The effect of temperature on plants is an example of action. The effect of high temperatures on plants. Thermal regime for indoor plants
For most plants, the most favorable temperatures for life are +15...+30 o C. At temperatures +35...+40 o C, most plants are damaged.
Action high temperatures entails a number of dangers for plants: severe dehydration and desiccation, burns, destruction of chlorophyll, irreversible respiratory disorders and other physiological processes, cessation of protein synthesis and increased breakdown, accumulation of toxic substances, in particular ammonia. At very high temperatures, the permeability of membranes sharply increases, and then thermal denaturation of proteins, coagulation of the cytoplasm and cell death occurs. Overheating of the soil leads to damage and death of superficially located roots, and to burns of the root collar.
Primary changes in cellular structures occur at the membrane level as a result of activation of the formation of oxygen radicals and subsequent lipid peroxidation, disruption of the antioxidant system - the activity of superoxide dismutase, glutathione reductase and other enzymes. This causes the destruction of protein-lipid complexes of the plasmalemma and other cell membranes, leading to the loss of osmotic properties of the cell. As a result, disorganization of many cell functions and a decrease in the speed of various physiological processes are observed. Thus, at a temperature of 20 o C, all cells undergo the process of mitotic division, at 38 o C, mitosis is observed in every seventh cell, and an increase in temperature to 42 o C reduces the number of dividing cells by 500 times.
At maximum temperatures, the consumption of organic substances for respiration exceeds its synthesis, the plant becomes poor in carbohydrates, and then begins to starve. This is especially pronounced in plants temperate climate(wheat, potatoes, many garden crops). With general weakening, their susceptibility to fungal and viral infections increases.
Even a short-term stressful effect of high temperature causes a restructuring of the hormonal system of plants. Using the example of wheat and pea seedlings, it was established that heat shock induces a cascade of multi-stage changes in the hormonal system, which is triggered by the release of IAA from the pool of its conjugates, which acts as a stress signal and initiates ethylene synthesis. The result of ethylene synthesis is a subsequent decrease in the level of IAA and an increase in ABA. These hormonal changes apparently induce the synthesis of antioxidant enzymes and heat shock proteins, cause a decrease in growth rates and, as a result, the plant’s resistance to high temperatures increases.
There is a certain connection between plant habitat conditions and heat resistance. The drier the habitat, the higher the temperature maximum, the greater the heat resistance of plants.
Plants can prepare for exposure to high temperatures in a few hours. Thus, on hot days, plants’ resistance to high temperatures in the afternoon is higher than in the morning. Usually this resistance is temporary, it is not fixed and disappears quite quickly if it gets cool. The reversibility of thermal effects can range from several hours to 20 days.
Heat resistance is also related to the stage of plant development: young, actively growing tissues are less resistant than old ones. High temperatures during the flowering period are especially dangerous. Almost all generative cells under these conditions undergo structural changes, lose activity and the ability to divide, deformation of pollen grains, poor development of the embryo sac and the appearance of sterile flowers are observed.
Plant organs also differ in heat resistance. Dehydrated organs tolerate elevated temperatures better: seeds up to 120 o C, pollen up to 70 o C, spores can withstand heating up to 180 o C for several minutes.
Of the tissues, cambial ones are the most resistant. Thus, the cambial layer in trunks tolerates temperatures up to +51 o C in summer.
When caring for indoor plants, it is important to follow the appropriate temperature regime. After all, in wildlife each of them grows in a certain climatic zone and is adapted to these living conditions.
At home, it is almost impossible to create a tropical, subtropical or semi-desert climate for them, but you must try to maintain a similar temperature regime, otherwise the plant may lose its decorative effect and even die.
In this article we will look at the effect of temperature on plant growth and development.
Effect of temperature on plants
If a plant is provided with the temperature to which it is adapted, it grows well, develops and blooms profusely. But flower growers often have difficulty ensuring the required temperature conditions.
Despite the fact that many indoor flowers come from the tropics, they do not tolerate rising temperatures well.. In their native climate, the summer heat is accompanied by high humidity, unlike the climate middle zone. Therefore, often when the temperature rises, first the tip dries out, and then the entire leaf.
Just like an increase in temperature, a decrease in temperature is harmful for many plants.
Low indoor temperatures, accompanied by increased humidity, are typical for autumn and spring periods before turning on and after turning off the heating. At this time, cases of rotting of the root system of plants become more frequent, and if the temperature drops significantly, their leaves may curl and fall off. Plants also react to a sharp drop in temperature.
High temperature for plants
Not all indoor plants tolerate summer heat well. Many of them suffer from high temperatures and low humidity in temperate areas. To protect indoor flowers from unusual temperatures, use abundant watering, spraying and shading.
Tropical summers are characterized by high humidity. At the same time, plants can easily tolerate temperatures up to 30ºС. Increasing the humidity in the room is facilitated by good moistening of the earthen clod and spraying of the leaves of the plant.
