light-loving plants - heliophytes, plants growing on open places and not enduring prolonged shading; For normal growth, they need intense solar or artificial radiation. Adult heliophytes, as a rule, are more photophilous than young specimens.
Light-loving plants include both herbaceous (large plantain, water lily, etc.) and woody (larch, acacia, etc.) plants, early spring - steppes and semi-deserts, and cultivated - corn, sorghum, sugar cane, etc. Woody or shrub heliophytes usually form sparse plantings.
Leaves - equilateral, narrow shiny; shoots are short; there are hairs.
Adaptation to intense illumination is provided by the peculiarities of the morphology and physiology of photophilous plants. They usually have rather thick leaves with small-celled columnar and spongy parenchyma and a large number stomata, often located at a large angle to the light (sometimes almost vertically); the leaf is shiny (due to the developed cuticle) or with pubescence.
In photophilous plants, the skin does not contain chlorophyll, and the stomata are located on the lower surface of the leaf. Pelargonium (geranium), violet and a number of other plants have hairs that scatter, bright direct light, thereby protecting the leaves from overheating. In the cells of light leaves, there are many small chloroplasts located along the walls - this explains the color of the leaves.
In light-loving plants, lignification of shoots with the formation of thorns and spines is much more common (compared to shade-loving ones). Characterized by a large number of stomata, which are concentrated mainly on bottom side sheet; multilayered palisade parenchyma is made up of small cells. Compared with shade-loving plants, heliophytes have a significantly higher content of chloroplasts in leaf cells - from 50 to 300 per cell; the total surface of leaf chloroplasts is tens of times greater than its area. Due to this, a high intensity of photosynthesis is ensured - distinguishing feature heliophytes. Another morphological difference from shade-loving plants is the greater content of chlorophyll per unit area and less - per unit mass of the sheet.
Light-loving plants (heliophytes) often have shoots with short internodes, strongly branching, often rosette. The leaves of heliophytes are usually small or with a dissected leaf blade, with a thick outer wall of epidermal cells, often with a wax coating or dense pubescence, with a large number of stomata per unit area, often submerged, with a dense network of veins, with well-developed mechanical tissues. In a number of plants, the leaves are photometric, that is, they are turned with an edge towards the midday rays or can change the position of their parts depending on the height of the Sun. So, in the steppe plant Sophora, the leaves of an unpaired pinnate leaf on a hot day are raised up and folded, in the Russian cornflower, segments of a pinnate leaf behave in the same way.
The optical apparatus of heliophytes is better developed than that of sciophytes, has a large photoactive surface and is adapted to a more complete absorption of light. Usually their leaves are thicker, the cells of the epidermis and mesophyll are smaller, the palisade parenchyma is two-layered or multi-layered (in some savannah plants of West Africa - up to 10 layers), often developed under the upper and lower epidermis. Small chloroplasts with a well-developed granal structure in large numbers (up to 200 or more) are located along the longitudinal walls.
There is less chlorophyll per dry weight in the leaves of heliophytes, but they contain more pigments of the I pigment system and chlorophyll P700. The ratio of chlorophyll a to chlorophyll b is approximately 5:1. Hence the high photosynthetic capacity of heliophytes. The compensation point lies in the region of higher illumination. The intensity of photosynthesis reaches its maximum in full sunlight. In a special group of plants - heliophytes, in which CO2 is fixed by C4-dicarboxylic acids, light saturation of photosynthesis is not achieved even under the strongest illumination. These are plants from arid regions (deserts, savannahs). There are especially many C4 plants among the families of bluegrass, sedge, aizaceae, purslane, amaranth, haze, clove, and euphorbia. They are capable of secondary fixation and reutilization of CO2 released during light respiration, and can photosynthesize at high temperatures and with closed stomata, which is often observed during the hot hours of the day.
shade tolerant plants - plants (woody, many herbaceous under the canopy of hardwoods, greenhouses, etc.), which tolerate some shading, but develop well in direct sunlight. With age, as well as high latitudes, mountains, in a drier climate, shade tolerance decreases. A number of plants under the forest canopy (for example, wild hoof, gout, etc.) in early spring, before the leaves of the tree layer open, are physiologically photophilous, and in summer, when the canopy is closed, they are shade-tolerant. Physiologically, shade-tolerant plants are characterized by a relatively low intensity of photosynthesis.
Shade-tolerant plants (sciophytes) - are constantly in conditions of strong shading. At illumination of 0.1–0.2%, only mosses and selaginella can grow. Club mosses are content with 0.25-0.5% of the total daylight, and flowering plants are usually found where the illumination on cloudy days reaches at least 0.5–1% (begonias, touchy, herbs from the ginger, madder, commelin families).
Leaves shade-tolerant plants have a number of anatomical and morphological features: the columnar and spongy parenchyma is poorly differentiated, enlarged intercellular spaces are characteristic - the cells contain a small number (10-40) of chloroplasts, the surface size of which varies within 2-6 cm 2 per 1 cm 2 of leaf area. The epidermis is rather thin, single-layered, the cells of the epidermis may contain chloroplasts (which is never found in heliophytes). The cuticle is usually thin. Stomata are usually located on both sides of the leaf with an insignificant predominance on the reverse side (in photophilous plants, as a rule, stomata are absent on the front side or are located mainly on the reverse side). Compared with heliophytes, shade-tolerant plants have a significantly lower content of chloroplasts in leaf cells - on average, from 10 to 40 per cell; the total surface of leaf chloroplasts slightly exceeds its area (2-6 times; while in heliophytes, the excess is tens of times). Some shade-tolerant plants are characterized by the formation of anthocyanin in the cells when growing in bright sun, which gives a reddish or brownish color to the leaves and stems, which is uncharacteristic in vivo habitat. In others, when growing in direct sunlight, a paler color of the leaves is noted. The leaves of shade-tolerant plants are thin, the cells and chloroplasts in them are large.
In northern broad-leaved and dark coniferous forests the canopy of a dense forest stand can pass only 1–2% of the PAR, changing it spectral composition. Blue and red rays are absorbed most strongly, and relatively more yellow-green, far red and infrared rays are transmitted. Poor illumination is combined with high air humidity and high CO2 content, especially near the soil surface. The sciophytes of these forests are green mosses, club mosses, common sorrel, wintergreens, two-leaved mullet, etc.
