The external structure of the leaf. Variety of leaves in shape and size. External structure of a leaf Chart the variety of leaves when charting

The root is the main organ of plants, which performs the most important functions: fixing in the soil, holding and storing water and minerals dissolved in it. All plants need to perform these tasks, but not equally. That is why there is a huge variety of root systems.

Root systems are divided into two groups:

1. Tap root system: there is a main root from which lateral roots spread through the soil (dicotyledonous plants);
2. Fibrous root system: the main root cannot be distinguished, all roots are the same (monocot).

Depending on the habitat, plants differ in the length of the roots. Desert plants have extremely long roots to extract moisture from deep groundwater. And tundra plants, because of the permafrost, have to keep their roots near the surface. This length of roots cannot provide good nutrition, so the plant grows small to conserve nutrients.

The metamorphoses of the roots do not end there. Some plants went further and came up with bizarre forms, which they called modifications of the roots.

Root changes:

Leaf variety

A leaf is a plant organ that is responsible for photosynthesis and water evaporation (transpiration). Plants have different nutrient and water requirements, so there is a variety of leaves.

According to the external structure, the leaves are:

1. Petiolate: leaves are connected to the stem with a petiole (oak, birch);
2. Sessile: leaves attached to the stem by the base of the leaf blade (aloe, wheat).

Variety of leaves in external structure:

Leaves differ in venation:

1. Net venation: small veins depart from a large vein, which form a whole network; mesh, in turn, is divided into pinnate and palmate (cherry, pear, apple tree);
2. Parallel venation: veins are arranged in parallel (wheatgrass, cereals);
3. Arc venation: veins are arranged in an arc (plantain, lily of the valley, tulip).

Leaf venation:

Depending on the habitat and soil moisture, plants have a different shape of leaves. If the plant lives in a humid area, it will have large leaves with lots of stomata. Such a plant does not save moisture and is not afraid to get an extra portion of sunlight. If the plant lives in an arid area, it will have narrow leaves with few stomata. Often these plants have additional protection against moisture loss: a wax coating and a thick cuticle.

Cardinal modifications of parts of the plant did not bypass the leaves.

1. Thorns. Such a modification can have two purposes: either the plant greatly reduces the surface to slow down the evaporation of water (cactus), or it protects itself from herbivores (barberry).
2. Water storage sheets. Plants of arid habitats (aloe) have such modified leaves. With their help, the plant retains the necessary moisture.
3. Antennae. With the help of such leaves, plants are attached to a support (peas). Do not confuse with sucker roots and trailer roots: although the function is the same, the origin is different. Antennae develop from former leaves, and sucker roots and trailer roots develop from roots.
4. Leaves of carnivorous plants. Insectivorous plants live on poor soils, so they have adapted to extreme conditions in an extreme way (Venus flytrap). On the surface of such leaves there are special glands that secrete digestive enzymes (pepsin) and organic acids (formic acid). If an insect gets on the trapping organ of such a plant, its secretion (excretion) of digestive substances increases. Glandular hairs bend towards the insect (dew) or bend the edges of the leaf on which the insect is located (fatty). After capturing prey, enzymes begin to work actively and break down insects into simple substances that the plants themselves can use. Thus, the leaves of insectivorous plants are able to digest insects, thereby replenishing the supply of nutrients.

Leaf modifications:

Variety of stems

The stem of a plant is a part of the shoot that performs a number of important functions: holding and storing substances, protection, ensuring vegetative propagation, attachment to a support. To provide all the functions a plant needs, there is a variety of stem types.

Variety of stems according to the degree of woodiness:

Variety of stems by cross-sectional shape:

In the direction of growth:

1. Upright: for this type of stem, the plant must have mechanical tissue (birch);
2. Climbing: such plants are able to wrap around a support (bindweed);
3. Climbing: use modified organs (grapes) to attach to the support;
4. Lying: lie on the ground (loosehair);
5. Creeping: also lie on the ground, but can take root (strawberry).

Variety of stems in the direction of growth:

Depending on the characteristics of the stem listed above, life forms of plants are distinguished:

1. Tree: a plant with a woody stem that has a main stem (birch);
2. Shrub: a plant with a woody stem that does not have a main stem when mature, that is, when the plant has reached its peak of development (lilac);
3. Shrub: a stunted plant that does not have a main stem when mature (blueberry);
4. Herbaceous Plant: An annual, biennial, or perennial plant with a herbaceous stem (clover).

