硒的价态与浓度水平对6种植物种子发芽和根际生长的影响

本文研究了硒的价态(Se6+和Se4+)和浓度水平(0～100mgSe·L-1)对6种植物(大麦、小麦、花椰菜、萝卜、苜蓿和欧芹)种子萌发和根际生长特性的影响。结果表明,低浓度硒(<1mgSe·L-1)对种子发芽促进作用不明显,而高浓度硒(>4mgSe·L-1)则有显著抑制作用,不同种子对硒的抗性表现不同。根长和芽长的测定结果表明,低浓度对花椰菜和小麦种子生长具有显著促进作用,对欧芹种子表现出抑制作用。较高浓度(1～4mg·L-1)即对花椰菜、苜蓿和欧芹的根生长表现出抑制作用,高浓度对小麦、大麦和萝卜根生长有抑制作用,且使芽生长受到抑制的硒浓度高于根生长。比较价态,低硒时六价对花椰菜生长的促进作用显著高于四价,高硒时小麦和苜蓿对硒的抗性表现为六价硒强于四价硒,其余科属差异不显著。不同科属对硒的抗性为禾本科小麦和大麦最强,十字花科花椰菜和萝卜次之,豆科苜蓿较差,伞形科欧芹最差。

促植物生长根际细菌HG28-5对黄瓜苗期生长及根际土壤微生态的影响

为研究促植物生长根际细菌HG28-5对黄瓜生长发育和根际土壤微生态的影响,采用HG28-5菌悬液进行黄瓜浸种处理后播种到穴盘,调查出苗和苗期生育指标,确认其对黄瓜的促生作用;测定黄瓜苗期根际土壤酶活性、速效氮磷钾和微生物种群数量,了解HG28-5对黄瓜苗期根际土壤微生态的影响;并检测HG28-5在黄瓜苗期植株根部和根际土壤的定殖密度。结果表明,HG28-5浸种处理能显著提高黄瓜的出苗势、出苗指数,提高出苗整齐度;显著增加苗期黄瓜株高、叶片数、根长、地上部和根鲜质量,显著提高根系活力;显著提高黄瓜苗期根际土壤脲酶、磷酸酶和蔗糖酶的活性,显著增加根际土壤速效磷的含量;显著增加黄瓜苗期根际土壤细菌和放线菌的数量,显著减少根际土壤真菌数量;另外,HG28-5在黄瓜根际具有良好的定殖能力,播种后第30天时,在黄瓜根系和根际土壤中的定殖密度分别为9.20×10~5cfu·g^(-1)和5.90×10~5cfu·g^(-1)。

促植物生长根际细菌A21-4对田间辣椒生长及根际土壤微生态环境的影响

为研究促植物生长根际细菌A21-4对辣椒生长发育和根际土壤微生态的影响,细菌A21-4灌根处理辣椒进行田间试验,测定了辣椒生长指标、土壤酶活性、速效氮磷钾及微生物种群数量。结果表明,细菌A21-4处理显著提高了辣椒成株期的茎粗、叶绿素含量和根系活力,辣椒移栽30 d后分别比对照提高了23.66%、56.26%和42.24%;移栽60 d后对辣椒果实的蛋白质、维生素C和硝态氮的含量分别提高了29.32%、53.97%和129.84%;移栽30-70 d,辣椒根际土壤过氧化氢酶、脲酶和磷酸酶活性分别显著提高22.95%-32.31%、24.32%-94.11%和49.41%-271.74%;土壤速效氮、磷、钾含量分别显著增加7.60%-49.25%、7.24%-17.93%和12.70%-25.61%;显著增加根际土壤细菌和放线菌数量,而降低真菌数量。

