牛粪好氧发酵挥发性物质排放特征及恶臭物质分析

不同原料好氧发酵产生的臭气物质组分和浓度存在差异。以牛粪和玉米秸秆为原料研究好氧发酵过程挥发性有机物（Volatile Organic Compound，VOCs）的产排特征及主要致臭物质，开展牛粪好氧发酵试验，采用气相色谱-质谱法分析测定发酵升温期、高温期、降温期及腐熟期等不同发酵阶段的VOCs组分和浓度，硼酸溶液吸收，盐酸滴定法测定NH3，便携式检测器（Tion NH3-H2S 300 G）测定H2S，3点比较式臭袋法测定不同发酵阶段臭气浓度。结果表明，牛粪好氧发酵过程中共检出31种VOCs，其中含硫化合物42种，醇类1种，酯类1种，酮类1种，卤代烃4种，苯系物9种，烷烃类8种，烯烃3种；在好氧发酵高温期臭气浓度最高为724（无量纲），VOCs产生与排放主要在高温期。基于恶臭污染排放标准和恶臭物质气味活度值，并结合各物质检出率、GS-MS图谱及相关性分析，发现NH3、H2S、甲硫醚是牛粪好氧发酵过程的主要致臭物质；其次芳香族化合物对臭气浓度贡献也相对较大，应进行重点监测与控制。该研究可为牛粪好氧发酵过程臭气物质减控提供理论支撑。     

猪粪好氧发酵过程中挥发性有机物组分分析及致臭因子的确定

为了控制猪粪好氧发酵中产生的挥发性有机物(volatile organic compounds)及主要致臭物质,开展了猪粪好氧发酵试验,通过连续监测猪粪好氧发酵过程中所排放的挥发性气体,研究猪粪好氧发酵中产生的VOCs组分及其致臭因子。研究表明,在猪粪好氧发酵过程中共产生33种挥发性物质,除氨气和硫化氢外,共有31种VOCs,包括芳香烃12种,醛类8种,硫醇硫醚类4种,卤代烃4种,酮类2种,胺类1种;猪粪好氧发酵中主要致臭物质为:二甲二硫、甲硫醚、二甲三硫、乙醛和硫化氢,并建议将甲硫醚作为猪粪好氧发酵中产生的恶臭污染指示物。该研究可为猪粪堆肥过程中恶臭物质的监测、制定控制策略提供参考。     

病死猪辅热好氧发酵尾气中的恶臭物质分析

为了明确病死猪辅热好氧发酵过程中产生的恶臭气体的种类及其排放规律,为控制恶臭气体排放浓度、降低病死猪无害化处理过程对环境的污染提供基础依据,该研究以病死猪为发酵原料,玉米秸秆为辅料,开展病死猪辅热好氧发酵试验,发酵过程中,采集处理槽排放的尾气,分析尾气中的有机恶臭物质组分并测定其排放浓度,同时测定其中的氨气浓度,并对不同发酵阶段尾气中气味活度值大于1的恶臭物质进行相关性分析和主成分分析。结果表明：在病死猪辅热好氧发酵过程中共检出36种恶臭物质,其中能准确定性与定量检测的有19种,包括3种含硫化合物,1种烷烃化合物,12种芳香烃化合物,1种酚类化合物,1种胺类化合物和1种无机气体;发酵全程或部分时间点超过其嗅阈值的有3-乙基甲苯、4-乙基甲苯、二甲基二硫醚、二甲基硫醚、氨气、对甲酚、甲硫醇、三甲胺8种,达到的最高浓度依次为0.241、0.350、0.247、0.280、69.06、0.041、0.314、0.033 mg/m3,与其嗅阈值的比值依次为2.745 7、8.634 7、29.325 6、36.981 5、66.669 1、173.314 5、374.77、432.471 1;各发酵阶段的主要致臭物质成分存在差异：在0～12 h的发酵阶段,三甲胺、甲硫醇、二甲基硫醚、二甲基二硫醚、氨气、对甲酚、3-乙基甲苯、4-乙基甲苯为主要致臭物质,在12～36 h的发酵阶段,三甲胺、甲硫醇、二甲基硫醚、二甲基二硫醚、氨气、对甲酚为主要致臭物质,在36～72 h的发酵阶段,三甲胺、甲硫醇、二甲基硫醚、二甲基二硫醚、氨气为主要致臭物质;不同发酵阶段的臭气强度存在较大波动：在0～72 h内的发酵过程中,0～3 h内臭气强度缓慢增强,但第6小时臭气强度有明显下降,在6～18 h时再次增强,第18小时臭气强度达到峰值,18～72 h内持续下降直至平稳。该研究可为病死猪辅热好氧发酵过程中恶臭物质的减控策略提供理论参考。     

