间作大豆对甘蔗根际土壤细菌及固氮菌多样性的影响

为探讨间作大豆(Glycine max)对甘蔗(Saccharum officinarum)根际土壤细菌及固氮细菌多样性的影响, 收集和开发固氮菌资源, 筛选高效甘蔗联合固氮体系, 选用3个甘蔗栽培品种‘ROC22’、‘GT21’、‘B8’与大豆品种‘Guizao 2’进行间种栽培, 采用巢式PCR特异扩增细菌16S rRNA基因片段和固氮细菌nifH基因片段, 并结合变性梯度凝胶电泳(DGGE)技术, 对间作大豆的甘蔗根际土壤细菌及固氮细菌进行系统演化和多样性分析。聚类分析结果显示, 间作大豆改变了甘蔗根际土壤细菌及固氮细菌原来的群落组成结构, 尤其对固氮菌群落组成的改变更大, 但对群落物种的优势度影响较小。Shannon-Wiener多样性指数和Simpson多样性指数分析结果表明, 甘蔗-大豆间作显著影响甘蔗根际土壤中细菌和固氮菌的多样性, 其中对固氮细菌多样性的影响较大。不同甘蔗品种的根际土壤细菌和固氮菌在间作大豆条件下表现出不同的多样性, ‘ROC22’和‘GT21’间作处理甘蔗根际土壤固氮细菌的Shannon-Wiener多样性指数显著高于单作处理, 而‘ROC22’与大豆间作处理的甘蔗根际土壤固氮菌多样性最为丰富。在大豆生长盛期, 间作处理的甘蔗根际土壤细菌多样性最为丰富, 不同处理间的差异也最大, 随后下降。总体来看, 甘蔗-大豆间作显著地影响根际土壤细菌和固氮菌的群落结构和群落多样性, 有助于对甘蔗合理间作栽培模式的认识和筛选高效甘蔗联合固氮体系。     

甘蔗器官固氮酶活性及其对接种固氮菌的响应

以巴西固氮甘蔗品种B1、B8和广西主栽甘蔗品种ROC22和ROC16为材料,通过桶栽砂培方法,研究不同品种甘蔗及接种固氮菌R16SH后不同生育期和不同器官(根、茎、叶片、叶鞘)的固氮酶活性.结果显示,4个品种甘蔗及接菌后各器官的固氮酶活性均在伸长初期或伸长盛期达到高峰,且以根和茎较高,叶、叶鞘次之;B1、B8根的接菌效果最佳,其固氮酶活性分别比对照增加13.22%和12.42%,而B1和ROC16茎的固氮酶活性分别比对照提高12.19%和12.02%,叶片提高了8%~9%,叶鞘的固氮酶活性变化最小;4个品种甘蔗固氮酶活性表现为B8>B1>ROC22>ROC16,且品种B8与ROC22和ROC16存在显著或极显著差异;相对于品种ROC22和ROC16,固氮菌R16SH对B1与B8的株高以及B1的茎径有更好的生长诱导效应,且在伸长期表现最明显.研究表明,甘蔗的固氮酶活性在品种、器官及生育期间均存在明显差异,接种固氮菌能不同程度提高各品种器官的固氮酶活性,且各品种根、茎以及B1和B8的叶片固氮酶活性显著或极显著差异增加;巴西固氮甘蔗品种表现出比广西主栽甘蔗品种更强的固氮酶活性,且对接种固氮菌反应更敏感.     

以茎尖组培苗检测甘蔗体内内生固氮菌的固氮活性

以巴西引进的甘蔗品种‘B1’、‘B3’、‘B5’、‘B8’以及广西地区栽培品种‘新台糖16号’和‘桂糖11号’的茎尖进行组织培养,对其继代4次的茎尖组培苗进行有氮与无氮培养比较以及于温室中无氮盆栽品种比较试验的结果表明,经茎尖培养的甘蔗品种其原有的固氮能力不丧失,4个巴西甘蔗品种的固氮能力和在无氮下的生长能力强于广西主栽品种‘新台糖16号’和‘桂糖11号’,无氮培养的巴西甘蔗品种氮含量较高,固氮活性较强,缺氮症状出现时间较迟;无氮盆栽的巴西甘蔗品种株高、分蘖、叶片的固氮活性等均优于‘新台糖16号’和‘桂糖11号’。     

