Nicotianamine（NA）在植物中的作用

Nicotianamine（NA）是植物中特有的一种次生代谢物质,它与植物体内多种金属离子螯合,借助特异的运输载体（YSL）,参与植物中金属离子的吸收、运输和平衡。本文就NA的生化性质,生物合成途径,其在植物金属离子吸收、运输、分布中的作用及其特异运输载体的研究进展作介绍。     

宁夏枸杞体细胞胚发生过程中对金属离子的吸收速率和游离氨基酸含量的变化

采用多重示踪技术研究宁夏枸杞 (Lyciumbar barumL .)体细胞胚发生中对多种金属离子的吸收动态及其与游离氨基酸含量变化之间的关系。结果表明 :(1)在枸杞体细胞胚发生中对一些金属离子具有选择吸收特性 ,而且在体细胞胚发育不同时期对同一种金属离子的吸收量也不同 ;(2 )在枸杞体细胞胚发生早期对多数金属离子吸收量迅速增加 ,而后下降。到球形胚期吸收量达到第二个峰值 ,而且金属离子被吸收后提高了体细胞胚发生的频率 ;(3)枸杞体细胞胚发生中游离氨基酸总量从胚性细胞启动期开始下降 ,到胚性细胞形成期到达谷底 ,然后开始上升 ,到多细胞原胚期达到峰值 ,多数游离氨基酸含量变化与金属离子被吸收的量相交叉 ;(4 )外加RbCl和SrCl2 对枸杞体细胞胚发生具有促进作用 ,而且加大了几种游离氨基酸含量变化的幅度。文章讨论了它们之间的关系及其可能的作用机理     

植物锌铁转运蛋白ZIP基因家族的研究进展

金属离子对植物的正常发育至关重要,但过量又会中毒.植物体内的自动调节平衡机制会调节金属离子的吸收和运输,从而控制金属离子的含量.锌铁调控蛋白ZIP( ZRT,IRT-like protein)家族是广泛存在于植物中的转运蛋白,具有Ca2+、Fe2+、Mn2+及Zn2+等多种金属元素的转运功能.了解ZIP转运体在植物中如何发挥离子转运功能,从分子水平认识金属离子缺乏或过量积累的机理有重要意义.综述拟南芥、水稻、大麦、苜蓿和玉米ZIP家族成员及其研究进展.     

枸杞体细胞胚发生中对痕量金属离子吸收的动态研究

以药用植物宁夏枸杞（Lycium barbarum L.)愈伤组织为材料,离体培养诱导体细胞胚发生,采用多重示踪技术和γ射线能谱分析法研究枸杞研究枸杞体细胞胚发生中对多种痕量金属离子的吸收动态,结果表明：（1）体胚发生中对多种痕量金属离子的吸收呈选择性。对多重示踪剂溶液中的23种核素,只吸收了其中的16种（Mn-52,Zn-65,Co-56,Co-60,As-74,mTc-95,Rh-99,V-48,Rb-83,Rb-84,Sr-85,Y-87,Y-88,Zr-88,Zr-89),而对另7种未吸收（Be-7,Tc-96,Ru-97,mRh-101,Sc-46,Ga-67和Cr-51)。（2）吸收呈动态变化,在同一发育期对不同的金属离子吸收率不同,如第10天,大部分金属离子的吸收率在5％／g左右,而se-75,Rb-83,Sr-85,Zr-89的则是10％－30％/g,在不同发育期对同一种金属离子的吸收率不同,如对Se-75的吸收总体呈上升趋势。第5天达第1峰值14％/g。随后缓慢下降,基本稳定,第15天后急剧上升,至第20天达第2个峰值20％／g;随着胚性细胞的分化与分裂,吸收既存在一致性,也存在非一致性。Se-75,Rb-83,Sr-85,Co-56和V－48等核素的吸收趋势相似,基本上呈上升曲线,而Mn-52的吸收趋势则类似正态分布曲线。     

