缓控释氮肥施用技术在水稻上应用研究进展与展望

缓控释氮肥作为一种新型肥料，兼顾增产和环境友好两大特点，在提高水稻产量与氮素利用率以及缓解环境污染方面展现出了显著优势。在前人研究基础上，总结了缓控释氮肥的概念、分类、不同缓控释氮肥作用机理，及缓控释氮肥在水稻生产上形成的不同施肥技术的特征及其效果，如缓控释氮肥一次性施肥、与速效尿素混合一次性基施、不同的缓控释氮肥相互混合一次施用，以及与速效尿素分次施用的施肥技术。介绍了缓控释氮肥不同施用技术对水稻产量形成的影响，以及施用缓控释氮肥对土壤和大气环境的影响。明确缓释氮肥在水稻生产应用中的优势，进一步指出缓控释氮肥在水稻生产应用中存在的问题并且提出相关建议，为推动缓控释氮肥在水稻生产上的广泛应用提供一定的参考依据。     

我国水稻氮肥高效利用的研究进展

综述了我国水稻氮肥使用现状和存在的主要问题,从高产水稻推广应用、土壤氮背景值、施氮时期和比例以及中期晒田等方面分析了影响我国水稻氮肥利用率的可能因素,提出了通过选育氮肥利用率高的水稻品种,施用新型氮肥并改善施肥技术,氮肥与其他肥料平衡施用,使用脲酶抑制剂和硝化抑制剂,采用适时适地氮肥管理模式和水肥调控技术等方法提高水稻氮肥利用率.     

水稻高产和氮肥高效利用研究进展

实现水稻高产和氮肥的高效利用是当前水稻生产的迫切需求。本文综述了水稻氮肥的投入损失概况及氮肥利用的生理机制,介绍了提高水稻氮肥利用效率的研究进展和主要技术,讨论了氮肥利用存在的问题和今后研究的重点。     

不同施氮肥处理对水稻植株吸磷量的影响

通过水稻田间小区试验,分析不同氮肥处理对水稻磷素吸收的影响。结果表明,氮肥施入量过高会影响水稻植株对磷肥的吸收利用。不同的氮肥施用比例及追施次数对水稻吸收磷素有影响,即随着氮肥的增加,磷肥的吸收量有所提高。缓释尿素控制了氮素的释放速度,有利于调节植株吸收磷素,并且间接地提高水稻植株对磷养分的吸收利用。     

氮肥运筹对水稻镉吸收转运影响的研究进展

综述了大田生产中氮肥运筹对重金属污染土壤中水稻对镉的吸收与转运的影响,从不同形态氮肥耦合灌溉对土壤理化环境、水稻根表铁膜、水稻各器官亚细胞结构以及镉元素在植株体内转运特点的影响进行分析,并阐述了氮肥对植物镉吸收的影响机制。今后研究的侧重点应当结合复杂的环境变量条件,选择适合不同地区实际生产的水稻品种,进一步探索不同的氮肥种类和施用方式与水稻吸收富集镉之间的关系,并注重寻找调控相关过程的关键基因及其表达产物,明确镉胁迫环境中水稻产生应答的相关生理过程,进一步在生产实践中指导镉污染稻田中的肥料精确释放。     

水稻氮效率基因型差异研究

目前我国稻田氮肥施用量越来越高,导致氮肥利用率下降,引发能源浪费、环境污染和生产效益降低等问题日益严重。充分挖掘作物吸收利用氮的遗传潜力,是提高稻田氮肥利用率的重要途径之一。综述了水稻基因型间的氮效率差异及各项指标间的相互关系,同时探讨了水稻氮利用基因型差异形成的机制。     

浅谈氮肥对水稻秧苗素质及产量品质的影响

阐述了氮肥对水稻秧苗素质的影响;从氮肥与水稻群体质量、氮肥与水稻倒伏及叶片光合作用的关系等方面总结了氮肥对水稻生长发育的影响;从氮肥的施用量及运筹方式与水稻产量形成的关系等方面总结了氮肥对水稻产量的影响;综合阐述了施氮量及施氮时期对稻米品质的影响。     