木麻黄和桤木离体根瘤和立地土壤的固氮酶与N2O还原酶活性的研究

为了解非豆科固氮树种的固氮酶和N_2O还原酶(Nos)活性,采用乙炔还原法和乙炔抑制技术对细枝木麻黄(Casuarina cunninghamiana)和江南桤木(Alnus trabeculosa)离体根瘤及立地土壤的两种酶活性进行了研究。结果表明,离体根瘤只在厌氧条件下有固氮酶活性,在好氧条件下有Nos活性。根瘤区根际土和非根瘤区根际土的固氮酶活性在好氧条件大于厌氧条件,Nos活性只表现在厌氧条件下。在好氧条件下,根瘤区根际土和非根瘤区根际土的固氮酶活性无显著差异;根瘤区根际土的Nos活性显著大于非根瘤区根际土。除离体根瘤在好氧条件下不表现固氮酶活性外,细枝木麻黄和桤木的离体根瘤、根瘤区根际土和非根瘤区根际土的固氮酶活性均都大于Nos活性。好氧条件下根瘤区根际土的固氮酶活性与非根瘤区根际土的呈极显著正相关,而厌氧条件下根瘤的固氮酶活性与好氧条件下根瘤区根际土和非根瘤区根际土固氮酶活性、好氧条件下根瘤的Nos活性与厌氧条件下根瘤区根际土和非根瘤区根际土Nos活性均呈极显著负相关。这为研究弗兰克氏菌结瘤植物共生固氮体系对N2O汇强度的影响和调控奠定基础。     

Na2CO3胁迫下甜菜幼苗根际土壤环境因子的变化及其相关性

以两个甜菜品种‘KWS0143’(耐盐碱性强)和‘Beta464’(耐盐碱性较弱)为对象,设置4个Na₂CO₃浓度处理[占土壤质量的0%(CK)、0.4%、0.8%和1.2%],采用盆栽方法研究甜菜幼苗时期植株干质量、根际土壤酶活性和微生物数量的变化.结果表明: 与对照相比,0.4%处理的植株干质量明显增加,而0.8%和1.2%处理显著受到抑制,且处理间差异显著. 不同处理下甜菜幼苗根际土壤脲酶、过氧化氢酶和碱性磷酸酶活性表现出相似的变化规律,0.4%处理酶活性较对照有所增加但不显著;0.8%和1.2%处理则显著降低了酶活性,同时‘KWS0143’的土壤酶活性均高于‘Beta464’.与对照相比,0.4%处理土壤微生物群落没有显著变化;0.8%和1.2%处理的根际土壤细菌、真菌和放线菌数量显著减少,且‘KWS0143’的根际微生物数量高于‘Beta464’.两品种植株干质量、土壤酶和土壤微生物之间呈显著正相关;通径分析表明,‘KWS0143’植株干质量决定系数表现为:放线菌>细菌>过氧化氢酶>脲酶>真菌>碱性磷酸酶,‘Beta464’表现为:放线菌>过氧化氢酶>脲酶>真菌>碱性磷酸酶>细菌.     

Na2CO3胁迫下甜菜幼苗根际土壤环境因子的变化及其相关性

以两个甜菜品种‘KWS0143’(耐盐碱性强)和‘Beta464’(耐盐碱性较弱)为对象,设置4个Na₂CO₃浓度处理[占土壤质量的0%(CK)、0.4%、0.8%和1.2%],采用盆栽方法研究甜菜幼苗时期植株干质量、根际土壤酶活性和微生物数量的变化.结果表明: 与对照相比,0.4%处理的植株干质量明显增加,而0.8%和1.2%处理显著受到抑制,且处理间差异显著. 不同处理下甜菜幼苗根际土壤脲酶、过氧化氢酶和碱性磷酸酶活性表现出相似的变化规律,0.4%处理酶活性较对照有所增加但不显著;0.8%和1.2%处理则显著降低了酶活性,同时‘KWS0143’的土壤酶活性均高于‘Beta464’.与对照相比,0.4%处理土壤微生物群落没有显著变化;0.8%和1.2%处理的根际土壤细菌、真菌和放线菌数量显著减少,且‘KWS0143’的根际微生物数量高于‘Beta464’.两品种植株干质量、土壤酶和土壤微生物之间呈显著正相关;通径分析表明,‘KWS0143’植株干质量决定系数表现为:放线菌>细菌>过氧化氢酶>脲酶>真菌>碱性磷酸酶,‘Beta464’表现为:放线菌>过氧化氢酶>脲酶>真菌>碱性磷酸酶>细菌.     

