铝诱导蚕豆气孔保卫细胞凋亡研究

植物叶表面的气孔保卫细胞是研究信号转导的模式实验系统,对环境变化反应灵敏而准确,采用蚕豆叶面气孔保卫细胞,研究了铝（AlCl3）对细胞的毒性效应。结果表明,在1～10 mmol.L^-1范围内,AlCl3可使气孔保卫细胞活性降低,部分细胞死亡,且随着浓度的增高细胞死亡率增高;死细胞呈现核固缩、核降解、凋亡小体等典型凋亡特征。凋亡抑制剂Z-Asp-CH2-DCB或TLCK与AlCl3共同作用时,保卫细胞死亡率显著降低;一定浓度的抗坏血酸（AsA）或过氧化氢酶（CAT）以及Ca2＋螯合剂乙二醇四乙酸酯（EGTA）或Ca2＋通道抑制剂LaCl3与AlCl3共同作用时,细胞死亡率降低。研究结果表明,铝诱导的蚕豆保卫细胞死亡可能是一种细胞凋亡过程,由胁迫诱发的活性氧介导,通过激活质膜钙通道,引起胞内Ca2＋水平改变,进而介导细胞凋亡。     

苏云金芽胞杆菌Bt9875杀虫晶体蛋白可诱导Caspase和Bcl-2家族参与调控HL-60细胞凋亡

研究Caspase家族与Bcl-2家族参与调控苏云金芽胞杆菌(Bacillus thuringiensis,Bt)Bt9875杀虫晶体蛋白对人急性髓细胞性白血病细胞HL-60的影响.本实验采用MTT法检测了杀虫晶体蛋白诱导HL-60细胞凋亡后的Caspase家族的活性和Caspase凋亡酶抑制剂对杀虫晶体蛋白诱导HL-60细胞凋亡的影响;采用Western blot检测了杀虫晶体蛋白诱导多聚ADP-核糖聚合酶(PARP)降解、Bcl-2/Bax调控和细胞色素C的释放.研究结果表明,杀虫晶体蛋白作用HL-60细胞后,激活了Caspase-3、Caspase-8和Caspase-9,在48 h内Caspase家族抑制剂(Z-VAD-FMK)、Caspase-3抑制剂(z-DEVD-FMK)和Caspase-9抑制剂(Z-LEHD-FMK)均可显著抑制杀虫晶体蛋白诱导的细胞凋亡;杀虫晶体蛋白可明显上调促凋亡蛋白Bax的表达,同时下调抗凋亡蛋白BCl-2的表达,并观察到胞浆中细胞色素C的释放.初步证明了Bt9875杀虫晶体蛋白诱导的HL-60细胞凋亡是由Caspase家族和Bcl-2家族共同调控的,线粒体途径在诱导细胞凋亡过程中起着重要作用.     

钙离子对海盐和NaCl胁迫下菊芋幼苗生理特征的响应

用不同浓度CaCl2（5mmol／L，10mmol／L，20mmol／L）对处在相同含盐量的海盐和NaCl两种盐胁迫处理下的菊芋幼苗进行化学调控，研究了钙离子对两种盐处理的菊芋幼苗的生物量、SOD活性、MDA含量、相对电导、叶绿素含量和Pn的影响。研究结果表明：（1）当菊芋处于海盐和NaCl两种盐胁迫下时，菊芋的生物量、SOD活性、叶绿素含量和Pn均显著降低，MDA含量和相对电导显著增加；（2）当施入钙离子后，两种盐对菊芋幼苗的胁迫不同程度降低，其中以中浓度的钙离子效果最好，使菊芋的生物量、SOD活性、叶绿素含量和Pn显著增加，MDA含量和相对电导显著降低，当CaCl2浓度大于10mmol／L时，则钙离子对盐胁迫的缓解作用降低，说明适量的钙离子有效缓解了盐胁迫所致的氧化损伤，从而抑制了脂质过氧化作用，增加叶绿素含量。维持较高的光合速率，增加干物质积累，从而使生物产量增加；（3）在5mmol／L，10mmol／L钙离子浓度下，钙离子对海盐胁迫的缓解作用显著优于NaCl，但在20mmol／L浓度下，两个处理差异不显著。     

牛肉宰后嫩化机制的研究

为了阐明牛肉的成熟机理,本试验模拟尸僵后牛肉的内在环境和成熟温度,将纯化后的钙激活酶Ⅰ(μ-Calpain)、内源性钙激活酶Ⅰ专一抑制剂(Calpastatin)、肌原纤维和钙激活酶Ⅰ外源性抑制剂抑亮酶肽(Leupeptin)用于6个不同的处理组合,反应不同时间后,分别做变性聚丙烯酰胺凝胶电泳(SDS-PAGE)和蛋白质印迹分析(Western-blotting).结果表明,Ca2 (100 μM)对肌原纤维没有降解作用,而在含Ca2 (100 μM)的反应体系中,μ-Calpain对肌间线蛋白(Desmin)和肌钙蛋白T(Troponin-T)都有明显的降解作用,且降解产物和宰后牛肉自然成熟条件下的降解产物类似;Calpastatin不能完全抑制μ-Calpain的活性;离体反应和自然成熟的牛肉中的肌动蛋白都没有发生变化.以上结论表明Ca2 很可能是通过激活μ-Calpain而间接发挥对肌原纤维的降解作用,而溶酶体组织蛋白酶在牛肉成熟的早期对嫩度的改善贡献不大.     

