According to the requirements for lighting conditions, it is customary to divide plants into the following ecological groups: 1) photophilous(light), orheliophytes,– plants of open, constantly well-lit habitats; 2) shade-loving(shadow), orsciophytes, – plants of the lower tiers of shady forests, caves and deep-sea plants; they do not tolerate strong light from direct sunlight; 3) shade-tolerant,orfacultative heliophytes,– can tolerate more or less shade, but grow well in light; They adapt more easily than other plants under the influence of changing lighting conditions.

Light adaptations of heliophytes and sciophytes. Heliophytes often have shoots with shortened internodes, highly branched, often rosette-shaped. The leaves of heliophytes are usually small or with a dissected leaf blade, with a thick outer wall of epidermal cells, often with a waxy coating or dense pubescence, with a large number stomata per unit area, often submerged, with a dense network of veins, with well-developed mechanical tissues. A number of plants have photometric leaves, that is, they are turned with their edges towards the midday rays or can change the position of their parts depending on the height of the Sun. The optical apparatus of heliophytes is better developed than that of sciophytes, has a larger photoactive surface and is adapted to more complete absorption of light. They usually have thicker leaves, smaller epidermal and mesophyll cells, and two-layer or multilayer palisade parenchyma (in some savannah plants 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 P 700. 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 area of ​​higher illumination. The rate of photosynthesis reaches its maximum at full sunlight. In a special group of plants - heliophytes, in which CO 2 fixation occurs through C4-dicarboxylic acids, light saturation of photosynthesis is not achieved even under the strongest illumination. These are plants from arid regions (deserts, savannas). There are especially many C4 plants among the families of Poa, Sedge, Aizaceae, Purslanaceae, Amaranthaceae, Chenopodiaceae, Cloveaceae, and Euphorbiaceae. They are capable of secondary fixation and recycling of CO 2 released during light respiration, and can photosynthesize at high temperatures and with closed stomata, which is often observed during hot hours of the day. Typically, C4 plants, especially sugarcane and corn, are highly productive.

Sciophytes- these are plants that are constantly in conditions of heavy shading. At 0.1–0.2% illumination, only mosses and selyaginella can grow. Mosses are content with 0.25-0.5% of total daylight, and flowering plants are usually found where illumination on cloudy days reaches at least 0.5-1% (begonias, impatiens, herbs from the ginger, madder, and commelinaceae families). In northern broad-leaved and dark-coniferous forests, the canopy of a closed tree 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 rays, far red and infrared rays are transmitted. Low illumination is combined with high air humidity and high CO 2 content, especially near the soil surface. The sciophytes of these forests are green mosses, mosses, wood sorrel, wintergreens, bifolia, etc. The leaves of sciophytes are arranged horizontally, often with a well-defined leaf mosaic. The leaves are dark green, larger and thinner. Epidermal cells are larger, but have thinner outer walls and a thin cuticle, and often contain chloroplasts. Mesophyll cells are larger, the palisade parenchyma is single-layered or has an atypical structure and consists not of cylindrical, but of trapezoidal cells. The area of ​​the veins is half that of heliophyte leaves, and the number of stomata per unit area is less. Chloroplasts are large, but their number in cells is small. Sciophytes have less chlorophyll P 700 compared to heliophytes. The ratio of chlorophyll a to chlorophyll b is approximately 3: 2. Such reactions occur with less intensity. physiological processes like transpiration, respiration. The intensity of photosynthesis, having quickly reached a maximum, ceases to increase with increasing illumination, and in very bright light it may even decrease. In deciduous shade-tolerant tree species and shrubs (pedunculate oak, cordate 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 leaves, and in the depths of the crown - shadow leaves with a shadow structure , similar to the structure of sciophyte leaves. facultative heliophytes,orshade-tolerant plants, depending on the degree of shade tolerance, have adaptive features that bring them closer to heliophytes and sciophytes. This group includes some meadow plants, forest grasses and shrubs that grow in shaded areas of the forest, and in forest clearings, edges, and clearings. In bright areas they often grow stronger, but their optimal use of PAR 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 laid: if the buds are laid in the light, then the light structure is formed, and vice versa. If in the same habitat the light regime regularly changes periodically, plants in different seasons can manifest themselves either as light-loving or shade-tolerant. In spring, in oak forests, 50–60% penetrates under the forest canopy. solar radiation. Leaves of rosette shoots common dream 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 the annual production. The leaves of the summer generation, which appear when the tree canopy is developed, under which an average of 3.5% of solar radiation penetrates, have a typical shadow structure, and their intensity of photosynthesis is much lower, 10–20 times. A similar duality in relation to light is shown by hairy sedge , light-loving in spring and shade-tolerant in summer. Apparently, this is also characteristic of other oak forest broadgrass plants. The attitude towards the light regime changes in plants and during ontogenesis. Seedlings and juvenile plants of many meadow species and tree species are more shade-tolerant than adult plants.

