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Plant analysis methods. Agrochemical analysis of soils, plants, fertilizers The first methods of chemical analysis of plants were developed

When determining the needs of plants for fertilizers, along with agrochemical analyzes of the soil, field and vegetation experiments, microbiological and other methods, methods of plant diagnostics have been increasingly used.
Currently, the following methods of plant diagnostics are widely used: 1) chemical analysis of plants, 2) visual diagnostics and 3) injection and spraying. Chemical analysis of plants is the most common method for diagnosing the need for fertilizer application.
Chemical diagnostics is represented by three types: 1) leaf diagnostics, 2) tissue diagnostics, and 3) fast (express) methods of plant analysis.
Important steps in plant diagnostics using chemical analysis are: 1) taking a plant sample for analysis; 2) taking into account the accompanying conditions of plant growth; 3) chemical analysis of plants; 4) processing of analytical data and drawing up a conclusion on the need for plants in fertilizers.
Taking plant samples for analysis. When selecting plants for analysis, care should be taken to ensure that the plants taken correspond to the average condition of plants in a given section of the field. If the sowing is homogeneous, then one sample can be limited; if there are spots of better developed or, conversely, worse developed plants, then a separate sample is taken from each of these spots to determine the cause of the altered state of the plant. The nutrient content of well-developed plants can be used in this case as an indicator of the normal composition of a given plant species.
When conducting analyzes, it is necessary to unify the technique of taking and preparing a sample: taking the same parts of a plant by layering, position on the plant, and physiological age.
The choice of plant part for analysis depends on the method chemical diagnostics. To obtain reliable data, it is necessary to take samples from at least ten plants.
In tree crops, due to the peculiarities of their age-related changes, taking plant samples is somewhat more difficult than in field crops. It is recommended to conduct research in the following age periods: seedlings, seedlings, young and fruiting plants. Leaves, their petioles, buds, shoots or other organs should be taken from the upper third of the shoots from the middle zone of the crown of trees or shrubs of the same age and quality, adhering to the same order, namely: either only from fruit shoots, or only from non-fruit shoots, or from shoots of current growth, or leaves in direct sunlight or diffused light. All these points must be taken into account, since they all affect the chemical composition of the leaves. It is noted that the best correlation between chemical composition leaf and fruit yield is obtained if, as a sample, a leaf is taken, in the axil of which a flower bud develops.
At what phase of plant development should samples be taken for analysis? If we keep in mind obtaining the best correlation with the harvest, then the analysis of plants in the flowering or maturation phase turns out to be the best. Thus, Lundegard, Kolarzhik and other researchers believe that flowering is such a phase for all plants, since by this moment the main growth processes are over and the mass gain will not “dilute” the percentage of substances.
To solve the problem of how to change the nutrition of plants in order to ensure the formation best harvest, it is necessary to analyze plants in earlier periods of development and not once, but several times (three or four), starting with the appearance of one or two leaves.
Sampling time. I term: for spring cereals (wheat, oats, corn) - in the three-leaf phase, i.e., before the start of differentiation of the embryonic ear or panicle; for flax - the beginning of the "Christmas tree"; for potatoes, legumes, cotton and others - the phase of four to five true leaves, i.e. before budding; for sugar beet - the phase of three true leaves.
II term: for spring cereals - in the phase of five leaves, i.e., in the phase of piping; for beets - in the phase of deployment of the sixth leaf; for everyone else - during the formation of the first small green buds, i.e., to the very beginning of budding.
III term: in the flowering phase; for beets - when deploying the eighth-ninth leaf.
IV term: in the phase of milk ripeness of seeds; for beets - a week before harvesting.
In woody plants and berries, samples are taken according to the following phases of crop formation: a) before flowering, i.e. at the beginning of strong growth, b) flowering, i.e. during the period of strong growth and physiological shedding of ovaries, c) fruit formation, d ) ripening and harvesting; and e) the period of autumn leaf fall.
When establishing the timing of plant sampling, it is also necessary to take into account during which period of growth and development critical nutritional levels occur. The term "critical levels" means the lowest concentrations of nutrients in plants during the critical period of their development, i.e., concentrations below which the plant deteriorates and yield decreases. The optimal composition of a plant is understood as such a content of nutrients in it in the critical phases of its development, which ensures a high yield.
The values ​​of critical levels and the optimal composition are given for some cultures below. Samples are taken in all cases at the same hours of the day, preferably in the morning (at 8-9 o'clock), in order to avoid changes in the composition of plants due to daily regime nutrition.
Accounting for related conditions. It is not always correct to judge the sufficiency or insufficiency of plant nutrition with certain elements only according to chemical analysis. Many facts are known when a lack of one or more nutrients, a delay in photosynthesis or a violation of water, thermal and other vital regimes can cause the accumulation of one or another element in a plant, which in no case should characterize the sufficiency of this element in the nutrient medium (soil ). To avoid possible errors and inaccuracies in the conclusions, it is necessary to compare the data of the chemical analysis of plants with a number of other indicators: with the weight, growth and rate of development of plants at the time of sampling and with the final harvest, with visual diagnostic signs, with the features of agricultural technology, with the agrochemical properties of the soil, with weather conditions and a number of other indicators affecting plant nutrition. Therefore, one of the most important conditions for the successful use of plant diagnostics is the most detailed account of all these indicators for their subsequent comparison with each other and with the analysis data.

