(Paper 1 Content Knowledge) 2.4 Organisation: Plant organ systems

Question 1

What are the two main plant transport tissues?

Answer 1

Xylem and phloem

Question 2

What does xylem transport?

Answer 2

Water and mineral ions from the roots to the rest of the plant.

Question 3

What does phloem transport?

Answer 3

Sugars (like glucose) and amino acids that are dissolved in water.

Question 4

How are xylem and phloem arranged in the root?

Answer 4

Xylem forms a central column with phloem around it – provides support.

Question 5

How are they arranged in the stem?

Answer 5

In vascular bundles containing xylem and phloem.

Question 6

What is the main organ of photosynthesis in plants?

Answer 6

The leaf

Question 7

How is a large surface area useful in a leaf?

Answer 7

It maximises light absorption and carbon dioxide intake for photosynthesis.

Question 8

Why is a leaf’s blade thin and flattened?

Answer 8

To reduce diffusion distance for water and gases.

Question 9

What is the function of vascular tissue in the leaf?

Answer 9

Xylem: brings water and minerals

Phloem: carries away glucose and other photosynthesis products

Question 10

Why are there air spaces in the leaf?

Answer 10

To allow gases to diffuse efficiently between cells.

Question 11

What is the main function of a leaf?

Answer 11

Photosynthesis and gas exchange

Question 12

Through what structure do gases enter and leave the leaf?

Answer 12

Through stomata

Question 13

What is the name of the process where water is lost from the leaf?

Answer 13

Transpiration

Question 14

What is the main role of the palisade mesophyll?

Answer 14

To absorb light for photosynthesis.

Question 15

How is the palisade mesophyll adapted for its function? (4 adaptations)

Answer 15

Packed with chloroplasts

Column-shaped cells

Arranged closely together

Located near the upper surface of the leaf

Question 16

What is the main role of the spongy mesophyll?

Answer 16

To allow efficient gas exchange.

Question 17

How is the spongy mesophyll adapted for gas exchange?

Answer 17

Loosely packed cells with air spaces

Thin layer of water on cells for gases to dissolve in

Question 18

Which gases are exchanged during photosynthesis?

Answer 18

Carbon dioxide in

Oxygen out

Question 19

What does the xylem transport?

Answer 19

Water and minerals from the roots to the leaves

Question 20

What type of process is transport in the xylem?

Answer 20

A physical process – it does not require energy

Question 21

What is the structure of xylem vessels?

Answer 21

Hollow tubes with no end walls

Strengthened with lignin

Dead cells

Question 22

What does lignin do in xylem vessels?

Answer 22

It provides strength and support; lignified xylem is also called wood

Question 23

What does the phloem transport?

Answer 23

Sugars and amino acids from photosynthesis (food substances)

Question 24

What is transport in the phloem called?

Answer 24

Translocation

Question 25

Is phloem transport passive or active?

Answer 25

It requires energy

Question 26

In which direction does phloem transport occur?

Answer 26

Up and down the plant

Question 27

What are sieve tubes?

Answer 27

Phloem cells with no nuclei and perforated end walls for cytoplasm to connect between cells

Question 28

What are companion cells?

Answer 28

Cells that provide energy for the active transport in sieve tubes; each sieve tube depends on its companion cell.

Question 29

Name two differences between xylem and phloem.

Answer 29

Xylem carries water and minerals; phloem carries sugars and amino acids Xylem transport is up only, passive; phloem transport is up and down, active

Question 30

What do plants need to transport to the leaves for photosynthesis?

Answer 30

Water, minerals, and carbon dioxide

Question 31

What happens to the products of photosynthesis in plants?

Answer 31

They are transported to where they are needed, such as growing parts and storage organs.

Question 32

How do small, simple plants like mosses absorb substances?

Answer 32

By diffusion and osmosis across their surface.

Question 33

Why don’t small plants need complex transport systems?

Answer 33

Substances don’t need to move far inside them; they have a large surface area compared to their volume.

Question 34

Why do larger plants need transport systems?

Answer 34

They do not have enough surface area to absorb all required substances by diffusion alone; their needs scale with volume.

Question 35

What is transpiration?

Answer 35

The evaporation of water from the mesophyll cells and its diffusion out of the leaf through stomata.