Light as a condition for animal orientation Sunlight for animals Not is like this necessary factor, as for green plants, since all heterotrophs ultimately exist due to the energy accumulated by plants. Nevertheless, the light part of the solar radiation spectrum plays an important role in the life of animals. Different species of animals require light of a certain spectral composition, intensity and duration of illumination. Deviations from the norm suppress their vital functions and lead to death. There are light-loving species ( photophiles) and shade-loving ( photophobes); euryphotic, withstanding a wide range of illumination, and stenophotic, tolerating narrowly limited lighting conditions.

Light for animals is a necessary condition for vision and visual orientation in space. Scattered rays reflected from surrounding objects, perceived by the visual organs of animals, provide them with a significant part of information about the outside world. The development of vision in animals went in parallel with the development of the nervous system. The completeness of visual perception of the environment in animals depends primarily on the degree of evolutionary development. The primitive eyes of many invertebrates are simply light-sensitive cells surrounded by pigment, and in unicellular organisms there is a light-sensitive region of the cytoplasm. The process of light perception begins with photochemical changes in the molecules of visual pigments, after which an electrical impulse occurs. The organs of vision from individual eyes do not produce images of objects, but perceive only fluctuations in illumination, alternation of light and shadow, indicating changes in the environment. Figurative vision is possible only with a sufficiently complex structure of the eye. Spiders, for example, can distinguish the contours of moving objects at a distance of 1–2 cm. The most advanced organs of vision are the eyes of vertebrates, cephalopods and insects. They allow you to perceive the shape and size of objects, their color, and determine distance. The ability for three-dimensional vision depends on the angle of the eyes and the degree of overlap of their fields of vision. Three-dimensional vision, for example, is characteristic of humans, primates, and a number of birds - owls, falcons, eagles, and vultures. Animals with eyes located on the sides of their heads have monocular, plane vision.

The maximum sensitivity of a highly developed eye is enormous. A person accustomed to the dark can distinguish light, the intensity of which is determined by the energy of only five quanta, which is close to the physically possible limit.

The concept of visible light is somewhat arbitrary, since individual animal species vary greatly in their ability to perceive different rays of the solar spectrum. For person region visible rays – from purple to dark red.

Some animals, for example rattlesnakes see the infrared part of the spectrum and catch prey in the dark, orienting themselves using their visual organs. For bees the visible part of the spectrum is shifted more shortwave region. They perceive a significant portion of ultraviolet rays as colors, but do not distinguish red ones. The ability to distinguish color largely depends on the spectral composition of the radiation at which the species exists or is active. Most mammals, descended from ancestors with twilight and nocturnal activity, do not distinguish colors well and see everything in black and white (dogs, cats, hamsters, etc.). The same vision is characteristic of nocturnal birds (owls, nightjars). Diurnal birds have well-developed color vision. Living in dim lighting often leads to eye hypertrophy. Huge eyes, capable of capturing tiny fractions of light, are characteristic of nocturnal lemurs, loris monkeys, tarsiers, owls, etc. Animals navigate using vision during long flights and migrations. Birds choose their flight direction with amazing accuracy, sometimes covering thousands of kilometers from nesting sites to wintering grounds. It has been proven that during such long flights birds are at least partially oriented by the sun and stars, i.e. astronomical light sources. When forced to deviate from the course, they are capable of navigation, i.e., changing orientation in order to get to the desired point on the Earth. In partly cloudy conditions, the orientation is maintained as long as at least part of the sky is visible. Birds do not fly into continuous fog or, if it catches them on the way, they continue to fly blindly and often lose their course. Birds' navigational ability is innate. It is not acquired through life experience, but is created by natural selection as a system of instincts. The exact mechanisms of this orientation are still poorly understood. The hypothesis of the orientation of birds in migration by astronomical light sources is currently supported by experimental and observational materials. The ability for this kind of orientation is also characteristic of other groups of animals. Among insects, it is especially developed in bees. Bees that have found nectar transmit information to others about where to fly for a bribe, using the position of the sun as a guide.

Usually only two opposite groups of plants are considered - light-loving and shade-tolerant; the latter are sometimes called sciophytes, thereby using the term in a slightly different, broader meaning. In any case, the boundaries of groups are arbitrary; there is enough a large number of species that, based on various characteristics or at different phases of development, could be classified as one or another group.

