桉树对砷的生理响应和解毒机制研究

发布时间：2018-05-15 13:48

本文选题：桉树 + 砷　；参考：《广西大学》2017年硕士论文

【摘要】：本文以桉树为实验材料,通过水培实验,研究了不同浓度砷胁迫对桉树生物量、叶绿素和丙二醛(MDA)含量,以及对桉树抗氧化酶系统(超氧化物岐化酶(SOD)、过氧化氢酶(CAT)和过氧化物酶(POD))和部分巯基物质(非蛋白巯基(NPT)、谷胱甘肽(GSH)和植物螯合素(PCs))含量的影响;研究了砷在桉树根和叶中的亚细胞分布和化学形态,并从砷的亚细胞分布和化学形态,以及桉树的抗氧化酶系统和巯基物质的螯合作用等方面探讨了桉树对砷的解毒机制。论文主要研究结果如下:(1)高浓度砷能显著抑制桉树生长,使桉树受到较强的氧化性损伤。低浓度砷(5 mg/L和10 mg/L)胁迫7 d和14 d时,桉树根、茎和叶的生物量及根和叶中MDA含量较对照无显著性差异,表明低浓度砷胁迫对桉树没有明显的毒害作用。高浓度砷(20 mg/L和30 mg/L)胁迫时,桉树生物量和叶绿素含量减少,MDA含量显著性增加,高浓度砷能抑制桉树生长,使桉树遭受较强的氧化损伤。(2)根部对砷的滞留作用及限制吸收作用是桉树解砷毒的重要机制。砷胁迫时,桉树各部位砷的积累量顺序为:根茎叶,大部分砷存储在根部(76.9%-88.9%),砷从根部向地上部的转运受到限制,能减轻砷对桉树地上部的毒害。砷胁迫时,随砷浓度的增加桉树根中砷积累量先增加后基本保持不变,表现出一定的限制吸收作用。(3)可溶组分对砷的区室化作用、细胞壁组分对砷的固定作用及根中部分砷转变为氯化钠提取态是桉树解砷毒的重要机制。砷胁迫时,桉树根和叶中的砷主要分布在可溶组分(分布比例分别为66.3%-79.9%和50.6%-53.8%),其次是细胞壁组分(分布比例分别为14.6%-23.2%和35.6%-39.9%)。砷胁迫时,根部砷的主要存在形态是乙醇提取态(29.5%-40.00%)、去离子水提取态(28.3%-32.3%)和氯化钠提取态(24.1%-33.8%)。随砷胁迫浓度的增加,乙醇提取态的砷的比例先基本不变后减少,去离子水提取态的比例先增加后保持不变,氯化钠提取态的比例先减少后增加。根中部分砷与果胶酸盐或蛋白质的结合,增加了氯化钠提取态的比例,能在一定程度上降低砷对桉树的毒害。另一方面,大量的砷未能向更稳定的化学形态转变,说明桉树较易受到砷的毒害。(4)低浓度砷胁迫时,桉树的抗氧化酶系统和疏基物质的螯合作用能缓解砷对桉树的毒害作用。低浓度砷胁迫7 d时,桉树根中抗氧化酶SOD、CAT和POD活性增加,减缓过氧化物积累,缓解膜脂过氧化程度。高浓度砷胁迫时,根中SOD和CAT活性较最高值显著性降低,叶中CAT和POD活性较对照显著性降低,大量过氧化物积累,抗氧化酶系统对氧化损伤的缓解作用大大降低。低浓度砷胁迫时,桉树根和叶中巯基物质NPT、GSH和PCs含量增加,巯基物质的螯合作用对桉树抵抗砷胁迫的毒害有重要意义。砷胁迫14 d时,随砷胁迫浓度的增加根中PCs含量显著性减少,PCs对砷的螯合作用和解毒能力降低。
[Abstract]:In this paper, eucalyptus was used as experimental material to study the effects of arsenic stress on biomass, chlorophyll and malondialdehyde (MDA) content in eucalyptus. The contents of antioxidant enzyme system (superoxide dismutase (SOD), catalase (catalase) and peroxidase (POD), some sulfhydryl substances (non-protein mercapto (NPT), glutathione (GSH) and plant chelate (PCS) in eucalyptus (Eucalyptus) were also affected. The distribution and chemical forms of arsenic in the roots and leaves of eucalyptus were studied. The detoxification mechanism of arsenic in eucalyptus was discussed from the subcellular distribution and chemical form of arsenic, as well as the antioxidant enzyme system and the chelation of sulfhydryl substances in eucalyptus. The main results are as follows: (1) the high concentration of arsenic can significantly inhibit the growth of eucalyptus and cause strong oxidative damage to eucalyptus. The biomass of root, stem and leaf of eucalyptus and the content of MDA in root and leaf of eucalyptus under 5 mg/L and 10 mg / L low concentration of arsenic stress were not significantly different from those of the control, indicating that the low concentration of arsenic stress had no obvious toxic effect on eucalyptus. Under the stress of 20 mg/L and 30 mg / L, the biomass and chlorophyll content of eucalyptus decreased significantly, and the high concentration of arsenic inhibited the growth of eucalyptus. It is an important mechanism of arsenic detoxification for eucalyptus to retain arsenic in roots