长江流域生态环境质量的时空演变特征及其驱动因素

[目的]探究2001—2021年长江不同子流域生态环境质量动态变化及其主导驱动因素,以期为长江流域生态环境保护与经济发展战略的协调发展提供理论依据。[方法]基于MODIS数据提取了2001—2021年5—11月长江流域遥感生态指数(remote sensing ecological index, RSEI),并基于RSEI分析了长江流域近21 a来生态环境质量动态及其驱动因素。[结果](1)长江流域中下游生态质量高于上游,南部高于北部。除2006年外,生态质量在中等级以上的面积占80%以上,整体生态水平较好。(2)生态环境质量变化整体以稳定变化为主,呈上升趋势的区域有乌江、太湖水系、宜宾至宜昌、宜宾至湖口、金沙江流域。(3)RSEI变化的主要驱动因素为湿度指标,其次为温度指数。(4)生态环境质量受到风速的正影响较大。气温升高会导致长江流域生态环境质量变差,但在金沙江流域、鄱阳湖流域、嘉陵江流域和湖口及以下干流地区气温升高有利于生态环境质量改善。(5)降水增多有利于大部分地区生态环境质量改善。[结论] 2001—2021年流域生态环境质量整体以不变趋势为主,但嘉陵江流域生态呈现退化现象需...     

白龙江流域生态环境质量动态监测与评价

[目的] 分析1990—2020年白龙江流域生态环境变化及驱动因素,为流域可持续发展提供科学依据和决策支持。[方法] 逐年筛选植被生长季6—9月的Landsat TM/OLI影像数据,计算绿度(NDVI)、湿度(WET)、热度(LST)、干度(NDSI)4个生态指标,采用主成分分析法(PCA)构建遥感生态指数(RSEI),对白龙江流域生态环境进行评价。[结果] 1990—2020年白龙江流域RSEI均值从0.531上升至0.675,生态环境质量总体好转;生态环境质量改善区域主要位于舟曲—武都段的白龙江两岸、宕昌县西北及岷江东岸,改善面积达8 393.97 km²,占总面积45.55%;各生态指标对于生态环境质量影响程度在1990年干度＞湿度＞热度＞绿度;2006年干度＞绿度＞湿度＞热度;2020年绿度＞湿度＞干度＞热度。[结论] 利用GEE平台实现RSEI模型扩展了在大范围尺度、长时间序列下对区域生态环境质量监测与评价,近年来白龙江流域生态环境质量整体呈改善态势,对于流域的保护治理工作仍需继续。     

1990—2020年阿拉尔垦区生态环境质量动态监测与评价

[目的]借助遥感生态指数(RSEI)对阿拉尔垦区生态环境质量进行动态监测与评价,分析1990—2020年研究区生态环境变化及驱动因素,为阿拉尔垦区发展和生态保护提供科学参考。[方法]选取1990,2000,2011和2020年4期Landsat TM/ETM~+/OLI影像数据,耦合绿度指标(NDVI)、湿度指标(WET)、干度指标(NDSI)、热度指标(LST)构建RSEI,结合研究区气候、人口、经济等驱动因素探究阿拉尔垦区生态环境质量动态变化。[结果] 1990—2020年阿拉尔垦区RSEI均值从0.344上升至0.468,生态环境质量总体好转;1990—2020年阿拉尔垦区生态环境质量变好区域主要位于垦区北部和南部地区,改善面积达1 756.36 km~2,占总面积45.92%;生态环境质量受自然因素和社会经济因素影响,社会经济因素对阿拉尔垦区生态环境质量变化起主导作用。[结论]近30 a来阿拉尔垦区生态环境得到有效改善。遥感生态指数(RSEI)在一定程度上可以快速、有效地反映1990—2020年阿拉尔垦区生态环境质量变化。     

基于RSEI模型的砒砂岩区生态环境质量演变研究

[目的]探究砒砂岩区生态环境质量状况，为当地生态环境治理工作提供科学依据。[方法]基于GIS和RS技术，利用遥感生态指数RSEI模型，分析砒砂岩区2001—2020年生态环境质量时空演变。[结果](1)基于砒砂岩区4期影像数据提取的遥感生态指数RSEI呈现先下降后上升的趋势，表明生态环境质量在缓慢改善；(2)绿度生态指标与湿度生态指标对砒砂岩区生态环境质量起正向作用，干度生态指标与热度生态指标会起到负面作用，并且绿度生态指标对生态环境质量改善的贡献率更高；(3)在2001—2020年间，生态环境质量改善区域占到研究区总面积的36.79%;生态环境质量恶化区域占15.68%,多为轻度退化。[结论]砒砂岩区2001—2020年间生态环境质量总体呈现出上升趋势，且生态环境质量对人为活动高度敏感，因此在改善生态环境的同时还需融入生态保护理念，做到人与自然和谐共生。     