Sciophytes have less chlorophyll P700 than heliophytes. The ratio of chlorophyll a to chlorophyll b is approximately 3: 2. With less intensity, they have such physiological processes as transpiration and respiration. The intensity of photosynthesis, having quickly reached a maximum, ceases to increase with increasing illumination, and in very bright light it can even decrease.
In deciduous shade-tolerant tree species and shrubs (pedunculate oak, heart-shaped linden, common lilac, etc.), the leaves located along the periphery of the crown have a structure similar to the structure of heliophyte leaves and are called light, and in the depths of the crown - shadow leaves with a shadow structure similar to the structure of sciophyte leaves.
The appearance of shade-tolerant plants also differs from light-loving ones. Shade-tolerant plants usually have wider, thinner, softer leaves to capture more diffused sunlight. In shape, they are usually flat and smooth (whereas heliophytes often have folded, tubercular leaves). The horizontal arrangement of foliage is characteristic (in heliophytes, leaves are often located at an angle to the light) and sheet mosaic. Forest grasses are usually elongated, tall, have an elongated stem.
Many shade-tolerant plants have a high plasticity of their anatomical structure, depending on the illumination (first of all, this concerns the structure of the leaves). For example, in beech, lilac, and oak, leaves formed in the shade usually have significant anatomical differences from leaves grown in bright sunlight. The latter in their structure resemble the leaves of heliophytes (such leaves are defined as "light", as opposed to "shadow").
Changes in the attitude of plants to light
Facultative heliophytes, or shade-tolerant plants, depending on the degree of shade tolerance, have adaptive features that bring them closer either to heliophytes or to sciophytes. This group includes some meadow plants, forest grasses and shrubs that grow both in shaded areas of the forest and in forest clearings, edges, clearings. In bright places, they often grow stronger, however optimal use PAR they do not occur in full sunlight.
In trees and shrubs, the shadow or light structure of the leaf is often determined by the lighting conditions of the previous year when the buds are set: if the buds are set in the light, then the light structure is formed, and vice versa.
If the light regime regularly changes periodically in the same habitat, plants in different seasons can manifest themselves either as light-loving or shade-tolerant.
In spring, in oak forests, 50–60% of solar radiation penetrates under the forest canopy. The leaves of the rosette shoots of common goutweed have a light structure and are characterized by a high intensity of photosynthesis. At this time they create the main part organic matter yearly production. The leaves of summer goutweed, appearing with a developed tree canopy, under which an average of 3.5% of solar radiation penetrates, have a typical shadow structure, and their photosynthesis intensity is much lower, by 10–20 times. A similar duality in relation to light is also manifested by hairy sedge, light-loving in spring and shade-tolerant in summer. Apparently, this is also characteristic of other plants of oak broad grasses.
The attitude to the light regime changes in plants and in ontogeny. Seedlings and juvenile plants of many meadow species and tree species are more shade tolerant than adults.
Sometimes the requirements for the light regime change in plants when they find themselves in different climatic and edaphic conditions. Thus, the usual shade-tolerant plants of the coniferous forest - blueberries, European week-grass and some others - in the tundra acquire the characteristics of heliophytes.
On the household plots many shaded places: under trees, along fences and buildings. They can be used to create beautiful compositions of shade-loving plants on them.
Shade-loving plants are considered to be plants that, for normal development, have enough rarefied sunlight penetrating them through the crown of trees or they are in the sun. just a few hours a day. They have bright juicy green foliage, because it does not fade in the sun, if they are planted in sunny areas, they do not grow well.
Plants for shade can be divided into flowering and decorative foliage.
To blooming shade-loving include: lily of the valley, dicentra, garden geranium, anemone, foxglove, large astration, primrose, aquilegia, astilbe, kupena, beautiful hydrangea, periwinkle, volzhanka, elecampane.
Decorative leafy shade-loving are: hostas, geyhera, ferns, bergenia, bruner.
Such creepers grow well in the shade: actinidia kolomikta, parthenocissus, Chinese magnolia vine. They decorate fences and walls of household premises.
Shaded areas of the garden can be decorated for the summer season with flowers in pots, such as ever-flowering begonia, lobelia, balsams and low-hardy hydrangeas. In autumn, at the end of the summer season, they are brought into the house, where they winter well until the next summer.
Let's take a closer look at shade-loving plants.
unpretentious perennial plant that enchants with its tenderness. She has beautiful not only flowers of various colors, but also openwork foliage.
Aquilegia is unpretentious in the choice of soil, grows on loose, moist soils, but when compost or humus is added to the soil, it grows powerful and blooms profusely. Care is moderate watering followed by loosening the soil and top dressing once every 3 weeks. Propagated by seeds, division of the bush.
Having planted a geranium in the most unattractive place, in a year you will not recognize it. A rapidly growing plant with its lush, openwork bushes fills the free space so tightly that even weeds cannot break through.
Perennial garden geranium popular among gardeners due to:
- drought and frost resistance
- long flowering and rich color scheme, which lacks so far only yellow and orange colors
- longevity and resistance to diseases and pests
Geranium Care consists of watering and fertilizing. Nitrogen fertilizers are applied in early spring, and complex mineral fertilizers are applied once a month throughout the season.
shade-tolerant perennial. When planted under trees, flowering is delayed, but the color of the flowers is brighter. Moisture-loving, responds well to fertilization. A few years after planting, the dicentra forms a powerful, profusely flowering bush.
Waterlogging is detrimental, fleshy roots rot.
It is better to cover the dicentra for the winter, in order to avoid freezing. It propagates by dividing the overgrown bushes and cuttings.
Perennial frost-resistant a plant 1.5-2 m high and a bush up to 1 m wide, very decorative, one might even say spectacular. A sweet honey aroma emanates from blooming white panicles, and openwork foliage adorns the Volzhanka until the very frost.
Volzhanka is unpretentious, but grows best on fertile soils . It is quite drought-resistant, but waterlogging of the soil is not terrible for it. After flowering throughout June, faded panicles must be removed so that the plant does not lose its decorative effect. In late autumn, the stems are cut at a level of 5 cm from the soil.
Hydrangea is a luxurious flowering shrub, one of the most impressive in its flowering in the garden. Hydrangea loves acidic, nutritious and well-moistened soil. To maintain the acidity of the soil and moisture in it, it is necessary to mulch with fallen needles, sawdust, and peat.