生活垃圾堆肥过程中恶臭物质分析

恶臭污染已成为生活垃圾堆肥过程中的主要环境问题.以15~80 mm粒径段的生活垃圾作为研究对象,利用嗅觉测定法和GC-MS分析了不同阶段堆肥尾气的臭气浓度和恶臭化合物的种类及其排放浓度,并对不同堆肥阶段臭气浓度和恶臭物质排放浓度的相关性进行分析.结果表明,垃圾堆肥过程中共检测到50种挥发性有机物,其中含硫恶臭物质5种,烃类化合物25种,芳香烃类化合物14种,其他物质6种.通过相关性分析,发现硫化氢、甲硫醚、二硫化碳、二甲二硫、1,3二甲基苯和邻二甲苯均与臭气浓度呈极显著相关(p<0.01),结合各恶臭物质的嗅阈值,15~80 mm粒径段垃圾堆肥过程中恶臭物质优先控制的顺序为硫化氢>甲硫醚>二甲二硫>二硫化碳>1,3二甲基苯>邻二甲苯.甲硫醇的嗅阈值非常低,即使其排放浓度很低,也会带来严重的臭气污染;NH3虽然对臭气浓度的贡献相对较小,但是其排放量很大,因此也应该对这2种恶臭物质进行重点监测和控制.该研究结果为生活垃圾堆肥过程中恶臭物质的监测、制定控制策略提供参考.     

猪粪堆肥挥发性有机物的产生规律与影响因素

堆肥是畜禽粪便处理及资源化利用的有效途径,然而堆肥过程中极易产生挥发性有机物(VOCs,volatile organic compounds),引发恶臭问题,并对人体健康带来危害。该研究以猪粪和秸秆为原料,通过堆肥试验,研究了含水率、碳氮比和通风速率等工艺参数对猪粪堆肥过程中主要VOCs产生的影响。研究结果表明:堆肥过程中TVOCs的最高体积分数可达2 000×10~(-6)以上,主要在堆肥升温期产生。二甲二硫、二甲三硫是主要的致臭VOCs,其中,影响二甲二硫排放的主要因素为物料初始含水率,影响二甲三硫排放的主要因素为通风速率。极差及方差分析结果表明,堆肥过程中采用含水率65%,碳氮比30,通风速率0.1 m~3/(min·m~3)可以有效控制VOCs的排放。     

生物过滤法去除死猪堆肥排放臭气效果的中试

为研究生物过滤法去除死猪堆肥发酵处理过程产生臭气以及挥发性有机物(volatile organic compounds,VOCs)的可行性,开展了死猪和猪粪混合堆肥试验,分析了死猪堆肥过程臭气浓度特性和VOCs组分特征,对生物过滤法去除臭气中VOCs的工艺关键参数-停留时间进行优化试验。死猪堆肥过程中排放VOCs种类达37种,其中主要致臭组分为三甲胺、二甲基硫、二甲基二硫、二甲基三硫;以腐熟猪粪堆肥作为滤料(添加3%活性污泥),在停留时间为30~100 s的条件下,生物过滤法对死猪堆肥排放臭气去除率达90%以上;停留时间60~100 s的条件下对VOCs中主要致臭组分的去除效率达82.2%~100%,生物过滤法去除死猪堆肥过程臭气浓度和VOCs的优化停留时间为60 s。研究结果能为死猪堆肥发酵过程排放臭气的处理和控制技术进一步研发提供科学依据。     