两株促植物生长根际细菌对辣椒的促生效果及其在辣椒根际定殖能力

以2株促植物生长根际细菌A21-4和HG28-5菌株为试材,在穴盘栽培条件下,探究了2种菌株浸种处理对辣椒出苗、生长发育和根际土壤生态的影响,以及其在辣椒根际的定殖能力。结果表明:A21-4和HG28-5浸种处理能显著提高辣椒出苗势,比对照分别提高40.54%和37.85%;同时,A21-4和HG28-5均显著促进辣椒苗期生长、叶绿素含量和根系活力,叶绿素含量各比对照增加65.49%和43.66%,根系活力各比对照提高77.91%和55.81%;此外,A21-4和HG28-5均显著提高辣椒根际土壤酶活性、有机质和速效磷的含量,尤其是A21-4的脲酶活性比对照提高66.01%,有机质含量比对照增加66.62%,HG28-5的磷酸酶活性比对照提高88.16%,速效磷含量比对照增加67.53%。另外,A21-4和HG28-5均具有良好的根际定殖能力,在皿内采用双层滤纸法测定其定殖密度,分别为2.15×105 cfu/cm和4.75×105 cfu/cm,在穴盘育苗期间,A21-4和HG28-5在辣椒根部定殖密度各能维持105 cfu/cm和106 cfu/cm左右,在根际土壤能保持104 cfu/cm和105 cfu/cm以上的定殖密度。

生物菌肥对玉米生长及产量影响的研究进展

生物菌肥通过改善土壤环境,与促进植物生长的根际细菌(PGPR)相互作用,直接或间接地促进植物生长发育。大量研究表明,施用生物菌肥能有效促进玉米及其他作物的生长,提高作物产量和品质。生物菌肥的大量施用可减少氮肥过剩对环境的污染,对农业可持续发展极其重要。

利用PCR技术快速检测根际产ACC脱氨酶细菌

通过产生ACC脱氨酶降低胁迫乙烯水平并缓解盐胁迫危害,是植物根际促生菌(PGPR)促进宿主生长和抗逆的重要机制。本研究提出了利用PCR技术快速检测产ACC脱氨酶细菌的快捷方法。以编码ACC脱氨酶的acd S基因为标记,分别使用acd Sf3/acd Sr4、Deg ACCf/Deg ACCr和F1936f/F1938r三对引物,对多种盐生植物和美洲黑杨(Populus deltoids)的根部及根际土中分离得到的细菌菌株进行检测。结果表明,结合acd Sf3/acd Sr4引物和递减PCR(touchdown-PCR)方法时,能获得单一的特异性扩增条带且扩增成功率高;但Deg ACCf/Deg ACCr和F1936f/F1938r两对引物特异性较差。从247个菌株中检测到25株含有acd S基因,旨为今后研究植物根际细菌acd S基因遗传性及储备丰富的功能性菌株奠定基础。

Dynamics of Microbial Activity Related to N Cycling in Cd-Contaminated Soil During Growth of Soybean

The potential influences of cadmium (Cd) on the biochemical processes of the soil nitrogen (N) cycle, along with the dynamics of ammonification, nitrification, and denitrification processes in the rhizosphere and non-rhizosphere (bulk soil), respectively, were investigated in a Cd-stressed system during an entire soybean growing season. In terms of Cd pollution at the seedling stage, the ammonifying bacteria proved to be the most sensitive microorganisms, whereas the effects of Cd on denitrification were not obvious. Following the growth of soybeans, the influences of Cd on ammonification in the bulk soil were: toxic impacts at the seedling stage, stimulatory effects during the early flowering stage, and adaptation to the pollutant during the podding and ripening stages. Although nitrification and denitrification in the bulk soil decreased throughout the entire growth cycle, positive adaptation to Cd stress was observed during the ripening stage. Moreover, during the ripening stage, denitrification in the bulk soil under high Cd treatment (20 mg kg-1) was even higher than that in the control, indicating a probable change in the ecology of the denitrifying microbes in the Cd-stressed system. Changes in the activity of microbes in the rhizosphere following plant growth were similar to those in the non-rhizosphere in Cd treatments; however, the tendency of change in the rhizosphere seemed to be more moderate. This suggested that there was some mitigation of Cd stress in the rhizosphere.

Characterization of Microbial Community Structure in Rhizosphere Soils of Cowskin Azalea(Rhododendron aureum Georgi)on Northern Slope of Changbai Mountains,China

The vegetation and soil are mutual environmental factors, soil characteristics, such as chemical properties and microorganism that affect the vegetation occurrence, development and succession speed. In this study, we evaluated the structure of microbial communities of rhizosphere of Cowskin Azalea(Rhododendron aureum Georgi) populations and compared with non-rhizosphere soils at four sample sites of the Changbai Mountains, China, and analyzed the correlation between chemical properties of soil and microbial communities. The results showed that microbial structure and soil chemical properties are significant superior to non-rhizosphere at all four sample sites. The rhizosphere microorganisms are mainly composed of bacteria, actinomycetes, followed by fungi least. The principal component analysis(PCA) biplot displayed that there are differences between rhizosphere and non-rhizosphere soils for microflora; Through correlation analysis, we found that the bacteria is clearly influenced by p H on the Changbai Mountains, besides p H, other soil features such as NO3–-N. These data highlight that R. aureum as the dominant vegetation living in the alpine tundra is a key factor in the formation of soil microorganism and improving soil fertility, and is of great significance for the maintenance of alpine tundra ecosystem.