The shrub is practically not affected by diseases and pests.
Hydrangea blooms from late June until frost with large flowers.
There are many hydrangeas: tree-like, paniculate (the most winter-hardy), petiolate, large-leaved. Most hydrangeas are winter-hardy, but shelter for the winter does not hurt. Even if they freeze slightly in harsh winters, they are easily restored during the season with good care.
perennial undemanding in the care of a plant that brings to flower beds and gardens bright accent. Pleases with its variegated foliage from spring to autumn. The composition of the soil for planting special significance does not have, the main thing is light and without stagnant water.
Once a month you can feed, but the dose of complex fertilizer should be halved compared to others. sockets in winter needs to be twisted and mulched.
Flower growers appreciate her for:
- compactness, frost resistance and unpretentiousness;
- a wide variety of varieties and colors;
- flower bed decoration all season and good compatibility with other colors;
- ease and speed in reproduction;
- absence of diseases and pests;
- very good in containers.
Hosts do not like frequent division of bushes. It is enough to perform this procedure once every five years.
The variety of colors of hosta leaves is impressive: from pale green to dark green, there are variegated varieties with white and yellow stripes. Hostas also vary in size, from dwarf to giant. The height varies from 5 cm to 1.5-2 m. There is something to choose from.
Astilbe is the little shadow princess. Plant moisture-loving and unpretentious. Astilbe is beautiful, both in bloom and before and after due to its carved foliage. After flowering, faded inflorescences can not be removed, they also decorate it.
Astilba blooms with white, pink, red panicle inflorescences in the first half of summer. The soil for cultivation should be fertile and moisture-intensive. It is advisable to mulch the plant to maintain soil moisture.
Every 5 years, astilba needs to be rejuvenated by dividing the bushes and transplanting to a new place.
The fern is herbaceous perennial shade a plant that loves moisture and shady places.
At the same time, the plant is drought-resistant, if the plant dries out during intense heat without watering, next spring it will again delight you with its appearance. Planted in the shade of trees, they give the site the appearance of a tropical forest.
Actinidia - kolomikta
perennial fragrant deciduous liana, the variegated color of the leaves gives it a decorative effect. Actinidia shoots require support and can grow up to 7 m in height. Actinidia is also valuable for its healthy, tasty fruits similar to kiwi.
For planting, seedlings are used no older than 4 years of age, because. adult plants do not take root.
To obtain a harvest of berries, it is necessary to plant 2 plants (male and female), because. dioecious plant.
On summer days, shady areas of the garden are arranged and used for relaxation, where you can enjoy the coolness, hide from the languishing heat and the scorching sun. The recreation area can be decorated with shade-loving plants, creating flower beds or islands of lush greenery. The choice of plants for this is large and varied.
Lighting is the most important factor in the development of plants, since only with its help the process of photosynthesis can be carried out. Each plant has its own sensitivity to light, but in general, in relation to it, they are divided into sun-loving, light-loving, shade-tolerant and shade-loving. We will introduce you to all four categories of indoor plants and tell you where in the apartment they are best placed.
Not all plants can tolerate direct sunlight for a long time. The most hardy of them come from arid places, where they almost all year round grow under open sky and bright sun. Sun-loving plants grown in room culture can also include those that are naturally found in the upper tier of subtropical and tropical forests. That's far from full list sun-loving ornamental leafy plants that can be found in room culture:
- agave;
- aloe;
- baban;
- bokarney;
- washingtonia;
- Zamioculcas;
- karyota;
- croton;
- coffee;
- coconut;
- liviston;
- likuala;
- spurge;
- rapis;
- sansevieria;
- yucca;
- canarian date.
Of the flowering houseplants, they love the sun more than others:
- adenium;
- hibiscus;
- bougainvillea;
- hippeastrum;
- hemanthus;
- geranium;
- dendrobium orchid;
- datura;
- jasmine;
- clivia;
- medinilla;
- the Rose;
- strelitzia;
- hoya.
Sun loving plants are pomegranate, all cacti and succulents, as well as all citrus fruits.
You should know that some plants are photophilous, but they can also be shade-tolerant, such as sansevieria. So don't be surprised if you see the same plant in different groups.
You can keep sun-loving plants on south, southeast and southwest window sills, however, in summer time it is impossible to allow direct sunlight to fall on the flowers for a long time, it is better to shade them in the afternoon hours with a light curtain.
As for the length of daylight hours, tropical crops need twelve hours of daylight in summer and eight hours of daylight in winter. Therefore, light-loving plants from the end of autumn may need additional artificial lighting.
It is advisable to keep subtropical crops cool in winter at 8-12 ºC, otherwise their shoots will begin to stretch, the leaves become small and may be deformed. But if they have to winter in warmth, then they will have to provide them with a twelve-hour daylight hours.
These plants love sunlight, but prefer it in the form of scattered or indirect rays that do not burn, but scatter as they pass through upper tier rainforest to the second tier, where light-loving cultures live. This category includes most of the indoor plants, including such representatives of decorative foliage, such as:
- maidenhair;
- araucaria;
- asparagus;
- ginura;
- dizygoteka;
- croton;
- dieffenbachia;
- dracaena;
- zebrina;
- coleus;
- coffee;
- cordelina;
- monstera;
- peperomia;
- rapis;
- sansevieria;
- scindapsus;
- netcreasia;
- tradescantia;
- ficus variegated;
- philodendron;
- chlorophytum;
- chrysalidocarpus;
- hamedorea;
- chefler.
From flowering crops the most light-loving are:
- a pineapple;
- azalea;
- abutilone;
- anthurium;
- ardisia;
- aphelandra;
- begonia;
- Beloperone;
- balsam;
- hypocytra;
- hibiscus;
- gardenia;
- gloriosa;
- hydrangea;
- datura;
- zantedeschia;
- jasmine;
- acid;
- calceolaria;
- capsicum;
- muraya;
- medinilla;
- nerter;
- oleander;
- passionflower;
- nightshade;
- poinsettia;
- ripsalidopsis;
- saintpaulia;
- stephanotis;
- spathiphyllum;
- fuchsia;
- hoya;
- chrysanthemum;
- cyclamen.
Sun-loving also all citrus and bromeliads.
