用氟离子电极零点电位法区分酸性土壤溶液中无机铝离子的形态

本文介绍氛离子电极零点电位法测定强酸性土壤溶液中的游离F^-,并区分无机单核铝离子的形态。结果表明,零点电位法对F^-的检测下限为10^-7 mol/L,在合成的Al-F体系中,该方法的相对误差在±5%范围内。对几种强酸性土壤的研究结果表明,用该方法测定强酸性土壤溶液中的游离F-并区分无机单核铝的形态是可行的。     

有机酸对酸性土壤中铝的溶出和铝离子形态分布的影响

五种低分子量的有机酸对酸性土壤中铝的溶出和铝离子形态分布的影响的研究结果表明，有机酸主要通过与铝形成络合物而促进铝的溶解，使土壤溶液中有机络合态铝浓度增加，有机酸对无机铝形态的影响较小。不同有机酸由于本身的性质和结构不同，它们对铝溶解的影响不同。     

酸铝胁迫对栝楼根系生长及铝积累的影响

针对南方酸性红壤对作物的生长造成的不利影响,采用水培方式,研究酸铝环境0、100、300、500、1000μmol·L-1Al3＋pH4.5,处理7d对长兴栝楼根系生长及铝积累的影响。测定指标包括根系活力、质膜透性、抗氧化酶类活性（过氧化物酶POD、过氧化氢酶CAT、抗坏血酸过氧化物酶APX、愈创木酚过氧化物酶GPX、超氧化物歧化酶SOD）及其同工酶、过氧化氢（H2O2）含量、根尖铝含量的影响。结果表明：随着铝处理浓度升高,根系活力增大,根系质膜透性无显著变化;POD、CAT、APX酶活升高,GPX和SOD活性降低,多种抗氧化酶都有多条同工酶谱带出现;根尖相对铝含量升高,桑色素染色情况显示,荧光梯度与铝含量测定结果一致,并观察到根尖以上根毛处细胞凸起较之平整排列的根细胞更容易积累铝。栝楼对南方酸性红壤具有较强的适应能力,其体内抗氧化酶系统及根尖吸收、积累铝的机制对缓解铝毒害起着重要作用。     

8-羟基喹啉(pH8.3)分光光度法测定酸性土壤中的可溶性铝

8-羟基喹啉(pH8.3)分光光度法对酸性土壤中的可溶性铝测定的研究表明,Al标准曲线的线性范围为0 ~ 50 mmol/L,相关系数R2 = 0.9999,表观摩尔吸光系数为1.995 104 L/(mol·cm),回收率在98.7 % ~ 106.8 %之间,该方法重现性好,选择性高。     

铝毒胁迫下磷对荞麦根系铝形态和分布的影响

以2个荞麦（Fagopyrum esculentum Moench）品种＂江西荞麦＂（铝耐性）和＂内蒙荞麦＂（铝敏感）为材料,采用水培法,研究铝毒胁迫下磷对荞麦根系总铝和单核2种形态以及Al在根尖和细胞壁中的分布情况的影响。结果表明,与200μmol/L Al处理相比,1.0mmol/L磷预处理分别使江西荞麦和内蒙荞麦的相对根长增加了24.4%和35.9%,根系总Al含量分别降低了18.2%和22.5%,根系单核Al含量分别降低了95%和63.2%。根尖细胞壁荧光检测结果为在单Al胁迫下细胞壁的荧光强度最大,1.0mmol/L磷预处理大幅度减弱细胞壁的荧光强度。表明外源磷供应可降低根系总Al和单核Al含量,使毒性形态的铝转化为无毒形态,以及减少Al在根尖以及细胞壁的积累,以缓解Al对根伸长的抑制,提高荞麦根系的抗铝毒害能力。     

有机物料对酸性红壤铝毒的缓解效应

利用盆栽试验研究了施用不等量稻草对酸性红壤旱耕地铝毒的缓解效应。结果表明,添加不等量的秸秆碳(C)后,土壤pH值显著提高,土壤交换性铝和吸附态羟基铝的含量则明显降低,土壤有机络合态铝的含量也呈增加趋势。添加铝盐并不影响秸秆碳对降低土壤交换性铝和吸附态羟基铝含量的作用。在本研究中,土壤pH值与土壤交换性铝和土壤吸附态羟基铝均呈显著负相关,方程分别为y=-2193.9x+11545,R2=0.9798**,y=-655.34x+9748,R2=0.7837**。土壤交换性铝和吸附态羟基铝与玉米主根长,地上部磷、钾含量均呈显著负相关,是抑制玉米吸收养分的主要限制因素,土壤吸附态羟基铝是次于交换性铝的又一活性较大的铝化合物。     