Life forms of plants:

Variety of shoots

A shoot is a terrestrial vegetative organ of a plant, which is a stem with leaves and buds. The shoots of some plants have changed so much that they are easily confused with other parts, for example, with a root. In this difficult matter, only maximum concentration will help.

Escape modifications:

1. Tubers. The potato fruit is actually a modified shoot called a tuber. Underground potato shoots are called stolons, and the tuber is its thickening. On the surface of the potato tuber, especially at the top, there are buds - eyes. Such a total modification of the shoot is necessary for a large deposition of nutrients, in particular starch.
2. bulbs. Such modifications can be seen directly in the onion or tulip. If you cut the onion, you can see its parts: the bottom and scales. The bottom is located in the lower part and is a residual flat stem. Above it are modified leaves - scales. This modification serves to accumulate water and nutrients in the succulent inner scales.
3. Rhizomes. The rhizome of the plant is easily confused with the root, but this is a modified shoot, as it has buds on its surface. Due to this, both adventitious roots and new shoots can grow from the rhizome. In practice, reproduction by rhizomes is used: an independent plant grows from a rhizome site placed in the soil. Many plants have such a modification, for example, nettle and lily of the valley.
4. spikes. Reducing the surface of the stem serves to reduce evaporation and protect against herbivores (acacia).
5. Mustache. Whiskers allow strawberries to reproduce vegetatively and spread over various distances.
6. storage shoots. Based on the name, such shoots perform the function of storing water and nutrients (cactus, orchids).

Escape modifications:

Variety of flowers

A flower is a plant organ that is intended for sexual reproduction. Despite the fact that the flower performs only one function, diversity has not bypassed this part of the plant.

Perianth type:

Perianth types:

According to the different form of flowers:

Correct and incorrect flowers:

Dioecious and bisexual flowers:

A flower formula is used to describe a variety of flowers. To use it, you need to remember the parts of the flower.

The flower formula includes the following abbreviations:

1. O - simple perianth;
2. H - sepals;
3. L - petals;
4. T - stamens;
5. P - pestle;
6. ∞ - if the number is greater than 12;
7. * - the right flower;
8. - the wrong flower;
9. ♀ - same-sex female;
10. ♂ - same-sex male.

For example, the formula of a stamen flower of a cucumber will be presented as follows: ♂ * H (5) L (5) T (5) P0, that is, it is a regular same-sex male flower with five fused sepals, five fused petals, five fused stamens, no pistil. If the number is not enclosed in brackets, then this part of the plant does not grow together.

Variety of inflorescences

Inflorescence - several flowers connected with each other. With the help of the appearance of inflorescences, plants increase the likelihood of pollination by insects: from a long distance, inflorescences can be seen better.

The variety of inflorescences is great:

1. Simple inflorescences: in such inflorescences, flowers (plantain) sit on the main axis (the main pronounced shoot);
2. Complex inflorescences: in such inflorescences, other simple inflorescences (lilacs) sit on the main axis;
3. Naked inflorescences: in such inflorescences, bracts (leaves on a stalk under the very base of the flower) are reduced or completely absent (shepherd's purse);
4. Leafy inflorescences: in such inflorescences, the bracts are strongly developed (violet).

Simple and complex inflorescences:

In turn, simple inflorescences are divided into:

1. Brush: pedicels are located on the long axis, at the ends of which there are flowers (cabbage);
2. Simple ear: sessile flowers (plantain) are located on the long axis;
3. Cob: sessile flowers (corn) are located on a long thick axis;
4. Simple umbrella: long pedicels emerge from the top of the axis (primrose);
5. Scutellum: pedicels are located on the long axis, while the lower ones are much longer than the upper ones (pear);
6. Head: sessile flowers (clover) are located on a shortened axis;
7. Basket: sessile flowers (sunflower) are located on the extended axis.

