热水结合维生素C处理对甜樱桃果实褐变的控制研究

在预试验基础上,甜樱桃果实采用42℃热水及42℃热水添加0.1%维生素C各处理10 min,在0±0.5℃,相对湿度为85%~90%的条件下贮藏18 d后,再置于24±1℃,相对湿度为65%~70%条件下存放2 d,对果实的褐变参数及相关酶活性进行检测。结果表明,热水处理明显抑制甜樱桃果实L^*和H⁰值的下降及苯丙氨酸解氨酶(PAL)、多酚氧化酶(PPO)和过氧化物酶(POD)活性的上升。热水添加维生素C处理强化了这一抑制效果。贮藏后,热水和热水添加维生素C处理的果实感官综合评分分别为6.9和7.5,而对照仅为5.7。相关分析表明,感官综合评分与L^*、b^*和H⁰呈显著正相关,与a^*、PPO和POD活性呈显著负相关(P<0.05)。     

青花菜贮藏期间颜色变化动力学模型的建立

该试验利用CIE-L^*a^*b^*(Commission International de I'Eclairage,国际照明委员会制定的色彩空间坐标表色系统)中的a^*、b^*、H°、TCD(Total Color Difference,总色差)以及叶绿素含量和黄化级数来衡量青花菜色泽的变化情况, 旨在建立贮藏期间多种颜色指标的动力学模型。试验组分为0℃、5℃、10℃条件下分别在HDPE(high-density polyethylene高密度聚乙烯)薄膜单球包装与不包装两种情况下进行。试验结果显示，包装提升了青花菜贮藏期间的活化能，延迟了呼吸跃变的启动。非线性回归分析的结果表明，色泽参数b^*和TCD的速率常数符合Arrhenius模型，模型符合一级动力学反应；而a^*和H°的变化则可用多项式表示。贮藏青花菜的黄化级数与色泽参数b^*之间具有良好的相关性，为利用计算机视觉系统进行颜色分级提供了理论依据。     

门头沟西侧小流域地表雨水资源量预测

应用传统的径流系数法与SCS-CN模型法预测了北京市门头沟西侧小流域雨水资源利用潜力,并对比了不同方法预测的雨水资源量及其时空分布规律。结果表明,径流系数法预测的丰水年(P=25%)、平水年(P=50%)、枯水年(P=75%)和多年平均年份地表雨水资源量分别为:2.84×10⁷m³,1.98×10⁷m³,1.22×10⁷m³和2.14×10⁷m³。模型法预测的丰水年、平水年、枯水年和多年平均地表雨水资源量分别为:3.21×10⁷m³,2.16×10⁷m³,1.31×10⁷m³和2.50×10⁷m³,经验法预测值小于模型法。夏季的7月,地表的雨水资源利用潜力达到相应特征年份的最大值。     

贮藏温度对炝蟹品质的影响

为阐明不同贮藏温度下炝蟹品质的变化和食用安全性,本试验以三疣梭子蟹为材料制作炝蟹,探讨冻藏(-18℃)和冷藏(4℃)条件下炝蟹感官品质、菌落总数(TVC)、挥发性盐基氮(TVB-N)和生物胺的变化规律,并对其生物胺与其他品质指标进行相关性分析。结果表明,贮藏温度对炝蟹感官品质TVC、TVB-N等指标的劣变具有显著的影响。-18℃冻藏和4℃冷藏条件下,炝蟹感官品质分别于第10天和第6个月超出可接受限值;随着贮藏时间的延长,4℃冷藏条件下炝蟹TVC值显著增加,但至贮藏16 d时仍小于5 lg(CFU·g^-1),TVB-N值于贮藏12 d时超出一级鲜度临界值;-18℃冻藏过程中炝蟹TVC值略有增加,但变化不显著,TVB-N值于第6个月超出一级鲜度临界值。4℃冷藏过程中炝蟹中共检测出8种生物胺,而-18℃冻藏过程中共检测出5种生物胺。此外,色胺、腐胺和酪胺是炝蟹贮藏过程中产生的主要生物胺,且与其他品质均具有显著相关性。本研究结果为炝蟹在贮藏过程中的安全性和货架期预测提供了理论依据。     