properties of all plant organisms and internal structures inherent in individual species are determined by the multifaceted, constantly changing influence environment. The influence of such factors as climate, soil, as well as the circulation of substances and energy is significant. Traditionally, to identify the properties of medicinal products or foodstuffs, the proportions of substances that can be isolated analytically are determined. But these individual substances cannot cover all internal properties, for example, medicinal and aromatic plants. Therefore, such descriptions of the individual properties of plants cannot satisfy all our needs. For an exhaustive description of the properties of herbal medicinal preparations, including biological activity, a comprehensive, comprehensive study is required. There are a number of methods to identify the quality and quantity of biologically active substances in the composition of the plant, as well as the places of their accumulation.

Luminescent microscopic analysis based on the fact that the biologically active substances contained in the plant give a bright colored glow in a fluorescent microscope, and different chemicals are characterized by different colors. So, alkaloids give a yellow color, and glycosides - orange. This method is mainly used to identify areas of accumulation of active substances in plant tissues, and the intensity of the glow indicates a greater or lesser concentration of these substances. Phytochemical analysis is designed to identify a qualitative and quantitative indicator of the content of active substances in the eastenium. Chemical reactions are used to determine the quality. The amount of active substances in a plant is the main indicator of its good quality, therefore, their volumetric analysis is also carried out using chemical methods. For the study of plants containing active substances such as alkaloids, coumarins,

glavones, which require not a simple summary analysis, but also their separation into components, are called chromatographic analysis. Chromatographic method of analysis was first introduced in 1903 by a botanist

color, and since then its various variants have been developed, which have an independent

meaning. This method of separating a mixture of g-zeets into components is based on the difference in their physical and chemical properties. Using the photographic method, with the help of panoramic chromatography, you can make visible the internal structure of the plant, see the lines, shapes and colors of the plant. Such pictures, obtained from aqueous extracts, are retained on silver-nitrate filter paper and reproduced. The method for interpreting chromatograms is being successfully developed. This methodology is supported by data obtained using other, already known, proven methods.

Based on circulation chromodiagrams, the development of a panoramic chromatography method for determining the quality of a plant by the presence of nutrients concentrated in it continues. The results obtained using this method should be supported by data from the analysis of the acidity level of the plant, the interaction of the enzymes contained in its composition, etc. The main task further development the chromatographic method of plant analysis should be the search for ways to influence plant raw materials during their cultivation, primary processing, storage and at the stage of direct production dosage forms in order to increase the content of valuable active substances in it.

Updated: 2019-07-09 22:27:53

  • It has been established that the adaptation of the body to various environmental influences is ensured by the corresponding fluctuations in the functional activity of organs and tissues, the central nervous

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Chemical analysis of plants for last years received recognition and widespread use in many countries of the world as a method for studying plant nutrition in the field and as a method for determining the need for plants in fertilizers. The advantage of this method is a well-defined relationship between the indicators of plant analysis and the effectiveness of the respective fertilizers. For analysis, not the whole plant is taken, but some specific part, more often a leaf or leaf petiole. This method is called leaf diagnostics.[ ...]

Chemical analysis of plants is carried out to determine the amount of nutrients that have entered them, by which it is possible to judge the need for the use of fertilizers (the methods of Neubauer, Magnitsky, etc.), to determine the indicators of the food and feed value of products (determination of starch, sugar, protein, vitamins, etc.). n) and to solve various issues of plant nutrition and metabolism.[ ...]

