Included in multicellular organisms, and intracellular parts under the influence of various factors (irritants) are called taxis (from the Greek word taxis - order, arrangement).
These movements can be either towards the stimulus - positive taxis, or away from it - negative. Those irritants that attract to themselves are called attractants (from the Latin word attraxo - I attract), and the irritants from which they move away are called repellents (from the Latin word repello - I repel, drive away). There are also movements that are not oriented in relation to the source of irritation.
If the stimulus is light, then the movement is called phototaxis, if the chemical substance is chemotaxis, the temperature is thermotaxis, the damage is traumataxis, the electric current is galvanotaxis, the force of gravity is geotaxis, etc.
The same irritant can be an attractant for some species, and a repellent for others. So, a unicellular euglena always moves towards a light source, and a trumpeter infusoria always moves away from it.
Taxis may depend on the intensity of the stimulus. For example, phototaxis can be positive at low light intensity, negative at high light intensity, and not appear at all at moderate light intensity. Negative galvanotaxis (when the movement goes towards the cathode) in the ciliates of the shoe with increasing current strength is replaced by a positive one. And it is quite difficult to determine what thermotaxis this ciliate has. If the shoe is placed in a horizontal tube along which there is a temperature difference from +40°C at one end to +15°C at the other, then after a while all the ciliates will accumulate in the place of the tube where the temperature is +26°, +27° WITH. Here for them, apparently, the most favorable conditions: neither hot nor cold.
Thanks to taxis, single-celled organisms find food, find places with more favorable living conditions, and also find individuals of their own species and avoid harmful influences.
Of the intracellular taxises, the phototaxis of chloroplasts in the leaf of a plant is best studied. They contain chlorophyll, thanks to which it goes into the light. Usually in leaves in the dark, chloroplasts are more or less evenly distributed along all walls. In moderate light, they move towards walls perpendicular to the incident light. This achieves maximum illumination of chloroplasts. With a significant increase in the brightness of light, chloroplasts move to walls that are parallel to the light beam, and their illuminated surface is reduced to a minimum. The biological significance of chloroplast phototaxis is obvious.
Movement towards the stimulus.
Source: "Dictionary of Botanical Terms"
I.A. Dudki, Kyiv, Naukova Dumka, 1984
Nikolai Avgustovich Monteverde (1856-1929) - botanist, graduated from the course at St. Petersburg University, specialist in plant physiology, was the chief botanist of the Imperial St. Petersburg Botanical Garden. N. A. Monteverde's book became an atlas of Russian flora. It included plants typical both for the European part of the Russian Empire and for its outskirts, for example, the Caucasus, Siberia or Turkmenistan. The book is also supplemented with a convenient reference and bibliographic section. Reproduced in the original author's spelling of the 1916 edition (publishing house "Petrograd. Edition by A. F. Devrien").
In the "Botanical Atlas" the reader will find a description of about 800 species of agricultural and wild plants, including the main agricultural crops, tree species, medicinal, ether-bearing, weeds and other plants that have one or another national economic significance and are also widespread in the territory. USSR.tables The atlas is illustrated with 149 multicolor tables and 57 figures. Color images of plants convey not only the shape and relative size, but also their natural color. The material in the atlas is arranged in a systematic manner, in accordance with modern ideas about the evolution of the organic world. schools and many people who come into contact with plants and are interested in them in their activities, the "Botanical Atlas" will be an interesting and useful illustrated guide in the knowledge of plants in our country. Reproduced in the original author's spelling of the 1963 edition (Selkhozizdat publishing house).
"Botanical Atlas" N.P. Zhivotovsky (1846–1888) is one of the famous books on the natural sciences in pre-revolutionary Russia. For almost twenty years, its author gave the Pedagogical Museum of St. Petersburg, published a variety of works on botany and natural sciences. Zhivotovsky studied at the natural department of the Faculty of Physics and Mathematics of St. Petersburg University, from which he graduated in 1868 and soon joined the main department of military educational institutions. In 1871, a permanent commission of the Pedagogical Museum was established.
Botanical atlas. Carl von Hoffmann. The flora of the Earth is so diverse that its full description would require an entire library. Illustrations for postcards are selected from the atlas, authored by the German botanist Carl von Hoffmann.
One of the main properties of a living organism is movement or response to an irritating factor. In developed organisms, movement is a muscular act, the implementation of which is achieved due to the influence of a nerve impulse on a muscle. However, in elementary organisms, movement and response to stimulation take on a somewhat different form. In general, these phenomena are united in the concept of "taxis". This is a motor reaction of the body, its part or a separate organelle in the direction of the stimulus or away from it. In plants, the term "tropism" has a similar interpretation. Taxis and tropisms can be positive or negative.
