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KMID : 0903519980410010053
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Journal of the Korean Society of Agricultural Chemistry and Biotechnology
1998 Volume.41 No. 1 p.53 ~ p.59
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Effects of Osmoprotectants on the Growth and Nitrogenase Activity of Rhizobium and Azospirillum under Osmotic Stress
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Gal Sang-Wan
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Abstract
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The Rhizobium and Azospirillum spp. were isolated from the root nodules of several leguminous plants and rhizosphere of various paddy rice varieties. The growth of the nitrogen-fixing strains isolated was largely inhibited in yeast extract-mannitol medium (AMA) containing 0.6 M NaCl. In response to osmotic stress, the nitrogen-fixing strains accumulate intracellular free glutamate. The growth and nitrogenase activity of Rhizobium and Azospirillum were increased by addition of osmoprotectants such as proline, glycine betaine, and glutamate during salt stress. Glycine betaine was the most effective among exogenous osmoprotectants tested. In the absence of sodium chloride, nitrogenase activity seem to be slightly decreased by the presence of the proline or glycine betaine. These results revealed that nitrogenase activity was repressed by fixed nitrogens such as proline or glycine betaine.
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