荸荠试管苗的快速繁殖

以四塘荸荠和郴州荸荠两个荸荠品种球茎顶芽作为外植体，通过正交设计方法，对基本培养基、细胞分裂素、生长素类进行了优化筛选试验，并研究不同的蔗糖浓度和不同6-BA浓度对荸荠试管苗增殖的影响。结果表明：四塘荸荠和郴州荸荠增殖的最佳培养基为MS＋6-BA3．0mg／L＋IBA0．1mg／L。四塘荸荠以蔗糖浓度6％为最佳，而郴州荸荠以蔗糖浓度8％效果为最佳。说明两个品种在培养基选择上存在差异。     

氮磷钾肥配施对荸荠产量和品质的影响

通过试验表明：（１）氮肥用量与荸荠产量呈一元二次方程相关，适量地施用磷钾肥对荸荠有明显的增产效果，氮磷钾合理施用比例：云会点为（１３．３－１６）：１：３，崇贤点为１３．３：２：３；（２）氮磷钾合理配施能提高荸荠糖分含量和调节荸荠淀粉含量，改善荸荠品质。     

荸荠试管结球茎的试验研究

以两个荸荠品种（四塘荸荠和郴州荸荠）的试管苗为试验材料．进行不同因素对试管苗结球茎的试验。结果表明：（1）不同蔗糖浓度对荸荠试管结球茎有显著影响，当蔗糖浓度为60g／L时，两个品种的结球茎个数和平均鲜重都达到了最大值；（2）6-BA对荸荠试管结球茎的效果明显．其最佳浓度为3mg／L；（3）温度对荸荠试管结球茎也有重要影响，日夜温差大对试管结球茎效果好。     

水稻白叶枯病的综合防治方法

水稻白叶枯病是由细菌引起的水稻病害。又称白叶瘟、地火烧、茅草瘟等。水稻白叶枯病于1884年首先在日本发现．目前已遍及世界各主要产稻区。此病在黑龙江省属检疫性病害．因此．不要盲目从水稻白叶枯病病区引种。水稻受害后，叶片枯萎，严重妨碍光合作用，致使不实粒增加．一般减产20％-30％,严重的可减产50％。     

广西淡水鱼类寄生指环虫（单殖纲：指环虫科）一新种记述

１９９０～１９９３年对广西淡水鱼类进行了寄生蠕虫区系调查，发现寄生于南方拟（Ｐｓｅｕｄｏｈｅｍｉｃｕｌｔｅｒｄｉｓｐａｒ）鱼上指环虫一新种，定名为右江指环虫Ｄａｃｔｙｌｏｇｙｒｕｓｙｏｕｊｉａｎｇｅｎｓｉｓｓｐ．ｎｏｖ．。此虫种以其辅助片量度较小，交接管为基部轻微弧形弯曲的直形锥管，支持器呈中部具套环的＂Ｖ＂字形，区别于与之相近似的Ｄ．ｌａｔｉｔｕｂａＧｕｓｓｅｖ１９５５及本属其他已知种。     

罐制过程中荸荠质构变化及其与淀粉特性的关系

该文通过比较荸荠罐制过程不同阶段的质地结构，研究了荸荠罐制过程中质构变化的规律及其与含水率的关系，比较了预煮、排气和杀菌三个受热过程后的质构，结果表明荸荠质构中弹性性质(脆度、硬度和黏着性)和塑性性质(凝聚性和回复性)在受热后有不同的变化，弹性性质参数值在排气过程中有所回升，塑性性质参数值则在整个过程中全部呈下降趋势；含水率与黏着性呈极显著的负相关，与凝聚性和回复性呈显著正相关。同时对荸荠质构变化与淀粉特性的相关性做了分析，探讨通过改变淀粉特性以达到较好质构的可行性。研究发现荸荠淀粉的膨胀力(Swell Power，SP)、淀粉凝胶质构和淀粉快速黏度分析(Rapid Visco Analysis，RVA)谱中的崩解值与荸荠的各项质构参数的相关性均达到显著或极显著水平。可根据荸荠质构特性的变化规律，通过控制不同的受热过程，尤其是预煮，使之得到具有较好质构的产品。另外，改变淀粉特性也可改善产品质构。     