三种荒漠灌木根际可培养固氮细菌类群及其固氮和产铁载体能力

【目的】揭示西鄂尔多斯荒漠孑遗灌木四合木(Tetraena mongolica)、沙冬青(Ammopiptanthus mongolicus)、白刺(Nitraria tangutorum)根际可培养固氮细菌类群,分析固氮酶活性和产铁载体能力,以期为认识和利用荒漠植物根际促生细菌提供依据。【方法】以Ashby无氮培养基、采用涂布划线法分离纯化根际固氮细菌;基于16S r RNA基因分析类群组成;以乙炔还原方法测定固氮酶活性;以铬天青S蓝色平板定性筛选产铁载体菌株,以分光光度计法定量产铁载体能力。【结果】共分离出固氮细菌22株,分别属于3个门与9个属,其中变形菌门(Proteobacteria,82%)为绝对优势门,假单胞菌属(Pseudomonas,27.27%)为优势属;Rhizobium和Bacillus分别是沙冬青和四合木的独有属,而白刺独有属有Enterobacter、Stenotrophomonas和Paenibacillus;10株在无氮培养基上生长迅速,它们的固氮酶活性在871.71-3 383.09 nmol C2H4/(H·Culture)之间,并且其中有7株具有产铁载体能力,其产铁载体的As/Ar值范围为0.35-0.79。【结论】鄂尔多斯荒漠珍稀孑遗灌木植物根际固氮细菌类群多样,植物间差异明显,包含多种高固氮酶活性和产铁载体能力的固氮细菌,可作为植物生长促进根际细菌的重要来源。     

嫁接辣椒根系特征及根际土壤酶活性与青枯病抗性的关系

以‘卫士’辣椒为砧木,‘新丰2号’为接穂嫁接,通过人工接种青枯病菌研究嫁接和自根辣椒根系特征、根际土壤微生物及酶活性的变化,探讨嫁接辣椒的抗病机理.结果显示:接种青枯病菌前,嫁接辣椒的根系重量、总长度、总体积、表面积、根尖数和分叉数均显著高于自根苗,根系活力、根际土壤放线菌数量和比例,以及根际土壤酶(多酚氧化酶、过氧化物酶和脱氢酶)活性也明显高于自根苗.接种青枯病菌后,嫁接辣椒的根系受伤程度较自根苗轻,根系重量、总长度、总体积、表面积、根尖数和分叉数的降低幅度均显著小于自根苗,根系活力、根际土壤微生物数量、放线菌比例及土壤酶活性明显大于自根苗.研究表明,嫁接辣椒根系发达,根系活力增强,根际土壤放线菌比例增加及酶活性提高是其青枯病抗性增强的重要原因.     

固氮细菌导入水稻原生质体并再生植株

本工作利用广亲和水稻品种02428细胞悬浮系为材料、分离出原生质体,将固氮细菌Alcaligenes faecalis A-1501导入水稻原生质体并分化培养成株。A.faecalis A-1501是我国南方分离出的一种水稻根际固氮细菌,具有较高的固氮酶活性和吸氢酶活性,并可利用同化 CO_2作为碳源生长及进行固氮作用。该菌不仅可附着和积聚在水稻根表,并可进入水稻根细胞以至原生质体内,并具有固氮活性。     

