Plant tissues, organs and systems (2.3) (M)

Question 1

What type of organ is the leaf?

Answer 1

a plant organ

Question 2

That the roots, stem and leaves work together in an (…) that (…) substances.

Answer 2

organ system

transports

Question 3

5 needed

What are the tissues of the leaf?

Answer 3

• upper and lower epidermal tissues
• palisade mesophyll
• spongy mesophyll
• xylem and phloem
• meristem tissue found at the growing tips of shoots and roots

Question 4

What are guard cells?

Answer 4

specialised cells which control the opening and closing of the stomata to enable gaseous exchange

this may allow CO₂ to enter for more/a greater rate of photosynthesis

Question 5

What does the palisade mesophyll contain and how is it adapted to function?

Answer 5

That the palisade mesophyll contains palisade cells.

It is the site for photosynthesis and the cells have a large number of chloroplasts (containing much chlorophyll so is adapted to absorb as much light as possible.

Question 6

What does the spongy mesophyll contain and how is it adapted to function?

Answer 6

That the spongy mesophyll has air spaces to create a large surface area for more efficient/greater gas exchange

Question 7

Where is the meristem tissue found and what can it do?

Answer 7

That meristem tissue is found at the tips of the growing regions of plants and can differentiate into different types of plant cell.

Question 8

Label a leaf?

Answer 8

sunlight shines on upper epidermis

Question 9

The phloem and xylem are often found in what?

Answer 9

they are often found together in vascular bundles (veins you can see on leaf)

Question 10

What is translocation?

Answer 10

the transport of dissolved food (e.g. sucrose, a sugar) from the leaves to other parts of the plant

Question 11

Where does translocation occur?

Answer 11

the phloem

Question 12

How is the phloem adapted to function?

Answer 12

Phloem is composed of tubes of elongated cells.

• Cell sap can move from one phloem cell to the next through pores (sieve plates) in the end walls
• have companion cells (containing many mitochondria for energy) to enable the dissolved food to be transported and pass through sieve plates

Question 13

What does the xylem do?

Answer 13

transports water (transpiration stream - uninterrupted from roots to leaves) and minerals from roots to leaves

Question 14

2 ways

How is the xylem adapted to function?

Answer 14

• Made up of hollow continuous tubes of dead cells with no end (cell) walls so water can be transported quickly through the cell
• Strengthened by spirals of waterproof lignin - will not absorb water (as made up of dead cells, it needs strengthening)

Question 15

What does water do to a cell?

Answer 15

Keeps it turgid (not flaccid)

Question 16

What are factors that increase the rate of transpiration?

Answer 16

• higher light intensity
• higher temperature
• increased airflow
• lower humidity

Question 17

How does an increased temperature affect the rate of transpiration? How?

Answer 17

increases it

increases molecular movement so that more water molecules evaporate from cell surfaces

there is increased movement of water molecules by osmosis from the leaf to outside of the leaf increases; so more evaporation of water from the stomata

Question 18

How does an increased humidity affect the rate of transpiration? How?

Answer 18

decreases it

More concentrated solution in leaf, so decreased movement of water molecules by osmosis from the leaf to outside of the leaf (more dilute solution) decreases as the air contains more water molecules (is more dilute), so less water loss as less water is evaporated from the stomata

Question 19

How does increased airflow affect the rate of transpiration? How?

Answer 19

increases it

Removes water vapour from leaf surfaces, so increased movement of water molecules by osmosis from the leaf (more dilute solution) to outside of the leaf (more concentrated solution) increases, so increased evaporation from stomata

Question 20

How does increased light intensity affect the rate of transpiration? How?

Answer 20

increases it

The stomata open wider to allow more carbon dioxide into the leaf for photosynthesis

so increased movement of water molecules by osmosis from the leaf (more dilute solution) to outside of the leaf (more concentrated solution) increases, thus more evaporation from stomata so more water loss

Question 21

What is a potometer used to do?

Answer 21

to investigate the rate of water uptake by a plant

Question 22

What is the waxy cuticle? What does it do?

Answer 22

A waxy waterproof layer which reduces water loss, it is transparent to allow light through the leaf

Also locks air flow across leaf’s surface - so decreases rate of transpiration

Question 23

When light intensity is high, potassium ions are moved into guard cells.

How does increased light intensity cause increased transpiration?

Answer 23

potassium ions make the cell more concentrated

water moves into the guard cell by osmosis

cells swell unevenly

as inner wall less flexible than outer wall

This can be applied to any situation relating to increased osmosis into the cell - make sure you understand this

Question 24

Suggest why leaves took in oxygen during the dark

Answer 24

oxygen used in aerobic respiration

Question 25

What is the advantage to the plant of the stomata’s width changing over a ten hour period?

Answer 25

reduces rate of transpiration

reduces wilting

Question 26

The lower surfaces of the leaf were covered in grease, explain why there was no water loss after this

Answer 26

lower surface has most stomata

stomata now blocked by grease

so water cannot escape/evaporate from the stomata

Question 27

What is transpiration?

Answer 27

Loss of water due to evaporation from the stomata

Question 28

What is the transpiration stream?

Answer 28

The movement of water molecules from roots to the leaves in the xylem

Water evaporates via the stomata in the leaf tissue

Question 29

2 marker

How does water move from roots to leaves?

Answer 29

By transpiration stream in xylem

Question 30

2 marks

A plant has very few stomata on the upper surface of the leaf - how is this an advantage to the plant?

Answer 30

less water lost

do does not wilt

Question 31

How is the volume of water lost from the leaves controlled?

Answer 31

By the opening and closing of stomata

Question 32

4 marks

Why do plants need two different methods to absorb water (osmosis) and ions (active transport)?

Answer 32

solution in the soil is more dilute

so water moves from dilute to more concentrated region/solution

concentration of ions less (than that in root hair cells)

so energy need to move ions or ions are moved against concentration gradient

Question 33

What is the function of the stomata?

Answer 33

(it opens and closes) to allow carbon dioxide to enter and oxygen to leave (i.e. to enable gaseous exchange)

Question 34

What are three environmental factors that could have increased the rate of transpiration?

Answer 34

• It was warmer
• It was windier
• It was less humid
• or there was more water (vapour) in the leaves