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P Topic: “External structure of the leaf” Prepared by: biology teacher of the MBOU “Romodanovskaya Secondary School No. 2” Lidiya Nikolaevna Elizarova

Lesson objectives: 1. Introduce the variety of leaves, develop morphological concepts. 2. Develop the ability to make comparisons, draw conclusions, identify common and distinctive features of simple and complex leaves.

Problem task The leaves of different plants are not similar to each other. Some plants have large leaves, while others are very tiny. Victoria regia - leaf diameter 2.2 m Duckweed has the smallest floating leaves Raffia palm has a leaf 20 m long

Hypothesis: Leaves of different plants have similar and distinctive characteristics

Task No. 1 1. Look at the drawing “External structure of a leaf.” Learn what main parts a sheet consists of. 2. Find the main parts of the leaf on the herbarium. 3. Do all leaves have a petiole? Look at the pictures in the appendix. What are these leaves called? 3.Complete task 33 in your workbook. 4.Draw a conclusion.

Conclusion: A leaf consists of a leaf blade with veins and a base. Leaves can be petiolate or sessile.

Task No. 2 1. Using knowledge about the external structure of the leaf, compare the herbarium leaves under No. 1 and No. 2. What is the difference? 2. Find in the appendix the definition of “simple leaves”, “complex leaves”. 3. Complete exercise 36 in your workbook. 4. Draw a conclusion.

Conclusion: A leaf consisting of one leaf blade and one petiole is called simple. A leaf consisting of several leaf blades connected to a common stalk by small petioles is called compound.

Variety of leaves

Task No. 3 Get acquainted with the shapes of the leaf blade of simple and complex leaves. 2. Answer the questions: 1) What shape of the leaf blade is characteristic of simple leaves? 2) What shape of the leaf blade is characteristic of compound leaves? 3. Determine the shape of the leaf blade of herbarium leaves No. 1 and No. 2. Write it down in your notebook.

Conclusion: Plants differ from each other in different shapes of leaf blades, which is important for identifying plants.

Task No. 4 1. Look at the drawing. 2. What types of venation are distinguished? 3. Fill out the diagram: (in your notebook) Type of venation 4. Determine the type of venation of the leaves of herbarium No. 1 and No. 2. Write it down in your notebook. 5. Draw a conclusion.

Venation type: Cirrus

Conclusion: The following types of venation are distinguished: parallel, reticulate (finger, pinnate), arcuate. This is an important feature when identifying plants.

The leaves of different plants are similar in external structure. Leaves have distinctive features that help identify plants by species.

Functions of the sheet 1) The sheet provides light capture. 2) Leaf ensures the formation of organic substances. 3) The leaf provides breathing. 4) The leaf evaporates water, protecting the plants from overheating. 5) The leaf can provide protection (modified leaves-spines have this role).

Thank you very much for your attention

According to the textbook:

I.N. Ponomareva

I.V. Nikolaev

O.A. Kornilova

Leaf, its structure and meaning

Chemistry and Biology Teacher

MKOU BSOSH No. 2 Bredy village

Ushkareva V.Ya.

Remember

1- leaf blade;

2- veins;

3- petiole;

4- stipules;

5- leaf base.

DIFFICULT

SIMPLE LEAVES HAVE A LEAF BLAME

COMPOUND LEAVES HAVE SEVERAL LEAF PLATES

Variety of leaves

simple leaves : 1- lilac, 2- apple tree, 3- maple, 4- dandelion.

Compound Leaves : 5- clover, 6- rosehip, 7- raspberry, 8- strawberry, 9- lupine.

Do you know that…

Leaf venation

1- parallel (wheat); 2- arc (lily of the valley);

3-pinnate (apple tree)

Leaf arrangement

In the rough elm and in many other plants

Each node has only one leaf.

This - another leaf arrangement.

Snowberry has two leaves at each node.

This is an opposite arrangement of leaves.

