"Green Plants and the Water Cycle of the Biosphere" PPT Courseware 4

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"Green Plants and the Water Cycle of the Biosphere" PPT Courseware 4

Information: Someone calculated that a corn plant consumes more than 200 kilograms of water during its lifetime from emergence to fruiting. Only about 2.2 kilograms of this water is used as a component of the corn plant and participates in various physiological processes. Where did the rest of the water go? What significance does this water have to the plants themselves and the natural world?

1. Plants’ absorption of water

Plants absorb water primarily through their roots. The main part of the root that absorbs water is the mature zone at the root tip. There are a large number of root hairs in the mature zone, which gives the root tip a huge absorption area and therefore a strong water absorption capacity.

Characteristics of roots suitable for absorbing water:

The main part of the root that absorbs water is the mature area of ​​the root tip, which has a large number of root hairs.

Characteristics of root hair cells: thin cell wall, less cytoplasm, and large vacuoles.

A large number of root hairs can increase the absorption area and improve the efficiency of roots in absorbing water.

2. Transpiration of plants

Cover a vigorously growing potted plant with a clear, dry plastic bag and tie it tightly around the stem. Put it in the sun and observe what happens on the inner wall of the plastic bag? What does it mean?

Transpiration:

The process by which water is lost as water vapor from the surface of living plants into the atmosphere

The significance of plant transpiration

1. Promote the absorption and upward transport of water and inorganic salts by plants,

2. Transpiration can increase atmospheric humidity, increase precipitation, and participate in the water cycle of the biosphere.

3. Transpiration can also lower the temperature of plants.

4. Green plants stabilize nature’s water cycle.

3. The water cycle of the biosphere

The role of green plants in the water cycle:

1. The transpiration of green plants can increase the humidity of the atmosphere and increase precipitation;

2. The stems and leaves of plants absorb rainwater and can greatly slow down the erosion of the ground by rainwater;

3. Litter leaves in the woods can absorb a large amount of rainwater, seep into the ground, and replenish groundwater.

Discussion: If there were no green plants on Earth, would the water cycle continue?

Without green plants, the water cycle can still take place. Water vapor evaporated from oceans and lakes enters the atmosphere and forms clouds, which then form rain and snow, and then return to the ocean or land. But without green plants, the water cycle in the biosphere will be affected to a certain extent. For example, rainfall on land will decrease; surface runoff caused by rainfall will increase and speed up, etc.

practise

1. Determine whether the following statements are correct or not. If the statement is correct, draw “” and if the statement is incorrect, draw “”.

(1) Plants lose a lot of water through transpiration, which is a waste. ( )

(2) The stomata of plants are very small, so very little water is lost through the stomata. ( )

(3) In plants, water flows to higher places, which is mainly driven by transpiration. ( )

2. When planting trees in spring, a large number of branches and leaves are often cut off from transplanted saplings. Why is this?

Because the leaves will lose a lot of water through transpiration, causing the saplings to die due to lack of water, a large number of branches and leaves need to be pruned.

When planting plants, choose evening or rainy days.

Why?

Answer: Reduce transpiration and increase survival rate.

3: Take two branches of the same plant and label them A and B respectively. Leave the leaves on branch A and remove the leaves on branch B. Then insert them into two measuring cylinders of the same size containing equal amounts of water. Add a drop of oil in the middle and let the oil droplets cover the water surface. Place the two devices in the same environment for 24 hours and observe the changes in the liquid level in the measuring cylinder.

(1) What is the function of dropping oil drops in a measuring cylinder?

Prevent water from evaporating directly from the measuring cylinder

(2) What difference will appear in the liquid levels in the two measuring cylinders? Reason for the difference?

The liquid level in graduated cylinder A drops higher than that in graduated cylinder B. The reason for this difference is that the blades of A are lost through transpiration.

Class exercises

(1)The structure of leaves is composed of _____,_____,_____.

(2) Stomata is the gateway through which plants lose water and is also the window for ______ exchange. It is a cavity surrounded by a pair of half-moon-shaped _____ cells. The shape of ______ cells can be adjusted, and the stomata can both _____ and _______.

(3) The cell wall thickness of guard cells is uneven. The cell wall close to the stomatal cavity is difficult to stretch; the cell wall far away from the stomatal cavity is easier to stretch. When the guard cells absorb water and expand, the stomata are called stomata; when the guard cells shrink when they lose water, the stomata are called stomata.

(4) Plants participate in the water cycle of the biosphere through ________.

Keywords: Green Plants and the Biosphere's Water Cycle Teaching Courseware, People's Education Edition 7th Grade Biology PPT Courseware Download, Seventh Grade Biology Slide Courseware Download, Green Plants and the Biosphere's Water Cycle PPT Courseware Download, .PPT format;

For more information about the "Water Cycle of Green Plants and Biosphere" PPT courseware, please click the "Water Cycle of Green Plants and Biosphere" ppt tag.

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Update Time: 2024-10-19

This template belongs to biology courseware People's Education Edition seventh grade biology volume 1 industry PPT template

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