不同植物根际土壤碳氮水解酶活性热点区的空间分布特征

为研究喀斯特退耕地不同植物根际土壤碳氮水解酶活性的空间分布特征,采用喀斯特区域农田表层土壤,选择当地粮食作物玉米、牧草苜蓿及弃耕后常见草本植物莎草,进行室内根盒培养试验。利用根际土壤原位酶谱分析技术,研究不同植物根际与非根际土壤β-葡萄糖苷酶(βG)和N-乙酰氨基葡萄糖苷酶(NAG)活性的分布模式。结果发现:1)3种植物在根尖和根伸长区都存在酶活性热点区,最大根际酶活性热点区范围为苜蓿莎草玉米;2)玉米βG和NAG根际酶活性热点范围在根尖与根伸长区范围相近约为1.13 mm,苜蓿根际βG热点区范围是根伸长区(1.98 mm)根尖(1.19 mm),而NAG热点区范围是根尖(0.91 mm)根伸长区(0.59 mm),莎草根际βG和NAG活性热点区范围均是根尖(1.38—1.86 mm)根伸长区(0.93—1.16 mm);3)豆科植物苜蓿的根系和根际微生物偏好碳需求,这可能与豆科植物的固氮功能有关,缓解氮养分需求;而莎草根系和根际微生物偏好氮养分,这与喀斯特土壤氮养分限制有关。总体上,苜蓿根际酶活性热点范围最广,根系和根际微生物偏好碳需求,而且其特有的固氮功能可缓解氮养分需求,对于喀斯特生态恢复效果更好。本研究的土壤原位酶谱法可为在根际酶活性热点区范围进行微生物养分获取机制提供定量依据。     

Influence of some environmental factors on nitrogen fixation in the rhizosphere of rice

Summary Nitrogen fixers make up a large percentage of the total microflora in the rhizosphere of lowland rice. There are more aerobic nitrogen fixers than there are anaerobic ones. When soil crumbs from the root zone were placed on a nitrogen free agar medium and inoculated at 0, 5, 10, and 21 percent oxygen concentration, colonies of aerobic nitrogen fixers reached their greatest diameter at 5 and 10 percent oxygen. In acetylene reduction assays rice plants grown in paddy fields and in solution culture were tested for the nitrogenase activities of their roots at different oxygen tensions. Nitrogenase activity was highest at 3 percent oxygen, lower at 0 percent, and far lower at 21 percent. When rice was grown in solution culture the redox potential of the nutrient solution strongly influenced nitrogenase activity. With declining redox potential, nitrogenase activity increased to a maximum value but dropped sharply as redox potential further decreased. Ten ppm of combined nitrogen as urea depressed nitrogenase activity on excised roots. Combined nitrogen applied to one part of the root system affected, to some extent, nitrogen fixation on other roots kept in a solution without nitrogen. Nitrogenase activity in a fertility trial with lowland rice, examined at several dates, showed no inhibitory effect of fertilizer nitrogen, however, presumably because the nitrogen concentration in the soil solution rapidly decreased. Instead, an overall stimulating effect of nitrogen dressing was noticeable. Diurnal fluctuations of nitrogenase activity in the rhizosphere, with a peak in the afternoon and low fixation rates after low solar radiation, suggest a photosynthetic effect on nitrogen fixation. re]19751208     

Effects of intercropping sugarcane and soybean on growth, rhizosphere soil microbes, nitrogen and phosphorus availability

The effects of sugarcane plantation intercropped with soybean on plant growth, yield, enzyme activity, nitrogen and phosphorus contents, the microbe quantity of rhizosphere soil were investigated. Results showed that dry weight of biomass and yield under sugarcane/soybean intercropping were increased by 35.44 and 30.57 % for sugarcane, and decreased by 16.12 and 9.53 % (100-grain weight) for soybean, respectively. The nitrogenase activity of intercropping soybean nodule was significantly increased by 57.4 % as compared with that in monoculture models. The urease activities of intercrops sugarcane and soybean were promoted by 89 and 81 % as compared to that of the monoculture models, respectively. The effective nitrogen and phosphorus contents of rhizospheric soil of intercrops sugarcane and soybean were increased by 66 and 311.7 %, respectively, as compared to those in the monoculture system. Microbe number of rhizosphere soil in the intercropping pattern increased significantly as compared to those in the monoculture models. The quantities of bacteria, fungi, and actinomyces increased by 42.62, 14.5 and 78.5 % in the intercropping sugarcane, while the intercropping soybean increased by 188, 183 and 73 %, respectively. Therefore, growing sugarcanes in combination with soybean can be considered a good agriculture management practice, helping to promote plant growth, yield and increase soil nutrients.     