畜禽粪含氮臭气成分的排放及其影响因素

氨和三甲胺是畜禽粪恶臭气体中的两种含氮臭气成分 ,畜禽粪排放的氨、三甲胺的体积分数分别达到1×10-6、0.02×10-6 时便可引起恶臭。畜禽粪在90d内的氨挥发量占粪便总量的0.007 %—0.354 %,其中以鸡粪最高、马粪最低。碳氮比、微生物以及化学物质和天然物质的添加物对畜禽粪含氮臭气成分的排放有直接影响。     

风干预处理对堆肥腐熟度及臭气排放量的影响

该研究以风干猪粪堆肥为处理,以新鲜猪粪堆肥为对照,在秸秆调理相同C/N基础上,对两个处理腐熟度和臭气排放进行比较分析。从温度、p H值、电导率和发芽率来看,利用新鲜猪粪和风干猪粪堆肥所得的产品均能达到腐熟和无害化标准;在硫化氢、羰基硫、二硫化碳、甲硫醚、乙硫醚、二甲二硫、甲硫醇和乙硫醇几种含硫臭气中,甲硫醚和二甲二硫占96%以上;风干猪粪堆肥比新鲜猪粪堆肥少排放71.09%的氨气,66.11%的甲硫醚和9.66%的二甲二硫。在不考虑风干环节存在的问题条件下,与新鲜猪粪堆肥相比,风干猪粪堆肥堆肥时间短,在堆肥品质提高的基础上,堆肥产品产量增加60%。通过降低水分和体积风干猪粪运输成本降低1/3,且对环境影响小,是远距离资源化处理畜禽粪便的较好途径。     

牛粪和玉米秸秆混合好氧堆肥过程分层规律

好氧堆肥过程常存在分层现象,对于发酵产物的均一性和整体质量存在影响。为探究好氧堆肥物料病原菌灭活的分层情况,该研究以不翻抛（T1）为对照组,设置3组好氧堆肥试验（T2高温期翻抛、T3降温期翻抛、T4高温期和降温期翻抛）,对牛粪好氧堆肥过程中常规理化性质和病原菌去除效率等进行分析,并利用克里格法（KRIGING）对堆体不同位置的温度和含水率进行插值分析。结果表明,4个处理发酵温度均达到了《畜禽粪便堆肥技术规范》要求,高温期最长的处理为T3和T4,达到7 d,T4处理的病原菌去除率最高,达到97.15%;从分层规律来看,堆体含水率从高到低为上层、中层、下层;好氧堆肥物料病原菌去除效率顺序从高到低为中层、下层、上层,4个处理病原菌去除率均不低于95.56%。综合考虑,高温期和降温期翻抛（T4处理）更有利于牛粪和秸秆混合堆肥物料整体实现无害化。该研究可为牛粪好氧堆肥过程中病原菌杀灭和翻抛参数的优化提供技术指导。     

