Leaf arrangement, leaf mosaic. Sheet mosaic Sheet mosaic

Leaf arrangement is the arrangement of leaves on a stem.

There are 3 main types of leaf arrangement:

Regular, or spiral,

characterized by the fact that the leaves sit on the stem one at a time, alternating with each other (in birch, apple, rose);

Opposite

2 leaves depart from the node, located one against the other (lilac, yasnotka, mint);

Whorled

3 or more leaves depart from the node (for elodea, crow's eye, oleander). The leaves are placed on the plant in such a way as not to obscure each other - in the form of a leaf mosaic. This allows more efficient use of the sun's rays. total area leaves many times the area occupied by the plant itself.

Layered categories are nothing more than sheet formations, i.e. types of leaves of one shoot, which differ in shape and location on the shoot. There are 3 types of leaves:
- riding - develop in the area of ​​\u200b\u200bthe inflorescence, these are bracts. They are underdeveloped, with a slightly dissected leaf blade, green (may attract pollinators and be brightly colored in this case);
- median - develop in the middle part of the shoot. They are green (perform the function of assimilation), have the largest size, the leaf blade is characterized by the greatest degree of dissection;
- grassroots - develop in the lower part of the shoot. They are white at first, then turn brown as the leaves age, and turn black when they die. They perform the function of protection or storage, or both.

Leaf mosaic- the location of the leaves of plants in one plane, usually perpendicular to the direction of the rays of light, which ensures the least shading of the leaves of each other.

Leaf mosaic is the result of uneven growth of leaf petioles and leaf blades that reach for the light and fill every lighted gap. In this regard, the size and even the shape of the leaves often change. Leaf mosaic can be observed on horizontal, less often on vertical branches of trees and shrubs in conditions of significant shading (lower branches of the crown of elm, linden, maple), on creeping shoots of grasses (hoof), on rosette shoots (geranium, plantain, dandelion). Leaf mosaic is an important adaptation to maximize the use of diffused light and can be formed in any type of leaf arrangement - spiral, opposite, whorled.

The life span of green leaves developed on shoots varies from plant species to 2-3 weeks to 20 years or more. In general, it should be noted that the leaves of perennial plants, compared with the stem and root, have the shortest life span. This is apparently due to the fact that the leaf tissues, having formed, are no longer renewed, and on the other hand, the leaves during their relatively short life are very active.

Distinguish plant types deciduous and evergreen. The former are characterized by the fact that annually for a certain period they are in a leafless state, and this period usually coincides with unfavorable conditions. external environment. For example, most of our trees and shrubs do not have leaves in winter.

Evergreens are characterized by the presence of green leaves during all year round. But this does not mean that their leaf is preserved and functions forever, throughout the life of the individual. Evergreens also have leaf fall, but older leaves fall from the plant and the leaves that formed at a later date are always preserved.

Tropical rainforests are characterized by evergreens, although there are also plants with leaves that last less than a year. But during this period of time, the buds repeatedly open and give rise to new leafy shoots. In tropical forests, plants with leaves that live for several years are also common. There are plants that, although for a short period of time in the year, may be in a leafless state.

In evergreens near Moscow - spruce and pine - the leaves persist for 5-7 (for spruce) and 2-4 (for pine) years. The life span of spruce needles is longer in plants growing in the Kola Peninsula and the Subpolar Urals, where it reaches 12-16, and in some cases 18 (22) years. The needles of the Tien Shan spruce (Picea scgenkiana F. et. M.) in the Zailiysky Alatau, where leaves of 26-28 years of age, were found for a long time.

leaf fall- a biological process, due to the development of the plant organism and its vital activity. Leaf fall is preceded by leaf aging: the intensity of vital processes occurring in its cells (photosynthesis, respiration) decreases, the content of ribonucleic acid, nitrogen and potassium compounds decreases. Hydrolysis prevails over the synthesis of substances; end products of decay accumulate in cells (for example, calcium oxalate crystals). The most valuable mineral and plastic compounds leave the leaves. Their outflow usually coincides either with the formation and growth of new organs, or with the deposition of reserve substances in ready-made storage tissues. In experiments, it was possible to extend the life of the leaves by removing buds or other formations on the plant, where plastic and mineral substances from the leaves can enter. The transfer of substances to places of their reuse is considered as one of the causes of aging and leaf fall.

