干湿交替条件下稻田土壤氧气和水分变化规律研究

在水稻高产栽培技术中,为合理利用水资源,改良土壤通气性,干湿交替灌溉技术已广泛应用。干湿交替灌溉技术的核心是协调土壤水分与氧气之间的平衡。本研究采用大田试验,在水稻生育后期进行干湿交替处理,同步监测稻田5 cm土层土壤氧气、水分及温度的变化,以探讨稻田土壤氧气和水分运移变化规律及其互作关系,为进一步揭示干湿交替灌溉技术的内在生理机制奠定基础。研究结果表明,干湿交替条件下,稻田土壤含水量处于饱和状态时,基本监测不到土壤含氧量;而稻田土壤在慢慢变干的过程中,5 cm土层土壤体积水分含量逐渐降低,土壤氧气含量逐渐升高。在花后19 d、24 d、29 d,当5 cm土层土壤体积含水量分别下降为25.4%、25.1%、24.7%时,土壤含氧量则分别上升到17.5%、17.4%、17.4%。在水稻生育后期不同阶段,土壤氧气含量的日变化呈现先降低再升高的趋势,谷值一般出现在14:00—15:00之间;土壤含水量随时间呈波动式逐渐降低的变化趋势;土壤温度呈现先升高后降低的趋势,峰值一般出现在15:00—16:00之间。从上午8:00到下午17:59,当土壤温度升至峰值时,土壤水分含量较低,而土壤含氧量开始升高。水稻开花期、灌浆期和成熟期的土壤氧气含量与土壤含水量均表现出极显著负相关关系,土壤温度与土壤水分间呈显著负相关关系,而土壤氧气与土壤温度之间无显著相关关系。说明干湿交替条件下,水稻生育后期稻田土壤中的水分和氧气含量存在一定的此消彼长的关系。因此,通过适度的干湿交替管理措施,可在一定程度上调节水稻根系周围的土壤水分和氧气的平衡。     

三江平原典型小叶章显地土壤中铵态氮水平运移规律研究

选择三江平原小叶章湿地不同水分带上的两种土壤类型（草甸沼泽土和腐殖质沼泽土）作为研究对象，以NH4Cl为示踪剂，模拟研究了铵态氮在土壤中的水平运移过程。结果表明，两种土壤各土层的铵态氮浓度和水平运移速率均与运移距离呈显著负相关（P〈0．01），并随运移距离的增加呈一阶指数衰减曲线变化。各土层的铵态氮水平运移主要由其对于铵态氮吸附的饱和程度来决定，而运移速率主要受浓度梯度、水势梯度及土壤基质势的控制；两种土壤各土层的铵态氮水平运移速率与土壤含水量大多呈显著正相关（P〈0．05），并随含水量的增加而呈指数增长曲线变化；两种土壤各土层的铵态氮浓度均受土壤水分扩散率的影响，二者大多呈显著正相关（P〈0．05），除草甸沼泽土0～20cm土层的铵态氮浓度随水分扩散率的升高呈Boltzmann曲线变化外，其它土层及腐殖质沼泽土的各土层均随其升高呈指数增长曲线变化；草甸沼泽土要比腐殖质沼泽土的相应土层更有利于铵态氮的水平运移，二者不同土层物理性质的显著差异是导致其铵态氮浓度、水平运移速率随运移距离、土壤含水量及水分扩散率的变化而发生分异的重要原因，而湿地水文条件可能对于二者物理性质的塑造作用有着重要影响。     

冻融对河北省深州市盐碱地土壤理化性质的影响

随着全球气候变暖,冻融对土壤性质的影响日益受到重视。以河北省深州市盐碱土为研究对象,通过分析土壤含水率、全持水量、容重、饱和导水率、电导率、pH和有机质的变化,探讨冻融对0—20cm深度盐碱地土壤理化性质的影响。结果表明:0—20cm土层深度,冻融增加土壤的含水率,而对全持水量的影响较小;0—10cm土层深度,冻融增加了土壤容重与pH,降低了土壤的电导率和渗透性,该层土壤水盐运移呈特殊规律,土壤含水率与电导率呈相反变化趋势;对于10—20cm土层深度,冻融增加了土壤的渗透性和有机质的含量。在相关性分析中,0—20cm土层深度土壤容重与全持水量呈极显著负相关(P0.01),与含水率呈显著负相关(P0.05),其有机质含量和导水率与其他性质无显著相关;0—10cm土层深度土壤pH与容重和含水率呈极显著相关,与全持水量呈显著相关;10—20cm土层深度土壤电导率与容重呈显著负相关,与全持水量呈显著正相关。研究结果为冻融对盐碱土影响的研究及盐碱土的改良提供科学依据。     