几种典型酸性旱地土壤磷吸附的关键影响因素

以几种典型的酸性旱地土壤为研究对象,测定了土壤磷的等温吸附曲线,描述土壤磷的吸附特征,分析土壤最大吸磷量与土壤理化性质之间的关系,通过通径分析等方法明确了影响磷吸附的关键土壤因素。结果表明:土壤粘粒、游离态氧化铝(Al_d)、非晶质氧化铝(Al_o)及有机络合态铝(Al_p)的含量均与最大吸磷量(X_m)呈极显著正相关(P0.01),土壤pH值与X_m呈极显著负相关(P0.01);非晶质铁铝氧化物含量(Feo+Al_o)与X_m有显著的正相关关系(r=0.62,P=0.01);而土壤有机质、游离态氧化铁(Fe_d)、非晶质氧化铁(Fe_o)及有机络合态铁(Fe_p)的含量对X_m均无显著影响(P0.05)。即在本研究区域内,pH值越低,粘粒含量越高的土壤,其铝氧化物、非晶质铁铝氧化物(Fe_o+Al_o)含量越高,土壤的固磷能力越强。粘粒含量可能是影响土壤吸磷能力的一个最关键因素,其次为游离态氧化铝Al_d、非晶质氧化铝Al_o、有机络合态铝Al_p及土壤pH值等,其中各形态氧化铝对X_m的影响效应主要是通过与粘粒的间接作用来实现。     

板栗壳色素的提取、纯化及稳定性（简报）

该文以板栗壳为材料,研究板栗壳色素的提取、纯化工艺及纯化色素的稳定性,为板栗壳色素的推广应用提供理论基础和实验数据.结果表明,板栗壳色素易溶于碱性水溶液,不溶或难溶于非极性溶剂.用1%的NaOH提取色素,石油醚和乙酸乙酯分别笨取3次后获得粗提色素,粗提色素经醇沉、酸沉及霞结晶法三种方法纯化后通过薄层层析证明色素纯度较高.紫外-可见光谱分析表明,纯化色素的0.01%水溶液在223 nm和264 nm处有明显吸收峰,0.01%甲醇溶液在218 m和264 nm处有明显吸收峰,推测板栗壳色素含有苯环及酚羟基.纯化色素的稳定性试验表明,色素264.nm处吸光度对pH值较敏感.510 nm处吸光度在pH为2.0至6.0时.呈逐渐增加的趋势,在pH为8.0至14.0时变化不大,pH=10.0条件下测定510 nm处吸光度可以作为色素定量的方法;不同金属离子对色素有不同影响;色素对光、热、氧化剂及还原剂的耐受力较强.     

有机酸对铝氧化物吸附磷的影响

以存在不同配位阴离子 (硫酸根、磷酸根、草酸根、柠檬酸根 )时合成的铝氧化物为对象 ,用平衡吸附法研究了草酸、柠檬酸等的浓度和 pH对铝氧化物吸附磷的影响 ,并讨论有机酸影响磷吸附的机制。结果表明 :六种合成铝氧化物的最大吸磷量 (Xm)介于 0.189～ 0.838mmol/g ,以Al(OH)x的吸磷量最高 ,铝 柠檬酸复合物 (Al-CA)的吸磷量最低 ;有机酸浓度升高时 ,铝氧化物的吸磷量降低 ,且柠檬酸的影响程度高于草酸 ;先加 pH为 2的草酸或酒石酸 ,Al(OH)x对磷的次级吸附量最低 ,而有机酸pH为 3时 ,Al(OH)x对磷的次级吸附量达最高 ,有机酸溶液 pH由 4增至 9,铝氧化物吸磷量变化不大或逐渐降低。有机酸与磷混合加入同单加磷相比 ,pH 3时差异较小 ,pH 4～ 6时差异最显著 ,pH 7～ 8时又减小 ;有机酸降低铝氧化物吸磷量的机理包括酸性溶解和络合竞争两方面 ,在 pH 2时以前者为主 ,pH 3～ 9时以后者为主 ,且铝氧化物表面的吸附点位对供试配位阴离子都是亲合的     