For residents of the tropics, in addition to frequent watering, placing the pot in a tray with moistened sand is suitable.. Spraying can be done daily with water at room temperature.
Often a plant suffers in summer not so much from high temperature as from the action of direct sun rays. In order to avoid burns on the leaves, and at the same time reduce the air temperature in which the plant lives, you need to put it in the shade or cover it from the sun with white paper.
The effect of low temperatures on plants
Winter content indoor plants always different from summer.
In winter, most plants need it, because in their homeland the temperature regime changes. Typically, indoor flowers should not grow in winter, and for this purpose they are kept at low temperatures oh and low watering.
There are species that are insensitive to temperature changes and do not have a pronounced dormant period. The rest must overwinter at temperatures to which they are adapted.
Plants tolerant to temperature changes
Some unpretentious species almost do not react at all to a decrease or increase in temperature. They are very resistant to temperature influences and do not require maintaining any specific temperature in winter.
These are the following decorative foliage plants: , . They can be kept in winter at room temperature, but they can withstand its reduction to plus 5-10ºС.
Many coniferous species growing in , withstands even short-term frosts. Pelargonium is also very hardy, shedding its leaves only when the temperature drops below 0ºC.
Let's look at groups of plants in relation to temperature.
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Heat-loving indoor plants
There are many species that do not tolerate low temperatures. If the air temperature drops to 10-13ºС, their leaves curl and fall off.
To such heat-loving tender plants include: , , fittonia. Optimal temperature their wintering area is 15-20ºС.
Plants that require cool temperatures
A cool winter is needed mainly for flowering plants, which after a period of dormancy begin to grow intensively and bloom. This , .
Among those that overwinter in the cool weather there are also decorative foliage plants. These are some types of ficus, ferns, and Kalanchoe. It is recommended to keep all these plants in winter at a temperature of 8-15ºС.
Plants requiring cold storage
Among indoor flowers There are also those grown at low room temperatures. These are mainly succulents that should not grow during the winter. The growth of succulents with shortened daylight hours leads to elongation. They weaken, they lose decorative look, do not bloom.
Almost all types of cacti require wintering at a temperature of 5-8ºС with very rare watering once a month or less. Some species, Aeoniums, overwinter at the same temperature.
Agave can also be kept at lower temperatures - down to 0ºС.
Many bulbous crops and gloxinia tubers are also kept in winter at temperatures around 8ºС, which stimulates their growth and flowering in the spring.
We looked at the classification of plants in relation to temperature.
Protecting flowers during ventilation
Ventilation is necessary for indoor plants, as they need fresh air. They especially experience this disadvantage in winter, when the windows are closed due to the winter cold. However, winter ventilation must be carried out very carefully so as not to sharply reduce the temperature in the room and harm the plants.
You can gradually ventilate the room through an intermediate room, the air of which has already been renewed.
In this case Fresh air will gradually move into the room with plants and will not lead to a strong decrease in temperature.
The easiest way to ventilate the room is to take the flowers to another room..
You especially need to take care of those plants that are closer to the window, because there the temperature can reach their limit values. It is recommended to bring them back only after the temperature returns to normal.
In addition to reducing the temperature when ventilating, there is also a risk of drafts. Many species react negatively to drafts by dropping leaves, and this can happen even in summer. Therefore, it is necessary to ensure that indoor flowers are not in a draft and remove them when opening the windows.
Plant adaptation to high temperatures
The ability of plants to adapt and tolerate high temperatures is called heat tolerance. Heat-loving flowers can withstand long-term overheating, while moderately heat-loving flowers can withstand short-term overheating.
To protect against high temperatures, plants use different kinds adaptation.
Morphological and anatomical devices are a special structure that helps prevent overheating. These features include:
- Shiny surface of leaves and stems, reflecting sunlight;
- Dense pubescence of the plant, which enhances the ability of leaves to reflect and gives them a light color;
- Meridional or vertical position of leaves, which reduces the surface area that absorbs sunlight;
- General reduction of leaf surface.
All these features also help the plant lose less water.
Physiological adaptations include:
Plant resistance to low temperatures
There are no special properties of plants adapting to low temperatures. However, there are devices that protect against a complex of unfavorable conditions - wind, cold, and the possibility of drying out. Among them are:
- Pubescence of the kidney scales;
- Thickening of the cork layer;
- Pubescence of leaves;
- Thickened cuticle;
- Resining buds for the winter in coniferous plants;
- Special forms of growth and small sizes, for example, small leaves, dwarfism, close internodes, horizontal growth form;
- Development of thick and fleshy contractile roots. At the end of autumn, they dry out and decrease in length, drawing bulbs, roots, and overwintering buds into the ground.
Physiological adaptations help lower the freezing point of cell sap and protect water from freezing.
- These include:
- Increased concentration of cell sap; Anabiosis is a possibility when extreme conditions
suspend life processes in the plant and reduce productivity.
