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1.
猪作为重要的疾病模型动物,目前猪诱导多能干细胞(iPS 细胞)已有建系,但是细胞的冻存和传代的效率较低,影响后续的实验研究。Rho 相关蛋白激酶(ROCK)抑制剂 Y-27632 可提高人胚胎干细胞的解冻存活率,促进其克隆形成。本实验以猪(Sus scrofa)iPS 细胞为研究对象,通过在猪 iPS 细胞冻存和解冻过程中添加Y-27632,发现其可以减少猪 iPS 细胞在冻存和解冻复苏过程中的凋亡。在细胞的传代过程中,使用 Y-27632 可以促进猪 iPS 细胞的贴壁和克隆形成。虽然高浓度 Y-27632 会对猪 iPS 克隆的形态产生一定的影响,但并未影响细胞的碱性磷酸酶(AP)活性和多能性基因 Oct4、Sox2 和 Nanog 的表达水平。最后将转座子报告质粒 PB[Act-RFP]DS 导入猪 iPS 细胞中,经流式筛选后得到的带有红色荧光的细胞,并将其注射于猪孤雌胚胎中进行发育能力检测,发现 Y-27632 的处理能减少细胞在流式筛选和胚胎注射中的凋亡,促进其在胚胎内的嵌合发育。研究结果说明,ROCK 抑制剂 Y-27632 可以提高猪 iPS 细胞冻存和传代的效率,促进其在胚胎中的嵌合。该研究有助于猪 iPS 细胞及其他多能干细胞的保存,传代和筛选等相关研究。 相似文献
2.
《农业生物技术学报》2014,(9)
正动物干细胞与胚胎工程研究,在家畜繁殖育种和转基因动物克隆方面发挥着重要作用,同时补充了转化医学研究无法开展的工作。本期特设了"动物干细胞与胚胎工程"专题,集中展示了该研究领域的部分研究成果,以增进读者对该领域研究进展的了解。多能干细胞是一类具有自我更新能力和多向分化潜能的细胞类群,其主要特性是具有发育成3个胚层细胞和特定功能组织器官的能力。通过体外培养建系获得多能干细 相似文献
3.
牛胚胎干细胞建系研究进展及存在问题 总被引：2，自引：0，他引：2
牛胚胎干细胞具有重要的生物学意义和广阔的应用前景。回顾了牛胚胎干细胞的研究进展，阐述了牛胚胎干细胞生物学特征与表面抗原标志、建系方法和技术路线，系统分析了影响牛胚胎干细胞分离克隆的各种重要因素，并对目前建系中所面临的主要问题进行了探讨。 相似文献
4.
猪转录因子Nanog高效表达、多克隆抗体制备及其应用 总被引：1，自引：0，他引：1
多能转录因子Nanog可维持干细胞的自我更新和多向分化潜能.为深入研究猪(Sus scrofa)Nanog在多能性调控网络的作用,本研究制备了鼠抗猪源Nanog多克隆抗体.首先,从猪肾脏中克隆Nanog基因CDS,再将CDS连接到pET32a质粒上,构建重组表达载体pET32a-Nanog.将重组载体转化大肠杆菌(Escherichia coli) Rosetta (DE3),经异丙基-β-d-硫代半乳糖苷(isopropyl-β-d-thiogalactoside,IPTG)诱导表达,优化最佳诱导时间、温度和IPTG浓度等表达条件,获得分子量为57 kD的Nanog重组蛋白.将纯化的Nanog蛋白,免疫C57BL/6小鼠(Mus musculus),6周后获得阳性抗血清,通过Western blot和免疫荧光检测其抗体效价及其特异性.结果显示,在28℃、8 mmol/L IPTG、诱导2.5 h的条件下,可获得高效Nanog重组表达;制备的鼠抗猪Nanog多克隆抗体能特异性识别猪诱导多能干细胞表达的Nanog蛋白.研究结果为猪多能性干细胞的研究提供了有力工具. 相似文献
5.
