不同营养液浓度与喷雾频率对雾培马铃薯生长及产量的影响

试验以营养液浓度为主区,喷雾频率为副区,马铃薯块茎形成前后为前期、后期,研究雾培条件下不同生育期不同营养液浓度与喷雾频率对马铃薯生长和产量的影响,为马铃薯原原种生产实践提供参考。营养液浓度梯度分别设为0.6 A∶0.8 A(前期∶后期)、0.8 A∶A、A∶1.2 A,用C0.6∶0.8、C0.8∶1、C1∶1.2表示,喷雾频率为40s/10 min∶40 s/20 min(喷雾/间隔,前期∶后期)、40 s/15 min∶40 s/25 min、40 s/20 min、40 s/30 min,用T10∶20、T15∶25、T20∶30表示,并采用主成分聚类分析对各处理进行综合排序与评价。结果表明:定植30 d,营养液浓度、喷雾频率及二者交互均可极显著增加马铃薯各部位干重且均为处理C0.8∶1T20∶30最大;定植60 d,各处理间生物量差异显著性较大且处理C1∶1.2T20∶30全株干重最大。各处理G≤3 g小薯在薯类分级中所占比例均最大,处理间3gG≤5 g小薯差异不大,但其他等级小薯差异较大,处理C1∶1.2T15∶25在单株薯数、单株薯重和折合产量上均最大。通过主成分聚类分析,处理C1∶1.2T15∶25得分最高,且各处理对雾培马铃薯生长的影响可聚为五类,处理C0.8∶1T20∶30与C1∶1.2T15∶25聚为一类,综合评价为一等;处理C0.6∶0.8T10∶20、C1∶1.2T20∶30和C0.6∶0.8T15∶25聚为一类,综合评价为二等;处理C0.8∶1T15∶25单独聚为一类,综合评价为三等;处理C0.6∶0.8T20∶30和C0.8∶1T10∶20聚为一类,综合评价为四等;处理C1∶1.2T10∶20单独聚为一类,综合评价为五等。因此,适当加大营养液浓度,延长喷雾间隔时间有利于雾培马铃薯生长及产量增加。     

不同氮素形态比对雾培马铃薯生长和原原种产量的影响

通过雾培试验研究4种不同比例硝态氮(NO_3~--N)和铵态氮(NH_4~+-N)对马铃薯品种米拉和川芋802植株生长及原原种生产的影响,为种薯生产的氮肥高效利用提供理论依据。结果表明,定植60 d,全硝态氮处理(0∶4)的植株干物质积累、匍匐茎数量及叶面积指数最高;而增铵营养更利于植株定植60 d后的生长发育,其中铵硝比(2∶2)处理下植株干物质积累、匍匐茎数量、叶面积指数增幅最大,表明块茎形成期全硝态氮更利于植株生长。铵硝比(2∶2)处理下,两个品种的氮积累最高,表明增加一定的铵态氮能增强马铃薯氮素利用率。产量上,全硝态氮处理(0∶4)单株结薯数最高(米拉115.5粒/株,川芋802为42.5粒/株),随铵硝比增大,单株结薯数降低,但大薯比例随之提高,最高为铵硝比(3∶1)处理(米拉64%,川芋802 76%)。因此,全硝态氮能增加结薯数量,增铵能促进马铃薯块茎膨大。     

营养与株型调控对雾培马铃薯的结薯生理影响

本研究采用3套营养液配方与3种株型调控措施探讨了不同马铃薯(Solanum tuberosumL.)品种的结薯生理效应。结果表明:不同营养液配方对雾培马铃薯的“源流库”皆存在一定的影响;采用以前期最小、结薯期最大的N/K和NH4 -N/NO3--N比值的A2营养液,对植株的光合势、叶绿素含量、根系活力、匍匐茎数、总薯数、总薯重以及后期末茎叶鲜重与干重等的增长刺激作用最大,其中又以“CIP24”品种的结薯性能最好;下放植株、喷施矮壮素和剪尖处理的不同组合均能使“CIP24”品种在A2营养液下增加光合势,降低株高,增加鲜重和增大根系体积。     

