Characteristics of biochemical adaptation. Biochemical features of the relationship between the organism and the environment. Institute of Mathematics, Natural Sciences and Information Technologies
In the process of evolution, as a result of natural selection and the struggle for existence, adaptations of organisms to certain living conditions arise. Evolution itself is essentially a continuous process of formation of adaptations, occurring according to the following scheme: intensity of reproduction -> struggle for existence -> selective death -> natural selection -> fitness.
Adaptations affect different aspects of the life processes of organisms and therefore can be of several types.
Morphological adaptations
They are associated with changes in body structure. For example, the appearance of membranes between the toes in waterfowl (amphibians, birds, etc.), thick fur in northern mammals, long legs and a long neck in wading birds, a flexible body in burrowing predators (for example, weasels), etc. In warm-blooded animals, when moving north, an increase in average body size is observed (Bergmann's rule), which reduces the relative surface area and heat transfer. Benthic fish develop a flat body (rays, flounder, etc.). Plants in northern latitudes and high mountain regions often have creeping and cushion-shaped forms, which are less damaged by strong winds and better warmed by the sun in the soil layer.
Protective coloration
Protective coloration is very important for animal species that do not have effective means of protection against predators. Thanks to it, animals become less noticeable in the area. For example, female birds hatching eggs are almost indistinguishable from the background of the area. Bird eggs are also colored to match the color of the area. Bottom-dwelling fish, most insects and many other animal species have a protective coloration. In the north, white or light coloring is more common, helping to camouflage in the snow (polar bears, polar owls, arctic foxes, baby pinnipeds - squirrels, etc.). A number of animals have acquired a coloration formed by alternating light and dark stripes or spots, making them less noticeable in bushes and dense thickets (tigers, young wild boars, zebras, sika deer, etc.). Some animals are capable of changing color very quickly depending on conditions (chameleons, octopuses, flounder, etc.).
Disguise
The essence of camouflage is that the shape of the body and its color make animals look like leaves, twigs, branches, bark or thorns of plants. Often found in insects that live on plants.
Warning or threatening coloring
Some types of insects that have poisonous or odorous glands have bright warning colors. Therefore, predators that once encounter them remember this coloring for a long time and no longer attack such insects (for example, wasps, bumblebees, ladybugs, Colorado potato beetles and a number of others).
Mimicry
Mimicry is the coloring and body shape of harmless animals that imitate their poisonous counterparts. For example, some non-venomous snakes resemble venomous ones. Cicadas and crickets resemble large ants. Some butterflies have large spots on their wings that resemble the eyes of predators.
Physiological adaptations
This type of adaptation is associated with a restructuring of metabolism in organisms. For example, the appearance of warm-bloodedness and thermoregulation in birds and mammals. In simpler cases, this is an adaptation to certain forms of food, the salt composition of the environment, high or low temperatures, humidity or dryness of soil and air, etc.
Biochemical adaptations
Behavioral adaptations
This type of adaptation is associated with changes in behavior in certain conditions. For example, caring for offspring leads to better survival of young animals and increases the stability of their populations. During mating seasons, many animals form separate families, and in winter they unite in flocks, which makes it easier for them to feed or protect (wolves, many species of birds).
Adaptations to periodic environmental factors
These are adaptations to environmental factors that have a certain periodicity in their manifestation. This type includes daily alternations of periods of activity and rest, states of partial or complete anabiosis (shedding of leaves, winter or summer diapauses of animals, etc.), animal migrations caused by seasonal changes, etc.
Adaptations to extreme living conditions
Plants and animals living in deserts and polar regions also acquire a number of specific adaptations. In cacti, the leaves have been transformed into spines (reducing evaporation and protecting them from being eaten by animals), and the stem has turned into a photosynthetic organ and reservoir. Desert plants have long root systems that allow them to obtain water from great depths. Desert lizards can survive without water by eating insects and obtaining water by hydrolyzing their fats. In addition to thick fur, northern animals also have a large supply of subcutaneous fat, which reduces body cooling.
Relative nature of adaptations
All devices are appropriate only for certain conditions in which they were developed. If these conditions change, adaptations may lose their value or even cause harm to the organisms that have them. The white coloration of hares, which protects them well in the snow, becomes dangerous during winters with little snow or severe thaws.
The relative nature of adaptations is well proven by paleontological data, which indicates the extinction of large groups of animals and plants that did not survive the change in living conditions.
The evolution of adaptation is the main result of the action of natural selection. Classification of adaptation: morphological, physiological-biochemical, ethological, species adaptations: congruence and cooperation. The relativity of organic expediency.
Answer: Adaptation is any feature of an individual, population, species or community of organisms that contributes to success in competition and provides resistance to abiotic factors. This allows organisms to exist in given environmental conditions and leave offspring. The adaptation criteria are: vitality, competitiveness and fertility.
Types of adaptation
All adaptations are divided into accommodation and evolutionary adaptations. Accommodation is a reversible process. They occur when environmental conditions suddenly change. For example, when relocating animals find themselves in a new environment, but gradually get used to it. For example, a person who moved from the middle zone to the tropics or the Far North experiences discomfort for some time, but over time gets used to the new conditions. Evolutionary adaptation is irreversible and the resulting changes are genetically fixed. This includes all adaptations that are affected by natural selection. For example, protective coloring or fast running.
Morphological adaptations manifest themselves in structural advantages, protective coloration, warning coloration, mimicry, camouflage, adaptive behavior.
The advantages of the structure are the optimal proportions of the body, the location and density of hair or feathers, etc. The appearance of an aquatic mammal, the dolphin, is well known.
Mimicry is the result of homologous (identical) mutations in different types, which help unprotected animals survive.
