间作对土壤团聚体有机碳储量的影响及其氮调控效应

基于5年的田间小区定位试验,采用干筛法对不同施氮水平下的玉米单作、马铃薯单作和玉米马铃薯间作土壤进行团聚体分级并测定各粒级团聚体有机碳含量,研究间作对土壤团聚体有机碳储量的影响及其氮调控效应。结果表明:92%以上的土壤有机碳储藏在土壤大颗粒团聚体(2 mm)和小颗粒团聚体(2～0.25 mm)中。间作提高了土壤大颗粒团聚体(2 mm)和小颗粒团聚体(2～0.25 mm)的比例,但对不同粒级团聚体有机碳含量的影响与施氮量相关。对比2种单作,间作在低氮(N1)和常规施氮(N2)下增加了土壤总有机碳储量,在不施氮(N0)和高氮(N3)下无显著影响或降低有机碳储量。其中,间作通过增加土壤大颗粒团聚体(2 mm)的比例及其有机碳含量,在低氮(N1)时产生最强的间作固碳优势,土壤总有机碳储量分别较玉米单作和马铃薯单作提高24.8%和5.7%。因此,适量施用氮肥可以充分发挥间作效应,有效提高土壤有机碳储量。     

稻田绿肥轮作提高土壤养分增加有机碳库

综合评价中国南方不同稻田绿肥轮作模式,筛选与优化绿色高效的稻田多熟种植系统,有利于南方双季稻区农业可持续发展。通过田间试验,研究不同绿肥轮作模式(A冬闲-稻-稻→冬闲-稻-稻(对照)、B紫云英-稻-稻→油菜/花生-稻、C油菜/花生-稻→马铃薯/玉米+大豆-稻、D马铃薯/玉米+大豆-稻→蔬菜/花生+玉米-稻、E蔬菜/花生+玉米-稻→紫云英-稻-稻)对土壤养分中pH值、有机质、全氮、碱解氮、有效磷和速效钾及总有机碳库、活性有机碳、碳库管理指数的影响。结果表明:绿肥轮作各处理的土壤有机质、碱解氮和速效钾均显著高于对照处理(P0.05),增加幅度分别为8.73%~15.59%、11.79%~19.64%和5.80%~37.19%。绿肥轮作处理B、C的总有机碳质量分数与对照相比有显著(P0.05)增加,分别增加了15.59%、11.19%。与对照相比,绿肥轮作B、C、D、E均可以显著(P0.05)提升土壤活性有机碳质量分数,提高幅度分别为29.03%、19.96%、16.67%和21.75%。与冬闲对照处理相比,绿肥轮作系统中处理B的土壤碳库指数显著(P0.05)增加了15.70%。相比冬闲对照处理,绿肥轮作处理B、C、D、E的土壤碳库管理指数分别显著(P0.05)增加了32.07、21.32、17.91和23.74,其中紫云英-稻-稻→油菜/花生-稻种植模式达到最大。土壤有机质与全氮、有效磷、总有机碳、活性有机碳、碳库管理指数存在极显著(P0.01)的相关性,土壤全氮、碱解氮、有效磷均与碳库管理指数存在显著的相关性(P0.05)。此外,总有机碳与活性有机碳和碳库管理指数存在极显著的相关性(P0.01)。可见在当地土壤肥力条件下,绿肥轮作尤其是紫云英-稻-稻-油菜/花生-稻能提高土壤有机碳质量分数和土壤碳库管理指数,有利于改善土壤质量,提高土壤肥力,为建立农田可持续的土壤管理和土地利用提供科学依据和参考价值。     

红壤侵蚀区崩岗土壤养分化学计量特征分异规律

以福建省西南部长汀县濯田镇黄泥坑崩岗群内植被盖度分别为2%,20%和95%的3处相邻崩岗为研究对象,对各崩岗内集水坡面、崩壁(顶部、中部及底部)、崩积体(上部和下部)和沟道出口7个典型部位0—10,10—20,20—30cm土壤基本理化性质进行测定,分析了各植被盖度崩岗不同深度及部位土壤化学计量比的空间分异规律。结果表明:随着植被盖度的升高,土壤养分含量及化学计量比显著增加(除全磷含量和P/K以外);随着土壤深度的增加,有机碳、全氮和全钾含量以及C/N、C/P、C/K和N/P总体上呈减少趋势,全磷含量以及N/K和P/K基本维持稳定;沿集水坡面→崩壁→崩积体→沟道出口,有机碳、全氮和全钾含量以及C/N、C/P、C/K、N/P和N/K基本表现为先减少再增加最后亦降低的变化趋势,全磷含量和N/P无明显差异;土壤化学计量特征与土壤养分含量、粉粒含量、容重、含水量和pH具有较强的相关关系。崩岗系统土壤物理结构较差,养分含量普遍较低,其中有机碳、全氮和全磷含量存在不同程度的限制。     

