Effects of Arbuscular Mycorrhizal Fungi and Ammonium: Nitrate Ratios on Growth and Pungency of Onion Seedlings

ABSTRACT

A pot experiment was conducted to study the growth and pungency of Allium cepa L. grown in Perlite as affected by colonization by the arbuscular mycorrhizal (AM) fungi Glomus versiforme and Glomus intraradices BEG141 and by ammonium:nitrate (NH₄ ⁺:NO₃ ^?) ratios of 3:1, 1:1, and 1:3 in 4 mM solutions. Plants were harvested when bulb formation commenced. In general, mycorrhizal colonization resulted in increased shoot dry weight, shoot length, sheath diameter, root nitrogen (N) and phosphorus (P) content (except with G. intraradices and a NH₄ ⁺:NO₃ ^? ratio of 1:3), shoot N and P concentrations (except with G. versiforme and a NH₄ ⁺:NO₃= ratio of 3:1) and content. Plants inoculated with G. versiforme had higher growth parameters and N and P content than those with G. intraradices, whereas N and P concentrations showed the opposite trends. Growth parameters and N and P content of non-mycorrhizal plants were highest at a NH₄ ⁺:NO₃= ratio of 1:3, while those of plants inoculated with G. versiforme or G. intraradices were highest at a ratio of NH₄ ⁺:NO₃ ^? 3:1 or 1:1. Neither mycorrhizal colonization nor proportion of inorganic N species significantly affected bulb enzyme-produced pyruvate or total or organic sulfur (S) concentrations in plant shoots. Colonization by AM fungi made a substantial contribution to onion growth and may not have been directly related to bulb pungency at early stages of plant growth. However, the influence of AM fungi on plant N and P metabolism may have implications for onion flavor at later stages of plant growth.     

DOUGLAS-FIR SEEDLING RESPONSE TO A RANGE OF AMMONIUM: NITRATE RATIOS IN AEROPONIC CULTURE

The objective of the experiment was to identify the most favorable nitrogen (N) source ratio of ammonium (NH₄ ⁺) and nitrate (NO₃ ^?) for aeroponically-grown Douglas-fir when pH was maintained at pH 4.0. Seedlings were grown in controlled environments with solutions containing 0:100, 20:80, 40:60, 60:40, 80:20 or 100:0 NH₄ ⁺:NO₃ ^? ratios. Nutrient additions in the aeroponic culture units were controlled by solution conductivity set points. Seedling growth and nutrient allocation was observed for 45 days. Different NH₄ ⁺:NO₃ ^? ratios resulted in significant differences in the rate of N addition, growth, morphology, and nutrient allocation. Seedlings grown in solutions containing 60 or 80% NO₃ ^? were characterized by a combination of high growth and photosynthetic rates, high and stable internal plant N concentrations, and sufficient levels of other essential nutrients. High proportions of NH₄ ⁺ in solution resulted in low rates of N addition, stunted lateral root growth, and may have been toxic.     

INFLUENCE OF SALINITY AND AMMONIUM: NITRATE RATIO ON GROWTH,PHOTOSYNTHESIS, FATTY ACID AND THE ACTIVITY OF ANTIOXIDATIVE ENZYMES IN CANOLA

