磷胁迫下氮形态对苗期玉米氮素吸收与分配的影响

采用营养液培养的方法,比较Ca_3(PO_4)_2模拟磷胁迫条件时3种氮处理(NO_3~--N、NH_4~+-N、NO_3~--N+NH_4~+-N)对玉米氮素吸收与分配的影响。结果表明,与KH_2PO_4处理相比,磷胁迫处理时,硝态氮、铵态氮及铵硝混合营养处理的玉米整株生物量分别降低38.1%、17.4%和20.8%;与此同时,铵态氮处理的玉米植株全氮、氮素累积量、有机氮及硝态氮含量显著升高,而硝态氮处理时全氮、氮素累积量、有机氮显著降低,硝态氮含量无明显变化;此外,与硝态氮及铵硝混合处理相比,铵态氮处理的玉米叶中可溶性蛋白含量下降幅度最大,而游离氨基酸、脯氨酸含量下降幅度最小。因此,本试验中,铵态氮处理的玉米更耐磷胁迫,表现为增加了氮的吸收和积累以及增强可溶性蛋白降解为氨基酸的过程。     

淹涝胁迫和氮形态对苗期玉米营养特性的影响

采用砂培培养方法,比较研究两种水分条件和3种供氮形态处理对苗期玉米根、茎鞘、叶生物量干重及其氮、磷、钾含量及分配的影响。结果表明,非淹涝胁迫条件下铵硝态氮混合处理(AN)玉米生物量干重及氮、磷、钾累积量最高;淹涝胁迫条件下铵硝态氮混合处理(ANF)的叶片、总生物量以及硝态氮处理(NF)的根系、叶片和总生物量干重明显降低。淹涝胁迫降低3种氮形态处理叶片氮累积量,明显降低铵硝态氮混合处理和硝态氮处理植株氮、钾累积量,降低磷在铵硝态氮混合处理茎鞘、叶中的分配比例、磷在硝态氮处理根、叶中的分配比例以及钾在铵硝态氮混合处理茎鞘、叶中的分配比例。淹涝胁迫下铵态氮处理(AF)叶片含氮量、植株含钾量呈降低趋势;非淹涝胁迫下铵态氮处理(A)具有相对较高的植株氮、磷含量,且淹涝胁迫对氮、磷、钾在植株不同部位分配的影响相对较低。因此,本试验供应铵态氮苗期玉米具有相对较强的耐淹涝胁迫能力。     

氮素形态配比对玉米氮素积累及转运的影响

通过田间试验,研究6种(N_1~N_6)硝态氮与铵态氮配比处理对旱地全膜双垄沟播玉米植株氮素积累、转运、氮素利用及子粒产量的影响。结果表明,单施硝态氮时玉米的养分吸收、氮素利用及产量均最低。N6(硝态氮与铵态氮3∶1配比)处理下玉米全生育期氮素积累量最高,氮素吸收强度较单施硝态氮处理高55.19%~73.28%(P0.05),该处理下叶片和茎中氮素转移量较单施硝态氮处理高78.99%和93.52%(P0.05);叶片和茎中分别有66.50%~71.89%和43.44%~55.59%的氮素转移到子粒中;叶片和茎对子粒的氮素贡献率分别较单施硝态氮处理高43.80%和56.00%(P0.05);玉米子粒产量、氮素吸收效率及氮肥偏生产力较其他处理显著增加3.31%~9.94%、4.62%~33.89%和3.31%~9.93%。硝态氮和铵态氮配施对玉米的养分吸收有明显的促进作用,提高硝态氮的施用比例有利于提高玉米叶片和茎对子粒氮素的贡献率,硝态氮与铵态氮按3∶1比例配施有利于提高当地玉米子粒产量。     

利用15N标记研究铵态氮与硝态氮对大豆的营养作用

以东农47为材料,采用15N示踪技术,利用组培的方式进行了铵态氮与硝态氮营养作用研究.结果表明,在无菌条件下,以NH4+-N为唯一氮源大豆表现出了铵盐毒害;以NO3--N和混合态氮作为氮源时,大豆可以正常生长.以混合态氮为氮源植株总生物量最大,以NO3--N为氮源次之,以NH4+-N为氮源的处理生物量最小,不同形态氮之间生物量差异达到显著水平.随氮素水平增加,外源氮在植株中比例增加,当培养基中NH4+-N与NO3--N比例为1∶1时,大豆吸收NH4+-N与NO3--N比例为1.5∶1,叶片、茎、根NH4+-N与NO3--N吸收比例分别为1.6∶1、1.4∶1和1.6∶1,说明硝态氮的存在能够解除铵盐毒害并促进大豆对氮素的吸收利用.     