Simple inflorescences:

And complex inflorescences are as follows:

1. Panicle (complex brush): brushes (lilac) are located on the axis;
2. Complex ear: spikelets (wheat) are located on the axis;
3. Complex umbrella: umbrellas (parsley) are located on the axis;
4. Monochasium: on an unexpressed axis there is one axis of the second and third order;
5. Dichasium: two axes of the second and third order are located on the unexpressed axis;
6. Pleochasium: more than two axes of the second and third order are located on an unexpressed axis.

Complex inflorescences:

Variety of fruits

The fruit is the organ of the plant in which the seeds are located for further distribution. Fruit parts: pericarp and seed. The pericarp (pulp) protects valuable seeds from adverse environmental conditions.

Classification of fruits by complexity:

1. Simple (real) fruit: develops from a flower that has one pistil (pea);
2. Complex fruit: develops from a flower that has several pistils (raspberries);
3. Inflorescence: develops from a whole inflorescence (pineapple).

Variety of fruits by complexity:

By number of seeds:

1. One-seeded fruits (nut);
2. Multi-seeded fruits (apple tree).

By consistency:

Depending on the structure of the fetus, varieties are distinguished:

Berry fruits. These fruits have a juicy pericarp with many seeds inside.

1. Berry: no doubt everyone has tried berries; these juicy fruits are covered with a thin skin (cranberries, blueberries);
2. Apple: surprisingly, not only the apple tree has an apple; an apple is called an apple - a false fruit, in the formation of which an overgrown receptacle (apple tree, hawthorn) participates;
3. Pomeranian: citrus fruit (lemon, tangerine).

Berry fruits:

Drupe fruits. These fruits have a juicy pericarp and hard seeds (one or more).

1. Drupe: a juicy fruit with a lignified center of the pericarp - a stone (cherry, apricot);
2. Polydrupe: a group of drupes formed from a single flower (raspberry, blackberry).

Drupe fruits:

Nutty fruits. These indehiscent fruits have a dry pericarp and one seed.

1. Nut: this fruit has a woody pericarp (walnut, hazelnut);
2. Nut: small nut (buckwheat, hemp);
3. Multi-nutlet: several nuts are located on an overgrown receptacle (strawberry);
4. Acorn: a fruit with a cupule - a cup-shaped organ that looks like a saucer (oak);
5. Hemicarp: This variety of fruit has a leathery pericarp that does not fuse with the seed (sunflower);
6. Caryopsis: unlike the achene, the membranous pericarp of the caryopsis fuses with the seed (wheat, corn).

Walnut fruits:

Box-shaped fruits. These opening fruits have a dry pericarp and many seeds.

Box fruits:

With this variety of seeds and fruits, plants have developed many strategies for dispersing seeds over long distances. Fruits and seeds can be moved by water, wind, animals and self-propagation.

1. Hydrochory - distribution by water. This is how the seeds of aquatic plants (water lily, pod) move. For this, plants have come up with special devices - water bubbles that prevent sinking to the bottom. Thus, currents carry seeds over long distances.
2. Anemochory - spread by wind. This is how dry and light fruits and seeds (ash, maple) move. To do this, bizarre outgrowths or tufts are formed in plants, which contribute to the movement of wind currents.
3. Zoochory is the distribution of animals. In order for the plant to move with the help of animals, you can go in two ways: either come up with special outgrowths, or have a juicy pericarp. If the plant has hooks and spines, then it is able to cling to the skin of an animal and thus travel a long distance (burdock). If the plant has a juicy pericarp, then with great probability the bird will eat it, digest it and throw out the seed intact (blueberries). The dispersal of seeds by birds is called ornithochory.
4. Anthropochory is spread by man. Seeds can be attached to bags when transporting goods (plantain).
5. Autochory is spreading by self-spreading. This is how opening fruits (peas, beans) move. With this method, the distance over which the seeds spread is small.

Textile

Where is located

Features of the structure of cells

Meaning

educational

stem tops
root tips
Cambium
Wound

Small dividing cells without vacuoles

plant growth

Integumentary

epidermis (skin)
Cork
Bark

Living and dead cells with thick and strong membranes, tightly adjoining each other

Protection against adverse effects

Mechanical

Lub
Wood

Thick lignified shells

Support for plant organs

Conductive

Vessels of wood
Bast sieve tubes

sieve tubes

The distribution of substances entering the roots and formed in the leaves throughout the body

Main

leaf pulp
stem core
Root

Chloroplasts in cells

Formation and accumulation of nutrients

excretory

Nectaries
glands

Isolation of essential oils, water, nectar

Cell - the basic structural and functional unit of the living, the smallest living system.
Textile - a group of cells that are similar in structure and perform the same functions.