These plants are best placed on the western and eastern windowsills, on which the light falls only in the morning or in the evening, and therefore the sun's rays are not as burning as during the day, from 12 to 16 hours. Diffused lighting stimulates the intensive laying of flower buds. We need bright diffused light to preserve the original colors and variegated plants.
These categories include crops that can decorate your northern window sills: although they do not fall on the sun's rays, diffused light through windows oriented to the north comes in abundance. You can place these plants in partial shade, next to a sunny window. If you keep them in the shade near the north window, then they will begin to lag behind in development, and to prevent this from happening, you need to periodically take them out for a while under bright diffused light. Shade-tolerant decorative leafy plants include:
- aglaonema;
- alocasia;
- maidenhair;
- asparagus;
- aspidistra;
- asplenium and other ferns;
- begonia;
- hypoesthesia;
- ginura;
- digisotheca;
- dieffenbachia;
- dark-leaved dracaena;
- zebrina;
- cordelina;
- ctenant;
- white-veined arrowroot;
- monstera;
- dark-leaved ivy;
- sansevieria;
- selanginella;
- syngonium;
- stromante;
- scindapsus;
- tradescantia;
- ficus;
- philodendron;
- fatsia;
- fatheader;
- fittonia;
- cissus.
But among the flowering houseplants, there are not so many shade-tolerant and shade-loving ones:
- bilbergia;
- vriesia;
- Guzmania;
- acid;
- orchid ludisia;
- saintpaulia.
In winter, the intensity of sunlight decreases, and even shade-loving crops can suffer from a lack of light, so move them as close as possible to well-lit windows. But with the onset of spring, the sun becomes especially dangerous for shade-loving and shade-tolerant plants, since the rays increase in intensity, reflected from the snow, and the plants have not yet had time to adapt to the change in lighting. So that the flowers do not suffer, return them to the northern windowsill or to the usual partial shade.
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Light is the main, vital factor that determines the development of plants. It is a component of photosynthesis - with the help of chlorophyll (a pigment contained in the green part of plants), the energy of the beam is converted into growth energy.
The ratio of plants from different climatic zones different to the world. Types of open habitats of the tropics and subtropics require very high illumination, do not tolerate the slightest shading. For example succulents, cacti, many palms, some bromeliads, orchids). Plants of the lower tiers of humid tropical and subtropical forests (many arrowroot, aroid, ferns, begonias) in culture need more or less strong shading from direct sunlight.
Depending on the light consumption, all plants are divided into 3 groups:
- neutral,
- long day plants
- short day plants.
neutral plants start to bloom if they receive enough light for a long period of time (fairly bright light for 8 hours, and even better 12-16 hours). Depending on the species, neutral plants require different amounts of light to bloom. Example: begonia, abutilon, asparagus.
Long day plants only when the ovary is formed and flowers appear, when for several weeks they receive the so-called minimum light per day, the value of which is not the same for different plants and is approximately from 13 to 15 hours. If the plant does not receive its daily minimum, then it does not bloom. The nature of the lighting (natural or artificial) does not matter. Illumination should not be excessive. Example: gloxinia, saintpaulia, calceolaria, coleus, cineraria, primrose, bellflower, balsam, epiphyllum, pelargonium, stephanotis.
Plants with a short day ovary and flowers appear only if within a few weeks (usually 8-10) they receive a strictly defined amount of light. Usually they need 12, 13 or 14 hours. Although in winter the amount of light is small, nevertheless it is quite enough for short-day plants. Example: zygocactus, tradescantia, kalanchoe, azaleas, large-flowered begonias, poinsettia.
The effects of light exposure (phototropism) can be observed in almost any plant - it reaches for the light. But we should not think that if we constantly rearrange the plant closer to the light, then we are doing it a favor. If stronger plants with decorative leaves positively react to light, then for flowering plants that are more sensitive to light, the consequences of the rearrangement can be detrimental. Azalea, camellia, "Decembrist", gardenia are known for the fact that when changing the angle of incidence of light, buds and sometimes leaves are immediately shed. Therefore, the pots of these sensitive plants must be "light-marked" as with a felt-tip pen or marker (or just stick a strip) a strip is placed on the side of the pot facing the light. It helps with the temporary taking of plants from the windowsill, then put it exactly as it stood.
As a rule, in the vast majority of cases, flowers are on the window. But windows are different.
If your window looks out north, northeast or northwest, then near it you can put a plant that does not particularly need light. West side considered very warm. Suitable for light sensitive plants southwestern side, in other cases, the plant must be darkened. With no blinds South side dangerous even for cacti. Very dry air and rapid evaporation of moisture plants can withstand only in winter period. This side without shading is the least suitable for indoor plants. East side favorable no less western, but on the northeast side, only shade-loving plants can grow well.
When placing plants a little further from the window or in the room, it should be borne in mind that the amount of light entering the room decreases sharply with distance from the window. Even a simple curtain "eats" more light than we think. Even the dust accumulating on the leaves prevents the access of light, so the plants need to be washed regularly, and the pubescent leaves should be cleaned with a soft brush. By the way, the cleanliness of windows also plays an important role - clean windows increase illumination by 10%. close to window glass the illumination is about 80% of the illumination outside the window, at a distance of only 1 m it drops to 50, at 3 m from the window it is only 3-5%. The amount of light plant needs for its normal development (growth, flowering, fruiting), is determined by the illumination, measured in lux, and the duration of illumination (length of the day). A light meter is used to measure illumination. On cloudy autumn days, the illumination on outdoors is approximately 1000 lux. Some shade-tolerant plants (aspidistra, rhombic cissus, asparagus, aloe, bilbergia, chlorophytum) are satisfied with this in winter time. The winter minimum light is 500 lux. Experts unanimously believe that shade-loving plants need at least 1000 lux, and for light-loving and flowering plants this figure increases to 5000 lux (for example, aphelandra, sanchetia, whiteperone, abutilon, bluebell, ceropegia, cacti). Flowering plants and many variegated species need more light, so when placing plants indoors, their need for light should be taken into account first of all. However, it should be remembered that in the spring and summer, many plants on the southern windows suffer from overheating by the sun's rays through the glass. Under the influence of direct sunlight, their leaves brighten and burn out, there may be burns - brown marks or thin and papery areas - this is a common problem for plants located on too sunny place if they are not adapted to such conditions. Most often, such problems arise if you leave drops of water on the leaves illuminated by the bright sun (water acts as a magnifying glass) or if you hold the plant near patterned glasses that collect rays. Therefore, in summer, most of the plants located on the southern windows need light shading with paper or a transparent curtain.
