The external structure of the sheet. Variety of leaves in shape and size. Variety of plant parts Subject: External structure of the leaf

Students know: What is a kidney; Kidney structure; What is an escape; The development of shoots from the kidneys; The location of the kidneys on the stem. Students can: Independently work with tables, diagrams, with additional literature; Find a connection between the structure and functions of organs; Formulate tasks, highlight the main thing, answer questions; Observe, analyze and draw conclusions; Work in groups and individually.

I. Organizational moment. II.Verification of homework. Test 4 “Escape. Its structure and functions ”(p.). III. Learning new material. The story of the teacher with elements of a multimedia lecture. (Theme, objectives, objectives of the lesson).

1 The leaf blade is an expanded part of the sheet. 2 Petiole is the narrow stem-like part of the leaf by which the leaf blade connects to the stem. 3Base base is the part by which the petiole is attached to the stem. 4 Stipules - located at the base of the leaf. 5 Veins - conductive vessels of the leaf (on the leaf plate)

The main vein runs in the middle, lateral, thinner ones depart from it (Lilac, nettle, linden, maple). Large veins run parallel to each other (cereals, reeds, sedge). Each vein, except for the central one, is curved like an arc (Plantain, lily of the valley). Dicotyledonous plants monocotyledonous plants

OBJECTIVES: To learn to distinguish between simple and complex leaves, to give a complete description of the leaves. EQUIPMENT: Herbaria of simple leaves with whole leaf blade and dissected leaves; various complex leaves (on each table). Definitive tables - memos.

PROGRESS OF WORK: 1. Describe the herbarium leaf samples lying on your tables according to the plan: What is the way to attach this sheet to the stem? What is leaf venation? Is it simple or complex? Which plant - monocotyledonous or dicotyledonous - belongs to this leaf? 2. Draw the external structure of the sheet in a notebook and sign the picture. Indicate the main parts of the sheet.

Name of the plants LEAFLINGING Biparticular Petioles Sedentary Simple Complex Arc Parallel 1. Rosehip 2. Mountain ash 3. Oak 4. Tradescence 5. Chestnut 6. Lupine 7. Birch 8. Lily of the valley 9. Strawberry 10 Reed 11. Aspen 12. Cuff 13. Sedge 14. Plantain Netted One-lobed

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

Sheet parts

A leaf is a lateral shoot organ that emerges from a kidney and attaches to the stem with a petiole. In the table “Characterization of the external structure of the leaves” each part is described in more detail.

Leaves with petioles are called petiolate. In the absence of 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 sheet has one leaf blade;
• complex - consist of several leaflets attached to a common petiole.

In autumn, simple leaves fall completely along with the petiole. An example is birch, elm, aspen. Complex leaves break up into leaves, and the common petiole is separated from the shoot. Examples are mountain ash, clover, dog rose.

By arrangement on a common petiole, complex leaves are divided into three types:

• cirrus - leaflets lie on the sides of the petiole; subdivided into paired ones - an even amount, each leaf has a pair, and unpaired ones - an odd amount, end with one leaf;
• palmate - leaves depart from the top of the petiole in different directions;
• ternary - consist of three leaves.

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

Variety of shapes

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

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

Fig. 1. Different forms of leaves.

The edges of the leaves are also diverse. Allocate:

• whole-edge (smooth);
• toothed;
• double toothed;
• serrated;
• small town;
• 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 of the leaf (birch);
• dissected - the recess does not reach the axis (oak);
• dissected - the recess reaches the center (potatoes).

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

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

Fig. 2. Leaf position.

Venation

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

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

Fig. 3. Types of venation.

What did we learn?

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

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the cloth

Where is located

Features of the structure of cells

Value

educational

Tops of stems
Root tips
Cambium
Wound

Small fissile cells without vacuoles

Plant growth

Coverslip

Epidermis (peel)
Bung
Bark

Living and dead cells with thick and strong shells, tightly adjacent to each other

Protection against adverse effects

Mechanical

Bast
Wood

Thick lignified shells

Reliance to plant organs

Conductive

Vessels of wood
Sieve tube bast

Sieve tubes

Distribution of substances entering the roots and formed in leaves throughout the body

Main

Leaf pulp
Stem core
Root

Chloroplasts in cells

The 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.
the cloth - a group of cells similar in structure and performing the same functions.