The term is also widely used in plant growing shade tolerance- it means the ability of cultivated plants to tolerate reduced illumination in general, or in comparison with illumination in natural habitat conditions. Shade tolerance is a relative term, its correct understanding depends largely on the context. When comparing different woody plants, “shade tolerance” will have one semantic content, but when comparing shade-tolerant trees with shade-tolerant shrubs or herbaceous plants, “shade tolerance” can mean completely different levels illumination Shade tolerance is a rather complex, multifaceted property of plants, depending on many factors, including how much various types adaptation to shading is developed. Plants of the same species grown in different conditions, can show varying degrees of shade tolerance: it is influenced by soil fertility, water availability and other abiotic factors.

Basic provisions

All but a few species require sunlight to survive. However, in quantitative terms, high light intensity does not always contribute to the normal development of plants. With a lack of water in the soil and moisture in the atmosphere, it is easier for plants to exist in shaded habitats than in open sun.

Plants absorb light energy mainly from the violet-blue and partly red zones of the spectral range of visible light. Light radiation in the red range is mostly absorbed by light-loving plants that form the upper tiers of forests, but radiation close to infrared penetrates through the foliage to the plants that form the lower tiers. The shade-tolerant plants living here are capable of absorbing light from the extreme red zone of the spectrum (with a wavelength of 730 nm).

However, less light means less energy is available to plants. Just as in sunny, dry environments the limiting factor in plant growth and survival is a lack of moisture, in shady habitats the limiting factor is usually a lack of solar energy.

Plant uptake nutrients often differs between those living in the shade and in a sunny place. Shading usually comes from trees that form the upper layers of forests. This causes differences in soils, which in forests are regularly enriched with nutrients due to the decomposition products of discarded leaves. Compared to forest soils, the soils of sunny habitats are the same climate zone usually poorer. Shade-tolerant plants compared to light-loving plants, they are better adapted for greater absorption of nutrients; and shade tolerance as such depends to some extent on soil fertility.

Features of the morphology and physiology of shade-tolerant plants

Shade-tolerant plants are characterized by a relatively low rate of photosynthesis. Their leaves differ from the leaves of heliophytes in a number of important anatomical and morphological characteristics. In the leaves of shade-tolerant plants, columnar and spongy parenchyma are usually poorly differentiated; characterized by increased intercellular spaces. The epidermis is quite thin, single-layered; epidermal cells 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 a slight predominance on back side(in light-loving plants, as a rule, front side stomata are absent or located predominantly on the reverse side). Compared to 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 the leaf chloroplasts does not significantly exceed its area (2-6 times; whereas in heliophytes the excess is tens of times).

Some shade-tolerant plants are characterized by the formation of anthocyanin in their cells when growing in bright sun, which gives a reddish or brownish color to the leaves and stems, which is uncharacteristic in natural conditions habitat. Others have paler leaves when grown in direct sunlight.

The appearance of shade-tolerant plants also differs from light-loving ones. Shade-tolerant plants typically have wider, thinner, softer leaves to capture more indirect sunlight. They are usually flat and smooth in shape (whereas in heliophytes, folding and tuberculation of leaves is often found). Characterized by a horizontal arrangement of foliage (in heliophytes, leaves are often located at an angle to the light) and leaf mosaic. Forest herbs are usually elongated, tall, and have an elongated stem.

Many shade-tolerant plants have high plasticity of their anatomical structure depending on the light level (primarily 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”).

Non-woody shade-tolerant plants

Although most plants grow towards the light (see phototropism), many shade-tolerant tropical vines (for example, Monstera attractive and many species of the genus Philodendron) initially, after germination, move away from the light. This helps them locate the tree trunk that serves as their support, and onto which they climb as they grow, reaching areas of brighter light.

Shade-tolerant trees

In forests where precipitation is sufficient and water is not a limiting factor for growth, shade tolerance is one of the determining factors characterizing various woody species. However different types trees show different adaptations to shading. For example, hemlock, one of the characteristic shade-tolerant plants native to North America, is able to germinate and fully develop under a completely closed forest canopy. Sugar maple is also classified as a characteristic shade-tolerant tree; it also germinates under a closed canopy and can develop well as an inhabitant of the understory, but unlike Canadian hemlock, it reaches full size and development only when open space is formed above it. Shade-intolerant trees - heliophytes, such as willow, aspen, birch - cannot develop as plants of the lower tier of the forest. They prefer open habitats with plenty of light: they often grow in wetlands, along rivers and lakes, or in former burned areas. Shade-tolerant trees of temperate climates, compared to light-loving trees, usually have greater resistance to low daytime temperatures during the growing season.