氮素水平对雾培马铃薯植株生长和产量的影响

在雾化栽培条件下,以马铃薯主栽品种川芋117和米拉为试验材料,研究了不同氮素水平下马铃薯植株农艺性状、干物质含量及产量变化。结果表明,氮素水平对川芋117和米拉的株高、茎粗、叶片数、叶面积、叶绿素含量、匍匐茎数、全株干物质含量、单株结薯数、产量均有极显著影响。品种对株高、茎粗、叶片数、叶绿素含量、匍匐茎数、全株干物质含量、单株结薯数、产量和收获指数均有显著或极显著影响。除叶绿素含量外,植株的各农艺性状在氮素水平为240 mg/L处理最高,氮素过高,反而不利于植株生长发育。随氮素水平的增加,叶、茎、根和块茎的干物质积累量呈先增高后降低趋势,均在240 mg/L氮素处理干物质积累量达到最大值。氮素水平对川芋117和米拉的单株结薯数和结薯产量均影响显著,随氮素水平从120 mg/L增加至600 mg/L,单株结薯数和产量先增加后显著下降,氮素浓度为240 mg/L时,两个品种的单株结薯数及产量达到峰值,较高氮处理,增幅分别为71.6%和107.8%,91.7%和83.1%。600 mg/L氮素处理,0.5～1 g小薯比例显著高于240 mg/L氮素处理。总体来看,240 mg/L的氮素浓度为雾培生产马铃薯原原种最佳浓度。     

AM 真菌对花生与甘薯产量的影响

在大田条件下试验研究了丛枝菌根(Arbuscular mycorrhiza,AM)真菌Glomus versiforme Berch及混合菌种[Glomus mosseae Nicolson&Gedermann+Sclerocystis smuosa(Gerd.Bakshi)Almeida ＆ Schenck]对花生与甘薯生长及产量的影响结果表明,供试AM真菌能显著促进花生植株生长健壮,增加单株果数,单位面积产量比对照增加21.3%.接种Glomus versiforme处理的甘薯植株高度和茎叶质量均低于对照,未增加植株生长量和产量;混合菌种处理则提高甘薯的生长量和增加单株薯块数,其单株产量、单位面积产量分别为对照的1.6和1.4倍,表明大田应用时不同作物应采用不同AM真菌.     

补充灌溉对半干旱区马铃薯产量和水分利用效率的影响

采用随机区组设计,研究了陇中半干旱区不同补灌时期及补水量对马铃薯产量形成和水分利用效率的影响。结果表明,苗期补水、现蕾期补水和膨大期补水较对照均能显著提高马铃薯产量;补水处理水分利用效率（WUE）均高于不补水处理（对照）;其中,现蕾期补水3kg/穴处理产量和水分利用效率增幅最高,产量和WUE分别达19 178.57kg/hm2（较对照处理高21.77%）和52.75kg/（hm2.mm）;与对照相比,各补水处理普遍优化了马铃薯各产量构成性状,有利于大薯率和中薯率的提高,单株结薯数和单株薯产量也较高。因此,现蕾期为旱地马铃薯需水关键期,对水分的变化敏感;现蕾期补水3kg/穴,可以作为半旱区马铃薯适宜的抗干旱节水高产种植模式。     

接种丛枝菌根真菌对脱毒马铃薯微型薯生长及产量的影响

在大田条件下采用混合菌种(Glomus mosseas+Glomus intraradices)作为接种剂,研究了接种丛枝菌根真菌对脱毒马铃薯微型薯菌根侵染、磷吸收和产量的影响。结果表明,接种菌根真菌,马铃薯菌根侵染率增加73.3%,植株吸磷量增加15.4%,块茎产量增加8.0%。上述结果证明,在大田条件下,接种菌根真菌能侵染马铃薯根部,促进植株对磷的吸收,从而增加产量。     

全有机营养栽培对樱桃番茄养分吸收、产量和品质的影响

为探求樱桃番茄全有机营养栽培养分的均衡供应,追求绿色优质的栽培目标,实现樱桃番茄全有机栽培的精准化管理。以“福特斯”樱桃番茄为试材,采用有机基质袋式栽培浇灌有机营养液的方式,设置2种有机营养液配方处理：F1(猪、牛、羊粪浸提液体积比2∶1∶1),F2(猪、牛、羊粪浸提液体积比4∶1∶1),配方混合配制后稀释到氮元素与山崎营养液中氮元素含量一致;3种有机营养液供应量：M1(开花坐果期每次0.6 L·株^-1,果实成熟期每次1.4 L·株^-1)、M2(开花坐果期每次0.8 L·株^-1,果实成熟期每次1.2 L·株^-1)、M3(开花坐果期每次1.0 L·株^-1,果实成熟期每次1.0 L·株^-1),两因素组合得到6个处理,以山崎营养液作为无机营养液配方处理(F0M3)。通过分析植株干物质累积量、养分含量、光合特性及最终果实产量和品质等指标,探究有机营养液配方及阶段供应量对设施全有机樱桃番茄生长的影响,以满足樱桃番茄不同生长时期的养分需求。结果表明,开花坐果期减少营养...     

