Presentation of the research paper “Why do leaves fall from trees in autumn? Leaves present.ppt - Presentation on the topic: research work "Why do leaves change color and fall off" Presentation on why leaves turn yellow and fall off.

The leaf is green because it contains the green coloring substance chlorophyll. The leaf is green because it contains the green coloring substance chlorophyll. Chlorophyll is quickly destroyed and quickly restored, but only under the influence of sunlight. Therefore, the leaf is always fresh and green in summer. In autumn, the days become shorter, the daylight hours decrease and chlorophyll does not have time to recover due to lack of light. The leaf turns pale and other coloring substances appear on it, which give the leaf a different color: yellow, orange, crimson tones. Chlorophyll is quickly destroyed and quickly restored, but only under the influence of sunlight. Therefore, the leaf is always fresh and green in summer. In autumn, the days become shorter, the daylight hours decrease and chlorophyll does not have time to recover due to lack of light. The leaf turns pale and other coloring substances appear on it, which give the leaf a different color: yellow, orange, crimson tones.

References 1. Viktorov D.P. A brief dictionary of botanical terms. - M.-L.: Science, - 177 p. 2. Goryshina T.K. Plant ecology. – M.: Higher. school, s. 3. Elenevsky A.G., Solovyova M.P., Tikhomirov V.N. Botany. 4. Taxonomy of higher or terrestrial plants. – M.: Academy, p. 5. Zhukovsky P.M. Botany. – M.: Kolos, – 623 p.

Research plan: Chapter 1: Introduction Chapter 2: Main part. Study. 1. Study of leaf structure. 2. Study of the role of leaves in the life of a plant. 3. Study of the causes of leaf fall. 4. Folk signs associated with changes in leaf color. Chapter 3: Conclusion.

CHAPTER 1. Introduction. Autumn is a wonderful time of year. At this time of year, our whole family loves to be in the forest: wandering through the autumn forest, breathing fresh air, observing nature, collecting bouquets of fallen leaves, admiring the yellow, orange, crimson, purple colors. One day while walking, I noticed on a branch of a tree different colored leaves: yellow and green. And I asked my mother: why were the leaves all green in the summer, but in the fall they turn yellow? And my mother and I decided to reveal this secret.

CHAPTER 2. Main part. Study. 2.1. Study of leaf structure. Leaf - consists of a leaf blade and a petiole. A mesh is visible on the leaf blade. The mesh is the vessels through which water and nutrients move. But if we look into the middle of the leaf, we will see that each leaf is full of wonderful grains. 2.2 Studying the role of leaves in the life of a plant. *Why do leaves need grains? *What is the role of wonderful grains, because they are so small that they cannot be seen?

Each leaf is full of wonderful grains. The grains are so small that you can't see them. They prepare food for the tree. The roots of the tree suck water from the ground. Many substances needed by plants are dissolved in this water. Green grains take the necessary substances from the air and water and build new branches, leaves, trunk and roots. But most importantly, they need sunlight for such work. From morning to evening they catch the sun's rays. In addition to green grains, there are also others in the leaves - yellow ones. While the green grains were working, the yellow ones were not visible, but the green ones dissolved - and only the yellow ones remained. The leaves have turned yellow. They gradually dry out and fall off. And you can’t leave the leaves for the winter - then such snowdrifts will grow on the branches that the branches can’t stand it and will break. Each leaf is full of wonderful grains. The grains are so small that you can't see them. They prepare food for the tree. The roots of the tree suck water from the ground. Many substances needed by plants are dissolved in this water. Green grains take the necessary substances from the air and water and build new branches, leaves, trunk and roots. But most importantly, they need sunlight for such work. From morning to evening they catch the sun's rays. In addition to green grains, there are also others in the leaves - yellow ones. While the green grains were working, the yellow ones were not visible, but the green ones dissolved - and only the yellow ones remained. The leaves have turned yellow. They gradually dry out and fall off. And you can’t leave the leaves for the winter - then such snowdrifts will grow on the branches that the branches can’t stand it and will break.

2.3 Studying the causes of leaf fall Why do leaves fall? Over the summer, a thin partition grows between the stem of the leaf and the twig. It does not allow juice or water to pass through. A partition will grow and separate the leaf from the branch. So even in calm weather there is leaf fall in our forest.

