What Is the Role of ε in the Escherichia coli ATP Synthase?

The ATP synthase from Escherichia coli is a prototype of the ATP synthases that are found in many bacteria, in the mitochondria of eukaryotes, and in the chloroplasts of plants. It contains eight different types of subunits that have traditionally been divided into F₁, a water-soluble catalytic sector, and F_o, a membrane-bound ion transporting sector. In the current rotary model for ATP synthesis, the subunits can be divided into rotor and stator subunits. Several lines of evidence indicate that is one of the three rotor subunits, which rotate through 360 degrees. The three-dimensional structure of is known and its interactions with other subunits have been explored by several approaches. In light of recent work by our group and that of others, the role of in the ATP synthase from E. coli is discussed.     

Relationship between the population of viable sclerotia ofSclerotium rolfsii in soil to cropping sequence in the Nigerian savanna

Populations of viable sclerotia ofSclerotium rolfsii were highest in soil in a field in which tomato was planted for three successive years before sampling and in one in which tomato followed groundnut in the 2 years prior to this study. The lowest sclerotial numbers were recorded in fields in which groundnut followed maize or in which maize or sorghum was the last crop before sampling.     

Prescribed moorland burning meets good practice guidelines: A monitoring case study using aerial photography in the Peak District,UK

Upland moors in the UK have been managed for centuries using rotational prescribed-burning, but in recent years there has been contentious debate over its continuing use due to varying effects on moorland ecosystem services. Prescribed-burning should only be carried out using good-practice codes, which include restrictions on the size, location and frequency of burns. Good burning practice is an indicator of management standards and habitat condition in moorland landscapes. However, there has been little attempt to assess management performance with respect to these restrictions. We investigated prescribed-burning on a case-study estate (Howden Moor) in the Peak District National Park from 1988 to 2009 using management maps and aerial photography. The annual area burned (0.9%) was far below recommendations (10%) and patches were in keeping with the target sizes specified (mean ± se: 2370 ± 70 m²). The risk of a large or escaped fire was very low, with less than 1% of fires greater than 15,000 m². However, only 28.9% of the total burnable area was burned, leaving the rest unmanaged and accumulating fuel. Future guidelines might recommend the application of prescribed-burning across the range of Calluna vulgaris growth phases, to reduce fuel load and promote biodiversity at the landscape scale. We show that vegetation mapping and aerial photography are an effective method for monitoring prescribed-burning practice on moorlands. The information derived from such monitoring studies should lead to greater confidence in the standard of prescribed-burning and adherence to good-practice guidelines and requirements imposed by statutory authorities.     

Light-induced linear dichroism in photoreversibly photochromic sensor pigments. – VI. Relation between the two pigments of the mycochrome system in Alternaria cichorii

Conidiation in Alternaria cichorii Nattras is reversibly stimulated by near ultraviolet radiation (NUV, ca 313 nm) and inhibited by blue light (ca 450 nm) and seems to be a mycochrome-mediated process. After induction with plane-polarized NUV, blue light polarized perpendicularly to the NUV was more effective in counteracting the induction than was blue light polarized parallel to the NUV. From this the conclusions are drawn that (a) both the blue-absorbing component (presumably a flavo-protein) and the P_NUV of the mycochrome system are membrane-bound and that (b) the transition moment associated with blue light absorption in the presumed flavoprotein forms an angle of at least 53° with the transition moment associated with NUV absorption in P_NUV.     

ULTRASTRUCTURE,DEVELOPMENT AND CYTOPLASMIC ROTATION OF SETA-BEARING CELLS OF COLEOCHAETE SCUTATA (CHLOROPHYCEAE)1

Part of the cytoplasm, which always contains the plastid, of seta-bearing cells of Coleochaete scutata Bréb. rotates clockwise about the base of the seta. Many golgi bodies, vesicles and much endoplasmic reticulum occupy the bridges between the rotating central core of cytoplasm and the stationary peripheral layer of these cells. The setae, which grow from their base, are devoid of organelles other than vesicles and elongate mitochondria. At irregular intervals along the thin seta wall are annular thickenings containing callose. Microtubules which encircle the base of the seta disappear on treatment with colchicine. This drug had no effect on the speed of rotational streaming or the growth rate of existing hairs but did inhibit the development of new setae. Cytochalasin B slowed, but did not stop, streaming after 3 h exposure. However caffeine, but not EDTA, EGTA or the Ca ionophore A23187, reversibly inhibited cyclosis. The mechanism of cytoplasmic rotation is discussed in the light of these drug treatments and the presence of actin in the alga.     

华东稻麦轮作生态系统的N2O排放研究

根据对华东稻麦轮作周期的N₂O排放及其影响因子的连续观测结果,分析了N₂O排放时间变化以及施肥、灌溉、温度、土壤湿度和土壤速效N素含量对N₂O排放的影响,同时还比较分析了稻田N₂O和CH₄排放.研究结果表明,稻麦轮作周期内,水稻生长季的N₂O排放量仅占30%,稻田持续淹水可比常规灌溉增加CH₄排放量26%,减少N₂O排放量11～26%.     