土壤有效磷含量对大豆植株磷素含量和土壤有效N、P、K含量的影响

土壤有效磷含量影响大豆植株对N、P、K的吸收利用,进而影响大豆植株的生长发育和产量形成。以吉育89为材料,在大豆不同生长时期测定大豆植株磷素含量和土壤N、P、K含量,研究其随土壤有效磷含量升高而发生变化的规律。结果表明:在取样的4个时期里,植株磷素含量均随土壤有效磷含量的升高呈单峰曲线变化,在土壤磷素水平为30 mg·kg~(-1)时,植株磷素含量达到最大;5个处理的土壤速效磷含量变化趋势都是先下降,在收获期由于土壤自身的磷素补偿作用而有所升高;在各生育时期的土壤中的硝态氮和速效钾含量最低值都出现在有效磷含量为30 mg·kg~(-1)处理,而土壤速效磷含量为10和50 mg·kg~(-1)两个处理的硝态氮和速效钾含量一直较高,说明低磷和高磷土壤对植株氮素吸收有抑制作用。土壤有效钾含量的变化情况与硝态氮相似,均是随土壤有效磷含量升高而呈单峰曲线变化。说明N、P、K肥的合理配比均能够提高肥料的作用效果。     

氮素形态与吡虫啉对甘蔗根系和地上部生长的影响

本研究通过水培的方式,探究不同形态氮素以及不同形态氮素和新烟碱类杀虫剂吡虫啉（IMI）处理对甘蔗生长、根系伤流强度和根系形态的影响。研究结果显示：与缺氮（CK）相比,添加铵态氮（A）、硝态氮（N）或铵态硝态氮（AN）能够显著提高甘蔗植株的株高和茎径（P<0.05）,其中株高增高了大约3倍,茎径增粗2~3倍,与硝态氮相比,铵态氮能促进甘蔗茎径变粗、鲜重增加以及侧根和不定根的形成;硝态氮为氮源可促进甘蔗根系的纵向生长;铵态氮和硝态氮共存时甘蔗根系总长、根表面积、根系体积以及伤流液强度大于单一氮源处理。添加吡虫啉促进了缺氮条件下甘蔗的生长;与对应的氮素处理组相比,吡虫啉和氮素共处理组甘蔗的鲜重均增加,其中A+IMI处理比A处理增加17.69%,N+IMI处理比N处理增加46.19%,AN+IMI处理比AN处理增加29.43%,在硝态氮存在时差异达到显著水平（P<0.05）;此外,吡虫啉和硝态氮共存显著提高了甘蔗根系总长、根表面积和伤流液强度（P<0.05）。结果表明铵态氮和吡虫啉共施对甘蔗整体的生长最为有利,吡虫啉和硝态氮共施可促进甘蔗鲜重增加以及根系的生长。本研究为甘蔗氮肥施用以及吡虫啉和氮肥在甘蔗中的共施提供重要的理论依据,同时,为“药肥一体化”技术在甘蔗上的应用提供借鉴。     

施氮对玉米产量和氮素积累及相关生理指标的影响

通过田间试验研究施氮对玉米产量、氮素积累及相关生理指标的影响。结果表明,施氮使玉米产量提高,与对照处理差异达极显著水平(P<0.01)。施氮处理使玉米植株的氮素积累量、叶片叶绿素含量、SPAD值、植株中硝态氮和可溶性蛋白含量均增加。相关分析表明,玉米植株干物质积累量与氮素积累量呈极显著正相关;植株干物质积累量、氮素积累量均与植株中硝态氮含量呈极显著正相关。因此,可用植株中硝态氮含量作为预测植株吸氮量及生物量的参考,为指导农业生产中合理施用氮肥提供依据。     