干湿交替对水稻土碳氮矿化的影响

通过室内培育试验,研究干湿交替条件下长期不同施肥处理水稻土微生物生物量和理化性状变化对土壤C、N矿化的影响机制.结果表明,与连续淹水(Cw)处理相比,干燥处理不仅显著地提高了所有施肥处理土壤有机C的矿化速率,其幅度为78%～204%,而且也提高了各处理土壤微生物生物量C和N,其幅度分别为55%～77%和57%～72%;干燥后淹水处理土壤有机C矿化速率的提高幅度为74%～95%,呈先降低再升高的趋势.土壤N的矿化在干湿交替过程的干燥处理中降低34%～78%:干燥后淹水过程仅使NPK处理的升高21%,而CK和NPKOM处理分别降低5%和13%.在培养过程中土壤Eh值仅在-60～60 mV范围时,与土壤微生物生物量C之间有显著的负相关关系.在干湿交替的干燥过程,随土壤pH值的升高土壤微生物生物量C有增加的趋势,在淹水条件下土壤pH值则仅与NPKOM处理土壤微生物生物量C之间有明显的负相关关系.干湿交替条件下土壤 pH和 Eh 值、微生物群落组成和数量与有机质的矿化之间的相互作用关系复杂,三者间的作用机理需进一步研究.     

宁夏引黄灌区干湿交替过程中土壤pH的动态变化及影响因素

地处干旱半干旱区的黄灌区干湿交替过程中引起土壤环境因素的周期性变化,从而影响农田生态系统关键过程。通过连续测定黄河上游宁夏引黄灌区稻田在灌溉淹水和落干过程中的土壤pH,研究在水稻生育期内表层土壤pH在高频次灌溉排水干湿交替过程中的变化规律。结果表明:在灌水之后淹水过程中,表层土壤pH升高;相反在淹水之后落干过程中表层土壤pH降低;但在最后一次灌水之后,经过长时间的落干烤田过程,土壤pH随表层土壤表层盐分积累过程逐渐升高。土壤电导率(EC)与土壤pH在灌溉淹水和落干过程中具有相同的变化趋势,具有显著正相关性(p0.05),土壤氧化还原电位(Eh)与pH呈极显著负线性相关(p0.01),而灌溉量、施肥量、降水、地表5 cm土壤温度对表层土壤pH的影响均不显著。     

冻融作用对棕壤水溶性盐和土壤氧化物的影响

为了解沈阳棕壤水溶性盐和土壤氧化物在冻融条件下的变化规律,采用冻融模拟试验研究了冻融作用对棕壤水溶性盐和土壤氧化物的影响。结果表明,(1)冻融作用促进了土壤K+、Na+、Ca2+、Mg2+的释放,有机质和黏粒含量是影响其释放的重要因素。(2)冻融作用促使土壤中CO2含量增加,促进了HCO3-的形成。虽然SO42-、Cl-性质稳定,但冻融作用中水分和温度的变化,致使SO42-、Cl-随着冻融次数的增加呈先增加后稳定的趋势。(3)冻融作用促进土壤铁结晶老化形成氧化铁,且氧化铁含量随土壤深度增加逐渐增加;氧化锰主要受冻融条件下土壤pH影响,pH上升氧化锰含量增加。(4)土壤氧化硅和氧化铝受pH影响,pH降低其含量增加,pH增加其含量降低。此外,有机质含量较多的土层不易形成硅铝氧化物,土壤铁锰氧化物的增加不利于土壤硅铝氧化物的形成。     

