钙离子对紫花苜蓿及苜蓿根瘤菌耐酸能力的影响

土壤酸性是阻碍苜蓿根瘤菌与其宿主紫花苜蓿之间高效共生固氮的重要环境因子.本文研究了Ca2 对紫花苜蓿及苜蓿根瘤菌耐酸能力的影响.结果表明:加入一定浓度的Ca2 (5和10mmol·L-1)能提高苜蓿根瘤菌的生长速率,使苜蓿根瘤菌提前进入对数生长期.中性pH条件下,Ca2 的加入对苜蓿根毛变形率无显著影响;低pH条件下,加入2、5和10mmol·L-1的Ca2 均可提高根毛变形率,Ca2 浓度越高,其影响越显著,说明低pH下Ca2 可能会促进苜蓿根瘤菌与其宿主之间的识别.低pH条件下加入Ca2 可以使苜蓿结瘤提前,结瘤率提高;结瘤动力学检测结果表明,加入一定浓度的Ca2 可以使同期结瘤数增加,越是结瘤后期,环境pH越低,这种表现越明显.     

pH对土壤中土著快、慢生大豆根瘤菌结瘤的影响

1　引　　言土壤 ｐＨ对根瘤菌结瘤的影响一直是微生物学和微生物生态学研究的内容之一[4] .在对大豆根瘤菌的研究中 ,早期的研究主要集中于生长慢、产碱的大豆慢生根瘤菌 (Ｂｒａｄｙｒｈｉｚｏｂｉｕｍｊａｐｏｎｉｃｕｍ) [1,2 ] .1982年 ,Ｋｅｙｓｅｒ等[3] 报道了一类生长快、产酸的大豆根瘤菌 ,并命名为费氏中华根瘤菌 (Ｓｉｎｏｒｈｚｏｂｉｕｍ ｆｒｅｄｉ ｉ) .由于它们在生理特性方面存在着明显的差异 ,其结瘤能力以及环境的生物、物理和化学等因素对结瘤的影响一直受到广泛的重视 .本文研究了偏酸、偏碱的 ｐＨ对费氏中华根瘤菌…     

一氧化氮对豆科植物结瘤及固氮的影响机制

豆科植物-根瘤菌共生过程受双方基因复杂且精细的调控, 能够产生特异的根瘤结构并可将大气中的惰性氮气(N₂)转化为可被植物直接利用的氨态氮。结瘤与固氮受多种因素影响, 其中, 一氧化氮(NO)作为一种自由基反应性气体信号分子, 可参与调节植物的许多生长发育过程, 如植物的呼吸、光形态建成、种子萌发、组织和器官发育、衰老以及响应各种生物及非生物胁迫。在豆科植物中, NO不仅影响寄主与菌共生关系的建立, 还参与调控根瘤菌对氮气的固定并提高植株氮素营养利用效率。该文主要从豆科植物及共生菌内NO的产生、降解及其对结瘤、共生固氮的影响和对环境胁迫的响应, 阐述了NO调控豆科植物共生体系中根瘤形成和共生固氮过程的作用机制, 展望了NO信号分子在豆科植物共生固氮体系中的研究前景。     

结合态氮对根瘤菌生长液诱导的苜蓿根毛变形的抑制

以苜蓿根瘤菌和其宿主苜蓿为材料,由结合态氮影响苜蓿根瘤菌生长液诱导宿主根毛变形的功能发现,硝态氮和铵态氮均能有效地抑制根瘤菌生长液诱导的宿主根毛变形。而其抑制作用随结合态氮浓度的增加、作用时间的延长而增强。该抑制作用发生在结合态氮浓度和作用时间分别达到1mmol/L和12h时,或当其浓度和作用时间分别为6mmol/L和48h时,根瘤菌生长液引起根毛变形的植株百分率下降到10％。硝态氮与铵态氮抑制根瘤菌生长液诱导根毛变形的作用相类似。     

