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A Level Biology > Transport In Plants > Flashcards

Transport In Plants Flashcards

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1
Q

What does xylem tissue transport?

A

Water and dissolved minerals

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2
Q

What are the main components of xylem tissue?

A

Xylem vessels, fibres, and parenchyma cells

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3
Q

What happens to xylem cells as they become lignified?

A

Cells die and contents and end walls decay, forming xylem vessels

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4
Q

Describe the structure of xylem vessels.

A

Continuous, hollow tubes with no end walls or contents

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5
Q

Why is there less resistance to the flow of water in xylem vessels?

A

Due to lack of contents and more space

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6
Q

What is the role of lignin in xylem vessels?

A

Increases cell wall rigidity and strengthens it

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7
Q

How does lignin affect the xylem vessel walls?

A
  • Prevents collapse under tension
  • Waterproofs the wall
  • Reduces lateral flow of water
  • Improves adhesion of water molecules
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8
Q

What pattern does lignification occur in xylem vessels?

A

Spiral pattern

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9
Q

What is the advantage of the spiral pattern in xylem vessels?

A

Allows the tubes to remain flexible

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10
Q

What are bordered pits in xylem vessels?

A

Pores in walls of vessels

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11
Q

What is the function of bordered pits?

A
  • Allow water to divert into other tubes if one gets blocked
  • Allow lateral movement of water between vessels
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12
Q

Why is a narrow lumen beneficial in xylem vessels?

A

Increases capillary rise and makes capillary action more effective

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13
Q

What is the function of phloem?

A

Transports sugars (sucrose) up and down the plant

Phloem is essential for the distribution of nutrients throughout the plant.

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14
Q

What are the main components of phloem?

A

Made of sieve tube elements and companion cells

These components work together to facilitate the transport of nutrients.

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15
Q

What is the structure of sieve tube elements?

A

Thin layer of cytoplasm

This structure allows for less resistance and more space for transport.

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16
Q

What is the significance of sieve plates?

A

Allows continuous transport

Sieve plates are crucial for the bi-directional flow of sucrose.

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17
Q

True or False: Sieve tube elements have a large nucleus.

A

False

Most organelles, including the nucleus, are absent in sieve tube elements.

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18
Q

What is the role of companion cells?

A

Provides large amounts of ATP for active processes

Companion cells are vital for loading sucrose into sieve tubes.

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19
Q

Fill in the blank: Sucrose is transported as _______ dissolved in water.

A

sap

This sap is essential for the transport of nutrients within the plant.

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20
Q

What structures connect sieve tube elements to allow sucrose transport?

A

Plasmodesmata

Plasmodesmata facilitate the transport of molecules such as proteins and ATP.

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21
Q

What type of flow does phloem allow?

A

Bi-directional flow

This means sucrose can move both up and down the plant.

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22
Q

What is a key characteristic of sieve tube elements that aids in transport?

A

Less resistance for transport

The thin layer of cytoplasm contributes to this characteristic.

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23
Q

What is the function of the nucleus in companion cells?

A

Controls the functions of companion cell and sieve tube elements

The nucleus is essential for maintaining the activity of these cells.

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24
Q

What type of respiration do companion cells require?

A

A lot of respiration

This is necessary to generate ATP for active transport processes.

25
Q

True or False: Sieve tube elements are living cells.

A

True

Despite lacking many organelles, sieve tube elements are still classified as living.

26
Q

What is water potential?

A

The potential energy of water in a system compared to pure water

Water potential determines the direction of water movement in plants.

27
Q

What happens to a plant cell when water enters it?

A

The cell becomes turgid

Turgidity is a state where the cell is firm due to water uptake.

28
Q

What is the water potential of a concentrated solution?

A

Very low

Concentrated solutions have lower water potential compared to dilute solutions.

29
Q

What occurs when water leaves a plant cell?

A

The cell becomes plasmolysed

Plasmolysis occurs when the cell membrane pulls away from the cell wall.

30
Q

How does water enter root hair cells?

A

Through osmosis

Water moves from an area of higher water potential in the soil to lower potential in the root hair cells.

31
Q

What are root hair cells adapted for?

A

They increase surface area for osmosis and mineral uptake

Adaptations include hair-like projections and thin cell walls.

