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| Response and intraspecific differences of alfalfa to cadmium (Cd) stress |
| Received:March 12, 2017 |
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| KeyWord:Medicago sativa L.;cadmium stress;stress response;intraspecific differences;mechanism |
| Author Name | Affiliation | E-mail | | YANG Shu | College of Resources and Environment, Yunnan Agricultural University, Kunming 650201, China | | | LI Yuan | College of Resources and Environment, Yunnan Agricultural University, Kunming 650201, China | liyuan03@yahoo.com.cn | | BI Yu-fen | College of Resources and Environment, Yunnan Agricultural University, Kunming 650201, China | | | ZU Yan-qun | College of Resources and Environment, Yunnan Agricultural University, Kunming 650201, China | | | HE Yong-mei | College of Resources and Environment, Yunnan Agricultural University, Kunming 650201, China | | | JIA Le | College of Resources and Environment, Yunnan Agricultural University, Kunming 650201, China | |
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| Abstract: |
| The responses of alfalfa(Medicago sativa L.) to Cd stress are reviewed in this paper, as follows:The response of alfalfa growth to Cd stress presented trends of promotion at low concentrations and inhibition at high concentrations. The stress damage caused by Cd on alfalfa was alleviated by physiological responses including antioxidative system activation changes in biological membrane permeability, photosynthesis regulation, and osmotic regulation. Possible Cd adsorption strategies included H+ exchange in the plasma membrane of the root epidermis and Ca2+ and Mg2+ cation channels in their roots. Cd uptake in alfalfa roots was affected by the rhizosphere environment and bioavailability of Cd in soil. When Cd transported from root to shoots, it accumulated in the roots of alfalfa with an increase of Cd content in the soil. Of alfalfa plants regulated their response to Cd stress with mechanisms included signal molecular regulation, antioxidant system regulation, combining Cd with thiols, subcellular distribution of Cd, and upregulation of Cd-resistant gene expression. H2S, NO, and CO were considered possible signal molecules, while upregulation of heme oxygenase-1(HO-1) transcription and increased heme oxygenase(HO) activity could be the key to activating the antioxidant system. Intraspecific differences of alfalfa in response to Cd stress are also reviewed in this paper, including the following:Seed germination and seedling growth of alfalfa showed remarkable differences among cultivars under Cd stress, and the maximum Cd tolerance value of various alfalfa cultivars was more than nine times greater than that of the minimum value. Under Cd stress, there were remarkable differences in nodule growth, plant morphology, and biomass between alfalfa cultivars, and the root length was considered an important indicator in evaluating intraspecific differences. The changes in physiological indicators, such as glutathione reductase(GR) and ascorbate peroxidases(APXs) activity, GSH, hGSH, chlorophyll, proline, and MDA concentrations, and the leakage rate of electrolytes were very different among various alfalfa cultivars under the same level of Cd stress. Absorption and accumulation of Cd in alfalfa also had intraspecific differences. Generally, Cd stress in alfalfa should be studied further in the future to establish criteria to judge intraspecific differences, studying significant differences in system selection, analysis at the molecular level of stress response mechanisms, and intraspecific differences to Cd stress as this would help provide theoretical and practical bases for using alfalfa for the restoration and utilization of Cd-contaminated soil. |
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