The effects of sodium chloride (NaCl) salinity (0 and 200 mM) and ammonium (NH₄):nitrate (NO₃) ratios (100:0, 25:75, 50:50, and 75:25) on growth, photosynthesis, fatty acids and the activity of antioxidative enzymes were investigated in canola plants. Leaf area and fresh and dry weights of leaves were significantly reduced by the salinity. The reduction in vegetative characteristics varied in both salinized and unsalinized plants according to the NH₄:NO₃ ratios so that the lowest reduction was observed with the 50:50 (NH₄:NO₃) ratio. Increased NH₄ up to 50 percent (50:50) of total N, promotes the yield at both salinized and unsalinized plants. In both salinized and unsalinized plants, the increased NH₄ and NO₃ ratio in the nutrient solution reduced the photosynthetic (Pn) rate and stomatal conductance; however, the reduction in Pn rate was severely impaired at a higher ratio of NH₄ in the nutrient solution. In both salinized and unsalinized plants, the 75:25 ratio had the lowest potassium (K) and sodium (Na) content; however, the K/Na ratio was the highest in 50:50 ratio. An increase of NH₄ in the solution led to a significant increase in NH₄ content in both salinized and unsalinized plants. Salinity increased NH₄ content so that the salinized plant had nearly twice as high NH₄ content in the leaves. The activity of nitrate reductase was increased by increasing NH₄ from 0 to 50% and then reduced at a higher ratio of NH₄ in the solution. The activities of antioxidative enzymes increased in salinized plants regardless of the NH₄:NO₃ ratios. In salinized plants, the activities of superoxide dismutase and catalase enzymes were increased by 44.4 % and 97.5%, respectively. Within salinized and unsalinized treatments, the highest activities of all antioxidant were observed in 75:25 ratio, while they remained unchanged for all NH₄:NO₃ ratios. The increased NH₄ content in the solution increased the oil content and the maximum oil content in both salinized and unsalinized plant was obtained in both 50:50 and 75:25 ratios. The percentage of oleic acid was affected by both salinity and NH₄:NO₃ ratios. The ratios of NH₄:NO₃ had no effect on the protein content; however, salinity reduced the protein content by 20%.     

丛枝菌根真菌对青稞生长发育及磷营养的影响研究

青稞是大麦类作物中的一种，是西藏地区栽培面积最大、产量最多、分布最广的农作物品种。近年来，青稞的保健作用（富含-β葡聚糖和“生育三烯酚”）已得到国内外公认，因而青稞生产受到更广泛的关注。然而，根据西藏首次土壤资源调查结果，全自治区低磷（速效磷〈10mgkg^-1）土壤占总耕地面积的46．9％～72．3％（内部资料）。土壤供磷不足是限制青稞高产的重要潜在因素之一，同时西藏目前没有一家化肥厂，生产、科研所需肥料全靠从内地长途运输。寻找一条经济有效的途径缓解西藏地区农业生产肥料紧缺的状况成为一项迫切的任务。     

丛枝菌根真菌对污染土壤中农产品质量安全的影响

丛枝菌根(Arbuscular mycorrhiza,AM)是自然界中分布最广的一类菌根,常见于各种类型的污染土壤中,如重金属污染土壤、有机污染土壤及复合污染土壤。AM真菌能与陆地上绝大多数的高等植物共生,大多数的农作物如粮食作物、果树、蔬菜等均能形成菌根。研究表明,AM真菌完全能在提高污染土壤中农产品质量安全方面发挥作用,主要体现在:(1)促进有机污染物的降解和转化,降低污染物在土壤和农产品中的残留;(2)提高农作物对重金属的耐性,降低重金属在农产品中的积累;(3)改善农作物营养状况,提高其抗病性,降低肥料、农药施用量,从而间接降低污染物在土壤和农产品中的残留。因此,AM真菌在提高农产品质量安全方面具有较大潜力。当前和今后可在以下几个方面开展工作:(1)筛选和驯化能显著降低农产品中污染物的AM真菌菌株;(2)AM真菌提高农产品质量安全的效应与机制;(3)AM真菌和其他生物农药、生物肥料间的相互作用;(4)AM真菌在农产品生产中的应用基础研究等。     

ARBUSCULAR MYCORRHIZAL FUNGI AND PIRIFORMOSPORA INDICA INDIVIDUALLY AND IN COMBINATION WITH RHIZOBIUM ON GREEN GRAM

Three species of AM fungi, Glomus mosseae, Glomus microcarpum, Gigaspora margarita and a fungus that mimics the properties of AM fungi, Piriformospora indica, were tested on green gram [Phaseolus aureus Roxb. (= Vigna radiata var. radiata)] individually and in combination with Rhizobium for their influence on growth and seed yield. The growth parameters analyzed were dry biomass, total leaf area, total chlorophyll,% root colonization, nodulation, and nitrogen, phosphorus, and potassium (NPK) content of leaf tissues using standard methodologies. Glomus microcarpum was found to be more effective in promoting biomass and seed yield when applied alone. But in combination with Rhizobium, G. mosseae enabled highest production of biomass. The tissue nitrogen content was high in G. microcarpum—Rhizobium dual inoculated plants. Many other characteristics were high in dual inoculation, while tissue P was high in individual treatment of G. mosseae. Piriformospora indica was not found to be a good synergist on green gram.     