Spring and summer are the most favorable for plants. At this time, with an abundance of light, a long day in plants, a rapid accumulation of organic substances occurs, shoots, leaves, and the root system develop more rapidly. Many plants bloom at this time, while others form flower buds for autumn-winter flowering. In spring and summer days, the amount of organic substances formed in the plant during photosynthesis significantly exceeds their consumption for respiration. With a decrease in the level of photosynthesis in the short autumn-winter days, organic matter is barely enough for breathing, growth stops. In the most dark days at an extremely low level of photosynthesis, plants are forced to expend on respiration the reserves of organic substances accumulated in leaves and roots.
Among indoor plants there is a large group of shade-tolerant species that can exist for quite a long time in low light conditions (below 500 lux) without losing their decorative qualities. These include many aroid (aglaonema, dieffenbachia, monstera, syngonium), ivy, dracaena, fatsia, ficus, sansevieria. AT dark rooms Plants with a well-developed root system should be used. Large, strong specimens are much more stable in conditions of lack of light, since with a low level of photosynthesis they can use reserves for some time. nutrients accumulated in the roots.
Artificial lighting (lighting)
To create more favorable conditions for keeping plants in poorly lit places in winter, it is recommended to use artificial lighting. Under conditions of short daylight hours from November to the end of February, plants are illuminated additionally for 10-12 hours. In this case, the illumination should be at least 500-800 lux. In rooms without daylight, artificial lighting should be 1000 lux for shade-tolerant plants and at least 5000 lux for flowering plants and cacti. The duration of illumination is set depending on the species of the plant. For artificial lighting, it is recommended to use fluorescent lamps - they are more economical and emit less heat. Moreover, now they produce special "flower" lamps from Philips, Osram, Hagen. They need to be placed based on power - for example, if lamps with a power of 40 W are taken, then at least 6 pieces must be placed per 1 sq.m. You need to hang the lamps at a height of 25-30 cm for ornamental flowering and 30-60 for ornamental plants.
examples of adaptability of shade-tolerant plants light-loving plants and frost-resistant organisms
Features of light-loving and shade-tolerant plants Light-loving plants - heliophytes, plants growing in open places and not enduring long-term shading; For normal growth, they need intense solar or artificial radiation. Adult heliophytes, as a rule, are more photophilous than young specimens. Light-loving plants include both herbaceous (large plantain, water lily, etc.) and woody (larch, acacia, etc.) plants, early spring - steppes and semi-deserts, and from cultivated - corn, sorghum, sugar cane, etc. Woody or shrub heliophytes usually form sparse plantings. Leaves are equilateral, narrow, shiny; shoots are short; there are hairs. Adaptation to intense illumination is provided by the peculiarities of the morphology and physiology of photophilous plants. They usually have rather thick leaves with small-celled columnar and spongy parenchyma and a large number of stomata, often located at a large angle to the light (sometimes almost vertically); the leaf is shiny (due to the developed cuticle) or with pubescence. In light-loving plants, the skin does not contain chlorophyll, and the stomata are located on the lower surface of the leaf. Pelargonium (geranium), violet and a number of other plants have hairs that scatter, bright direct light, thereby protecting the leaves from overheating. In the cells of light leaves there are many small chloroplasts located along the walls - this explains the color of the leaves. In light-loving plants, lignification of shoots with the formation of thorns and spines is much more common (compared to shade-loving ones). A large number of stomata are characteristic, which are concentrated mainly on the underside of the leaf; multilayered palisade parenchyma is made up of small cells. Compared with shade-loving plants, heliophytes have a significantly higher content of chloroplasts in leaf cells - from 50 to 300 per cell; the total surface of leaf chloroplasts is tens of times greater than its area. Due to this, a high intensity of photosynthesis is ensured - a distinctive feature of heliophytes. Another morphological difference from shade-loving plants is a higher chlorophyll content per unit area and less per unit leaf mass. Light-loving plants (heliophytes) often have shoots with short internodes, strongly branching, often rosette. The leaves of heliophytes are usually small or with a dissected leaf blade, with a thick outer wall of epidermal cells, often with a wax coating or dense pubescence, with a large number of stomata per unit area, often submerged, with a dense network of veins, with well-developed mechanical tissues. In a number of plants, the leaves are photometric, that is, they are turned with an edge towards the midday rays or can change the position of their parts depending on the height of the Sun. So, in the steppe plant Sophora, the leaves of an unpaired pinnate leaf on a hot day are raised up and folded, in the Russian cornflower, segments of a pinnate leaf behave in the same way.
1. Fitness - the correspondence of the structure of cells, tissues, organs, organ systems to the functions performed, signs of the organism to the environment. Examples: the presence of cristae in mitochondria - an adaptation to the location on them of a large number of enzymes involved in the oxidation of organic substances; the elongated shape of the vessels, their strong walls - adaptability to the movement of water along them with minerals dissolved in it in the plant. The green color of grasshoppers, praying mantises, many caterpillars of butterflies, aphids, herbivorous bugs is an adaptation to protection from being eaten by birds. 2. Causes of fitness - the driving forces of evolution: hereditary variability, the struggle for existence, natural selection. 3. The emergence of adaptations and its scientific explanation. An example of the formation of fitness in organisms: insects did not previously have a green color, but were forced to switch to feeding on plant leaves. Populations are heterogeneous in color. Birds ate highly visible individuals, individuals with mutations (the appearance of green tints in them) were less visible on a green leaf. When they reproduced, new mutations arose in them, but they mostly remained natural selection individuals with green tones. After many generations, all individuals of this population of insects acquired a green color. 4. The relative nature of fitness. Signs of organisms correspond only to certain environmental conditions. When conditions change, they become useless and sometimes harmful. Examples: fish breathe with gills, through which oxygen enters the blood from the water. On land, fish cannot breathe because oxygen from the air does not enter the gills. The green color of insects saves them from birds only when they are on the green parts of the plant, on a different background they become visible and not protected. 5. The tiered arrangement of plants in a biogeocenosis is an example of their adaptability to the use of light energy. Placement in the first tier of the most light-loving plants, and in the lowest - shade-tolerant (fern, hoof, oxalis). The dense closing of crowns in forest communities is the reason for the small number of tiers in them.