and limit the absorption of arsenic to eucalyptus. Under arsenic stress, the order of arsenic accumulation in eucalyptus was as follows: root, stem and leaf, and most of arsenic was stored in root, 76.9-88.9. the transport of arsenic from root to shoot was restricted, which could reduce the toxicity of arsenic to eucalyptus. Under arsenic stress, the arsenic accumulation in eucalyptus roots increased first and then remained unchanged with the increase of arsenic concentration. The immobilization of cell wall components to arsenic and the transformation of some arsenic from root to sodium chloride are the important mechanisms of arsenic detoxification in eucalyptus. Under arsenic stress, arsenic in roots and leaves of eucalyptus was mainly distributed in soluble components (66.3-79.9% and 50.6-53.8%, respectively), followed by cell wall components (14.6-23.2% and 35.6-39.9%, respectively). Under arsenic stress, the main forms of arsenic in the root were ethanol extract (29.5-40.00g), deionized water (28.3- 32.3um) and sodium chloride (24.1- 33.8g). With the increase of arsenic stress concentration, the ratio of arsenic in ethanol was first unchanged and then decreased, the proportion of deionized water first increased and then remained unchanged, and the proportion of sodium chloride first decreased and then increased. The combination of some arsenic in roots with pectin or protein increased the ratio of sodium chloride extract and reduced the toxicity of arsenic to eucalyptus to some extent. On the other hand, a large amount of arsenic could not change to a more stable chemical form, which indicated that the antioxidation enzyme system and chelation of the basic substances in eucalyptus could alleviate the toxicity of arsenic to eucalyptus under low concentration arsenic stress. The activities of cat and POD in root of eucalyptus increased after 7 days of low concentration arsenic stress, which slowed down the accumulation of peroxide and alleviated the degree of membrane lipid peroxidation. Under high arsenic stress, the activities of SOD and CAT in roots were significantly lower than those in the highest values, the activities of CAT and POD in leaves were significantly lower than those in the control, the accumulation of a large amount of peroxide, and the protective effect of antioxidant enzyme system on oxidative damage was greatly reduced. Under low concentration of arsenic, the contents of sulfhydryl substance (NPTGSH and PCs) in roots and leaves of eucalyptus increased, and the chelation of sulfhydryl compounds was of great significance to the resistance of eucalyptus to arsenic stress. Under arsenic stress for 14 days, the content of PCs in roots decreased significantly with the increase of arsenic stress concentration.
【学位授予单位】：广西大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：X173;S792.39

【参考文献】