无机氮和葡萄糖添加对土壤微生物生物量和活性的影响

以黄淮海平原潮土为研究对象,通过室内恒温恒湿培养方法,比较研究了土壤中纤维素是否存在时,外源无机氮和葡萄糖添加对土壤微生物生物量及其活性的影响变化。实验设8个处理,包括不加任何物质的对照(CK)、添加无机氮(N)、葡萄糖(G)、纤维素(C)处理及葡萄糖和无机氮同时添加(G+N)处理,以及在纤维素存在基础上添加无机氮(C+N)、葡萄糖(C+G)、葡萄糖和无机氮同时添加(C+G+N)处理。在33天培养时间内,分别在不同的时间间隔内测定了土壤CO2累积释放量、微生物生物量碳(Cmic)、及脱氢酶(DHD)、β-葡萄糖苷酶(GLU)、过氧化氢酶(CAT)、碱性磷酸酶(APH)活性。结果表明,所有测定的微生物性质在CK与C处理间均没有显著性差异。与CK和C处理相比,其他所有处理的土壤CO2累积释放量均显著增加,其中C+G+N处理达最大值;G、G+N、C+G、C+G+N处理的土壤Cmic含量及DHD和APH活性显著提升,尤其在培养的前14天,而N和C+N处理则与CK处理相似,表示添加葡萄糖可显著增加上述处理生物活性水平,而添加无机氮则不能。添加无机氮和葡萄糖对GLU和CAT的影响不明显,大部分情况下它们在处理间没有表现出显著性差异。相关性分析表明,CO2释放速率始终与APH活性成显著正相关,但与Cmic和其他酶活性之间的相关关系则随着培养时间的不同而发生变化,这可能与不同培养时间的微生物组成或微生物利用底物的模式发生改变有关。聚类分析结果进一步表明,8个处理的土壤微生物活性水平可明显分成3组,其中活性水平最高的组只包含C+G+N处理,该结果提示在难分解纤维素存在时,无机氮和易利用有机碳的同时添加对提升土壤微生物活性的重要性。     

玉米间作大豆、萝卜对红壤不同粒径水稳性团聚体碳氮分布的影响

为了探讨不同种植模式对红壤水稳性团聚体粒径分布以及不同粒级团聚体中有机碳、氮含量,土壤微生物量碳、氮含量的影响,选择大豆、萝卜与玉米间作及3种作物的单作进行田间试验,在作物成熟期采样,进行样品测定。结果表明:在玉米-大豆(玉//豆)、玉米-萝卜(玉//萝)、玉米单作(玉单)、大豆单作(豆单)、萝卜单作(萝单)处理中,大团聚体(> 0.25 mm)的百分含量明显高于微团聚体(<0.25 mm),其中以大团聚体中粒径为0.25~2 mm的百分含量最高且显著高于其余两种粒径,大团聚体百分含量表现为:玉//豆>玉//萝>玉单>萝单>豆单,微团聚体则与其相反。团聚体粒径中的有机碳含量表现为0.25~2 mm粒径最高、<0.25 mm粒径次之、>2 mm粒径含量最少、玉米大豆间作含量最高、玉米单作含量最低。团聚体粒级中全氮含量与有机碳分布一致,但单作的全氮含量高于间作。有机碳与全氮的C/N为间作高于单作,>2 mm粒径C/N高于其余两种粒径。微生物量碳、氮在团聚体粒径中的分布趋势一致,都表现为间作模式高于单作模式,大团聚体中的含量高于微团聚体。微生物量碳、氮的C/N为单作模式高于间作模式,微团聚体大于大团聚体。与单作相比,间作能提高土壤中水稳性大团聚体的含量,增加大团聚体粒径内的有机碳、氮及微生物量碳、氮的含量。     

稻秆炭还田对红壤双季稻田土壤碳氮磷钾生态化学计量学特征及其综合肥力的影响

为探究稻秆炭对红壤双季稻田土壤碳氮磷钾生态化学计量学特征及其综合肥力的影响,本研究采用大田定位试验,设置不施氮肥和生物炭(CK)、单施稻秆生物炭(B)、100%氮肥(N₁₀₀)和100%氮肥+稻秆生物炭(N₁₀₀B)4个处理,分析不同处理稻田土壤碳、氮、磷、钾生态化学计量学特征及其综合肥力的变化情况。结果表明,与CK相比,B和N₁₀₀B处理土壤pH值分别提高0.05和0.13个单位。与N₁₀₀相比,N₁₀₀B处理不仅使土壤有机质、全氮、NO₃^-、NH₄⁺、微生物生物量碳和氮含量增加5.13%、3.47%、11.7%、14.91%、60.89%、30.75%,还使土壤C/N、C/P、C/K、N/P、N/K化学计量比提升1.88%、2.10%、2.84%、3.62%、5.41%,并提升土壤综合肥力指数(IFI)2.97%。综上,稻秆炭还田有利于改善双季稻田土壤碳氮磷钾生态化学计量学特征及其综合肥...     