Conductive tissues provide the movement of water and nutrients dissolved in it throughout the plant. There are two types of conductive tissue - xylem (wood) and phloem (bast).

Xylem - this is the main water-conducting tissue of higher vascular plants, which ensures the movement of water with minerals dissolved in it from the roots to the leaves and other parts of the plant (upward current). It also performs a supporting function. The composition of the xylem includes tracheids and tracheae (vessels) (Fig. 8.3), wood parenchyma and mechanical tissue.

tracheids are narrow, strongly elongated dead cells with pointed ends and lignified shells. The penetration of solutions from one tracheid to another occurs by filtration through pores - depressions covered by a membrane. Fluid flows slowly through the tracheids, as the pore membrane prevents the movement of water. Tracheids are found in all higher plants, and in most horsetails, club mosses, ferns and gymnosperms they serve as the only conducting element of the xylem. In angiosperms, along with tracheids, there are vessels.

Figure 8.3. Elements of xylem (a) and phloem (6): 1-5 - annular, spiral, scalariform and porous (4, 5) tracheas, respectively; 6 - coli and porous tracheids; 7 - sieve tube with companion cell.

Trachea (vessels) are hollow tubes consisting of individual segments located one above the other. In the segments on the transverse walls, through holes are formed - perforations, or these walls are completely destroyed, due to which the rate of flow of solutions through the vessels increases many times. The shells of the vessels are impregnated with lignin and give the stem additional strength. Depending on the nature of the thickening of the membranes, tracheas are annular, spiral, ladder, etc. (see Fig. 8.3).

Phloem conducts organic substances synthesized in leaves to all plant organs (downward current). Like xylem, it is a complex tissue composed of sieve tubes with companion cells (see Figure 8.3), parenchyma, and mechanical tissue. Sieve tubes are formed by living cells located one above the other. Their transverse walls are pierced with small holes, forming, as it were, a sieve. Sieve tube cells lack nuclei, but contain cytoplasm in the central part, the strands of which pass through the through holes in the transverse septa into neighboring cells. Sieve tubes, like vessels, stretch along the entire length of the plant. Companion cells are connected to sieve tube segments by numerous plasmodesmata and, apparently, perform some of the functions lost by sieve tubes (enzyme synthesis, ATP formation).

Xylem and phloem are in close interaction with each other and form special complex groups in plant organs - conducting bundles.

mechanical fabrics provide the strength of plant organs. They make up a frame that supports all plant organs, counteracting their fracture, compression, and rupture. The main characteristics of the structure of mechanical tissues, which ensure their strength and elasticity, are a powerful thickening and lignification of their membranes, close closure between cells, and the absence of perforations in cell walls.

Mechanical tissues are most developed in the stem, where they are represented by bast and wood fibers. In the roots, mechanical tissue is concentrated in the center of the organ.

Depending on the shape of the cells, their structure, physiological state and the method of thickening of the cell membranes, two types of mechanical tissue are distinguished: collenchyma and sclerenchyma, (Fig. 8.4).

Rice. 8.4. Mechanical fabrics: a - corner collenchyma; 6 - sclerenchyma; in -- sclereids from cherry plum fruits: 1 - cytoplasm, 2 - thickened cell wall, 3 - pore tubules.

Collenchyma It is represented by living parenchymal cells with unevenly thickened membranes, making them especially well suited for strengthening young growing organs. Being primary, collenchyma cells are easily stretched and practically do not interfere with the elongation of the part of the plant in which they are located. Usually, collenchyma is located in separate strands or a continuous cylinder under the epidermis of the young stem and leaf petioles, and also borders the veins in dicotyledonous leaves. Sometimes collenchyma contains chloroplasts.

Sclerenchyma consists of elongated cells with evenly thickened, often lignified shells, the contents of which die off in the early stages. Shells of sclerenchyma cells have high strength, close to the strength of steel. This tissue is widely represented in the vegetative organs of land plants and constitutes their axial support.

