蔬菜中的硝酸盐及其影响因子

硝酸盐对人体健康的危害已引起世界各国的极大关注。硝酸盐可经硝酸还原菌的作用,在动物体内外还原成亚硝酸盐,亚硝酸盐可使血红蛋白中的二价铁氧化成三价铁,失去与氧结合的能力,使细胞陷入缺氧状态而中毒,严重者可以致死。另外,亚硝酸可与人和动物摄取的其它食品、医药品、残留农药成分中的次级胺反应,在胃腔中形成强力致癌物质——亚硝胺,从而诱发人和动物消化道系统癌变。尽管上述二者单独存在时并不致癌。但亚     

重庆市蔬菜硝酸盐、亚硝酸盐含量及其与环境的关系

在重庆市的主要蔬菜中,硝酸盐含量依次为根菜类＞叶菜类＞葱蒜类＞瓜类＞豆类＞茄果类,前３类的硝酸盐含量超标,但各种蔬菜的亚硝酸盐含量一般较低,未超过卫生标准。就同一种蔬菜的不同样品而言,硝酸盐和亚硝酸盐含量的差异很大,说明品种或环境条件可显著影响其含量。重庆市多雾少光,冬春低温,土壤含氮量和钠高子含量较高,有效钾含量较低可能是导致蔬菜大量积累硝酸盐的环境因素。蔬菜不同器官硝酸盐和亚硝酸盐含量各异,根＞茎＞叶柄＞叶片。     

几种野生蔬菜硝酸盐及维生素C含量的研究

野生蔬菜不仅具有较高的营养价值,还有相当高的医疗价值。近代研究表明,过量的食入硝酸盐,会诱发消化系统癌变,而维生素 C 有防癌作用,因此硝酸盐和维生素 C含量为评价蔬菜品质的重要指标之一。一般栽培的叶菜类蔬菜如白菜、菠菜、苔菜等硝酸盐含量很高,平均存4000mg/kg 鲜重左右。野生蔬菜中的硝酸盐及维生素 C 含量如何呢?我们仅对几种分布广泛,食用历史较长,营养价值较高的野生蔬菜进行了研究,以期为科学地有选择性地开发野生蔬菜资源提供有价值的依据。     

几种叶类蔬菜中硝酸盐和亚硝酸盐含量变化及其化学调控

几种叶类蔬菜中硝酸盐和亚硝酸盐含量变化及其化学调控陈振德,冯东升（青岛市农科所,青岛２３６１Ｕ０）（山东农业大学基础部,泰安２７１０１８）ＣＨＡＮＧＥＳＯＦＮＩＴＲＡＴＥＡＮＤＮＩＴＲＩＴＥＣＯＮＴＥＮＴＳＡＮＤＴＨＥＩＲＣＨＥＭＩＣＡＬＲＥＧＵＬＡ...     

降低蔬菜硝酸盐含量的食前处理方法

以小白菜、萝卜和四季豆为试材,研究了不同食前处理（清水浸泡、盐渍、漂烫）对蔬菜硝酸盐和维生素C（VitC）含量的影响。结果表明,清水浸泡和漂烫处理均可较大程度地降低蔬菜硝酸盐含量;盐渍处理硝酸盐含量下降不明显,其中萝卜经盐渍后硝酸盐含量反而升高;三种处理方式以漂烫0.5 min处理蔬菜VitC含量损失最小。     

氮肥施用与蔬菜硝酸盐积累的相关研究

蔬菜是一种容易富集硝酸盐的作物,人体摄入的硝酸盐有８１．２％来自蔬菜,而 酸盐是强致癌物－－－亚硝胺的前体物。硝酸盐在一定条件下可墨迹为亚硝酸盐,对人体前直接破坏血红蛋白中的Ｆｅ＾２＋等危害。为获高产,不合理地超量施用化学氮肥,使得蔬菜硝酸盐积累量剧增,品质退化。研究表明：筛选出氯化铵、硫酸铵两种氮肥品种,氮素施用剂量以３００ｋｇ／ｈｍ＾２为临界值;氮肥施用安全始期以施氮后８ｄ为宜;化学氮肥与有机     