Camouflage - devices in which the body shape and color of animals merge with surrounding objects
Physiological adaptations- acquisition of specific metabolic features in different environmental conditions. They provide functional benefits to the body. They are conventionally divided into static (constant physiological parameters - temperature, water-salt balance, sugar concentration, etc.) and dynamic (adaptation to fluctuations in the action of a factor - changes in temperature, humidity, light, magnetic field, etc.). Without such adaptation, it is impossible to maintain a stable metabolism in the body in constantly fluctuating environmental conditions. Let's give some examples. In terrestrial amphibians, large amounts of water are lost through the skin. However, many of their species penetrate even into deserts and semi-deserts. The adaptations that develop in diving animals are very interesting. Many of them can survive for a relatively long time without access to oxygen. For example, seals dive to a depth of 100-200 and even 600 meters and stay under water for 40-60 minutes. The chemical sense organs of insects are amazingly sensitive.
Biochemical adaptations ensure the optimal course of biochemical reactions in the cell, for example, the ordering of enzymatic catalysis, the specific binding of gases by respiratory pigments, the synthesis of necessary substances under certain conditions, etc.
Ethological adaptations represent all behavioral responses aimed at the survival of individuals and, therefore, the species as a whole. Such reactions are:
Behavior when searching for food and a sexual partner,
Pairing,
Feeding offspring
Avoiding danger and protecting life in the event of a threat,
Aggression and threatening postures,
Kindness and many others.
Some behavioral reactions are inherited (instincts), others are acquired throughout life (conditioned reflexes).
Species adaptations are discovered when analyzing a group of individuals of the same species; they are very diverse in their manifestation. The main ones are various congruences, the level of mutability, intraspecific polymorphism, the level of abundance and optimal population density.
Congruences represent all the morphophysiological and behavioral features that contribute to the existence of the species as an integral system. Reproductive congruences ensure reproduction. Some of them are directly related to reproduction (correspondence of genital organs, adaptations to feeding, etc.), while others are only indirect (various signal signs: visual - mating attire, ritual behavior; sound - birdsong, roar of a male deer during the rut and etc.; chemical - various attractants, for example, insect pheromones, secretions from artiodactyls, cats, dogs, etc.).
Congruences include all forms of intraspecific cooperation- constitutional, trophic and reproductive. Constitutional cooperation is expressed in the coordinated actions of organisms in unfavorable conditions, which increase the chances of survival. In winter, bees gather in a ball, and the heat they generate is spent on joint warming. In this case, the highest temperature will be in the center of the ball and individuals from the periphery (where it is colder) will constantly strive there. In this way, the insects constantly move and, through joint efforts, they survive the winter safely. Penguins also cluster in a close group during incubation, sheep during cold weather, etc.
Trophic cooperation consists of uniting organisms for the purpose of obtaining food. Joint activity in this direction makes the process more productive. For example, a pack of wolves hunts much more efficiently than an individual. At the same time, in many species there is a division of responsibilities - some individuals separate the chosen victim from the main herd and drive it into ambush, where their relatives are hiding, etc. In plants, such cooperation is expressed in joint shading of the soil, which helps retain moisture in it.
Reproductive cooperation increases the success of reproduction and promotes the survival of offspring. In many birds, individuals gather on lekking grounds, and in such conditions it is easier to find a potential partner. The same thing happens at spawning grounds, rookeries of pinnipeds, etc. The likelihood of pollination in plants increases when they grow in groups and the distance between individual individuals is small.
The Law of Organic Purpose, or Aristotle's Law
1. The deeper and more versatile science studies living forms, the more fully they are revealed expediency, that is, the purposeful, harmonious, seemingly reasonable nature of their organization, individual development and relationship with the environment. Organic expediency is revealed in the process of understanding the biological role of specific features of living forms.
2. Expediency is inherent in all types. It is expressed in the subtle mutual correspondence of the structures and purpose of biological objects, in the adaptability of living forms to living conditions, in natural focus features of individual development, in the adaptive nature of the forms of existence and behavior of biological species.
3. Organic expediency, which became the subject of analysis of ancient science and served as the basis for teleological and religious interpretations of living nature, received a materialistic explanation in Darwin’s teaching about creative role natural selection, manifested in the adaptive nature of biological evolution.
This is the modern formulation of those generalizations, the origins of which go back to Aristotle, who put forward ideas about final causes.
The study of specific manifestations of organic expediency is one of the most important tasks of biology. Having found out what this or that feature of the biological object under study is for, what is the biological significance of this feature, thanks to Darwin’s evolutionary theory, we are getting closer to answering the question of why and how it arose. Let us consider the manifestations of organic expediency using examples related to various areas of biology.
In the field of cytology, a striking, clear example of organic expediency is cell division in plants and animals. The mechanisms of equational (mitosis) and reduction (meiosis) division determine the constancy of the number of chromosomes in the cells of a given plant or animal species. Doubling the diploid set in mitosis ensures that the number of chromosomes in dividing somatic cells remains constant. Haploidization of the chromosome set during the formation of germ cells and its restoration during the formation of a zygote as a result of the fusion of germ cells ensure the preservation of the number of chromosomes during sexual reproduction. Deviations from the norm, leading to polyploidization of cells, i.e., to a multiplication of the number of chromosomes against the normal one, are cut off by the stabilizing effect of natural selection or serve as a condition for genetic isolation, isolation of the polyploid form with its possible transformation into a new species. In this case, cytogenetic mechanisms come into play again, causing the preservation of the chromosome set, but at a new, polyploid level.
In the process of individual development of a multicellular organism, the formation of cells, tissues and organs for various functional purposes occurs. The correspondence of these structures to their purpose, their interaction in the process of development and functioning of the body are characteristic manifestations of organic expediency.
A wide range of examples of organic feasibility are represented by devices for the reproduction and distribution of living forms. Let's name some of them. For example, bacterial spores are highly resistant to unfavorable environmental conditions. Flowering plants are adapted to cross-pollination, particularly with the help of insects. The fruits and seeds of a number of plants are adapted for dispersal by animals. Sexual instincts and instincts of caring for offspring are characteristic of animals at various levels of organization. The structure of caviar and eggs ensures the development of animals in the appropriate environment. The mammary glands provide adequate nutrition for the offspring of mammals.