The Ability of Phosphate Solubilizing Bacteria Isolated from Coffee Plant Rhizosphere and Their Effects on Robusta Coffee Seedlings

Phosphate solubilizing bacteria isolated from rhizosphere of coffee plants may play an important role in improving phosphate availability for the plants. However, one of the factors influencing the degree of phosphate solubilization by these bacteria is the ability of the microorganisms to utilize phosphate. The objective of this study was to determine the ability of phosphate solubilizing bacteria isolated from coffee plant rhizosphere and their effects on robusta coffee seedling growth. This research was carried out by taking soil samples from Andungsari （Bondowoso District） and Kaliwining （Jember District） coffee plantations, both located in East Java. Liquid medium of Pikovskaya was used for isolation of phosphate solubilizing bacteria from the soil samples. Results of this study showed that 12 phosphate solubilizing bacteria were obtained from this isolation, eight isolates from Andungsari and four isolates from Kaliwining. Selection of those bacteria isolates was based on the qualitative ability in phosphate solubilizing by measuring the clear zone surrounding the colonies and quantitatively by measuring the solubilized phosphate using spectrophotometer. The results showed that four isolates, in the order of PFpKW1, PFpC61, PFsC62a, and PFsB 11, had the highest qualitative ability in solubilizing phosphate, while for the highest quantitative ability the order was PFpKW 1, PFpC61, PFsC62a, and PFsB 11. In a green house study, inoculation of these selected isolates onto Robusta coffee seedlings positively enhanced the coffee seedling growth. Phenotypic test indicated that the four isolates are similar to the genus of Pseudomonas.

Isolation of Six Phosphate Dissolving Rhizosphere Bacteria （Bacillus subtilis） and Their Effects on the Growth, Phosphorus Nutrition and Yield of Maize （Zea mays L.） in Mali

The disadvantages of the long term application of Tilemsi natural phosphate （TNP） on maize （Zea mays L.） production has come out because of its low P availability. Some functional soil microbes, such as phosphate dissolving bacteria, have great potential in improvement of P solubility from TNP and P uptake by plants. The present study aimed to isolate and characterize typical phosphate dissolving bacterial strains （Bacillus subtilis） from Malian soils, and investigate their role in P uptake by maize grown in soils amended with TNP. The experimental design was a split plot with three main plots of fertilizers sources, i.e., natural phosphate, commercial fertilizer and without fertilizer, and with seven sub-plots of six microorganisms plus the control. The field experiment results have shown that the maize inoculated with the phosphate dissolving bacteria was improved in seed germination, plant growth, plant production （increase yield by 42%）, grain and aerial dry biomass （P） content of 34% and 64%, respectively. They have also shown that the locally available TNP can be used by the Malians farmers in maize culture and have comparable production to the one obtained with the costly imported commercial phosphate fertilizer, like the complex cereal. The project has provided information for the combined use of the Mali TNP and phosphate dissolving bacteria Bacillus subtilis subsp, subtilis （T）： DSM 10 in improvement of maize production in the country.

微生物帮助烟草抗旱的机理及其应用

干旱是中国烟草种植业面临的较为严重的非生物胁迫.很多与植物共生或联合的根际微生物能帮助植物避旱和耐旱.微生物能通过菌丝吸水并转运到植物,通过产生植物激素或改变植物内源激素的平衡来促进根发育和伸长,或诱导叶片关闭气孔,促进根吸水和减少叶片散失水分来避旱.微生物能通过调整不同激素介导的信号通路,诱导植物产生系统抗逆性,促进植物细胞产生渗透保护剂、抗氧化物和活性氧清除剂而耐旱.微生物还能帮助植物吸收营养,以支持植物在干旱胁迫下的代谢和生长.本文关注丛枝菌根真菌、模式内生真菌印度梨形孢和根际促植物生长细菌帮助烟草和番茄等植物抗旱的机理,探讨如何在烟草育苗和栽培中应用有益微生物来帮助烟草抗旱.