蔬菜废弃物循环堆肥的性能及经济效益评价

蔬菜废弃物含水率高,在堆肥堆制中需要添加大量高碳低水辅料进行调节,生产成本高,资源化利用率低,为了研发适用于消纳高含水率蔬菜废弃物的好氧堆肥发酵工艺体系以促进废弃物高效资源化利用,通过设置传统好氧堆肥和循环堆肥两组试验,研究蔬菜废弃物循环堆肥的性能,评价其工艺的可行性和经济效益。结果表明:在第一、二次循环过程中,堆肥性能稳定,堆体升温迅速,高温期分别持续10、5d;在第三次循环中,系统稳定性开始波动,温度≥50℃保持5d,第四次循环堆肥系统恶化,堆体无法达到50℃,终止循环过程。循环堆肥物料最终pH值为6.72、电导率值为3.43mS·cm-1,种子发芽指数为72.0%,满足无害化标准要求,不会对植物产生毒害。循环堆肥能使蔬菜废弃物迅速脱水,并将堆体水分保持在50%～60%的最佳范围以利于有机物质的降解,4次循环蔬菜废弃物最高降解率分别为92.9%、88.6%、59.4%、21.7%。经济效益分析表明,与常规堆肥相比较,循环堆肥辅料用量及成本减少48.8%,同时,添加同量的辅料,循环堆肥能消纳更多的蔬菜废弃物,其利润是常规堆肥的7.15倍。综上所述,循环堆肥工艺可行、性能稳定,最大循环次数为3次,辅料应用量少,利润高,是处理高含水率蔬菜废弃物经济可行的技术。     

低氮和干旱胁迫对富士和秦冠生长及氮素利用的影响

【目的】以富士（Fuji）、 秦冠（Qinguan）嫁接在平邑甜茶（Malus hupehensis Rehd.）上的当年生盆栽苗为试验材料,采用砂培方法,研究了缺氮胁迫和干旱对富士和秦冠生长情况、 光合参数、 植株各部位氮磷钾含量及氮素利用效率的影响,分析比较了低氮干旱条件下富士和秦冠生长及氮素利用的差异,以期为果树生产高效肥水利用提供理论指导。【方法】试验共设四个处理: 正常氮正常水（ZZ）、 低氮正常水（DZ）、 正常氮干旱（ZG）、 低氮干旱（DG）。氮素和水分均设置两个水平,分别为正常氮（6 mmol/L NO-3-N）、 低氮（0.3 mmol/LNO-3-N）、 正常供水（保持盆中砂子相对含水量为饱和含水量的80%~85%）、 干旱处理（保持盆中砂子相对含水量为饱和含水量的60%~65%）。【结果】富士和秦冠的生物量（茎和叶）、 株高茎粗等生长指标以及光合速率、 气孔导度、 蒸腾速率均为正常氮正常水（ZZ）＞低氮正常水（DZ）＞正常氮干旱（ZG）＞低氮干旱（DG）,并且相对应处理下秦冠的以上指标均高于富士;正常供水下,缺氮处理使富士、 秦冠的根冠比比正常氮处理均有所增加,富士提高了2.05%,秦冠提高了22.40%。富士和秦冠的氮、 磷、 钾含量均表现出正常氮正常水（ZZ）＞低氮正常水（DZ）＞正常氮干旱（ZG）＞低氮干旱（DG）; 氮、 钾元素含量在植株各部位的分布顺序依次是叶＞根＞茎,磷元素则是根＞叶＞茎;光合氮素利用效率（PNUE）和氮素利用效率表现为秦冠处理之间差异极显著,富士处理之间差异不显著;秦冠的PNUE和NUE明显高于富士,在低氮正常水（DZ）处理下,秦冠氮肥利用率比富士高42.07%,在低氮干旱（DG）处理下高64.14%;低氮胁迫下富士和秦冠的NUE显著提高,并且秦冠提高的幅度高于富士。【结论】施用氮肥能够显著提高富士与秦冠的干物质量,同等水肥条件下,秦冠生长优于富士;水分亏缺会减少叶片对氮的吸收,干旱条件下适度增施氮肥,可提高果树的抗旱能力;低氮干旱胁迫下秦冠的生长指标、 光合指标及氮素利用效率指标均优于富士,表现出较强的抗低氮干旱胁迫的能力。     

