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Biology > 3.3 Transport in Plants > Flashcards

3.3 Transport in Plants Flashcards

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1
Q

What do the xylem and phloem make up ?

A

Make up the vascular tissues that are responsible for transport of reactants and products of chemical reactions around the plant.

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2
Q

What is the role of the xylem ?

A

Dead cell that transports water and mineral ions from the roots to the leaves.

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3
Q

What is lignin and where is it found ?

A

Lignin waterproof the xylem and provides reinforcement so they don’t collapse under transpiration pull. Deposit of lignin is known as lignification.

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4
Q

What is lignification ?

A

Deposit of lignin. Leads to death of xylem cells (loss of cytoplasm, organelles, end walls, etc)

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5
Q

Is lignification complete ?

A

No, as it leaves gasping cell walls of xylem called bordered pits. Pits in 2 adjacent xylem cells are aligned to allow water to leave and go to another xylem cell.

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6
Q

What is capillary action ?

A

Forces that hold water molecules together (cohesion) also attract molecules to sides of xylem (adhesion). These forces of attraction pull water up, known as capillary action.

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7
Q

Parenchyma

A

Packing tissue which fills spaces between xylem and phloem. It is a living tissue.

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8
Q

What is phloem and its function ?

A

Sucrose dissolves and forms cell sap, which is transported by phloem. Amino acids are also transported. These are the 2 most common assimilates made by plant using substances absorbed from environment.

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9
Q

What are sieve tube elements ?

A

Cells that form sieve tube.
It does not contain a nucleus and has little cytoplasm to allow lots of space for cell sap.
Also has perforations to allow cell sap to move between sieve tube elements.

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10
Q

What 2 cells does the phloem consist of ?

A

Sieve tube elements and companion cells.

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11
Q

What are the companion cells and their function ?

A

Carry out active process, which are needed to load assimilates into sieve tubes.
Has large nucleus and a dense cytoplasm with lots of mitochondria.

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12
Q

Why is there lots of mitochondria in the cytoplasm of companion cells ?

A

Needed to produce ATP for active transport of moving of assimilates.

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13
Q

What is plasmodesmata ?

A

Thin strand of cytoplasm that links content of adjacent cells. Allows flow of assimilates between cells.

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14
Q

What kind of flow does the xylem and phloem have ?

A

-Xylem = uni-directional flow
-Phloem = bi-directional flow.

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15
Q

What is translocation ?

A

Transport of assimilates.

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16
Q

What is transpiration ?

A

Transport of water.

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17
Q

What are some features of the root hair cell ?

A

-Large surface area.
-Lack of chloroplasts
-Lots of mitochondria (for ATP for transport of mineral ions)

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18
Q

What is the first step of transport in root hair cells?

A

Mineral ions enter root hair cell via active transport, which requires ATP, to move them against concentration gradient. This lowers water potential so water will follow mineral ions and diffuse by osmosis.

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19
Q

What is the epidermis ?

A

Outermost cell layer of a plant and root hair cell are located in this outer layer in roots.

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20
Q

What is the root cortex ?

A

Series of plant cells on outer layer under epidermis.

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21
Q

What is the symplast pathway ?

A

Where water and mineral ions move through cytoplasm via plasmodesmata.

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22
Q

What is the vascular pathway ?

A

Where water and mineral ions move through cytoplasm and pass through vacuole where it passes through to another cell.

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23
Q

What is the apoplast pathway ?

A

Where water moves by mass flow as opposed to osmosis to allow dissolved mineral ions to be carried through the root cortex.

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24
Q

What is the endodermis ?

A

A cylinder of cells that forms the final boundary between the cortex and inner region of a plant.

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25
Q

What do walls of endodermis contain and what does this create?

A

Contains Suberin, which is impermeable and waterproof. Together this forms a water tight seal known as the casparian strip.

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26
Q

What pathway does the Casparian strip block ?

A

Blocks the apoplast pathway between the cortex and the medulla.

27
Q

What does the Casparian strip do to water and mineral ions ?

A

Forces them back into cytoplasm and actively pumps into medulla followed by water as it lowers the water potential gradient, so water moves down the water potential gradient.

28
Q

What increases when mineral ions and water are transported in the xylem ?

A

Root pressure increases.

29
Q

What occurs higher up the stem, in terms of root pressure, out of the xylem ?

A

There is a lower root pressure.

30
Q

What does root pressure create ?

A

Creates a root pressure gradient, which forces water to move up the xylem by mass flow.

31
Q

How much can root pressure move water by ?

A

Root pressure can move water by a few meters at time.

32
Q

What is transpiration and why does it occur ?

A

Transpiration is the movement of water that is inevitable consequence of gas exchange.