铝、镉胁迫对空心菜生长及抗氧化特性的影响

为明确铝(Al)、镉(Cd)胁迫对空心菜植株生长、有害元素积累和抗逆生理代谢的影响,采用营养液培养试验,模拟酸性环境(p H值4.5),对空心菜幼苗进行Al、Cd单一及复合处理3周,测定相关指标。试验结果表明,与对照组相比,单独10μmol·L-1Al和0.5μmol·L-1Cd处理促进空心菜植株生长;高浓度Al(100μmol·L-1)、Cd(5μmol·L-1)胁迫导致植株根系和地上部Al、Cd大量积累,诱导叶片中超氧化物歧化酶(SOD)和过氧化物酶(POD)活性增强,丙二醛(MDA)含量增多;叶片叶绿素含量明显降低,植株生物量大幅下降。Al、Cd复合处理植株各器官有害元素含量均显著高于单一毒害处理,尤其是根系,并诱发更严重的植株生长抑制效应和氧化胁迫,表明Al、Cd对空心菜植株的生长抑制和氧化胁迫具有协同性。本试验研究结果可为Al、Cd复合污染酸性菜园蔬菜安全栽培提供理论指导。     

“绿色革命”以来大气CO2浓度升高对C3作物营养品质的影响

自20世纪60年代"绿色革命"以来,育种技术和农耕技术的发展促进了农作物产量的大幅提升,然而作物的营养品质出现下降趋势。在相似的遗传背景下,大气CO_2浓度升高会使单位体积农作物产品的营养元素含量下降,因此"绿色革命"至今,农作物产品的营养元素下降可能受大气CO_2浓度升高影响。通过植物生长箱模拟"绿色革命"初期和目前的大气CO_2浓度水平(310μmol/mol和400μmol/mol),针对主要C_3作物水稻、小麦和大豆,研究"绿色革命"以来大气CO_2浓度升高对其籽粒的C、N、Fe、Zn元素含量的影响,结果表明:CO_2浓度升高对3种作物籽粒的C元素含量几乎没有影响,变化幅度在±1.5%之间;籽粒的N、Fe、Zn元素含量普遍呈现下降趋势,但均未达到显著水平。     

Potential of wild species for genetic enhancement of some semi-arid food crops

Discovery and incorporation of genes from wild species provide means to sustain crop improvement, particularly when levels of resistance in the cultigens are low and virulent strains of pests and pathogens overcome the host plant resistance. The extent of utilization and the potential of the wild genepool for genetic enhancement were reviewed in five important food crops viz. sorghum, pearl millet, chickpea, pigeonpea and groundnut grown in the semi-arid tropics. Introgression from compatible wild germplasm in the primary gene pool resulted in transfer of new cytoplasmic male sterility systems in pearl millet and pigeonpea, development of high protein, cleistogamous flower and dwarf pigeonpea lines and foliar disease resistant groundnut cultivars. Utilization of wild species in secondary and tertiary gene pools has been generally limited due to sterility, restricted recombination or cross incompatibility. Nevertheless, these species are extremely important as they contain high levels of resistance to several important biotic and abiotic stresses. Several of them, like those belonging to the Parasorghum section and the rhizomatous Arachis species are sources of multiple resistances and hold great promise to sustain crop productivity.     

Faculty positions:Center for Agricultural Resources Research,Chinese Academy of Sciences

正The Center for Agricultural Resources Research(CARR),the Institute of Genetics and Developmental Biology(IGDB),Chinese Academy of Sciences,invites applicants for several research group leader positions.CARR is one of the research organizations in Chinese Academy of Sciences(CAS).We seek nominations and applications     

Collection and preliminary evaluation of native turfgrass accessions in Italy

Despite a raising interest on turfs in Italy, all theavailable varieties of this kind in the Country are of foreign origin, and areoften poorly adapted to the prevailing climatic conditions. This prompted tobegin a collection activity of indigenous turfgrass species, with the ultimategoal of identifying promising materials for future breeding based on localgenetic resources. The collection was carried out in three areas of Italy, viz.the northern Po Plain, the coastal region of Liguria, and the island of Sardiniathat are characterised, respectively, by subcontinental, warm temperate, andtypical Mediterranean climate. Altogether, 141 sites were visited, yielding 226accessions belonging to eight species of potential interest for turfs:Poa pratensis, Poa trivialis,Festuca rubra, Festuca arundinacea,Lolium perenne, Agrostis stolonifera,Agrostis tenuis, and Cynodon dactylon,this last being a warm-season grass. Poa pratensis andCynodon dactylon were mostly collected in northern Italyand Sardinia, respectively, whereas Festuca arundinacea andLolium perenne were rather ubiquitous. The collection sitesranged from 0 to 1040 m asl, but sites over 750 m wereonly visited in the inner part of Sardinia. All the accessions, collected aswhole plants, were transplanted at Lodi, northern Italy, where they are beingevaluated. Their preliminary evaluation for traits of importance for turf use,such as sward colour and overall quality, highlighted the great variation andthe occurrence of interesting accessions in all species. Other characters wererecorded, bearing specific importance in individual species, and in all casespromising accessions were identified. The germplasm of Festucarubra, Festuca arundinacea, and Loliumperenne proved highly infected by endophytic (symbiotic) fungi of thegenus Neotyphodium.     