ABUNDANCE AND DISTRIBUTION OF ARBUSCULAR MYCORRHIZAL FUNGI SPECIES IN LONG-TERM SOIL FERTILITY MANAGEMENT SYSTEMS IN NORTHERN NIGERIA

Soil fertility management systems (SFMS) can influence the community structure of arbuscular mycorrhizal fungi (AMF). Hence, long-term SFMS was studied. The SFMS comprised three legume combinations, urea application and solely maize as control. Spores were extracted by wet sieving, characterized and identified using their morphology. Interrelationships between cropping systems and occurrence of AMF species were analyzed with genotype by environment (GGE) biplot. Seventeen species were identified with Glomus species (47.05%) having highest value while Gigaspora species had the least (11.76%). Legume residues significantly (P < 0.05) increased spore population with the highest spore count (120 spores/100 g soil) obtained in plot under cowpea residue. Shannon Weiner index (H′) of maize/Lablab purpureus plot was highest (1.996) while that of sole maize system was the least (1.550). The GGE indicated Glomus intraradices as a stable species across all the SFMS. Community structure of AMF and function can be preserved using appropriate SFMS.     

不同铵硝比例对水稻铵吸收代谢基因表达的影响

以水稻南光为材料,研究了不同铵硝摩尔比例处理时,水稻NH4^＋吸收代谢基因的表达情况.档结果表明：（1）应用荧光定量PCR方法,可以精确检测水稻氮素吸收代谢基因在不同铵硝处理间的表达量变化;（2）从各基因的表达量上来看,吸收基因中以OsAMT1.1表达量最高,编码GS的基因中以OsGln1.1表达量最高,编码GOGAT的基因中,OsGlu表达量最高;（3）总体来说,不同铵硝处理对NH4^＋吸收代谢基因的表达有显著影响,吸收基因对不同铵硝比例的反应要比代谢基因更敏感;（4）氮吸收基因中OsAMT4.1显著受到NO3的抑制,NH4^＋的诱导.而OsAMT1.1,OsAMT1.2,OsAMT1.3和OsNRT2在铵硝摩尔比例由100：0变为50：50过程中,受到NO3^-的显著抑制,在铵硝摩尔比例由50：50变为0：100过程中OsAMT1.2和OsAMT1.3受到NO3^-的显著诱导,OsAMT1.1和OsNRT2变化不显著;（5）编码GS的基因OsGln1.1表达受NO3诱导,受NH4^＋抑制.OsGln2在铵硝摩尔比例由100：0变为50：50过程中,受到NO3^-增加的诱导,同时,OsGln1.2受到NO3增加的显著抑制作用,铵硝达到50：50以后,NO3^-比例的增加对OsGln1.2和OsGln2的表达没有显著影响;（6）编码GOGAT的基因OsGlt1和OsGlu在不同铵硝摩尔比例中的变化趋势一致：铵硝比例由100：0变为50：50过程中没有显著变化,铵硝比例50：50基础上表达量受到NO3^-比例增加的显著抑制,而OsGlt2的表达受NO3^-的显著抑制,NH;的显著诱导.     

两株细菌与丛枝菌根真菌联合接种对红壤中DEHP降解的影响

采用绿豆为供试植物,通过温室盆栽试验研究接种邻苯二甲酸二(2-乙基己基)酯(DEHP)降解菌与丛枝菌根(Arbuscular mycorrhiza,AM)真菌对DEHP污染土壤的修复作用以及对植物生长的影响。试验土壤中添加DEHP浓度为100mg kg-1,试验设AM真菌Acaulospora 90034、降解菌Bacillus sp.DW1和Gordonasp.DH3单独接种以及互相组合的联合接种处理,同时设置不接种的对照处理(CK)。苗后60d收获植株。结果表明,AM真菌能很好地侵染绿豆的根系。菌根侵染提高了绿豆植株的干重,同时也促进了绿豆的磷营养,但接种DW1与DH3对菌根侵染率与绿豆生长都没有显著影响。三种菌剂无论是单独或者联合接种都能显著促进土壤中DEHP的降解,但三种菌剂同时接种对DEHP的降解能起到最好的协同作用。同时,接种AM真菌也减少了DEHP在绿豆地上部分的累积,这些都为DEHP污染农田土壤的生物修复提供了理论依据。     