植物对重金属的吸收和分布

植物修复是利用植物来清除污染土壤中重金属的一项技术。该技术成功与否取决于植物从土壤中吸取金属以及向地上部运输金属的能力。植物对金属的吸收主要取决于自由态离子活度。许多螯合剂能诱导植物对重金属的吸收。金属离子在液泡中的区域化分布是植物耐重金属的主要原因。同时,细胞内的金属硫蛋白、植物螯合脓等蛋白质以及有机酸、氨基酸等在金属贮存和解毒方面也起重要作用。本文还论述了重金属在植物体内运输的生理及分子方面的研究进展。     

植物对重金属的吸收和分布

植物修复是利用植物来清除污染土壤中重金属的一项技术。该技术成功与否取决于植 物从土壤中吸取金属以及向地上部运输金属的能力。植物对金属的吸收主要取决于自由态离子活度。许多螯合剂能诱导植物对重金属的吸收。金属离子在液泡中的区域化分布是植物耐 重金属的主要原因。同时,细胞内的金属硫蛋白、植物螯合肽等蛋白质以及有机酸、氨基酸等在金属贮存和解毒方面也起重要作用。本文还论述了重金属在植物体内运输的生理及分子 方面的研究进展。     

植物YSL家族基因研究进展

黄色条纹蛋白(Yellow stripe-like protein,YSL)是广泛存在于植物中的重金属吸收、转运蛋白,主要参与植物Fe~(3+)的吸收及对Fe~(2+)、Zn~(2+)、Cu~(2+)、Ni~(2+)和Mn~(2+)等金属离子的转运。目前,对于黄色条纹蛋白在植物体内的表达模式,亚细胞定位以及突变体等方面的研究揭示了其在植物生长发育过程中的作用。综述了近年来关于YSL基因在植物中的研究进展,旨为研究植物吸收铁的作用机理及生物强化谷物籽粒中的铁含量奠定基础。     

植物S-腺苷甲硫氨酸合成酶的新功能展望

S-腺苷甲硫氨酸合成酶(S-adenosylmethionine synthetase,SAMS)是广泛存在于动植物以及微生物体内的胞内酶,催化S-腺苷甲硫氨酸(SAM)的合成。近年来的研究发现SAM除了作为细胞甲基化供体,还参与多胺、乙烯、麦根酸等的生物合成过程。SAMS基因响应多种环境胁迫,且在根发育、果实成熟和植物衰老方面发挥作用。但关于SAMS与环境胁迫下植物激素代谢的联系还缺少深入研究。SAM是乙烯与氰化物合成的前体,氰化物诱导植物的抗氰呼吸,但关于SAMS与抗氰呼吸的关系还没有报道。SAM参与的合成麦根酸,同时麦根酸与植物根系对金属离子的吸收紧密关联,但关于SAMS在金属离子吸收、运输中的作用还缺少强有力的实验证据。本文就SAMS的基因表达规律、蛋白质结构、参与的细胞代谢通路、抗逆生理功能进行综述,并对其与抗氰呼吸、金属离子转运和植物激素之间的偶联进行预测和展望。     

植物育种学新领域——水生治污植物育种

利用水生治污植物治理水污染已经运用于实际生活之中,如藻类和高等植物.水生治污植物不仅可去除N、P营养物,还可以吸附金属离子,对于吸收有机物也起到了一定作用.虽然对于植物的育种有着越来越深的研究,但是对于水生治污植物,以更高效率吸收污染物为定向目的的育种方法和研究屈指可数,分析了水生治污育种新领域产生的客观条件和近期任务.     

