Phosphorus Forms and Availability Assessed by 31P‐NMR in Successively Cropped Soil

Abstract

Soils under no‐tillage gradually increase in organic matter and phosphorus (P) content from the top layer. Because of lack of knowledge about the organic phosphorus fraction contribution to plant nutrition, this research was conducted to estimate the availability of phosphorus fractions to plants. Soil samples of a very clayey Rhodic Hapludox that received 0, 156 and 312 kg P ha^?1 were submitted to 15 successive crops in pots without replacing P extracted by plants. ³¹P nuclear magnetic resonance analysis was performed to detect P fractions before cultivation and after the sixth, ninth and fifteenth crops. Inorganic phosphorus was the unique P fraction acting as P source to plants in soils with previous P addition. Contribution of organic P was observed only when inorganic P content was extremely low, with plants showing severe P stress. Contribution of organic P was not enough to supply the required P for normal plant growth.     

论农民合作组织与市场农业发展

一家一户的家庭经营有其自身的弱点，难以抵御“两个风险”，发展农村合作组织是提高农民组织化程度，增强农民抗御“两个风险”能力，加快农业结构调整，实现农民收入稳定增长的客观要求和必然选择。目前，我国农村合作组织中仍然存在着资产不清、产权不明、管理混乱、管理队伍素质较低等一系列问题。新形势下我国农村合作组织发展需要在转变观念的基础上，因地制宜的采取切实有效的措施。     

Mechanism of systemic inflammatory response syndrome induced by EC DNA

AIM: To investigate whether the bacterial DNA participates in SIRS and its possible mechanism. METHODS: Escherichia coli genomic DNA (EC DNA) was extracted and purified from Escherichia coli 25922 by alkaline lysis method. Mortality of mice challenged with EC DNA and the changes of TNF-α and IL-6 in rat serum were observed. ANA-1 cells were cultured in vitro, after the cells were stimulated by different concentrations of EC DNA and LPS, the level of TNF-α and IL-6 in supernatant were tested. Meanwhile,expression of TLR9 and TLR4 on cell surface was measured. Activation of NF-JB was also observed. RESULTS: The lethal effect of EC DNA on mice with an obvious dose-effect relationship was observed. The death happened within 24 hours. Calf thymus DNA and DNase I-treated EC DNA did not lead to mice to die. The changes of serum TNF-α and IL-6 in rats induced by EC DNA and LPS were similar, but TNF-α peak level of EC DNA group appeared 1 hour earlier than that of LPS group. In vitro, large amount of TNF-α and IL-6 were released from ANA-1 cells stimulated by EC DNA. High expression of TLR9 and TLR4 was observed on surfaces of THP-1 cells. In particularly, LPS induced strong activation of NFκB. The results suggested other pathway possibly took part in the signal transduction inducea by EC DNA. CONCLUSION: EC DNA has the abilities to lead to death of mice, andinduces serum TNF- αand IL- 6 level to increase in rats and ANA- 1 cells to release cytokines in vitro. High expression of TLR9 and TLR4, strong activation of NF- κB may be its importantmolecular mechanism, but other pathway probably exists to play an important role.     

邓小平集体主义道德思想的探析

本文阐述了邓小平的集体主义道德思想:肯定人民群众追求正当个人物质利益的合理性;把国家、集体、个人三者利益结合起来;发扬乐于奉献、自我牺牲精神;反对极端个人主义、地方保护主义等消极腐朽思想;实现共同富裕的最终价值目标。     

A comparison of the response of different citrus fruit cultivars to storage temperature

A comparison was made of the response to storage temperatures (0–17°C) of grapefruit ‘Shamouti’ and ‘Valencia’ oranges, and lemon fruit. There was no chilling injury (CI) and the incidence of rot was relatively low at 12°C or higher for all cultivars. At low storage temperatures, however, pitting and subsequent rot development in grapefruit and in ‘Shamouti’ and ‘Valencia’ oranges were highest at 6°C, while in lemon the incidence of these disorders rose with the decrease in storage temperature, and was highest at 2°C. Grapefruit and ‘Shamouti’ oranges exhibited the highest susceptibility to CI, lemon showed an intermediate susceptibility, and ‘Valencia’ orange a very low one. In grapefruit, severe peel pittings that developed in cold storage were covered by mold rots during cold storage and shelf-life, but in ‘Valencia’ and particularly in ‘Shamouti’ oranges the incidence of decay during cold storage was low. During shelf-life, a pronounced CI-induced increase in the incidence of mold rots was evident. This breakdown during shelf-life may be associated with microscopic peel injuries which are formed during cold storage and covered by mold rots during shelf-life. Increased susceptibility of the cultivar to CI could be correlated with an increase in ethanol content at low temperatures.     

新版"中国期刊网"专题全文数据库的性能与评价

中国期刊网最近发布了专题全文数据库 3 5版 ,相对于以前的版本 ,新版专题全文数据库不论从界面还是性能上都有很大的改进。本文主要介绍了中国期刊网专题全文数据库的性能 ,分析了其存在的不足 ,并针对不足提出了改进建议     

低温预处理对大蒜根尖细胞有丝分裂的影响

以大蒜根尖为材料，用常规压片方法制备染色体标本，研究不同低温预处理时间对根尖细胞有丝分裂的影响。结果表明：低温预处理12—42h能提高有丝分裂指数和中期分裂指数；6h和48h低温预处理会降低有丝分裂指数和中期分裂指数；低温预处理24～30h有利于根尖细胞的有丝分裂。     

试论项目制在公共图书馆读者活动中的运作——兼“寻找城市记忆”活动案例分析

公共图书馆读者活动一直采用部门负责制模式,这种模式以部门为核心,是直线职能性组织结构,对新形势下操作流程复杂,组织灵活、需多个部门合力参与、多种社会力量合作的活动来说,在整合优势资源方面存在一定的局限性。而项目制作为一种先进的管理方式,既有直线职能性组织结构的组织性又有横向联合的灵活性,运用于图书馆读者活动有一定的积极意义。本文以湖南图书馆开展的＂寻找城市记忆＂为例,探讨了项目制模式在公共图书馆读者活动中的运作。     

提升我国农产品加工业的途径

改革开放30年来，我国农产品加工业取得了长足发展．但与国外发达国家相比还存在较大差距。提升我国农产品加工业的途径主要有：制定并落实扶持政策：以食品精深加工作为重点，以龙头企业为主干；优化产品结构，大力发展主导产业，优先发展品牌企业；加大技术投入，加快技术创新，提升自主创新能力；按照国际标准完善农产品加工质量标准体系；加强农产品原料生产基地建设；降低农产品加工企业的税负；构建营销体系，发挥协会作用，提升服务水平等。     

植被培育抗旱分析

随着气候的演变,植被培育面临严峻的干旱缺水形势。为进一步增强抗旱的主动性和有效性,主要以作物栽培为背景,重点论述了有关抗旱的基础问题。通过分析干旱的特点、表现形式、区域差异、相对性、降水和灌溉水的利用状况、应对干旱的策略等,以明晰抗旱的依据。认为土壤水分亏缺是干旱的主要表征;土壤干旱的滞后性,也即和大气干旱的非同步性,是抗旱的一个重要依据。通过对抗旱途径的讨论,细分出避旱、御旱二个方面,并且认为御旱应当是正常的生产方式。抗旱具有高效、节约用水的特征,直接抗旱和间接抗旱都是必要的。最后,还补充阐述了水文干旱、降水资源化利用的意义。