不同恢复年限侵蚀红壤生态化学计量特征

为了解侵蚀红壤碳、氮、磷分配格局及化学计量特征,本文在长汀县侵蚀红壤区选取不同恢复年限(2、13、30、33年)、立地条件相近、样地情况基本一致的马尾松林作为研究对象,以未治理侵蚀地(CKl)和次生林(CK2)为对照,对其土壤总有机碳、全氮和全磷质量分数及其化学计量比的特征进行测定和分析.结果表明:1)随恢复年限的增加,土壤总有机碳和全氮质量分数呈线性增加,土壤全磷质量分数无显著变化,恢复2 ～33 a的马尾松林土壤总有机碳、全氮和全磷质量分数仍显著低于CK2土壤,表明土壤肥力的恢复是一个漫长的过程.2)土壤C∶N、C∶P、N∶P随恢复年限的增加呈上升趋势,恢复2～33 a的马尾松林土壤C∶N逐渐趋向CK2.3)土壤C∶N和C∶P与土壤总有机碳质量分数呈正显著相关,土壤N∶P与全氮质量分数呈显著正相关,土壤N∶P与全磷质量分数相关性不显著,表明侵蚀退化红壤恢复过程中,土壤化学计量比主要受土壤碳和氮质量分数的控制,暗示着侵蚀红壤现阶段的植被恢复对N素的响应比对P素的响应更敏感.     

景电灌区几种土地利用方式土壤有机碳和养分特征研究

对景电灌区土壤次生盐渍化的1年生枸杞地和多年生枸杞地、未盐渍化的小麦地和苜蓿地4种土地利用方式土壤有机碳和养分状况进行对比研究,结果表明:在0~60cm土层,小麦地土壤有机碳含量及其密度、全氮和速效磷含量均最高,苜蓿地均最低;土壤全氮与有机碳含量呈极显著正相关(r=0.791,P0.01);4种利用方式C/N比值均较低,多年生枸杞地C/N比值最高,1年生枸杞地最低;4种利用方式速效钾含量无显著差异;苜蓿地容重显著高于其他3种利用方式,这与其低的有机碳含量密切相关(r=0.420,P0.01)。与小麦地相比,1年生枸杞地土壤有机碳含量及其密度显著降低,全氮和速效磷含量有所降低;与1年生枸杞地相比,多年生枸杞地土壤有机碳含量及其密度有所增加,全氮含量显著降低,速效磷含量显著增加。这意味着该区耕地土壤发生次生盐渍化以后,土壤性状恶化;种植枸杞使次生盐渍化土壤性状有所改善。     

黄土高原不同年限刺槐土壤化学计量特征分析

通过对陕北黄土高原4种不同年限(10,15,25,40年)刺槐林地0—200cm土壤的采集与分析,研究不同刺槐种植时间对土壤营养元素及化学计量比的影响。在每个林龄的林地内设3个小区,每个小区采用随机采样法选取3个采样点分层采集土壤样品,进行土壤碳、氮、磷、钾测定,计算化学计量比。结果表明:(1)有机碳和全氮、全钾含量随刺槐年限增加呈基本增大的趋势,全磷随刺槐年限的增长变化不大;有机碳、全氮和全磷呈极显著的正相关关系;(2)在0—200cm土层,有机碳、全氮空间分布基本一致,随土层深度增加均呈先减少后趋于稳定的变化趋势;全磷在整个空间中的分布较为均匀,其空间变异性低于有机碳和全氮;全钾含量高于碳氮磷含量,且随土壤深度变化不大;(3)土壤C∶N比,C∶P比,N∶P比和C∶N∶P比均随刺槐年限的增长呈先降低后升高的趋势,都在15年处有最低值;(4)土壤C∶N比随土层深度在一定范围波动,C∶P和N∶P比均随土层深度的增加呈先减少后趋于稳定的变化趋势。     

烤烟连作对土壤生态化学计量特征的影响

为阐明烤烟连作对土壤生态化学计量学特征的影响,采用野外调查与室内分析相结合的方法,对四川泸州烟区正茬和连作1、3、5年土壤的有机碳(SOC)、全氮(TN)、全磷(TP)和全钾(TK)含量及其化学计量特征进行了研究。结果表明:与正茬相比,烤烟连作1年对土壤养分含量无显著影响;连作至第3年时,SOC含量明显下降,而TP和TK含量显著上升;连作至第5年时,SOC含量显著下降了9.89%,TN、TP和TK则分别增加了14.37%、68.84%和27.58%。土壤C/N、C/P、N/P和N/K随连作年限的增加而降低,年均下降4.06%、9.25%、6.51%和2.36%。土壤SOC对C/N、C/P、N/P、N/K贡献为正,而TN、TP、TK对C/N、C/P、N/P贡献为负,土壤养分及其化学计量比的相关性受到各养分的共同影响。总体来看,烤烟在连作3年时即可引起土壤磷钾累积及有机碳降低,使其生态化学计量比发生变化,从而可能影响土壤养分间的平衡供应。     

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.     

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.     

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.