There are two types of sclerenchymal cells: fibers and sclereids.fibers - these are long thin cells, usually collected in strands or bundles (for example, bast or wood fibers).Sclereids - these are rounded dead cells with very thick lignified shells. They form the seed coat, nut shells, pits of cherries, plums, apricots; they give the pulp of pears a characteristic grainy character.

main fabric, or parenchyma , consists of living, usually thin-walled cells that form the basis of organs (hence the name tissue). It contains mechanical, conductive and other permanent tissues. The main tissue performs a number of functions, in connection with which there are assimilation (chlorenchyma), storage, air-bearing (aerenchyma) and aquifer parenchyma (Fig. 8.5).

Figure 8.5. Parenchymal tissues: 1-3 - chlorophyll-bearing (columnar, spongy and folded, respectively); 4-storage (cells with grains of starch); 5 - air, or aerenchyma.

Cellsassimilation t Cani contain chloroplasts and perform the function of photosynthesis. The bulk of this tissue is concentrated in the leaves, a smaller part - in young green stems.

In cagesreservingly th parenchyma deposits proteins, carbohydrates and other substances. It is well developed in the stems of woody plants, in roots, tubers, bulbs, fruits and seeds. In plants of desert habitats (cacti) and salt marshes, stems and leaves haveaquifer parenchyma, which serves to accumulate water (for example, in large specimens of cacti from the genus Carnegia, tissues contain up to 2-3 thousand liters of water). Aquatic and marsh plants develop a special type of basic tissue -air-bearing parenchyma, oraerenchyma. Aerenchyma cells form large air-bearing intercellular spaces, through which air is delivered to those parts of the plant, the connection of which with the atmosphere is difficult.

PLANT ORGANS

AUTHORITY - This is a part of a plant that has a certain location, as well as a characteristic shape and structure, and performs a specific function.

ROOT - axial underground vegetative organ.

Absorption and transport of water and dissolved mineral salts

Vegetative propagation

Release of metabolic products into the soil

Storage of nutrients

Synthesis of biologically active substances

Anchoring in the soil

ROOT ZONES

ROOT ZONES AND VALUE

Protects the top of the root from mechanical damage and ensures the advancement of the root in the soil.

Cells are actively dividing, root meristem. All root tissues are formed from this zone.

The presence of root hairs, Ensures the absorption of water and minerals dissolved in it..

The mediator between the root suction zone and the aerial part of the plant is located above the root hairs. Conductive vessels and lateral roots form in this zone.

TYPES OF ROOTS

TYPES OF ROOT SYSTEMS

1- Main root

corn

Lateral roots

All orchids

Swamp cypress, all swamp

Carrot beet

Dahlia, clean

The escape - This is the above-ground part of the plant, consisting of a stem and leaves and buds located on it.

Stem – axial aboveground vegetative organ of a plant. The shoot often performs the function of storing nutrients, vegetative propagation of plants and protecting them from being eaten. In such cases, it is modified.

STRUCTURE OF THE ESCAPE

SHOOTS MODIFICATIONS

Reminds me of a root. It has underdeveloped scaly leaves and buds, adventitious roots grow from the nodes. Nutrients are stored in the rhizome as a reserve. Most often, the rhizome is found in perennial grasses.

Examples: wheatgrass, valerian, lily of the valley, streptocarpus.

Underground shoot, on which the kidneys are located in the eyes. Tubers are underground aboveground. Tubers serve for plant reproduction, store nutrients and endure unfavorable periods of the year. Under favorable conditions, the tubers germinate easily and, thanks to the stored substances, give the beginning of young independent plants.

Example: potatoes, kohlrabi, gloxinia.

Tuber

Calla tubers

Dahlia tubers

potato tubers

It has a shortened stem, surrounded by succulent leaves, in the axils of which there are buds. Nutrients are found in the leaves. Bulbs help plants survive under adverse conditions and are organs of vegetative reproduction.

Example: onion, tulip, narcissus, hyacinth, hypeastrum, amaryllis.

Bulb of Narcissus

spines

They are found in the axils of the leaves and protect the plant from being eaten by animals.

Example: hawthorn, rose, blackthorn, wild apple tree, cactus.

Mustache

Thin, creeping stems with elongated internodes. They take root at the nodes and give rise to new plants.

