Organisation in Plants

Question 1

Why are leaves considered organs?

Answer 1

They have many tissues working together to perform photosynthesis

Question 2

What does the waxy cuticle do?

Answer 2

Make the leaf waterproof

Question 3

Where is the waxy cuticle?

Answer 3

Very top layer of the leaf

Question 4

Where and what is the upper epidermis?

Answer 4

A single layer of cells under the waxy cuticle

Question 5

What does the upper epidermis do?

Answer 5

Protects against water loss

Question 6

Where and what is the palisade mesophyll?

Answer 6

A layer of tightly packed cells under the upper epidermis

Question 7

Name an adaptation of the upper epidermis.

Answer 7

Transparent to allow light through

Question 8

Name an adaptation of the palisade mesophyll.

Answer 8

Lots of chloroplasts to absorb light for photosynthesis

Question 9

Where and what is the spongy mesophyll?

Answer 9

A layer of spherical cells under the palisade mesophyll

Question 10

What does the spongy mesophyll do?

Answer 10

Allow for gas exchange

Question 11

Name an adaptation of the spongy mesophyll.

Answer 11

Air spaces for quick diffusion, large SA:V ratio to increase gas exchange

Question 12

Where is the lower epidermis?

Answer 12

The bottom layers of the cell

Question 13

What do guard cells do?

Answer 13

Control the opening and closing of the stomata

Question 14

What is the stomata?

Answer 14

Tiny openings on the lower surface of the leaf

Question 15

What does the stomata do?

Answer 15

Allow gases to diffuse in and out of the leaf

Question 16

Where are the stomata and guard cells located?

Answer 16

In the lower epidermis

Question 17

From top to bottom, what is the order of the structure of a leaf?

Answer 17

1. Upper epidermis
2. Palisade mesophyll
3. Spongy mesophyll
4. Lower epidermis

Question 18

What gas does the stomata let into the plant?

Answer 18

Carbon dioxide

Question 19

What gas does the stomata let out of the plant?

Answer 19

Oxygen

Question 20

What do the stomata help control?

Answer 20

Gas exchange and water loss

Question 21

What happens when a plant has lots of water?

Answer 21

The stomata become turgid

Question 22

What happens when the stomata become turgid?

Answer 22

They open up - the inner surface of the stomata curve away from each other

Question 23

What is transpiration?

Answer 23

The evaporation and movement of water away from the plant’s leaves through the xylem.

Question 24

What is the transpiration stream?

Answer 24

The constant movement of water up the plant (through the xylem vessels)

Question 25

How is water lost by the stomata?

Answer 25

Evaporation

Question 26

Name 2 reasons why transpiration is important.

Answer 26

1. Provides water to cells to keep them turgid 2. Provides water to cells for photosynthesis 3. Transports mineral ions to leaves

Question 27

What is translocation?

Answer 27

The movement of dissolved sugars from the leaves to the rest of the plant through the *phloem*.

Question 28

What is the movement of transpiration like?

Answer 28

Only *one way*

Question 29

What is transported in transpiration?

Answer 29

Water and minerals

Question 30

What does lignin do?

Answer 30

Stiffen the walls of the xylem

Question 31

What is different between the phloem and xylem?

Answer 31

1. Phloem has end walls; xylem has no end walls. 2. Phloem transports water and dissolved sugars; xylem transports water and minerals. 3. Phloem transports substances in two directions; xylem only one direction.

Question 32

What direction do substances travel in the phloem?

Answer 32

Both - up and down

Question 33

What are the end walls of the phloem like?

Answer 33

They have small holes to allow substances to flow through

Question 34

What does the phloem transport?

Answer 34

Water and dissolved sugars

Question 35

What effect does temperature have on transpiration?

Answer 35

Higher temp. -> higher rate of transpiration

Question 36

Why does increased temperature increase the rate of transpiration?

Answer 36

Water evaporates faster in high temperatures

Question 37

What effect does humidity have on transpiration?

Answer 37

Lower humidity -> higher rate of transpiration

Question 38

Why does decreased humidity increase the rate of transpiration?

Answer 38

Drier air -> steeper concentration gradient of water molecules between the air and leaf

Question 39

What affect does wind have on transpiration rate?

Answer 39

More wind -> higher rate of transpiration

Question 40

Why does increased wind increase the rate of transpiration?

Answer 40

Wind removes the water vapour quickly, so maintains the steeper concentration gradient

Question 41

What effect does light intensity have on transpiration rate?

Answer 41

Higher light intensity -> increased rate of transpiration

Question 42

Why does increased light intensity increase the rate of transpiration?

Answer 42

Stomata open wider to let more carbon dioxide into the leaf (for photosynthesis)

Question 43

What do root hair cells do?

Answer 43

Increase absorption of water and mineral ions into the root

Question 44

How do root hair cells increase absorption of water and mineral ions into the root?

Answer 44

By increasing the surface area

Question 45

Name an adaptation of root hair cells.

Answer 45

Lots of mitochondria -> energy transfer -> used to take in mineral ions via active transport