How low soil temperature affects plants. The effect of heat on plants. Plants requiring a cold room

Good day, dear friends!

We will talk about the effect of heat on plants in this article.

Excess or lack of heat is often the cause of poor plant growth and development. Low or too high temperatures sometimes cause irreversible processes in plant tissues. They are associated with a change in the structure of protein molecules in plant cells.

Changes that occur can be corrected in time if the temperature intensity is correctly adjusted and additional measures are used. For example, in conditions of excess heat, it is recommended not only to shade the affected plants, creating coolness, but also to spray more often. To prevent hypothermia, you should consider temporary greenhouses or shelters for plants.

Effect of lack of heat on plants

For different cultures, extreme values ​​of the same factor can cause different changes. So, for example, a low temperature causes reddening of the leaves, in ageratum and primroses it causes chlorosis, and in lilies - cracks on the stems and leaves. An early fall in temperature in autumn is also dangerous for irises. In such conditions, flowers may develop rot of the root collar of rhizomes. In general, with a lack of heat, almost all plants are stunted.

Some thermophilic crops grown in the open air in summer cannot withstand even a short-term lack of heat. Cooling down to -1 ° C causes freezing of the aboveground organs. These species include many southern plants that are grown in containers (yucca, palms, agaves) and carpet plants (clingia, echeveria, alternantera).

Effect of excess heat on plants

Too high temperatures are no less dangerous. This is especially true of bulbous and corms that have just been planted in the ground. Excess heat inhibits the development and growth of the root system. As a result, the underdeveloped underground part is unable to assimilate the required amount of chemical compounds from the soil. The aerial part of the bulbous begins to rapidly suffer from a lack of nutrition. The buds that have appeared cannot bloom for a long time and, in the end, dry up. The roots of such plants rot and die off.

It is noticed that not only bulbous, but also most flower crops at the beginning of the growing season require lower temperatures than in other periods. Moreover, at night all plants are more resistant to a lack of heat than during the day.

Among all ornamental and horticultural crops, plants stand out that safely tolerate both low and high temperatures. These include dracaena, aloe, clivia, aspidistra, epiphyllum, phyllocactus. These plants can be safely grown in both relatively cold and hot environments.

So, we can conclude that basically the effect of heat on plants is very large, therefore it is necessary to try to create the most acceptable temperature regime for each crop. See you, friends!

Completed by: Galimova A.R.

Effects of extreme temperatures on plants

In the course of evolution, plants have adapted quite well to the effects of low and high temperatures. However, these adaptations are not so perfect, so extreme extreme temperatures can cause some damage or even death of the plant. The range of temperatures acting on plants in nature is quite wide: from -77 ° C to + 55 ° C, i.e. is 132 ° C. The most favorable temperatures for the life of most terrestrial organisms are +15 - + 30 ° С.

High temperatures

Heat-resistant - mainly lower plants, such as thermophilic bacteria and blue-green algae.

This group of organisms is able to withstand temperatures up to 75-90 ° C;

The resistance of plants to low temperatures is subdivided into:

Cold resistance;

Frost resistance.

Cold resistance of plants

the ability of heat-loving plants to tolerate low positive temperatures. Heat-loving plants suffer greatly at positive low temperatures. The external symptoms of plant suffering are wilting of leaves, the appearance of necrotic spots.

Frost resistance

the ability of plants to tolerate negative temperatures. Biennial and perennial plants growing in the temperate zone are periodically exposed to low negative temperatures. Different plants have unequal resistance to this effect.

Frost-resistant plants

Influence on plants of low temperatures

With a rapid decrease in temperature, ice formation occurs inside the cell. With a gradual decrease in temperature, ice crystals are formed primarily in the intercellular spaces. The death of the cell and the organism as a whole can occur as a result of the fact that the ice crystals formed in the intercellular spaces, drawing water from the cell, cause its dehydration and at the same time exert mechanical pressure on the cytoplasm, which damages the cell structures. This causes a number of consequences - a loss of turgor, an increase in the concentration of cell juice, a sharp decrease in cell volume, a shift in pH values ​​in an unfavorable direction.

Influence on plants of low temperatures

Plasmalemma loses its semi-permeability. The work of enzymes localized on the membranes of chloroplasts and mitochondria and the processes of oxidative and photosynthetic phosphorylation associated with them are disrupted. The intensity of photosynthesis decreases, the outflow of assimilates decreases. It is the change in the properties of membranes that is the first cause of cell damage. In some cases, membrane damage occurs during thawing. Thus, if the cell has not passed the hardening process, the cytoplasm coagulates due to the combined effect of dehydration and mechanical pressure of ice crystals formed in the intercellular spaces.