Example: strawberries, strawberries.

tendrils

Curly shoots that, twisting around various supports, support the stem in a certain position.

STEM

Stem (for trees - the trunk, branches and shoots) serves as a link between the roots, through which water and minerals enter the plant, and the leaves, in which nutrients are synthesized.

FUNCTIONS:

Connects all parts of the plant

Supply of nutrients

Vegetative propagation

Provides water transport of mineral and organic substances

Forms and bears buds and leaves

STEM TYPES BY THE PRESENCE OF WOOD

herbaceous

Woody

TYPES OF STEMS BY PLACEMENT IN SPACE

Climbing plants: field birch, bindweed

Upright plants: all plants with upright stems: dandelion, clover, chamomile, etc.

Clinging plants China, grapes, cucumber, pumpkin, zucchini, melon.

Creeping: strawberries, strawberries.

INTERNAL STRUCTURE OF THE STEM

SHEET

Sheet - the lateral organ of the plant.
Functions- photosynthesis, gas exchange, transpiration.

LEAVES

Complex- consisting of several leaf plates: strawberries - trifoliate, mountain ash - unpaired pinnate, yellow acacia - paired pinnate.

Simple- consisting of one sheet plate: Linden, cherry, apricot, cereals.

Rice. 3.simple leaves : 1 - needle; 2 - linear; 3 - oblong; 4 - lanceolate; 5 - oval; 6 - rounded; 7 - ovoid; 8 - obovate; 9 - rhombic; 10 - spatulate; 11 - heart-shaped-ovoid; 12 - kidney-shaped; 13 - swept; 14 - spear-shaped : 1 - pinnately complex; 2, 3 - trifoliate; 4 - finger-complex.

VENTING -

Leaf fall - this is the dropping of leaves in perennial trees of shrubs; natural physiological phenomenon.

Fall value

Healthy for the plant and protection from excessive evaporation in autumn and winter

Fallen leaves are an excellent mineral and organic fertilizer

Prevention of freezing roots and crumbling seeds

KIDNEY TYPES

KIDNEY - a rudimentary shoot capable of maintaining the viability of meristems for a long time and protecting them from adverse conditions.

A - vegetative - stem growth to the top

B - vegetative-generative (vegetative reproduction reserve)

B - Generative (flowering) - contains the embryos of flowers and inflorescences

1 - rudimentary stem; 2- rudimentary scales; 3 - Rudimentary flowers; 4 - Rudimentary leaves; 5 - rudimentary kidneys.

Rice. sixteen . Escape structure: A - with leaves, B - after leaf fall

A. 1 - stem; 2 - sheet; 3 - node; 4 - internode; 5 - leaf axil; 6 - axillary kidney; 7 - apical kidney.

B. 1 - apical kidney; 2 - renal rings; 3 - leaf scars; 4 - lateral kidneys.

Rice. . Above-ground modifications of shoots:

1 - stem succulent; 2 - thorn; 3 - phyllocladium of butcher's broom; 4 - asparagus cladody; 5 - cabbage bud; 6 - strawberry stolons; 7 - mustache of grapes; 8 - a shortened cherry shoot; 9 - dandelion flower arrow.

Escape structure: LEAF:

People used to call a wide green plate a leaf. However, the external structure of the leaf is more complex. Consider the variety of forms, location on the stem, leaf venation.

Leaf parts

The leaf is a lateral organ of the shoot that emerges from the bud and is attached to the stem with the help of a petiole. The table "Characteristics of the external structure of the leaves" describes each part in more detail.

Leaves with petioles are called petiolate. In the absence of a petiole, the leaf blade grows from the stem. Such leaves are called sessile. An example is flax, wheat, dandelion.

Simple and complex

All leaves are divided into two types:

• simple - the leaf has one leaf blade;
• complex - consist of several leaflets attached to a common petiole.

In autumn, simple leaves fall completely along with the petiole. Example - birch, elm, aspen. Compound leaves break up into leaflets, and the common petiole is separated from the shoot. Examples are mountain ash, clover, wild rose.

By location on a common petiole, compound leaves are divided into three types:

• pinnate - leaflets lie on the sides of the petiole; subdivided into paripinnate - an even number, each leaf has a pair, and odd-pinnate - an odd number, ending with one leaf;
• palmately complex - leaflets depart from the top of the petiole in different directions;
• trifoliate - consists of three leaves.