For which plants are temperature fluctuations dangerous? Natural temperature fluctuations occur both throughout the year and throughout the day. How various plants
can they tolerate such changes? Most indoor flowers do not tolerate strong temperature fluctuations.
. So, when the temperature drops by 6-10 degrees, the leaves of Dieffenbachia begin to turn yellow and wither, and growth stops. The same “symptoms” can be observed in other plants. Therefore, when ventilating a room in winter, it is better to remove flowers from the windowsill.
It is important to know that a gradual change in temperature, at a rate of no more than 0.5 degrees per hour, can be tolerated by most plants.
However, there are plants that can tolerate even large temperature fluctuations. These include aloe, sansevieria, clivia, aspidistra, and others.
The most thermophilic, and therefore poorly tolerant of strong temperature changes, are the flowering and decorative foliage representatives of the families of aroids, begonias, mulberries and bromeliads.
The most thermophilic are variegated guests from the tropics: caladium, codiaeum.
Natural fluctuations in home temperature
In nature, there is a rhythmic change in temperature: at night it decreases, and during the day it rises. The same changes occur throughout the year, when the seasons smoothly change one after another.. Plants in their natural environment adapt to such changes Indoor flowers , which in natural conditions
grow in temperate latitudes and tolerate changes in the amount of heat well, while for guests from the tropics such temperature fluctuations are more painful. Therefore, during the cold season, tropical plants enter a pronounced dormant period. It is very important for them because it has a positive effect on further growth
and development.
It is important to know that indoor plants will benefit when the temperature during the day is several degrees higher than at night. The limit of cold that plants can withstand in natural conditions is given by the values of extremely low temperatures at. Where the lowest temperature is recorded (-90°C, Vostok station in Antarctica), there is no vegetation; and in the areas where plants live, a temperature of -68°C was noted (Oymyakon in Yakutia, the region of taiga larch forests - Larix dahurica).
The vegetation cover of vast areas of the globe (temperate and arctic regions, highlands) is annually exposed to low temperatures for several months. In addition, in some areas and during warmer seasons, plants may experience short-term effects of low temperatures (night and morning frosts). Finally, there are habitats where the entire life of plants takes place at a very low temperature background (Arctic snow and seaweed, snow-nival vegetation in the highlands). It is not surprising that natural selection has developed in plants a number of protective adaptations to the adverse effects of cold.
In addition to the direct effect of low temperature on plants, other unfavorable phenomena occur under the influence of cold. For example, compaction and cracking of frozen soil leads to rupture and mechanical damage to roots; the formation of an ice crust on the soil surface impairs aeration and respiration of roots. Under a thick and long-standing snow cover at a temperature of about 0°C, winter “damping off”, depletion and death of plants is observed due to the consumption of reserve substances for respiration, fungal diseases (“snow mold”), etc., and in the case of excessive In moistened soil, winter “soaking” is also dangerous for plants. In the tundra and northern taiga, the phenomenon of frosty “bulging” of plants is common, which is caused by uneven freezing and expansion of soil moisture. In this case, forces arise that push the plant out of the soil, resulting in “bulging” of entire turf, exposure and breaking of roots, etc., even to the fall of small trees. Therefore, in addition to cold resistance itself (or frost resistance) - the ability to tolerate direct action low temperatures, they also distinguish between winter hardiness of plants - the ability to withstand all the above-mentioned unfavorable winter conditions.
Particular attention should be paid to how low soil temperatures affect plants. Cold soils in combination with a moderately warm air regime for plants (and sometimes with significant heating of the above-ground parts of plants) are not uncommon. These are the living conditions of plants in swamps and marshy meadows with heavy soils, in some tundra etc. high mountain habitats and in vast areas permafrost (about 20% of all land), where during the growing season only a shallow, so-called “active” layer of soil thaws. Under conditions of low soil temperatures after snowmelt (0-10°C), a significant part of the growing season of early spring forest plants - “snowdrops” - takes place. Finally, short-term periods of sharp discrepancy between cold soils and warm air experience in early spring many temperate climate plants (including tree species).
Back in the last century, the German physiologist J. Sachs showed that when the soil is cooled to near-zero temperatures (covering the pot with ice), even abundantly watered plants can wilt, since at low temperatures the roots are not able to intensively absorb water. On this basis, the opinion about the “physiological dryness” of habitats with cold soils (i.e., the inaccessibility of moisture to plants despite its physical abundance) has spread in ecology. At the same time, they lost sight of the fact that Sachs and other physiologists carried out their experiments with fairly heat-loving plants (cucumbers, pumpkin, lettuce, etc.) and that in natural cold habitats plants for which low soil temperatures serve as a natural background may react to them completely different. Really, modern research showed that most plants of the tundra, swamps, and early spring forest ephemeroids do not have those phenomena of inhibition (difficulty in water absorption, disorders water regime etc.), which could be caused by the “physiological dryness” of cold soils. The same is shown for many plants in permafrost areas. At the same time, one cannot completely deny the depressing effect of low temperatures on moisture absorption and other aspects of the life of roots (respiration, growth, etc.), as well as on the activity of soil microflora. It is undoubtedly important in the complex of difficult conditions for plant life in cold habitats. “Physiological dryness”, “physiological drought” due to low soil temperatures are possible in the life of plants in the most difficult conditions, for example, when growing heat-loving plants on cold soils or in early spring for tree species, when the still unleafed branches become very hot (up to 30-35°C) and increase moisture loss, and intensive work of the root systems has not yet begun.