Thus, the lifespan of a leaf is determined by the processes of growth and development of the plant organism as a whole.

In most trees and shrubs, during the period of leaf fall, the leaves change color and become yellow or crimson. Their yellow color is due to plastid pigments (carotene and xanthophyll) and cell sap (flavones).

The reddish-crimson color of the leaves is provided by the accumulation of anthocyanin pigment in the cell sap, which changes its color depending on the pH of the medium. In an alkaline environment, the anthocyanin takes on a bluish-blue color, and in an acidic environment, it becomes pink-purple. In some plants (alder, lilac), the leaves retain green color before dying.

In addition to the biochemical transformations that occur in the leaves before they fall, anatomical changes are also observed at the base of the leaf. Perpendicular to the longitudinal axis of the petiole, cells of the separating layer are laid near the stem. The intercellular substance connecting these cells becomes mucilaginous, and the cells separate from each other. At the place of separation of the leaf from the side of the stem, layers of cells are formed by this time, the membranes of which are corked. The resulting layer of cork protects the internal tissues of the stem in place of the detached leaf.

After the formation of a separating layer and the disruption of the connection between the cells, the leaf continues to remain on the tree for some time due to the conductive bundles connecting the leaf to the stem. But there comes a moment of violation of this connection, and the leaves fall.

21. types of reproduction of higher plants. Methods of vegetative propagation

Plant reproduction. One of the essential properties of a living organism is the reproduction of offspring, that is, the ability of one individual to give rise to a whole series of similar daughter individuals, or at least one.

There are two fundamental various ways reproduction: sexual and asexual.

Asexual reproduction.

There are two types of asexual reproduction: vegetative and actually asexual. In some lower plants, there is no clear boundary between these types of reproduction.

vegetative reproduction.

It is carried out by parts of the thallus, root, stem, leaf. It is based on the ability of plants to regenerate - to restore the whole organism from its part.

In unicellular plants (algae), vegetative reproduction occurs by cell division, in colonial and lower multicellular plants, by dividing the thallus into parts.

In higher plants, vegetative reproduction is carried out by parts of the root, stem, leaf or their modifications - rhizomes, tubers, bulbs, brood buds. Based on natural vegetative propagation in practice Agriculture various methods of artificial vegetative propagation of vegetable, fruit and ornamental plants have been developed. For this, the most commonly used are: tubers (potatoes, sweet potatoes, dahlias), rhizomes (iris, phlox), mustaches (strawberries), bulbs (onions, tulips), root suckers (raspberries, cherries). Many cultivated plants are propagated by cuttings, layering, and also by grafting.

Propagation by cuttings. A stalk is a section of a shoot, root, or leaf cut off from the mother plant. When propagating by cuttings, it is necessary to remember the law of polarity.

shoot cuttings can be winter - without leaves (but with buds), 20 - 30 cm long, at the age of 1 - 3 years, and summer - with leaves, 3 - 4 cm long, from the shoots of the current year.

leaf cutting consists of a leaf blade and petiole. Adventitious roots appear more often on the morphologically lower side of the leaf in places where large veins branch, buds, and then shoots - on the upper side. Only a few plants (lily, begonia, aloe, etc.) can be propagated by leaf cuttings.

Root cuttings propagate plant species whose roots easily form adventitious buds (raspberries, cherries, plums, date palms, roses, phlox, etc.).

Reproduction by grafting. Grafting is the fusion of cut buds or stem cuttings of one plant (propagated) with another (rooted). In this case, the propagated plant is called scion, and the plant to which it is grafted, - rootstock.