2.4 Folk signs associated with changes in leaf color. People have been observing nature for a long time, noticing everything that happens around them. And among the people there appeared signs associated with changes in the color of leaves. Although the leaf has turned yellow, it falls off weakly - frost will not come soon. If in the fall the birch leaves begin to turn yellow from the top, then the next spring will be early, and if from below, then it will be late. Yellow leaves will appear on the trees untimely - by early autumn.

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Project Why leaves turn yellow and fall off 2B grade students
Votintseva Veronica

Tree leaves bloom in spring

Why are the leaves green?

The leaves are green because of the green pigment - Chlorophyll.
Without chlorophyll, trees cannot receive
nutrients.
Thanks to the green pigment, photosynthesis occurs -
process of producing oxygen from carbon dioxide
to the world
In addition to nutrition through the roots, the tree receives glucose,
which is produced in green leaves in the light

Therefore, leaves are very important for trees.
Without leaves, the tree could die in the summer. Leaves
very important for the tree!

The leaf contains not only one green pigment - Chlorophyll, but also several more
pigment substances – Xanthophyll, Carotene, Anthocyanin.
In spring and summer, under the influence of sunlight, Chlorophyll predominates, and therefore
green leaves

Chlorophyll - green

With the arrival of autumn, the number of sunny days decreases

The days are getting shorter and the temperature is dropping.
Chlorophyll production in leaves is reduced and slowly disappears.
With its disappearance, other pigments become visible.

Xanthophyll – Yellow
Carotene – Orange
Anthocyanin - Red

Thanks to this we enjoy such a variety of colors

Why do trees shed their leaves?

In summer, trees store nutrients through their leaves.
substances. In summer, a large amount of vapor evaporates through the leaves of the tree.
the amount of moisture that is then replenished from the soil or
from the atmosphere.
In winter, a tree needs to save moisture, since it can take it from
soil or from the air is much more difficult. Leaves for winter
trees become not only unnecessary, but also harmful.
Therefore, in the fall, the tree releases unnecessary substances to its leaves.
and resets them.
If the tree did not shed its leaves, it would simply
frozen.

Research
Research
Why do the leaves change?
Why do the leaves change?
color and fall off?
color and fall off?
I've done the work:
Student 3 "B" class MBOU
Secondary school No. 18
Martynov Yaroslav
Project Manager:
teacher classes
Kovalenko L.A.

Find out the reason for the change
leaf colors in autumn.
1. Conduct a theoretical
study.
2. Establish a relationship
between shifts
climatic conditions and
change in leaf color.
3. Find out what trees are for
dropping leaves.

The leaves turn yellow and fall off because
 Leaves turn yellow and fall off because
that the temperature is dropping,
that the temperature is dropping,
the amount of sunlight decreases
light and wood, due to
light and wood, due to
cooling of the soil stops
cooling of the soil stops
get moisture.
get moisture.

This topic
interested us
for a long time. Every autumn
going out into the forest,
we admired
the beauty of nature and
asked the question:
"Why leaves
change their color
and then completely
fall off?
And we decided
find out the reason.

In autumn, our body prepares for winter and the onset of
He is not afraid of cold weather.
Not only a person, but also all living things on the sly
preparing for the cold weather.
Bears and badgers store more fat for winter.
It is accumulated by bats and mosquitoes. In the body
many insects have a special appearance in the fall
frost-resistant substance.
Trees also have to withstand severe
frosts. How do they deal with this? After all, trees are not
can, like squirrels and partridges, huddle together for warmth
heap, they cannot, like wood grouse, bury themselves in the snow to
escape from the frost.
But they are also preparing for winter in advance.

It turns out that yellow paint is always in the leaves.
Only in summer the yellow color is invisible.
It becomes clogged with a stronger one – green.
The green color of the leaves is given by a special substance – chlorophyll.
Chlorophyll in a living leaf is constantly destroyed and re-formed.
But this only happens in the light.
In summer the days are very long and the plants get a lot of sun
Sveta.
At this time, photosynthesis is actively occurring in the leaves of plants,
Chlorophyll is constantly produced.
Chlorophyll cells are constantly being destroyed and restored,
since they undergo the most important decomposition processes for plants
carbon dioxide into water and oxygen, and the formation of carbohydrates.
In summer, the formation of chlorophyll does not lag behind its destruction, so
the leaf remains green all the time.