植物重金属超富集机理研究进展

植物超富集重金属机理主要涉及植物对金属离子高的吸收、运输能力,区域化作用及螯合作用等方面,其中跨膜运载蛋白的表达、调控对重金属超富集这一特性起了关键作用。金属阳离子运载蛋白家族主要包括CDF家族、NRAMP家族和ZIP家族等,在超富集植物中已克隆出多个家族的金属运载蛋白基因,这些基因的过量表达对重金属在细胞中的运输、分布和富集及提高植物的抗性方面发挥了重要作用。综述了近年来研究重金属超富集植物吸收、转运和贮存Zn、Ni、Cd等重金属的生理和分子机制所取得的主要进展。     

Translocation of radionuclides of Co, Zn, Se, Rb, Y, Tc, and Re into organs of tomato plant via roots

The translocation of the radionuclides of Co, Zn, Se, Rb, Y, Tc, and Re into red and green fruits, flesh, seeds, rind, calyxes, flower, leaves, and stems via the root of the tomato plant at two different growth stages was studied by a multitracer technique. The contents (%/g) of Co, Zn, Se, and Y in the roots were the highest among the organs, but only small amounts of them were translocated into the aerial parts after 5 d cultivation with a multitracer. In contrast, Rb, Tc, and Re showed rapid translocation into the stems and leaves from the root. In the plants cultivated for 95 d with a multitracer, Zn, Se, and Rb distributed in all of the organs, Co in the organs except for flowers, and Y, Tc, and Re in the limited organs. The translocation ratio of the elements for the edible part of the plants cultivated for 95 d decreased in the order of Rb>Zn>Co≈Se>Tc≈Y>Re. The transfer factor of the elements for tomato fruit was determined to be in the range of 10⁻⁵–10⁻². The characteristic translocation behavior of the elements gives us fundamental information on the assessment of pollutant uptake by the tomato plant.     

Uptake and distribution of trace elements in maturing soybean

The uptake and translocation of trace elements in maturing soybean plants cultivated on soil were studied over 360 h under diurnal conditions after the administration of a multitracer. The contents (%/g) of Co, Se, Rb, Sr, Ru, Rh, and Cs in all the leaves and stems collected from each node increased up to around 200 h after the administration of the multitracer and then decreased with time. The contents of Zn, Tc, and Re in the leaves and Zn in the stems continuously increased up to 360 h, but Tc and Re in the stems showed maximum content. This observation suggests the translocation of these elements from old leaves to growing leaves via stems. The relationship between the content (%/g) of an element in the seeds and pods, and the cultivation time varied depending on the kind of element and on the growth steps. Mathematical analyses were applied to the behavior of the elements in the soybean. The time dependence of the uptake rate (%/g/h) and distribution of elements in each part of the plant were characteristic of the element.     

Ion competition effects on the selective absorption of radionuclides by komatsuna (Brassica rapa var. perviridis)

The selective absorption coefficient, which is a parameter of an uptake model of radionuclides by plants, was determined for various radionuclides by a multitracer technique. Komatsuna, Brassica rapa var. perviridis, was hydroponically cultivated in a nutrient solution containing a multitracer for 1 day. Nutrient concentration dependence of the selective absorption coefficient of various elements from Be to Re was obtained separately for leaves and roots. The selective absorption coefficients of these elements were, in general, found to decrease with an increase in the concentration of nutrient solutions. Regression equations of the power function for the selective absorption coefficients and the concentration of nutrient solutions were obtained for the leaves and roots. The effects of photon flux and growth stage of plants on the selective absorption coefficients were also studied. It was found that the photon flux influenced the accumulation of radionuclides in the roots but had no significant effect on the selective absorption coefficients for the leaves in 1-day cultivation with the multitracer. The selective absorption coefficients of Mn and Zn in the leaves of the plants at the development stage were higher than those at the maturation stage. For the other elements, no significant effects of the growth stage on the selective absorption coefficients were observed.     