Adaptation of plants to negative temperatures

There are two types of devices for the action of negative temperatures:

avoiding the damaging effect of the factor (passive adaptation)

increased survival (active adaptation).

plant needs

Air temperature significantly affects indoor plants, as well as 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 can lead to the mistaken belief that all indoor flowers need to maintain a high air temperature.

In fact, only a small part of the plants can grow in our apartments at elevated temperatures (over 24 ° C). This is due to the fact that our conditions are noticeably different from the natural habitat in greater dryness, as well as less intensity and duration of illumination. Therefore, for the comfortable growth of indoor plants at home, you need to make an amendment to the air temperature, which should be lower than in their homeland.

1. Thermal conditions for indoor plants

How does temperature affect plants?

The temperature regime 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 - a decrease in the intensity of photosynthesis, respiration, production and distribution of organic matter. With an increase in temperature, these processes are activated.

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 such fluctuations that exist in their natural habitats. So, the inhabitants of the tropics react negatively to sudden changes in temperature, and the inhabitants of temperate latitudes can tolerate their significant fluctuations. Moreover, during the cold period, they have a period of rest, which is necessary for their further active development.

With a large difference between summer and winter, day and night temperatures (wide temperature range), it is best to grow ficuses, aloe, clivia, sansevier and aspidistra.

General rule: it should be 2-3 ° C cooler at night than during the day.

Optimum temperature

For the normal growth of tropical flowering and decorative deciduous plants, a temperature of 20-25 ° C is required (for all aroids, begonias, bromeliads, mulberries, etc.). Plants of the genus Peperomia, Coleus, Sanchecia, etc. develop best at 18-20 ° C. Residents of the subtropics (zebrina, fatsia, ivy, aucuba, tetrastigma, etc.) will feel comfortable at 15-18 ° C.

The most demanding for heat are tropical variegated plants - cordilina, codieum, caladium, etc.

Winter temperatures and dormant periods

In winter, some plants need coolness because their growth process is slowed down or they are dormant. 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 force plants such as Scherzer's anthurium, Sprenger's asparagus and Wallis spathiphyllum to 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 raised to 20-22 ° C.

A common reason for the lack of flowering is non-observance of the natural rhythm of plant life - their dormant period.

For example, cacti, which in winter at moderate temperatures and regular watering, give ugly growths and stop blooming. Hippeastrum ceases to lay buds, and cannot please with anything except green leaves.

Is soil temperature important?

Typically, the temperature of the ground in a pot is 1–2 ° C lower than that of the surrounding air. In winter, make sure that the pots with plants are not overcooled and do not place them close to the window glass. When the soil is overcooled, the roots begin to absorb water poorly, which leads to their rotting and the death of the plant. The best solution is a cork mat, wood, foam or cardboard pot holder.

For example, for a plant such as Dieffenbachia, the substrate temperature should be between 24-27 ° C. And such as gardenias, ficuses, eucharis, which love warm soil, you can pour warm water into trays.

2. Plant groups 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, calanie coleus, arrowroot, ferns, sheflera, 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, coconut palm, aphelandra, ginura, rheo, pilea will develop well

Heat-loving plants (20-25 ° С)

Feel most comfortable in the warmth: aglaonema, dieffenbachia, calathea, codieum, orchids, caladium, syngonium, dizigoteca, akalifa, etc. (read the information separately for each plant)

Plants that are dormant (5-8 ° C)

A group of plants that need rest and lower temperatures in winter: succulents, laurel, rhododendron, fatsia, chlorophytum, etc.

3. Non-observance of the thermal regime

Temperature jumps

Sudden drops in temperature are very harmful, especially by more than 6 ° C. For example, when the temperature drops to 10 ° C in Dieffenbachia spotted, the leaves begin to turn yellow and die off; at 15 ° C the golden scindapsus stops growing.

As a rule, sudden changes in temperature cause rapid yellowing and leaf fall. Therefore, if you ventilate the room in the 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, acquire a dark color and die off. The only exceptions are succulents, including cacti, which are adapted to high daytime and low nighttime temperatures.