水分胁迫及VA菌根接种对绿豆生长的影响

本文采用土培试验研究了水分胁迫下接种VA菌根真菌Glomusmosseae,G .sp .和G .caledonium对绿豆生长及代谢活动的影响。结果表明 ,水分胁迫严重抑制了植株的生长 ,但对VA菌根真菌的侵染能力影响不大。接种VA菌根真菌不仅有利于植株对土壤中磷和氮的吸收 ,而且明显改善了植株的水分状况 ,降低了植株叶片的脯氨酸含量 ,提高了接种株叶片的光合效率 ,显著增加了植株干物质量 ,增强了绿豆的抗旱性或耐旱性。 3种真菌中 ,以Glomusmosseae的接种效果最好。     

氯化胆碱与高效硝铵复合肥对玉米和水稻某些生理性状和产量的影响

玉米、水稻经叶面喷施氯化胆碱(CC)和高效硝铵复合肥(硝饺肥)后,叶片叶绿素含量,比叶重,硝酸还原酶(NR),ATP酶,以及玉米的磷酸烯醇式丙酮酸羧化酶(PEPC)和苹果酸酶等的活性均有不同程度的提高。从而促进了光合作用,使产量有所提高。CC和硝铵肥混合使用时,效果更好。     

丛枝菌根真菌对西藏高原草地植物和土壤环境的影响

采用三室隔网装置，就Glomus etunicatum、Glomus intraradices、Glomus mossecte对2种高山草地植物和土壤环境的影响进行了研究。结果表明：（1）接种AM真菌对草地植物的侵染和生长均具显著效应，植株地上部、根系干物重以及含磷量、吸磷量均显著高于不接种处理，菌根菌丝对植株吸磷的贡献率达47.8％-69．5％。其中，Glomus intraradices、Glomus mosseae分别对穗序剪股颖、紫羊毛吸收土壤磷索更具促进作用。（2）各接种处理中室土壤中各类微生物数量均显著高于边室土壤，但边室土壤中放线菌，特别是细菌、真菌的平均增幅均远高于中室土壤，表明菌根际、菌丝际土壤中各类微生物的数量差异趋于明显缩小，微生物区系构成得以平衡与改善；解磷细菌（芽孢杆菌）亦呈同一趋势。（3）2—1 mm粒径团聚体在土壤水稳性团聚体构成中占有绝对比重，菌根菌丝对距根表不同距离处2—1 mm团聚体形成的贡献率均在70％以上，但距根表2—4cm处菌根菌丝贡献率明显低于0-2、4-6cm处，并未表现出随菌丝密度增加而提高的趋势；5—2mm水稳性团聚体仅距根表较远处有少量形成（菌丝贡献率达100％），0-2、2—4cm处则未见分布。（4）同一、不同AM真菌对不同或同一草地植物的侵染及所产生的菌根效应具有不同程度的差异，穗序剪股颖各接种处理普遍优于紫羊毛，紫羊毛＋Glomus mosseae、穗序剪股颖＋Glomus intraradices优于同组其他接种处理的趋势较为明显。     

丛枝菌根真菌对羊草气体交换和δ~(13)C、δ~(15)N的组成影响

采用盆栽方法研究接种两种丛枝菌根真菌Glomus intraradices,Glomus claroidum对内蒙古典型草原优势种羊草(Leymus chinensis)的气体交换和稳定性同位素组成的影响,对羊草生长第45、60和75天的测定结果表明,丛枝菌根真菌能提高植株的含磷量、叶片的气孔导度和光合速率,降低植株δ15N值,但对羊草的内在水分利用效率和δ13C的组成未产生显著影响;植株生长的不同时期对其气体交换和稳定性同位素δ13C、δ15N均产生显著影响;时间和接种的相互作用显著影响植株的光合速率、δ13C和δ15N;羊草气孔导度和光合速率的提高归因于菌根真菌改善植株磷营养和增加根系碳分配所致;而植株内在水分利用效率和δ13C无显著性差异是因为气孔导度和光合速率总是发生同方向变化造成的;菌根植物具有较低δ15N是源于菌根真菌吸收N,并富集15N,转运给植株贫化的15N所致。试验结果为认识草原植物的碳水平衡和N循环提供了新的思路和借鉴。     

硝酸镧浸种对水稻发芽和幼苗生长的效应

用不同浓度的硝酸镧溶液,处理汕优桂99(三系品种)、桂光一号(二系品种)和广桂110(常规品种)3个水稻品种的种子。结果表明:对汕优桂99和桂光一号有促进芽生长、抑制根生长的作用;对广桂110前期有促进根生长,后期有促进菌生长的作用。3个水稻品种的种子经硝酸镧处理后,对α-淀粉酶活性、呼吸速率和光合速率均有不同程度的增强效应.     