Leaf position and genotype differences for mineral element concentrations in sorghum grown on tropical acid soil 1

Mineral element deficiencies and toxicities are common problems associated with sorghum [Sorghum bicolor (L.) Moench] production on acid soils. To better understand some of the mineral element problems and the analysis of plant tissue of sorghum plants grown on acid soils, four sorghum genotypes were grown on an acid Oxisol at Carimagua, Colombia limed with dolomite at 2 and 6 Mg ha^‐1.

Samples for mineral element analyses were obtained from leaves at different positions on the four genotypes. Concentrations of P and Mg were highest in the flag leaf (Leaf No. 1) and decreased as the position on the plant declined from the top of the plant for plants grown at 2 Mg lime ha^‐1. Similar decreases in P, Mg, K, and Zn concentrations occurred in plants grown with 6 Mg lime ha^‐1. Concentrations of Ca, S, Si, Mn, Fe, Cu, and Al increased as leaf position declined from the flag leaf for plants grown at 2 and 6 Mg lime ha^‐1. The higher lime supply enhanced Ca and reduced Mn and Fe concentrations in leaves. Differences in mineral element concentrations for the four genotypes used were fairly extensive. The elements to show the greatest range among genotypes were Al and Si and the elements to show the least range among genotypes were P, K, and S. Care should be used in collecting leaf samples for plant analysis and genotypic differences for accumulation of mineral elements should be considered in interpretation of results.     

Short-term variation in the concentration of selected ions within individual tropical rainstorms

Rainwater was collected at the campus of the University of Brunei Darussalam in Bandar Seri Begawan, Brunei Darussalam, using a funnel-in-bottle sampler. Polypropylene bottles were changed at intervals during rainstorm events. The pH and conductivity were determined immediately after collection on aliquots of the sample. Samples were refrigerated at 5°C for subsequent chemical analysis. Analyses for Na, Mg, Ca, Zn and Fe were carried out by means of inductively coupled plasma atomic emission spectroscopy (ICP-AES); Cu and Mn were analysed by graphite furnace atomic absorption spectroscopy (GFAAS); K was analysed using flame atomic emission spectroscopy (FAES); and Cl^–, NO₃ ^– and SO₄ ^2– were analysed by ion chromatography (IC). Concentration versus time profiles are reported for three rainstorm events. All ions exhibited a decrease in concentration during the rainstorm. The first sample contained the highest concentration of ions, consistent with a first-flush effect. The contribution of the initial stages of the shower to the total quantity of ion deposited during the entire rainstorm is quite overwhelming; in many cases 20 to 30% of the mass was deposited in less than 5% of rainstorm duration. On the other hand, the pH and conductivity variation during rainstorms did not exhibit a consistent pattern.     

The 5S rRNA gene diversity in the genus <Emphasis Type="Italic">Secale</Emphasis> and determination of its closest haplomes

We analyzed 127 rDNA sequences (5S DNA units) obtained from 23 seed accession samples from more or less 10 taxa in wild and cultivated rye, genus Secale L. The sequences fell into two known groups, here assigned to two unit classes, viz. long R1 and short R1 (designations to reflect on R haplome of rye). The different taxa could not be fully differentiated based on the 5S DNA units. We searched for 5S DNA sequences from known unit classes most closely similar to the long R1 and the short R1. One set with the long R1 unit class contained sequences of the long P1 unit class from Agropyron (P haplome) and from Kengyilia (StYP haplome), long J1 from Thinopyrum (J haplome), whereas the set with the short R1 included the long S1 from Pseudoroegneria (St haplome) and Kengyilia (StYP haplome), the short J1 from Thinopyrum (J haplome) and the short V1 from Dasypyrum (V haplome). Each of the two sets was analyzed separately by maximum likelihood (ML) phylogenetic analysis from which we were able to infer that the 5S DNA units of Secale differentiated in a non-clock fashion and followed the HKY substitution model in the gene tree with the long R1 unit class and the HKY + G in the gene tree with the short R1 unit class. A complementary Bayesian analysis yielded identical tree topologies to the ML ones for each of the two sequence sets. In the tree with the long R1 units the long P1 and long J1 unit classes were closest to the long R1 unit class, whereas in the tree with the short R1 units the long S1 and short J1 unit classes were closest to the short R1 unit class, indicating possibly a close relationship between the St, J and R haplomes.     