Cellular structure of the leaf
The leaf, like all plant organs, has a cellular structure and consists of various types of tissues. Its structure is due to the unique ability to produce organic substances in the light.
The structure of the skin and pulp of the leaf
Outside, the leaf has a skin covering tissue. A piece of skin can be easily removed by hooking it with a needle and examined in the light. It is transparent, thanks to which light penetrates the flesh of the leaf. The skin is made up of two types of cells. Most of the cells are colorless, tightly adjacent to each other, others are green and form stomata. At aquatic plants stomata are located on the upper skin, in terrestrial ones - on the lower one.
The pulp cells of the leaf, located under the upper skin, look like columns and contain many chloroplasts. This is a columnar fabric. Under it are the cells irregular shape with fewer chloroplasts. This is spongy tissue. Between the cells are large intercellular spaces filled with air.
Columnar and spongy tissues are types of photosynthetic tissue.
The structure of leaf veins
All plant organs have conductive tissues.
shade tolerant plants
In leaves, they form vascular bundles of veins. Organic substances move through the sieve tubes of the veins from the leaves, water and mineral salts enter the leaves through the vessels. The composition of the conductive bundles includes fibers. They give strength to the veins.
Leaf venation types
The passage of veins in a leaf is called venation.
There are several types of venation:
- parallel - large veins run parallel to each other (wheat, cattail);
- reticulated - a powerful main vein passes in the middle of the leaf blade, and thinner lateral ones depart from it; mutual arrangement the vein resembles a bird feather (lilac, nettle);
- arcuate - each vein, except for the central one, is curved in an arc (lily of the valley, plantain);
- forked - the veins are located along the leaf, one vein branches into two, and they do not intersect (ferns, ginkgo and other ancient plants).
Light and shadow leaves
In plants that live in good light conditions, the leaves contain several layers of columnar cells. Spongy tissue is also well developed in them. Such leaves are called light. In shade-tolerant plants, the leaves have but one layer of small columnar cells, and their spongy tissue is less developed. Such leaves are called shadow. Thus, the leaf blades of the light leaves are thicker than those of the shadow leaves, however, in the shadow leaves, the chloroplasts are larger and contain more chlorophyll. That is why they are dark green in color. Light leaves are light green, as they contain less chlorophyll. Light and shadow leaves differ in size. In forests, plants have large leaves that capture more light.
light-loving plants- heliophytes, plants growing in open places and not enduring long-term shading; For normal growth, they need intense solar or artificial radiation. Adult heliophytes, as a rule, are more photophilous than young specimens.
Light-loving plants include both herbaceous (large plantain, water lily, etc.) and woody (larch, acacia, etc.) plants, early spring - steppes and semi-deserts, and from cultivated - corn, sorghum, sugar cane, etc. Woody or shrub heliophytes usually form sparse plantings.
Leaves - equilateral, narrow shiny; shoots are short; there are hairs.
Adaptation to intense illumination is provided by the peculiarities of the morphology and physiology of photophilous plants. They usually have rather thick leaves with small-celled columnar and spongy parenchyma and a large number of stomata, often located at a large angle to the light (sometimes almost vertically); the leaf is shiny (due to the developed cuticle) or with pubescence.
In photophilous plants, the skin does not contain chlorophyll, and the stomata are located on the lower surface of the leaf. Pelargonium (geranium), violet and a number of other plants have hairs that scatter, bright direct light, thereby protecting the leaves from overheating. In the cells of light leaves, there are many small chloroplasts located along the walls - this explains the color of the leaves.
In light-loving plants, lignification of shoots with the formation of thorns and spines is much more common (compared to shade-loving ones). A large number of stomata are characteristic, which are concentrated mainly on the underside of the leaf; multilayered palisade parenchyma is made up of small cells. Compared with shade-loving plants, heliophytes have a significantly higher content of chloroplasts in leaf cells - from 50 to 300 per cell; the total surface of leaf chloroplasts is tens of times greater than its area. Due to this, a high intensity of photosynthesis is ensured - a distinctive feature of heliophytes. Another morphological difference from shade-loving plants is the higher content of chlorophyll per unit area and the lower content per unit leaf mass.
Light-loving plants (heliophytes) often have shoots with short internodes, strongly branching, often rosette. The leaves of heliophytes are usually small or with a dissected leaf blade, with a thick outer wall of epidermal cells, often with a wax coating or dense pubescence, with a large number of stomata per unit area, often submerged, with a dense network of veins, with well-developed mechanical tissues. In a number of plants, the leaves are photometric, that is, they are turned with an edge towards the midday rays or can change the position of their parts depending on the height of the Sun. So, in the steppe plant Sophora, the leaves of an unpaired pinnate leaf on a hot day are raised up and folded, in the Russian cornflower, segments of a pinnate leaf behave in the same way.
The optical apparatus of heliophytes is better developed than that of sciophytes, has a large photoactive surface and is adapted to a more complete absorption of light. Usually their leaves are thicker, the cells of the epidermis and mesophyll are smaller, the palisade parenchyma is two-layered or multi-layered (in some savannah plants of West Africa - up to 10 layers), often developed under the upper and lower epidermis. Small chloroplasts with a well-developed granal structure in large numbers (up to 200 or more) are located along the longitudinal walls.
There is less chlorophyll per dry weight in the leaves of heliophytes, but they contain more pigments of the I pigment system and chlorophyll P700. The ratio of chlorophyll a to chlorophyll b is approximately 5:1. Hence the high photosynthetic capacity of heliophytes. The compensation point lies in the region of higher illumination. The intensity of photosynthesis reaches its maximum in full sunlight. In a special group of plants - heliophytes, in which CO2 is fixed by C4-dicarboxylic acids, light saturation of photosynthesis is not achieved even under the strongest illumination. These are plants from arid regions (deserts, savannahs).
Answers to controversial test items
There are especially many C4 plants among the families of bluegrass, sedge, aizaceae, purslane, amaranth, haze, clove, and euphorbia. They are capable of secondary fixation and reutilization of CO2 released during light respiration, and can photosynthesize when high temperatures and with closed stomata, which is often observed during the hot hours of the day.
shade tolerant plants- plants (woody, many herbaceous under the canopy of hardwoods, greenhouses, etc.), which tolerate some shading, but develop well in direct sunlight.
