Text C Biology 9.2 Gas Exchange in Plants

Question 1

What is the primary function of stomata in plants?

Answer 1

Allow gases to diffuse in and out of the leaf

Stomata are small openings on the leaf surface that facilitate gas exchange.

Question 2

How do gases move in and out of plant cells? What is the name of the general process?

Answer 2

By passive transport, specifically diffusion

Gases like carbon dioxide, oxygen, and water vapour move through intercellular spaces.

Question 3

What gases are found in the air we breathe?

Answer 3

Oxygen, carbon dioxide, water vapour, nitrogen, and other gases

The composition of inhaled and exhaled air differs significantly.

Question 4

What changes occur to oxygen and carbon dioxide levels during cellular respiration?

Answer 4

Oxygen levels decrease and carbon dioxide levels increase

Body cells consume oxygen and produce carbon dioxide as waste.

Question 5

What is the main gas exchange organ in plants?

Answer 5

The leaf

Leaves are specialized for gas exchange, primarily through stomata.

Question 6

What happens to carbon dioxide when it enters a leaf?

Answer 6

It dissolves into the watery film around the cells and diffuses into the cells

Chloroplasts use carbon dioxide for photosynthesis.

Question 7

What is produced during photosynthesis?

Answer 7

Oxygen

Oxygen is a byproduct of photosynthesis, while carbon dioxide and water are consumed.

Question 8

How do lenticels contribute to gas exchange in woody plants?

Answer 8

They allow air to diffuse through the bark

Lenticels are lens-shaped openings in the bark that facilitate gas exchange.

Question 9

Fill in the blank: Air enters the leaf through _______.

Answer 9

stomata

Question 10

True or False: Plants consume more carbon dioxide during photosynthesis than they produce during cellular respiration.

Answer 10

True

Photosynthesis results in a net consumption of carbon dioxide.

Question 11

What are the two types of tissue cells mentioned in the leaf where gas exchange occurs?

Answer 11

Spongy and palisade tissue cells

These cells create spaces for gas circulation within the leaf.

Question 12

What is the role of xylem in leaves?

Answer 12

Transport water and minerals

Xylem carries water from the roots to the leaves.

Question 13

What is the role of phloem in leaves?

Answer 13

Transport sugar out of the leaf

Phloem distributes the products of photosynthesis throughout the plant.

Question 14

How does water exit the leaf?

Answer 14

As vapour through the stomata

Water vapor exits during transpiration, which also aids in cooling the plant.

Question 15

What prevents gas exchange in woody plants?

Answer 15

Layers of dead cork cells and waxy substances

These layers block direct gas exchange with living cells.

Question 16

What effect does the evaporation of water have on temperature?

Answer 16

Cooling effect

Evaporation cools the environment, which is why organisms like humans and dogs perspire or pant to regulate body temperature.

Question 17

What is transpiration?

Answer 17

Evaporation of water from leaves

Transpiration is a process by which plants lose water, which can cool the leaf significantly.

Question 18

How much can transpiration cool a leaf?

Answer 18

10 to 15°C below surrounding air temperature

This cooling effect helps prevent heat damage to the plant.

Question 19

How much water does an average-sized maple tree lose per hour due to transpiration?

Answer 19

200 L

This significant loss of water highlights the need for the tree to absorb more water from the soil.

Question 20

What percentage of water absorbed by a tree is lost through transpiration?

Answer 20

90 percent

This indicates that a tree must take up much more water to sustain both transpiration and photosynthesis.

Question 21

What are the two types of tissue cells in leaves that are involved in gas exchange?

Answer 21

Palisade and spongy tissue cells

These cells are important for photosynthesis and gas exchange in plants.

Question 22

What role do guard cells play in the stomata?

Answer 22

Control the opening and closing of stomata

This regulation is crucial for managing gas exchange and water loss.

Question 23

What happens to gas exchange when the stomata are open?

Answer 23

Carbon dioxide enters and oxygen and water vapor exit

Open stomata allow for high rates of photosynthesis.

Question 24

What happens to photosynthesis when stomata are closed?

Answer 24

Less photosynthesis occurs

Closing stomata reduces the exchange of gases, impacting the plant’s ability to perform photosynthesis.

Question 25

Fill in the blank: The evaporation of water from leaves is called _______.

Answer 25

transpiration ## Footnote Transpiration is essential for cooling plants and facilitating gas exchange.

Question 26

True or False: Plants can lose as much as 99 percent of the water absorbed by their roots through transpiration.

