砷超富集植物中砷化学形态其转化的EXAFS研究

通过同步辐射扩展X射线吸收精细结构(SR EXAFS)研究砷超富集植物大叶井口边草(Pteris nervosa)中砷的化学形态及其在植物体中的转化. 结果表明, 在大叶井口边草中砷主要与O配位, 根部存在与谷胱苷肽(GSH)结合的砷, 但是在羽叶中没有发现与GSH结合的砷. 在NaAsO2和Na2HAsO4处理中, 植物根系的砷分别以As(Ⅲ)和 As(Ⅴ)为主, 但是在叶柄和羽叶中砷都以As(Ⅲ)的形态为主. 植物根系吸收的As(Ⅴ)在向上转运的过程中具有向As(Ⅲ)转化的趋势, 其转化过程主要发生在根部. 实验证明, 与GSH结合并不是大叶井口边草中砷解毒的主要机理, 超富集植物可能具有与一般耐性植物不同的重金属解毒机制.     

砷超富集植物中砷化学形态及其转化的EXAFS研究

通过同步辐射扩展X射线吸收精细结构(SR EXAFS)研究砷超富集植物大叶井口边草(Pteris nervosa)中砷的化学形态及其在植物体中的转化。结果表明,在大叶井口边草中砷主要与O配位,根部存在与谷胱苷肽(GSH)结合的砷,但是在羽叶中没有发现与GSH结合的砷,在NaAsO_2和Na_2HAsO_4处理中,植物根系的砷分别以As(Ⅲ)和As(Ⅴ)为主,但是在叶柄和羽叶中砷都以As(Ⅲ)的形态为主,植物根系吸收的As(Ⅴ)在向上转运的过程中具有向As(Ⅲ)转化的趋势,其转化过程主要发生在根部。实验证明,与GSH结合并不是大叶井口边草中砷解毒的主要机理,超富集植物可能具有与一般耐性植物不同的重金属解毒机制。     

砷胁迫对桉树抗氧化酶活性的影响

通过水培实验,研究了砷胁迫对桉树根和叶的生物量,对砷、叶绿素和丙二醛(MDA)含量,以及对超氧化物歧化酶(SOD)、过氧化氢酶(CAT)和过氧化物酶(POD)活性的影响,讨论了桉树抗氧化酶系统在砷胁迫造成的氧化损伤中的作用。实验结果表明桉树叶的砷含量随砷胁迫浓度的增加而增加,根的砷含量高于叶。在低浓度砷(5 mg/L和10 mg/L)胁迫时,生物量及根和叶中MDA含量较对照无显著性差异,根中SOD、CAT和POD的活性增加,过氧化物的积累减缓。在高浓度砷(20 mg/L和30 mg/L)胁迫时,生物量和叶绿素的含量减少,SOD、CAT和POD活性降低,MDA含量显著性增加,桉树遭受较强的氧化损伤。结果表明,在低浓度砷胁迫时,抗氧化酶系统对砷胁迫造成的氧化损伤有较好的缓解作用;在高浓度砷胁迫时,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。     

砷超富集植物中砷化学形态及其转化的EXAFS研究

通过同步辐射扩展X射线吸收精细结构(SR EXAFS)研究砷超富集植物大叶井口边草(Pteris nervosa)中砷的化学形态及其在植物体中的转化. 结果表明, 在大叶井口边草中砷主要与O配位, 根部存在与谷胱苷肽(GSH)结合的砷, 但是在羽叶中没有发现与GSH结合的砷. 在NaAsO₂和Na₂HAsO₄处理中, 植物根系的砷分别以As(Ⅲ)和As(Ⅴ)为主, 但是在叶柄和羽叶中砷都以As(Ⅲ)的形态为主. 植物根系吸收的As(Ⅴ)在向上转运的过程中具有向As(Ⅲ)转化的趋势, 其转化过程主要发生在根部. 实验证明, 与GSH结合并不是大叶井口边草中砷解毒的主要机理, 超富集植物可能具有与一般耐性植物不同的重金属解毒机制.     

