3.3

Question 1

What is dicotyledonous plants?

Answer 1

Plants with two seed leaves and a branching pattern of veins

Question 2

What is meristem?

Answer 2

A layer of dividing cell called the pericycle

Question 3

What is phloem?

Answer 3

Transports dissolved assimilates

Question 4

What is vascular tissue?

Answer 4

Consists of cells specialised for transporting fluids by mass flow

Question 5

What is a xylem?

Answer 5

Transports water and minerals

Question 6

Why do plants need a transport system?

Answer 6

• Water and minerals from roots up to the leaves

- Sugars from leaves to rest of plant

Question 7

What are the two Vascular tissue?

Answer 7

• Water and soluble moves up in xylem tissue

- Assimilates travel up or down the phloem

Question 8

What are companion cells?

Answer 8

Cells that help load sucrose into sieve tubes

Question 9

What are seive tube elements?

Answer 9

Make up tubes in phloem tissue that carry sap up and down plants.

Sieve tube separated by sieve plates

Question 10

What are the adaptations of xylem to its function?

Answer 10

• Dead cells aligned end to end form continuous column.
• Tubes are narrow so water column does not break easily
• Bordered pits in lignified walls allow water to move sideways
• Lignin deposited in patterns allowing stretching of plant

Question 11

Structure of sieve tube elements

Answer 11

• No nucleus and little cytoplasm

- Perforated cross walls creating sieve plates

Question 12

Structure of companion cells

Answer 12

• Large nucleus
• Dense cytoplasm
• Mitochondria to produce ATP
• Load assimilates

Question 13

What is plasmodesmata?

Answer 13

Gaps in cell wall containing cytoplasm that connects cells

Question 14

What is the apoplast pathway?

Answer 14

• Water passes through space between cell walls and cells.

- Mass flow

Question 15

What is the symplast pathway?

Answer 15

Water enters cell via cytoplasm and passes through plasmodesmata

Question 16

What is vaculor pathway?

Answer 16

• Not confined to cytoplasm.

- Passes through vacuole

Question 17

What is water potential?

Answer 17

Tendency of water molecules to move from one place to another

Question 18

What is transpiration?

Answer 18

Loss of water from arial parts of plant

Question 19

What is a potometer?

Answer 19

A device that can measure rate of water uptake

Question 20

Why is transpiration important?

Answer 20

• Transports useful mineral ions up the plant
• Maintains cell turgidity
• Supplies water for growth, cell elongation and photosynthesis
• Supples water as it evaporates keep plant cool

Question 21

Precautions to ensure potometer experiment results are valid?

Answer 21

Set up under water to ensure no air bubbles enter xylem

Shoot is healthy

Leaves are dry

Cut stem at angle to ensure large surface area

Question 22

What is adhesion?

Answer 22

Attraction between water molecules and walls of xylem vessel

Question 23

What is cohesion?

Answer 23

Attraction between water molecules causes by hydrogen bonds

Question 24

What is role of Casparian strip?

Answer 24

Blocks apoplast pathway.

Question 25

What is the role of endodermis?

Answer 25

• Movement of water across root using active processes
  Endodermis sometimes called starch sheath
• Casparian strip blocks apoplast pathway between medulla and cortex, ensuring water and mineral ions pass via cytoplasm
• Plasma protein has transporter proteins actively pump in mineral ions into xylem and root medulla

Question 26

What is root pressure?

Answer 26

• Pressure in root medulla builds up forcing water into xylem

Question 27

What is transpiration pull?

Answer 27

• Water attracted to each other by cohesion
• Strong enough to hold water in continuous column
• Molecules lost at top of column tension created pulling column of water upwards

Question 28

What is capillary action?

Answer 28

• Adhesion forces pull water up xylem

Question 29

What is a hydrophyte?

Answer 29

A plant adapted to living in water or where the ground is very wet

Question 30

What is a xerophyte?

Answer 30

A plant adapted to living in dry conditions

Question 31

Adaptations of marram grass?

Answer 31

• Leaf is rolled longitudinally so air can be trapped inside making humid, reducing water loss from leaf
• Waxy cuticle layer to reduce evaporation
• Stomata on inner inner side
• Stomata in pits in lower epidermis folded and covered by hairs, reduce air movement and therefore loss through water vapour
• Spongy mesophyll is dense with few air spaces, less surface area for evaporation of water

Question 32

Adaptation of cacti?

Answer 32

• Succulents -> store water in stems which are fleshy and swollen
• Leaves are reduced to spines to reduce surface area reducing transpiration
• Stem is green for photosynthesis
• Roots are widespread

Question 33

Other xerophytic features?

Answer 33

• High salt concentration to reduce water potential
• Long roots
• Closing stomata

Question 34

What are adaptations of hydrophytes?

Answer 34

• Many large air spaces in leaf, keeping leaf afloat to access sunlight and air
• Stomata are on upper epidermis
• Leaf stem has large air spaces helping buoyancy and also allowing oxygen to diffuse quickly into roots

Question 35

What is translocation?

Answer 35

Transport of assimilates through a plant

Question 36

What occurs during active loading?

Answer 36

• Hydrogen ions actively pumped out of companion cell
• Concentration gradient created
• Hydrogen ions diffuse back in via co transport protein alongside a sucrose molecule
• Concentration of sucrose increases in companion cell causing it to diffuse into sieve tube

Question 37

What causes movement of sucrose?

Answer 37

• Mass flow
• Flow caused by difference in hydrostatic pressure producing pressure gradient
• Water enters increasing pressure