Table of contents:
- Nitrogen compounds of non-protein nature
- Non-protein nitrogen
- Cellulose, or fiber
- Pectin substances
- Fats and fat-like substances, so-called lipids and lipoids
Video: How Fertilizers Affect The Quality Of The Crop - 2
Nitrogen compounds of non-protein nature
In addition to proteins, plants always contain nitrogenous compounds of non-protein nature, the sum of which is often called "non-protein nitrogen - crude protein". This fraction includes mineral nitrogen compounds - nitrates and ammonia - as well as organic non-protein substances - free amino acids and amides. Among the organic nitrogenous substances in plant tissues are peptides, which are small "amino acid residues".
Important organic nitrogenous substances are basic compounds - pyrimidine and purine derivatives. They are called pyrimidine and purine bases. These are the basic building blocks that make up nucleic acid molecules. All this non-protein nitrogen in the leaves of most plants makes up 10-25% of the total protein content. In cereal seeds, non-protein nitrogen compounds are usually about 1% by weight of seeds, or 6-10% of the amount of proteins. In seeds of legumes and oilseeds, the share of non-protein nitrogen accounts for 2-3% of the weight of seeds, or about 10% of the protein content. Most of the non-protein nitrogenous substances are found in potato tubers, root crops and other vegetable crops.
In potato tubers, non-protein nitrogenous substances on average account for about 1% of the weight of tubers, that is, they contain about the same amount as proteins, and with an increased level of nitrogen nutrition, there may be more non-protein nitrogen compounds than proteins. In the roots of beets, carrots and other crops, the content of non-protein nitrogen compounds is also approximately equal to the content of proteins and averages 0.5-0.8% of the weight of root crops.
It is well absorbed by the human body and has a fairly high biological value. Fertilizers significantly increase the content of both protein and non-protein nitrogen in the crop, therefore, great attention is paid to increasing the amount of all fractions.
The second most important group of chemicals for which many crops are grown are carbohydrates. The most important of them are sugars, starch, cellulose and pectin substances.
In plant tissues, they accumulate in large quantities as reserve substances. They are dominated by monosaccharides - glucose and fructose - and a disaccharide - sucrose. Sometimes plants in a free state contain a noticeable amount of five-carbon sugars - pentoses.
Contained in almost any living plant cell. In many fruits and berries, it accumulates in a free state in significant quantities and determines their sweet taste. In beets and other root vegetables, despite the high total sugar content, the amount of glucose is small and rarely exceeds 1%. Glucose is also found in many disaccharides, trisaccharides, starch, fiber, glycosides and other compounds. In a living organism, glucose is the main respiratory material and, therefore, the most important source of energy.
Contained in many sweet fruits in amounts up to 6-10%. In vegetables, the fructose content is very low, not more than tenths of a percent. It is part of sucrose and many polyfructosides, of which inulin is the most abundant. It accumulates as a reserve substance (up to 10-12%) in the roots of Jerusalem artichoke (earthen pear), dahlias, chicory and some other plants.
Compared with other sugars, it is of the greatest economic importance, since it serves as the main sugar used in the nutrition of the population. Sucrose is built from residues of glucose and fructose molecules. Fruits and berries are distinguished by its higher content, there is a lot of it in the roots of beets (14-22%). Very important compounds in plants are the phosphoric esters of sugars (mainly hexose and pentose), which are sugar compounds with a phosphoric acid residue. Such important processes as photosynthesis, respiration, synthesis of complex carbohydrates from simpler ones, mutual transformations of sugars and other processes occur in plants with the obligatory participation of phosphorus esters of sugars. Therefore, the applied phosphorus fertilizers significantly change the quality of the crop, increasing the content of easily mobile carbohydrates - glucose, fructose and sucrose.
It is mainly a storage polysaccharide found in green leaves, but the main organs in which it is located are seeds and tubers. Starch is not a homogeneous substance, but a mixture of two different polysaccharides - amylose and amylopectin, which differ in chemical and physical properties. Starch contains 15-25 and 75-85%, respectively. Amylose dissolves in water without the formation of a paste, gives a blue coloration with iodine. Amylopectin gives a violet color with iodine, with hot water it forms a paste. The starch content in the crop is highly dependent on the application of phosphorus and potash fertilizers.
