盐肤木对铅的吸收累积及耐性机制

发布时间：2018-06-10 06:03

本文选题：盐肤木 + 铅　；参考：《中国林业科学研究院》2017年博士论文

【摘要】：土壤重金属污染已成为深受全球关注的环境问题之一。铅是一种对人体危害极大的有毒重金属,铅可通过食物链对人体健康造成威胁。因此修复铅污染土壤显得十分紧迫。植物修复技术是一种绿色、低成本的土壤污染修复技术。前期研究中发现盐肤木(Rhus chinensi Mill)在矿区环境中,对铅有良好的吸收转运能力。因此,明确盐肤木对铅的吸收转运过程,阐明其转运铅的内在机制,不仅有助于人们了解木本植物铅的转运途径及其运输机制,也将为土壤重金属铅污染植物修复提供科学依据。本研究通过土培和水培模拟试验深入探讨盐肤木对铅的吸收和耐性机制,揭示盐肤木根系对铅的吸收、累积、分布机理;铅在盐肤木体内的化学形态及亚细胞分布;根细胞壁在铅累积中的作用。主要研究结果如下:(1)铅胁迫下,盐肤木生物量减少,光合色素含量减少,膜脂过氧化程度显著加大;盐肤木表现出一定的毒害症状;同时抗氧化酶活性有升高的趋势。表明盐肤木能够耐受中等浓度铅引起的氧化胁迫,并且通过响应抗氧化体系来实现自我保护。土培和水培条件下,铅主要富集在植物根系,特别是在侧根。细胞壁是铅主要积累位点,其次积累在可溶性组分。铅在植物体内主要以醋酸提取态、盐酸提取态和氯化钠提取态等形态存在。铅胁迫下显著降低了铅分布在细胞壁的比例;而活性较强的氯化钠提取态铅所占比例增加。这种现象的发生可能是植物生物量下降的主要原因。铅胁迫下盐肤木幼苗根系分泌物中草酸浓度显著增加,同时会诱导根系产生苹果酸和柠檬酸,且浓度随着铅浓度增加而增加,表明植物可以利用不同形式的有机酸与铅离子螯合并将其运输至可收获部分。土培和水培下盐肤木铅转移系数分别为0.21-0.55和0.19-0.44,表明盐肤木具有一定的铅转移能力。(2)盐肤木根细胞壁(CW)及其组分(CW1、CW2和CW3)对铅的吸附试验结果表明:细胞壁中的纤维素、果胶、木质素等在铅吸附中的贡献较大;同时蛋白也参与到铅吸附中。吸附动力学分析表明孔内扩散进程不是唯一的限速步骤。Freundlich模型可较好描述盐肤木细胞壁及其各组分的铅吸附过程并表明这个过程是良好的。热力学分析表明所有盐肤木根细胞壁材料的吸附过程均是吸热的。(3)盐肤木根系对铅的吸收同溶液中铅活度有关。喷施蒸腾抑制剂后,蒸腾量有显著下降,但两个处理组根系中铅浓度无显著差异。低温处理和两种代谢抑制剂处理则显著抑制盐肤木根系对铅的吸收,但并不能完全抑制根系的主动吸收。因此通过以上几个试验表明盐肤木根系对铅的吸收可能是两种吸收类型共存,且共质体途径贡献率为23.9%。盐肤木各组织中铅浓度与吸收液中铅浓度呈显著正相关,盐肤木各组织对不同浓度铅的吸收过程可用改良Michaelis-Menten方程描述,初步表明盐肤木对铅的吸收是通过载体进行的。(4)水培试验表明低浓度钙显著抑制了盐肤木根系对铅的吸收,但高浓度钙处理(2mmol·L-1和4 mmol·L-1)则促进了盐肤木根系对铅的吸收。添加钙离子通道抑制剂和蛋白合成抑制剂后,盐肤木根系铅浓度也较对照有显著减少。通过以上试验结果可知盐肤木对铅的吸收可能与钙离子通道有关并受膜上蛋白调控。但高钙处理下盐肤木根系浓度高于对照组,表明盐肤木可能还存在其它阳离子通道运输途径。铅胁迫下,盐肤木植物体内钙和钾浓度减少。同时根系中钙和钾离子流速数据表明铅干扰了盐肤木对钙和钾的吸收。钙和钾离子的稳态平衡被打破,这可能是铅造成盐肤木毒害的原因之一。(5)试验结果表明,草酸和柠檬酸的添加未对盐肤木产生明显的生理毒害效应。其中,低浓度柠檬酸(0.5 mmol·L-1)和高浓度草酸(1.0 mmol·L-1)试验组各指标的变化趋势比其它试验组更为灵敏。低浓度柠檬酸(0.5 mmol·L-1)能促进盐肤木铅吸收。相反草酸的添加并未使得盐肤木根系能吸收更多的铅。外源柠檬酸和草酸可以在一定程度上促进植物对铅的转运。铅在植物体内主要以有效性较低的提取态(醋酸提取态、盐酸提取态和氯化钠提取态)存在,因此外源柠檬酸和草酸与铅形成金属螯合物能够缓解铅离子对植物体的毒害。
[Abstract]:Heavy metal pollution in soil has become one of the environmental problems that are deeply concerned around the world. Lead is a kind of toxic heavy metal which is very harmful to human body. Lead can threaten human health through food chain. Therefore, it is very urgent to repair lead contaminated soil. Phytoremediation technology is a green, low cost soil remediation technology. It is found that Rhus Chinensi Mill has good absorption and transport ability to lead in the mining environment. Therefore, it is not only helpful for people to understand the transport mechanism of lead and its transport mechanism, but also for the plant of heavy metal lead pollution in the soil. This study provides a scientific basis for the study. This study explored the absorption and tolerance mechanism of saline wood to lead by soil culture and hydroponic simulation, and revealed the absorption, accumulation and distribution of lead in the root system of the salt skin, the chemical form and subcellular distribution of lead in skin and the role of the root cell wall in the accumulation of lead. The main results are as follows: (1) lead stress Under the pressure, the biomass of Rhus chinensis decreased, the content of photosynthetic pigments decreased, the degree of membrane lipid peroxidation increased significantly; the salt skin showed certain toxic symptoms, and the activity of antioxidant enzymes increased. It indicated that the saline wood could tolerate the oxidative stress caused by moderate concentration of lead and realized self protection by response to the antioxidant system. Under the condition of hydroponics, lead is mainly enriched in plant roots, especially in lateral roots. Cell wall is the main accumulation site of lead, followed by the accumulation of soluble components. Lead is mainly in the form of acetic acid extraction, extraction state of hydrochloric acid and extraction state of sodium chloride in the plant. The proportion of lead in cell wall is significantly reduced under lead stress; and the activity is more than that of lead. This phenomenon may be the main reason for the decrease of plant biomass. The concentration of oxalic acid in root exudates of the seedlings under lead stress is significantly increased, and the root production of malic acid and citric acid will be induced, and the concentration increases with the increase of the concentration of lead, indicating that