Response of young hydroponically grown tomato plants to phenolic acids

Phenolic acids—excreted both as root exudates and by microorganisms—are of interest in cultivation systems of different horticultural crops since they have been claimed to accumulate in closed hydroponic growing systems. The aim of the present investigation was to assess the phytotoxic effects when hydroponically grown tomato plants are exposed to phenolic acids in the root environment. The tomato plants were grown in static aerated culture and exposed to benzoic, caffeic, chlorogenic, ferulic, p-hydroxybenzoic, salicylic and vanillic acid at concentrations of 50, 100, 150, 200 and 400 μM in the fresh nutrient solution. The highest concentration of all tested compounds significantly reduced fresh and dry weights. Salicylic and ferulic acid affected plants already at 150 and 200 μM while effects were less pronounced for p-hydroxybenzoic and chlorogenic acid. Chlorophyll fluorescence analysis did not result in any significant difference between any of the tested acids or concentrations. No clear dose-related pattern was obtained with respect to number of leaves and plant length. Visual assessment showed that the most deleterious effects appeared on the roots, which were discoloured and/or had slimy coatings when exposed to the phenolic acids. The uptake of several mineral nutrients was influenced at the highest concentration of all studied compounds. Significantly more bacteria were enumerated in the nutrient solution treated with phenolic acids compared to the controls. Most of the phenolic acids were degraded after 2 days during the start of the trial and within 1 day at the end of the trial. Concentrations phytotoxic to small tomato plants were 1000-fold higher than the natural concentrations measured before. Instead of potentially harmful, the relevance of certain phenolic acids as antimicrobial substances should be considered.     

黄绿木霉T1010对日光温室土壤微生物群落的影响

在土壤中施用黄绿木霉T1010,于樱桃番茄生长过程中定期取土样测定微生物数量。结果表明,黄绿木霉T1010能促进土壤中其它有益微生物的生长。在樱桃番茄盛果期,黄绿木霉T1010制剂处理组土壤细菌群落数量比初始值提高3．27倍,比常规肥料处理组提高76％;在盛果期,黄绿木霉T1010制剂处理组放线菌数量比常规肥料处理组提高1．32倍;黄绿木霉T1010制剂施人土壤后有些种类真菌数量有所下降;黄绿木霉T1010在土壤中生长,也促进了固氮菌的繁殖,与土壤处理前相比,在樱桃番茄苗期、盛花期、盛果期固氮菌数量分别提高0．91、4．19、6．98倍,盛果期比常规化肥处理组提高65％。应用黄绿木霉T1010制剂后,樱桃番茄花期、果期提前,果实整齐均匀,立枯病感病指数降低36．36％,侧根数比常规化肥处理组增加1．44倍,产量明显提高。     

低聚木糖对生长猪肠道菌群的影响

选用体重约20 kg的杜枫姜三元杂交猪180头,随机分成4组,每组45头。分别饲喂基础日粮(对照组)、基础日粮+100 mg/kg低聚木糖(第1组)、基础日粮+150 mg/kg低聚木糖(第2组)、基础日粮+200 mg/kg低聚木糖(第3组),研究不同处理对生长猪肠道菌群的影响。结果表明:与对照组相比,各试验组沙门氏菌数量均有所下降,且第2组显著低于对照组(P<0.05);第2、3组大肠杆菌数量与对照组相比分别下降了3.9%、0.7%;各试验组肠道乳酸杆菌数量均有增加趋势,比对照组分别增加了1.1%、1.4%、1.4%。     

短链脂肪酸组合对肉仔鸡消化道系统的影响

[目的]研究短链脂肪酸组合(SCFAs)对小肠肉仔鸡生产性能、小肠的食糜消化酶的活性及消化道菌群的影响。[方法]采用3×3+1试验安排,试验日粮在添加500 mg丁酸钠的基础上,进一步添加乙酸和丙酸,乙酸和丙酸的添加水平分别是500、1 0002、000 mg,另设不添加乙酸和丙酸的日粮作为对照。[结果]结果表明:日粮中添加500 mg/kg乙酸和丙酸能够增加小肠消化酶活性,抑制肠道中大肠杆菌生长,从而改善肉仔鸡生产性能。     