In autumn, the leaves turn not only yellow, but also red,
crimson, violet. It depends on what coloring matter
is found in a withering leaf.
The leaves of any plant species contain many pigments,
the main ones, in addition to the chlorophyll we know, are:
carotene (provitamin A) – it is what gives a rich, bright color
carrots, pumpkin, sea buckthorn berries. It comes in yellow and red.
anthocyanin is a purple-red pigment that gives beets a special color and
red cabbage.
Another element that is directly related to the formation of color
leaves is auxin. It nourishes the cells located in the area
attaching leaf cuttings to a branch.
In autumn, the release of auxin stops, all connecting channels
between the leaf and the branch are blocked, and the flow of nutrients
the sheet stops.
The breakdown of chlorophyll cells occurs, and their number
is rapidly decreasing.
But carotene is not removed, and the leaves remain colored
brown, red and other dark and light red colors.

If autumn is long,
rainy - coloring
foliage from excess water and
there will be a lack of light
dull, inexpressive.
If the nights are cold
alternate with clear
on sunny days, then
the colors will match
weather - juicy, bright.

Behind the appearance of autumn coloring
leaf fall begins. Deciduousness
- adaptive property of plants. IN
cold climate is an adaptation to
frosty winter, hot - to
withstanding the heat, which allows
endure drought.
Autumn coloring of leaves, and then
leaf fall, on various trees and shrubs
do not start at the same time. Significant
habitat influences this
plants. In the same plants
watershed, slope, narrow valley,
valley this happens at different times.
Different levels of illumination affect
and air temperature. Influenced
and soil moisture: on dry soils
autumn colors appear earlier.

Probably everyone has noticed that the more red or yellow the
the leaf, the easier it breaks. And now the moment comes when it’s worth
just touch the leaf, and it immediately falls from the branch along with
petiole. Just yesterday, even a strong wind could not tear off the leaves, but
Now they fall off on their own.
It turns out that in the fall, things also happen in the leaf petioles.
changes.
In summer, the leaf petioles are firmly attached to the branches. Rip off
green leaf from tree is very difficult. It's easier to tear than separate
from the branch without any damage.
What happened?
It turns out that in the fall at the base of the petiole, in the place where it
attaches to the branch, a so-called cork layer appears. He,
like a partition, separated the petiole from the branch. Now only a few
thin fibers connect the leaf petiole to the branch. Even mild
a breath of wind breaks these fibers. Leaves are falling.

Leaf fall diagram
Leaf fall diagram
Cork formation
layer and buds
Formation of separation
layer
Leaf fall
Bud formation for the winter

Leaf fall
Leaf fall

Leaf fall algorithm
Leaf fall algorithm
chlorophyll is destroyed in the leaves,
the leaf accumulates unnecessary substances,
appears between the leaf and stem
separation layer,
leaf changes color
the leaf turns brown
the sheet comes off
the leaf falls.

Although our deciduous trees live for tens and hundreds of years, their leaves
“work” for only one season. And during this time they still wear out quickly.
After all, the “work” of leaves is very intense.
In a green leaf, the entire lower surface is covered with transparent skin,
dotted with small holes - stomata. Under the influence of the environment
temperature and air humidity, they open and close.
The water that the root absorbs from the soil rises along the trunk to the branches and
leaves. When the stomata are open, moisture evaporates from the leaves, and new portions
water is drawn through the trunk into the crown.
Trees need a lot of water. Over the summer, a large birch tree, for example,
evaporates about 7 tons of water. In winter you won’t get as much moisture from the soil. Losing
leaves and trees are protected from “winter drought”.
In some cities, trees have to change their leaves twice a year. There are also
another reason for leaf fall: to protect thin fragile tree branches from
the severity of the fallen snow.
Leaf fall adapts trees to winter.

Elvira Sabirzyanova

"Why do leaves turn yellow and fall off?"On a walk in the fall, the children collected colorful fallen leaves. They came up to me and asked: - “Elvira Nailievna, and why did the leaves turn yellow and fall off?"What do they need me for? answered: - "Let's find out together."

From this our work began to boil.

We searched in books, in the library, on the Internet.

They sculpted, drew, played various educational games,

I would like to find out in more detail why leaves turn yellow and fall off. At the autumn festival we made various crafts from beautiful autumn leaves. After the guys learned more about leaves, began to draw their conclusions. And they assumed leaves turn yellow and fall off. because they lack solar heat and light, because in the fall it gets dark earlier than in the summer and the sun no longer warms so much, but just shines. Leaves be afraid of the cold and the wind and because of this they fall. The children were very interested in looking for the answer to their question.

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