Plants do not have any special morphological adaptations that protect against cold; rather, we can talk about protection from the whole complex of unfavorable conditions in cold habitats, including strong winds, the possibility of drying out, etc. In plants of cold regions (or in plants that tolerate cold winters) ) often there are such protective morphological features as pubescence of bud scales, winter tarring of buds (in conifers), thickened cork layer, thick cuticle, pubescence of leaves, etc. However, their protective effect would make sense only for preserving the own heat of homeothermic organisms, for plants, these features, although they contribute to thermoregulation (reducing radiation emission), are mainly important as protection against desiccation. In the plant world there are interesting examples adaptations aimed at maintaining (albeit short-term) heat in certain parts of the plant. In the highlands of East Africa and South America, giant “rosette” trees from the genera Senecio, Lobelia, Espeletia and others from frequent night frosts there is such protection: at night the leaves of the rosette close, protecting the most vulnerable parts - the growing tops. In some species the leaves are pubescent on the outside, in others the water released by the plant accumulates in the rosette; It only freezes at night surface layer, and the growth cones are protected from frost in a kind of “bath”.
Among the morphological adaptations of plants to life in cold habitats, small size and special growth forms are important. Not only many herbaceous perennials, but also shrubs and shrubs of polar and high-mountain regions have a height of no more than a few centimeters, very close internodes, and very small leaves (the phenomenon of dwarfism or dwarfism). In addition to the well-known example - the dwarf birch (Betula dad), can be called dwarf willows (Sahx polaris, S. arctica, S. herbacea) and many others. Usually the height of these plants corresponds to the depth of the snow cover under which the plants overwinter, since all parts protruding above the snow die from freezing and drying out. Obviously, in the formation of dwarf forms in cold habitats, both the poverty of soil nutrition as a result of suppression of microbial activity and the inhibition of photosynthesis by low temperatures play a significant role. But regardless of the method of education dwarf forms give plants a certain advantage in adapting to low temperatures: they are located in a near-soil ecological microniche, which is warmest in the summer, and in winter they are well protected by snow cover and receive an additional (albeit small) influx of heat from deep in the soil.
Another adaptive feature of the growth form is the transition of relatively large plants (shrubs and even trees) from orthotropic (vertical) to plagiotropic (horizontal) growth and the formation of creeping plants. form- stlantsev, dwarf trees, dwarf trees. Such forms are capable of forming dwarf cedar (Pinus pumila), juniper (Juniperus sibirica, J. communis, J. turkestanica), rowan, etc. The branches of the stlants are spread out on the ground and rise no higher than the usual depth of the snow cover. Sometimes this is the result of the death of the trunk and the growth of lower branches (for example, in spruce), sometimes it is the growth of a tree as if “lying on its side” with a plagiotropic trunk rooted in many places and rising branches (dwarf cedar). Interesting feature some arboreal and shrub elfin trees - constant death of the old part of the trunk and growth of the “top”, as a result of which it is difficult to determine the age of the individual.
Elf trees are common in high mountain and polar regions, in conditions that tree species can no longer withstand (for example, at the upper border of the forest). In extreme conditions, peculiar “elfin wood” forms are found in shrubs and even in species of lichens that usually have erect, bushy growth: on the rocks of Antarctica they form creeping thalli,
Depending on the conditions, modifications in the growth of the same species are possible. But there are species that have completely switched to the dwarf dwarf form, for example, the mountain pine dwarf tree that grows in the Alps and Carpathians - Pinus mughus, allocated as independent type from mountain pine - Pinus montana.
Among the growth forms that contribute to the survival of plants in cold habitats is another extremely unique one - cushion-shaped. The cushion plant shape is formed as a result of increased branching and extremely slow growth of skeletal axes and shoots. Small xerophilous leaves and flowers are located along the periphery of the cushion. Fine earth, dust, and small stones accumulate between individual branches. As a result, some types of cushion plants become more compact and extremely dense: you can walk on such plants as if you were walking on solid soil. These are Silene acaulis. Gypsophila aretioides, Androsace helvetica, Acantholimon diapensioides. From a distance they are difficult to distinguish from boulders. Less dense prickly pillows from genera Eurotia, Saxifraga.
Cushion plants come in different sizes (up to 1 m in diameter) and various shapes: hemispherical, flat, concave, sometimes quite fancy shapes(In Australia and New Zealand they are called "plant sheep").
