Plant tissues, organs and systems

Question 1

What are the layers of a plant leaf?

Answer 1

• waxy cuticle
• upper epidermis
• palisade mesophyll
• spongy mesophyll
• lower epidermis
• guard cells and stomata

Question 2

What does the waxy cuticle do?

Answer 2

Protective layer on top of the leaf, prevents water form evaporating

Question 3

What does the upper epidermis do?

Answer 3

Thin and transparent to allow light to enter palisade mesophyll layer underneath it

Question 4

What does the palisade mesophyll do?

Answer 4

Column shaped cells tightly packed with chloroplasts to absorb more light, maximizing photosynthesis

Question 5

What does the spongy mesophyll do?

Answer 5

Contains air spaces that increases the surface area to volume ration for the diffusion of gases

Question 6

What does the lower epidermis do?

Answer 6

Contains guard cells and stomata

Question 7

What do guard cells do?

Answer 7

Absorbs and loses water to open and close the stomata to allow carbon dioxide to diffuse in, oxygen to diffuse out

Question 8

What does the stomata?

Answer 8

Where gas exchange takes place ; opens during the day, closes during the night. Evaporation of water also takes place from here.
Reduces water loss

Question 9

What are the adaptations of the leaf? (5)

Answer 9

large surface area
thin
chlorophyll
stomata
waxy cuticle

Question 10

How do plants having a large surface area help it survive?

Answer 10

Increases surface area for the diffusion of carbon dioxide and absorption of light for photosynthesis

Question 11

How do plants being thin help it survive?

Answer 11

Allows carbon dioxide to diffuse to palisade mesophyll cells quickly

Question 12

How do plants having chlorophyll help it survive?

Answer 12

Absorbs light energy so that photosynthesis can take place

Question 13

How do plants having stomata help it survive?

Answer 13

Allows carbon dioxide to diffuse into the leaf and oxygen to diffuse out

Question 14

How do plants having waxy cuticle help it survive?

Answer 14

Protects leaf without blocking sunlight

Question 15

How are root hair cells specialised and what do they do? (4)

Answer 15

Absorb water/minerals for plants
- Large permanent vacuole - speeds up movement of water by osmosis from soil across root hair cell - maintain potential gradient

• Have many mitochondria that transfer the energy needed for active transport of mineral ions into root hair cells
• Thin walls = short diffusion distance

Question 16

How are xylem cells specialised and what do they do? (4)

Answer 16

Transports water and mineral ions from the roots to the highest leaves/shoots.
Supports plant
- Alive when the first form but lignin build up in spirals in the cell walls. Cells die and form long hollow tubes - allow water/mineral ions to move through them easily
- Rings of lignin make them strong and help them withstand the pressure of water moving up.

Question 17

How are phloem cells specialised and what do they do? (4)

Answer 17

Carries the food made by photosynthesis around the body of the plant

• Made of phloem cells that form hollow tubes
• Lose a lot of their internal structure but they are supported by companion cells
• Companion cells have mitochondria that transfer energy

Question 18

What is meristem tissue?

Answer 18

Found at the growing tips of shoots and roots, can DIFFERENTIATE into different types of plant cell, allows plant to GROW

Question 19

Factors affecting transpiration: (4)

Answer 19

Light intensity
Temperature
Air flow
Humidity

Question 20

How does light intensity affect transpiration?

Answer 20

Brighter the light, the higher transpiration rate
The stomata close as it gets dark, photosynthesis can’t happen in the dark, so they don’t need to let CO2 in, very little water can escape.
High light, stomata stays open to allow co2 in.

Question 21

What is transpiration?

Answer 21

The evaporation of water at the surfaces of the spongy mesophyll cells in leaves, followed by loss of water vapour through the stomata

Question 22

How does temperature affect transpiration?

Answer 22

Warmer, faster transpiration

When it is warm the water particles have more energy to evaporate and diffuse out of the stomata

Question 23

How does air flow affect transpiration?

Answer 23

better the air flow, faster the transpiration
Water vapour is swept away maintaining a low concentration of water in the air outside the leaf. Diffusion happens quickly

Question 24

How does humidity affect transpiration?

Answer 24

Drier the air, faster transpiration

Lots of water in the air, not much of a difference between inside and outside the leaf so diffusion happens slower

Question 25

What is translocation?

Answer 25

Movement of food/sugars from the leaves to the rest of the plant, goes in both directions

Question 26

When do guard cells and stomata become turgid?

Answer 26

In the light, the guard cells absorb water by osmosis , become turgid and the stoma opens. In the dark, the guard cells lose water, become flaccid and the stoma closes.