Pasture Vegetation Elemental Analysis by Laser-Induced Breakdown Spectroscopy

Laser-induced breakdown spectroscopy (LIBS) is a new technique for the analysis of plant material. This study investigates the application of LIBS to pasture-based plant samples. The LIBS measurements were obtained from pelletized pasture samples (100 samples) that had been also analyzed by inductively coupled plasma–optical emission spectroscopy (ICP-OES) following microwave digestion for calibration and comparison purposes. Comparisons for elements sodium (Na), potassium (K), magnesium (Mg), calcium (Ca), manganese (Mn), iron (Fe), copper (Cu), zinc (Zn), boron (B), phosphorus (P), and sulfur (S) showed that LIBS could be used for almost all the standard profile total elements with concentrations down to low mg/kg levels (observed error of Na: 0.024 percent, K: 0.18 percent, Mg: 0.016 percent, Ca: 0.073 percent, P: 0.017 percent, Mn: 31 mg/kg, Fe: 150 mg/kg, Zn: 6.6 mg/kg, and B: 1.1 mg/kg). Elemental analysis at less than mg/kg levels was not possible using LIBS. The elements S and Cu were particularly difficult to analyze with reliability using LIBS at the concentration levels found in the plant samples. Replacing microwave digestion and subsequent ICP analysis with a direct analysis of dried plant samples using LIBS has the potential to improve the productivity and reduce the cost of testing.     

Faculty positions:Center for Agricultural Resources Research,Chinese Academy of Sciences

正The Center for Agricultural Resources Research(CARR),the Institute of Genetics and Developmental Biology(IGDB),Chinese Academy of Sciences,invites applicants for several research group leader positions.CARR is one of the research organizations in Chinese Academy of Sciences(CAS).We seek nominations and applications from individuals who have expertise and a record of accomplishment in research areas related to ecology,agro-hydrology,     

Macroinvertebrates in North American tallgrass prairie soils: effects of fire, mowing, and fertilization on density and biomass

The responses of tallgrass prairie plant communities and ecosystem processes to fire and grazing are well characterized. However, responses of invertebrate consumer groups, and particularly soil-dwelling organisms, to these disturbances are not well known. At Konza Prairie Biological Station, we sampled soil macroinvertebrates in 1994 and 1999 as part of a long-term experiment designed to examine the effects and interactions of annual fire, mowing, and fertilization (N and P) on prairie soil communities and processes. For nearly all taxa, in both years, responses were characterized by significant treatment interactions, but some general patterns were evident. Introduced European earthworms (Aporrectodea spp. and Octolasion spp.) were most abundant in plots where fire was excluded, and the proportion of the total earthworm community consisting of introduced earthworms was greater in unburned, unmowed, and fertilized plots. Nymphs of two Cicada genera were collected (Cicadetta spp. and Tibicen spp.). Cicadetta nymphs were more abundant in burned plots, but mowing reduced their abundance. Tibicen nymphs were collected almost exclusively from unburned plots. Treatment effects on herbivorous beetle larvae (Scarabaeidae, Elateridae, and Curculionidae) were variable, but nutrient additions (N or P) usually resulted in greater densities, whereas mowing usually resulted in lower densities. Our results suggest that departures from historical disturbance regimes (i.e. frequent fire and grazing) may render soils more susceptible to increased numbers of European earthworms, and that interactions between fire, aboveground biomass removal, and vegetation responses affect the structure and composition of invertebrate communities in tallgrass prairie soils.     

