KMS XINJIANG INSTITUTE OF ECOLOGY AND GEOGRAPHY，CAS
| 罗布麻(Apocynum venetum)锂的吸收、分布和赋存形态的研究 | |
| Alternative Title | Li absorption, distribution and chemical forms in Apocynum venetum under Li exposures |
| 乔丽桃 | |
| Subtype | 博士 |
| Thesis Advisor | 田长彦 |
| 2019-06-30 | |
| Degree Grantor | 中国科学院大学 |
| Place of Conferral | 北京 |
| Degree Discipline | 理学博士 |
| Keyword | 罗布麻 锂吸收 锂分布 锂形态 Apocynum venetum Li uptake Li distribution Li chemical forms |
| Abstract | 锂工业的迅速发展，使大量工业废水及废弃锂电池排放到土壤中，造成土壤锂污染。罗布麻（Apocynum venetum）生长于锂丰度较高的荒漠地区，锂含量高于其伴生植物，具有富锂特性，可以用于土壤锂污染的生物修复。 另外，锂是人体必需的生命元素，从食物中获取锂是满足人体对锂需求最安全可行的方法。然而谷物和蔬菜锂含量水平较低，长期食用难于满足人体对锂的正常需求，会影响人体健康。罗布麻的富锂特性，对改善人体的锂营养也有很大的潜力。目前，植物吸收锂的机制、锂在植物中的分布定位，及锂在植物体的赋存形态并不清楚。因此阐明罗布麻锂吸收、分布、形态及生理效应，不仅为锂污染的生物修复提供理论基础，同时为调控植物体内的锂累积程度，解决人体锂缺乏问题，及保障人体健康提供理论与技术支撑。本文采用水培方法，研究不同供锂浓度对罗布麻生长的影响，并结合离子耗竭法探讨罗布麻吸收锂的机制。 并利用电感耦合等离子质谱技术（ICP-MS）及分级分离技术，分别对锂在罗布麻各器官分布及亚细胞水平的定位进行研究。同时结合连续提取法对各器官锂的化学形态进行分析。取得的主要结果如下：（1）低浓度锂能够促进植物生长。 罗布麻在锂浓度为 2.5 mg L-1 时，各器官生物量增加。 高浓度锂（≥ 50 mg L-1） 会抑制罗布麻生长。 罗布麻根系随供锂浓度的增加变细变长，而能保持根尖结构的完整性。锂对罗布麻新生叶的叶绿素含量影响不显著，而老叶叶绿素含量明显降低。并且叶尖会出现干枯，干枯症状随供锂浓度及处理时间的增加而加重。 然而锂对叶片气孔开度没有影响。（2）供锂浓度影响罗布麻对钙、钾和镁的吸收及累积。罗布麻根系在锂供应条件下，钙离子的吸收量显著增加，钙在茎中的变化不显著，叶中钙含量减少。不同的是， 罗布麻根和茎中钾含量随锂浓度的增加显著降低， 而叶中钾含量是显著增加的。 罗布麻根系镁含量减少，但受供锂浓度的影响不明显。茎中镁含量随锂浓度增加而显著增加，而叶片镁含量随供锂浓度的增加而减少。同时，罗布麻在低锂（2.5 mg L-1）浓度下，离子选择性吸收系数以及转运系数都是低于对照的， 暗示罗布麻在低锂供应下，根系细胞对锂的选择性吸收能力较钙、钾和镁都强。然而， 随供锂浓度的增加离子选择性吸收系数和运输系数的值是显著增加的， K+/Li+、 Ca2+/Li+和 Mg2+/Li+比率随锂浓度增加而减少，但不显著。表明罗布麻对 Ca2+、 K+和 Mg2+的吸收能力增加，而对锂的吸收降低。离子选择性吸收属于离子的主动吸收。同时， 锂离子吸收动力学曲线显示， 罗布麻对锂的吸收与碱金属离子钾的吸收类似，具有二相吸收特点。 呼吸抑制剂会明显降低罗布麻根系对锂的吸收，说明罗布麻对锂的吸收受能量的影响。相反，钙离子通道抑制剂的使用，对植物锂吸收的影响不显著，说明锂吸收不占用钙离子通道。（3） 锂在罗布麻器官水平的分布特点是叶>根>茎。植物根系向地上部的转运系数都在 1 以上，而且随锂浓度增加而增大。说明罗布麻根系具有较强的向上转运锂的能力。此外， 锂在成熟叶的浓度最高，其次是老叶，在新叶的含量最低。同时对单一叶片，锂在叶尖及中间部位含量较高，叶基（靠近叶柄） 含量较低。这说明，锂在罗布麻的分布可能受蒸腾流的影响。对不同植物器官进行细胞分级分离，结果显示，随供锂浓度的增加，罗布麻根、茎和叶中锂的含量都显著增加。锂在液泡中所占的比例较其它细胞器，如线粒体、叶绿体和细胞核的比例显著增加。其次是细胞壁中锂所占的比例。说明罗布麻主要将锂区隔于各器官的液泡中，其次是细胞壁。（4）随着供锂浓度的增加，不同提取态锂含量都是增加的。其中以乙醇提取态锂为主要的存在形态，其次是水溶态的锂。其中盐酸提取态、 醋酸提取态和氯化钠提取态等锂含量及比例都比较低。这说明罗布麻中锂的存在形态主要以一些醇溶性的蛋白质和氨基酸锂为主，其次是与有机酸结合的水溶性的锂。这两种形态的锂具有较高的移动性，有利于锂在植物器官的转运。同时也预示较强的毒性。总之，罗布麻根系对锂的吸收可能是一个主动的过程，吸收的锂大部分富集在植物叶片中，并且主要区隔于细胞液泡中。而且大部分的锂与醇溶性的蛋白质或氨基酸结合，易于迁移。罗布麻在外源供锂条件下，通过调节其自身对锂离子吸收和运输的选择性，保证在低浓度下锂的吸收，促进生长；同时调节体内的阳离子与锂的比率，维持细胞内离子稳态，减少高锂对罗布麻生长的抑制和毒害。 |
| Other Abstract | Lithium (Li) has widespread applications in various industries, and amount ofindustrial waste water and discarded batteries are dumped into the soil, raising the riskof Li pollution in environment. Besides, Li is an essential element for human and Li infood is security and healthy source for human. However, Li contents in grains andvegetables are relatively low, which fail to meet the normal demand for humanhealthy. Apocynum venetum rooted widely in the desert region of Xinjiang,accumulated comparatively higher Li content than its companion plants. As a Liaccumulator, it is an ideal material for bioremediation of Li pollution in soil. Inaddition, Apocynum venetum is a safety and healthy source for human Li nutrition.However, the mechanism of Li absorption, Li distribution and Li chemical forms inplants are unclear. In this paper, Apocynum venetum was used for the systematic studyon Li