Thanks to their compact structure, cushion plants successfully withstand cold winds. Their surface heats up almost as much as the surface of the soil, and temperature fluctuations inside are less pronounced than in the environment. There have been cases of significant increases in temperature inside the pillow; for example, in the most common species of the highlands of the Central Tien Shan Dryadanthe tetrandra at an air temperature of 10°C inside the pillow, the temperature reached 23°C due to the accumulation of heat in this kind of “greenhouse”. Due to their slow growth, cushion plants have a longevity comparable to trees. So, in the Pamirs a pillow Acantholimon hedini with a diameter of 3 cm had an age of 10-12 years, with 10 cm - 30-35 years, and the age of large pillows reached hundreds of years.
Within the general form of cushion plants, there is ecological diversity: for example, in the mountains surrounding the Mediterranean Sea, xerophilous “thorny cushions”, which are less compact in structure, are common, which are not found high in the mountains, since they are not very resistant to cold, but are very resistant to drought. The loose structure of the cushion here turns out to be more beneficial for the plant than the compact one, since in conditions of summer drought and strong insolation it reduces the risk of overheating of its surface. The surface temperature of Mediterranean pillows is usually lower than the air temperature due to strong transpiration, and a special microclimate is created inside the pillow; for example, air humidity is kept at 70-80% when the outside air humidity is 30%. Thus, here the shape of the pillow is an adaptation to a completely different set of factors, hence its different “design”.
Among other growth features that help plants overcome the effects of cold, we should also mention various devices aimed at deepening the wintering parts of plants into the soil. This is the development of contractile (contractile) roots - thick and fleshy, with highly developed mechanical tissue. In autumn, they dry out and greatly shorten in length (which is clearly visible from the transverse wrinkling), and forces arise that draw overwintering renewal buds, bulbs, roots, and rhizomes into the soil.
Contractile roots are found in many plants of high mountains, tundra and other cold habitats. They allow, in particular, to successfully resist the frosty bulging of plants from the soil. In the latter case, they not only retract the renewal bud, but also orient it perpendicular to the surface if the plant is knocked down. The depth of retraction by contractile roots varies from a centimeter to several tens of centimeters, depending on the characteristics of the plant and the mechanical composition of the soil.
Adaptive change in shape as protection from cold is a phenomenon limited mainly to cold regions. Meanwhile, plants in more temperate regions also experience the effects of cold. Physiological methods of protection are much more universal. They are aimed primarily at reducing the freezing point of cell sap, protecting water from freezing, etc. Hence such features of cold-resistant plants as increasing the concentration of cell sap, mainly due to soluble carbohydrates. It is known that with the autumn increase in cold resistance (“hardening”), starch is converted into soluble sugars. Another feature of cold-resistant plants is an increase in the proportion of colloid-bound water in the total water supply.
With a slow decrease in temperature, plants can tolerate cooling below the freezing point of cell sap in a state of supercooling (without ice formation). Experiments show that the level of hypothermia and freezing points is closely related to the temperature conditions of the habitat. However, in plants, the state of hypothermia is possible only in slight cold (several degrees below zero). This adaptation path turns out to be much more effective in other poikilothermic insect organisms, in which glycerol, trehalose and other protective substances play the role of antifreeze (openly hibernating insects can tolerate hypothermia of cell juices without freezing down to -30°C).
Many plants are able to remain viable even in a frozen state. There are species that freeze in the fall during the flowering phase and continue to bloom after thawing in the spring (woodlouse - Stellaria media daisy- Bellis perennis, arctic horseradish - Cochlearia fenestrata and etc.). During the short growing season, early spring forest ephemeroids (“snowdrops”) repeatedly endure spring night frosts: flowers and leaves freeze to a glassy-brittle state and become covered with frost, but already 2-3 hours after sunrise they thaw and return to their normal state. The ability of mosses and lichens to withstand prolonged freezing in winter in a state of suspended animation is well known. In one of the experiments, lichen Cladonia frozen at -15°C for 110 weeks (more than two years!).
After thawing, the lichen turned out to be alive and quite viable, photosynthesis and growth resumed. Obviously, in lichens in extremely cold conditions of existence, periods of such anabiosis are very long, and growth and active life activity are carried out only in short favorable periods (and not every year). Such frequent interruption active life for long periods of time, apparently, explains the colossal age of many lichens, determined by the radiocarbon method (up to 1300 years in Rhizocacron geographicum and the Alps, up to 4500 years in lichens in Western Greenland).
Anabiosis is an “extreme measure” in a plant’s fight against cold, leading to the suspension of life processes and a sharp decrease in productivity. Of much greater importance in the adaptation of plants to cold is the possibility of maintaining normal life activity by reducing the temperature optimum of physiological processes and the lower temperature limits at which these processes are possible. As can be seen from the example of optimal temperatures for photosynthesis and its lower temperature thresholds, these phenomena are well expressed in plants of cold habitats. Thus, in alpine and Antarctic lichens, the optimal temperature for photosynthesis is about 5°C; noticeable photosynthesis can be detected in them even at -10°C. At relatively low temperatures there is an optimum of photosynthesis in Arctic plants, high-mountain species, and early spring ephemeroids. In winter, at subzero temperatures, many coniferous tree species are capable of photosynthesis. In the same species, the temperature optimum of photosynthesis is associated with changing conditions: for example, in alpine and arctic populations of herbaceous perennials - Ohu ria digyna, Thalictrum alpinum and other species they are lower than those of the lowland species. Indicative in this regard is the seasonal shift in the optimum as the temperature rises from spring to summer and decreases from summer to autumn and winter.