胆汁酸盐和低pH值对乳酸菌活性的影响

本文比较了几种乳酸菌对胆汁酸盐的耐受性和ｐＨ值的残活能力。研究结果表明,在０．２％的ＭＲＳ或ＢＭ培养基上,婴儿双歧杆菌的生长速率受到的抑制最小,依次为嗜酸乳杆菌、保加利亚乳杆菌和嗜热链球菌。胆汁酸盐对其生长的完全抑制浓度分别为１．５％、１．２％、０．５％和０．３％。在ｐＨ３时,嗜热链球菌活菌数量降低较为明显,在ｐＨ２时,在３７℃１ｈ过程中,婴儿双歧杆菌活菌数量基本不变;嗜酸乳杆菌在３７℃２０ｍｉｎ后,活菌数量迅速降低;保加利亚乳杆菌数量在３７℃２０ｍｉｎ时几乎为零。     

OsPT6基因过表达对低磷条件下菜用大豆结瘤及固氮的影响

采用砂培方法,以转OsPT6基因的菜用大豆(T3株系)与其非转基因(NT)受体品种为实验材料,研究了两者在低磷条件下的生长发育指标,植株有效磷、全磷、全氮、豆血红蛋白和籽粒蛋白质含量以及谷氨酰胺合成酶活性的差异,并对植株结瘤及固氮相关基因表达进行检测,为阐明转OsPT6基因菜用大豆在低磷条件下结瘤及固氮相关机理提供理论依据。结果显示:(1)转基因植株的株高、茎粗、花数和荚数、根瘤数均显著高于NT植株。(2)转基因植株根、茎、叶及根瘤中有效磷,全株总磷、总氮含量,根瘤中的豆血红蛋白含量、功能叶片中谷氨酰胺合成酶的活性和籽粒蛋白质含量均显著高于NT植株。(3)相关性分析表明,豆血红蛋白含量、谷氨酰胺合成酶活性、总磷、总氮含量4个指标间均呈显著正相关关系。(4)GmENOD40a、GmENOD40b、GmGS1β1、GmGS1β2基因在转基因植株中的表达量显著高于NT植株。研究表明,OsPT6基因过表达增强了菜用大豆在低磷条件下的结瘤及固氮能力,该研究结果为进一步研究其调控机理奠定了基础。     

低pH对番茄幼苗菌根丛枝形成和磷营养功能的影响

以番茄Solanum lycopersicum为宿主,在pH 4.5和pH 6.5条件下分别接种3种丛枝菌根真菌(AMF),即根内球囊霉Rhizophagus irregularis、珠状巨孢囊霉Gigaspora margarita和脆无梗囊霉Acaulospora delicata,探讨低pH对AMF在根系中的丛枝形成和功能的影响。结果表明,低pH能够显著抑制AMF对根系的侵染以及丛枝的形成;3个菌种之间存在差异,表现为珠状巨孢囊霉的侵染强度最高,根内球囊霉的丛枝丰度对低pH最敏感;AMF显著增加番茄的生物量,降低其根冠比;番茄在pH 6.5的菌根依赖性低于在pH 4.5的对应值,对根内球囊霉的菌根依赖性最低;低pH对碱性磷酸酶(ALP)活性的影响与根系侵染有相似的模式;AMF显著提高地上部磷含量,增强根系LePT4的表达,但pH的影响并不显著。以上结果表明,低pH对AMF与植物共生关系的建立和维持有一定的抑制作用,低pH胁迫条件下AMF的促生作用更大,不同AMF菌种/菌株提高植株低pH抗性的能力存在差异。     