桔梗水浸提液对小麦幼苗的化感作用

采用培养皿滤纸法研究了不同浓度桔梗水浸提液对小麦的幼苗生长及生理生化指标的影响,探讨桔梗植株水浸提液对小麦的化感作用,推测其可能的生理机制。结果表明：桔梗植株水浸提液对小麦幼苗的地上部生长表现为低浓度（≤1mg／mL）促进、高浓度（5—20mg／mL）抑制作用;对根部生长为抑制作用,且抑制强度大于地上部。随处理浓度的升高,小麦幼苗体内POD活性、脯氨酸含量、MDA含量逐渐升高;CAT活性、根系活力、光合色素含量先升高后降低;可溶性蛋白含量和伤害率先降低后升高。桔梗植株水浸提液对小麦总体的化感效应表现为低促高抑,小麦可作为桔梗的轮作作物种植。     

稻鸭共作有机农业模式的能值评估

应用能值分析方法对稻鸭共作有机农业模式（模式Ⅰ）和对应的稻麦常规生产模式（模式Ⅱ）进行比较研究,并比较了两种模式的生态经济效益.结果表明,模式Ⅰ的能值效益高,自组织能力、可持续发展能力强,产品安全性高,净能值产出率（EYR）、系统产出能值反馈率（FYE）、能值可持续指标（ESI）分别是模式Ⅱ的1.57、14.1和8.71倍;基于能值的产品安全性指标（EIPS）模式Ⅰ为0,模式Ⅱ为-0.66;模式Ⅰ对环境的压力小于模式Ⅱ,能值投资率（EIR）,环境负载率（ELR）分别是模式Ⅱ的40.1%和18.3%;但模式Ⅰ的经济效益低于模式Ⅱ,其产出、毛收入和净效益分别低于模式Ⅱ15.7%、9.6%和29.6%;以能值 货币价值计算,模式Ⅰ的产投比、毛收入和净收入分别高于模式Ⅱ50%、102.6%和136.4%.随着生产系统的优化和市场对有机食品认知程度的提高,模式Ⅰ的经济效益具有提高的潜力.     

不同轮作制对农田生态系统中土壤硫攫取与归还途径的研究

研究了我国北方地区主要轮作制度下,土壤一植物生态系统中硫的主要输入(归还)与输出(攫取)途径．结果表明,在我国北方普遍推行的小麦-玉米轮作制中,作物收获物从土壤中攫取的硫素总量为每年26．4kg·hm^-2,由根系和植物其它残留物归还给土壤的硫素为每年6．8kg·hm^-2;在小麦．大豆轮作制中。作物收获物从土壤中攫取的硫素总量为每年24．4kg·hm^-2,对土壤的归还量为每年7．2kg·hm^-2;而在玉米-油菜轮作制中,收获物从土壤中攫取的硫量为每年45．4kg·hm^-2,归还给土壤的硫量为每年8．7kg·hm^-2;其它作物如棉花、高粱、花生、水稻种植一季通过收获物从土壤中带走的硫量分别为每年7．9、6．4、6．7和18．9kg·hm^-2。对土壤的归还量分别为每年2．6、1．8、4．3和5．6kg·hm^-2．通过对系统主要输入输出通量的估算,几种主要农田生态系统硫盈亏的状况计算结果说明,供试作物皆存在硫亏缺状况：小麦每年6kg·hm^-2、玉米8．5kg·hm^-2、油菜24kg·hm^-2、水稻7．1kg·hm^-2．     

不同轮伐期对杉木人工林碳固存的影响

在全球气候变化背景下, 科学的经营管理是人工林碳汇提升的主要途径。合理轮伐期从一定程度上反映了人工林集约经营的理念, 是实现森林结构调整的主要影响因素之一。杉木(Cunninghamia lanceolata)多代连栽出现立地生产力下降与轮伐期的选择密切相关, 开展不同轮伐期对杉木人工林碳固存影响的研究, 可为其可持续经营提供理论依据。通过设置不同年龄序列的杉木人工林野外观测样地, 应用野外观测数据对FORECAST模型进行验证, 在此基础上模拟不同轮伐期对其碳固存的影响。结果表明: (1)短轮伐期(15年)在150年间的总固碳量较高, 但固碳持久性较低, 每个轮伐期之间的固碳量下降幅度较大, 是一种不可持续的经营模式。(2)正常轮伐期(25年)和长轮伐期(50年)的总固碳量低于短轮伐期, 但长轮伐期固碳持久性更强, 有利于维持每个轮伐期内固碳量的稳定。(3)在好的立地条件下(立地指数(SI) = 27), 轮伐期越短对地力消耗影响越大, 为了碳固存的持久性, 建议杉木人工林的生态轮伐期选择在25年以上。(4)应用FORECAST模型可以定量地评估人工林的固碳能力, 且该固碳能力是基于不同经营管理措施下的可持续固碳能力。