基于蕨素聚类分析的凤尾蕨属药用植物化学分类研究

目的:研究凤尾蕨属5种药用植物蕨素类活性成分,为其质量评价、鉴定及亲缘关系研究提供依据,为凤尾蕨属植物化学分类深入研究奠定基础。方法:采用HPLC-DAD测定5种药用植物的石油醚、乙酸乙酯、正丁醇和水部位的蕨素类成分。比较蕨素种类和含量差异,并以蕨素类特征成分及其含量为分类性状,采用聚类分析对凤尾蕨属药用植物进行化学分类研究。结果:从大叶井口边草、半边旗、全缘凤尾蕨、蜈蚣草和凤尾草中分别检测出蕨素类成分59、39、3、7和22个,总体来看大叶井口边中蕨素类成分含量最高,而全缘凤尾蕨中蕨素类成分含量最低。运用系统聚类将5种药用植物聚成3类:第Ⅰ类为全缘凤尾蕨、蜈蚣草和凤尾草;第Ⅱ类为半边旗;第Ⅲ类为大叶井口边草。结论:半边旗与全缘凤尾蕨、蜈蚣草和凤尾草之间的化学亲缘关系较远。蕨素聚类结果与传统分类结果有较好的一致性。蕨素类成分HPLC-DAD图谱可用于凤尾蕨属植物的鉴别和分类研究,并可为其质量评价提供重要参考。     

高砷区植物的生态与化学特征

 土壤砷污染是一种十分严重的环境问题,但目前尚无经济有效的治理方法。利用各种重金属的耐性与富集植物修复重金属污染土壤是当前的研究热点。通过对两个中国典型的砷矿区（炼砷区）土壤与植物的系统调查与采样分析,发现若干种植物对砷具有极强的耐性和不同程度的富集能力。砷在不同植物中的含量分别为：蜈蚣草（Pteris vittata）羽片1 600 mg·kg-1 DW,剑叶凤尾蕨(Pteris ensiformis)地上部1 230 mg·kg-1 DW,酸模(Rumex acetosa)地上部 440 mg·kg-1     

UV-B辐射增强和O3浓度升高对大豆叶片内源激素和抗氧化能力的影响

揭示大豆叶片内源激素对UV-B和臭氧胁迫的代谢机制和响应方式,为从分子水平研究植物内源激素对UV-B(Ultraviolet-B)和O3(Ozone)胁迫的适应机制奠定基础。以大豆(Glycine max.)为试验材料,利用开顶式气室研究UV-B(0.32W/m2)和O3((110±10)nmol/mol)复合胁迫对大豆叶片内源激素含量及活性氧代谢系统的影响。结果表明:在大豆整个生育期内,与对照相比,UV-B胁迫使大豆叶片ABA(Abscisic acid)含量、ZR(Zeatin riboside)含量和IAA(Indoleacetic acid)含量显著降低,IAA/ABA、ZR/ABA、(IAA+ZR)/ABA比值升高,O·-2(Superoxide anion free radical,O·-2)产生速率和MDA(Malonaldehyde)含量升高,SOD(Superoxide dismutase)、CAT(Catalase)和POD(Peroxidase)活性显著降低;高浓度O3胁迫下,大豆叶片ABA和IAA含量显著下降、ZR含量显著增加,IAA/ABA、ZR/ABA、(IAA+ZR)/ABA值显著升高,O·-2产生速率和MDA含量增加,SOD、CAT和POD活性显著降低;UV-B和O3复合胁迫下,大豆叶片ABA含量、ZR含量和IAA含量降低,ZR/ABA、(IAA+ZR)/ABA值下降,而IAA/ABA值升高,O·-2产生速率和MDA含量显著增加,SOD、CAT和POD活性显著降低。UV-B辐射增强和O3浓度升高单一及复合作用使大豆叶片内源激素间平衡改变,进而影响大豆叶片的代谢水平。持续胁迫下,植株抗氧化能力下降,对大豆表现为伤害效应。UV-B和O3复合胁迫比单独胁迫时的影响有所加深,但是小于两者单独作用时影响的简单累加。     

大叶井边草——一种新发现的富集砷的植物

自1999年以来对位于湖南省一些高砷区的植物和土壤进行了一系列的野外调查,以着力寻找砷的超富集植物。结果表明,与砷超富集植物蜈蚣草同属的另一种植物－－大叶井口边草,对砷也具有显著的富集特征。这一发现为研究揭示砷在植物中的超富集机理提供了一种新的材料,建议深入开展蜈蚣草与大叶井口边草这两种砷富集植物的对比研究。     