At low temperatures, it is extremely important for plants to maintain a sufficient level of respiration - the energy basis for growth and repair of possible cold damage. Using the example of a number of plants in the Pamir highlands, it is shown that under these conditions, fairly intense respiration remains after exposure to temperatures from -6 to -10°C.
Another example of the resistance of physiological processes to cold is winter and pre-spring growth under snow in plants of the tundra, highlands and other cold habitats with a short growing season due to advance preparation. This phenomenon is extremely pronounced in the ephemeroids of forest-steppe oak forests (blues - Scilla sibirica, corydalis - Corydalis halleri, goose onions - Gagea lutea, clean - Ficariaverna etc.), in which, already at the beginning of winter, the growth of shoots with buds formed inside begins (first in the frozen soil, and then above the soil, inside the snow cover. The formation of generative organs does not stop in winter. As the snowmelt approaches, the rate of subsnow growth increases noticeably during the early “pre-spring”, when the forest still seems completely lifeless, thousands of sprouts of blueberries and goose onions already rise above the soil under the snow cover, reaching 2-7 cm in height by this time and ready to begin flowering as soon as the snow melts. The formation of chlorophyll in early spring ephemeroids also begins at low temperatures of the order of 0°C, still under snow.
Ecological differences in plant cold tolerance
In ecology and ecological physiology, the ability of a plant to tolerate low temperatures under experimental conditions for a certain period of time is used as one of the indicators of resistance to cold. A lot of data has been accumulated that makes it possible to compare plants in habitats with different temperature conditions. However, these data are not always strictly comparable, since the temperature that a plant can withstand depends, among other reasons, on the duration of its action (for example, a slight cold of the order of -3-5 ° C moderately heat-loving plant can withstand for several hours, but the same temperature can be destructive if it lasts for several days). In most experimental works, cooling of plants is adopted for a day or a similar period.
As can be seen from the following data and, the cold resistance of plants is very different and depends on the conditions in which they live.
One extreme example of cold resistance is the so-called “cryoplankton”. These are snow algae that live in the surface layers of snow and ice and, when multiplied en masse, cause it to color (“red snow,” “green snow,” etc.). IN active phases they develop at 0°C (in summer on the thawed surface of snow and ice). Limits of resistance to low temperatures from -36°C Chlamydomonas nivalis up to -40, -60°С Pediastrutn boryanum, Hormidium flaccidum. The cold resistance of the phytoplankton of the polar seas, which often overwinter in the ice crust, is equally great.
Alpine dwarf shrubs are distinguished by their great cold resistance - Rhododendron ferrugineum, Erica carnea etc. (-28, -36°С), coniferous tree species: for example, for pine Pinus strobus In the Tyrolean Alps, experiments recorded a record temperature: -78°C.
Plants from tropical and subtropical regions have very little cold resistance, where they do not experience low temperatures (with the exception of high mountains). Thus, for algae of tropical seas (especially shallow-water areas), the lower temperature limit lies in the range of 5-14 ° C (remember that for algae of the Arctic seas the upper limit is 16 ° C). Seedlings of tropical tree species die at 3-5°C. In many tropical thermophilic plants, for example, ornamental greenhouse species from the genera Gloxinia, Coleus, Achimenes etc., lowering the temperature to several degrees above zero causes the phenomenon of “colds”: in the absence of visible damage, after some time growth stops, leaves fall, plants wither and then die. This phenomenon is also known for thermophilic cultivated plants(cucumbers, tomatoes, beans).
Thermophilic molds from the genera have very little resistance to cold Mucor, Thermoascus, Anixia etc. They die in three days at a temperature of 5-6°C and cannot even withstand temperatures of 15-17°C for longer than 15-20 days.
Depending on the degree and specific nature of cold resistance, the following groups of plants can be distinguished.
Non-cold-tolerant plants
This group includes all those plants that are seriously damaged even at temperatures above freezing: algae of warm seas, some fungi and many leafy plants of tropical rain forests.
Non-frost-resistant plants
Although these plants tolerate low temperatures, they freeze out as soon as ice begins to form in the tissues. Non-frost-resistant plants are protected from damage only by anti-freeze agents. In the colder season, they increase the concentration of osmotically active substances in cell sap and protoplasm, as well as hypothermia, which prevents or slows down the formation of ice at temperatures down to about -7 ° C, and with constant supercooling even to lower temperatures. During the growing season, all leafy plants are not frost-resistant. Deep-sea algae, cold-sea and some freshwater algae, tropical and subtropical woody plants, and various species from warm-temperate regions are sensitive to ice formation throughout the year.
