Effects of Brief Summer or Winter Fasting on the Muscle Quality of Cultured Pacific Bluefin Tuna (Thunnus orientalis)

The effects of fasting on the quality of the dorsal and ventral ordinary muscles from cultured Pacific bluefin tuna (Thunnus orientalis) during chilled storage were investigated. Tuna were subjected to fasting for 2 days in the summer or 6 days in the winter prior to harvesting. The breaking strength of the dorsal ordinary muscle sampled in the summer increased until 24 h and then decreased. There were no significant differences in the lipid and glycogen content of the ordinary muscle after 9 h of storage between the controls and either fasting group. The pH of the ordinary muscle subjected to summer and winter fasting was higher than in the controls after 24–48 h of storage. However, the relationship between the pH and glycogen content was unclear. The metmyoglobin content during chilled storage was lower in the ordinary muscles from either fasting group than in the controls. In conclusion, fasting for 6 days in the winter improved the color stability of the ordinary muscle without a decline in its lipid content.     

蓝藻爆发机理研究进展

湖泊富营养化依然是我国目前以及今后相当长一段时期内的重大水环境问题.研究蓝藻水华的形成机制,具有重要的生态和环境意义.对近20年来国内外对蓝藻的研究状况做一个总结,提出自己的一些看法.     

环鄱阳湖地区浅层地下水化学特征及成因分析

[目的]分析环鄱阳湖地区浅层地下水化学特征及成因。[方法]于2010年对环鄱阳湖地区7个县市的地下水质状况进行调查,从矿化度、硬度、水化学类型等方面对鄱阳湖区域不同地区浅层地下水质状况进行分析对比,揭示区域浅层地下水质现状及其变化特征与原因。[结果]环鄱阳湖地区地下水质指标除pH外均较好,均属Ⅰ类水质标准;其中南昌市矿化度、硬度、电导率、Na+、K+、Ca2+、Mg2+、Cl-、HCO3-为最高值,都昌县pH和SO42-为最高值,鄱阳县Mg2+和pH为最低值,永修县硬度、K+、Ca2+、SO42-、Cl-为最低值,进贤县Na+、矿化度和电导率为最低值。江西整体经济发展水平不高是环鄱阳湖地区地下水质较好的主要原因;南昌市地下水多项水质指标最大,甚至趋于Ⅱ类水质标准,是由于经济发展水平较高,人类活动起决定性作用。[结论]该研究为区域浅层地下水管理对策提供依据。     

种植密度和施氮水平对华南8号木薯产量形成的影响

探讨不同种植密度和施氮水平条件下华南8号木薯干物质积累、分配的规律及其对产量形成的影响。结果表明,低密度低施氮水平处理的产量显著高于高密度高施氮水平处理;低密度低施氮水平处理的单条薯重显著高于高密度高施氮水平处理,并且交互作用显著;低密度和低施氮水平处理虽然前期干物质生产速率较低,但后期干物质生产速率及其向块根的分配比例明显高于高密度和高施氮水平。     

脱落酸浸种提高萌发期水稻种子对涝渍胁迫的抗性研究

[目的]探究脱落酸(ABA)浸种对涝渍胁迫条件下水稻种子萌发及幼苗生长的影响,为农业生产提供借鉴。[方法]分别用蒸馏水和0.1μmol/LABA溶液浸种24 h,正常催芽萌发至胚根长2～5 mm,涝渍处理72 h,测定水稻种子的出苗率及各项形态指标。[结果]与涝渍对照相比,ABA浸种处理的出苗率、根长、株高、干重、相对活力指数分别增加了38.7%、23.6%、13.3%、37.8%和34.8%。[结论]ABA处理可显著提高涝渍条件下水稻种子的出苗率、秧苗素质及种子相对活力指数。     

钾营养对莲藕产量形成和氮磷钾养分累积分配的影响

【目的】研究钾营养对莲藕产量形成及氮磷钾养分积累与分配的影响。【方法】采用盆栽试验,设置不施钾（-K）和施钾（+K）处理进行全生育期试验。【结果】莲藕移栽76 d后,+K处理叶片和叶柄干物质累积量明显高于-K处理,并均在97 d膨大茎成型后逐渐降低;膨大茎干物质累积速率和累积量在早期为+K处理低于-K处理,97 d后+K处理的干物质累积速率明显加快,其累积量于139 d明显高于-K处理,160 d不同处理膨大茎干物质累积量趋于稳定,+K处理为1 204 g/株,比-K处理高19.7%。在97—160 d产量形成关键期,膨大茎中氮、磷和钾的累积量,+K处理比-K处理分别高32.8%、10.3%和74.2%,其中来自其它器官转移的氮、磷和钾,+K处理比-K处理分别高1.20、0.12和1.26 g/株,来自根系直接从土壤中吸收转运的氮、磷和钾,前者比后者高2.16、0.04和5.70 g/株。莲藕氮、磷、钾累积总量之比-K处理为1﹕0.14﹕0.90,+K处理为1﹕0.13﹕1.31。【结论】钾营养促进莲藕干物质生产和累积、促进根系对养分的吸收并提高莲藕各器官尤其是叶柄中钾的含量,在生育后期促进干物质和养分从叶片等器官转移并贮存到膨大茎中并最终增产。     