It should be borne in mind that in the cold season, the temperature on the windowsill may be 1-5 ° C lower.

Too high temperature

Hot air in winter with a lack of light also negatively affects tropical plants. Especially if the nighttime temperature is higher than the daytime. In this case, during breathing at night, there is an overexpenditure of nutrients accumulated during photosynthesis during the day. The plant is depleted, shoots become unnaturally long, new leaves become smaller, old ones dry up and fall off.

The temperature of the soil or artificial growth medium is of great importance when growing plants. Both high and low temperatures are unfavorable for the vital activity of the root. At low temperatures, the respiration of the roots is weakened, as a result of which the absorption of water and nutrient salts is reduced. This leads to wilting and stopping the growth of the plant.

Cucumbers are especially sensitive to a decrease in temperature - a decrease in temperature to 5 ° C destroys cucumber seedlings. Leaves of adult plants wither and get burned at low temperatures of the nutrient solution in sunny weather. For this culture, the temperature of the nutrient solution should not be reduced below 12 ° C. Usually, when growing plants in greenhouses in winter, the nutrient solution stored in the tanks is at a low temperature and should be warmed up to at least the ambient temperature. The most favorable temperature of the solution used for growing cucumbers should be considered 25-30 ° C, for tomatoes, onions and other plants - 22-25 ° C.

If in winter it is necessary to warm up the substrate on which the cultivation is taking place, then in the summer, on the contrary, the plants may suffer due to its high temperature. Already at 38-40 ° C, the absorption of water and nutrients is suspended, the plants wither and may die. It is impossible to allow the heating of solutions and substrate to such a temperature. The roots of young seedlings are especially affected by high temperatures. For many crops, the temperature of 28-30 ° is already destructive.

If there is a danger of overheating, it is useful to moisten the surface of the soil with water, when it evaporates, the temperature decreases. In the summer, in the practice of greenhouse farming, spraying of glass with a lime solution is widely used, which scatters the direct rays of the sun and saves the plants from overheating.

Sources of

• Growing plants without soil / V.A. Chesnokov, E.N.Bazyrina, T.M. Bushueva and N.L. Ilyinskaya - Leningrad: Leningrad University Publishing House, 1960. - 170 p.

Along with the thermal characteristics of the environment, it is necessary to know the temperature of the plants themselves and its changes, since it is this temperature that represents the true temperature background for physiological processes. The temperature of the plants is measured using electrothermometers having miniature semiconductor sensors. In order for the sensor not to affect the temperature of the organ being measured, it is necessary that its mass be many times less than the mass of the organ. The sensor should also be fast and responsive to temperature changes. Sometimes thermocouples are used for this purpose. The sensors are either applied to the surface of the plant, or "implanted" into the stems, leaves, under the bark (for example, to measure the temperature of the cambium). At the same time, the ambient temperature must be measured (shading the sensor).

The temperature of the plants is highly variable. Due to turbulent currents and continuous changes in the temperature of the air immediately surrounding the leaf, the effect of wind, etc., the temperature of the plant varies with a range of several tenths or even whole degrees and with a frequency of several seconds. Therefore, “plant temperature” should be understood as a more or less generalized and sufficiently conventional value characterizing the general level of heating. Plants, like poikilothermic organisms, do not have their own stable body temperature. Their temperature is determined by the thermal balance, that is, the ratio of energy absorption and release. These values ​​depend on many properties of both the environment (the size of the arrival of radiation, the temperature of the ambient air and its movement), and the plants themselves (color and other optical properties of the plant, the size and arrangement of leaves, etc.). The primary role is played by the cooling effect of transpiration, which prevents very strong overheating in hot habitats. This can be easily shown in experiments with desert plants: one has only to smear with petroleum jelly the surface of the leaf on which the stomata are located, and the leaf dies before our eyes from overheating and burns.

As a result of the action of all these reasons, the temperature of the plants usually differs (sometimes quite significantly) from the temperature of the surrounding air. In this case, three situations are possible:

• The temperature of the plant is higher than the temperature of the ambient air ("supratemperature" plants, in the terminology of O. Lange),
• · Below it ("subtemperature"),
• · Equal to or very close to it.