Ice-resistant plants
During the cold season, these plants tolerate extracellular freezing of water and associated dehydration. Some freshwater algae and intertidal algae, terrestrial algae, mosses of all climatic zones (even tropical) and perennials become resistant to ice formation. land plants areas with cold winters. Some algae, many lichens and various woody plants capable of being extremely hardened; then they remain undamaged even after prolonged severe frosts, and they can even be cooled to the temperature of liquid nitrogen.
plant needs
Air temperature significantly affects indoor plants, like any other living organisms on Earth. Most houseplants are native to the tropics or subtropics. In our latitudes they are kept in greenhouses where a special microclimate is maintained. These facts may lead you to mistakenly believe that all indoor flowers need to be maintained at a high temperature.
In fact, only a small part of plants can grow in our apartments at elevated temperatures (more than 24°C). This is explained by the fact that our conditions are noticeably different from the natural habitat in that they are more dry, as well as less intense and duration of illumination. Therefore, for comfortable growth of indoor plants at home, you need to make adjustments to the air temperature, which should be lower than in their homeland.
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1. Thermal regime for indoor plants
How does temperature affect plants?
Temperature is measured by the amount of heat and the duration of exposure to a certain temperature. For indoor plants, there are minimum and maximum temperature limits within which their normal development occurs (the so-called temperature range).
Cold air slows down physiological and biochemical processes- reducing the intensity of photosynthesis, respiration, production and distribution of organic substances. With increasing temperature, these processes become more active.
Natural temperature fluctuations
Rhythmic changes in the amount of heat occur both during the day (change of day and night) and throughout the year (change of seasons). Plants have adapted to similar fluctuations that exist in their natural habitats. Thus, inhabitants of the tropics react negatively to sudden changes in temperature, while inhabitants of temperate latitudes can tolerate significant fluctuations. Moreover, during the cold period they enter a period of rest, which is necessary for their further active development.
When there is a large difference between summer and winter, day and night temperatures (wide temperature range), it is best to grow ficus, aloe, clivia, sansevieria and aspidistra.
General rule: at night it should be 2-3°C cooler than during the day.
Optimal temperature
For normal growth of tropical flowering and decorative foliage plants, a temperature within 20-25 ° C is required (for all aroids, begonias, bromeliads, mulberries, etc.). Plants of the genus Peperomia, Coleus, Sanchetia, etc. develop best at 18-20°C. Residents of subtropics (zebrina, fatsia, ivy, aucuba, tetrastigma, etc.) will be comfortable at 15-18°C.
The most demanding of heat are tropical variegated plants - cordyline, codiaeum, caladium, etc.
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Winter temperatures and dormancy
In winter, some plants need coolness because... their growth process slows down or they are in a dormant state. For example, for eucalyptus and rhododendrons in winter, a temperature of 5-8°C is desirable, for hydrangea, primrose, cyclamen and pelargonium - about 10-15°C.
Another example. To make plants such as Scherzer's anthurium, Sprenger's asparagus and Wallis's spathiphyllum bloom even more intensively, in the fall during the dormant period, the air temperature is reduced to 15-18°C, and in January it is increased to 20-22°C.
A common reason for the lack of flowering is non-compliance with the natural rhythm of plant life - their dormant period.
For example, cacti, which in winter, at moderate temperatures and regular watering, give ugly growth and stop blooming. Hippeastrums stop laying buds, and cannot please with anything except green leaves.
Is soil temperature important?
Usually the temperature of the soil in the pot is 1-2°C less than the surrounding air. In winter, you need to make sure that the pots with plants do not get too cold and do not place them close to the window glass. When the soil is overcooled, the roots begin to poorly absorb water, which leads to their rotting and death of the plant. The best solution There will be a cork mat, wood, foam or cardboard stand under the pots.
For example, for a plant such as Dieffenbachia, the substrate temperature should be in the range of 24-27°C. And such as gardenia, ficus, eucharis, which love warm soil, you can pour warm water into trays.
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2. Groups of plants in relation to heat
Plants for cool places (10-16°C)
These include plants such as azalea, oleander, pelargonium, aspidistra, ficus, tradescantia, roses, fuchsia, primroses, aucuba, saxifrage, ivy, cyperus, chlorophytum, araucaria, asparagus, dracaena, begonia, balsam, bromeliads, Kalanchoe, coleus, arrowroot, ferns, shefflera, philodendron, hoya, peperomia, spathiphyllum, etc.
Plants for moderately warm places (17-20°C)
At moderate temperatures, anthurium, clerodendron, saintpaulia, wax ivy, pandanus, siningia, monstera, Liviston palm will develop well. coconut palm, aphelandra, ginura, rheo, pilea
Heat-loving plants (20-25°C)
The following feel most comfortable in the warmth: aglaonema, dieffenbachia, calathea, codiaeum, orchids, caladium, syngonium, dizygoteca, akalifa, etc. (read the information separately for each plant)
Plants that are dormant (5-8°C)
A group of plants that need rest and a decrease in temperature in winter time: succulents, laurel, rhododendron, fatsia, chlorophytum, etc.