锰胁迫对不同基因型玉米幼苗氮素转化的影响

以常规锰浓度为对照,设置锰缺乏和锰过量胁迫条件,研究游离态和络合态锰对不同基因型玉米早期氮代谢影响。结果表明,随着锰浓度的升高,根系硝态氮含量下降,品种东青1号下降幅度最小。品种垦粘1号和双玉201铵态氮含量随锰浓度增加呈先降低后升高趋势。吉农大516和东青1号随着锰胁迫增强,根部铵态氮含量下降。MnCl2·4H2O处理的玉米幼苗根系铵态氮积累程度大于EDTA-Mn处理,锰胁迫显著抑制根系可溶性蛋白合成。随着锰浓度增大,根系可溶性蛋白含量逐渐降低。MnCl2·4H2O处理根部可溶性蛋白下降程度大于EDTA-Mn处理。吉农大516根部可溶性蛋白含量最高。双玉201可溶性蛋白合成受抑制程度较大。锰胁迫影响根部氮素养分的有效分配,阻碍韧皮部运输而使得部分氮素于根部积累。锰胁迫条件下,东青1号为耐受品系,双玉201为敏感品系;游离态锰离子对玉米幼苗氮素转化抑制程度大于络合态锰离子。     

质子泵在不同氮素形态调控茶树磷素吸收的功能研究

磷是植物生长发育的重要矿质营养元素之一,不同氮素形态均影响植物对磷素的吸收。植物细胞膜H⁺-ATPase在矿质营养元素吸收过程中具有重要调控作用,因此不同氮素形态调控茶树磷素吸收可能与细胞膜H⁺-ATPase相关。本研究采用二相分离法提取茶树根系质膜,并通过非损伤微测（NMT）、Western-blot等技术探究不同氮素形态对舒茶早根系磷素吸收和细胞膜H⁺-ATPase特征参数的影响。结果表明,铵态氮提高茶树对磷素的吸收;其茶树根系细胞膜电位、H⁺跨膜运输、H⁺-ATPase活性和蛋白表达均高于硝态氮处理;且细胞膜H⁺-ATPase专一抑制剂正钒酸钠（Na₃VO₄）显著减少不同氮素形态下茶树根系对磷素的吸收和富集。由此可见,茶树根系H⁺-ATPase可能参与不同氮素形态调控磷素的吸收。     

缺氮对油菜养分吸收及钾吸收转运相关基因表达的影响

为进一步了解缺氮对油菜养分吸收的影响,以甘蓝型油菜中双11号为材料,采用营养液培养方法,设置正常供氮和缺氮两个处理,培养14d后收获,分析缺氮对油菜植株表型、生物量、植株养分含量及养分吸收相关基因表达的影响。结果表明,缺氮严重抑制油菜植株生长,地上部生物量显著减少,叶片瘦小、黄化,茎秆呈紫红色。缺氮促进油菜根系生长,植株根冠比增加。缺氮处理对油菜叶、茎、根中大量元素含量的影响有所不同,缺氮油菜叶、茎、根的氮浓度及氮含量都显著降低;油菜叶、茎的磷浓度在缺氮胁迫时显著增加,根的磷浓度显著降低,而茎和根的磷含量在缺氮胁迫时都显著降低,但叶片磷含量不受影响;油菜不同部位钾浓度和钾含量在缺氮胁迫时都显著降低,并且缺氮处理14d显著抑制油菜大部分钾通道蛋白基因以及3个根部特异钾转运蛋白基因的表达,说明缺氮对油菜钾吸收运转相关基因表达的影响,可能导致油菜植株钾含量的降低。     

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.     

Mineral composition of some traditional Mexican teas

Teas of plant origin traditionally consumed by the Mountain Pima of Chihuahua, Mexico, were analyzed for mineral nutritional content. Fe, Cu, Zn, Ca, and Mg composition was determined for native teas made from shoots ofTagetes lucida, T. filifolia, Elytraria imbricata, andHolodiscus dumosus, and from root xylem ofCeanothus depressus andPhaseolus ritensis. Native uses of these teas are also described.     

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.