Wheat root colonization and nitrogenase activity by Azospirillum isolates from crop plants in Korea

Nitrogen-fixing bacteria were isolated from the rhizosphere of different crops of Korea. A total of 16 isolates were selected and characterized. Thirteen of the isolates produced characteristics similar to those of the reference strains of Azospirillum, and the remaining 3 isolates were found to be Enterobacter spp. The isolates could be categorized into 3 groups based on their ARDRA patterns, and the first 2 groups comprised Azospirillum brasilense and Azospirillum lipoferum. The acetylene reduction activity (ARA) of these isolates was determined for free cultures and in association with wheat roots. There was no correlation between pure culture and plant-associated nitrogenase activity of the different strains. The isolates that showed higher nitrogenase activities in association with wheat roots in each group were selected and sequenced. Isolates of Azospirillum brasilense CW301, Azospirillum brasilense CW903, and Azospirillum lipoferum CW1503 were selected to study colonization in association with wheat roots. We observed higher expression of beta-galactosidase activity in A. brasilense strains than in A. lipoferum strains, which could be attributed to their higher population in association with wheat roots. All strains tested colonized and exhibited the strongest beta-galactosidase activity at the sites of lateral roots emergence.     

甘蔗幼苗对难溶性磷的吸收及其根系对低磷胁迫的响应

为明确甘蔗适应低磷胁迫的生理生化机制,挖掘甘蔗对磷素的利用潜力,揭示甘蔗对低磷胁迫适应的可能机制,该研究以ROC22和ROC10两个甘蔗品种为材料,采用水培和土培的方法研究了甘蔗幼苗对难溶性磷的吸收及其在低磷胁迫下根构型和根系的生理反应。结果表明:(1)培养在以难溶性磷(Ca-P和Al-P)为磷源的培养液中的甘蔗的叶片数、地上部干重、生物量较缺磷(-P)处理显著增加,与对照(+P)的相当,甘蔗总磷积累量也显著提高,达到对照(+P)处理磷积累量的30%～77%。(2)在低磷条件下,甘蔗幼苗的根系有向土壤深层分布的趋势,根的总体积增大、最长根长变长、浅根系分布增多。(3)甘蔗幼苗在低磷环境下,根际环境明显酸化,且根系分泌物能溶解难溶性的铝磷,植株体内酸性磷酸酶的活性也明显增强。以上表明甘蔗幼苗有较强的吸收利用难溶性磷的能力,而低磷条件下根系数量增加、主根的向地性、浅根系分布增多、根际酸化以及植株体内酸性磷酸酶活性的增强可能是甘蔗幼苗适应缺磷环境的重要机制。     

不同土壤类型下甘蔗根系AM真菌多样性及与土壤因子关系

甘蔗是广西重要的糖料作物,本研究通过建立克隆文库、土壤养分分析和根样染色等方法测定了33个采样点3种土壤类型(赤红壤,红壤,砖红壤)下甘蔗根系AM真菌多样性及其与土壤因子的关系。结果表明,3种土壤类型的甘蔗根系共鉴定出6科6属11种AM真菌,AM真菌各属频度存在明显差异,其中球囊霉属的频度值最高,在33个根系样品中有32个存在该属,为广西甘蔗根系AM真菌的优势属,而类球囊霉属、无梗囊霉属、近明球囊霉属、多样孢囊霉属和盾巨孢囊霉属5个属为稀有属。3种土壤类型的甘蔗根系均发现有球囊霉属和盾巨孢囊霉属;近明球囊霉属、无梗囊霉属和类球囊霉属仅在赤红壤的甘蔗根系中出现;而多样孢囊霉属仅在在赤红壤和砖红壤的甘蔗根系中出现。土壤的pH与AM菌根侵染率呈显著正相关,而有机质、总N、有效P、交换性Mg2+与AM菌根侵染率均呈负相关。本研究表明,自然条件下甘蔗根系具有相对丰富的AM真菌类群,这些AM真菌可能在甘蔗生长过程中发挥着重要的生态功能。     