交替冻融对松花江流域典型土壤可溶性有机碳的影响

以受季节性冻融过程影响显著的黑土、暗棕壤和水稻土为例,采用实验室模拟的方法,研究交替冻融循环过程(分别在-20℃和20℃下处理)对土壤可溶性有机碳(DOC)的影响。研究表明,初次交替冻融后暗棕壤和水稻土DOC升高,黑土DOC仅降低1.3%。随着冻融次数增加,黑土和暗棕壤DOC含量逐渐下降,并趋于稳定,水稻土DOC呈交替上升趋势。15次交替冻融后,黑土DOC含量下降21%,水稻土DOC含量上升9%,暗棕壤DOC含量未出现明显变化。三维荧光分析结果验证了土壤DOC的变化趋势,15次交替冻融后,黑土可溶性有机物结构变复杂,分子量增加;水稻土可溶性有机物结构变简单,分子量变小;暗棕壤产生的新物质,一部分使可溶性有机物结构变复杂,分子量变大,另一部分使有机物分子量变小。     

土壤微生物体氮的季节性变化及其与土壤水分和温度的关系

以杨陵土垫旱耕人为土(中等肥力红油土)为供试土壤进行田间试验和室内培养试验,研究土壤微生物体氮的动态变化及其土壤含水量和温度的关系。结果表明,田间土壤微生物体氮的变化有明显的季节性;夏季最高,冬季最低,其它时期居中;且与土壤温度有显著或极显著的正相关性,相关系数在0.855以上;试验期间土壤水分含量在10%以上,基本能满足微生物活动所需,因而微生物体氮的变化与水分关系并不密切。应用培养试验结果进一步证明了田间试验结果,即在4～36℃范围内,微生物体氮与温度呈线性相关,而在土壤含水量为6.75%～23.23%范围内,与水分呈指数相关关系,当土壤水分小于10.87%时,水分对微生物体氮有突出结果,当超过10.87%后,几乎没有影响。频繁的干湿交替会使微生物体氮显著减少,但冻融交替却无明显影响。     

大兴安岭典型针阔混交林区土壤持水效应

受地貌条件的影响,大兴安岭低山丘陵地区土壤的水、热性质出现分异,发育的土壤类型以及植被都表现出典型的高寒森林湿地中域景观特征。沿局部分水岭向河谷低漫滩发育4种土壤类型,依次为塔头苔草草甸土—灰色森林土—白浆土—暗棕壤。大兴安岭地区森林湿地存在明显的冻融过程,冻融作用的影响下森林湿地表层的水分数量和状态都发生明显的变化。在冻融过程中,位于地势较高的森林植被湿地仅表层储存大量水分,而位于低位的塔头苔草湿地整体土体的水分数量和状态都发生明显的变化。白浆土的水分特征曲线非常平缓,表明土壤水分变化微弱。大兴安岭地区山岭和山麓发育的土壤土层较薄,使得除了枯落物(O)层外其他土层土壤持水性能都弱,一旦该地区枯枝落叶层受到破坏,整个山岭表层的土壤将发生严重的水土流失。     

冻融侵蚀机理

在温带地区 ,土壤流失量的 5 0 %以上发生在冻土层解冻时期。这是由于土壤表层水分含量过多所致 ,而土壤中存在一不透水的心土层则是导致土壤表层水分含量高的主要原因。研究具有不透水层土壤的侵蚀机理 :1)冻融交替对于土壤粘聚力的影响。 2 )降水条件下 ,不透水层对土壤分散力的影响。从绘制的摩尔图可以看出每种处理下土壤的粘聚力。在冻融交替进行初期 ,土壤含水量分别为 15 %和 2 5 %。首先在 - 12℃冷冻处理 90min ,解冻 30min ,然后立即测定土壤的抗剪强度和分散力。小于 5 0kg/m2 的土壤粘聚力不受非冷冻处理或冷冻处理时水分含量的影响。降雨对于具有不透水层土壤的分散力影响很大。据研究在一滴水作用下 ,具有不透水层的黄土与不具有不透水心土层的黄土相比土壤分散力从 0 0 16± 0 0 0 6 5g升高到 0 0 5 4± 0 0 2 6 5g ;而具有不透水性层的冰碛土与不具有不透水心土层的冰碛土相比土壤分散力从 0 0 36± 0 0 0 71g升高到 0 145± 0 0 6 35g;具有不透水层的土壤基质势趋近于 0Pa ,因此造成土壤粘聚力减小 ,土壤分散力变大 ,从而引起强烈的土壤侵蚀。     

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.