INFLUENCE OF ORGANIC AND MINERAL FERTILIZATION ON GERMINATION,LEAF NITROGEN,NITRATE ACCUMULATION AND YIELD OF VEGETABLE AMARANTH

The influence of manure and diammonium phosphate (DAP) mineral fertilizer on germination, leaf nitrogen content, nitrate accumulation and yield of vegetable amaranth (Amaranthus hypochondriacus) was investigated. Field trials were set up at the University of Nairobi Field Station at the Upper Kabete Campus during the long rains of March–May in 2007 and 2008. Trials were laid out as complete randomized block design with four fertilization treatments: 20, 40, and 60 kg nitrogen (N) ha^?1 supplied by DAP (18:46:0), 40 kg N ha^?1 supplied by cattle manure and an unfertilized control variant. The vegetables were harvested at three maturity stages at 6, 7, and 8 weeks after planting. Results indicated that there were significant differences between treatments in germination percentage, leaf nitrogen content, nitrate accumulation and vegetable yield. Plants that received manure had a higher germination percentage than those that received the same amount of N supplied by the chemical fertilizer DAP. The yields generally increased from week 6 to week 8. The highest yield was recorded in plots receiving 40 kg N ha^?1 from DAP at eight weeks after planting. Plots that were supplied with manure recorded the lowest yield when compared to the fertilizer treated plots at all rates. Leaf nitrogen content increased with increasing rate of N but only when N was supplied by DAP fertilizer. The leaf nitrogen content decreased with increasing age of the plants. The leaf nitrate content increased with increase in DAP application rate. Results indicate that manure application produced quality vegetables in terms of low nitrate levels, but leaf nitrogen and vegetable yields were low. DAP application effected higher yields, but the vegetables had high though acceptable nitrate levels.     

再生水灌溉对草坪草生长和土壤的影响

随着城市绿地与人争水的问题日益突出,再生水作为替代水资源在草坪草上的应用日益广泛。本试验于2003-2005年用3种类型灌溉水(清水、“清水+再生水”、再生水)处理5种草坪草(草地早熟禾、高羊茅、结缕草、野牛草和山麦冬),从观赏品质和生长指标方面进行耐污性评价,并分析再生水对土壤的影响。结果表明:本研究使用的再生水对所供测试绿化草种的颜色、覆盖度、质地和均匀性无不良影响,再生水灌溉条件下,高羊茅表现出了最强的综合耐污能力,其次是结缕草和野牛草。灌溉水类型对于草坪草的生长指标的影响具有种的特异性。再生水灌溉和“清水+再生水”交替灌溉提高了土壤的阳离子交换量(CEC)和总孔隙度,有利于土壤物理性状的改善。     

硝酸钾和硫酸钾对番茄幼苗生长、根系形态及钾素吸收和生理利用效率的影响

采用水培试验,研究不同钾肥种类(KNO3、K2SO4)、不同钾素水平(0、2.0、4.0和8.0mmol/L)对"天福冠露"和"毛粉802"2个番茄品种幼苗生长、根系特征及对钾素吸收、生理利用效率的影响。结果表明,随钾素水平提高,番茄鲜重、干重以及根长、根体积、根直径等根系特征显著提高。在钾素水平为4.0、8.0mmol/L时,硝酸钾处理的番茄株高、根长显著高于硫酸钾。钾素水平为8.0mmol/L时,硫酸钾根直径显著高于硝酸钾处理的;"天福冠露"施用硝酸钾的根尖数显著高于施用硫酸钾;"毛粉802"施用硫酸钾,植株的根直径、钾含量和钾素积累量显著高于硝酸钾处理。番茄水培适宜的钾素浓度为8.0mmol/L,硝酸钾有利于番茄生长发育,硫酸钾有利于番茄对钾素的吸收。在相同钾素水平条件下,2个番茄品种鲜重、干重均无显著差异。     