Bedstraws have leaves arranged in

each node has several (4–10 in different species).

This is a whorled leaf arrangement.

Sheet mosaic

Participation of stomata in gas exchange

and evaporation of water.

Do you know that ……

Stomata are found in the skin of all land plants. Their number in plants is enormous - from 80 to 300 pieces or more per 1 mm of leaf surface. For example, in maple, per 1mm of leaf surface there is

In most plants, stomata are located predominantly on the underside of the leaf, but in some (for example, eucalyptus, cabbage) they are located on both sides. In plants with leaves floating on water, stomata formed only on the upper side of the leaf, facing the airy side.

Sheet value

for plants

Sheet - specialized

shoot organ containing

cells that capture

sunlight needed

to implement

air supply

(PHOTOSYNTHESIS)

Evaporation of water

The stomatal fissure is surrounded by a pair of cells,

which are able to change their shape.

When the stomata closes it stops

evaporation of water from the intercellular spaces of the leaf.

At the same time, gas exchange also stops.

Factors affecting stomatal function

Environmental factors

Dry air

Water supply conditions

Light brightness

Temperature

Internal environmental factors

Water supply to leaf cells. When there is a water deficit in leaf tissues, the stomata close

Gas exchange

Leaf fall

Flying off the branch

gold coins

Autumn leaves

Reduction of the surface of above-ground organs in winter

Fallen leaves, rotting, participate in the formation of soil.

Leaf fall

Reduced evaporating surface

Removing accumulated products

A-leaf tendrils

B- fleshy leaves

3- sedum,

4-youthful)

Leaf modifications

A barberry shoot with leaf spines (left). Transition of a leaf to a barberry spine (right)

Leaves of some plants -

predators are capable of movement.

Hey, brother mosquito, watch out!

Don't sit on her bush -

I'll have to with my life

say goodbye.

Once you sit down, again

don't get up.

Nepenthes, or pitcher plant, has

modified leaves in the form of a pitcher to catch insects

Pemphigus vulgare

Among the thread-like green leaves there are modified ones that have the shape of trapping bubbles (2-5 mm in diameter) with a cap. Small insects trapped in them, for example, daphnia, are chemically processed in the bubble to a liquid state, and then digested.

• The leaf is an important organ of the plant. The functions of the leaf are varied: photosynthesis, gas exchange, evaporation, removal of waste products, storage of nutrients and water. The external and internal structure of the leaf determines the performance of certain functions. Acquiring new functions, the sheet changes.

• Sheet
• Leaf blade
• petiole
• Veins
• Stoma
• Gas exchange
• Evaporation
• Photosynthesis
• Leaf fall
• Leaf modification

• Describe the relationship between the internal structure of a leaf and its main function.
• What is the importance of leaf fall in the life of a plant?
• Give examples of plants with modified leaves.
• What is the importance of shelterbelts in the fight against drought?

External structure of the leaf Completed by Akimova N.A. Biology and Chemistry Teacher, Voloshovskaya Secondary School

Answers to the test Option 1 A 1 – 3 A 2 – 2 A 3 – 1 A 4 - 1 Option 2 A 1 – 4 A 2 – 2 A 3 – 3 A 4 – 3

Are all leaves the same in appearance? How do the leaves differ from each other? What do their structures have in common?

What does life on Earth depend on? Why do plants have such a powerful, huge crown?

