基于APSIM模型的2015-2100年气候变化对中国玉米生产力影响

全球气候变化直接影响作物生产。玉米是中国种植面积最大的粮食作物，系统探究未来气候变化对其生产力的影响对保障玉米高产稳产和粮食安全具有重要意义。为探究未来气候变化对中国玉米生产力影响，该研究基于SSP1-2.6和SSP5-8.5 共2种气候情景（shared socioeconomic pathways，SSP）1981-2100年逐日气象资料以及中国气象局农业气象观测站玉米生育期数据和土壤数据，使用调参验证后的农业生产系统模拟模型（agricultural production systems simulator，APSIM-Maize）解析了气候变化对中国玉米主产区高产性和稳产性的影响。结果表明：1）未来气候情景下，中国玉米主产区生育期内气温和≥10 ℃有效积温总体呈增加趋势，SSP5-8.5气候情景下升温幅度高于SSP1-2.6气候情景；降水量年际波动大，变化趋势不显著；太阳总辐射呈先增加后减少趋势。2）若不采取适应措施，未来气候变化使玉米全生育期、营养生长期和生殖生长期总体呈缩短趋势，且SSP5-8.5情景下缩短幅度大于SSP1-2.6情景，2080 s缩短幅度大于2030 s和2050 s。3）无适应措施条件下，未来气候变化下研究区域玉米光温潜在产量和雨养潜在产量总体呈下降趋势，SSP5-8.5情景下较SSP1-2.6情景下减产效应更大，2个情景光温潜在产量减产率平均值分别为13.8%和11.9%，雨养潜在产量减产率平均值分别为17.5%和14.0%。玉米潜在产量的稳定性略有提高，但区域间存在差异。因此，未来气候变化使中国玉米生产力总体下降，稳定性略有提高。研究为未来玉米高产稳产和中国玉米种植区划提供理论依据。     

气候变化对河南省夏玉米主栽品种发育期的影响模拟

为模拟气候变化对夏玉米发育期影响,本文将河南省划分为4个夏玉米主栽区,分区进行主栽品种遗传参数调试验证,确定各区域品种平均遗传参数。将未来气候变化情景(A2和B2)下,2020s、2050s和2080s各时段的温度和降水增量加上基准值,模拟未来气候变化对河南省夏玉米发育期的影响。模型调参验证结果表明：各区域品种遗传参数存在一定差异,豫西地区当前种植品种播种-开花所需积温高于其它地区,而豫北和豫东当前种植品种开花-成熟所需积温高于其它地区;各区开花期调参和验证误差RMSE为2～4d,相对误差NRMSE均小于10%;各区域成熟期调参误差RMSE均小于4d,验证误差RMSE为3～7d,除豫西区外,各区域调参及验证期间的成熟期相对误差NRMSE均小于10%。表明CERES-Maize模型对河南省各区域夏玉米发育期模拟精度均较高。未来气候变化影响模拟结果表明：A2和B2情景下,夏玉米营养生长期平均缩短4.7d和3.1d,全生育期平均缩短12.9d和8.6d。夏玉米生育期缩短日数与各时段增温幅度趋势一致,全省4个区域中豫西区生育期日数缩短最多。     

基于IPCC SRES A1B 情景下的福建省水稻生产模拟研究

选择福建省作为研究区域,根据地形特点划分了3个水稻种植区,选取17个样点及9个代表性品种,采用2006—2007年的逐日气象资料及同期区试产量资料对作物的遗传参数进行了调试;根据IPCC排放情景特别报告(SRES)中的A1B方案,利用区域气候模式PRECIS构建的气候变化情景文件与作物模型(CERES-Rice)耦合,采用雨养与灌溉两种方式,并综合考虑未来CO2浓度增加带来的直接增益效应,模拟了未来2020s及2040s气候变化对福建省水稻生产的影响。结果表明:无论是雨养方式还是灌溉方式,未来全省各稻区水稻生育期在两种情景下都将缩短,单季稻生育期天数减少幅度最大,2040s情景下达到20 d以上。未来双季稻种植区早稻与单季稻均表现为减产。2020s情景下闽东南稻区早稻减产率达到12.4%(雨养)和11.3%(灌溉);闽西北双季稻区早稻减产程度略小。单季稻区雨养水稻7.1%及灌溉水稻2.1%的减产主要来自中熟品种的负贡献。2040s减产幅度将进一步加大。与此相反,未来两种情景下双季稻区后季稻均表现为增产,但产量波动性较大。2020s情景下闽西北双季稻区灌溉后季稻产量增产达到21.0%,增产幅度大于闽东南地区的10.6%;雨养方式下后季稻增产幅度略小。2040s各稻区后季稻增产幅度将减小。未来水稻生长季的土壤水分条件将变得不如目前湿润,与之相关各稻区灌溉需要量均有所增加。总之,由于大气CO2肥效作用可在一定程度上提高未来气候变化下后季稻产量,全省水稻总产近期将有所增加,雨养与灌溉方式下分别增长0.4%及1.7%,但变化趋势是随着未来温度的增加总产将减少,负贡献主要来自于单季稻和早稻。     