INFLUENCE OF THE SPATIAL DISTRIBUTION OF NITRATE ON THE UPTAKE OF N BY PLANTS: A REVIEW AND A MODEL FOR ROOTING DEPTH

Published literature is re-examined in an attempt to understand the influence of the spatial distribution of soil nitrate on N uptake in order to devise a simple method for estimating the depth to which nitrate must be leached before it becomes unavailable to the crop. The evidence suggests that most crops can continue normal growth with less than 15% of their roots exposed to nitrate. A simple model of nitrate uptake is constructed in which nitrate is assumed to be totally available above a set depth and totally unavailable below it. This effective rooting depth is assumed to coincide with the depth at which uptake per unit length of root declines to half of the maximum rate. Estimates of effective rooting depth have been made from root distribution data for various vegetable crops grown at Wellesbourne and cereal crops at Rothamsted. The results were found to fit a simple regression equation which can be used to calculate effective rooting depths at any stage of growth from the dry weight and population density of the crop and the mean cross-sectional area of its roots. This equation is used in the succeeding papers to estimate the effects of leaching on the N fertilizer needs of crops.     

ARBUSCULAR MYCORRHIZA,AZOSPIRILLUM AND CHEMICAL FERTILIZERS APPLICATION TO BABY CORN (ZEA MAYS L.): EFFECTS ON PRODUCTIVITY,NUTRIENTS USE EFFICIENCY,ECONOMIC FEASIBILITY AND SOIL FERTILITY

The study was investigated at Agricultural Experimental Farm, Giridih, India during winter seasons of 2007–2008 and 2008–2009. Plants grown with 100% recommended dose of fertilizer (RDF) [nitrogen (N): phosphorus pentoxide (P₂O₅): potassium oxide (K₂O) = 150:60:60 kg ha^?1] + AM + Azospirillum (T₁₅) produced maximum chlorophyll, baby cob, and green fodder yield. Root biomass was highest with application of 150% RDF + arbuscular mycorrhizae (AM) + Azospirillum (T₁₆). Co-inoculated plants produced higher chlorophyll, root biomass resulted higher cob and green fodder yield. Biofertilizers supplied along with chemical fertilizers saved 70, 29, and 33 kg N, P₂O₅ and K₂O per hectare, respectively. Nutrient (NPK) uptake was greatest in T_15. Residual soil fertility in terms of NPK was recorded maximum in T_16. Although, co-inoculated plots built up higher residual soil fertility as compare to sole inoculation. Nutrients use efficiency and benefit cost ratio were higher due to application of 50% RDF with co-inoculants. T₁₆ was most costly whereas T₁₄ (50% RDF + AM + Azospirillum) was most beneficial.     

INFLUENCE OF HIGH TEMPERATURE AND UREA FERTILIZATION WITH N-(N-BUTYL) THIOPHOSPHORIC TRIAMIDE AND DICYANDIAMINDE ON COTTON GROWTH AND PHYSIOLOGY

The objective of this growth chamber study was to evaluate the effect of adding N-(n-butyl) thiophosphoric triamide (NBPT) and dicyandiaminde (DCD) to urea fertilizer, on the physiology and growth of cotton (Gossypiumhirsutum L.) under normal and high temperatures. Treatments consisted of two day temperature regimes, 30°C and 38°C, and five nitrogen fertilization applications: unfertilized control, 125 kg ha^?1 of urea, 93 kg ha^?1 of urea, 93 kg ha^?1 urea + NBPT, and 93 kg ha^?1 urea + NBPT + DCD. The addition of NBPT to urea fertilizer had positive effects on leaf chlorophyll, leaf area, dry matter, nitrogen (N) uptake, and N use efficiency. The absence of a significant interaction effect indicated that N fertilization was not influenced by temperature. Deficiency of N significantly decreased leaf chlorophyll, increased glutathione reductase, decreased protein and increased leaf nitrate reductase. Physiological changes under high temperature included increased plant N uptake, glutamine synthetase, leaf chlorophyll, protein content, plant height and leaf area were due to high N uptake and utilization.