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摘要： 以草原1号(抗旱型)和龙牧81(旱敏感型)这2种苜蓿为材料,采用水培方法,研究聚乙二醇(polyethylene glycol,PEG)胁迫下苜蓿幼苗不同器官中Na+、K+、Ca2+、Mg2+含量的变化。对2种苜蓿幼苗在不同PEG胁迫下离子含量变化进行分析,探讨干旱环境对苜蓿营养器官离子含量的影响。结果表明:2种苜蓿幼苗随着PEG质量分数的增加,根、茎、叶中Na+含量增加,K+、Ca2+、Mg2+含量减少,K+/Na+、Ca2+/Na+、Mg2+/Na+比值出现下降或先下降后升高的变化趋势。除草原1号在低质量分数处理时根中和高质量分数处理时叶中Na+含量增加幅度大于龙牧81外,其他各器官在PEG处理下的Na+含量增加幅度均小于龙牧81;在高质量分数PEG处理下,耐旱性强的草原1号的根、叶中的K+和Mg2+含量大于龙牧81,茎中K+和Mg2+含量小于龙牧81;在相同质量分数PEG处理下,耐旱性强的草原1号根、茎和叶中Ca2+含量明显高于耐旱性弱的龙牧81;在高质量分数PEG胁迫下,草原1号叶片中Ca2+含量明显高于龙牧81,根和叶中3种离子的比值和茎的Ca2+/Na+均为草原1号高于龙牧81。干旱胁迫影响苜蓿幼苗对上述矿质元素在根、茎、叶营养器官的分布,与苜蓿幼苗的抗旱性有一定的相关性。
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Abstract: The ions distribution in plants was changed under drought and other stresses. Plants could alleviate the damages caused by drought and enhance the adaptability to drought by re-constructing a new balance of sodium (Na+), potassium (K+), calcium (Ca2+) and magnesium (Mg2+) ions. Alfalfa, a kind of perennial leguminous plant, is the best and most important leguminous grass in the world. It plays important roles in the development of animal husbandry and the improvement of agricultural ecological environment. However, the development of alfalfa industry is limited because of the drought in the main planting area for alfalfa in North China. Monitoring the distribution changes of the four ions in drought-resistant and drought-sensitive alfalfa under drought stress would help to understand the mechanism by which alfalfa resists drought stress.
Water culture method was used to examine the contents changes of Na+, K+, Ca2+, Mg2+ in different organs of alfalfa cultivars Grassland 1 (drought-resistant) and Longmu 81 (drought-sensitive) under different concentrations 10%,15%, 20%, 25% of polyethylene glycol (PEG) stress (simulating drought stress), to investigate the responses of alfalfa to drought stress regarding to ions balance.
The results showed that in both drought-resistant and drought-sensitive alfalfa seedlings, the content of Na+ increased whereas the contents of K+, Ca2+ and Mg2+ decreased in the roots, stems and leaves with the increase of PEG concentration. In the same condition, the ratios of K+ to Na+ (K+/Na+), Ca2+ to Na+ (Ca2+/Na+) and Mg2+ to Na+ (Mg2+/Na+) were decreased or decreased at first and then increased.
The increment of Na+ content in the roots of Grassland 1 was more than that of Longmu 81 under low concentration of PEG stress, and the same phenomenon was observed in leaves under high concentration of PEG. Besides, it was opposite in other organs under different concentrations of PEG stress. Under high concentration of PEG, the increments of K+ and Mg2+ contents in the roots and leaves of the Grassland 1 were more than those of Longmu 81, whereas they were less in the stems. The increment of Ca2+ content in roots, stems and leaves of the Grassland 1 were all significantly more than those of Longmu 81 under different concentrations of PEG, respectively. Compared with Longmu 81, the ratios of K+/Na+, Ca2+/Na+, Mg2+/Na+ in roots and leaves, and the ratio of Ca2+/Na+ in Grassland 1 were all increased under high concentration of PEG.
With the increase of PEG concentration, in the roots, stems and leaves of alfalfa seedlings, Na+ content increased whereas K+, Ca2+, Mg2+ contents decreased, and the ratios of K+/Na+, Ca2+/Na+, Mg2+/Na+ decreased too. When the concentration of PEG was 25%,the contents of K+, Ca2+, Mg2+ and the ratios of K+/Na+, Ca2+/Na+, Mg2+/Na+ in the roots and leaves of drought-resistant alfalfa (Grassland 1) were more than those of drought-sensitive one (Longmu 81), but it was not the case in stems. These suggested that the changes of ion content may be involved in the drought resistance of alfalfa. |
