Transport In Plants

Question 1

Name the main tissues dicotyledonous plants (8)

Answer 1

Epidermis

Cortex; collenchyma and parenchyma

Vascular bundle; sclerenchyma fibres, phloem, cambium, xylem

Parenchyma (pith)

Question 2

Parenchyma (3)

Answer 2

Parenchyma cells, forms pith

Storage of glucose molecules

Secretion of carbohydrates

Question 3

Epidermis (4)

Answer 3

Outer layer of cell

Guard cells; form stomata that regulate water intake

Waxy cuticle; reduces water loss

Could contain trichomes; increases surface area

Question 4

Xylem (4)

Answer 4

Transports water and minerals(and amino acids) UP the stem from roots

Dead and hollow cells

Lignified cell walls for support

Bordered pits that allow water to pass in adjacent vessels

Question 5

Tracheids (3)

Answer 5

Feature of Xylem tissue; cells tapered at the end

• thicker and narrower than vessel elements
• contains pits

Question 6

Vessel elements (3)

Answer 6

• feature of xylem tissue
• wider and thinner walls than trachieds
• perforated ends arranged in chains allow continuous flow of water

Question 7

Phloem (4)

Answer 7

Tissue located in vascular bundle

• Alive and functioning cells; companion cells, sieve tube elements and drive plates
• perforated cross walls
• plasmodesmata between companion cells and drive tube elements

Question 8

Companion cells (3)

Answer 8

• part of phloem tissue
• contains organelles sieve tubes elements do not have
• contains plasmodesmata that comes to contact with the cytoplasm

Question 9

Sieve tubes

Answer 9

• chain of sieve tube elements
• sieve plates with perforated walls that allow continuous water flow
• sieve tube elements have no nucleus, ribosome and Golgi apparatus

Question 10

Symplast pathway

Answer 10

• water does not enter vacuole

- goes through plasmodesmata and cytoplasm

Question 11

Endodermis (3)

Answer 11

In root cells; located in the middle

• surrounds vascular bundle
• contains casparian strip that blocks apoplast route

Question 12

Translocation

Answer 12

• transport of organic products from source to sink

- via mass flow

Question 13

Describe 1st step of translocation (3)

Answer 13

• Phloem loaded at the source (eg leaves and stem)
• WP in driver tube cells decreases as solute concentration increases
• therefore water is drawn form other cells via osmosis

Question 14

Describe second step of translocation

Answer 14

• As sieve tube cells draw water, the HP increases and pushes sap to the sink

Question 15

3rd step of translocation (4)

Answer 15

• Organic material unloaded at the sink; decreases SC and increases WP
• water is lost and moves out through osmosis into xylem and up transpiration stream
• Water in transpiration stream is recycled again for the first step of translocation

Question 16

Describe the transportation of water from root to leaves (5)

Answer 16

1- Water moves into roots via osmosis= high HP at the bottom on xylem

2- water pulled up stem due to cohesive and adhesive forces. As well as capillary action

3. Water travels through symplast or apoplast but joins at endodermis when the casparian strip arises
4. ) transpiration occurs at the leaves cause sling low HP at top of xylem

Therefore this is bulk flow as water moves from high HP at bottom of xylem to low HP at the top of xylem

Question 17

Casparian strip

Answer 17

Waterproof band in radial and transverse walls of endorser is

Prevents apoplast pathway

Blocks passive move my of materials into Steele

Question 18

Xerophytes

Answer 18

Plants added to dry habitats

Question 19

Trichome adaption in xerophytes

Answer 19

Abundant:
Increases surface area for osmosis
Reduces air movement which builds up more humid air, leaving a less steep water vapour gradient to prevent transpiration.

Question 20

Stomata adaptation on Xerophytes

Answer 20

Reduced number of stomata: Reduces loss of water via transpiration

Sunken stomata: Reduces are movement. This creates a microclimate that increases water vapour. A less steep water vapour gradient is made, which reduces the rate of transpiration.

Question 21

Leave adaption of xerophytes

Answer 21

Sometimes leaves are curled: Reduces surface area so less water is lost. Also allows more humid air to form.

Thick waxy cuticle; prevents evaporation of water.

Reduced number of leaves: Less surface area for leaves so less water is lost in transpiration.

Question 22

Hydrophytes

Answer 22

Plants adapted to cope with high water availability

Contains Sclerid; filled with lignin, prevents rolling of leaves

Contains aerenchyma; allow buoyancy

Question 23

Trichomes adaptation of hydrophytes

Answer 23

• very scarce; increases air movement to increase rate of transpiration

Question 24

Succulents

Answer 24

Present in some xerophytes:

Specialised parenchyma capable of storing large amounts of water.

Question 25

Leave adaptation of hydrophytes (2)

Answer 25

• Large SA increases rate of gaseous exchange and water loss

- waxy cuticle; thin to prevent water evaporation

Question 26

Root adaptation on some hydrophytes

Answer 26

• aerated (pneumatophores)

- increases gaseous exchange

Question 27

Apoplast

Answer 27

Water pathway across root tissue between and through adjoining cell walls

Question 28

How is transpiration measured?

Answer 28

• Potometer

- Measures the water uptake of a plant

Question 29

Factors that affect Transpiration? (8)

Answer 29

• Temperature:
  Increases kinetic energy of water molecules which increases the rate of transpiration.
  Decreases humidity which also increases the rate.
• Humidity:
  Increased humidity decreases the rate as there is a less steeper concentration gradient between water inside and outside cell.
• Air movement:
  Increased air movement increases the rate as it dries accumulation of water vapour around the stomata.
• Light Intensity:
  Increases as the light increases because more photosynthesis will occur which opens the stomata (when CO2 enters) and causes water vapour to be released.

Question 30

Describe the coupled transport of sucrose. (3)

Answer 30

• H+ ions are pumped out companion cells using ATP
• The ions always move down a concentration gradient
• When the H+ ions diffuse back into the cell, it is coupled transport with sucrose using a protein

Question 31

Evidence to support couple transport?

Answer 31

• Companion cells have a much higher pH that the surrounding cells which shows how a gradient of H+ ions is maintained.
• Companion cells have a high amount of mitochondria due ATP being need.
• Companion cells also have a folded membrane for greater surface area to increase sucrose transported

Question 32

Features of xylem that allow continuous water flow (4)

Answer 32

• conjoined from end to end
• lignified walls
• pits in the walls
• hollow vessels

Question 33

Transpiration (2)

Answer 33

• evaporation of water vapour

- via the stomata

Question 34

Transpiration stream (2)

Answer 34

• movement of water using adhesive and cohesive properties in the xylem vessels
• from the roots to the leaves

Question 35

Root adaptations in xerophytes.

Answer 35

Very long tap roots:

Allows greater surface area to seek out more water in the soil.