Samples Of Plant Material Research Articles

A fifty-channel digital recorder for thermocouple psychrometers

Outputs from fifty thermocouples are recorded by converting the movement of a galvanometer light spot into a series of electrical impulses which are then amplified, shaped, counted, and finally printed on a paper strip. The thermocouples act as wet- and dry-bulb thermometers to measure the relative humidity of vapour in equilibrium with small samples of soil or plant material and the principle of Peltier cooling is exploited to deposit water on the wet bulbs. Passage of the cooling current, switching of the thermocouple circuits and the initiation of counting and printing operations are controlled by a programme timer and a selector which allows any combination of psychrometer units to be scanned repetitively. The precision of the system (equivalent to one digit) is ±0·0007 degC or 0·007% in relative humidity at 25°C or 10 J kg−1 (1 metre) in water potential.

Automated System for Determining Respiratory Gas Exchange of Plant Materials1

Abstract A continuous gas flow system is described which utilizes a paramagnetic O2 analyzer and an infra-red CO2 analyzer to automatically sample, analyze, and record respiratory gas exchange of plant material. The system monitors gas exchange of up to 96 plant samples sequentially, repeatedly, and over extended time periods.

Birmingham University Radiocarbon Dates III

Measurements have continued with the 6 L counter. A counter of similar design but with 1 L volume has recently been brought into operation. Despite replacement of the teflon parts, the 1.5 L Oeschger-type counter has not worked consistently and has not been used for dating. Results are not corrected for δ C13. Errors quoted refer only to the standard deviation calculated from a statistical analysis of count rates and the Libby half-life of 5570 ± 30 yr.Alkali pretreatment is used for all samples of charcoal, peat, wood, and plant material provided they are of sufficient quantity. It is now standard practice to boil the sample in 5% HCl solution and filter, both before and after boiling it in 2% NaOH solution. Between each treatment it is washed in boiling distilled water and is finally oven dried at 110°C. Concentrations of acid and alkalis are varied to suit each sample but the sequence of the pretreatment is always the same. In some cases a humate extract is obtained by precipitation with weak acid from the alkali solution filtrate.The collagen fraction is obtained from samples of bone using the method of Krueger (1966) by treatment with dilute acid under reduced pressure. The gas evolved during the treatment is usually discarded but is occasionally retained and dated as the mineral fraction.After mechanical cleaning, samples of shell are dissolved in stages with 6N HCl to divide them into two or three fractions corresponding to the outer, middle, and inner layers of the shell. Normally the outer fraction is discarded when three fractions have been prepared.

Multi-element analysis by means of atomic absorption with a time-resolved spark as primary light source

The use of a time-resolved spark as primary light source for multi-element atomic absorption analysis has been investigated. The elements of interest were introduced into the spark by a solution technique using rotating graphite disk electrodes. Time resolution of the spark radiation was achieved with a rotating disk in front of the slit. The following factors influencing the absorption, namely, time, concentration of solution in the spark, speed of rotation of the disk electrode, and the inductance in the spark circuit were investigated in order to choose optimum parameters. The maximum sensitivities obtained for the four elements copper, calcium, magnesium, and zinc compared favourably with those obtained with hollow cathode lamps as primary sources. Owing to the relatively poor reproducibility of the spark emission the reproducibility of the absorption measurements is not good. A sample of plant material was analysed using this technique and the advantages of the method, namely, simultaneous multi-element analysis and the simplicity of altering the atomic absorption working range by variation of spark parameters, are illustrated.

Analyse isotopique de l'azote par spectrometrie optique, pour de faibles teneurs en 15n

For mixtures of 14N 2 and 14N 15N low in 15N (isotopic abundances less than 2%), previous optical spectrometric methods do not produce rapid results of sufficient precision. In this paper, operating conditions are described for the determination of the isotopic content to ±3% near the natural abundance and to ±1% when the sample contains an atom ratio of 15N: 14N of 1.5:100. The time required for a determination is ca. 10 min. A spectrometer is modified by the substitution of an exit slit and a photomultiplier in place of a photographic plate. The excitation of the electrodeless discharge tube is made by a high-frequency field. The method has been applied to samples of ammonium salts, fertilisers and plant material. In all cases, the precision of the isotopic measurements was greater than that required for most agricultural studies (5–6%).