Plants were fed with labeled nitrogen in this experiment 24 days after germination. Ammonium sulfate was used as top dressing with a threefold enrichment with the N15 isotope at a dose of 0.24 g N per vessel. Since the labeled ammonium sulfate applied as a top dressing was diluted in the soil with ordinary ammonium sulfate applied before sowing and not completely used by the plants, the actual enrichment of ammonium sulfate in the substrate was somewhat lower, about 2.5. From table 1, which contains the yield data and the results of chemical analysis of plants, it follows that when plants were exposed to labeled nitrogen from 6 to 72 hours, the weight of plants remained practically at the same level, and only 120 hours after the introduction of nitrogen supplementation, it noticeably increased.[ ...]

So far, chemical taxonomy has failed to divide plants into large taxonomic groups on the basis of any chemical compound or group of compounds. Chemical taxonomy comes from the chemical analysis of plants. Until now, the main attention has been paid to European plants and plants of the temperate zone, while the systematic study of tropical plants has been insufficient. In the last decade, however, everything is gaining greater value mainly biochemical systematics, namely for two reasons. One of them is the convenience of using fast, simple and well-reproducible chemical-analytical methods for studying the composition of plants (these methods include, for example, chromatography and electrophoresis), the second is the ease of identifying organic compounds in plants; both of these factors contributed to the solution of taxonomic problems.[ ...]

When discussing the results of the chemical analysis of plants, we pointed out that these data could not be used to establish any regularities in the change in the content of storage proteins in plants at different times of their harvesting. The results of isotopic analysis, on the contrary, indicate a strong nitrogen renewal of these (proteins) 48 and 96 hours after the introduction of top dressing with labeled nitrogen. This forces us to recognize that in reality, storage proteins, as well as constitutional ones, were subjected to continuous changes in the plant body. And if in the first period after harvesting the nitrogen isotope composition of the storage proteins did not change, then this is not a basis for concluding that they are known to be stable in these periods of the experiment.[ ...]

Simultaneous chemical analyzes of plants showed that the total amount of protein nitrogen, both in this and in another similar experiment, for such short periods of time practically did not change at all or changed by a relatively small amount (within 5-10%). This indicates that in plants, in addition to the formation of a new amount of protein, there is a constant renewal of the protein already contained in the plant. Thus, protein molecules in plants have a relatively short lifespan. They are continuously destroyed and recreated again in the process of intensive metabolism of plants.[ ...]

The indicated methods of diagnosing nutrition according to chemical analysis plants are based on the determination of the gross content of the main nutrients in the leaves. Selected plant samples are dried and ground. Then, under laboratory conditions, a sample of plant material is ashed, followed by determination of the total content of N, P205, KrO> CaO, MgO and other nutrients. In a parallel sample, the amount of moisture is determined.[ ...]

Table 10 shows yield data and plant chemical analysis data for both series of experiments.[ ...]

However, in all these experiments, average plant samples were included in the analysis, as is done in the usual determination of the amount of phosphorus uptake by plants from fertilizers. The only difference was that the amount of phosphorus taken by the plants from the fertilizer was determined not by the difference between the phosphorus content in the control and experimental plants, but by direct measurement of the amount of labeled phosphorus that entered the plant from the fertilizer. In parallel, chemical analyzes of plants for the content of phosphorus in these experiments made it possible to determine what proportion of the total phosphorus content in the plant fell on fertilizer phosphorus (labeled) and phosphorus taken from the soil (unlabeled).