尕海湿地区沼泽草甸生长季土壤碳氮组分对增温施氮的响应

[目的] 为探究高寒湿地土壤碳氮组分对气候变暖和氮沉降的响应特征。[方法] 以尕海湿地沼泽草甸为研究对象,采用开顶箱增温(OTC)和外源氮素(NH₄NO₃)添加模拟未来气候变暖及氮沉降试验,分别设置对照(CK)、增温(W)、施氮(N)和增温施氮(WN)4种处理。在试验进行1.5年后对土壤碳氮组分含量进行测定。[结果] (1)开顶箱增温装置提高0—20 cm土层平均温度1.126℃,显著降低0—10 cm土层土壤含水量(SMC)、pH、全氮(TN)、微生物量氮(MBN)、铵态氮(NH₄⁺—N)、有机碳(SOC)和可溶性有机碳(DOC)含量,提高硝态氮(NO₃^-—N)含量。(2)施氮显著降低NH₄⁺—N、SOC和10—20 cm土层微生物生物量碳(MBC)及DOC含量,增加土壤TN、MBN和NO₃^-—N含量。(3)增温施氮显著增加土壤SMC、TN、NO₃^-—N和MBC含量,降低MBN、NH₄⁺—N和DOC含量。(4)相关分析显示,土壤水分与各理化因子均存在正相关性,土壤碳氮组分间均呈正相关性。[结论] 模拟增温施氮缓解尕海湿地植物生长的温度和氮的限制,促进TN的积累,对土壤微生物量碳氮影响较大,导致土壤微生物量碳氮及分布特征发生转换。     

高透光率青梅浓缩汁贮藏过程颜色的动力学研究

该文研究了高透光率青梅浓缩汁在贮藏过程中吸光度与贮藏温度、贮藏时间的关系,建立了颜色变化动力学模型,为高透光率青梅浓缩汁贮藏条件的优化控制及保质期预测提供了科学依据。结果表明：高透光率青梅浓缩汁的吸光度变化(A₀-A)符合Arrhenius模型,且为零级反应,其反应常数K₀为1.13×10⁷,活化能Ea为59.89 kJ/mol。经验证,该模型预测值与试验实测值的相关系数达0.999,表明该模型是合适有效的。     

堆肥反应器中表面活性剂APG对牛粪堆肥酶活性的影响

利用堆肥反应器严格控制堆肥条件, 以牛粪为主要原料进行好氧堆肥, 在堆肥过程中加入表面活性剂烷基多糖苷(APG), 研究其对堆肥中微生物数量以及酶活性变化的影响。结果表明: 在好氧堆肥中添加表面活性剂APG对堆肥中的微生物无显著抑制作用, 微生物数量无显著变化(P>0.05); 但可以促进堆肥升温, 延长高温期。加入APG对堆肥中的过氧化氢酶活性几乎无影响, 最终APG处理和CK处理的酶活性值均达到1.17 mmol·g^-1左右; 加入APG后脲酶活性略有提高, 第2 d APG处理和CK处理的脲酶活性均达到峰值, 分别为32.15 mg(NH₃-N)·g^-1·24h^-1和30.17 mg(NH₃-N)·g^-1·24h^-1, 差异不显著(P>0.05), 第7 d达到最低值, 分别为0.81 mg(NH₃-N)·g^-1·24h^-1和0.38 mg(NH₃-N)·g^-1·24h^-1, 差异显著(P<0.05); APG处理对转化酶和纤维素酶活性均有明显的提高作用, 其中转化酶在第3 d加APG处理和CK处理峰值分别为18.15 mg(葡萄糖)·g^-1·24h^-1和11.77 mg(葡萄糖)·g^-1·24h^-1, 第21 d两处理峰值分别为24.09 mg(葡萄糖)·g^-1·24h^-1和20.71 mg(葡萄糖)·g^-1·24h^-1, 差异显著(P<0.05); 纤维素酶在第3 d加APG处理和CK处理峰值分别为58.77 mg·min^-1和30.62 mg·min^-1, 差异显著(P<0.05)。本试验结果表明, 添加表面活性剂APG可以提高堆肥中转化酶和纤维素酶活性, 促进堆肥中有机物质的转化, 一定程度上加快好氧堆肥进程。     

