The study of medicinal plants. Agrochemical analysis of soils, plants, fertilizers Chemical research methods in plants
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 the chemical composition of the leaf and the yield of fruits is obtained if a leaf is taken as a sample, 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.
As early as the beginning of the 16th century. an important truth was established: medicinal properties each plant is determined by its chemical composition, i.e., the presence in it of certain substances that have a certain effect on the human body. As a result of the analysis of numerous facts, it was possible to identify certain pharmacological properties and the spectrum of therapeutic action of many groups of chemical compounds called active ingredients. The most important of them are alkaloids, cardiac glycosides, triterpene glycosides (saponins), flavonoids (and other phenolic compounds), coumarins, quinones, xangons, sesquiterpene lactones, lignans, amino acids, polysaccharides and some other compounds. Of the 70 groups of currently known natural compounds, we are often interested in only a few groups that have biological activity. This limits the choice and thus speeds up the search for the natural chemicals we need. For example, antiviral activity possess only some groups of flavonoids, xanthones, alkaloids, terpenoids and alcohols; antitumor- some alkaloids, cyanides, triterpene ketones, diterpenoids, polysaccharides, phenolic compounds, etc. Polyphenolic compounds are characterized by hypotensive, antispasmodic, antiulcer, choleretic and bactericidal activity. Many classes of chemical compounds and individual chemicals have a strictly defined and rather limited spectrum of biomedical activity. Others, usually very broad classes, such as alkaloids, have a very wide, varied spectrum of action. Such compounds deserve a comprehensive medical and biological study, and above all in the areas of interest to us, recommended. Advances in analytical chemistry have made it possible to develop simple and quick methods(express methods) detection in the classes (groups) of chemical compounds and individual chemicals that we need. As a result of this, the method of mass chemical analyzes, otherwise called chemical screening (from English word screening - sifting, sorting through a sieve). Often it is practiced to search for the desired chemical compounds by analyzing all the plants of the study area.
Chemical screening method
The chemical screening method, combined with data on the use of the plant in empirical medicine and taking into account its systematic position, gives the most effective results. Experience suggests that almost all plants used in empirical medicine contain classes of biologically active compounds known to us. Therefore, the search for the substances we need, first of all, should be purposefully carried out among plants that have somehow discovered their pharmacological or chemotherapeutic activity. Express method can be combined with a preliminary selection of promising species, varieties and populations as a result of their organoleptic evaluation and analysis of ethnobotanical data, indirectly indicating the presence of substances of interest to us in the plant. A similar selection method was widely used by Academician N. I. Vavilov in assessing the quality of the source material of various useful plants involved in breeding and genetic research. During the years of the first five-year plans, searches were carried out in this way in the flora of the USSR for new rubber-bearing plants.
For the first time on a large scale chemical screening method when looking for new medicinal plants began to use the head of the Central Asian expeditions of the All-Union Scientific Research Chemical-Pharmaceutical Institute (VNIHFI) P. S. Massagetov. Examination of more than 1400 plant species allowed Academician A.P. Orekhov and his students to describe about 100 new alkaloids by 19G0 and organize in the USSR the production of those that are necessary for medical purposes and pest control. The Institute of Chemistry of Plant Substances of the Academy of Sciences of the Uzbek SSR examined about 4,000 plant species, identified 415 alkaloids, and for the first time established the structure of 206 of them. VILR expeditions examined 1498 plant species of the Caucasus, 1026 species of the Far East, many plants of Central Asia, Siberia, and the European part of the USSR. Just on Far East 417 alkaloid-bearing plants were found, including semi-shrub securinega containing a new alkaloid securinine, a strychnine-like agent. By the end of 1967, the structure of 4349 alkaloids had been described and established worldwide. The next stage of the search is in-depth comprehensive assessment of pharmacological, chemotherapeutic and antitumor activity isolated individual substances or total preparations containing them. It should be noted that in the country as a whole and globally chemical research are far