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

Xylem is the main water supply tissue of higher vascular plants, providing movement of water with mineral substances dissolved in it from the roots to the leaves and other parts of the plant (upward current). It also performs a supporting function. The xylem consists of tracheids and trachea (vessels) (Fig. 8.3), wood parenchyma and mechanical tissue.

Tracheids they are narrow, very elongated dead cells with pointed ends and lignified membranes. The penetration of solutions from one tracheid to another occurs by filtration through the pores - recesses tightened by the membrane. The fluid flows slowly through the tracheids, as the pore membrane inhibits the movement of water. Tracheids are found in all higher plants, and in most horsetails, plunders, ferns and gymnosperms serve as the only conductive element of xylem. Angiosperms have vessels along with tracheids.

Fig 8.3. Elements of xylem (a) and phloem (6): 1-5 - annular, spiral, staircase and porous (4, 5) trachea, respectively; 6 - piercing and porous tracheids; 7 - sieve tube with a companion cell.

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

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

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

Mechanical fabrics provide strength to plant organs. They constitute a framework that supports all plant organs, counteracting their fracture, compression, and rupture. The main characteristics of the structure of mechanical tissues, ensuring their strength and elasticity, are a powerful thickening and lignification of their membranes, close closure between cells, and the absence of perforations in the 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 walls, two types of mechanical tissue are distinguished: collenchyma and sclerenchyma (Fig. 8.4).

Fig. 8.4. Mechanical fabrics: a - angled collenchyma; 6 - sclerenchyma; at -- scleroids from the fruits of cherry plum: 1 - cytoplasm, 2 - thickened cell wall, 3 - pore tubules.

Collenheim represented by live parenchymal cells with unevenly thickened membranes, making them especially well adapted to strengthen young growing organs. Being primary, the cells of the collenchyma easily stretch and practically do not interfere with the lengthening of the part of the plant in which they are located. Typically, the collenchyma is located in separate strands or a continuous cylinder under the epidermis of the young stem and petioles of the leaves, and also borders the veins in the leaves of dicotyledons. Sometimes collenchyma contains chloroplasts.

Sklerenheim consists of elongated cells with uniformly thickened, often lignified membranes, the contents of which die off in the early stages. The shells of sclerenochemical cells have high strength close to the strength of steel. This tissue is widely represented in the vegetative organs of terrestrial plants and constitutes their axial support.

There are two types of sclerenchymal cells: fibers and scleroids.Fibers - These are long thin cells, usually collected in strands or bundles (for example, bast or wood fibers).Scleroids - these are rounded dead cells with very thick lignified membranes. They formed a seed peel, a shell of nuts, seeds of cherry, plum, apricot; they give the pulp of pears a characteristic coarse character.

Main fabric or parenchyma , consists of living, usually thin-walled cells that form the basis of organs (hence the name of the tissue). It contains mechanical, conductive and other permanent tissues. The main tissue performs a number of functions, in connection with which they distinguish between assimilation (chlorenchyma), storage, air-borne (aarenchyma) and aquiferous parenchyma (Fig. 8.5).

Fig 8.5. Parenchymal tissue: 1-3 - chlorophyll-bearing (columnar, spongy, and folded, respectively); 4-storing (cells with starch grains); 5 - airborne, or aerhenchyma.