Micro-determination of zinc and copper in a single digest of small samples of plant material

The first page of this article is displayed as the abstract.

The ionic composition of rainwater at Katherine, NT. and its part in the cycling of plant nutrients

Rainwater was collected from individual showers at Katherine, Northern Territory, Australia, during the 1958–59 wet season, and again in 3.4 mm portions of individual showers during the 1959–60 wet season. Strict precautions were taken during rainless periods to prevent particulate material from accumulating in the rain collector. The laboratory examination of the samples included determinations of nitrate, ammonium, sodium, potassium, magnesium, and chloride ions, and of insoluble silica. Soil and plant material samples collected in the surroundings of Katherine were also analysed for a number of elements. In spite of a total annual average rainfall of 925 mm the annual total amount of soluble material in the rainwater was less than 6–7 kg 'ha. The concentration of all ions decreased during the progress of a shower, and from shower to shower, during the progress of the season. Correlation coefficients between the different ions were all positive and generally high. No relation could be detected between the nitrate content in the rainwater and the incidence of lightning. The correlation between chloride content and amount of insoluble silica was high (+ 0.73). It is argued that most of the material in the rainwater is part of a terrestrial cycle and cannot be regarded as a true accession.

A method for wet-ashing small plant samples

An inexpensive but efficient and fast method is described for the wetashing of small samples of plant materials.

Direct Reading Spectrometric Determination of Zinc, Copper and Lead in Plant Material

A method is described for the direct reading spectrometric determination of zinc, copper and lead in plant material. The metals to be determined are separated by dithizone extraction from a solution of 1 gram of the plant material. The excitation source consists of an interrupted d c. arc struck between a graphite counter electrode and a rotating graphite-sodium carbonate disc, on to which a chloroform solution of the metal dithizonates is sprayed. Spectrum line emission measurements are made by means of a medium dispersion quartz prism spectrograph with direct reading attachment A series of plant material samples has been analysed by the method and the standard deviations of the results obtained from the mean of two arcings in each of ten replicate analyses were found to be 5.1% for zinc, 73% for copper and 61 % for lead.

Persistence of alkaloids in plant tissue.

Under appropriate conditions of preservation, alkaloids can be detected in plant tissues after extended periods of time. A positive test for this class of compounds was given by a sample of plant material estimated to be 1300 years old.

The determination of fluoroacetic acid and fluoroacetamide in plant material

AbstractAn analytical method is described for the determination of total organically combined fluorine in a mixture of fluoroacetamide and fluoroacetic acid in plant material; a method is also suggested for the determination of fluoroacetamide alone. On a 100‐g. sample of plant material 1 p.p.m. can be determined with an accuracy of 13% and 0.1 p.p.m. with an accuracy of 50%. The methods involve the determination of the fluorine content of plant extracts and therefore depend for their validity on the removal of interfering fluorine‐containing plant constituents.

Correction of ‘Crude-Fibre’ Estimation for the Effect of Altitude

IN the estimation of crude fibre at altitudes appreciably above sea-level, it is necessary to correct for lowered boiling points of reagents and consequent reduced speeds of reaction. When Todd1 estimated crude fibre in ten samples of plant materials at sealevel and at 6,200 ft., he calculated the percentage error involved in each instance and proposed three ways of correcting, namely: (1) by increasing the duration of the boiling; (2) by increasing the concentration of acid and alkali; (3) by carrying out the estimation by the standard procedure and applying a correction factor.

Nutrient Interactions and Deficiency Diagnosis in the Lettuce

A sand-culture experiment with lettuces is described, having as its principal purpose the study of the relationship between the potential responses of plants to applications of nitrogen, phosphorus, and potassium fertilizers and the composition of. their foliage. Plants were supplied initially with five levels of these nutrients in all combinations, samples of plant material were taken fot analysis at various stages of development, and at 44 days from sowing additional quantities of nutrients were supplied to some of the cultures in order that their response potentialities might be determined. The present paper analyses the effects of the nutrient interactions on plant dry weight, further results being left to subsequent papers.