气调包装技术用于虾皮保鲜的效果研究

为改进虾皮贮藏质量,延长货架期,研究了气调包装(Modified Atmosphere Packaging)对虾皮的保鲜效果。采用3种不同浓度配比的N₂和CO₂气体和真空包装等方法对虾皮进行包装,分别于5℃、室温和35℃下贮藏。检测虾皮感观、色差、菌落总数和脂肪含量。结果表明：低温有利于虾皮保鲜,高浓度CO₂气调贮藏能抑制虾皮中的微生物繁殖,减缓脂肪蚝蛤败速度,但CO₂浓度过高易使虾皮产生异味,影响感观品质。气调与低温结合可延长虾皮的保鲜期2个多月,推荐的气调气体比例为70%N₂/30%CO₂,低温冷藏。     

猕猴桃低温、气调、保鲜剂复合贮藏保鲜技术

猕猴桃是呼吸跃变型果实，温度、乙烯和呼吸强度是影响贮藏寿命的主要因素，采用低温、限气和保鲜剂复合贮藏保鲜技术，贮温(0±0.5)℃，O₂ 2%～3%，CO₂ 4%～5%，KMnO₄作乙烯吸收剂，简易库贮藏，可使其贮藏180 d以上，平均果实硬度 ≥2.5 kg/cm²，硬果率≥92%,商品果率≥96%，维生素C保存率≥80%，鲜度指数≥90%。贮后果实外观新鲜，果脐绿色，色、香、味、形俱佳。     

不同气体成分贮藏对大久保桃果实品质的影响

该文研究了大久保桃在不同气体成分下贮藏60 d以及出库后在20℃下货架期3 d后果实硬度、褐变指数、可溶性固形物含量、pH值、膜透性、出汁率和感官品质的变化。结果表明,1%的O₂对桃果实产生伤害,表现为表面色泽非正常变化、桃固有风味丧失并产生严重异味;(5～10)%O₂、(5～10)%CO₂气体成分能够在60 d的贮藏期内保持桃果实的品质,尤其是10%O₂＋10%CO₂处理较好地保持了果实的风味、质地和色泽,出库后果肉不褐变。与冷藏对照相比,气调贮藏能有效地延缓果实软化,抑制pH值和出汁率的升高,但对可溶性固形物的影响不大;在相同O₂浓度下,随CO₂浓度升高(<10%),果实在货架期期间的软化程度、褐变指数下降幅度、pH值上升程度和膜透性增加幅度均增大,表明果实能够进行正常后熟。本研究推荐的大久保桃果实气调贮藏的适宜气体指标是10%O₂＋10%CO₂。     

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,     

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.     

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.     

Properties of anaerobically digested and composted municipal solid waste assessed by linking soil mesofauna dynamics and nitrogen modelling

We have studied the effect of anaerobically digested (ADMSW) and composted municipal solid waste (CMSW) on mineralization and foodweb dynamics to verify the hypothesis that ADMSW would immobilize N right after addition to soil in contrast to addition with CMSW. Another hypothesis was that the mesofauna (enchytraeids and microarthropods) would stimulate N release from the decomposer community. We measured excretion of -N and urea-N from the mesofauna and hypothesized that enchytraeids would release urea. ADMSW and CMSW were amended to pots with sandy loam and barley. The pots were divided into treatments with or without mesofauna. Mesofauna, plant N and biomass, soil N and ergosterol (fungal biomass) were measured over a 113-day period of four equidistant samplings. Soil respiration, N mineralization and N release by the mesofauna were modelled from concurrent studies. ADMSW- and CMSW-treated soils initially (<20 days) immobilized N. The amendments did not increase plant growth substantially, and this was probably due to N-limitation in the early stages of plant growth. Enchytraeid abundance was about three times higher in ADMSW- than CMSW-treated soils, indicating that ADMSW contained more labile compounds, bacteria, and microfauna. The mesofauna did not affect N-content, but the cumulated -N excreted by the mesofauna was estimated to be substantial and about one-fifth of total plant N in ADMSW. An explanation for this discrepancy might be that in the absence of the mesofauna, other members of the detrivore and microbivore community performed the mesofauna’s function. Neither enchytraeids nor microarthropods excreted urea.     

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,     

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,     

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.