Modern concepts of the species. The reality of existence and the biological significance of species.
Answer: A species is one of the main forms of organization of life on Earth and the basic unit of classification of biological diversity. The diversity of modern species is enormous. According to various estimates, about 2-2.5 million species (up to 1.5-2 million animal species and up to 500 thousand plant species) currently live on Earth. The process of describing new species continues continuously. Every year hundreds and thousands of new species of insects and other invertebrate animals and microorganisms are described. The distribution of species among classes, families and genera is very uneven. There are groups with a huge number of species and groups - even of high taxonomic rank - represented by a few species in the modern fauna and flora. For example, an entire subclass of reptiles is represented by only one species - the hatteria.
At the same time, modern species diversity is significantly less than the number of extinct species. Due to human economic activity, a huge number of species become extinct every year. Since the conservation of biodiversity is an indispensable condition for the existence of humanity, this problem is becoming global today. C. Linnaeus laid the foundations of modern taxonomy of living organisms (System of Nature, 1735). K. Linnaeus established that within a species, many essential characteristics change gradually, so that they can be arranged in a continuous series. K. Linnaeus considered species as objectively existing groups of living organisms, quite easily distinguishable from each other.
Biological concept of species. The biological concept was formed in the 30s-60s of the XX century. based on the synthetic theory of evolution and data on the structure of species. It is most fully developed in Mayr's book “Zoological Species and Evolution” (1968). Mayr formulated the biological concept in the form of three points: species are determined not by differences, but by isolation; species do not consist of independent individuals, but of populations; Species are defined based on their relationship to populations of other species. The decisive criterion is not fertility during crossing, but reproductive isolation.” Thus, according to the biological concept A species is a group of actually or potentially interbreeding populations that are reproductively isolated from other similar populations. This concept is also called polytypic. The positive side of the biological concept is its clear theoretical basis, well developed in the works of Mayr and other proponents of this concept. However, this concept is not applicable to species that reproduce sexually and in paleontology. The morphological concept of the species was formed on the basis of a typological one, more precisely, on the basis of a multidimensional polytypic species. At the same time, it represents a step forward compared to these concepts. According to her, the species is a set of individuals that have hereditary similarity in morphological, physiological and biochemical characteristics, freely interbreed and produce fertile offspring, adapted to certain living conditions and occupying a certain area in nature - habitat. Thus, in modern literature, mainly two concepts of the form are discussed and applied: biological and morphological (taxonomic).
The reality of existence and biological significance of species.
For objects of biological science to exist means to have the subject-ontological characteristics of biological reality. Based on this, the problem of the existence of a gene, species, etc. “is resolved in the language of this level by constructing appropriate experimental and “observational” techniques, hypotheses, concepts that assume these entities as elements of their objective reality.” Biological reality was formed taking into account the existence of various levels of “living”, which represents a complex hierarchy of the development of biological objects and their connections.
Biological diversity is the main source of satisfaction for many human needs and serves as the basis for its adaptation to changing conditions environment. The practical value of biodiversity is that it is an essentially inexhaustible source of biological resources. These are primarily food products, medicines, sources of raw materials for clothing, production of building materials, etc. Biodiversity is of great importance for human recreation.
Biodiversity provides genetic resources for agriculture, constitutes the biological basis for global food security and is a necessary condition for the existence of humanity. A number of wild plants related to crops are of great economic importance at the national and global levels. For example, Ethiopian varieties of Californian barley provide protection against pathogenic viruses, in monetary terms amounting to $160 million. USA per year. Genetic disease resistance achieved using wild wheat varieties is estimated at $50 million in Turkey
Many animals and plants are capable of producing various substances that serve them to protect themselves from enemies and to attack other organisms. The smelly substances of bedbugs, the venoms of snakes, spiders, scorpions, and plant toxins are classified as such devices.
Biochemical adaptations also include the appearance of a special structure of proteins and lipids in organisms living at very high or low temperatures. Such features allow these organisms to exist in hot springs or, conversely, in permafrost conditions.
Rice. 28. Hoverflies on flowers 
Rice. 29. Chipmunk hibernating
Physiological adaptations. These adaptations are associated with metabolic restructuring. Without them, it is impossible to maintain homeostasis in constantly changing environmental conditions.
A person cannot do without fresh water for a long time due to the peculiarities of his salt metabolism, but birds and reptiles, spending most of their lives in the sea and drinking sea water, have acquired special glands that allow them to quickly get rid of excess salts.
Many desert animals accumulate a lot of fat before the onset of the dry season: when it oxidizes, a large amount of water is formed.
Behavioral adaptations. Special type behavior in certain conditions is very important for survival in the struggle for existence. Hiding or frightening behavior when an enemy approaches, storing food for an unfavorable period of the year, hibernation of animals and seasonal migrations that allow them to survive a cold or dry period - this is not a complete list of various types of behavior that arise during evolution as adaptations to specific living conditions (Fig. 29).
Rice. 30. Mating tournament of male antelope
It should be noted that many types of adaptations are formed in parallel. For example, the protective effect of protective or warning coloring is greatly enhanced when combined with appropriate behavior. Animals with a protective coloring freeze in a moment of danger. Warning coloration, on the contrary, is combined with demonstrative behavior that scares away predators.
Of particular importance are behavioral adaptations associated with procreation. Marital behavior, choice of a partner, family formation, caring for offspring - these types of behavior are innate and species-specific, i.e., each species has its own program of sexual and child-parent behavior (Fig. 30-32).
Adaptation is a set of processes in the body that shape its resistance to changed conditions of existence. Depending on the level of adaptive reactions, physiological (systemic) and biochemical (cellular) adaptation can be distinguished.
Physiological adaptation is associated with the restructuring of the activity of systemic functions of the body (for example, blood circulation, respiration, nervous system, etc.), which allows maintaining the constancy of the internal environment of the body and facilitating the activity of organs and tissues, improving their supply of nutrients and oxygen, accelerating the removal of waste products .