基于RSEI的黄河中游地区生态环境质量时空演化特征及驱动因素——以延安市为例

[目的]生态环境质量评价是开展黄河中游地区生态环境保护和生态文明建设的重要基础，探究其生态环境质量动态及不同主导因子对其影响，可为生态环境保护战略与经济发展战略的协调发展提供理论依据。[方法]基于遥感生态指数(remote sensing ecological index, RSEI)并辅以Sen趋势分析、Manna-Kendall突变点检验、变异系数、Hurst法对黄河中游地区延安市1990—2020年的生态环境过去和未来演化特征进行了分析，并利用随机森林和结构方程模型探究了不同阶段RSEI对不同驱动因素的敏感性。[结果](1)延安市近31年生态环境质量整体呈变好趋势。其中，绿度和湿度指标均呈增加趋势，热度指标和干度指标均呈减小趋势，各指标共同促进了延安市的生态环境质量变化。(2) 1995年前RSEI为上升趋势，1995—2001年RSEI为下降趋势，2001年后RSEI呈增加趋势。(3) 1990—1995年RSEI变化属于较高波动变化，1996—2001年以高波动变化为主，2002—2020年属于较低波动变化。RSEI在未来一段时间内会出现大面积的下降趋势。(4) 1990—1...     

基于GEE云计算的南宁市生态环境质量时空分异监测

[目的]利用遥感技术及时、动态、客观地监测和评估城市生态环境质量变化,为城市生态环境规划与管理提供参考。[方法]以南宁市为案例,利用Google Earth Engine(GEE)平台对2000—2020年Landsat系列遥感影像进行像元级融合、消除色彩、去云等预处理,计算绿度、湿度、干度和热度这4个遥感指标,并采用主成分分析法构建遥感生态指数,定量评价南宁市生态环境质量动态变化及空间分异特征。[结果]南宁市RSEI多年平均值为0.615,总体呈现“下降—上升—稳定”的波动上升趋好的态势。生态环境质量较好的区域主要是自然保护区、山林地、草地和水域,生态环境质量较差的区域则集中于人类活动频繁,土地利用强度较大的城镇及城乡交错区、农耕区。生态环境质量与植被绿度和湿度指标呈正相关,与干度和热度指标呈负相关,且干度指标因子对RSEI影响程度最大。[结论]南宁市2000—2020年生态环境质量总体处于良好水平且呈上升态势。结合GEE和RSEI指数能够较好地反映城市生态环境质量,为城市生态环境质量长时间序列监测提供计算平台。     

2000—2020年漳河上游生态环境质量动态监测及驱动因素分析

[目的]探究漳河上游生态环境质量时空变化特征及其驱动因素,为该区域生态环境建设与治理提供科学依据。[方法]优化重构2000—2020年漳河上游Landsat影像,基于遥感生态指数(RSEI),引入坡度(slope)、归一化山地植被指数(NDMVI)、颗粒物浓度(DI)3项指标,构建考虑地形和颗粒物影响的改进型遥感生态指数(advanced RSEI,ARSEI)模型,辅以多种空间分析和统计方法对研究区生态环境质量进行定量评价。[结果](1)ARSEI具有较好适用性,能够准确地表征漳河上游生态环境质量状况。NDMVI对ARSEI影响最大,DI最小。(2)研究区生态环境质量整体呈“西南差、东北优”的空间格局,等级以较差和中等为主;研究期内,35.94%的区域表现为改善,并以改善1个等级为主,其中2010—2020年改善最为显著,变化格局呈“整体稳定,局部改变”的特点。(3)不同类型因子的影响力排序为：模型因子>地形因子>气象因子>社会因子>经济因子;所有影响因子均表现为协同增强作用,NDSI,NDMVI和slope的共同作用下对ARSEI空间异质性的影响最大。[结论...     