小鼠胚胎成纤维细胞(mouse embryonic fibroblasts,MEFs)作为胚胎干细胞培养的饲养层细胞,受到细胞代次等因素限制,需要长期反复制备,消耗大量的实验动物。寻找可替代小鼠胚胎成纤维细胞支持干细胞生长增殖的稳定细胞系,对于降低干细胞的培养成本和减少工作量具有重要意义。L-Wnt3a细胞是一个能够稳定向细胞外分泌Wnt3A蛋白的永生细胞系,目前尚不清楚其是否支持小鼠胚胎干细胞的培养。本研究探讨L-Wnt3a作为饲养层细胞对于小鼠(Mus musculus)胚胎干细胞系的建立以及该细胞条件培养液对无饲养层培养小鼠胚胎干细胞的影响。实验结果表明,丝裂霉素C浓度为10μg/mL,作用4 h时,可显著抑制L-Wnt3a细胞的体外生长而不影响细胞的活力。用该细胞制备饲养层,原代分离、培养小鼠胚胎干细胞,成功建立小鼠胚胎干细胞系。利用L-Wnt3a细胞制备条件培养液进行胚胎干细胞的培养,结果显示,L-Wnt3a条件培养液可支持小鼠胚胎干细胞在无饲养层条件下自我增殖,该条件下培养的胚胎干细胞表达碱性磷酸酶、Oct4、Sox2、Nanog、E-cadherin(E-CAD)和SSEA-1多能性因子,并能够在体内、外分化为3个胚层,形成嵌合体后代。L-Wnt3a细胞作为饲养层细胞,能够成功分离获得小鼠胚胎干细胞,可以避免小鼠胚胎成纤维细胞作为饲养层细胞存在的代数限制、制备繁琐等问题;并且LWnt3a条件培养液可以在无饲养层条件下维持小鼠胚胎干细胞的自我更新,能够在一定程度上有效避免饲养层细胞对胚胎干细胞造成的不利影响。 相似文献
6.
猪诱导多能干细胞(iPS)具有自我更新和多向分化潜能,是医学和细胞生物学研究理想的材料。为了探索猪iPS细胞的胚胎嵌合能力,本实验采用piggyBac转座子系统PB[Act-RFP]DS和Act-PBase载体,共转染猪iPS细胞,获得带有红色荧光标记的猪iPS细胞株PS24-R。并通过显微注射方法,将供体细胞PS24-R注入到4~8细胞期的胚胎腔隙,制备嵌合胚胎,待其继续发育至囊胚阶段,统计PS24-R细胞在胚胎中的嵌合情况。结果显示,通过转座子系统piggyBac标记的猪PS24-R细胞能够稳定表达红色荧光,以其作为供体细胞制备猪嵌合胚胎能够有效观察iPS细胞在胚胎中的嵌合情况。将1、5和10个猪PS24-R细胞和1个猪PS24-R细胞团分别注射到猪胚胎中构建嵌合胚胎,随着猪iPS细胞注射数量的增加,注射胚胎的囊胚率逐渐下降,但嵌合比例逐渐升高。同时与孤雌胚胎相比,嵌合胚胎中多能基因OCT4、SOX2和NANOG表达显著提高。由此可见,采用piggyBac转座子标记的猪PS24-R细胞能够在猪早期胚胎发育阶段实现嵌合,为iPS细胞嵌合猪的生产提供了基础资料。 相似文献
7.
羊水干细胞是一种存在于胎儿羊水中Oct4阳性的多能性干细胞.该细胞具有增殖能力强、分化潜能高和免疫原性低等特点,在生物学和医学研究上具有广泛的应用前景.本实验从不同胎龄的猪胎儿标本中分离猪羊水干细胞,并通过诱导其向脂肪细胞分化来检测其多向分化潜能.结果表明,从胎龄为30～70 d的猪胎儿羊水中分离出的羊水干细胞贴壁率高,增殖能力强,活性好,并建立了两株猪羊水干细胞系.经流式细胞仪和RT-PCR检测,猪羊水干细胞表达CD117、CD44、CD166和CD90表面抗原,不表达CD45、CD54和CD34;稳定表达Oct4、Nanog、C-myc和HLA-abc干细胞特异标志基因;转染报告基因载体pOct4-EGFP和pNanog-EGFP后表达绿色荧光;此外,猪羊水干细胞还能够在体外诱导分化为脂肪细胞.研究结果为大动物羊水干细胞的研究提供了可借鉴的材料. 相似文献
8.
