【作者】 黄运湘；

【导师】 廖柏寒； 肖浪涛；

【作者基本信息】 湖南农业大学 ， 植物学， 2006， 博士

【摘要】 在我国土壤镉污染是一个非常严重的环境危胁。高效吸收和高耐镉植物已经被成功地用于镉污染土壤的修复。本论文的主要研究目的是：（ⅰ）研究不同浓度Cd对大豆幼苗生长发育、激素含量及主要逆境生理指标的影响；（ⅱ）Cd在大豆体内的分布、运转规律以及对氮、磷、钾、锌等主要营养元素吸收的影响；（ⅲ）不同类型土壤中Cd的化学形态及其与大豆Cd生物有效性的关系；（ⅳ）不同大豆品种Cd毒害效应及耐Cd差异性；（ⅴ）植物生长调节剂NAA和微量营养元素Zn对大豆Cd毒害的调控效应。结果如下：1．营养液培养试验表明，短时间（5d）低浓度Cd(0.25mg·L^-1)胁迫可促进大豆株高及生物产量的积累，但差异不明显，对大豆幼苗生长素（IAA）、赤霉素（GA₃）和玉米素（Z）的合成有一定的促进作用。随着Cd浓度的增加和胁迫时间的延长，大豆株高和生物产量明显降低，3类激素的合成作用均受到抑制。不同浓度Cd处理均可促进大豆幼苗ABA的合成，且随Cd浓度的升高促进作用加强。2．土壤盆栽试验表明，Cd胁迫抑制大豆叶片IAA和Z的合成，且随Cd浓度的升高，抑制效应加强。对GA₃合成的影响则表现为低浓度下的刺激效应和高浓度下的抑制效应。至花荚期时，大豆叶片Z含量低于幼苗期，而IAA和GA₃含量高于幼苗期，使大豆在生育前期仍保持一定的生长势。对ABA合成的影响表现为明显的刺激效应，且随Cd浓度的升高和胁迫时间的延长而加强。3．大豆不同器官中的Cd浓度以根系最高，根系吸收转运到地上部的Cd主要分布在茎和叶中，荚壳和籽粒中相对较少。除对照外，红壤不同浓度Cd处理大豆根、茎、叶、荚壳、籽粒中Cd浓度比为1：0.48～0.81：0.48～0.80：0.09～0.34：0.09～0.40；河潮土则为1：0.25～0.75：0.22～0.69：0.08～0.33：0.06～0.22。从土壤中Cd的化学形态分析结果看，红壤水溶交换态Cd和生物有效态Cd含量显著高于河潮土，故红壤加Cd处理，大豆表现Cd中毒症状的浓度低于河潮土，表明河潮土的Cd环境容量高于红壤。4．从大豆籽粒中N、P、K、Zn含量的分析结果看，低浓度Cd(≤0.50mg·L^-1)处理，P—Cd之间表现为协同作用，Cd浓度升高则转变为拮抗作用。N—Cd之间在不同浓度Cd处理下均表现为拮抗作用。籽粒中K—Cd在低浓度Cd胁迫下为拮抗作用，但根系中K—Cd却表现为协同作用。籽粒中Zn—Cd在不同浓度Cd处理下均表现为协同作用，但叶片中Zn—Cd则表现为拮抗作用。5．营养液培养试验表明，低浓度Cd刺激了大豆的根系活力，根系对Cd的吸收及Cd向茎叶的转运能力加强，Cd浓度增加，大豆根系活力降低，吸收和转运Cd的能力下降，根系中Cd积累量增加。相关分析表明，当Cd处理浓度≤1.00mg·L^-1时，大豆根系活力（5d）与茎叶和根系中Cd浓度之间具有极显著的正相关关系，其相关系数r分别为0.996^**和0.979^**（n=4）。当Cd处理浓度≥2.50 mg·L^-1时，大豆根系活力（5d）与茎叶和根系中Cd浓度之间则表现为极显著的负相关关系，其相关系数r分别为-0.995^**和-0.993^**（n=3）。6．土壤盆栽试验表明，河潮土和红壤加Cd处理，大豆幼苗期和花荚期叶片丙二醛（MDA）和脯氨酸（PRO）含量在Cd处理浓度低于或等于2.50 mg·kg^-1时随Cd浓度的升高而增加，继续增加Cd浓度，其含量降低，但仍高于对照。红壤加Cd处理，大豆叶片POD活性随Cd处理浓度的升高而增加，至Cd浓度为2.50 mg·kg^-1时，POD活性达最大值，以后又随Cd浓度的升高而下降。河潮土加Cd浓度小于或等于0.50 mg·kg^-1时，大豆叶片POD活性低于对照，增加Cd浓度，POD活性随Cd浓度的升高而增加，且明显高于对照。尽管Cd胁迫导致大豆叶片内MDA含量的增加，但由于POD活性的提高和ABA及PRO含量的增加，使大豆在低浓度Cd胁迫时表现一定的适应能力。7．主成分分析结果表明，Cd胁迫后大豆叶片叶绿素含量的降低率、根系活力、POD活性的增加率以及茎叶、根系中Cd含量能较好地反映不同大豆品种的耐Cd能力，可作为选育抗Cd大豆品种的参考指标。Cd的化学形态分析表明，大豆叶片和根系中的Cd主要以NaCl提取态形式存在，其分别占总提取态Cd量的87.64％和88.40％，其他形态的Cd含量较少。不同化学形态Cd含量的大小顺序在叶片和根系中均为F_NaCl＞F_HAC＞F_H2O＞F_乙醇。大豆的耐Cd能力不仅与植株体内Cd的含量有关，也与Cd的化学形态关系密切。在不同Cd化学形态中，乙醇提取态和水提取态Cd含量低的品种，抗Cd能力较强，含量高的品种抗Cd能力相对较弱。8．外施NAA可提高大豆叶片中硝酸还原酶（NR）活性，降低叶片中游离脯氨酸（PRO）和丙二醛（MDA）含量，可减轻膜脂的过氧化作用和蛋白质的分解。施用锌肥也可降低Cd伤害大豆幼苗丙二醛和脯氨酸含量，对缓解大豆的Cd毒害具有积极的调控作用。更多还原

【Abstract】 Cadmium contamination in soils is a serious environmental threat in China. Theplants with highly efficient Cd uptake and high tolerance have successfully used in Cdremediation in soils. The main objectives of this dissertation were: （ⅰ） to study theeffects of different concentration of Cadmium （Cd） on the growth, the amount ofphytohormones and the stress physiological indexes of Glycine max plants; （ⅱ） toinvestigate the distribution and transportation of Cd in Glycine max organic and theeffects of Cd on uptake of nitrogen. （N）, phosphorous （P）, potassium （K） and Zinc（Zn）; （ⅲ） to study the fractions of Cd in different soils and their bioavailability; （ⅳ） toevaluate the toxic effects of Cd on Glycine max plants and the differentiation ofvarious Glycine max cultivars to Cd tolerances; （ⅴ） to investigate the influences ofexogenous hormone, naphthalene acetic acid （NAA） and micronutrient zinc （Zn）, onCd toxicity. The results showed that:1. The nutrient