ahead of the possibilities of deep medical and biological testing of new chemical compounds found in plants. At present, the structure of 12,000 individual compounds isolated from plants has been established; unfortunately, many of them have not yet been subjected to medical and biological study. Of all classes, chemical compounds are most greater value definitely have alkaloids; 100 of them are recommended as important medicines, for example, atropine, berberine, codeine, cocaine, caffeine, morphine, papaverine, pilocarpine, platifillin, reserpine, salsolin, securine, strychnine, quinine, cytisine, ephedrine, etc. Most of these drugs are obtained in the result of searches based on chemical screening. However, the one-sided development of this method, which in many institutes and laboratories has been reduced to the search for only alkaloid-bearing plants, is alarming. We must not forget that, in addition to alkaloids, new biologically active plant substances belonging to other classes of chemical compounds are identified annually. If before 1956 the structure of only 2669 natural compounds from plants that were not related to alkaloids was known, then in the next 5 years (1957-1961) another 1754 individual organic substances were found in plants. Now the number of chemical substances with an established structure reaches 7,000, which together with alkaloids makes up over 12,000 plant substances. Chemical screening slowly coming out of the "alkaloid period". Of the 70 groups and classes of plant substances currently known (Karrer et. al., 1977), it is carried out only in 10 classes of compounds, because there are no reliable and fast express methods for determining the presence of other compounds in plant materials. Involvement in chemical screening of new classes of biologically active compounds is an important reserve for increasing the pace and efficiency of the search for new drugs from plants. It is very important to develop methods for the rapid search for individual chemicals, for example, berberine, rutin, ascorbic acid, morphine, cytisine, etc. Secondary compounds, or so-called substances of specific biosynthesis, are of greatest interest in the creation of new therapeutic drugs. Many of them have a wide range biological activity. For example, alkaloids are approved for use in medical practice as analeptics, analgesics, sedatives, hypotensive, expectorant, choleretic, antispasmodic, uterine, tonic central nervous system and adrenaline-like drugs. Flavonoids are able to strengthen the walls of capillaries, lower the tone of the smooth muscles of the intestine, stimulate the secretion of bile, increase the neutralizing function of the liver, some of them have antispasmodic, cardiotonic and antitumor effects. Many polyphenolic compounds are used as antihypertensive, antispasmodic, antiulcer, choleretic and antibacterial agents. Antitumor activity was noted in cyanides (for example, contained in peach seeds, etc.), triterpene ketones, diterpenoids, polysaccharides, alkaloids, phenolic and other compounds. More and more drugs are created from cardiac glycosides, amino acids, alcohols, coumarins. polysaccharides, aldehydes, sesquiterpene lactones, steroid compounds. Often, long-known chemical substances find medical use, in which it was only recently possible to discover one or another medical and biological activity and develop a rational method for manufacturing drugs. Chemical screening allows not only to identify new promising objects for study, but also: - identify correlations between systematic position plants, its chemical composition and biomedical activity;
- find out the geographical and environmental factors that promote or hinder the accumulation of certain active substances in plants;
- to determine the significance of biologically active substances for the plants producing them;
- to identify chemical races in plants that are hereditarily different from each other in the presence of certain active substances.
Study of plant organs
Different plant organs often differ not only in the quantitative content of active substances, but also in their qualitative composition. For example, the alkaloid sinomenin is found only in the herb of Daurian moonseed, and cytisine is found only in the fruits of the lanceolate thermopsis, being absent in its terrestrial parts until the end of flowering plants, while in the thermopsis of the alternate-flowered cytisine in in large numbers contained in the aerial parts in all phases of plant development. That is why, in order to get the full picture chemical composition each plant needs to be analyzed at least four of its organs: underground (roots, rhizomes, bulbs, tubers), leaves and stems (in herbs, leaves are always richer in active substances than stems), flowers (or inflorescences), fruits and seeds. In woody-shrub plants, active substances often accumulate in the bark of the stems (and roots), and sometimes only in seedlings, some parts of the flower, fruit and seed.
