Citrus - drug effects
Citrus - growth & development
Citrus - physiology
Citrus grandis
Citrus maxima
electron transfer
Fluorescence
leaves
photochemistry
photoinhibition
photosystem II
Photosystem II Protein Complex - physiology
phytotoxicity
Plant Leaves - drug effects
Plant Leaves - physiology
Ribulose-Bisphosphate Carboxylase - metabolism
roots
shoots
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Summary:Seedlings of Citrus grandis (L.) Osbeck cv. Tuyou were irrigated daily for 5 months with nutrient solution containing 0 (control), 0.2, 0.6 or 1.6 mM aluminum (Al) from AlCl3·6H2O. Shoot growth was more sensitive to Al toxicity than root growth, gas exchange, chlorophyll (Chl) concentration, polyphasic Chl a fluorescence (OJIP) induction and related parameters. Leaves of Al-treated plants showed decreased CO2 assimilation and Chl concentration, yet intercellular CO2 concentration increased and ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) activity was unchanged. Chlorophyll a fluorescence induction analysis of Al-stressed leaves showed a large rise at the O-step and a large depression at the P-step, accompanied by two new bands at 300 μs (K-band) and at about 150 μs (L-band). Maximum fluorescence, maximum quantum yield of primary photochemistry, oxygen-evolving complex (OEC), quantum yield of electron transport, quantum yield of electron transport from QA- to the Photosystem I end electron acceptors, IP phase and total performance index were decreased in leaves of Al-treated plants, whereas minimum fluorescence, relative variable fluorescence at the J-step and I-step, and dissipated energy were increased. We propose that impaired electron transport capacity accompanied by lack of reducing equivalents were the main factors contributing to decreased CO2 assimilation in Al-treated plants. Aluminum-induced photoinhibition occurring at both the donor (i.e., the OEC) and the acceptor sides of Photosystem II may be associated with growth inhibition. Besides decreased light absorption due to reduced Chl concentration, enhanced energy dissipation protected the leaves of Al-treated plants from photo-oxidative damage in high light.
ISSN:0829-318X
1758-4469
DOI:10.1093/treephys/28.12.1863