hydroponic experiments showed that Cd stress with lowconcentrations (0.25 mg L^-1) for a short period （5 days） slightly increased the heightsand biomass of Glycine max plants without significant statistical difference and it alsostimulated the synthesis of indole-3-acetic acid （IAA）, glibberellic acid （GA₃） andzeatin in Glycine max seedlings. However, the heights and biomass of Glycine maxplants thereafter significantly decreased with increasing Cd concentrations andelongating Cd stress period, and the synthesis of above three hormones decreased. Inaddition, all Cd concentrations increased the synthesis of abscisic acid （ABA） inGlycine max seedlings, and this increase enhanced with increasing Cd concentrations.2. The pot experiments showed that Cd stress depressed the synthesis of IAA andzeatin in Glycine max leaves and this depress increased with increasing Cdconcentrations. However, a stimulated synthesis of GA₃ was found at low Cdconcentrations, while a depressed effect was exhibited at high Cd concentrations.Zeatin contents in Glycine max leaves at pod stage were lower than those at seedlingstage. As compared with the seedling stage, higher IAA and GA₃ contents were foundat pod stage, which could maintain a certain growth potential for Glycine max plants.The synthesis of ABA was distinctly stimulated by Cd stress. Moreover, thissimulative effect enhanced with increasing Cd concentrations and elongating Cdstress period. 3. Cadmium concentrations in roots were the highest among different Glycinemax plant parts. Cd uptake by roots was mainly distributed in stems and leaves, butminor Cd in pods and seeds. Except the control treatment, the ratios of Cdconcentrations in roots, stems, leaves, pods and seeds of Glycine max plants for all Cdtreatments were 1:0.48-0.81:0.48-0.80:0.09-0.34:0.09-0.40 in the tested red soil,and 1:0.25-0.75:0.22-0.69:0.08-0.33:0.06-0.22 in the tested alluvial soil.Exchangeable Cd with water and bio-available Cd in the red soil were higher those inthe alluvial soil. Therefore, the critical concentration of Cd toxicity for Glycine maxplants in the red soil was lower than that in the alluvial soil, which indicated thatalluvial soils possesses of greater Cd environmental capacity compared to red soils.4. Interactive effects of N, P, K, Zn contents on Cd contents in Glycine max seedswere investigated in the present study. Phosphorus and Cd showed a synergistic effectat low Cd concentrations (≤0.50 mg L^-1), and an antagonistic effect at increased Cdconcentrations (＞0.50 mg L^-1). Nitrogen and Cd exhibited obviously an antagonisticeffect. Moreover, K and Cd exhibited an antagonistic effect at low Cd concentrationsin Glycine max seeds, but a significant synergistic effect in Glyeine max roots. Zincand Cd exhibited consistently a synergistic effect for all Cd treatments in Glycine maxseeds, but a significant antagonistic effect in Glycine max leaves.5. In nutrient hydroponic experiments, low Cd concentrations stimulated rootactivity of Glycine max plants, enhanced Cd uptake by Glycine max roots and Cdtransportation to the stems and leaves. In reverse, high Cd