Cells, being part of the body, have their own mechanisms for restructuring metabolism, based on changes in the course of biochemical reactions inside the cells.
The two types of adaptation are closely interrelated and enable the body to adapt to unfavorable conditions.
Adaptation is associated with regulation, since metabolism can be directed in the right direction only with the help of a system of extracellular regulators. Biochemical adaptation and regulation can be immediate and long-term.
Urgent adaptation is associated with a rapid restructuring of metabolism that occurs at the beginning of a critical situation. Moreover, all changes in metabolism are caused by the inclusion of urgent mechanisms for the regulation of cellular metabolism, namely the effect of neuro-hormonal stimuli on the permeability of cell membranes and enzyme activity.
If immediate adaptation is aimed at the survival of the cell, then long-term adaptation is aimed at preserving its viability under unfavorable conditions. During long-term adaptation, the restructuring of metabolism is due to the inclusion of long-term regulatory mechanisms, i.e. the influence of neurohormonal stimuli on the synthesis of enzymes and other functional proteins that provide a different type of metabolism corresponding to changed conditions.
If for some reason neurohormonal regulation is disrupted, then the body cannot adapt to the prevailing environmental conditions for a long time, which manifests itself in the form of diseases of adaptation and acclimatization.
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Preface | |
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Introduction | |
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Subject and tasks of biochemistry | |
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Research methods | |
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Basic signs of living matter | |
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Chapter 1. CHEMICAL COMPOSITION OF ORGANISMS | |
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Chapter 2. STRUCTURE AND PROPERTIES OF PROTEINS | |
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2.1. The role of proteins in the construction of living matter. Determination of proteins | |
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2.2. Elemental composition of proteins. Protein content in organs and tissues | |
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2.3. Amino acid composition of proteins | |
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2.4. Acid-base properties of amino acids | |
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2.5. Stereochemistry of amino acids | |
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2.6. Protein structure | |
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2.7. Levels structural organization proteins | |
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Primary structure of proteins | |
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Secondary structure of proteins | |
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Tertiary structure of proteins | |
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Quaternary structure of proteins | |
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2.8. Denaturation and renaturation | |
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2.9. Determination of molecular weight of proteins | |
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2.10. Physicochemical properties of proteins | |
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Acid-base and buffering properties of proteins | |
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Protein hydration and factors affecting their solubility | |
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2.11. Functions of proteins in the body | |
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2.12. Methods for protein isolation and purification | |
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Selection methods | |
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Protein purification, protein homogeneity assessment | |
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2.13. Protein classification | |
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Chapter 3. CARBOHYDRATES | |
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3.1. The concept of carbohydrates and their classification | |
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3.2. Monosaccharides | |
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Optical properties of monosaccharides | |
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Monosaccharide structure | |
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3. 3 Basic reactions of monosaccharides | |
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Reactions involving a carbonyl group | |
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Reactions involving hydroxyl groups | |
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3.4. Complex carbohydrates | |
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Oligosaccharides | |
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Polysaccharides | |
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3.5. Biological functions of carbohydrates | |
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Chapter 4. NUCLEIC ACIDS | |
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4.1. general characteristics nucleic acids | |
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4.2. Chemical composition and structure of nucleic acids | |
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4.3. Levels of structural organization nucleic acids | |
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Primary structure of nucleic acids | |
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Secondary structure of DNA | |
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Secondary structure of RNA | |
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Tertiary structure of RNA and DNA | |
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Chapter 5. LIPIDS | |
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5 1. General characteristics and classification of lipids | |
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5.2. Lipid monomers | |
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5.3. Multicomponent lipids | |
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5. 4. Biological functions of lipids | |
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Chapter 6. ENZYMES | |
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6.1. Methods for isolating and purifying enzymes | |
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6.2. Chemical nature and enzyme structure | |
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6.Z. Enzyme cofactors | |
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Metal ions as enzyme cofactors | |
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Coenzymes | |
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6.4. Mechanism of action of enzymes | |
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6.5. Properties of enzymes | |
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6. 6. Specificity of enzyme action | |
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7.7. Factors affecting the rate of enzymatic catalysis | |
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Effect of temperature on enzyme activity | |
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Effect of pH on enzyme activity | |
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Effect of substrate and enzyme concentrations on the rate of enzymatic reaction | |
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Dependence of reaction speed on time | |
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6.8. Regulation of enzyme activity | |
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Enzyme activation | |
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Enzyme inhibition | |
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Allosteric regulation of enzyme action | |
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6.9. Determination of enzyme activity | |
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6.10. Nomenclature and classification of enzymes | |
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6.11. Localization of enzymes in the body and cell | |
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6.12. Application of enzymes | |
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Chapter 7. VITAMINS | |
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7.1. Concept of vitamins | |
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7.2. Classification of vitamins | |
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7.3. Fat-soluble vitamins | |
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Vitamin A (retinol) | |
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Vitamin D (calciferol) | |
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Vitamin E (tocopherols) | |
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Vitamin K (naphthoquinones) | |
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7.4. Water-soluble vitamins | |
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Vitamin B 1 (thiamine) | |
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Vitamin B 2 (riboflavin) | |
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Vitamin B 3 (pantothenic acid) | |
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Vitamin B 5 (PP, niacin, nicotinamide, nicotinic acid) | |
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Vitamin B 6 (pyridoxine) | |
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Vitamin B 9 (B c, folic acid) | |
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Vitamin B 12 (cobalamin) | |
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Vitamin C (ascorbic acid) | |
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Vitamin H (biotin) | |
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Vitamin P (rutin, permeability vitamin) | |