基于DSSAT模型的宁夏马铃薯生产的适应对策

将DSSAT作物模型与PRECIS区域气候模式相嵌套,在25km×25km网格尺度上,模拟未来气候情景下宁夏马铃薯的生产.结果表明在B2排放情景下,假定作物品种和播期不变,考虑未来大气中CO2的肥效作用,在2020S和2050S,宁夏马铃薯的生育期可能缩短5%和3%,产量则可能增加11.3%和13.3%;如果品种不变、播期提前,马铃薯的生育期将延长,产量将会增加,但播期提前超过10d后,增产幅度将减小;如果改种温度敏感系数低的品种,马铃薯的生育期将延长、产量提高.因此,在宁夏地区,应采取播期提前或培育温度敏感系数低的马铃薯新品种以适应当地未来的气候变化.     

多模式集合模拟气候变化对玉米产量的影响

气候模式驱动作物模型是气候变化影响评估的主要手段。但是,单一气候模式输出和作物模型的结构差异使得研究结果存在不确定性。多模式集合的概率预估可以有效减少研究结果的不确定性。为此,本文利用1981—2009年东北地区海伦、长岭、本溪3地区农业气象站的历史气象资料和玉米作物数据,分别建立了作物统计模型并验证了APSIM机理模型在研究区域的适用性。在此基础上,与CMIP5在RCP4.5情景下的8个全球模式结合,尝试基于多模式集合评估了未来2010—2039年时段和2040—2069年时段气候变化对玉米产量的可能影响(相对于1976—2005年基准时段)。研究结果表明,APSIM模型对玉米生长发育和产量形成有很好的模拟能力。玉米生育期的模拟误差(RMSE)为3~4 d,产量的RMSE为0.6~0.8 t?hm~(-2)。建立的产量统计模型表明,玉米出苗阶段(5月中旬)的温度增加对产量增加有积极作用,而开花到成熟阶段(7月中旬到9月上旬)的温度和降水的增加、光照的不足均不利于产量增加。与1976—2005年基准时段相比,气候因素影响下2010—2039年玉米产量减少3.8%(海伦)~7.4%(本溪),减产的概率为64%(长岭)~73%(本溪);2040—2069年时段减产6.4%(海伦)~10.5%(本溪),减产的概率为74%(海伦)~83%(本溪)。未来2010—2039年时段和2040—2069年时段基于机理模型模拟的产量降低分别为6.6%(海伦)~8.9%(本溪)和9.7%(海伦)~13.7%(本溪),均高于相应时段基于统计模型得到的0.9%(海伦)~6.0%(本溪)和2.0%(长岭)~7.3%(本溪)减产结果。     

气候变化情景下我国水稻产量变化模拟

利用中国随机天气模型将IPCC最新推荐的气候模式HadCM2和ECHAM4与作物模式CERESRICE3．5相连接，模拟了未来4种气候情景下我国主要水稻产区产量的变化趋势。结果表明：（1）未来气候情景下，水稻产量大多表现为不同程度的减产趋势，其中早稻减产幅度最大；地区上以东北地区减产幅度最大。（2）若不取温室气体减排措施，2056年我国水稻产量较2030年减产程度更加明显；即使采取温室气体减排措施，水稻产量下降的趋势也没有大的改变；（3）高海拔地区在未来气候情景下表现出一定的增产趋势。     

未来气候变化对中国东北三省玉米需水量的影响预测

为了预测未来气候变化对中国东北三省玉米需水量的影响,该文在对中国东北三省近26 a来玉米生育期内参考作物蒸散量变化及玉米需水量分析的基础上,结合《排放情景特别报告》（Special Report on Emissions Scenarios, SRES）的两种排放情景A2（强调经济发展）和B2（强调可持续发展）预估的未来气候情景,研究探讨了未来气候情景下中国东北三省玉米需水量的变化趋势。结果表明,未来气候变化情景下,东北三省玉米需水量距平百分率大多表现为增加的趋势,最高可增加77.8%,而且不同地理环境及气候差异下,各地空间分布上也不尽相同。A2情景下,到2040年玉米需水量距平百分率平均增加27.2%,到2070年玉米需水量距平百分率平均增加34.5%,到2100年玉米需水量距平百分率平均增加42.9%;B2情景下,到2040年玉米需水量距平百分率平均增加28.6%,到2070年玉米需水量距平百分率平均增加33.3%,到2100年玉米需水量距平百分率平均增加37.3%。可见,未来中国东北三省水资源可能更趋于短缺状况。     

