不同草带对坡耕地土壤侵蚀的影响

于20012002年进行了“不同草带对坡耕地土壤侵蚀的影响”研究,试验设高羊茅(A)单作、高羊茅与红三叶混作(B)、非洲狗尾草与红三叶混作(C)和一个无草带种植(对照D)4个处理,坡地在13.2°14°。在每个处理上部等高种植玉米,基部种0.5 m宽的草带,底部设径流收集池,主要收集510月玉米生长期间的水土流失量。结果表明:①草带可显著减少径流量和侵蚀量,3种草带处理2年的总径流量和总侵蚀量均极显著(P<0.01)小于对照D,其中非洲狗尾草与红三叶混作的水土保持效果最好,高羊茅与红三叶混作次之,高羊茅单作为第三。②试验地水土流失主要发生在68三个月,这3个月的径流量和侵蚀量分别占总量的96.8%,99.9%,特别是6月径流量和侵蚀量分别占总量的63.2%,80.3%,草带在此期间水土保持效果最显著。所以,在坡耕地上结合农作物等高种植多年生草带是一项简单有效的水土保持技术。     

非洲狗尾草防治坡耕地水土流失效应的研究

为定量研究优良牧草纳罗克非洲狗尾草带的水土保持效应,于2001~2002年在云南昆明进行了研究。试验设纳罗克非洲狗尾草草带(A)、迈洛克高羊茅草带(B)和无草带种植(C)三个处理,坡度在13.2~14°之间;每个处理上部等高种植9 m×2 m玉米,基部种植0.5 m宽的草带,底部设径流收集池。结果表明,三个处理的水土流失量为C>B>A,与对照C相比,处理A的年均径流量、侵蚀量分别减少75.9%、96.4%,处理B分别减少59.2%、88.2%;与B处理相比,处理A减少了40.9%、69.2%,说明结合农作物种植纳罗克非洲狗尾草草带,是一种很好的防治水土流失方法,在云南及南方地区的坡耕地上有着广泛的应用前景。     

坡耕地间作作物群体水土保持耕作措施

为解决云南山区坡耕地作物生态系统中存在的作物栽培技术措施不配套,水土等自然资源不能有效利用与保护的问题,对不同作物搭配间作方式水土保持效应进行了研究,为坡耕地水土流失治理提供了合理可行的保护性作物种植措施。试验选用玉米、辣椒和混播草带搭配成不同间作方式:玉米间作辣椒(行比为2∶2,2∶4,2∶6)、玉米间作草带、辣椒间作草带,研究不同间作群体对坡耕地水土流失的影响。结果表明:作物间作群体总水土流失量均低于作物单作,玉米间作草带总径流量最多比玉米单作减少97.52%,总侵蚀量最多比辣椒单作减少99.49%;玉米间作辣椒群体中,行比为2∶2,2∶4的水土保持效果好于2∶6处理。随着降雨强度增加,间作处理的水土保持效果更明显,玉米间作草带和辣椒间作草带的径流量和侵蚀量均显著小于辣椒单作及玉米单作(p0.05),在高强度降雨下,玉米间作草带径流量最多比玉米单作减少98.25%,侵蚀量最多减少99.96%。玉米间作辣椒、玉米间作草带和辣椒间作草带均能有效减轻坡耕地水土流失,在高强度降雨下,该间作模式的水土保持效果更明显,有利于山区坡耕地水土资源的持续利用与保护。     