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7.5. Vitamin-like substances | |
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Chapter 8. GENERAL REGULARITIES OF METABOLISM AND ENERGY IN THE BODY | |
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8.1. Metabolism | |
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8.2. Energy exchange | |
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Chapter 9. BIOLOGICAL OXIDATION | |
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9.1. The essence of biological oxidation | |
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9.2. Respiratory chain | |
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9.3. Oxidative phosphorylation | |
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Chapter 10. CARBOHYDRATE METABOLISM | |
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10.1. Digestion of carbohydrates | |
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10.2. Glucose metabolism | |
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10.3. Glycogen biosynthesis | |
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10.4. Glycogen breakdown | |
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10.5. Anaerobic glycolysis | |
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10.6. Aerobic breakdown of glucose | |
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10.7. Pentose phosphate cycle | |
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10.8. Glucose biosynthesis (gluconeogenesis) | |
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10.10. Regulation of carbohydrate metabolism | |
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Chapter 11. LIPID METABOLISM | |
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11.1. Digestion of lipids | |
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11.2. Metabolism of glycerol | |
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11.3. Fatty acid metabolism |
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11.4. Biosynthesis of fats | |
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11.5. Regulation of lipid metabolism | |
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Chapter 12. METABOLISM OF NUCLEIC ACIDS | |
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12.1. RNA and DNA decay pathways | |
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12.2. Decomposition of purine and pyrimidine bases | |
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12.3. Biosynthesis of nucleotides | |
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12.4. Biosynthesis of nucleic acids | |
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12.5. Path of information from genotype to phenotype | |
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Chapter 13. PROTEIN METABOLISM | |
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13.1. Concept of protein metabolism | |
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13.2. Digestion of food proteins and breakdown of tissue proteins | |
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13.3. Amino acid metabolism | |
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13.4. Removing ammonia from the body. Ornithine cycle | |
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13.5. Amino acid synthesis | |
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13.6. Protein biosynthesis (translation) | |
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Chapter 14. WATER-SALT AND MINERAL METABOLISM | |
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14.1. Water-salt metabolism | |
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The role and functions of water in the process of life | |
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14.2. Regulation of water-salt metabolism | |
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Regulation of osmotic pressure and extracellular fluid volume | |
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pH regulation | |
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14.3. Mineral metabolism | |
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Minerals | |
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Functions of minerals | |
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Minerals and nucleic acid metabolism | |
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Minerals and protein metabolism | |
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Minerals and metabolism of carbohydrates and lipids | |
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14.4. Regulation of mineral metabolism | |
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Chapter 15. RELATIONSHIP OF THE METABOLISM OF PROTEINS, FATS, CARBOHYDRATES AND NUCLEIC ACIDS | |
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Chapter 16. HORMONES. NERVOUS-HORMONAL REGULATION OF METABOLISM | |
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16.1. The concept of hormones. Basic principles of metabolic regulation | |
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16. 2. Classification of hormones | |
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16.3. General understanding of the action of hormones | |
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16. 4. Hormones of the thyroid and parathyroid glands | |
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Thyroid hormones | |
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Parathyroid hormones | |
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16.5. Pancreatic hormones | |
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16.6. Adrenal hormones | |
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16.7. Gonadal hormones | |
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16.8. Hormones of the hypothalamic-pituitary system | |
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16.9. Hormones of the thymus and pineal gland | |
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16.10. Prostaglandins | |
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16.11. Biochemical adaptation | |
Reactions to unfavorable environmental factors are detrimental to living organisms only under certain conditions, but in most cases they have adaptive significance. Therefore, these responses were called “general adaptation syndrome” by Selye. In later works, he used the terms “stress” and “general adaptation syndrome” as synonyms.
Adaptation is a genetically determined process of the formation of protective systems that ensure increased stability and the course of ontogenesis in unfavorable conditions for it.
Adaptation is one of the most important mechanisms that increases the stability of a biological system, including a plant organism, in changed conditions of existence. The better an organism is adapted to a certain factor, the more resistant it is to its fluctuations.
The genotypically determined ability of an organism to change metabolism within certain limits depending on the action of the external environment is called reaction norm. It is controlled by the genotype and is characteristic of all living organisms. Most modifications that occur within the normal range of reaction have adaptive significance. They correspond to changes in the environment and ensure better plant survival under fluctuating environmental conditions. In this regard, such modifications have evolutionary significance. The term “reaction norm” was introduced by V.L. Johannsen (1909).
The greater the ability of a species or variety to be modified in accordance with the environment, the wider its reaction rate and the higher its ability to adapt. This property distinguishes resistant varieties of crops. As a rule, slight and short-term changes in environmental factors do not lead to significant disturbances in the physiological functions of plants. This is due to their ability to maintain relative dynamic balance of the internal environment and the stability of basic physiological functions in a changing external environment. At the same time, sudden and prolonged impacts lead to disruption of many functions of the plant, and often to its death.
Adaptation includes all processes and adaptations (anatomical, morphological, physiological, behavioral, etc.) that contribute to increased stability and contribute to the survival of the species.
1.Anatomical and morphological devices. In some representatives of xerophytes, the length of the root system reaches several tens of meters, which allows the plant to use groundwater and not experience a lack of moisture in conditions of soil and atmospheric drought. In other xerophytes, the presence of a thick cuticle, pubescent leaves, and the transformation of leaves into spines reduce water loss, which is very important in conditions of lack of moisture.
Stinging hairs and spines protect plants from being eaten by animals.
Trees in the tundra or at high mountain altitudes look like squat creeping shrubs; in winter they are covered with snow, which protects them from severe frosts.
In mountainous regions with large daily temperature fluctuations, plants often have the form of spread out pillows with numerous stems densely spaced. This allows you to maintain moisture inside the pillows and a relatively uniform temperature throughout the day.
In marsh and aquatic plants, a special air-bearing parenchyma (aerenchyma) is formed, which is an air reservoir and facilitates the breathing of parts of the plant immersed in water.
2. Physiological-biochemical adaptations. In succulents, an adaptation for growing in desert and semi-desert conditions is the assimilation of CO 2 during photosynthesis via the CAM pathway. These plants have stomata that are closed during the day. Thus, the plant preserves its internal water reserves from evaporation. In deserts, water is the main factor limiting plant growth. The stomata open at night, and at this time CO 2 enters the photosynthetic tissues. The subsequent involvement of CO 2 in the photosynthetic cycle occurs during the day when the stomata are closed.