荸荠收获机弹簧辊式泥果分离装置研制

针对荸荠收获泥果分离难、果实损伤率高的问题，根据旱地环境下荸荠采收作业需求，该研究提出一种由正反旋弹簧并排布置的荸荠收获机弹簧辊式泥果分离装置。通过对荸荠与弹簧辊的相对运动过程动力学分析，确定了影响荸荠收获泥果分离的关键因素为弹簧外径、螺距、相邻弹簧间距、高度差及弹簧转速、线径、作业速度。利用EDEM软件建立泥果混合物离散元模型，对弹簧辊结构参数与工作参数进行单因素试验，分析各因素对泥果分离效果的影响。以荸荠筛分率和土壤筛分率为指标进行二次回归正交试验，得到弹簧辊最佳参数组合为外径100 mm、螺距30 mm、间距9 mm、转速420 r/min，该参数组合下荸荠筛分率为80.00%，土壤筛分率为80.69%。进行仿真验证试验，对比试验结果与模型预测值，荸荠筛分率平均相对误差为2.09%，土壤筛分率平均相对误差为2.42%。以明果率、伤果率、破皮率、挖净率为指标开展模拟采挖试验，分析不同线径弹簧辊的泥果分离能力，确定12 mm线径弹簧兼具较好的振动筛分性能和较低的损伤率。通过实际收获试验测得作业速度0.21 m/s，作业效率0.19 m² /s，碎土率75.61%，明果率82.42%，伤果率14.73%，破皮率7.01%。研究结果可为荸荠收获机研制和优化改进提供参考。     

“荸荠杆枯病病原、发病规律与防治研究”项目通过技术成果鉴定

由广西大学农学院赖传雅教授主持、广西区科技厅下达的“荸荠杆枯病病原、发病规律与防治研究”项目,于1998年6月16日通过了由广西区科技厅组织的技术成果鉴定。荸荠又名马蹄,是我国重要的水生经济作物之一,广西各地都有种植,尤以荔浦、贺州、平乐、桂林等地所产的马蹄汁多、味甜,品质上乘,食用和经济价值较高。近年来荸荠的大面积种植,已成为乡(镇)脱贫致富、增加财税来源的支柱产业。然而,随着种植面积的扩大,荸荠杆枯病已严重地影响了马蹄的产量和商品率的提高。为了有效地控制此病的发生,多年来,该课题组的研究人员,对病原菌的鉴定、生…     

荸荠高产种植技术要点

随着我国荸荠种植面积不断扩大,人们对于荸荠种植效益的重视程度不断提升。但是当前,在荸荠种植过程中还存在一些问题,这就需要结合种植情况、施肥情况、病虫害防治情况,采取有效的管理技术,提升荸荠的种植效益。基于此,分析荸荠高产种植技术要点。     

荸荠贮藏期真菌性病害种类调查鉴定初报

真菌是荸荠(Eleocharis dulcis)贮藏期间腐烂病的重要病原，严重影响荸荠的品质和产量，造成巨大的经济损失。为了查明致病真菌种类，作者在2001年，分别从荔浦、合浦、南宁等地收购站，采集荸荠病害标本。经分离、培养、致病力测定和形态特征观察，获得三种病原：A-8菌株为根串珠霉(Thielaviopsis sp.)、A—l3菌株为根霉(Rhizopus sp)、A—3菌株为尖孢镰刀菌(Fusarium oxysporum Schlecht）。     

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,     

Assessing the effectiveness of conservation measures: Resolving the “wicked” problem of the Steller sea lion

“Wicked” problems are those that are complex and that change when solutions are applied. Many conflicts in conservation fall into this category. The study approached the problem of how to constrain the apparent wickedness of a problem in the conservation management of a species by using simple empirical indicators to carry out iterative assessment of the risk to a population and to document how this risk evolves in relation to the addition of new data and the implementation of management actions. Effects of high levels of uncertainty within data and also concerning population structure were examined through stochastic simulation and by exploration of scenarios. Historical trends in the example used, the Steller sea lion, showed rapid declines in abundance in some regions during the 1980s. The current total population is 130,000-150,000 Steller sea lions through Alaska and British Columbia and this number has been stable since about 1990 in spite of regional differences in population dynamics. Regional differences in the sequence of changes in the number of pups and non-pups, suggested that an internal re-distribution of juveniles could have happened between 1980 and 1990. Current productivity also appears close to the long-term mean. Stochastic population projection using various scenarios showed that, based upon this history, the risk of extinction for the population has declined and is below reasonable thresholds for considering the population to be endangered. The trends in risk suggest that management actions taken since 1990 have probably been effective. Consequently, the conservation management objectives for the Steller sea lion are probably being met. The approach provides a mechanism, based upon experience and scenario analysis, for exploring future policy options and may help to constrain the debate amongst stakeholders about the cost-benefit trade-offs associated with different options.     

