霞多丽苗木中镉的积累、亚细胞分布及化学存在形态

以一年生盆栽葡萄品种霞多丽(Vitis vinifera L.cv.Chardonnay)自根苗及SO4砧嫁接苗为试材,采用CdCl2和CaCl2根部灌入的方法,研究了镉在霞多丽植株内的亚细胞分布和存在形态,以及外源添加氯化钙对植株镉吸收的影响.结果表明:大部分镉积累在霞多丽自根苗及嫁接苗的地下部器官;4 mmol·L-1浓度的CdCl2处理下,镉在自根苗根及根颈部分的积累量占77.1％,在叶片中的积累量占1.4％,而嫁接苗中镉在嫁接口以下部分的积累量高达93.9％,叶片中的积累量仅占0.1％;5 mmol·L-1外源钙缓解了植株对镉的吸收积累,而10mmol ·L-1外源钙则显著增加了植株对镉的吸收积累.镉在根系和叶片中的亚细胞分布规律为细胞壁＞可溶性部分＞细胞器,且在细胞壁中积累50％以上;镉在根系中主要以氯化钠提取态存在,其次为乙酸提取态,去离子水提取态含量最少.随着镉处理浓度的增加,各提取态含量有所变化.     

镉在东南景天中的亚细胞分配

采用差速离心技术,比较研究了Cd在矿山生态型东南景天(Sedum alfredii Hance)根、茎、叶中的亚细胞分布.结果表明:矿山生态型东南景天对Cd具有很好的忍受耐和累积能力,非矿山生态型东南景天则不具有这种能力.Cd在矿山生态型东南景天根、茎、叶各部分的亚细胞分配满足F1(细胞壁部分)>F3(可溶部分)>F2(细胞器及膜)规律,且Cd在细胞壁部分的分配占绝对优势;同时矿山生态型东南景天地上部有很好的Cd累积能力.与众多超累积植物相似的Cd亚细胞分配规律和地上部的良好的Cd累积能力.对此植物的Cd亚细胞分布完全不同于非矿山生态型东南景天的情况作了比较分析,结果显示矿山生态型东南景天很可能是一种新的镉超累积种质资源.     

Pb 在水花生愈伤组织中的超微定位及对矿质元素的影响

水体重金属污染已经成为一个日益严重的环境问题, 了解水体重金属污染原理、处理水体重金属, 已经成为一个必需解决的课题。由于重金属元素具有难降解、易积累、毒性大等特点, 另外还能被水生植物富集吸收进入食物链危害人畜健康。因此, 植物对重金属毒害的抗性机理以及提高植物抗重金属胁迫能力的探索研究越来越引起人们的关注。虽然在铅(Pb2+)胁迫下植物的抗氧化反应已经有了一些报道, 但有关于植物愈伤组织受到重金属胁迫后变化的研究报道较少。鉴于此, 研究将分布广泛的挺水植物水花生进行愈伤组织培养, 克服了光照、温度、水分及植物生长发育在自然状态下的不可控制性, 使实验数据更具重复性和科学性。经过70%酒精30s、5%次氯酸钠10min 和0.1%升汞10min 消毒后, 在激素为6-BA(3.0 mg/L)和NAA(0.2mg/L)的1/2MS 培养基中培养出水花生茎段的愈伤组织并以此作为研究对象, 以常见的污染环境的重金属离子—Pb2+为胁迫因子。研究了在不同Pb 处理浓度(0、0.2、0.4、0.8 和1.6 mmol/L)下愈伤组织对Pb 的积累、亚细胞分布、亚显微定位及矿质元素的影响。结果表明, 随着培养液中Pb 浓度的增加, (1)愈伤组织体内的Pb 含量极显著上升, 富集系数为2341—2681; (2)各亚细胞组分中的Pb 含量都呈逐渐上升的趋势, 但分配比例明显不均, 分布规律为细胞壁>细胞器>可溶性部分, Pb 胁迫与处理浓度间存在显著的剂量—效应关系, Pb在亚细胞分布与对细胞超微结构的损伤关系密切; (3)超微定位观察发现在细胞壁上分布有大量的Pb 颗粒,细胞内膜结构及基质中也都存在Pb; ⑷Pb 对各亚细胞组分中矿质元素的影响不同, 其中抑制了大量元素P、K、Mg 和微量元素Na、Zn、Mn 的吸收; Ca 在细胞壁中先升后降, 细胞器中逐渐减少, 可溶性部分中则是逐渐增加; Fe 和B 在各亚细胞组分中均表现出先升后降; Cu 在前两个组分中总体呈上升趋势, 可溶性部分中则是先升后降; Si 在细胞壁中逐渐减少, 细胞器中呈先升后降的趋势, 而可溶性部分中无法测出。可见, Pb 打乱了各亚细胞组分中离子平衡, 导致愈伤组织正常生理活动紊乱, 这些都是Pb 毒害水花生愈伤组织的主要表现。       