Shade-tolerant plants in crop production

Agricultural plants

Some shade-tolerant plants are valuable forage crops. The common vetch grown for these purposes is also used as green manure.

Ornamental plants for gardens and parks

Greenhouse and indoor plants

For more information on this topic, see: Shade Tolerant houseplants.

see also

Notes

Literature

• Lysikov A. Shadow society. Shade-tolerant plants // Gardener: magazine. - 2007, No. 8.

Links

• Flower garden in the shade. Master's recommendations. Lecture notes by Yu. B. Markovsky.

Wikimedia Foundation. 2010.

If you are, then shadows will definitely appear on it. Residential and outbuildings, trees and large shrubs will create areas with complete or partial absence of direct light. The most common light-loving plants will not be able to survive in such places, as a result of which the dacha may have a somewhat deserted appearance. This article will talk about those plant crops that will help you solve this problem.

Dahlias - perennial shade-loving flowers for the garden

General provisions

First of all, let's draw a dividing line between plant species according to their dependence on sunlight, in order to avoid possible confusion in the future:

Separation according to photophilousness

Advice: before purchasing, be sure to check with the seller which specific group the flora representative you are purchasing belongs to, since incorrect placement on your site will deprive it of the opportunity for full development.

Shadow Control

In addition to choosing plants with different needs for sunlight, you can also optimally plan the placement of shady areas. To do this, just adhere to the following rules:

Tip: if you need to identify dark places in an already planted garden, it is convenient to do this in the spring when the snow melts. Where it lasts the longest, you can safely plant shade-loving crops with your own hands.

Species and representatives

The crops in question have many variations:

Shrubs

There are several common summer cottages representatives of bush vegetation that thrive even with limited light:

1. Rhododendron. They can do without the sun at all, but then they won’t bloom, so it’s better to choose partial shade for them.

1. Hydrangea. Its delicate buds will decorate any dark area.

1. Kalina. Not only is it unpretentious, it is also useful.

1. Elderberry. It is also famous for its medicinal properties.

1. Ivy. The price of such a plant is minimal, but the possibilities with the right approach colossal.

1. Clematis. It also belongs to the climbing species and can become a decoration for any plant.

Flowers and ornamental vegetation

1. Perennials include the largest number of representatives of shade lovers.

Here are some of them:

• Badan. It is capable of developing normally in growth even in the complete absence of light; only its flowering can suffer.

• Hosta. Not only is he not afraid of the shadow, but he also adores it. The only important thing is that the soil is sufficiently moist.

• Aconite. Twilight and moisture are all it needs for full growth.

• Brunner. An unpretentious and fast-growing plant. Keep an eye on it so it doesn't grow too big.

1. Biennials:

• "Pansies" will delight you with their continuous flowering from spring to autumn.

• Digitalis. When growing it, it is very important that the agricultural technology instructions are strictly followed.

• Forget-me-not. Allows you to create an aesthetic carpet even in the darkest place.

Any plant that grows in an open area under abundant sun and does not experience, so to speak, discomfort, but, on the contrary, needs such conditions, is a heliophyte. an example of which will be discussed below, have their own distinctive features.

What is characteristic of heliophytes?

The leaves of light-loving plants have their own characteristics and are easy to notice. Namely:

• the thickness of the leaves of such plants is most often greater than that of others that are not so susceptible to light;
• the angle between the leaves and the direction of incidence of the sun's rays is large, reaching up to ninety degrees.

Also, light-loving plants (for example, birch, and in hotter latitudes, cactus) contain a huge number of chloroplasts in their leaves: there can be from fifty to three hundred of them per cell, due to which there is a high intensity of photosynthesis. This is the most characteristic physiological sign plants with high needs in the sun. With this characteristic of light-loving plants, let’s look at a few more questions.

What happens if you deprive a heliophyte of solar energy?

With low doses of lighting, the plant develops symptoms such as depression, and a delay in its development is also observed. And the older the plant, the higher its need for sun.

Where do heliophytes grow?

Listing the characteristics of light-loving plants should begin with parameters such as location and nature of growth. What exactly are we talking about? Heliophytes can grow both in conditions of intense solar radiation and in some shaded areas. Prolonged blackouts, as mentioned above, will have a detrimental effect on them. Heliophytes, which are classified as shrubs or trees, usually grow as sparse plantings in order to have access to the sun at any time of the day.

What types of light-loving plants are there?