大豆结瘤突变体成分的初步分析及其对硝酸还原酶活性和结瘤的影响

超结瘤大豆（Ｇｌｙｃｉｎｅ ｍ ａｘ （Ｌ．） Ｍｅｒｒ．） ｎｔｓ ３８２ 和不结瘤大豆Ｎｏｄ ４９ 的叶和根组织水提取物经Ｓｅｐｈａｄｅｘ Ｇ２５ 过滤、洗脱,再根据洗脱物对硝酸还原酶（ＮＲ）活性的影响可划分为４ 个组分（ｆｒａｃｔｉｏｎ）样品,即ｎｔｓ ３８２（Ｎｏｄ ４９） Ｆ１、ｎｔｓ ３８２（Ｎｏｄ ４９） Ｆ２、ｎｔｓ ３８２（Ｎｏｄ ４９） Ｆ３ 和ｎｔｓ ３８２（Ｎｏｄ ４９） Ｆ４。其中, ｎｔｓ３８２ Ｆ２ 和Ｆ４ 抑制ＮＲ 活性作用在接种ＵＳＤＡ１１０ 后明显下降, 但接种的ｎｔｓ ３８２ Ｆ２ 却能提高大豆Ｂｒａｇｇ 的结瘤数达一倍, 而接种的ｎｔｓ ３８２ Ｆ３ 和Ｆ４ 的作用不明显。ＮＲ 活性抑制因子不是刺激结瘤的因子, 刺激结瘤的因子主要分布在接种的ｎｔｓ３８２ Ｆ２ 部分中。与这一现象相反, Ｎｏｄ ４９ Ｆ２ 和Ｆ４ 抑制ＮＲ活性的作用在接种后更强, 且也抑制大豆ｎｔｓ ３８２ 的结瘤, 其中Ｎｏｄ ４９ Ｆ４ 抑制结瘤的作用基本不能逆转。抑制结瘤因子主要分布在接过种的Ｎｏｄ ４９ Ｆ４ 部分中     

重金属镉（cd）对花生结瘤和生长发育的影响

试验结果表明：重金属镉对“天府９号”、‘鲁花９号”花生品种的结瘤和植株生长均有影响。镉浓度在１００ＰＰＭ下,花生植株根系发育受到抑制,快生型花生根瘤菌株８５—７虽能侵染,但结瘤数量显著减少。     

低pH对鱼类胚胎发育、鱼苗生长及鳃组织损伤影响的研究

本文研究了低pH水平对鱼类的胚胎,鱼苗和鱼种的影响以及鱼鳃的组织学观察。在硬水环境,pH≤4.5时,对泥鳅胚胎发育有严重影响。胚胎在低pH水平下,发育进程明显地迟缓。pH≤5.5时,泥鳅幼苗的生长受到抑制;在软水环境,pH≤4.5时,影响草鱼苗和幼鱼的存活率。低pH水平加上铝则对鱼类呈现出协同毒性。低pH使鱼鳃直接遭受严重的损害:出现大量的粘液、渗血、鳃上皮肿胀和脱落,组织增生和融合。     

The ethylene-inhibitor aminoethoxyvinylglycine restores normal nodulation by Rhizobium leguminosarum biovar. viciae on Vicia sativa subsp. nigra by suppressing the ‘Thick and short roots’ phenotype

Nodulation of Vicia sativa subsp. nigra L. by Rhizobium bacteria is coupled to the development of thick and short roots (Tsr). This root phenotype as well as root-hair induction (Hai) and root-hair deformation (Had) are caused by a factor(s) produced by the bacteria in response to plant flavonoids. When very low inoculum concentrations (0.5–5 bacteria·ml^-1) were used, V. sativa plants did not develop the Tsr phenotype and became nodulated earlier than plants with Tsr roots. Furthermore, the nodules of these plants were located on the primary root in contrast to nodules on Tsr roots, which were all located at sites of lateral-root emergence. The average numbers of nodules per plant were not significantly different for these two types of nodulation. Root-growth inhibition and Hai, but not Had, could be mimicked by ethephon, and inhibited by aminoethoxyvinylglycine (AVG). Addition of AVG to co-cultures of Vicia sativa and the standard inoculum concentration of 5·10⁵ bacteria·ml^-1 suppressed the development of the Tsr phenotype and restored nodulation to the pattern that was observed with very low concentrations of bacteria (0.5–5 bacteria·ml^-1). The delay in nodulation on Tsr roots appeared to be caused by the fact that nodule meristems did not develop on the primary root, but only on the emerging laterals. The relationship between Tsr, Hai, Had, and nodulation is discussed.Abbreviations AVG aminoethoxyvinylglycine - cfu colonyforming units - Had root-hair deformation - Hai root-hair induction - NB naringenin-bacteria filtrate - Tsr Thick and short roots     