Growth-Promoting Hormone DA-6 Assists Phytoextraction and Detoxification of Cd by Ryegrass

A pot experiment was carried out to study the effect of growth-promoting hormone diethyl aminoethyl hexanoate (DA-6) on Cd phytoextraction and detoxification in ryegrass. Foliar spray of DA-6 significantly enhanced Cd extraction efficiency (P < 0.05), with 1 μM DA-6 the most effective. At the subcellular level, 43–53% of Cd was soluble fraction and 23–46% in cell wall, and 9–25% in organelles. Chemical speciation analysis showed that 52.7–58.5% of Cd was NaCl extractable, 12.1–22.7% ethanol extractable, followed by other fractions. DA-6 alleviated metal toxicity by fixing more Cd in cell wall and decreasing Cd migration in plant. In conclusion, ryegrass tolerates Cd by cell wall compartmentalization along with protein and organic acids combination, and the treatment of 1 μM DA-6 appears to be optimal for enhancing the remediation efficiency of ryegrass for Cd contaminated soil.     

Subcellular distribution,chemical forms,and physiological response to cadmium stress in Hydrilla verticillata

This study investigated the subcellular distribution and chemical forms of cadmium (Cd) in Hydrilla verticillata and the physiological mechanism underlying H. verticillata responses to Cd stress. Hydrilla verticillata was grown in a hydroponic system and was treated with various Cd concentrations (0, 10, 50, 100, 125, and 150?µM) for 7?days. Cadmium analysis of the leaves at the subcellular level showed that Cd was mainly stored in the soluble fraction (77.98–83.62%) and in smaller quantities in the cell wall fraction (11.99–17.30%) and the cell organelles (4.30–4.88%). The Cd taken up by H. verticillata was in different chemical forms. In the leaves and stems, the Cd was mostly extracted using 1?M NaCl and smaller amounts of Cd were extracted using 2% acetic acid. The malondialdehyde content significantly increased at all Cd concentrations, which indicated oxidative stress. The superoxide dismutase, guaiacol peroxidase, and catalase activities were enhanced. The proline, ascorbate, and glutathione contents increased at lower Cd concentrations, but decreased consistently as the Cd concentration rose. These results suggest that H. verticillata can be successfully used in the phytoremediation of Cd-contaminated water.     

蒌蒿对镉的富集特征及亚细胞分布特点

以镉(Cd)富集植物蒌蒿(Artemisia selengensis)为试材, 采用超声波细胞破碎处理和超速离心的方法, 对蒌蒿根和叶中亚细胞水平的Cd分布状况进行研究, 同时测定Cd在蒌蒿不同器官中的富集效果。结果表明, 在30 mg·kg^–1Cd胁迫下, 蒌蒿叶片中Cd的富集浓度是根和茎中的2–3倍, 但因叶片所占植株的生物量比例较小, 其对Cd的积累量远小于茎和根; Cd在蒌蒿叶片细胞壁、胞液和细胞器中含量比为16:5:1。细胞壁固定是叶片对Cd的主要防御机制。随着Cd处理浓度的增加, 细胞壁和胞液中的Cd含量大幅上升, 但细胞器中Cd含量仍维持在较低水平。长时间和高浓度的Cd胁迫可使细胞壁解毒机制失活并诱导细胞器中的Cd含量增加, 导致植株死亡。根中液泡的Cd贮存量较大, 解毒效果显著。     

Exogenous nitric oxide enhances cadmium tolerance of rice by increasing pectin and hemicellulose contents in root cell wall

To study the mechanisms of exogenous NO contribution to alleviate the cadmium (Cd) toxicity in rice (Oryza sativa), rice plantlets subjected to 0.2-mM CdCl₂ exposure were treated with different concentrations of sodium nitroprusside (SNP, a NO donor), and Cd toxicity was evaluated by the decreases in plant length, biomass production and chlorophyll content. The results indicated that 0.1 mM SNP alleviated Cd toxicity most obviously. Atomic absorption spectrometry and fluorescence localization showed that treatment with 0.1 mM SNP decreased Cd accumulation in both cell walls and soluble fraction of leaves, although treatment with 0.1 mM SNP increased Cd accumulation in the cell wall of rice roots obviously. Treatment with 0.1 mM SNP in nutrient solution had little effect on the transpiration rate of rice leaves, but this treatment increased pectin and hemicellulose content and decreased cellulose content significantly in the cell walls of rice roots. Based on these results, we conclude that decreased distribution of Cd in the soluble fraction of leaves and roots and increased distribution of Cd in the cell walls of roots are responsible for the NO-induced increase of Cd tolerance in rice. It seems that exogenous NO enhances Cd tolerance of rice by increasing pectin and hemicellulose content in the cell wall of roots, increasing Cd accumulation in root cell wall and decreasing Cd accumulation in soluble fraction of leaves.     