The largest amount of starch accumulates in the seeds of rice (70-80%), corn (60-75%) and other cereals. The starch content in the seeds of leguminous crops is low, and in the seeds of oilseeds it is almost absent. There is a lot of starch in potato tubers: in early varieties - 10-14%, medium-late and late varieties - 16-22% of the tuber weight. Depending on the growing conditions of plants and, above all, on fertilizers, the starch content can vary significantly. Starch is very well absorbed by the human body and is easily converted in plants into other easily mobile carbohydrates. Its decomposition occurs under the action of a group of enzymes called amylases.
Cellulose, or fiber
It is the main part of the plant cell walls. Pure cellulose is a white, fibrous substance. In seeds of leguminous crops, cellulose is 3-5%, in potato tubers and root crops - about 1%. There is a lot of cellulose in cotton, flax, hemp, jute, which are grown mainly for the production of filamentary cellulose fibers. Cellulose is not assimilated by the human body and serves as a ballast, but ensures better bowel function, promotes the removal of heavy metals from the body. With the complete hydrolysis of fiber (this occurs in the body of ruminants) glucose is formed.
Widespread in plants, they are capable of forming jelly or jellies in the presence of acid and sugar. In the greatest amount (up to 1-2% of the tissue weight), they are found in root crops, fruits and berries. The content of cellulose and pectin substances (insoluble forms of carbohydrates) in the crop can also be controlled with the help of fertilizers, mainly by changing the ratio between the applied elements.
Fats and fat-like substances, so-called lipids and lipoids
They play a very important role in the life of plants, since they are structural components of the cytoplasm of cells, and in many plants, in addition, they play the role of reserve substances. Cytoplasmic fats and complexes of lipoids with proteins - lipoproteins - are included in all organs and tissues of plants - in leaves, stems, fruits, roots; their content is 0.1-0.5%. Plants that accumulate a large amount of fat in the seeds and in which it is the main reserve substance are called oil plants. The fat content in sunflower seeds is 26-45%, flax - 34-48%, hemp - 30-38%, poppy - 50-60%, goat's rue and amaranth - 30-40%, in sea buckthorn fruits - up to 20%. The variability of the fat content in seeds depends on the varietal characteristics of the crop, climatic, soil conditions and applied fertilizers.
The nutritional value of vegetable fats is not lower than that of animal fats. In addition, when determining the nutritional value of fats, it should be borne in mind that linoleic and linolenic acids, which are part of their composition, are contained only in vegetable oils. They are "irreplaceable" for a person, since they cannot be synthesized in his body, but they are necessary for normal life.
Vitamins in the human body cannot be synthesized, and in their absence or deficiency, serious diseases develop. In plants, vitamins are closely related to enzymes. About 40 different vitamins are now known. A lack of ascorbic acid (vitamin C) in food leads to a serious illness called scurvy. To prevent it, a person should receive 50-100 mg of ascorbic acid with food per day.
Thiamine (vitamin B1) is indispensable in metabolic processes in plants and animals, since in the form of phosphoric ether it is included in a number of enzymes that catalyze the transformation of many compounds. With a lack of thiamine in human food, polyneuritis occurs. Riboflavin (vitamin B2) is a component of many redox enzymes.
The daily human need for it is 2-3 mg. Most of this vitamin is found in yeast, cereal grains and in some vegetables. Pyridoxine (vitamin B6) plays an important role in metabolic processes, especially in nitrogen metabolism: it is part of enzymes that catalyze many amino acid metabolism reactions, including such an important reaction as their transamination.
Tocopherol (vitamin E) is a group of substances with high activity. With a lack of vitamin E in a person, the metabolism of proteins, lipids, carbohydrates is disturbed, the genitals are affected and the ability to reproduce is lost. Retinol (vitamin A) protects humans and animals from xerophthalmia, inflammation of the cornea of the eyes and "night blindness".
Plants do not contain vitamin A, but they contain substances with A-vitamin activity. These include carotenoids - yellow or red pigments. The most important among them is carotene, which, along with chlorophyll, is always found in green leaves, in many flowers and fruits. Carotenoids are of great importance in the processes of photosynthesis, plant reproduction and in redox systems. Carotene in the human body is easily converted to vitamin A.
Several compounds with K-vitamin activity are known, they are necessary for normal blood coagulation, with their lack, the blood coagulation rate decreases sharply, and sometimes death from internal hemorrhages is observed. In plants, vitamins of the K group are involved in redox processes and, in particular, in the process of photosynthesis.
Vitamin K is synthesized in green parts of plants, which are richer in this vitamin compared to seeds. Good plant nutrition through fertilization significantly increases the vitamin content of the crop.