With age, as well as in high latitudes, mountains, in a drier climate, shade tolerance decreases. A number of plants under the forest canopy (for example, wild hoof, gout, etc.) in early spring, before the leaves of the tree layer open, are physiologically photophilous, and in summer, when the canopy is closed, they are shade-tolerant. Physiologically, shade-tolerant plants are characterized by a relatively low intensity of photosynthesis.
Shade-tolerant plants (sciophytes) - are constantly in conditions of strong shading. At illumination of 0.1–0.2%, only mosses and selaginella can grow. Club mosses are content with 0.25-0.5% of total daylight, and flowering plants are usually found where the illumination on cloudy days reaches at least 0.5-1% (begonias, touchy, herbs from the ginger, madder, commelin families).
The leaves of shade-tolerant plants have a number of anatomical and morphological features: the columnar and spongy parenchyma are poorly differentiated, enlarged intercellular spaces are characteristic - the cells contain a small number (10-40) of chloroplasts, the surface area of which varies within 2-6 cm2 per 1 cm2 of leaf area. The epidermis is rather thin, single-layered, the cells of the epidermis may contain chloroplasts (which is never found in heliophytes). The cuticle is usually thin. Stomata are usually located on both sides of the leaf with an insignificant predominance on the reverse side (in photophilous plants, as a rule, stomata are absent on the front side or are located mainly on the reverse side). Compared with heliophytes, shade-tolerant plants have a significantly lower content of chloroplasts in leaf cells - on average, from 10 to 40 per cell; the total surface of leaf chloroplasts slightly exceeds its area (2-6 times; while in heliophytes, the excess is tens of times). Some shade-tolerant plants are characterized by the formation of anthocyanin in the cells when growing in bright sun, which gives a reddish or brownish color to the leaves and stems, which is uncharacteristic in the natural habitat conditions. In others, when growing in direct sunlight, a paler color of the leaves is noted. The leaves of shade-tolerant plants are thin, the cells and chloroplasts in them are large.
In the northern broad-leaved and dark coniferous forests, the canopy of a dense forest stand can transmit only 1–2% of PAR, changing its spectral composition. Blue and red rays are absorbed most strongly, and relatively more yellow-green, far red and infrared rays are transmitted. Poor illumination is combined with high air humidity and high CO2 content, especially near the soil surface. The sciophytes of these forests are green mosses, club mosses, common sorrel, wintergreens, two-leaved mullet, etc.
Sciophytes have less chlorophyll P700 than heliophytes. The ratio of chlorophyll a to chlorophyll b is approximately 3: 2. With less intensity, they have such physiological processes as transpiration and respiration. The intensity of photosynthesis, having quickly reached a maximum, ceases to increase with increasing illumination, and in very bright light it can even decrease.
In deciduous shade-tolerant tree species and shrubs (pedunculate oak, heart-shaped linden, common lilac, etc.), the leaves located along the periphery of the crown have a structure similar to the structure of heliophyte leaves and are called light, and in the depths of the crown - shadow leaves with a shadow structure similar to the structure of sciophyte leaves.
The appearance of shade-tolerant plants also differs from light-loving ones. Shade-tolerant plants usually have wider, thinner, softer leaves to capture more diffused sunlight. In shape, they are usually flat and smooth (whereas heliophytes often have folded, tubercular leaves). The horizontal arrangement of foliage is characteristic (in heliophytes, leaves are often located at an angle to the light) and leaf mosaic. Forest grasses are usually elongated, tall, have an elongated stem.
Many shade-tolerant plants have a high plasticity of their anatomical structure, depending on the illumination (first of all, this concerns the structure of the leaves). For example, in beech, lilac, and oak, leaves formed in the shade usually have significant anatomical differences from leaves grown in bright sunlight. The latter in their structure resemble the leaves of heliophytes (such leaves are defined as "light", as opposed to "shadow").
Changes in the attitude of plants to light
If the light regime regularly changes periodically in the same habitat, plants in different seasons can manifest themselves either as light-loving or shade-tolerant.
In spring, in oak forests, 50–60% of solar radiation penetrates under the forest canopy. The leaves of the rosette shoots of common goutweed have a light structure and are characterized by a high intensity of photosynthesis. At this time, they create the bulk of the organic matter of annual production. The leaves of summer goutweed, appearing with a developed tree canopy, under which an average of 3.5% of solar radiation penetrates, have a typical shadow structure, and their photosynthesis intensity is much lower, by 10–20 times. A similar duality in relation to light is also manifested by hairy sedge, light-loving in spring and shade-tolerant in summer. Apparently, this is also characteristic of other plants of oak broad grasses.
2551-2560
2551. What adaptation in shade-tolerant plants ensures more efficient and complete absorption of sunlight?
BUT) small leaves
B) large leaves
B) thorns and spines
D) wax coating on the leaves
2552. Why are algae in the pond ecosystem classified as producer organisms?
A) consume ready-made organic substances
B) decompose organic matter
B) create organic substances from inorganic substances
D) participate in the cycle of substances
Abstract
2553. Oxygen breakdown of glucose is much more efficient than fermentation, since in this case
A) the released energy is released in the form of heat
B) 2 ATP molecules are synthesized
B) energy is being used
D) 38 ATP molecules are synthesized
Abstract
2554. Crossed two diheterozygous pumpkin plants with yellow round fruits. Determine the ratio of phenotypes of hybrids of the first generation with complete dominance.