Influence of lanthanum on the uptake of trace elements in cucumber plant

The effects of La³⁺ on the uptake of trace elements (Se, Co, V, and Tc) in cucumber plants were studied by a radioactive multitracer technique. It was observed that the uptake and distribution of these trace elements in roots, stems, and leaves are different under different La³⁺ treatments. Furthermore, in the control, the plant accumulates ⁷⁵Se, ⁵⁶Co, and ⁴⁸V all in the order roots>leaves>stems, whereas ^95mTc was in the order leaves>stems>roots. The accumulations of ⁷⁵Se and ^95mTc in plants treated with different La³⁺ concentration were in the same order as those in the control, but the uptakes percentages of other kinds of element changed differently. The results indicate that lanthanum treatments to a growing cucumber lead to the change of uptake of trace elements, which suggest that a rare earth element is directly or indirectly involved in the ion transport of the plant and affects plant growth by regulating the uptake and distribution of elements that influence the plant cell physiology and biochemistry.     

同位素示踪技术在丛枝菌根真菌生态学研究中的应用

丛枝菌根(arbuscular mycorrhizal,AM)真菌是生态系统中重要的土壤微生物之一。AM真菌菌丝体网络是由AM真菌菌丝体在土壤生态系统中连接两株或两株以上植物根系所形成的菌丝体网络。随着菌根学研究的深入,如何直观的揭示AM真菌的生态学功能已经成为相关领域关注的热点问题。研究发现,利用同位素示踪技术可以开展AM真菌与宿主植物对土壤矿质营养的吸收、转运等方面的研究,以及菌丝体网络对不同宿主植物之间营养物质的分配研究和AM真菌在生态系统生态学中的功能研究。基于此,为了阐明同位素示踪技术在AM真菌研究中的价值,围绕菌根学最新研究进展,系统回顾了利用同位素示踪技术探究AM共生体对不同元素吸收和转运的机制、同位素示踪技术在AM真菌菌丝体网络研究中的价值和利用同位素示踪技术研究AM真菌在生态系统中的功能,为AM真菌生态学功能的研究提供理论基础,并对本领域未来的研究方向和应用前景进行展望。     

基于15N示踪技术的植物-土壤系统氮循环研究进展

同位素示踪技术是指外源添加与生物体内的元素或物质完全共同运行的示踪物,用来指示生物体内某元素或物质变化过程的一种方法。利用氮稳定同位素示踪技术,能从本质上揭示生态学过程发生的机理,从而成为生态学科研工作十分重要的工具之一。对近年来15N示踪技术应用于土壤氮素固定、植物氮素营养和植物-土壤系统氮迁移的研究进展进行了综述,并对稳定氮同位素技术在解决相关生态学难题可能的前景和不足方面进行了展望。     

Uptake and distribution of trace metal elements in wheat seedlings

The uptake and distribution of eight metallic elements were examined in wheat seedlings for a period of 12 d with a radioactive multitracer technique. The radioactive nuclides of the seedlings were simultaneously determined by γ-ray spectrometry. All of the elements studied were taken up by the wheat seedlings and mainly accumulated in the roots. Only some elements were transported to shoots and leaves of the seedlings or bound to leaf proteins, and two elements were transported into the chloroplast. Uptake of most elements reached a maximum on the fifth or the eighth day and then gradually decreased afterward. In the cases of ^95mTc and ⁷²Se, the uptake increased continuously within 12 d without the peak uptake. The change of elemental concentrations was dependent on uptake and excretion rates. The dynamics of metal elements taken up by the wheat seedlings and their distribution in roots, shoots, and leaves were different for each element, suggesting that it may depend on the characteristics of the elements.     