氮磷钾肥施用对蔬菜中硝酸盐积累的数学模型

氮磷钾肥施用对蔬菜中硝酸盐积累的数学模型段咏新付庭治（徐州师范学院生物系,２２１００９）（南京大学生物系,２１０００８）ＭａｔｈｅｍａｔｉｃａｌＭｏｄｅｌｏｎＮｉｔｒａｔｅＡｃｃｕｍｕｌａｔｉｏｎｉｎＶｅｇｅｔａｂｌｅａｆｔｅｒＡｐｐｌｙｉｎｇＮ,ＰａｎｄＫＦｅｒｔｉｌｉｚｅｒｓ￥ＤｕａｎＹｏｎｇｘｉｎ（ＤｅｐａｒｔｍｅｎｔｏｆＢｉｏｌｏｇｙ,ＸｕｚｈｏｕＴｅａｃｈｅｒ＇ｓＣｏｌｌｅｇｅ,２２１００９）,ＦｕＴｉｎｇｚｈｉ（ＤｅｐａｒｔｍｅｎｔｏｆＢｉｏｌｏｇｙ,ＮａｎｊｉｎｇＵｎｉｖｅｒｓｉｔｙ,２１０００８）．ＣｈｉｎｅｓｅＪｏｕｒｎａｌｏｆＥｃｏｌｏｇｙ,１９９３,１２（６）：３４－３６．ＩｎＴｈｉｓｐａｐｅｒ,ａｒｅｇｒｅｓｓｉｏｎｗｏｄｅｌｏｎｎｉｔｒａｔｅａｃｃｕｍｕｌａｔｉｏｎｉｎｓｐｉｒａｃｈｉｓｅｓｔａｂｌｉｓｅｄ,ｗｈｉｃｈｃａｎｐｒｅｄｉｃｔｔｈｅａｃｃｕｍｕｌａｔｉｏｎａｍｏｕｎｔｏｆｎｉｔｒａｔｅｕｎｄｅｒｄｉｆｆｅｒｅｎｔａｐｐｌｉｃａｔｉｏｎｒａｔｅｓｏｆＮ,ＰａｎｄＫｆｅｒｔｉｌｉｚｅｒｓ。Ｕｓｉｎｇｔｈｉｓｍｏｄｅｌ,ｔｈｅｎｉｔｒａｔｅｃｏｎｔｅｎｔｉｎｓｐｉｒａｃｈｃａ     

蔬菜中硝酸盐对心血管健康的改善作用

综述了硝酸盐对心血管健康相关功效的研究进展,并对硝酸盐的食物来源和安全性进行了论述。     

广东8种野菜中硝酸盐、亚硝酸盐及Vc的含量

测定了广东菊科8种野菜中硝酸盐、亚硝酸盐和维生素C的含量,结果表明：革命菜、一点红、苣荬菜的硝酸盐含量低于轻度污染水平,属于一级野菜;山莴苣、地胆草、加拿大蓬和艾的硝酸盐含量低于785mg/kg,达中度污染水平,属二级蔬菜范围,不宜生食,煮熟或盐渍可安全食用;甜菜籽属于三级蔬菜,不可生食和盐渍,可熟食.这些野菜维生素C的含量均低于50mg/100g（鲜重）,属于中、低维生素C含量的野菜.     

六种野菜不同部位硝酸盐、亚硝酸盐及维生素C的含量

报道了6种野菜不同部位的硝酸盐、亚硝酸盐和维生素C的含量。参考蔬菜中硝酸盐含量分级评价标准和无公害蔬菜亚硝酸盐含量限量标准,结合各种野菜及不同部位的维生素C的含量,对这6种野菜评价如下:鼠麴草的叶、龙葵的叶、苋的嫩茎和叶,属于一级野菜,可以安全食用;鼠麴草的嫩茎属二级蔬菜范围,不宜生食,煮熟或盐渍可安全食用;龙葵的嫩茎、树仔菜的嫩茎,属于三级蔬菜,不可生食和盐渍,可熟食。白子菜的嫩茎和狗肝菜的嫩茎,属于四级蔬菜,不宜食用或限量食用;树仔菜的叶、白子菜的叶亚硝酸盐含量高于我国制定的无公害蔬菜亚硝酸盐含量的限量标准,所以不宜食用或限量食用。     

施氮对不同品种冬小麦植株硝态氮和硝酸还原酶活性的影响

以黄土高原南部半湿润区土垫旱耕人为土为供试土壤进行盆栽试验,以NR 9405、9430、偃师9号、小偃6号、陕229号和西农2208冬小麦品种为供试材料,研究施氮对不同品种冬小麦植株硝态氮含量和硝酸还原酶活性(NRA)的影响.结果表明,施氮能明显增加叶片NRA.不施氮时除小偃6号和偃师9号外,其余品种NRA在全生育时期的动态变化均呈双峰曲线,2个高峰期分别在返青期和开花期,且开花期高峰值(36.17 NO2-μg.-g 1FW.h-1)明显比返青期峰值(15.407 NO2-μg.-g 1FW.h-1)大;施氮时不同品种叶片NRA在全生育期呈单峰曲线变化,最高峰在开花期,平均峰值为80.93 NO2-μg.-g 1FW.h-1),比同期不施氮处理增加1倍以上.施氮后地上部硝态氮含量在各时期均显著提高,在小麦生育前期(出苗到拔节)表现最为显著.氮肥对不同品种硝态氮含量的影响程度基本上与对NRA的影响程度相反,即施氮后硝态氮增加幅度小的品种,NRA却增加幅度大.     