concentrations decreasedthe root activity, Cd uptake and transportation, but increased Cd accumulation in theroots. When the Cd concentration was lower than or equal to 1.00 mg L^-1, there weresignificantly positive relationships between the root activities （5 days） and the Cdcontents in Glycine max leaves and roots with correlation coefficients （n=4） of 0.996and 0.979, respectively. When the Cd concentration was higher than or equal to 2.50mg L^-1, significantly negative relationships between the root activities （5 days） andthe Cd contents in Glycine max leaves and roots were obtained. Their correlationcoefficients （n=3） were-0.995 and -0.993, respectively.6. Treated with various Cd concentrations in the tested red soil and alluvial soil inpot experiments, the contents of malondialdehyde （MDA） and proline （PRO） ofGlycine max leaves at seedling and pod stages increased with increasing Cdconcentrations until 2.5 mg kg^-1 of external Cd in the soils. Thereafter, these contentsdecreased with increasing Cd concentrations, but were still higher than that in the control treatment. In the red soil, peroxidase （POD） activities in Glycine max leavesincreased with increasing Cd concentrations with a maximum value at 2.5 mg Cd kg^-1soil, but it declined thereafter. In the alluvial soil, when Cd was lower than or equal to0.5 mg kg^-1, Cd treatments showed a lower POD activity of Glycine max leaves thanthe control. However, when Cd concentration was higher than the above value, PODactivity increased with further increasing Cd concentrations, and it was significantlyhigher than that in the control. The results suggest that although Cd stress resulted inthe increased MDA contents in Glycine max leaves, Glycine max plants still exhibitedcertain suitability to Cd stress due to increase of POD activity and ABA and PROcontents.7. The results of the principal component analysis showed that decreased rates ofchlorophyll in Glycine max leaves, root activity, increment rates of POD activity andCd contents in the stems, leaves and roots of Glycine max plants due to Cd stress werewell response to Cd tolerance capacity of different Glycine max varieties, which couldbe used to select Glycine max varieties with high Cd tolerance. The extractive Cd withNaC1 solution was the main Cd form in Glycine max leaves and roots, accounting for87.6 % and 88.4 % of total extractive Cd contents, respectively. Different Cd forms inGlycine max plant leaves and roots were in the following sequence: F_NaCl＞F_HAc＞F_H2O＞F_ethanol. Capacity of Cd tolerance for Glycine max plants was not onlyrelated to Cd contents in the plants, but also to Cd forms. Those Glycine max varietieswith low contents of ethanol and water extractive Cd showed higher Cd tolerance.8. NAA application increased nitratase activities in Glycine max leaves, butdecreased amounts of free PRO and MDA. Lipid peroxidation of cell membrane andprotein decomposition were also alleviated by NAA application. Furthermore, Znapplication decreased MDA and PRO contents in Glycine max seedlings, whichindicated that Zn could alleviate Cd toxicity to Glycine max plants.更多还原