The most complex leaves are twice or thrice pinnate or palmate. In these cases, the common petiole has branches.

Variety of forms

The leaves differ in the shape of the leaf blade. Leaves are:

• rounded;
• oval;
• needle;
• lanceolate;
• heart-shaped;
• ovoid;
• linear;
• sickle-shaped;
• fan-shaped;
• etc.

Rice. 1. Different forms of leaves.

The edges of the leaves are also varied. Allocate:

• entire (smooth);
• jagged;
• double-toothed;
• serrated;
• crenate;
• wavy;
• prickly;
• notched.

Depending on the depth of the excavation, the leaves are divided into three types:

• whole - depth less than a quarter 1/2 sheet (birch);
• dismembered - the recess does not reach the axis (oak);
• dissected - the recess reaches the center (potatoes).

Leaves can be arranged differently on the petiole. There are four types of location:

• next - one leaf per node one after another (apple tree);
• opposite - two sheets per node in both directions (mint);
• whorled - three or more leaves from one node (oleander);
• socket - in a circle at the same height (agave).

Rice. 2. Leaf arrangement.

Venation

Any plate, regardless of the shape and complexity of the structure, has an internal network of veins that conduct nutrients to the leaf cells. Also, the veins serve as a kind of skeleton - they keep their shape and give the sheet strength. Venation is of three types.

• Mesh . The main veins branch into smaller ones. The structure resembles a network. Reticulate venation is divided into three types - pinnatiform (apple), radial (ceanothus), palmate (maple). Typical of dicot plants.
• Parallel . The veins run parallel from the base to the top of the leaf. Found in monocots.
• Arc . It resembles parallel, but the veins repeat the rounded shape of the leaf, starting from the base and connecting at the top. An example is plantain, lily of the valley. Typical for monocotyledonous plants.

Rice. 3. Types of venation.

What have we learned?

From the 6th grade biology article, we learned about the components, diversity and shapes of plant leaves. Leaves are simple and complex, rounded and elongated with different edges, location on the shoot and type of venation.

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lesson type - combined

Methods: partially exploratory, problem presentation, reproductive, explanatory-illustrative.

Target:

Students' awareness of the importance of all the issues discussed, the ability to build their relationship with nature and society based on respect for life, for all living things as a unique and priceless part of the biosphere;

Tasks:

Educational: to show the multiplicity of factors acting on organisms in nature, the relativity of the concept of "harmful and beneficial factors", the diversity of life on planet Earth and the options for adapting living beings to the whole range of environmental conditions.

Developing: develop communication skills, the ability to independently acquire knowledge and stimulate their cognitive activity; the ability to analyze information, highlight the main thing in the studied material.

Educational:

Formation of an ecological culture based on the recognition of the value of life in all its manifestations and the need for a responsible, careful attitude to the environment.

Formation of understanding of the value of a healthy and safe lifestyle

Personal:

education of Russian civil identity: patriotism, love and respect for the Fatherland, a sense of pride in their homeland;

Formation of a responsible attitude to learning;

3) Formation of a holistic worldview, corresponding to the current level of development of science and social practice.

cognitive: the ability to work with various sources of information, convert it from one form to another, compare and analyze information, draw conclusions, prepare messages and presentations.

Regulatory: the ability to organize independently the execution of tasks, evaluate the correctness of the work, reflection of their activities.

Communicative: Formation of communicative competence in communication and cooperation with peers, older and younger in the process of educational, socially useful, teaching and research, creative and other activities.

Planned results

Subject: know - the concepts of "habitat", "ecology", "environmental factors" their influence on living organisms, "connections of living and non-living";. Be able to - define the concept of "biotic factors"; characterize biotic factors, give examples.

Personal: make judgments, search and select information; analyze connections, compare, find an answer to a problematic question

Metasubject:.

The ability to independently plan ways to achieve goals, including alternative ones, to consciously choose the most effective ways to solve educational and cognitive problems.

Formation of the skill of semantic reading.

Form of organization of educational activities - individual, group

Teaching methods: visual and illustrative, explanatory and illustrative, partially exploratory, independent work with additional literature and textbook, with DER.

