B4 - (Part 2) Organising Plants

Question 1

Examples of plant organs

Answer 1

• Leaf
• Stem
• Roots
• Flower

Question 2

Function of the upper and lower epidermis (epidermal tissue)

Answer 2

• Protects the surface of the leaf
• Upper epidermis is transparent to allow light through for photosynthesis

Question 3

Function of the waxy cuticle

Answer 3

Reduces the evaporation of water from the surface of the leaf preventing it from drying out

Question 4

Function of the palisade mesophyll

Answer 4

Contains palisade cells which absorb the sunlight needed for photosynthesis as they have lots of chlorophyll

Question 5

Function of the spongy mesophyll

Answer 5

Has air spaces to allow for rapid diffusion of CO2 for photosynthesis and rapid diffusion of O2 to be removed

Question 6

Function of the xylem

Answer 6

• Transports water and mineral ions
• From the roots to the leaves (up only)

Question 7

Function of the phloem

Answer 7

• Transports dissolved sugars produced by photosynthesis
• From the leaves to the rest of the plant (up + down)

Question 8

What is meristem tissue

Answer 8

• Found at shoots and roots
• Contains stem cells which can differentiate into any type of plant tissue

Question 9

What is translocation

Answer 9

The movement of sugars and other dissolved molecules through phloem tissue

Question 10

How to tell the difference between xylem and phloem in a diagram

Answer 10

• Xylem is always at the top or in the middle
• Phloem is always at the bottom or outside

Question 11

What is transpiration and what are its two stages

Answer 11

• The loss of water vapour from the surface of the leaf
• First stage is evaporation from spongy mesopyll
• Second is diffusion through stomata

Question 12

Describe the transpiration stream

Answer 12

• Evaporation of water from leaf cells
• Water vapour diffuses through spongy mesophyll air spaces
• Diffuses out of leaf through stomata
• Water goes from xylem to leaf to replace lost water
• Water taken in by roots trhough xylem to leaf

Question 13

What is important about the transporation stream (3)

Answer 13

• Brings water to the leaf needed for photosynthesis
• Brings mineral ions such as magnesium (chlorophyll)
• Cools the leaf down

Question 14

Factors that affect the rate of transpiration

Answer 14

• Temperature
• Humidity
• Wind
• Light intensity

Question 15

Optimum conditions for maximum transpiration

Answer 15

• High temp - more evaporation
• Not humid - faster evaporation when dry
• Very windy - removes water vapour allowing more to evaporate
• High light intensity - stomata open for CO2 for photosynthesis and water vapour can get out

Question 16

Adaptations of the root hair cells

Answer 16

• Hairs - increase SA so more water an mineral ions absorbed
• Do not have chloroplasts - are underground
• Lots of mitochondria - provide energy for active transport

Question 17

Structure and adaptations of xylem

Answer 17

• Thick walls containing lignin - provide strucuture + causes cells to die
• No end walls of cell - forms a long hollow tube
• No internal organelles

Question 18

Structure and adaptations of phloem

Answer 18

• Vessel cell with sieve plates - allow dissolved sugars to flow through
• Companion cells with mitochondria - provide energy

Question 19

Function of stomata and guard cells

Answer 19

• Control gas exchange and water loss

Close when it is too hot and at night

Question 20

Important ions that plants need

Answer 20

• Nitrates - protein synthesis
• Magnesium - to make chlorpyhll