Journal
JOURNAL OF PLANT PHYSIOLOGY
Volume 165, Issue 12, Pages 1264-1273Publisher
ELSEVIER GMBH, URBAN & FISCHER VERLAG
DOI: 10.1016/j.jplph.2007.10.007
Keywords
allelochemical; antioxidants; ethyl 2-methyl acetoacetate (EMA); Microcystis aeruginosa; water bloom
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Funding
- National Natural Science Foundation of China (NSFC)-Japan Science and Technology Agency (JST) [50721140017]
- [2006BAC101303]
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Macrophytic allelochemicals are considered an environment-friendly and promising alternative to control algal. bloom. However, studies examining the potential mechanisms of inhibitory allelochemicals on algae are few. The allelochemical ethyl 2-methyl acetoacetate (EMA), isolated from reed (Phragmites communis), was a strong allelopathic inhibitor on the growth of Microcystis aeruginosa. EMA-induced antioxidant responses were investigated in the cyanobacterium M. aeruginosa to understand the mechanism of EMA inhibition on algal. growth. The activities of enzymatic antioxidants superoxide dismutase (SOD) and catalase (CAT), and the contents of non-enzymatic antioxidants reduced glutathione (GSH) and ascorbic acid (AsA) of M. aeruginosa cells were analyzed after treatments with different concentrations of EMA. Exposure of M. aeruginosa to EMA caused changes in enzyme activities and contents of non-enzymatic antioxidants in different manners. The decrease in SOD activity occurred first after 4 h of EMA exposure, and more markedly after 40 h. CAT activity did not change after 4 h of EMA exposure, but increased obviously after 40h. The contents of AsA and GSH were increased greatly by EMA after 4 h. After 60 h, tow EMA concentrations still increased the CAT activity and the contents of AsA and GSH, but high EMA concentrations started to impose a marked suppression on them. EMA increased dehydroascorbate (DHAsA) and oxidized glutathione (GSSG) contents during all exposure times. After 60 h, the regeneration rates of AsA and GSH (represented by the AsA/DHAsA ratio and GSH/GSSG ratio, respectively) were reduced by high EMA concentrations. These results suggest that the activation of CAT and the availability of AsA and GSH at early exposure are important to counteract the oxidative stress induced by EMA, and the inactivation of SOD may be crucial to the growth inhibition of M. aeruginosa by EMA. (c) 2007 Elsevier GmbH. All rights reserved.
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