Extractors for barium,cadmium, copper,nickel, and zinc in tropical soils

ABSTRACT

The accumulation of potentially toxic elements (PTEs) in the soil can pose risks to human health, and precise risk assessment dealing with the production and consumption of plants is required. The 0.43 M of nitric acid (HNO?) solution was suggested by the International Organization for Standardization for reactive fraction of PTEs in the soil. The efficiency of some extractors was evaluated in tropical soils. Contents of barium (Ba), cadmium (Cd), copper (Cu), nickel (Ni) and zinc (Zn) were extracted in accordance with the methods of Environmental Protection Agency (EPA) 3051A, Aqua Regia, Diethylenetriaminepentaacetic acid (DTPA), Mehlich-1, Mehlich-3, 0.43 M HNO? and 0.01 M of calcium chloride (CaCl?), and these contents correlated with the contents of PTEs in roots, shoots, and fruits of vegetables. Mehlich-3 had the highest correlation with Ni and Zn contents extracted by the plants. Contents extracted with 0.43 M HNO? had high correlation with the amounts extracted by DTPA and Mehlich-3, as well as with the amounts of PTEs accumulated by plants.     

CaCl_2对NaCl胁迫下酸枣苗AsA-GSH循环的影响

以酸枣(Ziziphus acidojujuba C.Y.Cheng et M.J.Liu)水培实生幼苗为试材,研究了CaCl_2对NaCl胁迫下其根、茎、叶中抗坏血酸—谷胱甘肽循环(AsA-GSH)的影响。结果表明:与对照(日本园试配方营养液)相比,NaCl处理下根和叶中AsA含量升高,MDHAR活性升高,APX活性下降;根、茎、叶中GSH含量升高。NaCl+CaCl_2处理与NaC处理相比,根和茎中AsA含量进一步升高,叶中AsA含量下降,叶中APX下降,根中MDHAR活性进一步升高,茎和叶中DHAR活性升高;根和叶中GSH含量下降。外源CaCl_2可能通过提高酸枣实生苗根、茎和叶中AsA再生关键酶MDHAR和DHAR活性,促进根和茎中AsA的再生与生物合成,从而提高根、茎清除过量H_2O_2的能力,缓解NaCl胁迫对酸枣幼苗根和茎部的伤害。     

Critical Olsen P and CaCl2‐P levels as related to soil properties: results from micropot experiments

The usefulness of soil phosphorus (P) tests used in routine soil analyses is limited by the fact that a single measurement cannot encompass all P‐related factors potentially affecting plant performance. In this work, we performed micropot (15 mL) experiments to test the hypothesis that the predictive value of two common soil P tests (Olsen P and CaCl₂‐P) can be improved by considering properties commonly measured in laboratory analyses. Forty‐nine sets of soils ranging widely in properties were used for this purpose, each set consisting of samples with similar properties but differing in P status. Ryegrass and turnip were grown in a chamber for 30 days in two separate experiments and their yields at harvest recorded. The critical Olsen P and CaCl₂‐P levels, which were taken to be those corresponding to 95% asymptotic yield as calculated from data fitted to a Mitscherlich equation, were greater for turnip than for ryegrass, probably as a result of the difference in yield (49 and 160 mg dry matter/micropot on average for ryegrass and turnip, respectively) and hence in P requirements between the two species. Critical Olsen P spanned narrower ranges than critical CaCl₂‐P in both crops and is therefore seemingly the more robust of the two tests. Both critical P values exhibited moderate correlations with soil properties. Thus, critical Olsen P was (a) lower in soils with a medium pH – which is consistent with the fact that the bicarbonate solution method tends to overestimate plant‐available P in strongly acid and calcareous soils; (b) positively correlated with pH and carbonate content in calcareous soils; and (c) uncorrelated with soil properties in noncalcareous soils. On the other hand, critical CaCl₂‐P in some soil groups was negatively correlated with some properties increasing the P buffering capacity of soil (e.g. Fe oxide content). Taken together, our results suggest that routinely measured soil properties help to predict critical Olsen P better than critical CaCl₂‐P.     

一种简捷有效的大肠杆菌感受态细胞制备方法

[目的]探索建立简捷快速有效的大肠杆菌感受态细胞制备方法。[方法]在已有的TSS法基础上进行了进一步的改进,建立了一个只需一步室温离心便能够获得与常规方法效价相近,能够长期保存的大肠杆菌感受态细胞的制备方法。[结果]新方法制备的感受态细胞每微克转化菌落数达105~106个,可以满足在质粒中进行的常规克隆需要。不同冻存时间对新方法制备的感受态细胞转化效率无显著影响。新方法制备的感受态细胞可以立即使用也可以于-80℃下长期保存至少9个月不会影响其转化效价。这也与常规CaC l2法制备的感受态细胞性能相当。[结论]该方法为一次大量制备并长期保存使用感受态细胞奠定了基础。     

外源Ca2+对水分胁迫下酿酒葡萄黑比诺主要抗旱生理指标的影响

为了探讨外源Ca2+对葡萄抗旱生理指标的影响,为Ca2+在葡萄耐旱生产中的应用提供参考依据,以盆栽酿酒葡萄黑比诺幼苗为试材,在水分胁迫条件下,用0.5,1.0和1.5 mmol/L CaCl2喷施黑比诺葡萄幼苗,以喷清水作为对照,研究水分胁迫下外源Ca2+对葡萄幼苗主要抗旱生理指标的影响。结果表明,与对照相比,CaCl2处理能够提高葡萄叶片可溶性糖含量、过氧化物酶(POD)及超氧化物歧化酶(SOD)活性,减缓叶绿素的分解,降低MDA含量。在整个水分胁迫期间,可溶性糖含量平均比对照提高46.4%~60.1%,SOD活性提高18.4%~66.6%,POD活性提高1.5%~2.5%,叶绿素a含量提高3.1%~9.4%,MDA含量降低8.1%~23.4%,CaCl2处理对叶绿素a的保护效果显著,对叶绿素b则无明显影响。以1.0 mmol/L CaCl2处理对提高黑比诺幼苗的抗旱性效果最佳。     