Answer 26

True ## Footnote This highlights the efficiency of water use and the necessity for plants to manage their water resources carefully.

Question 27

What determines the opening and closing of the stomata?

Answer 27

The amount of water in the guard cells ## Footnote Water moves into and out of the guard cells by osmosis.

Question 28

What happens to guard cells when water moves into them?

Answer 28

They swell due to increased water pressure ## Footnote This increased pressure is called turgor pressure.

Question 29

What is turgor pressure?

Answer 29

The high water pressure inside guard cells that pushes against the cell wall ## Footnote Turgor pressure is crucial for the opening of stomata.

Question 30

What is the effect of transpiration on water loss from plants?

Answer 30

It causes water to be lost from the plant's cells ## Footnote Water vapor passes out of the leaf through transpiration.

Question 31

What happens to guard cells when the amount of water decreases?

Answer 31

They deflate and change shape, closing the stoma ## Footnote This action prevents further water loss.

Question 32

How do stomata function in most plants during the day?

Answer 32

They open during the day and close at night ## Footnote This pattern helps with photosynthesis and water conservation.

Question 33

How do desert plants adapt their stomata to their environment?

Answer 33

They only open their stomata at night ## Footnote This adaptation helps conserve water during the day.

Question 34

What happens to plants when their water source is depleted?

Answer 34

The leaves droop and wither, and the stem softens and bends ## Footnote This is a result of reduced turgor pressure in plant cells.

Question 35

What causes plant cells to wilt?

Answer 35

Reduced turgor pressure due to water loss ## Footnote Limp cells can regain shape and rigidity if supplied with water.

Question 36

What is the role of turgor pressure in plant cells?

Answer 36

It acts as a plant's 'skeleton' to maintain shape and rigidity ## Footnote High turgor pressure is necessary for non-woody plants to stay upright.

Question 37

True or False: During droughts, non-turgid guard cells keep the stomata open.

Answer 37

False ## Footnote Non-turgid guard cells keep the stomata closed to reduce water loss.

Question 38

What is a consequence of closed stomata during droughts for plants?

Answer 38

Plants photosynthesize less due to reduced carbon dioxide intake ## Footnote This is one reason crop yields are lower during droughts.

Question 39

Fill in the blank: Water stops diffusing into the cell when the cell's _______ reaches an upper limit.

Answer 39

turgor pressure ## Footnote This limit is set by the cell wall in plant cells.

Question 40

How do plant and animal cells respond to continued inflow of water by osmosis?

Answer 40

Plant cells have a limit due to the cell wall, while animal cells may burst ## Footnote Plant cells maintain turgor pressure, while animal cells do not have a rigid structure.

Question 41

What is the range of stomata per cm² on the lower epidermis of a leaf?

Answer 41

10,000 to 100,000 stomata per cm²

Question 42

How many stomata would be present on a leaf with a surface area of 10 cm² and an average of 50,000 stomata per cm²?

Answer 42

500,000 stomata

Question 43

How many guard cells would be associated with the stomata?

Answer 43

Equal to the number of stomata, 500,000 guard cells

Question 44

What gases diffuse through the leaf via stomata?

Answer 44

Carbon dioxide, oxygen, and water vapour

Question 45

What process do plants undergo that consumes carbon dioxide and produces oxygen?

Answer 45

Photosynthesis

Question 46

What is the term for water evaporation from leaves?

Answer 46

Transpiration

Question 47

What regulates the size of stomata to control gas exchange?

Answer 47

Guard cells

Question 48

What pressure in guard cells regulates the opening and closing of stomata?

Answer 48

Turgor pressure

Question 49

What happens to stomata when transpiration is high?

Answer 49

Stomata close to minimize gas exchange and conserve water

Question 50

Fill in the blank: During cellular respiration, plant cells consume _______ and produce carbon dioxide and water.

Answer 50

Oxygen

Question 51

Fill in the blank: The cells of some plant stems are surrounded by a protective layer of _______ or waxy material.

Answer 51

Cork

Question 52

True or False: Plants do not require oxygen.

Answer 52

False

Question 53

What could you design to test the effect of a range of water temperatures on the amount of photosynthesis in an aquatic plant?

Answer 53

An experiment

Question 54

Describe how the cells of stems exchange gases across the protective layer.

Answer 54

Through diffusion or specialized structures

Question 55

Which gases are consumed and produced during cellular respiration?

Answer 55

Consume oxygen; produce carbon dioxide and water