氮肥用量和运筹对我国水稻产量及其构成因子影响的整合分析

【目的】合理的氮肥用量和运筹能够有效提高水稻产量和氮肥利用率。明确氮肥用量和运筹对水稻产量及其构成因子的影响可为水稻高产高效生产提供理论指导。【方法】基于119篇已发表的有关稻田氮肥管理的论文，采用整合分析(Meta-analysis)的方法量化了不同施氮量、基肥+分蘖肥、穗肥、种植区域和土壤性质等条件下氮肥管理对水稻产量及其构成因子的影响，并探究了我国各水稻主产区提高产量构成因子以获得高产的适宜措施。【结果】与不施氮肥相比，施用氮肥能够显著提高水稻实际产量(+42.2%)和理论产量(+43.1%)，有效穗数和每穗粒数分别增加了33.2%和13.5%，而结实率和千粒重分别下降了4.2%和1.6%。在不同施氮量和氮肥运筹下，水稻产量及其构成因子存在显著差异。水稻实际和理论产量在施氮量为150～200 kg/hm²时增幅最大，有效穗数和每穗粒数在施氮量为250～300 kg/hm²时增幅最大。另外，随着施氮量的增加，水稻的结实率和千粒重显著下降。基肥+分蘖肥的氮比例(基肥+分蘖肥占总施氮量的比例)为30%～50%和穗肥氮比例为10%～30%时，水...     

水稻氮肥运筹及施用模式简述

氮肥是作物增产的重要因素。介绍了国内外主要的氮肥施用方法以及近年来新型的氮肥施用技术,阐述了水稻生产中合理的氮肥运筹与氮肥利用率之间的关系,指出了前氮后移施肥技术对水稻生产的促进作用,为水稻产量和品质的提升提供了具有可参考性的意见和建议。     

两湖地区中稻产量和效益的影响因素分析——基于344个水稻种植农户的调查

基于湖南和湖北两省344个水稻种植农户的调查数据，采用柯布—道格拉斯生产函数，利用OLS模型分析方法，预估影响两湖地区水稻产量和效益的因素及其效应。结果表明：劳动力老龄化和教育水平低下对我国水稻生产存在负向影响；扩大种植规模能够显著提高水稻种植效益，但农村劳动力的大量流失迫切需要机械化程度进一步提高；水稻品种和种植方式对水稻产量无明显贡献；施肥方式对水稻产量有正效应；抽穗扬花期温度对水稻产量造成显著影响，持续高温天气不利于产量形成。建议少施化肥，增施有机肥，合理追施氮肥和磷钾肥，保证水稻生产所需养分；通过深施肥和新型肥料等途径提高肥料利用率；选用耐高温品种，适当调整播期；进一步倡导规模化和机械化种植。     

Comparative Assessment of the Efficacy of Various Nitrogen Fertilizers

Summary

The efficiency of N fertilizers is usually poor; often less than 50% of the applied N is taken up by the crop. This review focuses on various N fertilizers with respect to the significance of different N loss pathways, namely (i) ammonia volatilization, (ii) dinitrogen and nitrogen oxide emissions, and (iii) nitrate leaching. Further, the significance of biological N immobilization, ammonium fixation and, finally, the impact of nitrate vs. ammonium uptake on crop yield are also discussed. The reviewed literature shows that N fertilizers may differ markedly in their susceptibility to losses. There is, however, considerable scope to improve N efficiency of each N source by proper N management practices.     

Studies on natural repellents against potato tuber moth (Phthorimaea operculella Zeller) in country stores

Summary The effects of the leaves of five plant species, one from each of the generaAmbrosia, Anemone, Eupatorium, Eucalyptus andLantana, on potato tuber moth were investigated under indigenous storage conditions at the Central Potato Research Station, Shillong (1800 m above sea level). Their action was compared with that of a biological insecticide (spores ofBacillus thuringiensis), a chemical insecticide (carbaryl), and an untreated control. The data collected after six months storage on tuber damage, sprout damage and the rotting indicated that the leaves ofLantana aculeata provided most protection to the tubers, reducing damage from over 70% in the check to below 5%, and sprout damage from over 45% to below 3%. Next best wasEucalyptus globulus followed byB. thuringiensis. They may be used on tubers stored for table use or for seed as they had no adverse effect on germination or on the yield of a subsequent crop.     