影响植物根际微生物区系之因素研究进展

根际是土壤、植物生态系统物质交换的活跃界面,植物作为第一生产者将部分光合产物转运至根部,通过分泌物供给根际微生物碳源和能源;根际微生物则将有机养分转化成无机养分利于植物吸收利用,植物、土壤、微生物的相互关系维持着土壤生态系统的生态功能。近年来,随着对根际土壤微环境研究的深入,根际微生物研究内容不断丰富和发展。笔者结合近年来国内外研究结果综述了不同因素对植物根际微生物生物多样性和生态功能产生的影响,并提出了今后这一领域的研究思路及方向     

铝胁迫对大豆根际土壤微生物区系的影响

通过盆栽试验研究了不同浓度外源铝对大豆根际土壤微生物区系的影响。结果表明:在低浓度下,铝对土壤细菌、放线菌具有刺激作用,在高浓度下,表现为抑制作用。铝对真菌的生长具有明显的刺激作用。在高浓度下,铝对土壤硝化细菌、反硝化细菌、自生固氮菌均产生强烈的抑制作用,最大抑制率分别为96%、98%和89%。土壤硝化细菌、反硝化细菌可以作为铝污染土壤生态环境的指示菌。铝对两个大豆品种根际土壤微生物区系组成的影响不一致,揭示铝胁迫的生物效应还与植物生长、植物根际效应有关。     

连作香蕉园生态熏蒸剂的筛选及其对土壤微生物群落结构的影响

通过对多年连作后发香蕉枯萎病土壤进行熏蒸处理,应用传统涂布计数法,结合变性凝胶电泳(Denaturing gradient gel electrophoresis,DGGE)技术,较为全面地研究了不同熏蒸剂对病原菌的杀灭效果以及对土壤微生物区系的影响,为连作蕉园的可持续栽培提供了理论依据。试验通过研究石灰、碳铵、石灰碳铵联用、二氧化氯、次氯酸钠、过氧化氢和氨水处理对水体病原菌孢子、土壤中尖孢镰刀菌的杀灭作用,逐步筛选出适合连作蕉园灌溉水和土壤的熏蒸剂种类。结果表明:上述熏蒸剂对水体或土壤中尖孢镰刀菌均具有杀灭作用,土壤中氨水、石灰碳铵联用处理效果更加显著,被选择为发病蕉园土壤熏蒸剂。不同用量氨水、石灰碳铵联用处理熏蒸土壤,随着熏蒸剂施用量的增加,土壤中尖孢镰刀菌数量下降幅度逐渐增大;两种熏蒸剂对土壤中可培养总细菌和总真菌均有杀灭效果,随着用量的增加,总真菌数量下降幅度显著高于总细菌。DGGE结果显示,氨水、石灰碳铵联用处理对土壤中总真菌种类的影响也显著高于总细菌,随着熏蒸剂用量的增加,总细菌有少许条带的增加或减少,总真菌条带丰富度急剧减少。与对照相比,各熏蒸剂处理后总细菌物种多样性指数均有所降低,随着用量的增加,总体呈下降趋势,在氨水、石灰碳铵联用用量分别为2.67 ml/kg和(3.33+1.67)g/kg时各项指数最高。综上,所有熏蒸剂均能作为水体病原菌杀灭剂,其中氨水、石灰碳铵联用是良好的连作蕉园土壤熏蒸剂,最适用量分别为2.67 ml/kg、(3.33+1.67)g/kg。     