外源添加抑制剂对芦蒿吸收Cd和Pb的影响

以水生植物芦蒿为试验材料,通过人工培养液温室培养方法,研究了代谢抑制剂、P-型ATP酶抑制剂、蛋白合成抑制剂、离子通道抑制剂对芦蒿吸收Cd和Pb的影响。结果表明,代谢抑制剂（Na3N）和P-型ATP酶抑制剂（Na3VO4）对芦蒿Cd和Pb的吸收均有一定的抑制作用,说明芦蒿对Cd和Pb存在主动吸收。钙离子通道抑制剂LaCl3显著抑制芦蒿根部对Cd的吸收,而对Pb的吸收没有明显的抑制作用,说明芦蒿对Cd的吸收与钙离子通道有关;蛋白质合成抑制剂放线菌酮（CHD）对芦蒿Cd和Pb的吸收有显著的抑制作用,说明芦蒿对Cd和Pb的吸收与一些蛋白质或酶的诱导合成及其活性密切相关。     

盐胁迫下外源钙对高羊茅种子萌发和幼苗离子分布的影响

该文模拟了上海市临港新成陆地盐渍化土壤的盐分特点,并在100 mmol/L NaCl盐胁迫下,以常见牧草和草坪草高羊茅（Festucaarundinacea）为材料,在人工气候室可控制条件下,进行了盐胁迫下种子萌发和幼苗盆栽试验,用不同浓度的CaCl2（5、10、20、40、80 mmol/L）处理,研究高羊茅种子萌发和幼苗生长状况,重点研究了矿质元素Na^＋、K^＋、Ca^2＋和Mg^2＋在植株地上部分和地下部分的分布。研究表明：适当浓度的外源CaCl2浸种处理能缓解高羊茅种子受到的盐胁迫伤害,促使种子提前萌发,20 mmol/L CaCl2浸种处理能显著提高种子萌发率,但高浓度（80 mmol/L）的外源钙处理对高羊茅种子萌发不利;适当浓度的CaCl2处理能促进幼苗地上部分生长,降低高羊茅根冠比、稳定植物细胞膜、维持离子平衡、提高植物耐盐性,但是高浓度（80 mmol/L）CaCl2处理会对植物幼苗生长造成伤害。     

化感物质阿魏酸对小麦幼苗内源激素水平的影响

研究了化感物质阿魏酸（FA）在0.25mmol/L、2.50mmol/L浓度下对小麦幼苗内源激素-生长素（IAA）、赤霉素（GA）、细胞分裂素（ZR）和脱落酸（ABA）含量的影响,并测定了培养液中剩余阿魏酸量,结果表明,在2.50mmol/L处理的培养液中剩余阿魏酸量在3-10d内下降最快,14d后98%以上阿魏酸消失。不同浓度阿魏酸对小麦幼苗中4种内源激素的含量表现为0.25mmol/L与对照差别不大,2.50mmol/L样品中的含量均呈上升趋势,但生长素、赤霉素、细胞分裂素在小麦体内大量积累,反而抑制了小麦幼苗的生长,同时诱导脱落酸含量升高。     

外施氯对油菜幼苗生长和光合特征影响的研究

采用盆栽砂培试验,研究了不同浓度氯离子（Cl-）处理对油菜（Brassica napus L.）幼苗干物质积累速率（DMAR）、根冠比（R/S）、叶绿素（Chl）含量、氯离子含量（Cl-）、净光合速率（Pn）、气孔导度（Gs）、细胞间CO2浓度（Ci）、蒸腾速率（Tr）、水分利用效率（WUE）、气孔限制值（Ls）等的影响。结果表明:25～100 mmol/L Cl- 处理9 d和18 d,油菜幼苗植株DMAR均上升,均在50 mmol/L Cl- 处理时达到最大值;不同浓度Cl- 处理9 d,Chl含量有先上升后下降的趋势,在100 mmol/L Cl- 处理时达到最大值,处理18 d,Chl含量依次下降。Cl- 处理能显著提高叶片中的Cl- 含量。除了在处理18 d后的Ci外,25～100 mmol/L Cl- 处理下,油菜叶片均能维持较高的Pn、Gs、Ci和Tr,200 mmol/L Cl- 处理9 d和18 d,油菜叶片Pn、Gs、Ci和Tr均显著下降。随着Cl- 浓度的增加,WUE呈现先降后升,在9 d处理后,随着Cl- 浓度的增加,油菜Ls也呈现先升后降,而在18 d处理后,随着Cl- 浓度的增加,Ls逐渐显著上升。上述结果表明,外施低量氯（Cl- 25~100 mmol/L）显著提高或者维持油菜幼苗的光合作用和蒸腾作用,促进油菜幼苗的生长;而高氯（200 mmol/L Cl-）条件下显著降低其光合作用和蒸腾作用,抑制其生长,且抑制油菜幼苗光合的主要是气孔因素。相关性分析还表明,植株DMAR、Pn、Ci、Tr、Gs之间均有显著的正相关性,而Pn与WUE之间存在极显著的负相关。     