水分调控与种植模式对人工草地土壤水分及产量品质的影响

针对河西走廊地区水资源短缺、天然草地退化严重和质量低下等问题,探究合理的水分调控与种植模式,以缓解草畜矛盾,改善生态环境,实现区域草地畜牧业可持续发展。试验采用2年大田试验,研究3种种植模式(O:红豆草单播;A:红豆草+无芒雀麦混播;B:红豆草+无芒雀麦+长穗偃麦草混播)与4种水分调控[灌水上下限以土壤含水量占田间持水量θ_FC的百分比计,W0:充分灌水(75%~85%θ_FC);W1:轻度水分亏缺(65%~75%θ_FC);W2:中度水分亏缺(55%~65%θ_FC);W3:重度水分亏缺(45%~55%θ_FC)]对人工草地土壤水分特征、干草产量、品质及水分利用效率的影响。结果表明:(1)在时间维度(4—9月)0—40 cm土层土壤含水量表现为先减小后增大的变化趋势,且该变化趋势W2、W3较W0、W1明显,单播较混播明显,40—100 cm土层土壤含水量呈现逐渐减小的变化规律;在空间垂直分布上,各处理土壤含水量呈先增大后减小之后趋于稳定的变化趋势;3种种植模式中土壤含水量均属于中等变异,且表层与60—100 cm土层变异系数较大。(2)随着水分亏缺加剧,单混播牧草产量均逐渐减小,WUE先增大后减小,W1较W0处理牧草产量差异不显著(p＞0.05),且WUE最高;A和B种植模式2年平均总产量分别较O提高16.01%和12.74%,2年平均WUE分别较O提升18.64%和11.19%。(3)适宜水分亏缺提升了牧草品质,混播模式较单播牧草品质改善。A和B种植模式较O种植模式2年平均ADF分别降低4.40%和2.73%,NDF分别降低2.82%和2.02%,CP分别降低3.53%和7.24%,但W0与W1水分处理,O与A种植模式CP差异不显著。A和B种植模式较O种植模式2年平均Ash分别提升18.50%和16.58%,EE分别提升23.19%和20.37%,RFV分别提升4.87%和3.20%。通过主成分分析综合评价得出,轻度水分亏缺下红豆草与无芒雀麦混播是河西走廊地区人工草地高产优质高效的适宜水分调控与种植模式。     

混播草带控制水源区坡地土壤氮、磷流失效应

坡地土壤氮、磷流失是湖库型饮用水源区污染的主要来源。本文以云南最大的城市集中式饮用水源地为研究区域,在昆明云龙水库库区周边的坡耕地红壤上开展了混播草带防治土壤氮、磷流失效应的研究。研究结果表明:选择适宜草种进行混播,所形成的草带控制水土及氮、磷流失效果优于自然植被;对地表径流量、土壤侵蚀量的控制效果均为:混播黑麦草+紫花苜蓿>混播黑麦草+白三叶>自然植被>无草带种植;草带对土壤侵蚀量的控制效果要好于地表径流量。其中处理混播黑麦草+紫花苜蓿、混播黑麦草+白三叶径流量分别比无草带种植降低35.19%、46.26%;侵蚀量比无草带种植降低73.51%、78.13%;坡耕地地表径流中氮素流失形态主要以泥沙中氮流失为主,占到80%～85%左右,磷素流失以颗粒态磷流失为主,占到90%～95%左右;对地表径流中的氮、磷流失量控制效果均为:混播黑麦草+紫花苜蓿>混播黑麦草+白三叶>自然植被>无草带种植,对总氮流失量的控制效果要好于总磷流失量;混播黑麦草+白三叶处理中径流中总氮、总磷流失量分别降低59.96%、48.57%;混播黑麦草+紫花苜蓿处理径流中总氮、总磷流失量分别降低63.31%、56.91%;自然植被处理中径流总氮、总磷流失量分别降低29.46%、26.03%。     

2种草本植物混播根系对土体抗剪强度的影响

为研究混播草本植物根系对土体抗剪强度的影响,选择合理的播种方式,强化草本植物固土效应,为生态环境建设提供科学依据,采用无侧限抗压强度试验,测算素土、单播紫花苜蓿(Medicago sativa)、单播非洲狗尾草(Se-tariaanceps stapf ex massey)、混播紫花苜蓿+非洲狗尾草(1∶1)根土复合体...     

坡耕地甜玉米地膜覆盖间作模式水土保持效应

针对云南省山地种植措施不合理,水土资源流失严重的现状,进行了甜玉米间作草带和辣椒的水土保持效应研究。结果表明,在降雨集中的6,7,8这3个月,间作处理的径流量比单作处理的径流量平均减少了29.08%,侵蚀量平均减少了52.36%。B处理(甜玉米盖膜+牧草)的总径流量比D处理(辣椒单作)减少了85.05%,B处理的总侵蚀量比C(甜玉米盖膜单作),D处理分别减少了62.58%,63.34%。在极高雨强下,B处理的径流量比D处理减少了75.29%,B处理的侵蚀量比C,D处理的分别减少了81.36%,98.34%。可见,甜玉米间作牧草草带是一种持续利用和保护山地水土资源的有效措施。     