Physiological and biochemical adaptations include the ability of stomata to open and close, depending on external conditions. The synthesis in cells of abscisic acid, proline, protective proteins, phytoalexins, phytoncides, increased activity of enzymes that counteract the oxidative breakdown of organic substances, accumulation of sugars in cells and a number of other changes in metabolism help to increase plant resistance to unfavorable environmental conditions.
The same biochemical reaction can be carried out by several molecular forms of the same enzyme (isoenzymes), with each isoform exhibiting catalytic activity in a relatively narrow range of some environmental parameter, such as temperature. The presence of a number of isoenzymes allows the plant to carry out reactions in a much wider temperature range compared to each individual isoenzyme. This allows the plant to successfully perform vital functions in changing temperature conditions.
3. Behavioral adaptations, or avoidance of an unfavorable factor. An example is ephemera and ephemeroids (poppy, chickweed, crocuses, tulips, snowdrops). They go through their entire development cycle in the spring in 1.5-2 months, even before the onset of heat and drought. Thus, they seem to leave, or avoid falling under the influence of the stressor. Similarly, early ripening varieties of agricultural crops form a harvest before the onset of unfavorable seasonal phenomena: August fogs, rains, frosts. Therefore, the selection of many agricultural crops is aimed at creating early ripening varieties. Perennial plants overwinter in the form of rhizomes and bulbs in the soil under snow, which protects them from freezing.
Adaptation of plants to unfavorable factors is carried out simultaneously at many levels of regulation - from an individual cell to a phytocenosis. The higher the level of organization (cell, organism, population), the greater the number of mechanisms simultaneously involved in plant adaptation to stress.
Regulation of metabolic and adaptation processes inside the cell is carried out using systems: metabolic (enzymatic); genetic; membrane These systems are closely interconnected. Thus, the properties of membranes depend on gene activity, and the differential activity of the genes themselves is under the control of membranes. Enzyme synthesis and activity are controlled by genetic level, at the same time, enzymes regulate nucleic acid metabolism in the cell.
On organismal level new ones are added to the cellular mechanisms of adaptation, reflecting the interaction of organs. In unfavorable conditions, plants create and retain such an amount of fruit elements that are sufficiently provided with the necessary substances to form full-fledged seeds. For example, in the inflorescences of cultivated cereals and in the crowns of fruit trees, under unfavorable conditions, more than half of the established ovaries may fall off. Such changes are based on competitive relationships between organs for physiologically active substances and nutrients.
Under stress conditions, the processes of aging and falling of the lower leaves sharply accelerate. At the same time, substances needed by plants move from them to young organs, responding to the organism’s survival strategy. Thanks to the recycling of nutrients from the lower leaves, the younger ones, the upper leaves, remain viable.
Mechanisms for regeneration of lost organs operate. For example, the surface of a wound is covered with secondary integumentary tissue (wound periderm), a wound on a trunk or branch is healed with nodules (calluses). When the apical shoot is lost, dormant buds awaken in plants and side shoots intensively develop. The regeneration of leaves in the spring instead of those that fell in the fall is also an example of natural organ regeneration. Regeneration as a biological device that provides vegetative propagation of plants by segments of the root, rhizome, thallus, stem and leaf cuttings, isolated cells, and individual protoplasts has a great practical significance for plant growing, fruit growing, forestry, ornamental gardening, etc.
The hormonal system also participates in the processes of protection and adaptation at the plant level. For example, under the influence of unfavorable conditions in a plant, the content of growth inhibitors sharply increases: ethylene and abscisic acid. They reduce metabolism, inhibit growth processes, accelerate aging, organ loss, and the plant’s transition to a dormant state. Inhibition of functional activity under stress conditions under the influence of growth inhibitors is a characteristic reaction for plants. At the same time, the content of growth stimulants in tissues decreases: cytokinin, auxin and gibberellins.
On population level selection is added, which leads to the emergence of more adapted organisms. The possibility of selection is determined by the existence of intrapopulation variability in plant resistance to various environmental factors. An example of intrapopulation variability in resistance can be the uneven emergence of seedlings on saline soil and the increase in variation in germination timing with increasing stressors.
View in modern concept consists of a large number of biotypes - smaller ecological units that are genetically identical, but exhibit different resistance to environmental factors. Under different conditions, not all biotypes are equally viable, and as a result of competition, only those that best meet the given conditions remain. That is, the resistance of a population (variety) to one or another factor is determined by the resistance of the organisms that make up the population. Resistant varieties include a set of biotypes that provide good productivity even in unfavorable conditions.
At the same time, during long-term cultivation of varieties, the composition and ratio of biotypes in the population changes, which affects the productivity and quality of the variety, often not for the better.
So, adaptation includes all processes and adaptations that increase the resistance of plants to unfavorable environmental conditions (anatomical, morphological, physiological, biochemical, behavioral, population, etc.)
But to choose the most effective adaptation path, the main thing is the time during which the body must adapt to new conditions.
In the event of a sudden action of an extreme factor, the response cannot be delayed; it must follow immediately to avoid irreversible damage to the plant. With prolonged exposure to a small force, adaptive changes occur gradually, and the choice of possible strategies increases.
In this regard, there are three main adaptation strategies: evolutionary, ontogenetic And urgent. The goal of the strategy is the effective use of available resources to achieve the main goal - the survival of the body under stress. The adaptation strategy is aimed at maintaining the structural integrity of vital macromolecules and the functional activity of cellular structures, preserving life regulation systems, and providing plants with energy.
Evolutionary or phylogenetic adaptations(phylogeny - the development of a biological species over time) are adaptations that arise during the evolutionary process on the basis of genetic mutations, selection and are inherited. They are the most reliable for plant survival.