大叶井口边草——一种新发现的富集砷的植物

自 1 999年以来对位于湖南省一些高砷区的植物和土壤进行了一系列的野外调查 ,以着力寻找砷的超富集植物。结果表明 ,与砷超富集植物蜈蚣草同属的另一种植物——大叶井口边草 ,对砷也具有显著的富集特征。这一发现为研究揭示砷在植物中的超富集机理提供了一种新的材料。建议深入开展蜈蚣草与大叶井口边草这两种砷富集植物的对比研究。     

杜鹃对SO2胁迫的抗氧化防护效应

以SO2耐受性植物杜鹃(Rhododendron sp.)为材料,在2个高浓度SO2熏气后,检测了叶组织中丙二醛(MDA)、可溶性蛋白和叶绿素含量以及抗氧化酶活性.结果表明:40和80mg?m-3SO2熏气4h(1d)后,杜鹃叶片超氧化物歧化酶(SOD)活性和MDA含量均分别比对照显著增加了11.26%、11.86%和73.32%、76.43%;随熏气时间的延长,SOD、过氧化物酶(POD)、过氧化氢酶(CAT)活性持续增高,且SOD和CAT活性显著高于对照,MDA含量逐渐降至对照水平;SO2熏气导致叶片可溶性蛋白含量显著降低,但叶绿素含量却无显著改变.熏气后恢复期间,抗氧化酶活性相对降低,可溶性蛋白含量恢复至对照水平.研究发现,杜鹃对SO2的耐受性与细胞中抗氧化酶活性的诱导性增强有关,抗氧化能力增强是植物适应SO2胁迫的重要原因.     

Effects of indole-3-acetic acid on arsenic uptake and antioxidative enzymes in Pteris cretica var. nervosa and Pteris ensiformis

A hydroponic experiment was conducted to investigate the effects of indole-3-acetic acid (IAA) on arsenic (As) uptake and antioxidative enzymes in fronds of Pteris cretica var. nervosa (As hyperaccumulator) and Pteris ensiformis (non-hyperaccumulator). Plants were exposed to 2 mg L^?1 As(III), As(V) or dimethylarsinic acid (DMA) and IAA concentrations for 14 d. The biomass and total As in the plants significantly increased at 30 mg L^?1 IAA. Superoxide dismutase (SOD) activities significantly increased with IAA addition. Catalase (CAT) activities showed a significant increase in P. ensiformis exposed to three As species at 30 or 50 mg L^?1 IAA but varied in P. cretica var. nervosa. Peroxidase (POD) activities were unchanged in P. ensiformis except for a significant decrease at 50 mg L^?1 IAA under As(III) treatment. However, a significant increase was observed in P. cretica var. nervosa at 10 mg L^?1 IAA under As(III) or DMA treatment and at 50 mg L^?1 IAA under As(V) treatment. Under DMA stress, malondialdehyde contents in fronds of P. cretica var. nervosa showed a significant decrease at 10 mg L^?1 IAA but remained unchanged in P. ensiformis. Therefore, IAA enhanced As uptake and frond POD activity in P. cretica var. nervosa under As stress.     

Characterization of glutathione reductase and catalase in the fronds of two Pteris ferns upon arsenic exposure

To better understand the mechanisms of plant tolerance to high concentration of arsenic, we characterized two antioxidant enzymes, glutathione reductase (GR) and catalase (CAT), in the fronds of Pteris vittata, an arsenic-hyperaccumulating fern, and Pteris ensiformis, an arsenic-sensitive fern. The induction, activation and apparent kinetics of GR and CAT in the plants upon arsenic exposure were investigated. Under arsenic exposure (sodium arsenate), CAT activity in P. vittata was increased by 1.5-fold, but GR activity was unchanged. Further, GR was not inhibited or activated by the arsenic in assays. No significant differences in K_m and V_max values of GR or CAT were observed between the two ferns. However, CAT activity in P. vittata was activated by 200 μM arsenate up to 300% compared to the control. Similar but much smaller increases were observed for P. ensiformis and purified bovine liver catalase (133% and 120%, respectively). This research reports, for the first time, the activation of CAT by arsenic in P. vittata. The increased CAT activities may allow P. vittata to more efficiently mediate arsenic-induced stress by preparing the fern for the impeding production of reactive oxygen species resulting from arsenate reduction to arsenite in the fronds.     