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3. Failure to comply with thermal conditions
Temperature jumps
Sudden drops in temperature, especially by more than 6°C, are very harmful. For example, when the temperature drops to 10°C, Dieffenbachia spotted leaves begin to turn yellow and die; at 15°C, golden scindapsus stops growing.
As a rule, sudden changes in temperature cause rapid yellowing and falling of leaves. Therefore, if you ventilate a room in winter, try to remove all indoor plants from the windowsill.
Temperature too low
If the temperature is too low, the plants do not bloom for a long time or form underdeveloped flowers, the leaves curl up and become dark color and die off. The only exceptions can be succulents, including cacti, which are adapted to high daytime and low night temperatures.
It is worth considering that in the cold season the temperature on the windowsill may be 1-5°C lower.
Temperature too high
Hot air in winter with a lack of light also negatively affects tropical plants. Especially if the night temperature is higher than the day temperature. In this case, during breathing at night, excessive consumption occurs. nutrients accumulated during photosynthesis during the day. The plant becomes depleted, the shoots become unnaturally long, new leaves become smaller, old leaves dry out and fall off.
Plant growth is possible in a relatively wide range of temperatures and is determined by the geographical origin of the species. The temperature requirements of a plant change with age and are different for individual plant organs (leaves, roots, fruit elements, etc.). For the growth of most agricultural plants in Russia, the lower temperature limit corresponds to the freezing temperature of cell sap (about -1...-3 ° C), and the upper limit corresponds to the coagulation of protoplasmic proteins (about 60 ° C). Let us remember that temperature affects the biochemical processes of respiration, photosynthesis and other metabolic systems of plants, and graphs of the dependence of plant growth and enzyme activity on temperature are similar in shape (bell-shaped curve).
Temperature optimum for growth. The emergence of seedlings requires a higher temperature than for seed germination (Table 22).
22. Requirement of field crop seeds for biologically minimum temperatures (according to V.N. Stepanov)
Temperature, "C
seed germination 1st emergence
Mustard, hemp, camelina 0-1 2-3
Rye, wheat, barley, oats, 1-2 4-5
peas, vetch, lentils, china
Flax, buckwheat, lupine, beans, 3-4 5-6
noug, beets, safflower
Sunflower, perilla 5-6 7-8
Corn, millet, soybeans 8-10 10-11
Beans, castor beans, sorghum 10-12 12-15
X-wolfwort, rice, sesame 12-14 14-15
When analyzing plant growth, three cardinal temperature points are distinguished: minimum (growth is just beginning), optimal (most favorable for growth) and maximum temperature (growth stops).
There are plants that are love-loving - with minimum temperatures for growth of more than 10 "C and optimal 30-35 "C (corn, cucumber, melon, pumpkin), cold-resistant - with minimum temperatures for growth within 0-5 "C and optimal 25-31 " WITH. Maximum temperatures for most plants are 37-44 "C, for southern ones 44-50" C. With an increase in temperature by 10 °C in the zone of optimal values, the growth rate increases by 2-3 times. Increasing the temperature above the optimum slows down growth and shortens its period. The optimal temperature for the growth of root systems is lower than for above-ground organs. The optimum for growth is higher than for photosynthesis.
It can be assumed that at high temperatures there is a lack of ATP and NADPH, necessary for reduction processes, which causes growth inhibition. Temperatures that are optimal for growth may be unfavorable for plant development. The optimum for growth changes throughout the growing season and during the day, which is explained by the need for temperature changes fixed in the plant genome, which took place in the historical homeland of plants. Many plants grow more intensively at night.
Thermoperiodism. The growth of many plants is favored by changes in temperature during the day: increased during the day and decreased at night. So, for tomato plants, the optimal temperature is 26 °C during the day, and 17-19 °C at night. F. Vent (1957) called this phenomenon thermoperiodism. Thermal periods! - the plant’s reaction) to periodic changes in high and low temperatures, expressed in changes in growth processes and development! (M. *. Chailakhyan, 1982). For tropical plants, the difference between day and night temperatures is 3-6 °C, for plants in the temperate zone - 5-7 °C. This is important to consider when growing plants in the field, greenhouses and phytotrons, zoning crops and varieties of agricultural plants.
The alternation of high and low temperatures serves as a regulator of the internal clock of plants, as in photope1_iodism. Relatively low night temperatures increase the yield of potatoes (F. Vent. 1959), the sugar content of sugar beet roots, and accelerate the growth of the root system and lateral shoots of tomato plants (N. I. Yakushkin, 1980). Low temperatures may increase the activity of enzymes that hydrolyze starch in leaves, and the resulting soluble forms of carbohydrates move to the roots and side shoots.