In the process of evolution, each plant species has developed certain needs for living conditions and adaptability to the ecological niche it occupies, a stable adaptation of the organism to its habitat. Moisture and shade tolerance, heat resistance, cold resistance and other ecological characteristics of specific plant species were formed as a result of long-term exposure to appropriate conditions. Thus, heat-loving and short-day plants are characteristic of southern latitudes, while less demanding heat-loving and long-day plants are characteristic of northern latitudes. Numerous evolutionary adaptations of xerophyte plants to drought are well known: economical use of water, deep-lying root system, shedding leaves and transition to a dormant state, and other adaptations.
In this regard, varieties of agricultural plants exhibit resistance precisely to those environmental factors against the background of which breeding and selection of productive forms is carried out. If selection takes place in a number of successive generations against the background of the constant influence of some unfavorable factor, then the resistance of the variety to it can be significantly increased. It is natural that the varieties selected by the research institute Agriculture South-East (Saratov), are more resistant to drought than varieties created in breeding centers of the Moscow region. In the same way, in ecological zones with unfavorable soil-climatic conditions, resistant local plant varieties were formed, and endemic plant species are resistant precisely to the stressor that is expressed in their habitat.
Characteristics of resistance of spring wheat varieties from the collection of the All-Russian Institute of Plant Growing (Semyonov et al., 2005)
| Variety | Origin | Sustainability |
| Enita | Moscow region | Moderately drought resistant |
| Saratovskaya 29 | Saratov region | Drought resistant |
| Comet | Sverdlovsk region. | Drought resistant |
| Karasino | Brazil | Acid resistant |
| Prelude | Brazil | Acid resistant |
| Colonias | Brazil | Acid resistant |
| Trintani | Brazil | Acid resistant |
| PPG-56 | Kazakhstan | Salt resistant |
| Osh | Kyrgyzstan | Salt resistant |
| Surkhak 5688 | Tajikistan | Salt resistant |
| Messel | Norway | Salt tolerant |
In a natural setting, environmental conditions usually change very quickly, and the time during which the stress factor reaches a damaging level is not enough for the formation of evolutionary adaptations. In these cases, plants use not permanent, but stressor-induced defense mechanisms, the formation of which is genetically predetermined (determined).
Ontogenetic (phenotypic) adaptations are not associated with genetic mutations and are not inherited. The formation of this kind of adaptation takes a relatively long time, which is why they are called long-term adaptations. One of these mechanisms is the ability of a number of plants to form a water-saving CAM-type photosynthetic pathway under conditions of water deficiency caused by drought, salinity, low temperatures and other stressors.
This adaptation is associated with the induction of the expression of the phosphoenolpyruvate carboxylase gene, which is “inactive” under normal conditions, and the genes of other enzymes of the CAM pathway of CO 2 assimilation, with the biosynthesis of osmolytes (proline), with the activation of antioxidant systems and changes in the daily rhythms of stomatal movements. All this leads to very economical use of water.
In field crops, for example, corn, aerenchyma is absent under normal growing conditions. But under conditions of flooding and a lack of oxygen in the tissues of the roots, some of the cells of the primary cortex of the root and stem die (apoptosis, or programmed cell death). In their place, cavities are formed through which oxygen is transported from the aboveground part of the plant to the root system. The signal for cell death is ethylene synthesis.
Urgent adaptation occurs with rapid and intense changes in living conditions. It is based on the formation and functioning of shock defense systems. Shock defense systems include, for example, the heat shock protein system, which is formed in response to a rapid increase in temperature. These mechanisms provide short-term conditions for survival under the influence of a damaging factor and thereby create the prerequisites for the formation of more reliable long-term specialized adaptation mechanisms. An example of specialized adaptation mechanisms is the new formation of antifreeze proteins at low temperatures or the synthesis of sugars during the overwintering of winter crops. At the same time, if the damaging effect of a factor exceeds the protective and reparation capabilities of the body, then death inevitably occurs. In this case, the organism dies at the stage of urgent or at the stage of specialized adaptation, depending on the intensity and duration of the extreme factor.
Distinguish specific And nonspecific (general) plant responses to stressors.
Nonspecific reactions do not depend on the nature of the acting factor. They are the same under the influence of high and low temperatures, lack or excess of moisture, high concentration of salts in the soil or harmful gases in the air. In all cases, the permeability of membranes in plant cells increases, respiration is impaired, the hydrolytic breakdown of substances increases, the synthesis of ethylene and abscisic acid increases, and cell division and elongation are inhibited.
The table presents a complex of nonspecific changes that occur in plants under the influence of various environmental factors.
Changes in physiological parameters in plants under the influence of stress conditions (according to G.V. Udovenko, 1995)
| Options | The nature of changes in parameters under conditions | |||
| drought | salinity | high temperature | low temperature | |
| Ion concentration in tissues | Growing | Growing | Growing | Growing |
| Water activity in the cell | Falls | Falls | Falls | Falls |
| Osmotic potential of the cell | Growing | Growing | Growing | Growing |
| Water holding capacity | Growing | Growing | Growing | — |
| Water shortage | Growing | Growing | Growing | — |
| Permeability of protoplasm | Growing | Growing | Growing | — |
| Transpiration rate | Falls | Falls | Growing | Falls |
| Transpiration efficiency | Falls | Falls | Falls | Falls |
| Energy efficiency of breathing | Falls | Falls | Falls | — |
| Breathing intensity | Growing | Growing | Growing | — |
| Photophosphorylation | Decreasing | Decreasing | — | Decreasing |
| Stabilization of nuclear DNA | Growing | Growing | Growing | Growing |
| Functional activity of DNA | Decreasing | Decreasing | Decreasing | Decreasing |
| Proline concentration | Growing | Growing | Growing | — |
| Content of water-soluble proteins | Growing | Growing | Growing | Growing |
| Synthetic reactions | Depressed | Depressed | Depressed | Depressed |
| Absorption of ions by roots | Suppressed | Suppressed | Suppressed | Suppressed |
| Transport of substances | Depressed | Depressed | Depressed | Depressed |
| Pigment concentration | Falls | Falls | Falls | Falls |
| Cell division | Braking | Braking | — | — |
| Cell stretching | Suppressed | Suppressed | — | — |
| Number of fruit elements | Reduced | Reduced | Reduced | Reduced |
| Aging of organs | Accelerated | Accelerated | Accelerated | — |
| Biological harvest | Demoted | Demoted | Demoted | Demoted |
Based on the data in the table, it can be seen that plant resistance to several factors is accompanied by unidirectional physiological changes. This gives reason to believe that an increase in plant resistance to one factor may be accompanied by an increase in resistance to another. This has been confirmed by experiments.