About 100 different methods of vaccination are known, but they can be reduced to three main types:

inoculation by rapprochement, or ablactation, - the graft is not separated from the mother plant until it grows together with the stock;

cutting grafting, or copulation, - on annual cuttings of the scion with 2-3 buds and on the stem of the stock, oblique cuts are made and applied to each other, while the stems of the scion and stock are selected of the same thickness so that their cambial layers coincide. If the diameters of the scion and rootstock do not match, then the vaccination is done split, under the bark, butt or in other ways;

inoculation, or budding, - a dormant or growing bud is used as a scion, separated from the middle part of the shoot of the propagated plant, which is inserted under the rootstock bark.

Intergrowth occurs best if the scion and rootstock belong to the same species or close species of the same genus, but if they belong to different genera, intergrowth is difficult.

Leaf mosaic

the location of the leaves of plants in one plane, usually perpendicular to the direction of the rays of light, which ensures the least shading of the leaves of each other. L. m. is the result of the uneven growth of leaf petioles and leaf blades, which reach for the light (see Phototropism) and fill every illuminated gap ( see pic .). In this regard, the size and even the shape of the leaves often change. L. m. can be observed on horizontal, less often on vertical branches of trees and shrubs in conditions of significant shading (the lower branches of the crown of elm, linden, maple), on creeping shoots of grasses (hoof), on rosette shoots (geranium, plantain, dandelion). L. m. is an important adaptation to the maximum use of scattered light and can be formed with any type of leaf arrangement (See leaf arrangement) - spiral, opposite, whorled.

Great Soviet Encyclopedia. - M.: Soviet Encyclopedia. 1969-1978 .

See what "Sheet mosaic" is in other dictionaries:

Characteristic for shade-tolerant plants. Ivy ordinary Leaf mosaic arrangement of plant leaves in one plane, usually perpendicular to the direction of the rays of light, which provides the least ... Wikipedia

sheet mosaic- the arrangement of leaves in space, in which they shade each other less and are better illuminated (see Fig. Leaf mosaic: a - for ivy; b - for elm) ... Plant anatomy and morphology

MOSAIC OF BEET- English mosaic of sugar beet German Mosaik, Zuckerrübe French mosaïque de la betterave pathogen: Aphidophilus betae Ryzhkov; Beta virus 2 (Lind.) Smith; Marmor betae Holmes see …

SUGAR, FODDER, LEAF AND TABLE BEET- English Sugar beet; fodder beet; chard; table beet; garden beetroot German Zuckerrübe; Futterrube; Mangold; rote Rübe French Betterave à sucre; b. fourragere; b. a cards; b. rouge lat. Beta vulgaris L. spp. et var cult. div... Phytopathological dictionary-reference book

- (Latin folium, Greek phyllon), one of the main organs of higher plants, occupying a lateral position on the stem (shoot axis) and performing the functions of photosynthesis, transpiration and gas exchange. As a rule, L. is a flat dorsiventral organ, the shape of which is ... Biological encyclopedic dictionary

I (List) Wilhelm (born May 14, 1880, Oberkirchberg, Württemberg), General Field Marshal of Nazi Germany (1940). In the army since 1898. He graduated from the Military Academy (1912). Member of the 1st World War 1914 18, then served in the Reichswehr. In 1938 he commanded ... ...

- (from Photo... and Greek trópos - turn) change in the direction of growth of plant organs under the influence of one-sided incident light. There are positive F., for example, the bending of the stem towards the light source, plagiotropism, or Diatropism, of the plates ... ... Great Soviet Encyclopedia- ... Wikipedia

In tree species, the next arrangement of leaves on the branches is most often observed. If, at the next arrangement of leaves, we connect the places of attachment of the leaves with a line, then it turns out that the leaves are arranged in a spiral. Therefore, the next leaf arrangement is also called spiral. Birch, beech, birch bark, elm, oak, elm, linden have such a leaf arrangement.

In many tree species, the leaves are located opposite each other, i.e., two leaves are formed in one node. Oppositely, the leaves are located in maple, ash, honeysuckle, spindle tree, lilac, viburnum.