The chemical composition of each plant organ also varies significantly in different phases of its development. The maximum content of some substances is observed in budding phase, others - in full bloom phase, third - during fruiting and others. For example, the alkaloid triacanthin is found in significant quantities only in the blossoming leaves of the three-prickly locust, while in other phases of development it is practically absent in all organs of this plant. Thus, it is easy to calculate that in order to identify, for example, only complete list of alkaloid-bearing plants of the flora of the USSR, numbering about 20,000 species, it is necessary to make at least 160,000 analyzes (20,000 species X 4 organs X 2 phases of development), which will require about 8000 days of work of 1 laboratory assistant-analyst. Approximately the same amount of time must be spent to determine the presence or absence of flavonoids, coumarins, cardiac glycosides, tannins, polysaccharides, triterpene glycosides, and every other class of chemical compounds in all plants of the flora of the USSR, if analyzes are carried out without preliminary culling of plants for one reason or another. In addition, the same organs in the same phase of plant development in one region may have the necessary active substances, while in another region they may not. In addition to geographical and environmental factors (the influence of temperature, humidity, insolation, etc.), the presence of special chemical races in a given plant, which are completely indistinguishable by morphological features, may affect here. All this greatly complicates the task and, it would seem, makes the prospects for completing the preliminary chemical assessment of the flora of the USSR, and even more so of the entire globe, very remote. However, knowledge of certain patterns can greatly simplify this work. First, it is not necessary to examine all organs in all phases of development. It is enough to analyze each organ in the optimal phase, when it contains the largest amount of the test substance. For example, previous studies have established that leaves and stems are richest in alkaloids in the budding phase, bark - during the spring sap flow, and flowers - in the phase of their full blooming. Fruits and seeds, however, may contain different alkaloids and in different quantities in the mature and unripe state, and therefore, if possible, they should be examined twice. Knowledge of these regularities greatly simplifies the preliminary chemical evaluation of plants. Complete examination of all types- the method is effective, but still it is blind work! Is it possible, without carrying out even the simplest chemical analysis, to distinguish groups of plants that presumably contain one or another class of chemical compounds from those that obviously do not contain these substances? In other words, is it possible to determine the chemical composition of plants by eye? As will be discussed in the next section of our brochure, in general terms we can answer this question in the affirmative. 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
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, mainly biochemical systematics has become increasingly important, 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).
Since botany studies quite a lot of different aspects of the organization and functioning of plant organisms, in each specific case, its own set of research methods is used. Botany uses both general methods (observation, comparison, analysis, experiment, generalization) and many
special methods (biochemical and cytochemical methods, light methods (conventional, phase-contrast, interference, polarization, fluorescence, ultraviolet) and electron (transmission, scanning) microscopy, cell culture methods, microscopic surgery, molecular biology methods, genetic methods, electrophysiological methods, freezing and chipping methods, biochronological methods, biometric methods, mathematical modeling, statistical methods).
Special methods take into account the peculiarities of one or another level of organization of the plant world. So, to study the lower levels of organization, various biochemical methods, methods of qualitative and quantitative chemical analysis are used. Various cytological methods are used to study cells, especially electron microscopy methods. To study tissues and the internal structure of organs, methods of light microscopy, microscopic surgery, and selective staining are used. Various genetic, geobotanical and ecological research methods are used to study the flora at the population-species and biocenotic levels. In plant taxonomy, an important place is occupied by such methods as comparative morphological, paleontological, historical, and cytogenetic methods.
The assimilation of material from different sections of botany is theoretical basis in the training of future specialists in agricultural chemists-soil scientists. Due to the inextricable relationship between the plant organism and the environment of its existence, the morphological features and internal structure of the plant are largely determined by the characteristics of the soil. At the same time, the direction and intensity of the course of physiological and biochemical processes also depend on the chemical composition of the soil and its other properties, which ultimately determines the increase in plant biomass and the productivity of crop production as an industry as a whole. So botanical knowledge make it possible to substantiate the need and doses of applying various substances to the soil, to influence the yield of cultivated plants. In fact, any impact on the soil in order to increase the yield of cultivated and wild plants is based on data obtained in various branches of botany. The methods of biological control of plant growth and development are based almost entirely on botanical morphology and embryology.
In turn, the plant world is an important factor in soil formation and determines many properties of the soil. Each type of vegetation is characterized by certain types of soils, and these patterns are successfully used for mapping soils. Plant species and their individual systematic groups can be reliable phytoindicators of food (ground) conditions. Indicator geobotany gives soil scientists and agrochemists one of the important methods for assessing the quality of soils, their physicochemical and chemical properties,
Botany is the theoretical basis of agricultural chemistry, as well as applied areas such as crop production and forestry. About 2,000 plant species have now been introduced into cultivation, but only an insignificant part of them is widely grown. Many wild-growing species of flora can become very promising crops in the future. Botany substantiates the possibility and expediency of agricultural development of natural areas, carrying out land reclamation measures to increase the productivity of natural plant groups, in particular meadows and forests, promotes the development and rational use of plant resources on land, fresh water bodies and the World Ocean.
For specialists in the field of agrochemistry and soil science, botany is the basic basis, which allows a deeper understanding of the essence of soil-forming processes, to see the dependence of certain soil properties on the characteristics of the vegetation cover, and to understand the needs of cultivated plants for specific nutrients.