What are the main functions of a leaf? evaporation photosynthesis respiration

Leaf structure leaf blade petiole leaf base

Petiolate leaf

Leaf sessile

Shapes of the leaf blade 1. Broadly ovate leaf 2. Round 3. Inversely broadly ovate 4. Ovate 5. Elliptic 6. Obovate 7. Narrow ovate 8. Lanceolate 9. Oblong 10. Inversely narrow ovoid 11. Linear

Shape of leaf blade edge

Simple leaves Compound leaves

Types of leaf venation Veins are conductive bundles of leaves

Plant characteristics dicotyledonous monocotyledons number of cotyledons two one root system taproot fibrous leaf venation reticulate arcuate, parallel

Exception Plantain Crow's Eye

name of the plant leaves simple or compound Venation leaf arrangement dicotyledonous or monocotyledonous Laboratory work “Leaves are simple and compound, their venation and leaf arrangement”

Line 1 – one noun expressing the main theme of the syncwine. Line 2 – two adjectives expressing the main idea. Line 3 – three verbs describing actions within the topic. Line 4 is a phrase that carries a certain meaning. Line 5 – conclusion in the form of a noun (association with the first word). syncwine

I stretch out my earthly hands from the sun - little rays I collect every day doing important work What is this riddle about?

Lesson topic: “External structure of the leaf. Leaf modifications. Leaf fall."

The purpose of the lesson: study the external structure of a leaf, the diversity of leaves, modifications of leaves and their functions, form an idea of ​​the phenomenon of leaf fall and its significance.

The smallest leaves aquatic plant – Duckweed (in diameter 2-3mm)

Record holder for largest leaves Victoria amazonica (up to 2m in diameter)

External leaf structure .

sheet

Leafy

plate

petiole

Main part

extended part,

attaching

sheet

plate to node

stem

leaf,

having a flat

form

Leaves can be:

leaves

Petiolate

sedentary

Leaves

Complex – on a common petiole several

leaf blades

Simple –

if on the petiole

one leaf

plate

Compound Leaves there are :

Complex

leaves

Trifoliate

Palmate compound

Pinnately

Pairi-pinnately compound

Imparipinnate

Vascular-fibrous bundles connecting the leaf to the stem - veins

Arrangement of veins in

leaf blade - venation

Venation

arc

mesh

parallel

Leaf arrangement – a certain order of arrangement leaves on a stem.

Leaf arrangement:

• Next
• Opposite
• Whorled

Leaf modifications

What functions does a leaf perform?

1. Fleshy leaves (Agave)

Function – water supply

2. Thorns (cacti)

Function – reduce water evaporation

spines

Barberry performs a protective function

3. Mustaches (peas)

Function – support the stem in a certain position

4. Scales (bulb onions)

dry (protection)

Scales

juicy

(stock

nutritious

substances)

5. Trap leaves Insectivorous plants

Sundew

“Leaves are traps” Venus flytrap

"Jug" Nepenthes

Plants

Evergreens

Deciduous

• leaves live for several months;
• leaves are shed en masse;

• leaves live for several years;
• retain leaves all year round;
• fall off gradually

External structure of a leaf 1. Get acquainted with the variety of leaves, the features of their external structure; 2. Learn to recognize leaves by types of venation, shape of the leaf blade, shape of the edge, location on the stem, distinguish between simple and complex leaves. 3. Get an idea of ​​the cellular structure of a leaf, the connection between the structural features of cells and their functions.

Simple leaves Whole leaves consist of an entire leaf blade or have shallow grooves (lilac, birch, apple, poplar). Lobed leaves have cutouts no more than 1/4 of the leaf width (maple). Separated leaves have cutouts more than 1/4 of the leaf width (dandelion). Dissected leaves have cuts reaching the midrib (wormwood, tansy, chamomile). Types of leaves

Compound leaves Trifoliate leaves have three leaf blades (clover, strawberry). Palmate leaves consist of several leaf blades emerging from one point (lupine, horse chestnut). Pinnately compound leaves have leaflets attached along the entire length of the petiole in two rows. The imparipinnate ones end with one leaf (rowan, raspberry, rose hip), the paripirpinnate ones end with a pair of leaflets (peas, yellow acacia). Types of leaves

Venation in plants is a system of bundles in leaf blades through which substances are transported. Plants of the Dicotyledonous class are characterized by pinnate and palmate venation. Plants of the Monocot class are characterized by arcuate and parallel venation