In some tree species, the nature of the leaf arrangement changes with age. For example, in eucalyptus trees on young shoots, the leaf arrangement is usually opposite, on older ones it is alternate.

Less often, a whorled arrangement of leaves is observed when in one node, as, for example, in an oleander, whorled sciadopitis (Sciadopitys verticillata), several leaves are formed.

To better capture the light, the leaves of tree species are arranged so as to shade each other less. This is achieved by the fact that the lower leaves, by changing the length of the petiole, the size, and sometimes the shape of the leaf blade, occupy the gaps between the upper leaves. It turns out a kind of "leaf mosaic".

In a decorative sense, the leaf mosaic of many tree species is very effective and should be taken into account in architectural compositional solutions.

The mosaic arrangement of the leaves increases the density of the tree crown and is its important ornamental detail.

The decorativeness of leaf mosaic is especially pronounced in climbing plants covering the walls of buildings and garden structures (pavilions, pergolas, trellises, grottoes, retaining walls) should be taken into account when selecting tree species for these purposes.

Very decorative, for example, leaf mosaic in ivy, grapes (different types), aristolochia, actinidia.

Maples are also distinguished by expressive leaf mosaics, especially small-leaved ones, with a beautiful leaf ornament: beautiful maple, field maple, palm maple, hornbeam, oak, large-leaved linden, white mulberry.

LEAF COLOR

The color of the leaves at different times of the year is of great importance when using tree plantations for decorative purposes.

Each type of woody plant has its own characteristic leaf color.

The normal color of the leaves of woody plants is green of varying intensity and different shades (from light green to dark green).

The intensity of the green color of the leaf depends on the amount and intensity of the color of chlorophyll grains in the cells of the leaf, and the shade of green depends mainly on the nature of the integumentary tissue of the leaf: a smooth, shiny (glossy) surface of the integumentary tissue of the leaf (cuticle) enhances the intensity of the main green color of the leaf; on the contrary, a bluish or whitish waxy coating on the surface of the leaf gives the leaf a duller, matte hue.

Finally, in many tree species, outgrowths of cells in the form of fluffs or hairs form on the surface of the leaf from the integumentary tissue, which give the leaf a grayish-green or silvery-white tint.

The quantity and intensity of color of chlorophyll grains, as well as the nature of the outer cover of the leaf, in most cases are not the same on the upper and lower sides of the leaf.

Most often, the intensity of the green color is stronger on the upper side of the leaf, and the pubescence is stronger on the underside of the leaf.

Therefore, in most tree species, the underside of the leaf has a lighter color than the top.

The color of the leaves of tree species is subject to age and seasonal changes.

In all tree species, both deciduous deciduous evergreens and conifers, they have a brighter light green (sometimes even yellowish-green) color, which in older leaves that have completed their development turns into green and dark green.

In the spring, new bright yellowish-green needles appear from the opening buds of the common spruce, which stands out in contrast against the background of the dark green old needles and gives the tree a very elegant spring look.

Young leaves of birch, oak, maple, willow, poplar with their bright fresh greenery differ from the darker leaves of the same species in the summer.

In some woody plants, young, freshly blossomed leaves have a very effective pinkish and reddish color, which gradually turns into normal green as the leaf develops (in ginnal maple, red elderberry).

A lighter and brighter spring color of the leaves, corresponding to the early period of their development, is observed in all tree species. This color is quickly replaced by a darker summer color, which persists until autumn.

In addition to the light and bright spring color of the leaves, many deciduous tree species (and some conifers and evergreen deciduous trees) also have a bright autumn color.

Finally, in addition to the leaf color typical for each type of leaf color with its age and seasonal changes, many species of tree species have varieties (forms) with a variety of leaf colors that differ very sharply from the typical for a given species and undergo neither age nor seasonal changes, for example, blue and silvery forms of prickly spruce, red-leaved form of English oak, etc.

From the above, the complexity of systematizing leaf colors in tree species and constructing an appropriate classification, theoretically justified and suitable for practical purposes, is clear.