Alleviation of Cadmium Toxicity to <i>Medicago Truncatula</i> by AMF Involves the Changes of Cd Speciation in Rhizosphere Soil and Subcellular Distribution

Arbuscular mycorrhizal fungi (AMF) can improve plant tolerance to several abiotic stresses, including heavy metals, drought or salinity exposure. However, the role of AMF in alleviation of soil cadmium (Cd)-induced toxicity to plants is still largely unknown. In this study, Cd speciation in soil and subcellular distribution of Cd were used to characterize the roles of application AM fungi in the alleviation of Cd toxicity in alfalfa plants. Our results showed that the addition of Glomus mosseae in Cd contaminated soil (10 mg/Kg) significantly increased soil pH, cation exchange capacity (CEC) and organic matter in rhizosphere soil with Medicago truncatula L., and then account for significantly decreased contents of exchangeable and carbonate-bounded Cd speciation in rhizosphere soil, indicating alleviation of plant toxicity by reduction of bioavailable fractions of Cd. Although there is no significant difference found in Cd accumulation by roots and shoots respectively between Cd and AM-Cd treatments, more portion of Cd was recorded compartmentalization in cell wall fraction of both root and shoot in treatment of Cd with AM application, indicating alleviation of Cd toxicity to plant cell. Herein, application of AM fungi in Cd treatments performed to inhibit the appearance of Cd toxicity symptoms, including the improvement of leaf electrolyte leakage, root elongation, seedling growth and biomass. This information provides a clearer understanding of detoxification strategy of AM fungi on Cd behavior with development and stabilization of soil structure and subcellular distribution of plant.     

镉在互花米草中积累、转运及亚细胞的分布

研究了在不同Cd浓度(0、5、100、200μg·g-1)处理下,互花米草花序、叶、茎、根茎、须根中Cd含量、积累量、转运特征,及Cd在互花米草体内的亚细胞分布。结果表明,Cd在互花米草不同器官中的积累能力存在较大差异。茎、根茎、须根中Cd含量及积累量随处理浓度的增加而升高,其中须根中Cd含量及积累量均高于其他器官。Cd处理浓度为100gμ·g-1时,花序和叶中Cd含量达到最大值,分别为8.65和7.82μg·g-1。在Cd处理浓度为200μg·g-1时,须根中Cd含量可高达390.00μg·g-1,积累量达3200μg·株-1。Cd在互花米草体内转运能力极低,绝大部分Cd积累在地下部位。Cd在互花米草亚细胞中的分布规律为细胞壁>胞液>细胞器。随着Cd处理浓度的增加,Cd在细胞壁中的分配比例增大,胞液中Cd分布比例则相应减小,细胞壁和胞液相互协调,增强互花米草对重金属Cd的耐性。     

Subcellular Distribution and Chemical Forms of Cadmium in the Medicine Food Homology Plant <i>Platycodon grandiflorum</i> (Jacq.) A.DC.

Although Platycodon grandiflorum (Jacq.) A.DC. is a renowned medicine food homology plant, reports of excessive cadmium (Cd) levels are common, which affects its safety for clinical use and food consumption. To enable its Cd levels to be regulated or reduced, it is necessary to first elucidate the mechanism of Cd uptake and accumulation in the plant, in addition to its detoxification mechanisms. This present study used inductively couple plasma-mass-spectrometry to analyze the subcellular distribution and chemical forms of Cd in different tissues of P. grandiflorum. The experimental results showed that Cd was mainly accumulated in the roots [predominantly in the cell wall (50.96%–61.42%)], and it was found primarily in hypomobile and hypotoxic forms. The proportion of Cd in the soluble fraction increased after Cd exposure, and the proportion of insoluble phosphate Cd and oxalate Cd increased in roots and leaves, with a higher increase in oxalate Cd. Therefore, it is likely that root retention mechanisms, cell wall deposition, vacuole sequestration, and the formation of low mobility and low toxicity forms are tolerance strategies for Cd detoxification used by P. grandiflorum. The results of this study provide a theoretical grounding for the study of Cd accumulation and detoxification mechanisms in P. grandiflorum, and they can be used as a reference for developing Cd limits and standards for other medicine food homology plants.