利用稳定干扰载体pSuper-cNanog和pSuper-cPouV转染鸡(Gallus gallus)胚胎干细胞(chicken embryonic stem cells,cESCs),观察多能性相关基因cNanog和cPouV下调后cESCs的增殖特性和多能性标记的改变。Real-time PCR检测分析结果显示,cNanog和cPouV两基因的表达量从48 h开始出现显著下降趋势,并随着转染筛选时间的延长而呈现持续显著下降趋势,96 h可达65%以上(P0.05)。下调cNanog和cPouV基因的表达后,cESCs呈现分化形态,细胞增殖速度减慢,隆起逐渐不明显,边缘不整齐。待筛选后培养至96 h时,干扰cNanog基因的细胞多能性标记碱性磷酸酶(alkline phosphatase,AKP)和阶段特异性胚胎抗原1(stage-specific embryonic antigen-1,SSEA-1)均不表达,而干扰cPouV基因的细胞中则仍有部分表达。将下调cPouV基因的cESCs再次用pSuper-cNanog转染,培养48 h多能性标记AKP和SSEA-1均不表达。结果说明,cNanog和cPouV基因在维持鸡胚胎干细胞多能性和自我更新中起重要作用,且cNanog基因占主导地位。本研究为研究家禽胚胎发育的分子机制以及家禽胚胎干细胞体外培养时自我更新和多能性维持的分子机制提供理论依据。 相似文献
9.
建立含有TetO-FUW-OSKM和FUW-M2rtTA的第二代猪(Sus scrofa domesticus)成纤维细胞,使其在添加强力霉素(doxycycline,DOX)而无需再次感染病毒的条件下可以重编程。将慢病毒(Lentiviral)质粒四环素调控基因(TetO)-FUW-OSKM和FUW-M2rtTA同时感染猪胎儿成纤维细胞(porcine embryonic fibroblasts,PEF),在添加DOX的培养条件下,形成诱导多能干细胞(induced pluripotent stem cells,iPSCs)。随后,将iPSCs通过形成拟胚体(embryoid body,EB)再分化为成纤维样细胞,即TetO-PEF细胞。TetO-PEF携带TetO-FUW-OSKM和FUW-M2rtTA两个载体,且外源四因子拷贝数一致,在+DOX条件下调控四因子表达,直接驱动细胞重编程。本研究建立了TetO-PEF细胞系,为优化猪iPSCs培养条件提供了新的细胞资源。 相似文献
10.
多能干细胞(pluripotent stem cells,PSCs)包括从胚胎内细胞团中分离出的胚胎干细胞(embryonic stem cells,ESCs),外胚层干细胞(epiblast stem cells,EpiSCs),从原始生殖细胞(primordial germ cells,PGCs)分离出的胚胎生殖细胞(embryonic germ cells,EGCs)和诱导多能干细胞(induced pluripotent stem cells,iPSCs).这些细胞都具有向各种类型细胞发育的潜能,因此,PSCs为再生医学的发展,人类基因疾病的动物模型的建立,异种器官移植和高质量抗病新品种的培育提供了有效的途径.迄今为止,PSCs在小鼠(Mus musculus)模型和人类物种已经做了大量研究,同时,家畜的ESCs和iPSCs也取得了有效的进展,表明其不仅可以应用于特定家畜优良品性的稳定遗传和优育,而且可以以家畜为载体生产人类需要的化学药品和抗体,甚至应用在人类疾病的临床前应用中.然而,家畜的ESCs相对来说是难分离和富集的,体外培养建立稳定的ESCs系具有更大的难度和挑战.近年来,得益于对家畜ESCs和相关iPSCs相关的持续研究,已初步揭示了家畜ESCs的独特生物学特性.PSCs已经成为生命科学和高科技农业和生物学一个创新的研究领域.在本文中,本文综述了家畜PSCs的发展历程与应用前景. 相似文献
11.