Question 36

Which cells does water evaporate from during transpiration?

Answer 36

The spongy mesophyll and palisade mesophyll cells.

Question 37

Through which structure does water leave the leaf?

Answer 37

The stomata.

Question 38

What replaces water lost from the leaves?

Answer 38

Water is drawn up through the xylem from the roots.

Question 39

Why does water form a continuous column in the xylem?

Answer 39

Because of cohesion between water molecules due to hydrogen bonding.

Question 40

What is the transpiration stream?

Answer 40

The continuous flow of water from roots to leaves, pulled up by evaporation from the leaves.

Question 41

Name four benefits of transpiration.

Answer 41

Provides water for photosynthesis Transports mineral ions Cools the leaf Maintains turgidity in plant cells

Question 42

What are root hairs?

Answer 42

Single-celled extensions of epidermal cells that absorb water and minerals.

Question 43

How does water enter root hair cells?

Answer 43

By osmosis, from soil water (higher water potential) into the cell (lower water potential).

Question 44

How do minerals enter root hair cells?

Answer 44

By active transport, using energy.

Question 45

What is transpiration rate?

Answer 45

The speed at which water evaporates from the leaf and diffuses out through the stomata.

Question 46

How does temperature affect transpiration?

Answer 46

Higher temperature increases evaporation, so transpiration increases.

Question 47

How does humidity affect transpiration?

Answer 47

Lower humidity increases transpiration, because it increases the concentration gradient for water vapour.

Question 48

How does air movement (wind) affect transpiration?

Answer 48

More air movement removes water vapour from around the leaf, increasing the rate of diffusion and transpiration.

Question 49

How does light intensity affect transpiration?

Answer 49

More light increases the number of open stomata, allowing more water to evaporate.

Question 50

Why do plants in different habitats have different transpiration adaptations?

Answer 50

To resist extremes in environmental factors like heat, wind, or low humidity.

Question 51

What is a simple way to measure transpiration in leaves?

Answer 51

Measure the change in mass of leaves over time.

Question 52

What are three variables that can affect water loss from leaves?

Answer 52

Air movement Temperature Whether the stomata are obstructed

Question 53

What is the purpose of applying petroleum jelly to leaves?

Answer 53

To block stomata and prevent water loss through transpiration.

Question 54

Why is the experiment repeated with several leaves?

Answer 54

To reduce the effect of natural variation and allow for a more reliable mean.

Question 55

How do you calculate the mean percentage decrease in mass?

Answer 55

Add all the percentage decreases and divide by the number of leaves.

Question 56

What is a potometer used to measure?

Answer 56

The rate of water uptake by a plant.

Question 57

What does water uptake by the plant indicate?

Answer 57

It is used as an estimate of the rate of transpiration.

Question 58

What does a basic potometer consist of?

Answer 58

A piece of capillary tubing connected to a plant shoot.

Question 59

How is water uptake measured using a potometer?

Answer 59

By timing how long it takes a bubble to move a set distance along the capillary tube.

Question 60

Why must the potometer be set up carefully?

Answer 60

To ensure no air leaks, and that the plant stem is sealed tightly for accurate results.

Question 61

Why is it important that the potometer is airtight?

Answer 61

To prevent loss of water other than through transpiration.

Question 62

Why is understanding transpiration important for agriculture?

Answer 62

Because insufficient water reduces crop yield.

Question 63

How does air movement affect transpiration?

Answer 63

It increases transpiration by removing humid air from around the leaf.

Question 64

How is air movement simulated in a lab?

Answer 64

By using a fan.

Question 65

What simulates pollution or coatings that block stomata in the lab?

Answer 65

Petroleum jelly smeared on the leaf surface.

Question 66

What is the effect of blocking stomata with petroleum jelly?

Answer 66

It reduces transpiration by preventing water loss through the stomata.

Question 67

How is high light intensity simulated?

Answer 67

By using artificial lighting.

Question 68

How does light intensity affect transpiration?

Answer 68

It increases transpiration by causing more stomata to open.

Question 69

How is high temperature simulated in a lab?

Answer 69

Using a heater or placing the plant in a greenhouse.

Question 70

How does temperature affect transpiration?

Answer 70

Higher temperatures increase evaporation from leaf surfaces, so transpiration increases.