Keeping in mind, first of all, practical purposes, we consider separately the following leaf colors in tree species:

1) typical (normal) summer in the main types of tree species;

2) autumn in the same species;

3) color patterns in varieties.

The typical color of leaves in the main species of tree species, characteristic of them in summer period, can be presented in the following variety of colors and their shades.

a) LIGHT GREEN LEAVES have:

deciduous trees - ailanthus, maakia (Amur acacia), Manchurian aralia, warty birch, paper birch, fluffy birch, bignoniform catalpa; magnificent catalpa, ash-leaved maple, large-leaved linden, maklura, Berlin poplar, white mulberry;

deciduous shrubs - acacia yellow, hydrangea tree, hydrangea paniculata, pomegranate, honeysuckle golden cinquefoil artisanal, pteleya three-leafed (elm), vesicle tree-like, rhododendron yellow (azalea pontica), rowanberry-leaved, golden currant, spirea oak-leaved, mock orange;

evergreen trees and shrubs - Siebold's aralia, pittosporum (resin seed) variegated, mastic pistachio;

coniferous trees - European and Siberian larches, Italian pine (pinia), Alepska pine, Japanese thick-flowered pine, common taxodia (marsh cypress);

coniferous shrubs - eastern biota (thuja), western thuja.

b) GREEN COLOR LEAVES have:

deciduous trees - white locust, sticky locust, albizia (acacia) Lankaran, bereka, hazelnut, honey locust three-thorn, common hornbeam, brittle willow, catalpa ovoid (K. Kaempfer), field maple, oriental plane tree, balsamic poplar, fragrant poplar, laurel poplar , black mulberry, Pennsylvania ash:

deciduous shrubs - amorpha, red elderberry, wisteria (wisteria) many-flowered, dog rose (common dog rose);

evergreen trees and shrubs - gardenia, racemose distillum, richly colored jasmine, camphor laurel, false camphor laurel, Tobir's pittosporum;

coniferous trees - river cedar, large-fruited cypress, lusitanian cypress, Japanese cryptomeria, pseudosuga yew-leaved. evergreen sequoia, common pine, giant thuja.

c) DARK GREEN LEAVES have:

deciduous trees in the common apricot, cherry plum, Amur velvet, succulent beech, forest beech (b. ordinary), black elderberry, common cherry, leafy elm, rough elm (mountain elm), common pear (city of forest), sessile oak (for winter), horse chestnut, Norway maple, false sycamore maple (sycamore), styrax liquid dambar (ambergris tree) small-leaved linden, Manchurian linden, black alder, black walnut, Canadian black poplar poplar , bird cherry, bird cherry Magalebskaya (cherry Magalebskaya), bird cherry, late bird cherry, common ash;

deciduous shrubs - Japanese quince, Thunberg barberry, warty euonymus, European euonymus, common privet, Siberian hawthorn, blue honeysuckle, common dogwood, Imeretian buckthorn, laxative buckthorn, rose rugosa (r. wrinkled), red svidina (red derain), common lilac , Spirea Vangutta;

deciduous climbing - Amur grapes, grape clematis, purple clematis, five-leaf parthenocissus (virgin grapes);

evergreen trees and shrubs - Japanese euonymus (small-leaved form), brilliant privet, Japanese privet, Japanese viburnum, Chinese camellia, Japanese camellia, officinalis laurel, noble laurel, large-flowered magnolia, holly magonia, holly osmanthus, holly, Pontic rhododendron, cycad, boxwood , tea bush;

evergreen curly - common ivy, Colchis ivy;

coniferous trees - Chilean araucaria, common spruce, Siberian spruce, evergreen cypress (horizontal and pyramidal forms), Caucasian fir, Numidian fir, black pine, yew berry;

coniferous shrubs - Cossack juniper, mountain pine.