低氮和干旱胁迫对富士和秦冠生长及氮素利用的影响 总被引：2，自引：2，他引：0
【目的】以富士（Fuji）、 秦冠（Qinguan）嫁接在平邑甜茶（Malus hupehensis Rehd.）上的当年生盆栽苗为试验材料,采用砂培方法,研究了缺氮胁迫和干旱对富士和秦冠生长情况、 光合参数、 植株各部位氮磷钾含量及氮素利用效率的影响,分析比较了低氮干旱条件下富士和秦冠生长及氮素利用的差异,以期为果树生产高效肥水利用提供理论指导。【方法】试验共设四个处理: 正常氮正常水（ZZ）、 低氮正常水（DZ）、 正常氮干旱（ZG）、 低氮干旱（DG）。氮素和水分均设置两个水平,分别为正常氮（6 mmol/L NO-3-N）、 低氮（0.3 mmol/LNO-3-N）、 正常供水（保持盆中砂子相对含水量为饱和含水量的80%~85%）、 干旱处理（保持盆中砂子相对含水量为饱和含水量的60%~65%）。【结果】富士和秦冠的生物量（茎和叶）、 株高茎粗等生长指标以及光合速率、 气孔导度、 蒸腾速率均为正常氮正常水（ZZ）＞低氮正常水（DZ）＞正常氮干旱（ZG）＞低氮干旱（DG）,并且相对应处理下秦冠的以上指标均高于富士;正常供水下,缺氮处理使富士、 秦冠的根冠比比正常氮处理均有所增加,富士提高了2.05%,秦冠提高了22.40%。富士和秦冠的氮、 磷、 钾含量均表现出正常氮正常水（ZZ）＞低氮正常水（DZ）＞正常氮干旱（ZG）＞低氮干旱（DG）; 氮、 钾元素含量在植株各部位的分布顺序依次是叶＞根＞茎,磷元素则是根＞叶＞茎;光合氮素利用效率（PNUE）和氮素利用效率表现为秦冠处理之间差异极显著,富士处理之间差异不显著;秦冠的PNUE和NUE明显高于富士,在低氮正常水（DZ）处理下,秦冠氮肥利用率比富士高42.07%,在低氮干旱（DG）处理下高64.14%;低氮胁迫下富士和秦冠的NUE显著提高,并且秦冠提高的幅度高于富士。【结论】施用氮肥能够显著提高富士与秦冠的干物质量,同等水肥条件下,秦冠生长优于富士;水分亏缺会减少叶片对氮的吸收,干旱条件下适度增施氮肥,可提高果树的抗旱能力;低氮干旱胁迫下秦冠的生长指标、 光合指标及氮素利用效率指标均优于富士,表现出较强的抗低氮干旱胁迫的能力。 相似文献
12.
Aleš Lebeda Ivana Doležalová Eva Křístková Barbora Mieslerová 《Genetic Resources and Crop Evolution》2001,48(2):153-164
Staff members of the Department of Botany of Palacký University in Olomouc and Gene Bank Department – Workplace Olomouc, Research Institute of Crop Production in Prague, Czech Republic, conducted an expedition in seven European countries (Austria, Czech Republic, France, Germany, Italy, the Netherlands, Switzerland) in August/September 1999 to collect wild Lactuca spp. germplasm and study its geographic distribution, ecology and biodiversity. During the mission, more than 600 locations were visited resulting in the collection of 602 seed samples (accessions) of wild Lactuca species and 13 seed samples of related genera (Chondrilla and Mycelis). Lactuca serriola f. serriola, L. serriola f. integrifolia, L. saligna and L. viminea subsp. chondrilliflora were prevalent in southern Europe (Italy, France), however, only L. serriola was common in central and western Europe (Austria, Czech Republic, Germany, Netherlands, Switzerland). The greatest diversity of Lactuca species was found in France, where also the most seed samples (165) were collected. The most characteristic habitats with a high density of Lactuca spp. populations were observed along roads and highways, grassy ditches, ruderal communities, and dust-heaps. Natural infections by powdery mildew (Erysiphe cichoracearum) and downy mildew (Bremia lactucae) on some wild Lactuca spp. were observed. Recent observations concerning the geographic distribution, population structure, habitats, and natural occurrence of diseases of Lactuca spp. are discussed. This assemblage of genetic resources of Lactuca spp. can serve as the basis of future studies of species diversification, spatial population structure, plant microevolution, domestication processes, and genetic variability of host-parasite interactions. 相似文献
13.