absorption, distribution, chemical forms and physiological effects in plants. Thisresearch will not only provide theoretical basis for bioremediation of Li pollution, butalso provide theoretical and technical support for regulating Li accumulation in plants,solving the problem of Li deficiency in human body.In this paper, Li was supplied as LiCl in hydroponic culture. Ion depletionmethod was used to figure out the mechanism of Li uptake in the root of Apocynumvenetum. In addition, the distribution of Li in various organs under different Lisupplements were detected by inductively coupled plasma mass spectrometry(ICP-MS). The localization of Li at the subcellular level in Apocynum venetum wasanalyzed by fractional separation technique. The chemical forms of Li in variousorgans extracted sequentially by different extractants. The results are as follows:(1) Low Li concentration stimulated plant growth. For Apocynum venetum, plantbiomass increased at 2.5mg L-1 Li concentration, while high Li concentrations(≥ 50 mg L-1) inhibited plant growth.Morphology alterations occurred in roots and leaves under higher Li supply. Theroots of Apocynum venetum became thinner and longer with the increase of Liconcentration. For leaves, the chlorophyll content of new-born leaves was notsignificantly affected, while the content of chlorophyll in old leaves was significantlyreduced, and the leaf tip was withered. The withered symptom was aggravated withthe increase of Li supply and Li treatment time. Compared to organ alterations, there were no significant change in the structure of root tip, stem crosscutting tissue andstomata of Apocynum venetum analyzed by scanning electron microscope.(2) Li concentration affected the accumulation of calcium, potassium andmagnesium in plants. The absorption of calcium (Ca) in root of Apocynum venetumremarkably increased with the increase of Li concentration. The alteration of Ca in thestems was not obvious. The content of calcium in leaves significantly decreased.Besides, potassium (K) content in roots and stems of Apocynum venetum decreasedstrikingly, while K content in leaves increased remarkably. The effect of Liconcentration on magnesium (Mg) content in roots was not striking. Mg content in thestems increased significantly. However, Mg content decreased sharply in leaves ofApocynum venetum.Under low lithium concentration (2.5mg L-1), the ionic selective absorptioncoefficient, and transport coefficient were all lower than the control group, suggestingthat root cells of Apocynum venetum have stronger selective absorption capacity for Liions than calcium, potassium and magnesium. While， the values of ionic selectiveabsorption coefficient and transport coefficient increased significantly with theincrease of lithium concentration. In addition, the ratios of K+/Li+, Ca2+/Li+ andMg2+/Li+ decreased with the increase of lithium concentration, but not significantly.The results showed that the absorption of Ca2+, K+ and Mg2+ was increased, but theabsorption of Li+ was decreased.In addition, Li absorption curve showed that Li uptake in the roots of Apocynumvenetum under short-term Li treatment was similar with the alkali metals, whichfollowed dual absorption mechanism. The energy inhibitor significantly reduced Liuptake in roots, indicating that the absorption of Li in Apocynum venetum wasassociated with energy. However, calcium channel inhibitor had no significant effecton Li uptake.