32
Q

What is the function of mitochondria in root hair cells?

A

To provide energy for active transport of minerals

Energy from mitochondria is crucial for mineral uptake against the concentration gradient.

33
Q

What is the apoplast pathway?

A

Water travels through cell walls in gaps

This pathway does not involve crossing cell membranes.

34
Q

What is the symplast pathway?

A

Water crosses cell surface membranes and moves through plasmodesmata

This pathway allows for direct movement within the cytoplasm of connected cells.

35
Q

What is the vacuolar pathway?

A

Water moves through vacuoles as well as the cytoplasm

Similar to the symplast pathway but includes vacuole movement.

36
Q

Fill in the blank: Water moves into the root hair cell via osmosis across the cell surface, down the _______.

A

water potential gradient

This movement is driven by differences in water potential.

37
Q

What is the Casparian Strip?

A

A strip of waterproof material called suberin in the cell walls of the endodermis.

38
Q

How are minerals transported into the xylem?

A

Minerals must be actively transported from the cytoplasm into the xylem through carrier proteins.

39
Q

What is the relationship between water potential and osmosis in the xylem?

A

Water potential is lowest in the xylem, causing osmosis of water from the root hair cell to the endodermis.

40
Q

What pathway is blocked by the Casparian Strip?

A

The apoplast pathway.

41
Q

After the Casparian Strip blocks the apoplast pathway, what pathway must water take?

A

The symplast pathway.

42
Q

What effect does the active transport of minerals have on water potential in the xylem?

A

It lowers the water potential in the xylem.

43
Q

Where does water move from during osmosis into the xylem?

A

From the cells of the endodermis and cortex.

44
Q

Fill in the blank: Water moves from soil into root hair cells across cell surface membrane through _______.

A

[aquaporins]

45
Q

What are the two pathways water can take to move across the soil cortex?

A
  • Apoplast pathway
  • Symplast pathway
46
Q

True or False: The Casparian Strip allows water to flow freely through the apoplast pathway.

A

False

47
Q

What is the primary function of the Casparian Strip in water movement?

A

To force water to enter the symplast pathway.

48
Q

What links the cytoplasm in neighboring cells for water movement?

A

Plasmodesmata.

49
Q

What causes the water potential to be most negative in the xylem?

A

The active transport of minerals into the xylem.

50
Q

What happens to water potential as minerals are actively transported into the xylem?

A

It decreases, causing water to move into the xylem.

51
Q

Transpiration

A

The loss of water by evaporation out of plant leaves via the stomata
- happens at the same time as gas exchange

52
Q

3 ways water is helped move up the xylem vessels from the root

A

Root Pressure
- the push from the water entering the vessels in the roots (doesn’t move water far)

Capillary Action
- adhesion of water molecules to lignin in narrow vessels and pull water up the sides of the vessel

Transpiration Pull
- most of the driving force

53
Q

Evidence for cohesion-tension theory

A

Changes on the diameter of trees
- when transpiration is at its highest rate in the day, the tension in the xylem vessels is also highest
- this causes the tree to shift in diameter

if xylem is broke, air is drawn in rather than water leaking out
- if a xylem vessel breaks, pressure is lost
- this means that the cohesive forces (H bonds) break, and water cannot be pulled up so air is pulled out

54
Q

Factors affecting transpiration rate

A
  • number of leaves
  • number & size of stomata
  • waxy cuticle present
  • light
  • temperature
  • humidity
  • wind
  • water availability
55
Q

Xerophytes

A

A plant that is adapted to reduce water loss through transpiration so that it can survive in very dry, arid conditions

56
Q

Xerophyte adaptations

A
  • epidermis covered in hairs
  • thick waxy cuticle
  • small leaves/needles
  • sunken stomata in pits
  • curled leaves
  • small air spaces in mesophyll
  • stomata shut in day, open at night
57
Q

Hydrophyte

A

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

58
Q

Hydrophyte adaptations

A
  • many large air spaces in the leaf - keeps leaf afloat
  • stomata are on the upper epidermis- exposed to air for gas exchange
  • leaf stem has many large air spaces- helps with buoyancy, but also allows oxygen to diffuse quickly to the roots for aerobic respiration.

A Level Biology (16 decks)

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