The spores of Pteris cretica complex (Pteridaceae-Pteridophyta) in America

Spore morphology in the Pteris cretica complex, including Pteris brasiliensis, P. ciliaris, P. cretica, P. denticulata var. denticulata, P. denticulata var. tristicula, P. ensiformis, P. multifida and P. mutilata was examined using light and scanning electron microscope. The spores are trilete, triangular to circular in shape, with an equatorial thickening (= cingulum). Equatorial diameter ranges from 29 to 69 μm, and polar diameter from 18 to 53 μm. Exospore is proximally verrucate and distally rugate, with the exception of Pteris ensiformis, which has cones on both polar faces. Perispore is generally less than 1 μm thick, apparently single-layered in section, and translucent under light microscope. Spheroids were frequently observed on the surfaces of both perispore and exospore. Hyaline spores lacking cingulum were found in all specimens. Pteris brasiliensis, P. cretica and P. denticulata exhibit pronounced polymorphism and, in addition to trilete spores these taxa also produce atypical spores such as tetralete, monolete and intermediate types.     

Synergistic effect of auxins and polyamines in hairy roots of <Emphasis Type="Italic">Cichorium intybus</Emphasis> L. during growth,coumarin production and morphogenesis

Hairy roots of Cichorium intybus obtained by infecting with different Agrobacterium rhizogenes strains (LMG-150 and A20/83) were studied for total endogenous indole-3-acetic acid (IAA) levels and indole-3-acetic acid oxidase (IAAO) activity. The roots initiated by LMG- 150 showed higher endogenous IAA levels as well as IAAO activity as compared to the roots from A20/83. Coumarin production in roots obtained by both of these strains strictly correlated with growth, with higher content in the roots obtained by LMG- 150. Moreover roots from LMG-150 showed increased growth index, length of primary roots and number of secondary and tertiary roots. The roots derived from LMG-150 were studied for total endogenous IAA and IAAO activity under the exogenous administration of polyamines and fungal elicitors. The treatment with putrescine (Put) at 1.5 mM level showed maximum endogenous IAA levels and IAAO activity as compared to the control and other polyamine administration, it also supported faster growth in terms of biomass accumulation, and total coumarin production. Of the various treatments, mycelial extract (ME) and culture media filtrate (CMF) of Pythium aphanidermatum and Phytopthora parasitica var. nicotiana, the treatment with 1 % CMF of P. parasitica var. nicotiana, resulted in maximum IAA levels and IAAO activity, which was supported by maximum biomass, coumarin production as compared to the control and other elicitor treatments. Two different regenerants of chicory obtained through A. rhizogenes LMG-150 designated as T-I and T-II, were studied for total endogenous IAA levels and IAAO activity. T-II showed higher titers of IAA with higher activity of IAAO as compared to T-I. Endogenous titer of IAA and IAAO activity was found to be maximum in transformed roots as compared to T-I, T-II, normal roots and normal plants. Our work showed a variation in endogenous auxin levels in these transformed plants. There exists a synergistic effect of endogenous IAA titers and polyamines in regulating root morphogenesis. Fungal elicitors influenced growth and coumarin production and an elicitor preparation of 1 % CMF of P. parasitica var. nicotiana gave spontaneous regeneration of shoots. The implications of these results are discussed.     