Kyle Devey Michael Mucalo Gordon Rajendram Joseph Lane 《Communications in Soil Science and Plant Analysis》2015,46(4):72-80
Laser-induced breakdown spectroscopy (LIBS) is a new technique for the analysis of plant material. This study investigates the application of LIBS to pasture-based plant samples. The LIBS measurements were obtained from pelletized pasture samples (100 samples) that had been also analyzed by inductively coupled plasma–optical emission spectroscopy (ICP-OES) following microwave digestion for calibration and comparison purposes. Comparisons for elements sodium (Na), potassium (K), magnesium (Mg), calcium (Ca), manganese (Mn), iron (Fe), copper (Cu), zinc (Zn), boron (B), phosphorus (P), and sulfur (S) showed that LIBS could be used for almost all the standard profile total elements with concentrations down to low mg/kg levels (observed error of Na: 0.024 percent, K: 0.18 percent, Mg: 0.016 percent, Ca: 0.073 percent, P: 0.017 percent, Mn: 31 mg/kg, Fe: 150 mg/kg, Zn: 6.6 mg/kg, and B: 1.1 mg/kg). Elemental analysis at less than mg/kg levels was not possible using LIBS. The elements S and Cu were particularly difficult to analyze with reliability using LIBS at the concentration levels found in the plant samples. Replacing microwave digestion and subsequent ICP analysis with a direct analysis of dried plant samples using LIBS has the potential to improve the productivity and reduce the cost of testing. 相似文献
14.
Thomas Larsen Jesper Luxhøi Jakob Magid Lars Stoumann Jensen Paul Henning Krogh 《Biology and Fertility of Soils》2007,44(1):59-68
We have studied the effect of anaerobically digested (ADMSW) and composted municipal solid waste (CMSW) on mineralization
and foodweb dynamics to verify the hypothesis that ADMSW would immobilize N right after addition to soil in contrast to addition
with CMSW. Another hypothesis was that the mesofauna (enchytraeids and microarthropods) would stimulate N release from the
decomposer community. We measured excretion of -N and urea-N from the mesofauna and hypothesized that enchytraeids would release urea. ADMSW and CMSW were amended to pots
with sandy loam and barley. The pots were divided into treatments with or without mesofauna. Mesofauna, plant N and biomass,
soil N and ergosterol (fungal biomass) were measured over a 113-day period of four equidistant samplings. Soil respiration,
N mineralization and N release by the mesofauna were modelled from concurrent studies. ADMSW- and CMSW-treated soils initially
(<20 days) immobilized N. The amendments did not increase plant growth substantially, and this was probably due to N-limitation
in the early stages of plant growth. Enchytraeid abundance was about three times higher in ADMSW- than CMSW-treated soils,
indicating that ADMSW contained more labile compounds, bacteria, and microfauna. The mesofauna did not affect N-content, but
the cumulated -N excreted by the mesofauna was estimated to be substantial and about one-fifth of total plant N in ADMSW. An explanation
for this discrepancy might be that in the absence of the mesofauna, other members of the detrivore and microbivore community
performed the mesofauna’s function. Neither enchytraeids nor microarthropods excreted urea. 相似文献
15.
《中国生态农业学报》2014,(6)
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 from individuals who have expertise and a record of accomplishment in research areas related to ecology,agro-hydrology, 相似文献
16.
《中国生态农业学报》2014,(7)
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 from individuals who have expertise and a record of accomplishment in research areas related to ecology,agro-hydrology, 相似文献
17.
《中国生态农业学报》2014,(8)
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 from individuals who have expertise and a record of accomplishment in research areas related to ecology,agro-hydrology, 相似文献
18.