外源氯化钙对高温胁迫下叶用莴苣种子萌发及生化特性的影响

采用不同浓度氯化钙溶液浸泡叶用莴苣种子,在人工气候箱的高温胁迫条件（35℃/30℃,Day/Night）下进行发芽试验.7d后调查各处理的发芽率、发芽势、活力指数（Ⅵ）,以及丙二醛（MDA）含量,超氧岐化酶（SOD）、过氧化物酶（POD）和过氧化氢酶（CAT）活性,脯氨酸含量和可溶性蛋白含量.结果表明：浓度在1～5 mmol/L的CaCl2处理时,能显著提高莴苣种子在高温胁迫条件下的发芽率、发芽势、活力指数,同时提高幼苗叶片的过氧化物酶、过氧化氢酶和超氧物歧化酶的活性,增加可溶性蛋白和脯氨酸的含量.当CaCl2处理浓度超过5mmol/L时,不论种子萌发特性还是幼苗的生理生化特性,均反应出处理的效应呈下降的趋势.     

3%CaCl2提高6-BA对蔬菜保鲜作用的研究

采用3?Cl2、不同浓度的6-BA和不同浓度的6-BA 3?Cl2对芥菜进行采后保鲜处理,结果表明,用3?Cl2,5mg/L、10mg/L、20mg/L 6-BA 3?Cl2处理后的芥菜,其鲜重下降率,叶绿素、蛋白质、维生素C含量的下降率,电导率的上升率均比对照降低,呼吸强度抑制比对照提高.在各种处理的组合中,6-BA的作用比3?Cl2明显,而同一浓度6-BA中,以6-BA 3% CaCl2处理的效果比单独用6-BA处理的明显.其中以5mg/L 6-BA处理的效果最为明显.     

家兔高钾血症对心电图的影响及其抢救治疗

为掌握家兔高钾血症模型的复制方法,观察高钾血症时家兔心电图的变化特征和CaCl2以及利尿药对高钾血症的抢救与治疗作用。先记录家兔正常的心电图,再制备高钾血症模型(耳缘静脉注射KCl溶液),观察家兔症状的变化及其心电图的变化特征,再静脉注射5%的CaCl2抢救和静脉注射速尿进行治疗,分别观察记录家兔心电图的变化。结果显示高钾血症能导致家兔的心律失常,其心电图发生明显的变化。静脉推注CaCl2对缓解高钾血症有一定的作用,静脉推注速尿有一定的治疗作用。     

CaCl_2对月季切花保鲜效果的影响

[目的]研究CaCl2对月季切花保鲜效果的影响。[方法]使用含有不同浓度CaCl2的保鲜液进行月季切花瓶插保鲜。[结果]结果表明,不同浓度的CaCl2溶液对月季切花有一定的保鲜作用。其中,含有4 g/LCaCl2+3%蔗糖+300 mg/L8-羟基喹啉柠檬酸盐的保鲜液保鲜效果最佳。处理过的月季切花瓶插寿命有所延长,花枝硬挺,蓝变和花头下垂时间延迟。此外,该处理还具有保持花枝鲜重、维持花瓣中可溶性糖含量、花青素含量和花瓣细胞质膜相对透性的稳定等生理效应。但含有CaCl2的保鲜液对月季切花花瓣组织pH值的上升没有明显的抑制作用。[结论]为今后钙盐在切花保鲜上的应用提供依据。     

Prediction of mineralizable nitrogen in soils on the basis of an analysis of extractable organic N

Most of the nitrogen (N) in agricultural soils is organically bound, while the N uptake by plants and also the N losses from the soil-plant system into the environment are as inorganic N. The electro-ultrafiltration (EUF) method and the extraction by a CaCl₂ solution extract an organic N fraction (Norg) that is thought to provide information about the amount of rapidly mineralizable N in soils. This paper aims to illustrate various aspects regarding the biological meaning of the Norgfractions extracted by these two extraction methods and also the opportunities and limitations for predicting the mineralizable N based on an Norg analysis. From an evaluation of numerous data on EUF and CaCl₂ extract-able Norg fractions we concluded that these methods extract N compounds which can be used as indices for easily mineralizable soil N. However, both methods extract only some of the rapidly mineralizable N in soils, and some of the Norg ecxtracted appears to be from the more recalcitrant soil organic N. This was particularly true for the EUF-method. It may therefore be desirable to improve both the extractability and the selectivity of the extraction methods. This may be achieved by measuring extractable amino-N compounds instead of the total extractable Norg. Evaluating the numerous field experiments done during the last decade shows that the calibration factors obtained for extractable Norg were not the same for different growing seasons, geographical regions and management practices. Theoretically, for each combination of these factors separate calibrations would be necessary. It is this inflexibility which appears to be the most serious drawback for the use of extractable Norg fractions in practice. A possible solution may be to combine the flexibility of a simulation model with additional information obtained by the analysis of extract-able soil organic N. Further work in this direction may be desirable.