An example of heliophytes can be cited from any type of plant, be it trees, bushes, grasses, or representatives of flora growing in water. Let's look at what heliophytes are found in our latitudes.

1. Trees. These include: birch, linden, mountain), ash, apple, juniper, oak (common, English), quince, aspen, etc.
2. Shrubs. These include lilac, rose, sour thorn, jasmine, some, etc.
3. Herbal and cereals. These are tomato, water lily, plantain, corn, lingonberry, heather, etc.

Those who like to grow flowers at home need to take into account data on the light sensitivity of the flower that will grow in a pot on the windowsill. Before purchasing a certain plant, it is worth knowing all its characteristics so that it can live in your apartment without any problems. Returning to the current topic, we can give several examples of light-loving indoor plants.

1. In many homes you can find a flower such as begonia. It is a light-loving plant, but it is still better not to place it under direct scorching rays from May to September.
2. Kalanchoe also loves light, but not direct rays, which can cause burns on the leaves.
3. Monsteras, sansevierias and dracaenas will do well under bright, diffused rays or in partial shade.
4. Phalaenopsis is a type of orchid that loves light, but not heat, so it is good to place them on an eastern window.
5. Fuchsias are not averse to bathing in the sun in the morning or in the afternoon.
6. Cyclamen also benefit from bright lighting, but it is advisable to place them under direct rays only in winter period. The same conditions need to be created for violets. As they shrink, you can move them slightly closer to the window from a distance of about 2-3 meters during the hottest period.

Adaptation of heliophytes to unfavorable conditions

Not always environment protects light-loving plants. An example of how a cherry tree disappears and does not bear fruit if it is in the shade will be familiar to many people who are at least a little involved in gardening. But first, the plant will do everything it can to get more light. This is mainly expressed in the increased surface area of ​​​​the sheets and a deeper green tint, because it is known that dark colors absorb more energy from the sun's rays. Also, for the same purpose, the stems of plants are stretched, but at the same time they become more fragile, and the trees grow taller or can change their shape in order to receive more light.

Depending on the degree of illumination that particular indoor plants like, they can be divided into four main groups: shade-loving indoor plants, shade-tolerant, light-loving and plants that are undemanding to the light regime.

“Love” or “dislike” for light is determined by the place where the houseplant’s ancestors grew in natural conditions. Briefly about each group we can say the following.

Shade-loving indoor plants

Under natural conditions, the ancestors of shade-loving houseplants grow in the lower layer of tropical rainforests and bright light They practically never get it.

Shade-loving indoor plants include asparagus (some species), aspidistra, helxina, clivia, tuberous begonia, some types of ferns, ophiopogon, ruscus, tradescantia, rhipsalis and others, less popular.

Shade-loving indoor plants do not tolerate bright light at all; it is not recommended to take them out of the room, even to a shaded place. The most favorable location for them is the northern and northwestern windows.

The advantage of cultivating shade-loving indoor plants is that they can be grown even away from the window and under artificial lighting.

Shade-tolerant indoor plants

Shade-tolerant indoor plants differ from shade-loving ones in that they can grow in both light and shaded areas. However, they require more intense lighting to bloom.

The group of shade-tolerant indoor plants includes begonia, bougainvillea, aloe, laurel, myrtle, ferns, philodendron, ficus, hoya, schefflera and others.

Shade-tolerant indoor flowers grow well on windows facing south, southeast and southwest. Direct sunlight in summer time are often destructive for such plants, therefore, for normal well-being during the period of intensive development, some of them must be removed to western and eastern windows.

Variegated types of shade-tolerant indoor plants require more intense lighting, especially on winter days. To ensure normal living conditions at this time, they can be illuminated with ordinary fluorescent lamps.

Light-loving indoor plants

Under natural conditions, the ancestors of light-loving indoor plants grow in open spaces. These are plants such as agave, abutilon, akalifa, gardenia, belopelone, geranium, hibiscus, irezine, cacti, camellia, bells, cordyline, poinsettia, oleander, setcreasia, date palm, citrus fruits and others.

It is recommended to place light-loving indoor plants on southern or southeastern, as well as southwestern windows. However, care should be taken to ensure that they do not get sunburn in the form of brown spots on the leaves. If indoor conditions do not allow creating the lighting necessary for light-loving plants, then they must be illuminated with fluorescent lamps.

Plants that require little lighting

Such plants develop best in moderate light, but, if necessary, they do well in both a south and north-west window. These include some types of cryptomeria, rapis, ficus, aucuba, monstera, bignonia, chlorophytum, chloranthus and others.