江西上饶5种野菜硝酸盐和Vc含量

测定了江西上饶地区常见的5种野菜（蔊菜、马齿苋、车前、山莴苣和水芹）的硝酸盐和Vc含量,结果表明：5种野菜的硝酸盐含量相差较大,分别为26.76、77.66、22.92、70.99和1.54 mg/kg,均未超过FAO/WHO规定的日允许量（ADI）的计算值;5种野菜的Vc含量相差不大。水芹的硝酸盐含量最低,故其利用价值较大。     

西双版纳野生蔬菜中硒含量测定

为从天然植物中寻找富硒食品 ,分析了西双版纳地区常用的 6 8种野生蔬菜的硒含量。结果表明 ,6 8种野生蔬菜中硒平均含量为 0 0 85 3mgkg-1(干物质 ) ,低于栽培蔬菜中硒含量 ,其中富硒的 8种 ,低硒的 34种 ,极度低硒的 2 6种。 8种富硒含量为 0 84± 0 0 2 5— 0 37± 0 0 2 2mgkg-1(干物质 ) ,平均硒含量高于其它 6 0种野生蔬菜平均硒含量 35倍     

An Improved Method for Determining Lipolytic Acyl-hydrolase Activity

The effects of 2-phthalimidooxyalkanoic acid derivatives on the germination and root-growth of cress were examined. Since 2-phthalimidooxypropionates were most effective, the optically active ethyl esters were prepared. As the result of biological testing, the (S)-(-)-isomer exhibited stronger activity than the (R)-(+)-isomer. This result is contrary to those from commercial herbicides with similar structures, phenoxy- and oxyphenoxy-propionate-type compounds, where the (R)-isomers are generally known to be the active principles.     

一种禾本科植物鲜叶下表皮制片方法

介绍一种禾本科植物鲜叶下表皮制片的快速方法,该方法也能适用于多数单子叶植物鲜叶和经FAA固定液固定的单子叶植物叶片的气孔观察。该方法制片能有效防止叶表皮脱水、透明后发生卷曲,使保持完整的结构,便于准确的显微观察。具操作简单、材料易得、可靠性和稳定性高等优点。     

Nitrate and ammonium as nitrogen sources for lupins prior to nodulation

Two cultivars of Lupinus angustifolius L. were grown in a glasshouse in solutions containing NO₃ ^-, NH₄ ⁺ or NH₄NO₃ with a total nitrogen concentration of 2.8 M m^-3 in each treatment. One cultivar chosen (75A-258) was relatively tolerant to alkaline soils whereas the other (Yandee) was intolerant to alkalinity. Controlled experiments were used to assess the impact of cationic vs. anionic forms of nitrogen on the relative performance of these cultivars. Relative growth rates (dry weight basis) were not significantly different between the two cultivars when grown in the presence of NO₃ ^-, NH₄ ⁺ or NH₄NO₃. However, when NO₃ ^- was supplied, there was a modest decline in relative growth rates in both cultivars over time. When plants grown on the three sources of nitrogen for 9 days were subsequently supplied with ¹⁵NH₄NO₃ or NH₄ ¹⁵NO₃ for 30 h, NH₄ ⁺ uptake was generally twice as fast as NO₃ ^- uptake, even for plants grown in the presence of NO₃ ^-. Low rates of NO₃ ^- uptake accounted for the decrease in growth rates over time when plants were grown in the presence of NO₃ ^-. It is concluded that the more rapid growth of 75A-258 than Yandee in alkaline conditions was not due to preferential uptake of NH₄ ⁺ and acidification of the external medium. In support of this view, acidification of the root medium was not significantly different between cultivars when NH₄ ⁺ was the sole nitrogen source.     

An Unexpected Nitrate Decline in New Hampshire Streams

Theories of forest nitrogen (N) cycling suggest that stream N losses should increase in response to chronic elevated N deposition and as forest nutrient requirements decline with age. The latter theory was supported initially by measurements of stream NO₃ ⁻ concentration in old-growth and successional stands on Mount Moosilauke, New Hampshire (Vitousek and Reiners 1975; Bioscience 25:376–381). We resampled 28 of these and related streams to evaluate their response to 23 years of forest aggradation and chronic N deposition. Between 1973–74 and 1996–97, mean NO₃ ⁻ concentration in quarterly samples from Mount Moosilauke decreased by 71% (25 μmol/L), Ca²⁺ decreased by 24% (8 μmol/L), and Mg²⁺ decreased by 22% (5 μmol/L). Nitrate concentrations decreased in every stream in every season, but spatial patterns among streams persisted: Streams draining old-growth stands maintained higher NO₃ ⁻ concentrations than those draining successional stands. The cause of the NO₃ ⁻ decline is not evident. Nitrogen deposition has changed little, and although mechanisms such as insect defoliation and soil frost may contribute to the temporal patterns of nitrate loss, they do not appear to fully explain the NO₃ ⁻ decline across the region. Although the role of climate remains uncertain, interannual climate variation and its effects on biotic N retention may be responsible for the synchronous decrease in NO₃ ⁻ across all streams, overriding expected increases due to chronic N deposition and forest aging. Received 4 December 2001; accepted 30 May 2002.