Sources of irritation
Sources of irritation capable of provoking taxis are factors of animate and inanimate nature. Any physical phenomena, biological factors or chemical substances are capable of causing the movement of an organism if its vital activity depends on them. For example, chemotaxis is a directed movement towards the location of a chemical. If the cell moves towards the molecule that has value as a metabolic substrate, then such chemotaxis is positive. Negative chemotaxis is the deliberate increase in the distance between a chemical and a cell. An example of positive chemotaxis is the movement of a leukocyte to the site of inflammation.
Negative chemical taxis is an active flight of cells or an attempt to delimit from them if substances are capable of leading to their death. Also, the source of irritation is electromagnetic radiation with different wavelengths, liquid, soil and other factors. In each case, taxis can be positive, that is, the organism, its part or its separate organoid, approaches the stimulus, or negative. Negative taxis is a deliberate increase in the distance between the organism and the irritating factor.
Tropism and taxis
Tropism is a particular example of taxis in plants. They have many landmarks in relation to which they move during life or daily cycles. For example, the tops of almost all photosynthetic plants have negative geotropism and positive heliotropism. This means that they seek to reach the sun in order to increase the efficiency of photosynthesis. Plants also have positive hydrotropism, negative thermotropism.
Specific tropisms and taxises
Having understood what taxis is in biology, the definition of specific stimuli for some organisms allows us to understand the features of their metabolism. In particular, organisms whose metabolism must proceed at high temperatures have positive thermotropism. There is also magnetotaxis, anemotaxis (movement in the direction of air), barotaxis, cytotaxis, rheotaxis (depending on the flow in water bodies), galvanotaxis (in relation to electric current). At the same time, taxis is a fundamental type of behavior of unicellular or multicellular organisms. Only in relation to the reference point, which is any of the above factors, organisms are able to move in wildlife.
instinctive form of spatial orientation of animals, mechanical orienting components of behavioral acts, innate ways of spatial orientation:
1) in the direction of vitally favorable conditions and irritations of the external environment (positive taxis);
2) away from unfavorable (negative taxises). For example, moving towards everything that looks like food and away from everything that is unpleasant. In plants, similar reactions are expressed in changes in the direction of growth and are called tropisms.
According to the modality of influences and reactions in relation to the diverse components, they differ:
1) phototaxis - reactions to light;
2) chemotaxis - to chemical stimuli;
3) thermotaxis - for temperature changes;
4) geotaxis - by gravity;
5) hydrotaxis - on the flow of liquids.
The taxis of unicellular and many lower multicellular animals are represented by orthotaxis - reactions to the acceleration or deceleration of movement, and clinotaxis - reactions to a change in the direction of movement at a certain angle.
Taxis are usually characteristic of unicellular organisms devoid of a nervous system, but are also observed in some more highly organized species. Their manifestation is maximal in protozoa, moderate in worms and insects, and disappears already in primitive mammals.
In animals with a developed central nervous system and symmetrically located sensory organs, in addition, an active choice of the direction of movement and the preservation of this direction are possible - topotaxis. They are permanent components of even the most complex forms of behavior.
TAXIS
from the Greek taxis - order, location) - congenital mechanisms of spatial orientation of the motor activity of animals in the direction of favorable vital environmental conditions (positive T.) or in the direction from unfavorable (dangerous) conditions for life (negative T.). In plants, similar reactions are expressed in a change in the direction of growth (tropism). The nature of orientation depends on the impact of biologically significant agents of the environment, in connection with which T. are divided into photo-chemo-, thermo-, geo-, anemo-, hydrotaxis, etc. (reactions to light, chemical stimuli, temperature changes, force gravity, air flow, liquid flow, environmental humidity, etc.). The degree of complexity and function of t. depend on the level of evolutionary development of animals. Lower T. - orthotaxis (acceleration or deceleration of movement) are characteristic of unicellular and many lower multicellular animals.
In animals with developed n. With. and symmetrically located sense organs, it is possible to actively choose the direction of movement and maintain this direction (topotaxis). Such behaviors are permanent components of even complex forms of behavior. Wed Kinesis.
taxis
Word formation. Comes from the Greek. taxis - order, arrangement.
Specificity. In accordance with them, movement begins either towards favorable, vital elements of the environment (positive taxises), or from unfavorable ones (negative taxises).
Phototaxis, as reactions to light,
Chemotaxis to chemical stimuli,
Thermotaxis for temperature changes,
Geotaxis on gravity,
Hydrotaxis on the flow of liquids.
Unicellular and many lower multicellular animals are characterized by:
Orthotaxis, as a reaction to the acceleration or deceleration of movement,
Clinotaxis, as a reaction to a change in the direction of movement at a certain angle.