Uptake Rate of Tracer MetalIons by a?Lycium barbaruma?Somatic Embryogenesis

The callus of medical plant Lycium barbarum L. in Ningxia was used as the materials for inducing somatic embryogenesis, and multitracer technique and γ-ray energy spectrum analysis were used for studying the rates of uptake of several tracer metal ions during embryogenesis. The results were: 1) Of 23 radionuclides, only 16 (Mn-52, Zn-65, Co-56, Co-60, As-74, Se-75, mTc-95, Rh-99, V-48, Rb-83, Rb-84, Sr-85, Y-87, Y-88, Zr-88 and Zr-89) were selectively absorbed, the other 7 (Be-7, Tc-96, Ru-97, mRh-101, Sc-46, Ga-67 and Cr-51) were not absorbed. 2) The rates of absorption of different metal ions were different at the same developmental stage. In 10 day culture, the rates of uptake of most metal ions were 5%/g, but that of Se-75, Ab-83, Sr-85 and Zr-89 were 10%-30%/g. The rates of absorption of the same metal ion were different at the same developmental stage, e.g. the rates of uptake of Se-75 were increasing in the course of development, two peaks of absorption appeared in the 5-7th and 15-20th days, being 14%/g and 20%/g. But, around 10th, the uptake rate decreased somewhat. The maximum uptake rate was 20%/g in 20th days. The uptake rates of some metal ions were with the somtimes keeping pace differentiation of embryonic cells. But sometimes not and division. The tendencies of the uptake rates of Se-75, Rb-83, Sr-85, Co-56 and V-48 were similar, indicating that the metal ions were accumulated in the callus during somatic embryogenesis. The uptake rate of Mn-52 was not only similar to other elements, but the variation was like normal distribution.     

Methodological tests of the use of trace elements as tracers to assess root activity

Background and aims

There is increasing interest in how resource utilisation in grassland ecosystems is affected by changes in plant diversity and abiotic conditions. Research to date has mainly focussed on aboveground responses and there is limited insight into belowground processes. The aim of this study was to test a number of assumptions for the valid use of the trace elements caesium, lithium, rubidium and strontium as tracers to assess the root activity of several grassland species.

Methods

We carried out a series of experiments addressing the reliability of soil labelling, injection density, incubation time, application rate and the comparability of different tracers in a multiple tracer method.

Results

The results indicate that it is possible to achieve a reliable labelling of soil depths. Tracer injection density affected the variability but not the mean level of plant tracer concentrations. Tracer application rates should be based on pilot studies, because of site- and species-specific responses. The trace elements did not meet prerequisites to be used in a multiple tracer method.

Conclusions

The use of trace elements as tracers is potentially a very useful tool to give insight into plant root activity at different soil depths. This work highlights some of the main benefits and pitfalls of the method and provides specific recommendations to assist the design of tracer experiments and interpretation of the results.     

Multitracer Screening: Brain Delivery of Trace Elements by Eight Different Administration Methods

Trace elements are closely associated with the normal functioning of the brain. Therefore, it is important to determine how trace elements enter, accumulate, and are retained in the brain. Using the multitracer technique, which allows simultaneous tracing of many elements and comparison of their behavior under identical experimental conditions, we examined the influence of different administration methods, i.e., intravenous (IV), intraperitoneal (IP), intramuscular (IM), subcutaneous (SC), intracutaneous (IC), intranasal (IN), peroral (PO), and percutaneous (PC) administration, on the uptake of trace elements. A multitracer solution containing 16 radionuclides (i.e., ⁷Be, ⁴⁶Sc, ⁴⁸V, ⁵¹Cr, ⁵⁴Mn, ⁵⁹Fe, ⁵⁶Co, ⁶⁵Zn, ⁷⁴As, ⁷⁵Se, ⁸³Rb, ⁸⁵Sr, ⁸⁸Y, ⁸⁸Zr, ^95mTc, and ¹⁰³Ru) was used. The results indicated that the ⁸³Rb brain uptake rate with intranasal administration was approximately twice those obtained with the other administration methods. This result indicated that a portion of Rb was delivered into the brain circumventing the blood circulation and that delivery could be accomplished mainly by olfactory transport. Multitracer screening of trace element delivery revealed differences in brain uptake pathways among administration methods.