三峡库区某滑坡稳定性分析及工程治理

在研究了三峡库区某滑坡的工程地质条件及滑坡体特征的基础上,分析了该滑坡成因机制和失稳因素。考虑到未来三峡蓄水位的变化,结合不同工况对该滑坡进行了稳定性计算,针对计算结果,提出并设计了采用抗滑桩支挡与监测工程相结合的综合工程治理方案。     

Proton toxicity interferes with the screening of common bean (Phaseolus vulgaris L.) genotypes for aluminium resistance in nutrient solution

Common bean (Phaseolus vulgaris L.) proved to be very sensitive of low pH (4.3), with large genotypic differences in proton sensitivity. Therefore, proton toxicity did not allow the screening of common bean genotypes for aluminium (Al) resistance using the established protocol for maize (0.5 mM CaCl₂, 8 μM H₃BO₃, pH 4.3). Increasing the pH to 4.5, the Ca²⁺ concentration to 5 mM, and addition of 0.5 mM KCl fully prevented proton toxicity in 28 tested genotypes and allowed to identify differences in Al resistance using the inhibition of root elongation by 20 μM Al supply for 36 h as parameter of Al injury. As in maize, Al treatment induced callose formation in root apices of common bean. Aluminium‐induced callose formation well reflected the effect of Ca supply on Al sensitivity as revealed by root‐growth inhibition. Aluminum‐induced callose formation in root apices of 28 bean genotypes differing in Al resistance after 36 h Al treatment was positively correlated to Al‐induced inhibition of root elongation and Al contents in the root apices. However, the relationship was less close than previously reported for maize. Also, after 12 h Al treatment, callose formation and Al contents in root apices did not reflect differences in Al resistance between two contrasting genotypes, indicating a different mode of the expression of Al toxicity and regulation of Al resistance in common bean than in maize.     

Time-course of dinitrogen fixation of promiscuous soybean cultivars measured by the isotope dilution method

 Soybean cultivars capable of nodulating with indigenous Bradyrhizobium spp. have been developed by the International Institute of Tropical Agriculture (IITA) and national programs in Africa in order to avoid artificial inoculation by resource-poor farmers in Africa. The current selection procedure for enhanced N₂ fixation is based on an assessment of nodule formation which does not directly quantify the proportions of crop N derived from the atmosphere. We have monitored N accumulation patterns and N₂ fixation in nine promiscuous soybean cultivars with different maturity periods, using the ¹⁵N dilution technique. Nodule development generally peaked at the early podfill stage for all cultivars except Tgx 1519-1D and Tgx 1447-2D in which it continued to increase. The proportion of crop N derived from fixation (%NDFA) ranged between 51% and 67%, 77% and 84%, and 66% and 73% at full bloom, early podfill, and physiological maturity stages, respectively. Total N accumulation increased in all soybean genotypes with increasing plant age. Significant correlations (P<0.001) were established between nodule weight and %NDFA, even though this did not explain the relationship between nodule development and N₂ fixation in cultivars such as Tgx 1519-1D. Promiscuous soybean cultivars retained between 10% and 19% of total N accumulated at the final harvest, in belowground biomass. Our results indicated that these soybean cultivars can derive substantial proportions of plant N from N₂ fixation in soils where compatible indigenous bradyrhizobia populations are adequate and effective. Also, we have substantiated the claims that qualitative nodulation parameters currently used to select varieties with a high N₂ fixation capacity need to be validated with other measurements of N₂ fixation. Received: 5 November 1998     

不同CO2浓度对玉米秸秆分解期间土壤腐殖质形成的影响

以往人们较多的研究了土壤有机碳与温室气体的源、汇关系问题,却很少研究温室气体对土壤有机碳本身分解转化和各组分性质的影响。为了探讨CO2浓度升高对腐殖物质形成转化的作用,本文通过室内人为高浓度CO2的培养试验,用腐殖质组成修改法研究了玉米秸秆分解期间（1~180d）土壤总有机碳（TOC）、水溶性物质（WSS）、碱提取腐殖物质（HE）、胡敏酸（HA）和胡敏素（HM）数量的动态变化规律及不同CO2浓度对有机碳各组分形成与转化的影响。结果表明：玉米秸秆分解期间,“新形成”的净TOC逐渐降低,净HE表现为先增加而后下降的趋势,HM的绝对数量逐渐下降。可提取腐殖物质中HA的比例（PQ）先增加后下降,最终趋于平稳,说明最初富里酸（FA）的形成速度大于HA,随培养时间的延长,FA和HA经历了一段相互转化的过程,最终达到动态平衡。30%CO2浓度（V/V）处理的TOC、WSS、HE和HM数量明显高于3%CO2浓度处理和正常CO2浓度（0.0375%）处理,其中WSS和HM反应更为敏感。但3%CO2浓度处理与正常CO2浓度处理的差异不明显。可提取腐殖物质的PQ的顺序是30%CO2浓度处理〉3%CO2浓度处理〉正常CO2浓度处理,说明CO2浓度增加更有利于FA而不利于HA的形成和稳定。