TITLE	Application of external calcium in improving the PEG-induced water stress tolerance in liquorice cells
AUTHOR	Ming Li State Key Laboratory of Arid Agroecology, Lanzhou University, 730000, Lanzhou, P.R. China Gen-Xuan Wang State Key Laboratory of Arid Agroecology, Lanzhou University, 730000, Lanzhou, P.R. China Jiou-Sheng Lin State Key Laboratory of Arid Agroecology, Lanzhou University, 730000, Lanzhou, P.R. China
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ABSTRACT	Calcium (Ca2+) may be involved in plant tolerance to water stress by regulating antioxidant metabolism. This study was designed to examine whether external Ca2+ treatment would improve drought tolerance in liquorice cells. The results showed that water stressed treatment induced by 10% PEG could reduce significantly the FW and RWC of liquorice cells, but external Ca2+ treatment considerably increased the two factors after 10-days stress. In addition, lesser amounts of MDA and H2O2 accumulated in Ca2+-treated cells than in untreated cells, and the activities of CAT, SOD and POD in Ca2+-treated cells were higher than in untreated cells during the stress period. The measured parameters treated by 40 mmol L-1CaCl2 were higher than those treated by 10 mmol L-1CaCl2. The changes in CAT, SOD and POD activities under stressed conditions were significantly larger than those in non-stressed conditions. Under stressed conditions, the trend of SOD activities was similar to that of CAT, and the activity of CAT was larger than that of SOD. CAT activity changed in relation to H2O2 content. It was indicated that water stress induced oxidative stress in liquorice cells, and application of external calcium (40 mmol L-1) significantly improved water stress tolerance in those cells. In addition, the measured parameters were different between Ca2+-treated cells under stressed and non-stressed conditions, and it is possible that calcium signals were different coming from different stimulations. The investigations also showed that the effect of external Ca2+ on the measured parameters was not due to the regulation of osmotic potential and osmotic adjustment in liquorice cells. The mechanism that allowed extracellular Ca2+ to improve adaptation of liquorice cells to drought was mediated by mitigating oxidative stress.
KEYWORD	Aatioxidant enzyme; Ca2+; Glycyrrhiza uralensis; Polyethylene glycol; Water stress;
ARTICLE INFO	Botanical Bulletin of Academia Sinica, Volume 44 Number 4 October 2003, page 275-284, 10 pages
PUBLISHER	Institute of Plant and Microbial Biology, Academia Sinica, Taipei, Taiwan, Republic of China