Variation in quality parameters between and within 14 Nordic tree fruit and berry species

Abstract

A 3-year study was carried out to investigate quality parameters in 14 tree fruit and berry species grown in southern Norway. The species were blueberry, apple, aronia, sour cherry, sweet cherry, red raspberry, strawberry, blackcurrant, gooseberry, red currant and elderberry, harvested along with wild bilberry, cloudberry and lingonberry. Significant differences between species were identified for all quality parameters. The coefficient of variation between species was lowest for pH (12.5%), dry matter (18.9%) and soluble solids (25.3%), followed by titratable acids (59.3%), total phenolics (83.8%), antioxidant capacity FRAP (85.7%) and antiradical power by the DPPH-assay (97.8%), total monomeric anthocyanins (132%) and ascorbic acid (137%). Average coefficient of variation within species were lower and ranged from 4 (pH) to 62% (ascorbic acid). Only the FRAP values were significantly affected by harvesting year with lower levels in 2004 than in 2005 and 2006. There were significant interactions between species and harvesting year for dry matter, soluble solids, pH, ascorbic acid and FRAP. The results indicate generic ranges in composition within species independent upon growing location and climate, and the composition of the tree fruits and berries is not likely to deviate from these ranges. It is concluded that desirable composition of tree fruits and berries and their products should primarily be achieved by selection among species rather than searching fors broadened variation within individual species.     

Potassium Fixation and Release Characteristics in Rhizosphere and Nonrhizosphere Soils for a Rapeseed–Rice Cropping Sequence

Potassium (K) fixation and release in soil are important factors in the long-term sustainability of a cropping system. Changes in K concentration and characteristics of K fixation and release in rhizosphere and nonrhizosphere soils in the rapeseed (Brassica napus L.)–rice (Oryza sativa L.) rotation were investigated using a rhizobox system. The concentrations of different forms of K in both rhizosphere and nonrhizosphere soils decreased with plants compared to without plants, regardless of K fertilizer application. Potassium uptake by crops mainly came from the rhizosphere soil. In the treatment without K fertilizer (–K), the main form of K supplied by the soil to the crops was 1.0 mol L^?1 nitric acid (HNO₃) nonextractable K, followed by nonexchangeable K, and then exchangeable K. In the treatment with K fertilizer (+K), the main K forms supplied by the soil to the crops were exchangeable K and nonexchangeable K. The amount and rate of K fixation after one cycle of the rapeseed–rice rotation was greater in rhizosphere soil than in nonrhizosphere soil. The amount and rate of K fixation of soil in the +K treatment were significantly less than in the –K treatment. The cumulative amounts of K released with 1.0 mol L^?1 ammonium acetate (NH₄OAc) and 1.0 mol L^?1 HNO₃ extraction increased with the increasing numbers of extractions, but the K-releasing power of soil by successive extraction decreased gradually and finally became almost constant. The release of K was less in rhizosphere soil than in nonrhizosphere soil. The release of K in the +K treatment was similar to that in the –K treatment in rhizosphere soil, but the K release in nonrhizosphere soil was greater with the +K than the –K treatment. Overall, the information obtained in this study will be helpful in formulating more precise K fertilizer recommendations for certain soils.     

Electron donor and pH relationships for biologically enhanced dissolution of chlorinated solvent DNAPL in groundwater

Biologically enhanced dissolution offers a method to speed removal of chlorinated solvent dense non-aqueous-phase liquid (DNAPL) sources such as tetrachloroethene (PCE) and trichoroethene (TCE) from aquifers. Bioremediation is accomplished by adding an electron donor to the source zone where fermentation to intermediates leading to acetic acid and hydrogen results. The hydrogen and possibly acetic acid are used by dehalogenating bacteria to convert PCE and TCE to ethene and hydrochloric acid. Reductive dehalogenation is thus an acid forming process, and sufficient alkalinity must be present to maintain a near neutral pH. The bicarbonate alkalinity required to maintain pH above 6.5 is a function of the electron donor: 800 mg/L of bicarbonate alkalinity is sufficient to achieve about 1.2 mM TCE dechlorination with glucose, 1.7 mM with lactate, and a much higher 3.3 mM with formate. Laboratory studies indicate that in mixed culture, formate can be used as an electron donor for complete conversion to ethene, contrary to pure cultures studies indicating it cannot. Various strategies can be used to add electron donor to an aquifer for DNAPL dehalogenation while minimizing pH problems and excessive electron donor usage, including use of injection-extraction wells, dual recirculation wells, and nested injection-extraction wells.     