A) 1:1
B) 1:2:1
C) 3:1
D) 9:3:3:1
Abstract
2555. In cell engineering, research is carried out related to
A) transfer of nuclei from one cell to another
B) the introduction of human genes into bacterial cells
B) rearrangement of the organism's genotype
D) gene transfer from bacteria to cereal cells
Abstract
Test "Abiotic environmental factors"
Each division of plants is subdivided into
A) kingdoms
B) squads
B) classes
D) types
Abstract
2557. If a concentrated solution of table salt is added to a test tube with blood, the erythrocytes shrink due to
A) release of water from them
B) EPS damage
B) water intake
D) reduction in the number of ribosomes
2558. Organisms in an ecosystem change the environment, thereby creating conditions for
A) natural change of community
B) mass selection actions
B) the occurrence of mutations
D) seasonal changes
Abstract
Abstract
2560. Cytogenetic method allows to study in humans
A) development of signs in twins
B) features of the metabolism of his body
B) its chromosome set
D) family history
© D.V. Pozdnyakov, 2009-2018
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| mosaics are also found in the grass cover of heavily shaded forests. Some shade plants capable of protective movements: changing the position of leaf blades when strong light hits them. AT spruce forest with a sparse canopy, one can often see that Oxalis acetosella in bright sunlight, the leaves fold so that their lobes acquire a vertical position. It is interesting that the areas of grass cover with folded sorrel leaves quite accurately coincide with the location of large sun glare. A number of adaptive features can be noted in the structure of the leaf as the main receiver of solar radiation. In many heliophytes, the leaf surface has features that contribute to the reflection of rays (shiny, as if varnished, for example, in magnolia laurel; covered with light wax | |
| - in bloom - in cacti, milkweeds, crassula) or weakening their action (dense_ pubescence, thick cuticle). Sometimes crystalline inclusions are found in the cells of the epidermis, which play the role of a “screen” for light rays (in some plants on chalk outcrops, in linden with excess lighting, |  |
| nia, etc.). |
Plant adaptations to light conditions
In plants of shady habitats, such protective features of the integumentary tissues of the leaf, as a rule, are absent. The internal structure of the leaf in heliophyte plants differs in a number of features of the "light structure" of assimilation tissues (Fig. 29). This is primarily a well-developed palisade tissue, often consisting of narrow and long cells (sometimes of 2-3 rows). In many heliophytes, the palisade tissue is well developed not only on the upper, but also on the underside of the leaf (“isopalisade” leaf). The formation of a powerful palisade tissue in the ontogeny of "light" leaves is associated with the fact that under conditions of strong illumination, palisade cells continue to grow in length for a long time, and in shading, growth in this direction stops early.
Plants have various morphological and physiological adaptations to the light regime of habitats.
According to the requirement for lighting conditions, it is customary to divide plants into the following ecological groups:
- light-loving (light), or heliophytes, - plants of open, constantly well-lit habitats;
- shade-loving (shady), or sciophytes, - plants of the lower tiers of shady forests, caves and deep-sea plants; they do not tolerate strong lighting in direct sunlight;
- shade-tolerant, or facultative heliophytes - can tolerate more or less shading, but grow well in the light; they are easier than other plants to rebuild under the influence of changing lighting conditions.
Light-loving, or heliophytes, can develop normally only with sufficiently bright light, they do not tolerate or tolerate even slight shading very badly. Therefore, they live in open places and are rarely found in the forest zone. They usually grow sparsely so as not to obscure each other. Many meadow grasses, plants of the steppes and deserts, tundra and high mountains, tall trees, most of them are photophilous. cultivated plants open ground, many weeds. Adaptation to light has formed a very character traits these plants. They usually have a highly branched root system, well-developed axial organs, relatively short internodes (since strong light inhibits growth): rather small, thick, hard, sometimes fleshy leaves with a thick outer wall of epidermal cells and with a thick cuticle, often with a waxy coating or pubescence; relatively low chlorophyll content compared to other plants (chlorophyll a predominates), a dense network of veins, good development of mechanical tissues or water-storing parenchyma; a large number of stomata (often very small, lying in pits or covered with hairs); arrangement of leaves at an angle (or edge) to the rays of the sun; vigorous respiration with a high waste of synthesized organic matter; high osmotic potential of cell sap.
Shade-loving plants, or sciophytes, grow only in shaded places and are never found in strong light conditions. Shade-loving species include species located in the lower tiers of plant communities, especially in the attached layer of dark coniferous and deciduous forests, tropical moist forests, in caves and at great depths. This is Asarum europaeum and raven eye Paris quadriifolia growing in oak forests, small periwinkle Vinca minor, celandine Chelidonium majus.
In the process of evolution, this group of plants adapted to low light conditions. Their characteristic anatomical, morphological and physiological features are in most cases opposite to those of photophilous plants. They are distinguished by poor development of mechanical and conductive tissues; have large, wide, thin and soft leaf blades, located perpendicular to the incident light and forming a mosaic to better capture it; their leaves are dark green, large quantity green pigments (they contain significantly more chlorophyll b than light-loving ones); the leaf epidermis is single-layered, large-celled, often containing a chloroplast with or without a thin cuticle; the number of stomata is small (they are 10-15 times more in photophiles) and they are large and shallow; the concentration of cell sap is lower than that of heliophytes, so the osmotic potential is low; physiological processes - transpiration, respiration - proceed less intensively. In conditions of high insolation, they cannot effectively regulate transpiration and usually dry out in open areas.
Features of light-loving and shade-tolerant plants
A clear expression of light and shade love. e. stenobiontness, characteristic of species narrowly adapted to light.
Facultative heliophytes, or shade-tolerant plants, depending on the degree of shade tolerance, have adaptive features that bring them closer either to heliophytes or to sciophytes. This group includes some meadow plants, forest grasses and shrubs that grow both in shaded areas of the forest and in forest clearings, edges, clearings. In brightened places, they often grow stronger, however, the optimal use of PAR in them does not occur in full sunlight.
In trees and shrubs, the shadow or light structure of the leaf is often determined by the lighting conditions of the previous year when the buds are set: if the buds are set in the light, then the light structure is formed, and vice versa.
The attitude to the light regime changes in plants and in ontogeny. Seedlings and juvenile plants of many meadow species and tree species are more shade tolerant than adults.
Sometimes the requirements for the light regime change in plants when they find themselves in different climatic and edaphic conditions. Thus, the usual shade-tolerant plants of the coniferous forest - blueberries, European week-grass and some others - in the tundra acquire the characteristics of heliophytes.
The most common adaptation of plants to the maximum use of PAR is the spatial orientation of leaves. When the leaves are vertical, as, for example, in many cereals and sedges, sunlight is more fully absorbed in the morning and evening hours - at a lower standing of the sun. With the horizontal orientation of the leaves, the rays of the midday sun are more fully used. With a diffuse arrangement of leaves in different planes solar radiation during the day is utilized most fully. Usually, the leaves of the lower tier on the shoot are deflected horizontally, the middle ones are directed obliquely upwards, and the upper ones are almost vertical.
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