Arbuscular Mycorrhiza Prevents Suppression of Actual Nitrification Rates in the (Myco-)Rhizosphere of Plantago lanceolata

The vast majority of herbaceous plants engage into arbuscular mycorrhizal (AM) symbioses and consideration of their mycorrhizal status should be embodied in studies of plant-microbe interactions. To establish reliable AM contrasts, however, a sterilized re-inoculation procedure is commonly adopted. It was questioned whether the specific approach is sufficient for the studies targeting the bacterial domain, specifically nitrifiers, a group of autotrophic, slow growing microbes. In a controlled experiment mycorrhizal and non-mycorrhizal Plantago lanceolata were grown up in compartmentalized pots to study the AM effect on nitrification rates in the plant rhizosphere. Nitrification rates were assayed following an extensive 3-week bacterial equilibration step of the re-inoculated soil and a 13-week plant growth period in a controlled environment. Under these specific conditions, the nitrification potential levels at harvest were exceptionally low, and actual nitrification rates of the root compartment of non-mycorrhizal P. lanceolata were significantly lower than those of any other compartment. It is then argued that the specific effects should be attributed to the alleged higher growth rates of non-mycorrhizal plants that are known to occur early in the AM experiment. It is concluded that the specific experimental approach is not suitable for the study of microbes with slow growth rates.

Indigenous Microbial Community Structure in Rhizosphere of Chinese Kale as Afected by Plant Growth-Promoting Rhizobacteria Inoculation

Plant growth-promoting rhizobacteria （PGPR） have been widely recognized as an important agent, especially as a biofertilizer, in agricultural systems. The objectives of this study were to select effective PGPR for Chinese kale （Brassica oleracea var. alboglabra） cultivation and to investigate the effect of their inoculation on indigenous microbial community structure. The Bacillus sp. SUT1 and Pseudomonas sp. SUT19 were selected for determining the efficiency in promoting Chinese kale growth in both pot and field experiments. In the field experiment, PGPR amended with compost gave the highest yields among all treatments. The Chinese kale growth promotion may be directly affected by PGPR inoculation. The changes of microbial community structure in the rhizosphere of Chinese kale following PGPR inoculation were examined by denaturing gradient gel electrophoresis （DGGE） and principal coordinate analysis. The DGGE fingerprints of 16S rDNA amplified from total community DNA in the rhizosphere confirmed that our isolates were established in the rhizosphere throughout this study. The microbial community structures were slightly different among all the treatments, and the major changes depended on stages of plant growth. DNA sequencing of excised DGGE bands showed that the dominant species in microbial community structure in the rhizosphere were not mainly interfered by PGPR, but strongly influenced by plant development. The microbial diversity as revealed by diversity indices was not different between the PGPR-inoculated and uninoculated treatments. In addition, the rhizosphere soil had more influence on eubacterial diversity, whereas it did not affect archaebacterial and fungal diversities.

Plant Growth-Promoting Traits in Rhizobacteria of Heavy Metal-Resistant Plants and Their Effects on Brassica nigra Seed Germination

Phytoremediation is an emerging technology that uses plants and their associated microbes to clean up pollutants from the soil, water, and air. In order to select the plant growth-promoting rhizobacteria （PGPR） for phytoremediation of heavy metal contamination, 60 bacterial strains were isolated from the rhizosphere of two endemic plants, Prosopis laevigata and Spharealcea angustifolia, in a heavy metal-contaminated zone in Mexico. These rhizobacterial strains were characterized for the growth at different pH and salinity, extracellular enzyme production, solubilization of phosphate, heavy metal resistance, and plant growth-promoting （PGP） traits, including production of siderophores and indol-3-acetic acid （IAA）. Overall, the obtained rhizobacteria presented multiple PGP traits. These rhizoba^teria were also resistant to high levels of heavy metals （including As as a metalloid） （up to 480 mmol L-1 As（V）, 24 mmol L-1 Pb（II）, 21 mmol L-1 Cu（II）, and 4.5 mmol L-1 Zn（II））. Seven rhizobacterial strains with the best PGP traits were identified as members of Alcaligenes, Bacillus, Curtobacterium, and Microbacterium, and were selected for further bioassay. The inoculation of Brassica nigra seeds with Microbacteriurn sp. CE3R2, Microbacterium sp. NE1R5, Curtobacterium sp. NM1R1, and Microbacterium sp. NM3E9 facilitated the root development; they significantly improved the B. nigra seed germination and root growth in the presence of heavy metals such as 2.2 mmol L-1 Zn（II）. The rhizobacterial strains isolated in the present study had the potential to be used as efficient bioinoculants in phytorremediation of soils contaminated with multiple heavy metals.