Novel food and non-food uses for sorghum and millets

Sorghum and millets have considerable potential in foods and beverages. As they are gluten-free they are suitable for coeliacs. Sorghum is also a potentially important source of nutraceuticals such antioxidant phenolics and cholesterol-lowering waxes. Cakes, cookies, pasta, a parboiled rice-like product and snack foods have been successfully produced from sorghum and, in some cases, millets. Wheat-free sorghum or millet bread remains the main challenge. Additives such as native and pre-gelatinised starches, hydrocolloids, fat, egg and rye pentosans improve bread quality. However, specific volumes are lower than those for wheat bread or gluten-free breads based on pure starches, and in many cases, breads tend to stale faster. Lager and stout beers with sorghum are brewed commercially. Sorghum's high-starch gelatinisation temperature and low beta-amylase activity remain problems with regard to complete substitution of barley malt with sorghum malt . The role of the sorghum endosperm matrix protein and cell wall components in limiting extract is a research focus. Brewing with millets is still at an experimental stage. Sorghum could be important for bioethanol and other bio-industrial products. Bioethanol research has focused on improving the economics of the process through cultivar selection, method development for low-quality grain and pre-processing to recover valuable by-products. Potential by-products such as the kafirin prolamin proteins and the pericarp wax have potential as bioplastic films and coatings for foods, primarily due to their hydrophobicity.     

In vitro antimicrobial activity of different accessions ofSolanum commersonii Dun. from Uruguay

Summary The in vitro antimicrobial activity of extracts from accessions ofSolanum commersonii Dun. collected in the south of Uruguay was investigated against five microorganisms including the pathogenRalstonia solanacearum. A total of 30 extracts corresponding to organic and aqueous extracts were studied. Interestingly, most of the positive results for growth inhibition were againstR. solanacearum. The extracts were also analyzed for the presence of glycoalkaloids and lectins. Six of the ten aqueous extracts showed lectin presence and a wide variation in the type and amounts of glycoalkaloids, was found. Results indicate that there is no clear relationship between the antimicrobial activity against the five microorganisms screened and the presence or amounts of lectins and glycoalkaloids, traditionally regarded as possible antimicrobial metabolites in theSolanum genus, which indicates the presence of as yet unidentified antimicrobial compounds.     

Extreme resistance to infection by potato virus X in genotypes of wild tuber-bearingSolanum species

Summary Clones derived from thirty-one different accessions (nineteen of Argentine origin) belonging to eightSolanum species were screened for resistance to infection by potato virus X strain cp (PVX cp) by mechanical inoculation of plantlets that had been micropropagated in vitro. Estimates of PVX multiplication obtained by enzyme linked immunosorbent assay and slot blot nucleic acid hybridization allowed the identification of resistant clones derived from five accessions belonging toS. commersonii S. oplocense, S. sparsipilum andS. tuberosum andigena. Resistant genotypes supported PVX concentrations 5 to 15 times smaller than did the susceptible control cultivar Spunta. Graft inoculation test confirmed the presence of extreme resistance similar to that conferred by the ‘immunity’ gene X¹ (also called RX_act).     

Cyanobacteria Secondary Metabolites as Biotechnological Ingredients in Natural Anti-Aging Cosmetics: Potential to Overcome Hyperpigmentation,Loss of Skin Density and UV Radiation-Deleterious Effects