d) GRAY-GREEN OR SILVER-WHITE LEAVES have:

deciduous trees - pear pear, willow pear, white willow, goat willow, silver maple, felted linden, white alder, gray walnut, aspen, round-leaved mountain ash, white poplar;

deciduous shrubs - buddley David (b. changeable), comb (tamarix), different types; Albert's honeysuckle, gray willow, viburnum-gordovina, silver sucker, narrow-leaved sucker, edible sucker, sea buckthorn, silver chemysh (chingil);

evergreen trees and shrubs and - silver acacia, European olive, prickly sucker, rosemary, feijoa, Japanese eriobothria (medlar);

coniferous trees - white spruce, prickly spruce (silver form), Atlas cedar (silver form), Weymouth pine, Himalayan pine, Mexican five-needle pine, Rumelian pine, Sabina pine.

e) BLUE-GREEN OR BLUE-GREEN LEAVES have:

deciduous trees - tulip tree;

deciduous shrubs - honeysuckle honeysuckle, skumpia;

evergreen trees and shrubs - butia Bonetta (b. Brazilian), capitate butia, hybrid butia, large-stem daphnelist, magnolia virginia (m. blue), bluish stranvesia, forest date, ash eucalyptus, erythea armed (blue palm);

coniferous trees - Engelman's spruce, Atlas cedar (blue form), Arizona cypress, McNab cypress, Lawson's cypress, Japanese larch, single-color fir, gray-gray false suga (l. blue).

When distributing the main species of woody plants used in green building in the USSR into groups according to leaf color, it must be borne in mind that the color of the leaves is influenced by growing conditions. So, for example, in many tree species with a lack of iron in the soil, a lighter, sometimes yellow, color is observed (the phenomenon of the so-called “chlorosis” of leaves). Excess lime in the soil has the same effect on some tree species.

download

Abstract on the topic:

Leaf mosaic

Leaf mosaic is typical for shade-tolerant plants. Ivy

Leaf mosaic- the location of the leaves of plants in one plane, usually perpendicular to the direction of the rays of light, which ensures the least shading of the leaves of each other.

Leaf mosaic is the result of uneven growth of leaf petioles and leaf blades that reach for the light and fill every lighted gap. In this regard, the size and even the shape of the leaves often change. Leaf mosaic can be observed on horizontal, less often on vertical branches of trees and shrubs in conditions of significant shading (lower branches of the crown of elm, linden, maple), on creeping shoots of grasses (hoof), on rosette shoots (geranium, plantain, dandelion). Leaf mosaic is an important adaptation to maximize the use of diffused light and can be formed in any type of leaf arrangement - spiral, opposite, whorled.

Role in plant life

Leaf mosaic - a phenomenon in which the leaves are located in space on the shoots of one individual in such a way that their plates do not obscure each other. Leaf mosaic allows the plant to more rationally use the sunlight falling on it. Sheet mosaic:

• causes the formation of light and shade effects under the crown of the tree;
• gives picturesqueness and originality to the appearance of the plant.

download
This abstract is based on an article from the Russian Wikipedia. Synchronization completed on 07/17/11 00:31:53
Related abstracts: plants in the same plane, usually perpendicular to the direction of the light rays, which ensures the least shading of each other's leaves.

Leaf mosaic is the result of uneven growth of leaf petioles and leaf blades that reach for the light and fill every lighted gap. In this regard, the size and even the shape of the leaves often change. Leaf mosaic can be observed on horizontal, less often on vertical branches of trees and shrubs in conditions of significant shading (lower branches of the crown of elm, linden, maple), on creeping shoots of grasses (hoof), on rosette shoots (geranium, plantain, dandelion). Leaf mosaic is an important adaptation to maximize the use of diffused light and can be formed in any type of leaf arrangement - spiral, opposite, whorled.

Role in plant life

Leaf mosaic- a phenomenon in which the leaves are located in space on the shoots of one plant in such a way that their plates do not obscure each other. Leaf mosaic allows the plant to more rationally use the sunlight falling on it. Sheet mosaic:

• causes the formation of light and shade effects under the crown of the tree;
• gives picturesqueness and originality to the appearance of the plant.