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

In the cellsstocking up th parenchyma is deposited proteins, carbohydrates and other substances. It is well developed in the stems of woody plants, in root crops, tubers, bulbs, fruits and seeds. Plants of desert habitats (cacti) and solonchaks in stems and leaves haveaquifer parenchyma, which serves for the accumulation of water (for example, in large specimens of cacti from the genus Carnegia, tissues contain up to 2-3 thousand liters of water). Aquatic and bog plants develop a special type of main tissue -airborne parenchyma, oraerenchyma. Aeroenchyma cells form large air-borne intercellular spaces, through which air is delivered to those parts of the plant whose communication with the atmosphere is difficult

PLANT BODIES

BODY - it is a part of a plant that has a specific 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

Isolation of metabolic products into the soil

Nutrient storage

Synthesis of biologically active substances

Soil fixation

ROOT ZONES

ROOT ZONES AND VALUE

Protects the apex of the root from mechanical damage and ensures the promotion of the root in the soil.

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

The presence of root hairs, provides absorption by the roots of water and minerals dissolved in it.

The mediator between the root absorption zone and the aerial part of the plant, is located above the root by hairs. In this zone, conducting vessels and lateral roots are formed.

ROOT TYPES

TYPES OF ROOT SYSTEMS

1- The main root

corn

Side roots

All orchid

Swamp cypress, all swamp

Beetroot

Dahlia, Chistyak

The escape - this is the aerial part of the plant, consisting of the stem and the leaves and buds located on it.

Stem – axial elevated vegetative organ of the plant. Escape often performs the function of storing nutrients, vegetative propagation of plants and protecting them from eating. In such cases, it is modified.

STRUCTURE OF THE ESCAPE

Escape Variations

Reminds root. On it there are underdeveloped scaly leaves and buds, accessory roots grow from the nodes. In the rhizome are deposited for supply of nutrients. Most often, rhizome occurs in perennial cereals.

Examples: wheat grass, valerian, lily of the valley, streptocarpus.

An underground shoot on which the kidneys are located in the eyes. Tubers are underground aboveground. Tubers serve to propagate plants, store nutrients and tolerate adverse periods of the year. Under favorable conditions, tubers sprout easily and, thanks to stored substances, give beginning to young independent plants.

Example: potatoes, kohlrabi, gloxinia.

Tuber

Calla tubers

Dahlia tubers

Potato tubers

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

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

Onion Narcis

Spines

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

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

Mustache

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

Example: strawberries, strawberries.

Antennae

Curly shoots which, wrapping around different supports, support the stem in a certain position.

STEM

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

FEATURES:

Communicates all parts of a plant

Nutrient reserve

Vegetative propagation

Provides water transport of mineral and organic substances

Forms and carries kidneys and leaves

STEM TYPES AVAILABLE WOOD

Grassy

Woody

TYPES OF STEMS FOR PLACING IN SPACE

Climbing plants: field birch, bindweed

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

Clinging plants Chin, grapes, cucumber, pumpkin, tavern, melon.

Creeping: strawberries, strawberries.

INTERNAL STEM STRUCTURE

SHEET

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

LEAVES

Difficult - consisting of several leaf blades: strawberries - triple, mountain ash - unpaired pinnate, yellow acacia - paired pinnacle.

Simple - consisting of one leaf plate: linden, cherry, apricot, cereals.

Fig. 3.Simple leaves : 1 - needle; 2 - linear; 3 - oblong; 4 - lanceolate; 5 - oval; 6 - rounded; 7 - ovoid; 8 - obovate; 9 - rhombic; 10 - scapular; 11 - heart-ovoid; 12 - kidney; 13 - swept; 14 - spear-shaped : 1 - cirrus-complex; 2, 3 - ternary; 4 - palm-complex.

VEGETABLE -

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

The value of fall foliage

Plant health and protection against excessive evaporation in autumn and winter

Fallen leaves are an excellent mineral and organic fertilizer.

Prevention of freezing of roots and crumbled seeds

TYPES OF KIDNEYS

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

A - vegetative - stem growth to the top

B - vegetative-generative (reserve of vegetative propagation)

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

1 - an embryonic stem; 2- rudimentary scales; 3 - primordial flowers; 4 - conception leaves; 5 - rudimentary buds.