33
Q

Why is transpiration described as inevitable consequence of gas exchange ?

A

As stomata in a leaf remain open during the day, so CO2 can enter for photosynthesis.

34
Q

What is transpirational pull ?

A

When the water vapour lost in a cell, must be replaced by moving up the xylem known as the transpirational pull.

35
Q

What is cohesion ?

A

It is the attraction between the same type of molecule. Water is very cohesive due to the hydrogen bonds. This enables water to move by mass flow.

36
Q

What is adhesion ?

A

Attraction between 2 different types of molecules. Water molecules adhere to molecules on side of xylem vessel walls, allowing water to move upward.

37
Q

What is capillary action ?

A

Attraction between water molecules and walls of xylem vessels causing the column of water to move upward.

38
Q

Is capillary action smaller or greater in small vessels?

A

Greater.

39
Q

How can water leave the leaf ?

A

-Leave via stomata.
-Used up in photosynthesis.
-Used to fill guard cells to close stomata.
-Some is lost through the waxy cuticle.

40
Q

What does water turn into once it has left the xylem and reached the spongy mesophyll?

A

Water vapour.

41
Q

How does water vapour diffuse (gradient)?

A

Water vapour diffuses from a high to low water vapour potential, down the water vapour potential gradient.

42
Q

How are chemicals loaded in sieve tubes ?

A

They are actively loaded by companion cells.

43
Q

How does ATP form to ADP ?

A

By hydrolysis.

44
Q

What is the first step in plant translocation ?

A

H+ ions (protons) are pumped out of companion cell.

45
Q

What is a co-transporter protein ?

A

Protein that can move 2 molecules across membrane via facilitated diffusion. They pump protons and sucrose back into companion cell.

46
Q

Is sucrose transported with or against concentration gradient in translocation ?

A

Sucrose is transported against the concentration gradient back into the companion cells.

47
Q

What happens to sucrose once it has moved back into companion cells in translocation ?

A

Sucrose, or amino acids, move into phloem down the concentration gradient via the plasmodesmata.

48
Q

What is hydrostatic pressure ?

A

Pressure exerted by a fluid on its container at a given point. This increases when sucrose diffuses from the companion cell.

49
Q

What lowers when sucrose enters the sieve tube elements ?

A

Water potential lowers causing water to enter sieve tube elements via osmosis.

50
Q

What is translocation ?

A

Mass flow of assimilates down the hydrostatic pressure gradient from a source to a sink.

51
Q

What is stomata regulation ?

A

Turgor driven process where the solute is transported against the gradient . Water potential is lower so water follows solute.

52
Q

What does asymmetric configuration in guard cell cause ?

A

Causes guard cell to bend when it is swollen with water causing it to open.

53
Q

What are 5 factors that affects rate of transpiration?

A

Air movement, humidity, temperature, light intensity and soil-water availability.

54
Q

How does air movement affect rate of transpiration ?

A

Air is trapped beneath the leaf. Water diffuses out of stomata, which accumulates in layer of air. Increases WP in air lowering WP gradient. Blows air away taking water.

55
Q

How does humidity affect rate of transpiration ?

A

A lower humidity increases water potential gradient as WP is lower outside the leaf causing water to be lost by stomata.

56
Q

How does temperature affect rate of transpiration ?

A

A higher temperature increases KE of water molecules so increases rate of evaporation in air spaces.

57
Q

How does light intensity affect rate of transpiration ?

A

Increases light intensity means there are more stomata open which means more water molecules diffuse out.

58
Q

How does soil-water availability affect rate of transpiration?

A

More soil-water avaliability increases rate of transpiration as the plant wont be under ‘water stress’.

59
Q

What is a potometer ?

A

Measures water uptake. More evaporation is faster transpiration as bubble speed increases.

60
Q

Where is marram grass found ?

A

Found in sand dunes where water drains quickly and it is often very windy.

61
Q

What some adaptations of marram grass ?

A

-Long roots (15-20 m )
-Leaves roll up longitudinally to trap humid air.
-waxy cuticle.
-Stomata on inner surface of rolled leaf protect from air movement.
-Stomata in pits.
-Covered in hairs.

62
Q

What are cacti ?

A

They are succulents that store water in their stems, which can expand to allow more water to be stored.
-Have spines (leaves) that reduced SA.
-Widespread roots to collect any rain.

63
Q

What are some adaptations of water lilies ?

A

-Many air spaces = keeps leaves afloat.
-Stomata on upper epidermis.
-Small roots .
-Flat leaves for increased SA for gaseous exchange.

64
Q

What do hydrophytes have to increase rate of reaction ?

A

Have hydathodes that release water droplets. This lowers the water potential in leaves generating transpirational pull.

Biology (15 decks)

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