Biodiversity and ecogeography of wild Lactuca spp. in some European countries

Staff members of the Department of Botany of Palacký University in Olomouc and Gene Bank Department – Workplace Olomouc, Research Institute of Crop Production in Prague, Czech Republic, conducted an expedition in seven European countries (Austria, Czech Republic, France, Germany, Italy, the Netherlands, Switzerland) in August/September 1999 to collect wild Lactuca spp. germplasm and study its geographic distribution, ecology and biodiversity. During the mission, more than 600 locations were visited resulting in the collection of 602 seed samples (accessions) of wild Lactuca species and 13 seed samples of related genera (Chondrilla and Mycelis). Lactuca serriola f. serriola, L. serriola f. integrifolia, L. saligna and L. viminea subsp. chondrilliflora were prevalent in southern Europe (Italy, France), however, only L. serriola was common in central and western Europe (Austria, Czech Republic, Germany, Netherlands, Switzerland). The greatest diversity of Lactuca species was found in France, where also the most seed samples (165) were collected. The most characteristic habitats with a high density of Lactuca spp. populations were observed along roads and highways, grassy ditches, ruderal communities, and dust-heaps. Natural infections by powdery mildew (Erysiphe cichoracearum) and downy mildew (Bremia lactucae) on some wild Lactuca spp. were observed. Recent observations concerning the geographic distribution, population structure, habitats, and natural occurrence of diseases of Lactuca spp. are discussed. This assemblage of genetic resources of Lactuca spp. can serve as the basis of future studies of species diversification, spatial population structure, plant microevolution, domestication processes, and genetic variability of host-parasite interactions.     

Increase in auxiliary photoprotective photosynthetic pigments in wheat seedlings induced by Azospirillum brasilense

Inoculation of wheat seedlings with the plant growth-promoting bacterium Azospirillum brasilense Cd was immobilized in alginate microbeads and, without applying any stress, significantly increased the quantity of several photosynthetic pigments, such as chlorophyll a, chlorophyll b, and the auxiliary photoprotective pigments violaxanthin, zeaxanthin, antheroxanthin, lutein, neoxanthin, and β-carotene. This resulted in greener plants with no apparent visible stress. After monitoring the quantity of photosynthetic pigments for 4 weeks, we observed that inoculated plants had higher quantities of pigments in shoot and stem. The greatest difference in the quantity of all pigments between inoculated and noninoculated plants occurred in the first week of growth. Regardless of treatment, the quantity of pigments in stems was three to four times less than the quantity of these pigments in shoots. Application of Azospirillum, either as liquid inoculant or as alginate microbeads, did not alter the positive effect of the bacteria on pigment production or the positive response of the plants towards A. brasilense Cd inoculation.     

Responses of native legume desert trees used for reforestation in the Sonoran Desert to plant growth-promoting microorganisms in screen house

Three slow-growing legume trees used for desert reforestation and urban gardening in the Sonoran Desert of Northwestern Mexico and the Southwestern USA were evaluated whether their growth can be promoted by inoculation with plant growth-promoting bacteria (Azospirillum brasilense and Bacillus pumilus), unidentified arbuscular mycorrhizal (AM) fungi (mainly Glomus sp.), and supplementation with common compost under regular screenhouse cultivation common to these trees in nurseries. Mesquite amargo (Prosopis articulata) and yellow palo verde (Parkinsonia microphylla) had different positive responses to several of the parameters tested while blue palo verde (Parkinsonia florida) did not respond. Survival of all tree species was over 80% and survival of mesquite was almost 100% after 10 months of cultivation. Inoculation with growth-promoting microorganisms induced significant effects on the leaf gas exchange of these trees, measured as transpiration and diffusive resistance, when these trees were cultivated without water restrictions.