马铃薯/玉米不同行数比套作对马铃薯光合特性和产量的影响

以单作马铃薯为对照,设置2︰2和3︰2两种马铃薯/玉米套作的行数比,研究大田套作条件下马铃薯光合特性的动态变化及其对产量的影响。结果表明:套作显著降低了马铃薯整个生育期叶面积指数(LAI)、比叶重(SLW)和叶绿素a/b值(Chla/b),提高了马铃薯叶绿素a(Chla)、叶绿素b(Chlb)、叶绿素总(Chla+Chlb)含量。整个生育期套作3︰2行数比LAI显著高于套作2︰2行数比,SLW块茎形成期显著低于套作2︰2行数比,苗期、淀粉积累期高于套作2︰2行数比;Chla、Chlb、Chla+Chlb块茎增长期显著高于套作2︰2行数比,淀粉积累期低于套作2︰2行数比;Chla/b值块茎增长期和淀粉积累期显著高于套作2︰2行数比;套作降低了3︰2行数比Chla和Chla+Chlb随生育期递减的速率。套作显著降低了马铃薯净光合速率(Pn)、气孔导度(Gs)、蒸腾速率(Tr)、气孔限制值(Ls),提高了胞间CO2浓度(Ci)和水分利用率(WUE),非气孔因素是套作马铃薯净光合速率降低的主要因素;套作3︰2行数比的Pn、Gs、Tr、Ci显著高于套作2︰2行数比,WUE显著低于套作2︰2行数比。与单作相比,套作显著降低了两种行数比的大薯数量和大薯鲜重;套作2︰2行数比小薯数量和小薯鲜重显著降低,但套作3︰2行数比小薯数量显著增加,小薯鲜重差异不显著;套作3︰2行数比小薯数量和小薯鲜重显著高于套作2︰2行数比。总之,套作改变了马铃薯的光合特性,并显著降低了马铃薯块茎产量;2︰2行数比无套作优势(LER为0.88),3︰2行数比具有较强的套作优势(LER为1.24),在生产中宜采用套作3︰2行数比模式。     

2∶2与3∶2行比下不同马铃薯品种与玉米套作的光合生理响应机制(摘要)

在重庆北碚槽上(海拔650m),研究了马铃薯/玉米套作2∶2和3∶2行比下,4个不同类型马铃薯品种(费乌瑞它、中薯5号、鄂马铃薯5号和米拉)的光合生理响应机制。主要结果如下:1.2∶2较之3∶2行比,马铃薯平均株高更高,LAI偏低,HI、单株主茎数和分枝数差异因品种而异,单株结薯数和薯重偏低;套作条件下单株结薯数以‘中薯5号’最多;套作生物产量2种行比均以‘费乌瑞它’和‘鄂马铃薯5号’较高,‘中薯5号’和‘米拉’较低;复合产量和总产值均较高的组合为费乌瑞它3∶2行比;套作LER(土地当量比)>1,套作优势大小依品种和行比而不同。2.中、下位叶PAR截获,米拉群体高于中薯5号群体;两品种冠层群体平均PAR3∶2行比高于2∶2;随着叶位从高至低,马铃薯群体中、下位叶PAR呈下降趋势,降低幅度套作高于单作。3.套作提高了马铃薯叶片Chla、Chlb、Chla+Chlb含量;2种行比套作之间叶绿素含量、SLW的差异因品种和生育时期不尽一致,但LAI和叶绿素a/b值3∶2行比套作高于2∶2行比套作;套作降低了马铃薯Pn、Gs、Tr,提高了WUE。两品种3∶2行比套作Pn、Gs、Tr均高于2∶2行比套作;套作降低了马铃薯上位叶Pn、Gs,提高了中、下位叶Pn、Gs,不同叶位Ci、Tr、WUE存在品种间差异。4.马铃薯叶、茎、块茎干物质积累及全株干物质积累总量2∶2行比低于3∶2行比;套作中薯5号干物质积累总量高于套作米拉。5.套作降低了马铃薯SPC(可溶性蛋白)含量,提高了叶片Pro(脯氨酸)含量、SOD活性、POD活性;套作提高了中薯5号MDA含量和CAT活性,降低了米拉MDA含量和CAT活性;两品种套作CAT活性3∶2行比高于2∶2行比;套作中薯5号SPC高于套作米拉,SOD活性低于套作米拉。6.适合与玉米套作的马铃薯品种和套作行比为费乌瑞它/玉米3∶2行比和2∶2行比、中薯5号/玉米3∶2行比、米拉/玉米3∶2行比。     

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.