水稻响应缺铁的韧皮部汁液蛋白质组学分析

为鉴定水稻(Oryza sativa)响应缺铁的根冠长距离信号转导物质, 采用TMT标记技术分析了不同浓度铁处理下水稻韧皮部汁液的蛋白质组学变化, 共鉴定出206个差异蛋白, 其中54个蛋白表达丰度上调, 152个蛋白表达丰度下调。差异蛋白的KEGG通路分类主要包括激素信号代谢、谷胱甘肽代谢、碳代谢以及mRNA转运等代谢途径。此外, 对差异蛋白对应的生理指标进行测定, 发现激素、蔗糖、谷胱甘肽和转运蛋白等在缺铁条件下变化显著, 后续对这些差异蛋白的功能研究有助于揭示水稻响应铁素营养的长距离信号途径。     

Effects of Low pH on the Induction of Root Hair Formation in Young Lettuce (Lactuca sativa L. cv. Grand Rapids) Seedlings

Received 13 August 1999/ Accepted in revised form 22 December 1999     

宁南山区紫花苜蓿(Medicago sativa)土壤干层水分动态及草粮轮作恢复效应

以各类作物农田水分为对照,连续两年对宁南山区不同生长年限苜蓿深层土壤水分以及10年生苜蓿地耕翻后轮作不同年份作物农田的水分进行了测定.结果表明,随着苜蓿生长年限的增加,干层深度与厚度先增加后减小.3年生苜蓿干层深度为720cm,6年生干层最深可达1000cm以下,10年生干层深度为920cm,3～12年生苜蓿地0～700cm土层基本上均属于土壤干层范围.苜蓿地0～800cm土壤湿度随生长年限增加而降低,2004年测定的4、7年生和12年生苜蓿地0～700cm土层平均含水率分别为5.30%、5.22%和5.01%;2005年测定的3、6年生和10年生苜蓿地0～800cm土层湿度分别为6.26%、5.60%和5.27%;而800～1000cm土层湿度在一定年限后有恢复趋势.300cm为苜蓿地降水下渗的最大临界深度,300cm以下土壤干层一旦形成,将长期存在,7～12年生苜蓿300～700cm土层湿度仅维持在4.0%左右.苜蓿地和农田的土壤干层厚度与湿度有较大差异,草粮轮作可使苜蓿土壤干层水分基本恢复到农田湿度,而且轮作年份越长,土壤各层次水分恢复效果越好,10年生苜蓿轮作18年后土壤水分基本恢复到农田状态.     

Adaptation of plasma membrane H+-ATPase of rice roots to low pH as related to ammonium nutrition

The preference of paddy rice for NH₄⁺ rather than NO₃^- is associated with its tolerance to low pH since a rhizosphere acidification occurs during NH₄⁺ absorption. However, the adaptation of rice root to low pH has not been fully elucidated. This study investigated the acclimation of plasma membrane H⁺-ATPase of rice root to low pH. Rice seedlings were grown either with NH₄⁺ or NO₃^-. For both nitrogen forms, the pH value of nutrient solutions was gradually adjusted to pH 6.5 or 3.0. After 4 d cultivation, hydrolytic H⁺-ATPase activity, V _max, K _m, H⁺-pumping activity, H⁺ permeability and pH gradient across the plasma membrane were significantly higher in rice roots grown at pH 3.0 than at 6.5, irrespective of the nitrogen forms supplied. The higher activity of plasma membrane H⁺-ATPase of adapted rice roots was attributed to the increase in expression of OSA1, OSA3, OSA7, OSA8 and OSA9 genes, which resulted in an increase of H⁺-ATPase protein concentration. In conclusion, a high regulation of various plasma membrane H⁺-ATPase genes is responsible for the adaptation of rice roots to low pH. This mechanism may be partly responsible for the preference of rice plants to NH₄⁺ nutrition.     