M.A. Callaham Jr. J.M. BlairT.C. Todd D.J. KitchenM.R. Whiles 《Soil biology & biochemistry》2003,35(8):1079-1093
The responses of tallgrass prairie plant communities and ecosystem processes to fire and grazing are well characterized. However, responses of invertebrate consumer groups, and particularly soil-dwelling organisms, to these disturbances are not well known. At Konza Prairie Biological Station, we sampled soil macroinvertebrates in 1994 and 1999 as part of a long-term experiment designed to examine the effects and interactions of annual fire, mowing, and fertilization (N and P) on prairie soil communities and processes. For nearly all taxa, in both years, responses were characterized by significant treatment interactions, but some general patterns were evident. Introduced European earthworms (Aporrectodea spp. and Octolasion spp.) were most abundant in plots where fire was excluded, and the proportion of the total earthworm community consisting of introduced earthworms was greater in unburned, unmowed, and fertilized plots. Nymphs of two Cicada genera were collected (Cicadetta spp. and Tibicen spp.). Cicadetta nymphs were more abundant in burned plots, but mowing reduced their abundance. Tibicen nymphs were collected almost exclusively from unburned plots. Treatment effects on herbivorous beetle larvae (Scarabaeidae, Elateridae, and Curculionidae) were variable, but nutrient additions (N or P) usually resulted in greater densities, whereas mowing usually resulted in lower densities. Our results suggest that departures from historical disturbance regimes (i.e. frequent fire and grazing) may render soils more susceptible to increased numbers of European earthworms, and that interactions between fire, aboveground biomass removal, and vegetation responses affect the structure and composition of invertebrate communities in tallgrass prairie soils. 相似文献
19.
I.L. Boyd 《Biological conservation》2010,143(7):1664-1674
“Wicked” problems are those that are complex and that change when solutions are applied. Many conflicts in conservation fall into this category. The study approached the problem of how to constrain the apparent wickedness of a problem in the conservation management of a species by using simple empirical indicators to carry out iterative assessment of the risk to a population and to document how this risk evolves in relation to the addition of new data and the implementation of management actions. Effects of high levels of uncertainty within data and also concerning population structure were examined through stochastic simulation and by exploration of scenarios. Historical trends in the example used, the Steller sea lion, showed rapid declines in abundance in some regions during the 1980s. The current total population is 130,000-150,000 Steller sea lions through Alaska and British Columbia and this number has been stable since about 1990 in spite of regional differences in population dynamics. Regional differences in the sequence of changes in the number of pups and non-pups, suggested that an internal re-distribution of juveniles could have happened between 1980 and 1990. Current productivity also appears close to the long-term mean. Stochastic population projection using various scenarios showed that, based upon this history, the risk of extinction for the population has declined and is below reasonable thresholds for considering the population to be endangered. The trends in risk suggest that management actions taken since 1990 have probably been effective. Consequently, the conservation management objectives for the Steller sea lion are probably being met. The approach provides a mechanism, based upon experience and scenario analysis, for exploring future policy options and may help to constrain the debate amongst stakeholders about the cost-benefit trade-offs associated with different options. 相似文献
20.
Soil-profile distribution of primary and secondary plant-available nutrients under conventional and no tillage 总被引：1，自引：0，他引：1
Nutrient distributions under no tillage (NT) compared with conventional disk-and-bed tillage (CT) management in the warm, humid region of the southeastern USA need to be assessed so that future placement, quantity, and type of fertilizers can be altered, if necessary, to efficiently match crop demands. We determined soil-profile distributions of pH, N, P, S, K, Ca, Mg, Na, Zn, Fe, Mn, and Cu to a depth of 0.9 m at the end of 8.5 years of continuous CT and NT management on a Weswood silty clay loam (fine, mixed, thermic Fluventic Ustochrept) in southcentral Texas. Most dramatic changes occurred within the 0–0.05 m depth, where soil under NT had lower pH, Fe, and Cu than under CT, but greater P, K, Zn, and Mn. Greater P and K under NT than under CT also occurred below the till-zone (0.15–0.3 m). At a depth of 0–0.3 m, soil under NT contained greater amounts of extractable P, K, Zn, Fe, Mn, and Cu than under CT. Nitrogen fertilization had little effect on nutrient distributions, except resulting in greater extractable K at 0–0.05 m and greater nitrate at 0–0.15 m. Few changes in soil-profile distributions were observed for extractable S, Ca, Mg, and Na. Long-term continuous use of NT on this fine-textured, high-fertility (except for N) soil had no apparent adverse effects on nutrient distributions relative to CT, but enhanced conservation and availability of P, K, Zn, Fe, Mn, and Cu near the soil surface where crop roots proliferate. 相似文献