不同剂量中链甘油三酯对川藏黑猪断奶仔猪生长性能和肠道微生物菌群比例的影响

本研究旨在探讨不同剂量中链甘油三酯(MCT)对川藏黑猪断奶仔猪生长性能和肠道微生物菌群比例的影响。试验选择体重为5.4 kg左右、25日龄断奶的川藏黑猪仔猪30头,按体重相近的原则随机分为5组,每组6个重复。对照组饲喂含1.5%豆油的基础日粮,抗生素组在对照组日粮基础上添加50 mg/kg金霉素,试验组分别以0.5%、1.0%和1.5%的MCT等量替代对照组日粮中的豆油,试验期21 d。结果表明:与对照组相比,1.0%MCT组和1.5%MCT组的仔猪末重和平均日增重显著提高(P0.05),耗料增重比和腹泻指数显著降低(P0.05);与抗生素组相比,1.5%MCT组显著提高平均日增重和平均日采食量(P0.05);与对照组相比,随着日粮中MCT添加量的增加,各肠段乳酸杆菌、双歧杆菌占总细菌的比例提高,大肠杆菌比例降低(P0.05);日粮添加MCT显著降低回肠链球菌比例(P0.05),1.0%MCT组显著降低结肠的链球菌比例(P0.05),1.0%MCT组和1.5%MCT组显著降低空肠的链球菌比例(P0.05);与抗生素组相比,日粮添加MCT显著提高各肠段双歧杆菌比例(P0.05),1.5%MCT组显著提高空肠、回肠和盲肠乳酸杆菌比例(P0.05),1.0%MCT组显著降低结肠链球菌比例(P0.05),1.5%MCT组显著降低盲肠和结肠链球菌比例(P0.05)。结果提示,日粮中添加1.5%MCT可提高川藏黑猪断奶仔猪肠道中有益菌的比例并降低有害菌的比例,改善肠道菌群结构,进而降低腹泻指数,提高生长性能。     

Gram-positive bacterial flora on the root surface of wheat (Triticum aestivum L.) grown under different soil conditions

We identified 108 Gram-positive bacterial strains isolated from the root surface of wheat grown under different soil conditions. The strains were divided into four groups based on morphological and physiological characteristics, but most appeared to be coryneform. The taxonomic position of the various groups was verified by the guanine+cytosine DNA contents of the strains. In general, the ranges of these values agreed with those described for the respective taxonomic positions in the literature, with a few exceptions. With soil improvement the distribution of the various groups on the root surface changed, with the coryneform group becoming dominant. This group was further divided into five subgroups, according to cell wall components, cellulose-decomposition, and morphological characteristics, and were identified to genus level. The distribution of these subgroups on the root surface of wheat did not alter with soil improvement. The genus Arthrobacter, the dominant subgroup, predominated in every plot.     

低聚木糖对仔猪生产性能和肠道微生物影响的研究

(目的)本试验旨在研究添加不同梯度低聚木糖对仔猪生产性能和肠道微生物的影响。(方法)试验选取35±2日龄体型基本一致的断奶仔猪300头,随机分为5个处理,每个处理6个重复。处理1为对照组(饲喂基础日粮),处理2、3、4、5分别在基础日粮的基础上添加50 mg/kg、100 mg/kg、150 mg/kg、200 mg/kg低聚木糖。(结果)结果表明,日粮中添加不同水平的低聚木糖,可降低仔猪的腹泻率(p<0.05),同时对仔猪的平均日增重(ADG)、平均日采食量(ADFI)、料重比(F/G)也有所改善但差异不显著(p>0.05)。低聚木糖添加组明显增加了乳酸菌的含量(p<0.05),对乳酸菌/沙门氏菌,乳酸菌/大肠杆菌比值有明显的改善作用(p<0.05),乳酸菌/对芽胞杆菌没有显著差异(p>0.05)。(结论)试验结果证明,低聚木糖对仔猪的生产性能有提高的趋势,可以增加仔猪肠道有益菌的数目,维持肠道微生物平衡。