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Urunchi, China

Li L.,Xinjiang Institute of Ecology and Geography | Pan X.,Xinjiang Institute of Ecology and Geography | Li H.,Xinjiang Forest Academy
International Journal of Agriculture and Biology | Year: 2012

The responses of photosystem II (PSII) activity of samara and leaf of Siberian elm (Ulmus pumila L.) to chilling (5°C) and freezing (-5°C & -15°C) temperature and their recovery were investigated. There was little difference in Fv/Fm between samara and leaf. Leaf showed more efficient photosynthesis (PI ABS) and electron transport (φ Eo & Ψo) than samara. Chilling and freezing had adverse impact on PSII function in both samara and leaf. Low temperature stress decreased photochemical efficiency (Fv/Fm & PI ABS) and electron transport activity (ψ o, ψ Eo & ETo/RC) in both leaf and samara. PSII of samara was more tolerant to low temperature stress than leaf. Photochemical efficiency (Fv/Fm) for chilled (at 5°C) or mild frozen (at - 5°C) samara or leaf showed a recovery trend. Severe freezing stress (-15°C) led to drastic and irreversible injuries to PSII in samara and leaf. The fact that samara has photosynthetic activity and is more tolerant to low temperature than leaf is of great ecological significance for seed development, population establishment and the northern distribution limit of Siberian elm in northern hemisphere. © 2011 Friends Science Publishers. Source

Li L.,Xinjiang Institute of Ecology and Geography | Li L.,Xinjiang Forest Academy | Chen X.,Xinjiang Institute of Ecology and Geography | Chen X.,Xinjiang Forest Academy | And 4 more authors.
Pesticide Biochemistry and Physiology | Year: 2010

Effects of insecticide acetamiprid on photosystem II (PSII) activity of Synechocystis sp. were investigated by a variety of in vivo chlorophyll fluorescence tests. Acetamiprid exposure increased the proportion of inactivated PSII reactive centers (PSIIX) and led to loss of active centers (PSIIA). High concentration (1.0mM) acetamiprid decreased amplitude of the fast phase and increased the slow phase of fluorescence decay during QA- reoxidation. The electron transport after QA was hindered by high concentration acetamiprid and more QA had to be reoxidized through S2(QAQB)- charge recombination. Acetamiprid decreased the density of the active reaction centers, electron transport flux per cross section and the performance of PSII activity but had little effect on dissipated energy flux per reaction center, antenna size and the maximum quantum yield for primary photochemistry (Fv/Fm). The target site of acetamiprid toxicity to the PSII of Synechocystis sp. was electron transfer on the acceptor side. © 2010 Elsevier Inc. Source

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