未来升温1.5℃与2.0℃背景下中国玉米产量变化趋势评估

基于ISI-MIP推荐的5个气候模式在4个RCP情景下的模拟结果,筛选21世纪末全球升温最接近1.5℃和2.0℃的气候数据,运用作物模型DSSAT,模拟升温1.5℃和2.0℃背景下中国玉米产量相对于基准时段1985-2006年的变化,揭示了1.5℃与2.0℃升温背景下中国玉米产量变化的空间分布。结果表明：升温2.0℃背景下玉米减产风险明显高于升温1.5℃,未来升温2.0℃背景下中国玉米减产面积比升温1.5℃背景下多6.2%,升温1.5℃和2.0℃背景下中国玉米平均减产幅度分别为3.7%和11.5%;从空间分布来看,升温1.5℃与2.0℃背景下未来中国玉米产量变化在区域分布上大致相似,但未来玉米增产和减产的面积和幅度不尽相同,在北方与西南玉米种植区都有一定的增产区域,其它区域大多以减产为主,其中西北部玉米种植区减幅最大;1.5℃升温背景下北方大部分地区气候条件对玉米生长有利,2.0℃升温背景下北方地区玉米减产也不明显,说明从近期到未来一段时间内,将全球升温控制在1.5℃以内,北方地区玉米仍具有一定增产潜力。     

基于CERES模型的临沂小麦生产的适应措施研究

采用英国Had ley中心的区域气候模式PREC IS结合CERES-W heat模型,对2071-2100年（2080 s）SRES A2、B2两种排放情景下山东临沂地区小麦生产进行模拟。结果表明：在PREC IS预测的2080 s气候变化情景下,不考虑CO2的肥效作用,临沂地区小麦的生育期明显缩短,产量有所下降,且A2情景下产量下降更明显;考虑CO2肥效作用时,能够补偿温度升高带来的负面影响,两种情景下的小麦产量均显著增加。未来如果保持品种和管理措施不变,A2、B2情景下分别将小麦的播期推迟15d、10d后,小麦的生育期将延长,产量将增加;通过品种参数对产量的影响分析,得出未来气候变化情景下应尽量培育穗粒数较多的品种以提高产量;根据现有品种的表现,未来气候变化情景下,临沂地区适当引进偏春性的冬小麦品种,将可能提高产量。总之,将播期推迟,培育穗粒数较大的小麦新品种或引进偏春性的小麦品种可以减小未来气候变化对临沂小麦生产的不利影响。     

播期和品种变化对马铃薯产量的耦合效应

马铃薯作为北方农牧交错带的主栽作物,随着气候向暖干化发展,其产量的稳定对保证该地区粮食安全有重要意义。为探究播期和品种耦合对农牧交错带马铃薯产量的影响,基于分期播种和品种比较试验的生育期和产量数据对APSIM-Potato模型进行调参和验证,利用验证后的模型设置连续模拟情景,比较不同耦合方式的产量及保证率,分析农牧交错带雨养马铃薯的最佳播期和品种耦合方式。结果表明：APSIM-Potato模型可以较好地模拟不同熟性马铃薯品种的生育期和产量,不同品种生育期实测值和模拟值的均方根误差（RMSE）均小于6.3 d,不同品种产量实测值和模拟值的归一化均方根误差（NRMSE）均小于7.6%。雨养条件下,农牧交错带不同播期和品种耦合下马铃薯的多年平均鲜重产量为10 494 kg·hm^-2;中熟品种‘克新一号’晚播（6月1日播种）的平均产量最高,为12 153 kg·hm^-2,且可以保证在66.7%的年份产量高于不同耦合方式的平均值,较早播（4月26日播种）和中播（5月15日播种）的平均鲜重产量分别高16.3%和7.0%,较同一时期播种的早熟品种‘费乌瑞它’和晚熟品种‘底西芮’分别高18.7%和17.2%。本研究揭示了农牧交错带马铃薯播期、品种和环境存在显著的交互作用,播期推迟和选种中熟马铃薯品种是应对气候暖干化的重要方式,为该地区马铃薯适应气候变化和保证稳产高产提供了科学依据。     

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.     

In-situ enrichment and analysis of atrazine-degrading microbial communities using atrazine-containing porous beads

We examined the community composition of microbes that colonized atrazine-containing beads buried in agricultural soils that differed in atrazine treatment history. Bacterial abundance was 5-40-fold greater in atrazine-fortified beads. In beads containing 20 mg atrazine kg⁻¹ buried in soil with a history of atrazine application (conditioned soil), the abundance of Actinobacteria increased approximately 80-fold whereas in control soil, Actinobacteria were enriched only 10-fold and the gamma-Proteobacteria and Planctomycetes increased by 60- and 25-fold, respectively. The gamma-Proteobacteria were enriched by 120- and 230-fold in beads containing 200 mg atrazine kg⁻¹ in conditioned and control soil, respectively. The results demonstrate that BioSep^® beads are a suitable matrix for recruiting a diverse subset of the bacterial community involved in atrazine degradation.