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

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

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

Fig. . Overhead modifications of shoots:

1 - stem succulent; 2 - a thorn; 3 - phyllocladium of the needle; 4 - a treasure trove of asparagus; 5 - a kidney of cabbage; 6 - stolons of strawberries; 7 - grape mustache; 8 - a shortened shoot of cherry; 9 - flower arrow of a dandelion.

Escape structure: SHEET:

Lesson Type - combined

Methodspartially search, problem statement, reproductive, explanatory and illustrative.

Purpose:

Students' awareness of the importance of all the issues discussed, the ability to build their relations with nature and society on the basis of respect for life, for all life as a unique and invaluable part of the biosphere;

Tasks:

Educational: 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 adaptations of living beings to the entire spectrum of environmental conditions.

Developing: to 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:

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

Building an understanding of the value of a healthy and safe lifestyle

Personal:

the 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) The formation of a holistic worldview, corresponding to the modern level of development of science and public practice.

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

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

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

Expected Results

Subjects:to know - the concepts of "habitat", "ecology", "environmental factors", their impact on living organisms, "the connection of living and nonliving" ;. To be able to - define the concept of "biotic factors"; characterize biotic factors, give examples.

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

Meta subject:.

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

The formation of semantic reading skills.

Form of organization of educational activity - individual, group

Teaching methods: visual-illustrative, explanatory-illustrative, partially-search, independent work with additional literature and a textbook, with the center.

Receptions:analysis, synthesis, inference, translation of information from one form to another, generalization.

Objectives: acquaint with the variety of leaves, the features of their external structure; to learn 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, herbaria of plants with various types of leaf blades, herbarium of willow leaf (for each desk).

Key words and concepts: leaf, leaf structure, leaf blade, petiole, leaf base, stipules; methods of leaf attachment: petiole, sessile, moisture-leaf; simple and complex leaves; dissected leaves: palmate-lobed, palmate-dissected, palmately divided, ciriform-lobed, tricolobate; forms of the edge of the sheet: solid, serrated, serrated, spiky (prickly-toothed), crusty, concave, sinuous; forms of leaf blades: oval, ovoid, spear-shaped, arrow-shaped, cirrus, cirrus dissected, paranoid, unpaired, linear, ternary, palmate

The story of the teacher with conversation elements

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

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

If you look at the leaf blade, you will notice veins - bundles of conducting vessels. You saw them on a willow leaf. The location of the veins on the sheet may be different. The method of vein placement is called venation. There are several types of venation: parallel, arched, dichotomous, reticular (palmate and cirrus).

Parallel, or arc, venation is characteristic of monocotyledonous plants, and reticular - for dicotyledons.

Remember which plants are dicotyledonous.

What other signs of dicotyledonous plants do you know?

Give examples of monocotyledonous and dicotyledonous plants.

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

Progress

Describe the herbarium leaf patterns on your tables according to plan.

Plan

What is the way to attach this leaf to the stem?

What is leaf venation?

Is it simple or complex?

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 - belongs to this leaf?

3. Review the drawing. Write down the types of venation that have the leaves shown in the figure.

Leaf venation

4. Leaves are simple and complex., venation and leaf arrangement

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

Creative task. Make a sheet print. To do this, a dried sheet is needed (the leaves are dried in several layers of the newspaper under the press), gouache or watercolor paints, ac-vare paper, a small paint roller. The sheet should be densely smeared with watercolor or gouache paint and put on watercolor paper. Cover with blotting paper from above and roll with a roller. Make a composition from prints of various leaves.

Task for students interested in biology. Using additional literature, select examples of plants with different types of leaf blades.

Manifoldleaves

Sheet. Viewsleaves. Release#2

Resources:

I.N. Ponomareva, O.A. Kornilov-va, V.S. KuchmenkoBiology: Grade 6: textbook for students of educational institutions

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

N.V. PreobrazhenskayaWorkbook on biology for the textbook In V. Pasechnik "Biology Grade 6. Bacteria, fungi, plants "

V.V. Beekeeper. A manual for teachers of educational institutions Biology lessons. Grades 5-6

Kalinina A.A. Class work in biology 6th grade

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

textbook "Biology", 6th grade

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