The loss of density and elasticity, the appearance of wrinkles and hyperpigmentation are among the first noticeable signs of skin aging. Beyond UV radiation and oxidative stress, matrix metalloproteinases (MMPs) assume a preponderant role in the process, since their deregulation results in the degradation of most extracellular matrix components. In this survey, four cyanobacteria strains were explored for their capacity to produce secondary metabolites with biotechnological potential for use in anti-aging formulations. Leptolyngbya boryana LEGE 15486 and Cephalothrix lacustris LEGE 15493 from freshwater ecosystems, and Leptolyngbya cf. ectocarpi LEGE 11479 and Nodosilinea nodulosa LEGE 06104 from marine habitats were sequentially extracted with acetone and water, and extracts were analyzed for their toxicity in cell lines with key roles in the skin context (HaCAT, 3T3L1, and hCMEC). The non-toxic extracts were chemically characterized in terms of proteins, carotenoids, phenols, and chlorophyll a, and their anti-aging potential was explored through their ability to scavenge the physiological free radical superoxide anion radical (O₂^•−), to reduce the activity of the MMPs elastase and hyaluronidase, to inhibit tyrosinase and thus avoid melanin production, and to block UV-B radiation (sun protection factor, SPF). Leptolyngbya species stood out for anti-aging purposes: L. boryana LEGE 15486 presented a remarkable SPF of 19 (at 200 µg/mL), being among the best species regarding O₂^•− scavenging, (IC₅₀ = 99.50 µg/mL) and also being able to inhibit tyrosinase (IC₂₅ = 784 µg/mL), proving to be promising against UV-induced skin-aging; L. ectocarpi LEGE 11479 was more efficient in inhibiting MMPs (hyaluronidase, IC₅₀ = 863 µg/mL; elastase, IC₅₀ = 391 µg/mL), thus being the choice to retard dermal density loss. Principal component analysis (PCA) of the data allowed the grouping of extracts into three groups, according to their chemical composition; the correlation of carotenoids and chlorophyll a with MMPs activity (p < 0.01), O₂^•− scavenging with phenolic compounds (p < 0.01), and phycocyanin and allophycocyanin with SPF, pointing to these compounds in particular as responsible for UV-B blockage. This original survey explores, for the first time, the biotechnological potential of these cyanobacteria strains in the field of skin aging, demonstrating the promising, innovative, and multifactorial nature of these microorganisms.     

Marine Pharmacology in 2009–2011: Marine Compounds with Antibacterial,Antidiabetic, Antifungal,Anti-Inflammatory,Antiprotozoal, Antituberculosis,and Antiviral Activities; Affecting the Immune and Nervous Systems,and other Miscellaneous Mechanisms of Action ?

The peer-reviewed marine pharmacology literature from 2009 to 2011 is presented in this review, following the format used in the 1998–2008 reviews of this series. The pharmacology of structurally-characterized compounds isolated from marine animals, algae, fungi and bacteria is discussed in a comprehensive manner. Antibacterial, antifungal, antiprotozoal, antituberculosis, and antiviral pharmacological activities were reported for 102 marine natural products. Additionally, 60 marine compounds were observed to affect the immune and nervous system as well as possess antidiabetic and anti-inflammatory effects. Finally, 68 marine metabolites were shown to interact with a variety of receptors and molecular targets, and thus will probably contribute to multiple pharmacological classes upon further mechanism of action studies. Marine pharmacology during 2009–2011 remained a global enterprise, with researchers from 35 countries, and the United States, contributing to the preclinical pharmacology of 262 marine compounds which are part of the preclinical pharmaceutical pipeline. Continued pharmacological research with marine natural products will contribute to enhance the marine pharmaceutical clinical pipeline, which in 2013 consisted of 17 marine natural products, analogs or derivatives targeting a limited number of disease categories.     

Recent Modifications of Chitosan for Adsorption Applications: A Critical and Systematic Review

Chitosan is considered to be one of the most promising and applicable materials in adsorption applications. The existence of amino and hydroxyl groups in its molecules contributes to many possible adsorption interactions between chitosan and pollutants (dyes, metals, ions, phenols, pharmaceuticals/drugs, pesticides, herbicides, etc.). These functional groups can help in establishing positions for modification. Based on the learning from previously published works in literature, researchers have achieved a modification of chitosan with a number of different functional groups. This work summarizes the published works of the last three years (2012–2014) regarding the modification reactions of chitosans (grafting, cross-linking, etc.) and their application to adsorption of different environmental pollutants (in liquid-phase).