基于遥感生态指数的神东矿区1995-2020年生态环境质量的时空变化特征分析

[目的] 分析神东矿区1995—2020年生态环境质量时变化特征,为改善该区域生态环境提供科学依据。[方法] 基于1995—2020年6期Landsat 5 TM及Landsat 8 OLI数据,利用主成分分析法,选用干度指标（NDSI）、绿度指标（NDVI）、热度指标（LST）、湿度指标（WET）构建遥感生态指数（RSEI）。运用重分类将RSEI分为5级,按照重心迁移方法分析RSEIⅠ—Ⅴ等级的重心迁移情况,并分析RSEI的空间变化规律,实现利用RSEI对神东矿区的生态环境质量的动态监测和评价。[结果] ①神东矿区在1995—2020年生态环境状况明显提升,其中呈上升趋势的面积占矿区总面积的42.22%,绿度、干度指标对矿区生态环境质量影响较大。②矿区生态环境质量各级土地利用类型以草地、耕地为主,且生态环境质量变化受耕地、草地面积变化影响较大。③矿区生态环境质量主要以Ⅱ,Ⅲ级为主,Ⅰ级、Ⅱ级和Ⅴ级迁移幅度较大且重心整体向矿区西南、西北方向迁移。[结论] 1995—2020年神东矿区生态环境质量呈现总体上升态势,受植被生长情况和人类活动因素影响较大。     

基于遥感生态指数的元谋干热河谷生态环境动态监测及其驱动力分析

[目的] 探究元谋干热河谷2000-2020年生态环境变化现状，对该区域生态进行动态监测及其驱动力分析，为干热河谷的生态环境保护和可持续发展提供理论依据。[方法] 选取3期Landsat TM/OIL影像数据计算绿度(NDVI)、湿度(WET)、干度(NDBSI)、热度(LST)4个指标来构建遥感生态指数(RSEI)评价体系，并通过地理探测器对影响区域的生态环境因素进行量化分析。 [结果] ①2000，2010和2020年元谋干热河谷的RSEI均值分别为0.628，0.609和0.684，呈先降后升的变化趋势。 ②在2000-2020年这20 a间，区域内生态环境改善面积占29.58%，主要分布河谷两侧；生态恶化面积占21.45%，主要散布在农耕区和居民区周围。 ③对影响元谋干热河谷RSEI的10个因子进行驱动力分析发现，绿度指标和土地利用对RSEI的空间分异特征解释力最强。 [结论] 多因子交互结果显示，元谋干热河谷的生态环境现状是多重因素共同作用的结果，所有因子在交互作用下均有协同增强的作用；绿度指标和土地利用是研究区生态环境质量的主要驱动因子。因此，在探究元谋干热河谷生态环境恢复与保护，应合理规划利用土地资源，落实植被保护及修复政策及措施。     

2010—2020年陕西省神木市生态环境质量时空演变及其驱动因素

[目的] 陕西省神木市是黄河流域生态保护建设的重要地区。分析该地区生态环境质量变化,为资源型城市神木市的生态环境治理、修复及绿色发展提供科学依据。[方法] 选取2010,2015与2020年共3期Landsat遥感影像,利用主成分分析方法构建遥感生态指数(RSEI)作为生态环境评价指标,分析神木市生态环境质量时空演变格局,并通过地理探测器探究该地区生态环境驱动机制。[结果] ①神木市生态环境质量持续恶化,RSEI指数下降幅度达到12.47 %,在2010-2015年间下降最快;神木市生态环境质量很差与较差的面积增加幅度达到15.29 %。②神木市生态环境质量恶化以西北部的风沙区率先增强,随后转向地势较低的东南部和东北部。同时,神木市生态环境质量以较差和一般为主,两者总和占据神木市总面积的67.09 %。③植被覆盖度与绿度、湿度、干度及热度4个指标因素均表现出显著的驱动性,其中植被覆盖度解释力最高(达到62.4 %),是神木市生态环境质量的主要驱动力;多因子交互也均表示出协同增强的作用,夜间灯光、人口密度、热度与植被覆盖度交互作用最强。[结论] 神木市生态环境质量总体仍在进一步恶化,尽管前期退化得到遏制,但恶化区域在逐渐扩大,提高植被覆盖度可以有效增强神木市生态环境质量。为此应进一步落实植被绿化等生态保护措施,提升神木市高品质生态环境质量。     

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.