Effect of Plant Growth-Promoting Rhizobacteria on Growth,Nodulation and Nutrient Accumulation of Lentil Under Controlled Conditions

Application of plant growth-promoting rhizobacteria （PGPR） has been shown to increase legume growth and development under field and controlled environmental conditions. The present study was conducted to isolate plant growth-promoting rhizobacteria （PGPR） from the root nodules of lentil （Lens culinaris Medik.） grown in arid/semi-arid region of Punjab, Pakistan and examined their plant growth-promoting abilities. Five bacterial isolates were isolated, screened in vitro for plant growth-promoting （PGP） characteristics and their effects on the growth of lentil were assessed under in vitro, hydroponic and greenhouse （pot experiment） conditions. All the isolates were Gram negative, rod-shaped and circular in form and exhibited the plant growth-promoting attributes of phosphate solubilization and auxin （indole acetic acid, IAA） production. The IAA production capacity ranged in 0.5-11.0μg mL-1 and P solubilization ranged in 3-16 mg L-1. When tested for their effects on plant growth, the isolated strains had a stimulatory effect on growth, nodulation and nitrogen （N） and phosphorus （P） uptake in plants on nutrient-deficient soil. In the greenhouse pot experiment, application of PGPR significantly increased shoot length, fresh weight and dry weight by 65%, 43% and 63% and the increases in root length, fresh weight and dry weight were 74%, 54% and 92%, respectively, as compared with the uninoculated control. The relative increases in growth characteristics under in vitro and hydroponic conditions were even higher. PGPR also increased the number of pods per plant, 1 000-grain weight, dry matter yield and grain yield by 50%, 13%, 2870 and 29%, respectively, over the control. The number of nodules and nodule dry mass increased by 170% and 136%, respectively. After inoculation with effective bacterial strains, the shoot, root and seed N and P contents increased, thereby increasing both N and P uptake in plants. The root elongation showed a positive correlation （R2 = 0.67） with the IAA production and seed yield exhibited a positive correlation （R2 = 0.82） with root nodulation. These indicated that the isolated PGPR rhizobial strains can be best utilized as potential agents or biofertilizers for stimulating the growth and nutrient accumulation of lentil.

Bacillus promotes invasiveness of exotic Flaveria bidentis by increasing its nitrogen and phosphorus uptake

The effect of exotic plants on Bacillus diversity in the rhizosphere and the role of Bacilli in exotic or native plant species remain poorly understood.Flaveria bidentis is an invasive grass in China.Setaria viridis is a native grass and occurs in areas invaded by F.bidentis.Our objectives were(i)to examine the differences in the Bacillus communities between F.bidentis and S.viridis rhizospheres soil,and(ii)to compare the effects of Bacilli from F.bidentis and S.viridis rhizospheres on the competitiveness of the invasive species.Flaveria bidentis monoculture,mixture of F.bidentis and S.viridis and S.viridis monoculture were designed in the field experiment.Bacillus diversity in their rhizosphere was analyzed using 16S rRNA.One of the dominant Bacilli in the rhizosphere soil of F.bidentis was selected to test its effect on the competitive growth of F.bidentis in a greenhouse experiment.Bacillus diversity differed in F.bidentis and S.viridis rhizosphere.Brevibacterium frigoritolerans was the dominant Bacilli in the rhizosphere of both F.bidentis and S.viridis;however,its relative abundance in the F.bidentis rhizosphere was much higher than that in the S.viridis rhizosphere.In addition,B.frigoritolerans in the F.bidentis rhizosphere enhanced the growth of the plant compared with that of S.viridis by improving the nitrogen and phosphorus levels.This study showed that F.bidentis invasion influenced Bacillus communities,especially B.frigoritolerans,which,in turn,facilitated F.bidentis growth by increasing the levels of available nitrogen and phosphorus.