The first situation occurs quite often in a wide variety of conditions. A significant excess of plant temperature over air temperature is usually observed in massive plant organs, especially in hot habitats and with weak transpiration. Large fleshy stems of cacti, thickened leaves of milkweed, stonecrops, rejuvenated, in which evaporation of water is very insignificant, heat up strongly. So, at an air temperature of 40-45 ° C, desert cacti heat up to 55-60 ° C; in temperate latitudes on summer days, the succulent leaves of plants from the genera Sempervivum and Sedum often have a temperature of 45 ° C, and inside the rosettes they are young up to 50 ° C. Thus, the excess of the plant temperature over the air temperature can reach 20 ° C.

Various fleshy fruits are strongly heated by the sun: for example, ripe tomatoes and watermelons are 10-15 ° C warmer than the air; the temperature of red fruits in ripe arum cobs - Arum maculatum reaches 50 ° C. An increase in temperature inside the flower with a more or less closed perianth, which retains the heat that is released during respiration, is quite noticeable. Sometimes this phenomenon can have a significant adaptive value, for example, for flowers of forest ephemeroids (woodpecker, corydalis, etc.), in early spring, when the air temperature barely exceeds 0 ° C.

The temperature regime of such massive formations as tree trunks is also peculiar. In solitary trees, as well as in deciduous forests, in the leafless phase (in spring and autumn), the surface of the trunks heats up strongly during the daytime, and to the greatest extent from the southern side; the temperature of the cambium here can be 10-20 ° C higher than on the northern side, where it has the temperature of the ambient air. On hot days, the temperature of dark spruce trunks rises to 50-55 ° C, which can cause cambium burns. The readings of thin thermocouples implanted under the bark made it possible to establish that tree trunks are protected in different ways: in birch, the temperature of the cambium changes faster in accordance with fluctuations in the outside air temperature, while in pine it is more constant due to the better heat-shielding properties of the bark. Heating of tree trunks and leafless spring forest significantly affects the microclimate of the forest community, since the trunks are good heat accumulators.

The excess of plant temperature over air temperature is found not only in strongly warmed, but also in colder habitats. This is facilitated by a dark color or other optical properties of plants that increase the absorption of solar radiation, as well as anatomical and morphological features that contribute to a decrease in transpiration. Arctic plants can warm up quite noticeably: one example is the dwarf willow - Salix arctica in Alaska, in which the leaves are 2-11 ° C warmer than the air during the day, and by 1-3 ° C even during the night hours of the polar "round-the-clock day". Another interesting example of heating under the snow: in the summertime in Antarctica, the temperature of lichens is above 0 ° C even under a layer of snow of more than 30 cm.Obviously, in such harsh conditions, natural selection retained forms with the darkest color, in which, due to such heating, a positive balance of carbon dioxide gas exchange.

The needles of coniferous trees in winter can be heated quite significantly by the sun's rays: even at negative temperatures, an excess of 9-12 ° C over the air temperature is possible, which creates favorable opportunities for winter photosynthesis. It has been shown experimentally that if a strong radiation flux is created for plants, then even at a low temperature of the order of -5, -6 ° C, the leaves can heat up to 17-19 ° C, that is, photosynthesize at quite "summer" temperatures.

A decrease in plant temperature in comparison with the ambient air is most often observed in highly illuminated and warmed habitats (steppes, deserts), where the leaf surface of plants is greatly reduced, and increased transpiration helps to remove excess heat and prevents overheating. In intensively transpiring species, the cooling of leaves (the difference with the air temperature) reaches 15 ° C. This is an extreme example, but a decrease by 3–4 ° C can also prevent destructive overheating.

In the most general terms, we can say that in hot habitats the temperature of the aboveground parts of plants is lower, and in cold ones, higher than the air temperature. This pattern can be traced in the same species: for example, in the cold zone of the mountains of North America, at altitudes of 3000-3500 m, the plants are warmer, and in the low mountains, colder than the air.

The coincidence of the temperature of plants with the temperature of the surrounding air is much less common in conditions that exclude a strong influx of radiation and intense transpiration, for example, in herbaceous plants under the canopy of shady forests (but not in the glare of the sun), and in open habitats - in cloudy weather or with rain.

There are different biological types of plants in relation to temperature. In thermophilic, or megathermal (thermophilic) plants, the optimum lies in the area of ​​elevated temperatures. They live in areas of tropical and subtropical climates, and in temperate zones - in highly warmed habitats. For cryophilic, or microthermal (cold-loving) plants, low temperatures are optimal. These include species that live in polar and high mountain areas or occupy cold ecological niches. Sometimes an intermediate group of mesothermal plants is distinguished.