Abstract
Chloris virgata, an alkali-tolerant halophyte, was chosen as the test material for our research. The seedlings of C. virgata were treated with varying salt and alkali stress. First, the composition and content of organic acids in shoots were analyzed and the results indicated that there was not only a significant increase in total organic acids, but there were also obvious changes in different components of organic acids under alkali stress. The increments in citrate were the largest, followed by malate. However, none of the organic acids showed significant alterations in the content and components under salt stress. Also, activity of some enzymes (citrate synthase, malate synthase, NADP-isocitrate dehydrogenase, and isocitrate lyase) associated with such organic acids did not change significantly under alkali stress, but malate dehydrogenase activity markedly decreased under a stronger alkali stress (80 mM). Under salt stress as well as increased malate synthase (MS) activity, however, there was no significant change for other enzymes. These results strongly demonstrated that the enzymatic regulation of organic acid metabolism may be the biochemical basis of alkali tolerance for C. virgata. Citrate synthase (CS), MS and isocitrate lyase (ICL) might be the key enzymes that determine the alkali tolerance of C. virgata. Key words: Salinity, ion balance, enzyme activity, Chloris virgata.
Highlights
More than 800 million hectares of land throughout the world are affected by salt level
Popova et al (2002) reported that the activity of NADP-ICDH in plants adapted to high salinity increased in leaves and decreased in roots, and expression of Mc-ICDH1 was found to be stimulated in leaves in salt-adapted M. crystallinum by transcript analyses and western blot hybridizations. These results indicated that organic acid metabolism is influenced by salt stress due to the alteration of some enzyme activities under salt stress, and this kind of change might play a key role in enhancing salt resistance
Qualitative and quantitative changes of organic acids under salt and alkali stress The analysis of organic acid composition showed that there were no changes in composition of organic acids in the shoots of C. virgata under salt and alkali stress compared with the control
Summary
More than 800 million hectares of land throughout the world are affected by salt level. This amount accounts for more than 6% of the world’s total land area. The salinization of soil is a widespread environmental problem and an important factor in limiting plant growth and productivity (Allakhverdiev et al, 2000). The detrimental effects of high salinity on plants can be observed at the whole-plant level as the death of plants and/or decreases in productivity.
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