plants can be used not. The same form of organic acid was combined with lead ion chelate and transported to the reacable part. The transfer coefficient of lead in soil culture and hydroponics was 0.21-0.55 and 0.19-0.44 respectively, indicating that the salt skin had a certain ability of lead transfer. (2) the results of the adsorption test of the root cell wall (CW) and its components (CW1, CW2 and CW3) on the lead showed that the fiber in the cell wall was the fiber. The contribution of vitamin, pectin and lignin to lead absorption is great, and the protein also participates in the lead absorption. Adsorption kinetics analysis shows that the process of intraporm diffusion is not the only speed limit step.Freundlich model, which can better describe the lead adsorption process of the cell wall and its components and show that this process is good. The adsorption process of all the root cell wall materials of the salt skin was endothermic. (3) the absorption of lead in the root system of the salt skin was related to the lead activity in the solution. After spraying transpiration inhibitors, the transpiration decreased significantly, but there was no significant difference in the lead concentration in the roots of the two treatment groups. The low temperature treatment and the treatment of two kinds of metabolic inhibitors significantly inhibited the salt skin. The root system absorbs lead, but it does not completely inhibit the active absorption of root system. Therefore, these experiments show that the absorption of lead in the root system of the salt skin may be two types of absorption, and the contribution rate of the common plastid pathway is the significant positive correlation between the lead concentration and the lead concentration in the absorption solution of 23.9%.. The absorption process of different concentrations of lead can be described by the modified Michaelis-Menten equation. It is preliminarily indicated that the absorption of lead in salinwood is carried out through the carrier. (4) the hydroponic test shows that low concentration of calcium significantly inhibits the absorption of lead in the root system of the salt skin, but the high concentration calcium treatment (2mmol. L-1 and 4 mmol. L-1) promotes the absorption of lead in the root system of the salt skin. After adding calcium ion channel inhibitors and protein synthesis inhibitors, the lead concentration in the root system of the salt skin was also significantly reduced. The results showed that the absorption of lead could be related to the calcium channel and regulated by the protein on the membrane. However, the root concentration of the salt skin was higher than that of the control group, indicating the possibility of the salt skin. There are other channels of cation channel transport. Under lead stress, the concentration of calcium and potassium in the plant body is reduced. At the same time, the data of calcium and potassium ions in the root system show that lead interferes with the absorption of calcium and potassium. The steady equilibrium of calcium and potassium ions is broken, which may be one of the causes of the toxicity of lead. (5) experimental results. The results showed that the addition of oxalic acid and citric acid did not produce obvious physiological toxic effects on the salt skin. Among them, the change trend of low concentration citric acid (0.5 mmol. L-1) and high concentration oxalic acid (1 mmol. L-1) test group was more sensitive than that of other experimental groups. Low concentration citric acid (0.5 mmol. L-1) could promote the absorption of lead in salt skin. The addition of citric acid and oxalic acid can promote the transport of lead to plants to a certain extent. The lead in plants is mainly in the presence of low availability (acetic acid extraction state, hydrochloric acid extraction state and sodium chloride extraction state) in plants, and the metal chelate is formed because of the exogenous citric acid and oxalic acid and lead. Things can relieve the toxic effects of lead ions on plants.
【学位授予单位】：中国林业科学研究院
【学位级别】：博士
【学位授予年份】：2017
【分类号】：X173;X53

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