无芒雀麦与苜蓿混播草地生产力提升的水氮调控模式

针对西北干旱草原区天然草地退化、水土流失严重以及人工草地生产力低下等问题,研究种植模式和水氮调控对牧草产量、品质和水氮利用效率的影响,以期获得高产高效的草地管理模式。以3年生紫花苜蓿和无芒雀麦(2018年播种)为试验材料,分析种植模式(无芒雀麦与苜蓿混播D1,无芒雀麦单播D2)、施氮(纯氮)量(N1:60 kg/hm²;N2:120 kg/hm²)和灌水量(以灌水下限占田间持水量θ_f的百分比计,轻度亏水 65%θ_f、中度亏水 55%θ_f、重度亏水 45%θ_f分别记为W1、W2、W3,灌水上限均为85%θ_f)3个因素对牧草产量、品质和水氮利用效率的影响。结果表明:(1)增加灌水量和施氮量有利于牧草株高和茎粗的生长,与W3N1处理相比,W1N2处理混播苜蓿、混播无芒雀麦和单播无芒雀麦三茬平均株高分别增加27.41%,20.26%和26.55%,茎粗分别增加11.32%,4.11%和20.98%;混播对无芒雀麦株高有促进作用,对茎粗有抑制作用。(2)灌水量和施氮量的增加有利于提高牧草产量和品质,W1N2处理牧草年产量和粗蛋白(CP)含量最高,与W3N1处理相比,W1N2处理下混播牧草年产量、CP含量分别增加42.16%,27.00%,单播牧草年产量、CP含量分别增加38.59%,37.26%,混播牧草ADF和NDF分别降低19.56%和33.86%,单播牧草ADF和NDF分别降低21.29%和25.53%。(3)随着灌水量的增加,IWUE和WUE减小,PFP_N增大;增加施氮量,混播模式IWUE、WUE和PFP_N均减小,单播模式IWUE和PFP_N减少,WUE增大。(4)基于主成分分析得出,混播模式轻度亏水(灌水下限65%θ_f)高氮量(120 kg/hm²)处理综合得分最高,为适宜的水氮管理模式。研究结果可为西北干旱半干旱草原区牧草的种植管理提供理论依据。     

水源保护区坡耕地不同种植模式水土保持效应试验

在水源保护区16．5°的坡耕地上,通过3种种植模式（玉米＋小麦、牧草混播、黄梨＋绿肥）进行连续3年水土保持试验,研究水源保护区坡耕地水土保持效应。结果表明：1）与玉米＋小麦习惯轮作模式相比,牧草混播及黄梨＋绿肥种植模式降低径流量、土壤流失量、养分流失量分别为27．7％、44．2％、38．0％及14．4％、20．9％、27．9％,牧草混播及黄梨＋绿肥2种种植模式都能有效地降低水土及养分流失,并且效果随着年限延长而增加;2）在肥料施用量比玉米＋小麦种植模式减少34．0％的条件下,牧草混播种植模式的纯收益仍能与玉米＋小麦轮作模式持平;黄梨＋绿肥种植模式纯收益比玉米＋小麦种植模式提高5．9％,梨树盛果期以后,产值还有很大提升空间;3）从水土保持角度看,牧草混播种植模式的效果最好,从经济角度分析,黄梨＋绿肥种植模式效益最高,二者都可作为水源保护区种植结构调整及坡耕地综合治理的较好模式。     

堆肥施用和牧草种植对煤矿复垦地土壤肥力的影响

为改善采煤沉陷复垦区表层土壤养分贫瘠、控制水土流失,2013年5月在新庄孜煤矿沉陷区复垦地施用四种堆肥(堆肥1、堆肥2、堆肥3、堆肥4)后,进行紫花苜蓿(Medicago sativa)单播,墨西哥玉米(Purus frumentum)单播和两种牧草混播种植试验,并在当年牧草生长季结束后(2013年11月)对改良地表土进行理化性质分析,并用主成分分析的方法进行土壤质量评价。结果表明:施加堆肥各处理均能有效增加土壤有机质、全氮、速效磷含量,分别比对照增加了26%~45%、6%~14%、138%~359%,施加堆肥再单播紫花苜蓿使土壤含水量和硝态氮含量分别增加了24%~37%和210%~338%;堆肥改良后种植墨西哥玉米,复垦区表层土壤全磷含量增加了18%~20%;堆肥改良后混播紫花苜蓿和墨西哥玉米使复垦区表层土壤的含水量和铵态氮含量分别增加了36%~54%、50%~105%。在各处理中,施用堆肥4加紫花苜蓿和墨西哥玉米混播处理对复垦地表层土壤改良效果最好。     

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.