Soil-profile distribution of primary and secondary plant-available nutrients under conventional and no tillage

Nutrient distributions under no tillage (NT) compared with conventional disk-and-bed tillage (CT) management in the warm, humid region of the southeastern USA need to be assessed so that future placement, quantity, and type of fertilizers can be altered, if necessary, to efficiently match crop demands. We determined soil-profile distributions of pH, N, P, S, K, Ca, Mg, Na, Zn, Fe, Mn, and Cu to a depth of 0.9 m at the end of 8.5 years of continuous CT and NT management on a Weswood silty clay loam (fine, mixed, thermic Fluventic Ustochrept) in southcentral Texas. Most dramatic changes occurred within the 0–0.05 m depth, where soil under NT had lower pH, Fe, and Cu than under CT, but greater P, K, Zn, and Mn. Greater P and K under NT than under CT also occurred below the till-zone (0.15–0.3 m). At a depth of 0–0.3 m, soil under NT contained greater amounts of extractable P, K, Zn, Fe, Mn, and Cu than under CT. Nitrogen fertilization had little effect on nutrient distributions, except resulting in greater extractable K at 0–0.05 m and greater nitrate at 0–0.15 m. Few changes in soil-profile distributions were observed for extractable S, Ca, Mg, and Na. Long-term continuous use of NT on this fine-textured, high-fertility (except for N) soil had no apparent adverse effects on nutrient distributions relative to CT, but enhanced conservation and availability of P, K, Zn, Fe, Mn, and Cu near the soil surface where crop roots proliferate.     

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.     

Enhanced establishment and growth of giant cardon cactus in an eroded field in the Sonoran Desert using native legume trees as nurse plants aided by plant growth-promoting microorganisms and compost

To evaluate the feasibility of long-term desert reforestation technology of mixed vegetation, cardon cactus (Pachycereus pringlei) seedlings from indoor and outdoor nurseries were planted in the field adjacent to one seedling of potential legume nurse trees: mesquite amargo (Prosopis articulata), yellow palo verde (Parkinsonia microphylla), and blue palo verde (Parkinsonia florida). Some of the planting holes were also supplemented with common dairy compost. Additionally, the combinations of legume tree–cactus were inoculated with either a consortium of desert arbuscular mycorrhizal (AM) fungi, plant growth promoting bacteria (PGPB; the diazotroph Azospirillum brasilense Cd, and the phosphate solubilizer Paenibacillus sp.), or a mixture of all. The field experiments were evaluated periodically during 30 months for survival and growth. Cardons reared in an outdoor screen house survived better in the field than those reared in a controlled growth chamber and hardened later outdoors. Association with any legume nurse tree increased survival and enhanced growth of untreated cardons. For cardons growing alone, application of either compost, AM fungi, and all the treatments combined increased survival. For these plants, no treatment affected plant growth during the first 3 months after transplanting. Later, all treatments, except for AM fungi, enhanced plant growth. However, only 2 years after transplanting the enhanced growth effect of AM fungi was also significant. In the presence of the legume nurse trees, transient positive effects on cardon growth were recorded. General evaluation after 30 months of cultivation showed that the treatments positively affected cardon growth when growing alone or in combination only with mesquite amargo but not with the other two legume trees. This study proposes that young legume trees have the capacity to enhance survival and growth of cardon cactus, depending on the legume cactus combination. Additional treatments such as compost or PGPB can either amplify the effect or else attenuate it.     

Karyotypic and genome size variation in Cajanus cajan (L.) Millsp. (pigeonpea) and some wild relatives

Detailed karyotypes and 4C DNA amounts have been studied in five cultivars of Cajanus cajan and 20 species belonging to Cajanus, Rhynchosia, Dunbaria, Flemingia and Paracalyx. C. cajan shows intraspecific variability and its karyotype is most similar to that of C. cajanifolius (sect. Cajanus) in the morphology and number of satellite chromosomes and the lack of any correlation between chromosome size within the complement and asymmetry. Karyotypes of C. lineatus and C. sericeus belonging to sect. Atylia are similar with respect to maximum r-index and the ratio of longest and shortest chromosomes in their respective complements. C. acutifolius (sect. Frutocosa) is distinct in having a very low ratio (1.44) between the longest and the shortest chromosomes, while in C. albicans, C. goensis, C. scarabaeoides (sect. Cantharospermum) there is no chromosome pair with r-index >2.0. C. mollis and C. volubilis (sect. Volubilis) show similarity with regard to ratio between the longest and the shortest chromosomes and a distinct chromosome pair with an arm ratio of 2.7 and C. platycarpus is distinct (sect. Rhynchosoides) in having the smallest ratio (1.36) between the longest and the shortest chromosomes. 4C DNA amounts in Cajanus and Rhynchosia vary between 3.28 pg to 11.69 pg and 4.92 pg to 11.13 pg respectively, while in Dunbaria, Flemingia and Paracalyx these vary between 4.70 and 7:06 pg. In the genus Cajanus karyotypic features and 4C DNA amounts agree with the sectional classification and bring out a close relationship between C. cajan and C. cajanifolius. This is supported by studies based on seed protein patterns, isozyme analysis, trypsin and chymotrypsin inhibitor patterns, RFLP and RAPD data and crossability relationships. A clear relation between DNA amount and abnormalities effecting the extent of pairing and recombination in interspecific hybrids shows the importance of this study in developing future breeding programme involving C. cajan and its wild relatives that are of potential value.     

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.