Arsenic hyperaccumulation and localization in the pinnule and stipe tissues of the gold-dust fern (Pityrogramma calomelanos (L.) Link var. austroamericana (Domin) Farw.) using quantitative micro-PIXE spectroscopy

Spatial distribution patterns of arsenic (As) in the tissues of a lesser-known As hyperaccumulating fern Pityrogramma calomelanos (L.) Link var. austroamericana (Domin) Farw. (Pteridaceae) have been studied. Quantitative micro-proton-induced X-ray emission (micro-PIXE) spectroscopy was employed to examine As localization in pinnule and stipe cross-sections of this species. In addition, As hyperaccumulation status of P. calomelanos var. austroamericana was compared with the well-known As hyperaccumulating fern Pteris vittata L. Both species were grown in pots under controlled conditions and exposed to four levels of As (0–500 mg As kg⁻¹) for 20 weeks. Pityrogramma calomelanos var. austroamericana accumulated up to 16 415 mg As kg⁻¹ dry weight (DW), however, phytotoxicity symptoms such as necrotic pinnule tips and margins, appeared in fronds with concentrations >3,008 mg As kg⁻¹ DW. Arsenic was readily translocated to fronds, with concentrations up to 75 times greater in fronds than in roots. Quantitative elemental maps of As generated using micro-PIXE analysis revealed that As concentrations in pinnule cross-sections were higher than in stipe cross-sections with concentrations of 3.7 × 10³ and 1.6 × 10³ mg As kg⁻¹ DW, respectively (as determined by region selection analysis; RSA). In pinnules, RSA revealed variable concentrations of As, however did not resolve a clear pattern of compartmentalization across different anatomical regions. In stipe tissues, As concentrations followed the order vascular bundle > cortex > epidermis (as determined by RSA). Our results show that P. calomelanos var. austroamericana is an As hyperaccumulator and has the potential for use in phytoremediation of soils with low levels (up to 50 mg kg⁻¹) of As contamination.     

Effects of arsenic species and concentrations on arsenic accumulation by different fern species in a hydroponic system

Two hydroponic experiments were conducted to evaluate factors affecting plant arsenic (As) hyperaccumulation. In the first experiment; two As hyperaccumulators (Pteris vittata and P. cretica mayii) were exposed to 1 and 10 mg L(-1) arsenite (AsIII) and monomethyl arsenic acid (MMA) for 4 wk. Total As concentrations in plants (fronds and roots) and solution were determined In the second experiment P. vittata and Nephrolepis exaltata (a non-As hyperaccumulator) were exposed to 5 mgL(-1) arsenate (AsV) and 20 mgL(-1) AsIIIfor 1 and 15 d. Total As and AsIII concentrations in plants were determined Compared to P. cretica mayii, P. vittata was more efficient in arsenic accumulation (1075-1666 vs. 249-627mg kg(-1) As in the fronds) partially because it is more efficient in As translocation. As translocation factor (As concentration ratio in fronds to roots) was 3.0-5.6 for P. vittata compared to 0.1 to 4.8 for P. cretica. Compared to N. exaltata, P. vittata was significantly more efficient in arsenic accumulation (38-542 vs. 4.8-71 mg kg(-1) As in thefronds) as well asAs translocation (1.3-5.6 vs. 0.2-0.5). In addition, P. vittata was much more efficient in As reduction from AsV to AsIII (83-84 vs. 13-24% AsIII in the fronds). Little As reduction occurred after 1-d exposure to AsV in both species indicates that As reduction was not instantaneous even in an As hyperaccumulator. Our data were consistent with the hypothesis that both As translocation and As reduction are important for plant As hyperaccumulation.     

Arsenic uptake and accumulation in fern species growing at arsenic-contaminated sites of southern China: field surveys

Aiming at searching for new arsenic (As) hyperaccumulators, field surveys were conducted at 12 As-contaminated sites located in Guangxi and Guangdong Provinces of southern China. Samples of 24 fern species belonging to 16 genera and 11 families as well as their associated soils were collected and As concentrations in plant and soil samples were determined by inductively coupled plasma-atomic emission spectrometry (ICP-AES). The results show that among 24 fern species, Pteris multifida and P. oshimensis can (hyper)accumulate As in their fronds with high concentrations in addition to P. vittata and P. cretica var. nervosa, which have been previously identified as As hyperaccumulators. Total As concentrations in soils associated with P. multifida and P. oshimensis varied from 1262 to 47,235 mg kg(-1), but the DTPA-extractable As concentrations were relatively low, with a maximum of 65 mg kg(-1). Forty-four of 49 samples of P. multifida collected from five sites and 3 of 13 samples of P. oshimensis collected from one site accumulated over 1000 mg As kg(-1) in their fronds and As concentrations in the fronds were higher than those in the petioles and rhizoids. Although As concentrations in the fronds of P. oshimensis (789 mg kg(-1) averaged, range 301-2142 mg kg(-1)) were comparatively lower than those of P. multifida (1977 mg kg9-1), 624-4056 mg kg(-1)), its high aboveground biomass makes it more suitable for phytoremediating As-contaminated soils. Among all the species in Pteris genus studied, Pteris semipinnata accumulated only very low As concentration in its fronds (8 mg kg(-1), 1-18 mg kg(-1)). Further research is needed to study the differences in As uptake and accumulation among fern species in the same or other genera.     