Receptions: analysis, synthesis, conclusion, transfer of information from one type to another, generalization.

Goals: to acquaint with the variety of leaves, the features of their external structure; to teach to recognize leaves by types of venation, the shape of the leaf blade, the shape of the edge, the location on the stem, to distinguish between simple and complex leaves.

Equipment and materials: indoor plants, herbariums of plants with different types of leaf blades, willow leaf herbariums (for each desk).

Key words and concepts: leaf, leaf structure, leaf blade, petiole, leaf base, stipules; ways of attaching leaves: petiolate leaf, sessile leaf, moisture leaf; simple and compound leaves; dissected leaves: palmately lobed, palmately dissected, palmately divided, pinnately lobed, trichately lobed; leaf edge shapes: entire, serrated, serrate, prickly (prickly-toothed), crenate, pitted, sinuous; forms of leaf blades: oval, ovoid, lanceolate, sagittate, pinnately lobed, pinnately dissected, paired pinnate, unpaired pinnate, linear, ternary, palmate

Teacher's story with elements of conversation

Leaf blades can be classified in form. There are a huge number of forms of leaf blades: rounded, ovoid, linear, lanceolate, spear-shaped, sagittate, heart-shaped, oblong etc. Can be classified according to edge shape. In addition to leaves with a solid edge (they are called - whole-edge), There are several main types of edge shape: jagged, serrated, prickly (prickly-toothed), crenate, pitted, winding.

It should be noted that leaves of various shapes, sizes, and colors can be found on one shoot. This phenomenon is called heterophilia. Heterophilia is characteristic of buttercup, arrowhead and many other plants.

If you look at the leaf blade, you can see veins- bundles of conducting vessels. You saw them on the willow leaf. The arrangement of the veins on the leaf may be different. The way the veins are placed is called venation. There are several types of venation: parallel, arcuate, dichotomous, reticular (finger and pinnate).

Parallel, or arcuate, venation is characteristic of monocotyledonous plants, and reticulate - for dicotyledons.

Think about which plants are dicots.

What other signs of dicot plants do you know?

Give examples of monocots and dicots.

Consolidation of knowledge and skills Practical work 13. DETERMINATION OF SIMPLE AND COMPLEX LEAVES

Working process

Describe the herbarium leaf samples lying on your tables according to the plan.

Plan

What is the method of attaching this leaf to the stem?

What is leaf venation?

Is it a simple sheet or a complex one?

What is the shape of the leaf blade of this leaf?

What is the shape of the edge of the sheet?

2. What plant - monocotyledonous or dicotyledonous - does this leaf belong to?

3. Look at the picture. Write down the types of venation that the leaves shown in the figure have.

Leaf venation

4. Leaves simple and compound, their venation and leaf arrangement

Consider the proposed plant samples. Give a brief description of their leaves according to the plan, the name of the plant, simple or compound leaves, type of venation, type of leaf arrangement.

Creative task. Make a sheet print. To do this, you need a dried sheet (the leaves are dried in several layers of newspaper under pressure), gouache or watercolor paints, watercolor paper, a small paint roller. The sheet should be thickly smeared with watercolor or gouache paint and placed on watercolor paper. Top with blotting paper and roll. Compose a composition of prints of various leaves.

A task for students interested in biology. Using additional literature, pick up examples of plants with different types of leaf blades.

Manifoldleaves

Sheet. Kindsleaves. Release#2

Resources:

I.N. Ponomareva, O.A. Kornilov, V.S. Kuchmenko Biology: Grade 6: a textbook for students of educational institutions

Serebryakova T.I., Elenevsky A. G., Gulenkova M. A. et al. Biology. Plants, Bacteria, Fungi, Lichens. Trial textbook for grades 6-7 of high school

N.V. Preobrazhenskaya Biology workbook for the textbook by V. V. Pasechnik “Biology Grade 6. Bacteria, fungi, plants

V.V. Pasechnik. Manual for teachers of educational institutions Biology lessons. 5th-6th grades

Kalinina A.A. Lesson developments in biology Grade 6

Vakhrushev A.A., Rodygina O.A., Lovyagin S.N. Verification and control work to

textbook "Biology", 6th grade

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