Leaf litter selection by detritivore and geophagous earthworms

Summary Litterbag experiments with 10 different kinds of leaf litter showed that detritivore (Lumbricus species) and geophagous (Aporrectodea species) earthworms prefer certain litter types over others, since different numbers of worms were found below the litter after 50–52 days of exposure in a pasture. The detritivores preferred Fraxinus, Tilia, and predecomposed Ulmus and Fagus litter to Fagus litter and paper, while geophages preferred Tilia litter to Alnus and Ulmus litter, so that the two groups of earthworms showed different preferences. The detritivores seemed to be more selective than the geophages. The palatability of the litter was examined in relation to the C: N ratio, the lignin concentration and the initial and final polyphenol concentration. The numbers of detritivores were significantly correlated with the C: N ratio and the final polyphenol concentration, so that selection of litter seems to be related to palatability. The numbers of geophages were not significantly correlated with any of the parameters for palatability. The disappearance of litter after 50–52 days appeared to be due to detritivore activity, since the numbers found below the litter were positively and significantly correlated with the litter disappearance. There was no significant correlation with geophage activity. This indicates that detritivores use litter as food, and therefore influence the composition of the litter layer.     

Nematode succession and microfauna-microorganism interactions during root residue decomposition

The quality of plant material affects the vigor of the decomposition process and composition of the decomposer biota. Root residues from hairy vetch (Vicia villosa Roth), rye (Secale cereale L.) and vetch+rye, packed in litterbags were placed in pots of soil at 15 C and the content of the bags was analyzed after 2, 4, 8 and 12 weeks. Bacterial biomass did not differ between residues with contrasting composition. Among bacterivores groups of nematodes that require high bacterial production dominated in fast decomposing resources whereas flagellates with smaller requirements prevail in slower decomposing resources. Biomass of bacterial feeding nematodes correlated positively with early phase (0-2 wk) decomposition that increased in the order: rye< vetch+rye<vetch. Bacterial biomass therefore seems to be under top-down (predation) control during early decomposition. In contrast, the fungal biomass differed between resources with highest values for rye. Moreover, this increase in fungal biomass occurred later during succession and was correlated with decomposition activity for rye in that period. Fungal biomass therefore seems to be under bottom-up (resource) control. The composition of the nematode assemblages (composed of 25 taxa) showed a clear relationship to initial plant resource quality as well as decomposition phase. Early successional microbivorous nematodes vary according to resource quality with demanding bacterivores+predators (Neodiplogasteridae) dominating in vetch and less demanding bacterivores (Rhabditidae) and fungivores (Aphelenchus) being equally common in vetch and rye. Later in the succession (2-4 wk) bacterivorous Cephalobidae and fungivorous Aphelenchoides prevailed similarly on the different root materials whereas bacterivorous protozoa and the amoebal fraction thereof dominated in rye. At week 12 no species dominated the nematode assemblages that were similar between the resources. The differences between nematode assemblages among plant resources at 2 week were similar to the results of a field study sampled after 6 weeks with the same soil and plant resources. This lends support to the relevance of the successional patterns observed in this incubation study.     

Cycling of extracellular DNA in the soil environment

Upon entering the soil environment, extracellular DNA is subjected to dynamic biological, physical, and chemical factors that determine its fate. This review concerns the fate of both recombinant and non-recombinant sources of DNA. A schematic of DNA cycling coupled with genetic transformation is presented to understand its behavior in soil. Extracellular DNA may persist through cation bridging onto soil minerals and humic substances, be enzymatically degraded and restricted by DNases of microbial origin, and/or enter the microbial DNA cycle through natural transformation of competent bacteria. Lateral gene transfer may disseminate DNA through the microbial community. An understanding of DNA cycling is fundamental to elucidating the fate of extracellular DNA in the soil environment.