(3) Li distribution differ in different organs. Li accumulation was highest in theleaf of Apocynum venetum, followed by root, and Li concentration in stem was lowest.The value of the translocation factor (TF) in Apocynum venetum was higher than 1,and increased with the increased Li supplementations, indicating that the roots ofApocynum venetum had a strong ability to transport Li upward.In addition, Li concentration varied in different leaves. It showed that higher Liaccumulation occurred in the mature and old leaves, while Li concentration in new leaf was lower. Besides, Li concentration in the individual leaf was different. Theapex of the leaf had higher Li content than the base of the leaf, while highest Liaccumulation occurred in the rest part (middle) of the leaf. These indicated that thedistribution of Li in Apocynum venetum may be affected by transpiration current.Besides, Li content in different organelles were differ in root, stem and leaf, andincreased significantly with the increase of the Li supply. Li accumulated mainly invacuoles， followed by cell walls. The proportion of Li in vacuoles and cell walls weresignificantly higher than that in other organelles, such as mitochondria, chloroplastsand nucleus. This indicates that, higher Li accumulation were compartmentalized invacuole of each organ, followed by the cell walls.(4) The result of sequential extraction showed that the Li content in differentextractants increased with the increasing Li supply. Besides, ethanol-extracted Li wasthe main chemical form, followed by water-soluble Li. However, the content andproportion of hydrochloric acid and acetic acid extracted Li are relatively low. Thisindicated that Li ion in the tissues of Apocynum venetum was primarily chelated bycertain ethanol-soluble proteins or amino acids. In addition, Li ions partly bondedwith water-soluble organic acid. These two forms of Li have high mobility, which isconducive to the transport of Li in plant organs, also highly toxic.In conclusion, Li uptake in Apocynum venetum was an active process driven byenergy from respiration. In addition, amount of lithium accumulated in the leaves andcompartmentalized in vacuoles of cells. The lithium in cells largely bound toalcohol-soluble proteins or amino groups with higher mobility. The ionic selectiveabsorption capability in Apocynum venetum changed under different Lisupplementations to 1) increase Li uptake at low Li concentration, which stimulatedplant growth, 2) maintain the ratio of cation and lithium under higher Li supply,regulating ion homeostasis to tolerate Li stress. |
| Subject Area | 生态学 |
| Language | 中文 |
| Document Type | 学位论文 |
| Identifier | http://ir.xjlas.org/handle/365004/15280 |
| Collection | 中国科学院新疆生态与地理研究所 研究系统 |
| Affiliation | 中国科学院新疆生态与地理研究所 |
| First Author Affilication | 中国科学院新疆生态与地理研究所 |
| Recommended Citation GB/T 7714 | 乔丽桃. 罗布麻(Apocynum venetum)锂的吸收、分布和赋存形态的研究[D]. 北京. 中国科学院大学,2019. |
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