A 31P-NMR study of the cross-membrane pH gradient induced by ATP hydrolysis in mitochondria

³¹P-NMR has been used to study the increase of ΔpH in mitochondria by externally added ATP. Freshly prepared mitochondria was treated with N-ethylmaleimide to inhibit the exchange between internal and external P_i. Upon addition of ATP, phosphocreatine (30 mM) and creatine kinase to a NMR sample of mitochondria suspension (approx. 120 mg protein/ml) at 0°C, an increase of ΔpH by approx. 0.5 pH unit was observed. However the increased ΔpH could not be maintained, but slowly decayed along with the increase of external ADP/ATP ratio. Further addition of valinomycin to the suspension induced a larger ΔpH (approx. 1) which was maintained by the increased rate of internal ATP hydrolysis as seen in the growth of the internal P_i peak intensity in NMR spectra and the concomitant decrease of the external phosphocreatine peak. The external P_i and ATP peaks stayed virtually constant. When carboxyatractyloside was added to inhibit the ATP/ADP translocase, the internal P_i increase was stopped and the ΔpH decayed. These observations in conjunction with those made earlier in respiring mitochondria clearly show the reversible nature of the ATPase function in which the internal ATP hydrolysis is associated with outward pumping of protons.     

Correlation between infection by Rhizobium leguminosarum and lectin on the surface of Pisum sativum L. roots

The lectin on the surface of 4- and 5-dold pea roots was located by the use of indirect immunofluorescence. Specific antibodies raised in rabbits against pea seed isolectin 2, which crossreact with root lectins, were used as primary immunoglobulins and were visualized with fluorescein- or tetramethylrhodamine-isothiocyanate-labeled goat antirabbit immunoglobulin G. Lectin was observed on the tips of newly formed, growing root hairs and on epidermal cells located just below the young hairs. On both types of cells, lectin was concentrated in dense small patches rather than uniformly distributed. Lectin-positive young hairs were grouped opposite the (proto)xylematic poles. Older but still-elongating root hairs presented only traces of lectin or none at all. A similar pattern of distribution was found in different pea cultivars, as well as in a supernodulating and a non-nodulating pea mutant. Growth in a nitrate concentration which inhibits nodulation did not affect lectin distribution on the surface of pea roots of this age. We tested whether or not the root zones where lectin was observed were susceptible to infection by Rhizobium leguminosarum. When low inoculum doses (consisting of less than 10⁶ bacteria·ml^-1) were placed next to lectin-positive epidermal cells and on newly formed root hairs, nodules on the primary roots were formed in 73% and 90% of the plants, respectively. Only a few plants showed primary root nodulation when the inoculum was placed on the root zone where lectin was scarce or absent. These results show that lectin is present at those sites on the pea root that are susceptible to infection by the bacterial symbiont.Abbreviations FITC fluorescein isothiocyanate - TRIC tetramethylrhodamine isothiocyanate     

生长素和乙烯互作调控硝酸铵诱导的根毛分叉

以野生型拟南芥(WT)及其生长素和乙烯不敏感型突变体(aux1-7、axr1-3、etr1-1和etr1-3)为实验材料,采用固体培养法研究了高浓度硝酸铵对根毛发育的影响,以揭示其调控根毛发育的机制。结果表明:(1)随着外源硝酸铵浓度的逐渐增加,拟南芥根毛伸长受阻,产生大量的分叉根毛。(2)高浓度硝酸铵条件下,外源活性氧或活性氧产生抑制剂二苯基氯化碘(DPI)的添加能抑制高浓度硝酸铵诱导的分叉根毛产生。(3)高浓度硝酸铵条件下,外源生长素或乙烯合成前体物质1-氨基-环丙烷-1-羧酸(ACC)处理能恢复根毛的正常生长,解除高浓度硝酸铵诱导根毛分叉现象。(4)高浓度硝酸铵条件下,外源生长素处理乙烯不敏感型突变体或ACC处理生长素不敏感型突变体均能抑制突变体分叉根毛的形成。研究表明,活性氧、生长素和乙烯都参与了高浓度硝酸铵对根毛发育的过程调控;在硝酸铵诱导的根毛分叉中生长素和乙烯存在相互作用,在缺乏生长素信号通路时,乙烯能够发挥补充作用抑制分叉根毛的产生;在缺乏乙烯信号通路时,生长素也可以弥补缺失乙烯的作用抑制根毛的分叉,但是需要更高浓度的生长素才能充分抑制分叉根毛的产生。