Transpiration

Question 1

What is transpiration?

Answer 1

Transpiration is the loss of water vapor from the surface of leaves.

Question 2

Explain the process of transpiration. (3)

Answer 2

• Water is pulled up the xylem in the stem from the roots to the leaves.
• The water is used for photosynthesis and to stop the plant from wilting
• Water evaporates from the leaves into the air.

Question 3

As water is used up or lost from the leaves more is sucked up from the ______ vessels. It’s a bit like sucking up water up a straw. So there is a continuous flow of water from the _____ to the ______. This movement of water up the xylem is called the _______ ________.

Answer 3

Xylem
Roots
Leaves
Transpiration stream

Question 4

Explain transpiration within the mesophyll layer?

Answer 4

• Water first evaporates from the spongy cells into the air spaces.
• The air space become full of water vapor.
• Water vapor diffuses through the stomata into the air.
• The water lost from the spongy cells is replaced by more water from the xylem.

Question 5

Why does more transpiration take place during the day than at night?

Answer 5

Stomata are open during the day but close at night.

Question 6

Stomata May also close in very _____ conditions. This is because the water lost in ________ is not being replaced by water from the soil. The stomata close to _____ transpiration.

Answer 6

Dry
Transpiration
Reduce

Question 7

What happens if the plant doesn’t get enough water?

Answer 7

It will start to wilt. It’s cells have lost so much water that they are no longer turgid or full of water.

Question 8

Turgid cells are ____ and give the plant support.

Answer 8

Firm

Question 9

What happens when cells become flaccid?

Answer 9

The plant becomes soft and the stem is no longer upright and the leaves droop.

Question 10

What are the environmental factors which affect transpiration?(4)

Answer 10

Wind
Humidity
Temperature
Light

Question 11

How do windy conditions affect the rate of transpiration?

Answer 11

Transpiration increases the rate of transpiration. Water molecules are blown away from the lead surface, so more diffuse out of the stomata.

Question 12

How does humidity affect transpiration?

Answer 12

They decrease the rate of transpiration. The air contains a lot of water already.

Question 13

How does temperature affect temperature?

Answer 13

Warm conditions increase the rate of transpiration. The air can hold more water vapor.

Question 14

How does light affect transpiration?

Answer 14

Light causes the stomata to open. This increases the rate of transpiration.

Question 15

How do you measure the rate of water uptake?

Answer 15

Using a potometer

Question 16

Why is the amount of water lost actually less than the amount of water taken in by the roots?

Answer 16

Most of the water is used up in photosynthesis.

Question 17

How does transpiration help with the pulling of water ?

Answer 17

As water evaporates through the stomata in the leaves, it creates a negative pressure (tension or suction) in th leaves and tissues of the xylem. The negative pressure exerts a pulling force on the water in the plant’s xylem and draws the water upward.

Question 18

How does cohesion help with drawing water?

Answer 18

When water molecules stick to one another through cohesion, they fill the column in the xylem and act as a single molecule of water.

Question 19

Capillary action is the movement of a liquid across the surface of a solid caused by _____ between the two. When you place a tube in water, water ________ moves up the sides of the tube because of adhesion, even before you apply sucking force.

Answer 19

Adhesion

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