SAHA对水牛卵母细胞体外成熟及胚胎发育潜能的影响

卵母细胞体外成熟过程中组蛋白修饰发生了剧烈的变化,其表达模式的改变对卵母细胞的成熟乃至后续胚胎的发育有着至关重要的作用.去乙酰化酶抑制剂-伏立诺他(suberoylanilide hydroxamic acid,SAHA)作为新型抗癌药物,是组蛋白去乙酰化酶的潜在抑制剂,在体内和体外抑制多种类型肿瘤细胞生长并促进其分化和凋亡.为探讨组蛋白去SAHA对水牛Bubalus bubalus)卵母细胞体外成熟和胚胎体外发育潜能的影响,本研究比较了不同浓度(0,2,5,10,20和40 nmol/L)SAHA处理成熟期的水牛卵母细胞对其成熟率(第一极体排出率)、受精卵分裂率、囊胚率和囊胚总细胞数的影响.结果表明,10 nmol/L SAHA处理组成熟率、卵裂率、囊胚率显著高于对照组((77.07±1.79)％和(62.3士2.08)％,(86.81±1.93)％和(74.86±2.07)％,(27.56±2.86)％和(24.23±1.74)％,P＜0.05).随着浓度增加,各处理组囊胚总细胞数有提高的趋势,但组间差异不显著(141±10,151±13,165±17,170±14,147±20,185士22,P＞0.0S).qRT-PCR检测结果显示,SAHA对水牛卵母细胞成熟过程的处理,均显著下调了cAMP反应元件结合蛋白(cAMP responsive element binding protein,CREB)结合蛋白基因CBP、组蛋白乙酰转移酶1基因(histone acetyltransferases 1,HAT1)、组蛋白去乙酰化酶1基因(histone deacetylase 1,HDAC1)在MⅡ期卵母细胞中的表达,P300则有所上调.实验结果表明,组蛋白去乙酰化酶抑制剂SAHA处理是一种能够提高水牛卵母细胞体外成熟效率促进胚胎发育的有效途径之一,该研究结果可为今后研究转基因克隆胚胎发育相关基因调控机理提供了理论基础.     

家蚕Bm30Kc6蛋白对过氧化氢诱导的家蚕细胞凋亡的抑制作用

30K蛋白是一类家蚕(Bombyx mori)血淋巴中具有最强抗细胞凋亡活性的蛋白,家蚕Bm30Kc6蛋白作为30K蛋白家族的成员之一,也具有较强的抗细胞凋亡作用,但其抗细胞凋亡的作用机制还不十分清楚。本研究将本实验室成功构建的重组病毒Bacmid-Bm30Kc6接种家蚕BmN细胞大量表达后,利用Ni-NTA蛋白亲和层析柱纯化重组蛋白Bm30Kc6。SDS-PAGE和Westernblot检测结果显示纯化蛋白的纯度较高。然后利用不同浓度(0.1、1、5和10mmol/L)的H2O2处理家蚕BmN细胞,诱导细胞发生凋亡,结果表明,在培养基中加入终浓度为5mmol/LH2O2孵育4h后即可成功诱导BmN细胞凋亡。在上述建立的H2O2诱导的家蚕BmN细胞凋亡体外损伤模型的基础上,分析了Bm30Kc6蛋白的抗细胞凋亡的活性及作用机制。首先利用CelldeathDetection ELISA试剂盒检测了细胞内的DNA片段化程度,检测结果表明,Bm30Kc6蛋白(终浓度5μg/mL)可明显降低H2O2诱导的家蚕BmN细胞内的DNA片段化程度。然后利用Cellproliferation ELISA试剂盒检测了细胞的增殖情况,结果表明,Bm30Kc6蛋白可以显著增强家蚕BmN细胞的活力。进一步利用8-isoprostane EIA试剂盒检测细胞内氧化应激标志物8-isoprostane的浓度变化,结果显示,家蚕Bm30Kc6蛋白可以显著降低胞内8-isoprostane的浓度。此外,Western blot分析结果显示,Bm30Kc6蛋白可显著抑制家蚕BmN细胞中细胞色素c从线粒体中释放进入细胞质。Bm30Kc6蛋白一方面可以通过降低BmN细胞内的氧化应激水平从而起到抑制细胞凋亡的作用;另一方面,Bm30Kc6蛋白也可以通过阻断H2O2诱导激活的线粒体通路来抑制细胞发生凋亡。本研究将为进一步深入研究家蚕Bm30Kc6蛋白的抗凋亡机制提供基础资料。     

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.     

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,     

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.