Gross analysis is carried out either on the leaves of a certain position on the plant, or in the entire aerial part, or in other indicator organs.
Diagnostics by gross analysis leaves - mature, completed growth, but actively functioning, was called "leaf diagnostics". It was proposed by the French scientists Lagatu and Mom and was supported by Lundegard. At present, this type of chemical diagnostics is widely used both abroad and in our country, especially for plants, in the roots of which nitrates are almost completely reduced, and therefore it is impossible to control nitrogen nutrition in the aerial parts using this form (apple and other seed and stone fruits). , coniferous, rich in tannins, bulbous, etc.).
In the bulk analyzes of leaves or other parts of plants, the usual methods of ashing organic matter are used to determine N, P, K, Ca, Mg, S, and other elements in it. More often, the determination is carried out in two portions: in one, nitrogen is determined by Kjeldahl, in the other, the remaining elements after wet, semi-dry or dry ashing. In wet ashing, either strong H2SO4 with catalysts is used, or mixed with HNO3, or with HClO4, or with H2O2. In dry ashing, careful temperature control is necessary, since when burned at temperatures above 500 ° C, there may be losses of P, S and other elements.
At the initiative of France, in 1959, the Inter-Institute Committee for the Study of the Technique of Chemical Sheet Diagnostics was organized, consisting of 13 French, 5 Belgian, 1 Dutch, 2 Spanish, 1 Italian and 1 Portuguese institutes. In 25 laboratories of these institutes, chemical analyzes of the same samples of leaves of 13 crops (field and garden) were carried out for the total content of N, P, K, Ca, Mg, Fe, Mn, Cu, and Zn. This allowed the committee, after mathematical processing of the data, to recommend methods for obtaining standard leaf samples and give standard methods their chemical analysis to control the accuracy of such analyzes in sheet diagnostics.
Ashing of leaf samples is recommended as follows: to determine total nitrogen according to Kjeldahl, ash with H2SO4 (sp. weight 1.84), with catalysts K2SO4 + CuSO4 and selenium. To determine other elements, dry ashing of the sample in platinum dishes is used with gradual (2 hours) heating of the muffle to 450 ° C; after cooling in a muffle for 2 hours, the ash is dissolved in 2-3 ml of water + 1 ml of HCl (sp. weight 1.19). Evaporate on the stove until the first vapors appear. Add water, filter into a 100 ml volumetric flask. The filter cake is ashed at 550°C (maximum), 5 ml of hydrofluoric acid are added. Dry on a tile at a temperature not exceeding 250 ° C. After cooling, 1 ml of the same HCl is added and filtered again into the same flask, washing off warm water. The filtrate, brought to 100 ml with water, is used for analysis of the content of macro- and microelements.
There is a fairly large variation in the methods of ashing plant samples, which differ mainly in plant species - rich in fats or silicon, etc., and in the tasks of determining certain elements. Enough detailed description The technique for using these methods of dry ashing was given to the Polish scientist Novosilsky. They also give descriptions various ways wet ashing with the help of certain oxidizing agents: H2SO4, HClO4, HNO3 or H2O2 in one or another combination, depending on the elements being determined.
To speed up the analysis, but not to the detriment of accuracy, ways are being sought for such a method of incinerating a plant sample, which would make it possible to determine several elements in one sample. V. V. Pinevich used the ashing of H2SO4 to determine N and P in one sample and subsequently added 30% H2O2 (checking it for the absence of P). This principle of ashing, with some refinements, was found wide application in many laboratories in Russia.
Another widely used method of acid ashing of a sample for the simultaneous determination of several elements in it was proposed by K.E. Ginzburg, G.M. Shcheglova and E.A. Wolfius and is based on the use of a mixture of H2SO4 (sp. weight 1.84) and HClO4 (60%) in a ratio of 10: 1, and the mixture of acids is preliminarily prepared for the entire batch of the analyzed material.
If it is necessary to determine sulfur in plants, the described methods of ashing are not suitable, since they include sulfuric acid.
P.X. Aydinyan and his collaborators suggested burning a plant sample to determine sulfur in it, mixing it with bartholite salt and clean sand. The method of V. I. Kuznetsov with his collaborators is a somewhat revised Schöniger method. The principle of the method consists in rapid ashing of the sample in a flask filled with oxygen, followed by titration of the resulting sulfates with a solution of barium chloride with a barium nitchromase metal indicator. To ensure greater accuracy and reproducibility of the analysis results, we recommend passing the resulting solution through a column with an ion exchange resin in H+ form in order to free the solution from cations. The sulfate solution thus obtained should be evaporated on a hot plate to a volume of 7-10 ml and titrated after cooling.
Novosilsky, pointing out the large losses of sulfur during dry ashing, gives recipes for ashing plants for these analyses. The author considers one of the most simple and fast method ashing according to Butters and Chenery with nitric acid.
The determination of the content of each element in a sample ashed in one way or another is carried out by various methods: colorimetric, complexometric, spectrophotometric, neutron activation, using autoanalyzers, etc.