Experiments at the Institute of Plant Physiology of the Russian Academy of Sciences (Vl. V. Kuznetsov and others) have shown that short-term heat treatment of cotton plants is accompanied by an increase in their resistance to subsequent salinity. And the adaptation of plants to salinity leads to an increase in their resistance to high temperatures. Heat shock increases the ability of plants to adapt to subsequent drought and, conversely, during drought the body's resistance to high temperatures increases. Short-term exposure to high temperatures increases resistance to heavy metals and UV-B irradiation. Previous drought promotes plant survival in salinity or cold conditions.
The process of increasing the body's resistance to a given environmental factor as a result of adaptation to a factor of a different nature is called cross adaptation.
To study general (nonspecific) resistance mechanisms big interest represents the response of plants to factors that cause water deficiency in plants: salinity, drought, low and high temperatures and some others. At the level of the whole organism, all plants respond to water deficiency in the same way. Characterized by inhibition of shoot growth, increased growth of the root system, abscisic acid synthesis, and decreased stomatal conductance. After some time, the lower leaves age rapidly and their death is observed. All these reactions are aimed at reducing water consumption by reducing the evaporating surface, as well as by increasing the absorption activity of the root.
Specific reactions- These are reactions to the action of any one stress factor. Thus, phytoalexins (substances with antibiotic properties) are synthesized in plants in response to contact with pathogens.
The specificity or non-specificity of response reactions implies, on the one hand, the attitude of the plant to various stressors and, on the other hand, the specificity of plant reactions various types and varieties to the same stressor.
The manifestation of specific and nonspecific plant responses depends on the strength of stress and the speed of its development. Specific responses occur more often if stress develops slowly, and the body has time to rebuild and adapt to it. Nonspecific reactions usually occur with a shorter and stronger stressor. The functioning of nonspecific (general) resistance mechanisms allows the plant to avoid large energy expenditures for the formation of specialized (specific) adaptation mechanisms in response to any deviation from the norm in their living conditions.
Plant resistance to stress depends on the phase of ontogenesis. The most stable plants and plant organs are in a dormant state: in the form of seeds, bulbs; woody perennials - in a state of deep dormancy after leaf fall. Plants are most sensitive at a young age, since under stress conditions growth processes are damaged first. The second critical period is the period of gamete formation and fertilization. Stress during this period leads to a decrease in the reproductive function of plants and a decrease in yield.
If stressful conditions are repeated and have low intensity, then they contribute to plant hardening. This is the basis for methods of increasing resistance to low temperatures, heat, salinity, and increased levels of harmful gases in the air.
Reliability of a plant organism is determined by its ability to prevent or eliminate failures in different levels biological organization: molecular, subcellular, cellular, tissue, organ, organismal and population.
To prevent disruptions in plant life under the influence unfavorable factors principles are used redundancy, heterogeneity of functionally equivalent components, systems for repairing lost structures.
Redundancy of structures and functionality is one of the main ways to ensure system reliability. Redundancy and redundancy have diverse manifestations. At the subcellular level, the redundancy and duplication of genetic material contribute to increasing the reliability of the plant organism. This is ensured, for example, by the double helix of DNA and an increase in ploidy. The reliability of the functioning of a plant organism under changing conditions is also supported by the presence of various messenger RNA molecules and the formation of heterogeneous polypeptides. These include isoenzymes that catalyze the same reaction, but differ in their physicochemical properties and the stability of the molecular structure under changing environmental conditions.
At the cellular level, an example of redundancy is an excess of cellular organelles. Thus, it has been established that a portion of the available chloroplasts is sufficient to provide the plant with photosynthetic products. The remaining chloroplasts seem to remain in reserve. The same applies to the total chlorophyll content. Redundancy is also manifested in the large accumulation of precursors for the biosynthesis of many compounds.
At the organismal level, the principle of redundancy is expressed in the formation and in the laying down at different times of more than is required for the change of generations, the number of shoots, flowers, spikelets, in a huge amount of pollen, ovules, and seeds.
At the population level, the principle of redundancy manifests itself in large number individuals differing in their resistance to one or another stress factor.
Reparation systems also operate at different levels - molecular, cellular, organismal, population and biocenotic. Repair processes require energy and plastic substances, so repair is possible only if sufficient metabolic rate is maintained. If metabolism stops, repair also stops. IN extreme conditions In the external environment, the preservation of respiration is especially important, since it is respiration that provides energy for reparation processes.
The restorative ability of cells of adapted organisms is determined by the resistance of their proteins to denaturation, namely the stability of the bonds that determine the secondary, tertiary and quaternary structure of the protein. For example, the resistance of mature seeds to high temperatures is usually due to the fact that, after dehydration, their proteins become resistant to denaturation.
The main source of energy material as a substrate for respiration is photosynthesis, therefore, the energy supply of the cell and the associated repair processes depend on the stability and ability of the photosynthetic apparatus to recover after damage. To maintain photosynthesis under extreme conditions in plants, the synthesis of thylakoid membrane components is activated, lipid oxidation is inhibited, and the ultrastructure of plastids is restored.
At the organismal level, an example of regeneration can be the development of replacement shoots, the awakening of dormant buds when growth points are damaged.
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