Section 4: Gas Exchange in Plants

Question 1

Where are the upper and lower epidermis of a leaf cell?

Answer 1

They are the two outer layers

Question 2

What does the upper and lower epidermis have?

Answer 2

They have a few chloroplasts and have a thin waxy material called a cuticle on them.

Question 3

What is a cuticle?

Answer 3

A thin waxy layer on the upper and lower epidermis

Question 4

What does the cuticle do?

Answer 4

They stop water loss by evaporation and acts as a barrier for disease-causing microorganisms

Question 5

What is a stomata?

Answer 5

They are pores found on the lower epidermis

Question 6

What does the stomata do?

Answer 6

They allow CO2 to diffuse into the leaf - get to the photosynthetic tissue. It also allows oxygen and water vapor to diffuse out.

Question 7

How can guard cells control the stomata?

Answer 7

The stoma is in between two guard cells, these can open and close

Question 8

Where are the two layers of photosynthetic cells found?

Answer 8

In the middle of the leaf

Question 9

What is a mesophyll?

Answer 9

The two layers of photosynthetic cells

Question 10

Where is the palisade layer?

Answer 10

Below the upper epidermis

Question 11

What is the palisade layer made of?

Answer 11

They are made of elongated cells with hundreds of chloroplasts

Question 12

Where is the main site of photosynthesis?

Answer 12

In the palisade layer

Question 13

Why is the palisade layer effective in making chloroplast?

Answer 13

As they are close to the light source; the upper epidermis is relatively transparent

Question 14

What is below the palisade layer?

Answer 14

A spongy layer

Question 15

How are the cells organised in the spongy layer?

Answer 15

They are loosely packed with air spaces.

Question 16

Why does the cells of the spongy layer have air spaces in between them?

Answer 16

So that gas exchange can occur. The air spaces allow gas to diffuse in and out of the cells. The carbon dioxide is absorbed and oxygen and water is released.

Question 17

What are xylem?

Answer 17

A vessel that supplies water and mineral ions

Question 18

How is water transported in a plant?

Answer 18

Water is transported through the steam and veins in the leaves in the transpiration stream.

Question 19

How does water supply mesophyll cells in leaves?

Answer 19

Water leaves the xylem and supplies mesophyll cells

Question 20

What is the phloem?

Answer 20

It is a transport system that supplies products of photosynthesis, like sugars

Question 21

What parts does the phloem supply to?

Answer 21

Parts that do not photosynthesis

Question 22

What transport system do veins contain in leaves?

Answer 22

Both the xylem and phloem tissue

Question 23

What happens when light intensity increases?

Answer 23

Photosynthesis speeds up, but eventually levels off in very bright light. This causes a lack of CO2 near the leaves and a surplus of oxygen

Question 24

Describe the concentration of carbon dioxide around a leaf throughout the day?

Answer 24

In the middle of the day, there is a lack of carbon dioxide and lots of oxygen.
In the middle of the night, there is lots of carbon dioxide and a lack of oxygen.

Question 25

What solution is used to experiment on the sensitive changes in carbon dioxide concentration around a plant in a test tube?

Answer 25

Hydrogen Carbonate Indicator Solution