接种变栖克雷伯氏菌DX120E对不同甘蔗品种的促生效应

为探究具有高固氮酶活性的变栖克雷伯氏菌DX120E回接甘蔗后的固氮能力和促生效应,以甘蔗品种B8和GT21的无菌组培苗为材料,采用根部接种的方法,研究固氮菌DX120E在甘蔗体内的定殖数量及其对甘蔗组培苗植株生长、氮代谢关键酶活性和硝态氮含量及矿质元素吸收的影响.结果表明： 固氮菌DX120E能在甘蔗根和地上部分组织内生存和定殖;接种固氮菌DX120E可以有效促进甘蔗植株生长和对矿质营养的吸收;显著提高甘蔗植株体内的硝酸还原酶(NR)活性,同时也能在一定程度上提高植株体内谷氨酰胺合成酶(GS)活性,增加硝态氮含量.表明变栖克雷伯氏菌DX120E对甘蔗具有明显的促生效应,在生物固氮肥开发方面具有较大的应用前景.     

乙烯利对甘蔗分蘖期茎三种酶活性的影响及其与分蘖的关系

在分蘖前期喷施适宜浓度(100mg/L)乙烯利提高了蔗茎的过氧化物酶活性和IAA氧化酶的活性。用100mg/L乙烯利处理后,两个品种根部的过氧化物酶和IAA氧化酶活性明显高于上部的活性,并且比对照和400mg/L乙烯利处理的效果明显。乙烯利处理后新台糖16号上部节间的酸性转化酶活性始终高于下部节间的酶活性,其中100mg/L乙烯利处理下部节间的明显低于对照的;乙烯利处理后新台糖22号茎内的酸性转化酶活性也低于对照的,但与对照的差异相对比新台糖16号的小。     

固氮菌接种对棉苗氮磷钾吸收、某些酶活性及产量的影响(英文)

Spermospheremodels和盆栽试验结果表明 ,海岛棉 (GossypiumbarbadenseL .)苗接种自生固氮菌(Azotobactersp .)、巴西固氮螺菌NO40 (AzospirillumbrasilenseNO40 )、多粘芽孢杆菌 (BacilluspolymyxaCF)和根瘤菌 (Rhizobium) ,和以自生固氮菌分别与其它 3种供试菌种两者的混合菌 ,能增强棉花根际固氮酶活性和棉苗对氮的吸收 ,提高功能叶中氮、磷和叶绿素含量 ,从而有利于提高生物学产量 ,尤以自生固氮菌的促进效应最为显著。另一方面 ,混合菌处理较单一菌株处理 ,可以显著提高棉苗对氮的吸收 ,增加干物质积累提高皮棉产量 ,其中尤以固氮菌分别与根瘤菌或巴西固氮螺菌NO40的协同效应最显著     

Isolation and characterization of <Emphasis Type="Italic">Azotobacter</Emphasis> and <Emphasis Type="Italic">Azospirillum</Emphasis> strains from the sugarcane rhizosphere

Bacteria with the ability to grow on nitrogen-free media and with nitrogenase activity under aerobic or microaerobic conditions were isolated from sugarcane roots collected from four different agricultural locations in Granada (Spain). Isolates were Gram negative rods and were identified as Azotobacter chroococcum and Azospirillum brasilense. Our results suggest that Azotobacter isolates do not have a particular affinity for sugarcane rhizospheres and that, on the contrary, Azospirillum isolates show specific association and perhaps endophytic colonization of sugarcane. However, obligate endophytes (Gluconacetobacter diazotrophicus) were not found in the apoplastic fluid of the stems and macerates extracts of sugarcane tissues with the procedure applied. Population of this microorganism might be in low number in the Spanish sugarcane varieties studied which is also discussed.