沙生柽柳扦插生根过程插穗相关理化特征分析

选取沙生柽柳半木质化枝条进行苗床扦插,通过实验测定插穗生根过程中内源激素(IAA、GA3、ZR、ABA)含量、可溶性营养物质(糖、蛋白质)含量及相关氧化酶(PPO、POD、SOD、IAAO)活性的动态变化特征,探讨沙生柽柳插穗扦插生根机理。结果表明:(1)沙生柽柳插穗内源激素含量随生根进程而发生变化,其中,IAA含量在扦插35d最大,并出现较大的波动变化;ZR含量在扦插55d前后变化明显,呈现低水平向高水平转化趋势;ABA、GA3含量依次呈先升高后降低再升高的变化过程,并在扦插15d和55d(80d)呈现变化的峰值和谷值。(2)沙生柽柳扦插生根与相关氧化酶活性密切相关,其中,POD、IAAO活性在插穗扦插35d后长时间保持较高水平,直至插穗生根后POD活性明显降低,IAAO活性有所增加;PPO、SOD活性则在插穗扦插15d保持较高活性,且PPO活性的变化均匀,SOD活性的高低交替变化明显。(3)在沙生柽柳扦插生根期间,插穗可溶性糖含量呈现生根前消耗减少与生根后积累增加两大变化过程,可溶性蛋白质含量表现为扦插后逐步积累增加的变化趋势。研究表明,高水平的IAA、ZR和低水平的GA3、ABA共同调控着沙生柽柳插穗生根;IAA能够通过促进插穗POD、PPO、IAAO活性变化来影响生根,较高的POD、IAAO活性可调节插穗IAA水平,高水平的PPO活性则催化插穗IAA-酚酸复合物的形成,进而诱导插穗生根。     

Influence of elevated CO2 and O3 on IAA, IAA oxidase and peroxidase in the leaves of ginkgo trees

This study examined the impacts of elevated CO₂ or O₃ on indole-3-acetic acid (IAA) content, activities of IAA oxidase (IAAO) and peroxidase (POD) in Ginkgo biloba leaves. Plants grown in open-top chambers were exposed to ambient atmosphere (control; C), elevated CO₂ and elevated O₃ from 1 June to 30 September. An increase in IAA content and decrease in IAAO and POD activities were observed in plants exposed to elevated CO₂ compared with C. Elevated O₃ had no significant effect on IAA content and IAAO activity, but increased POD activity during the early days. When trees pre-exposed to elevated CO₂ were transferred to elevated O₃ or C, the increase in IAAO activity resulted in the decrease in IAA content. When trees pre-exposed to elevated O₃ were transferred to elevated CO₂ or C, IAA content, IAAO and POD activities showed no significant changes. The influence of POD activity on the IAA activity was low.     

EXAFS study on arsenic species and transformation in arsenic hyperaccumulator

Synchrotron radiation extended X-ray absorption fine structure (SR EXAFS) was employed to study the transformation of coordination environment and the redox speciation of arsenic in a newly discovered arsenic hyperaccumulator, Cretan brake (Pteris cretica L. var nervosa Thunb). It showed that the arsenic in the plant mainly coordinated with oxygen, except that some arsenic coordinated with S as As-GSH in root. The complexation of arsenic with GSH might not be the predominant detoxification mechanism in Cretan brake. Although some arsenic in root presented as As(V) in Na₂HAsO₄ treatments, most of arsenic in plant presented as As(III)-O in both treatments, indicating that As(V) tended to be reduced to As(III) after it was taken up into the root, and arsenic was kept as As(III) when it was transported to the above-ground tissues. The reduction of As(V) primarily proceeded in the root.