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Biology > 3.3 Transport in Plants > Flashcards

3.3 Transport in Plants Flashcards

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1
Q

What is the xylem made of?

A
  • Lignin waterproof cell walls
  • Long column of DEAD ccells
  • Cells are end to end
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2
Q

What is the purpose of lignin in the xylem?

A
  • Strengthen walls of xylem
  • Prevent it from collapsing
  • Doesnt impede flow of water
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3
Q

What are the patterns of lignification?

A
  • Spiral
  • Annular
  • Reticular
  • Pitted
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4
Q

What is the purpose of pitted lignification?

A
  • Allows water to move to adjacent cells/vessels
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5
Q

What are the adaptations of xylems for function?

A
  • Continuous column
  • Narrow (column of water doesnt break)
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6
Q

What is vascular tissue?

A
  • Transport tissue
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7
Q

Why do plants need a transport system?

A
  • Multicellular
  • Small SA:V ratio
  • Continual growth
  • Water and sugars foound in different places than needed
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8
Q

How does water move into the cell?

A
  • Minerals actively transported from soil to root hair cell
  • Decreases water potential inside cell
    -Water follows via osmosis
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9
Q

What adaptations does a root have?

A
  • Many root hairs increase surface area
  • Lots oof mitochondria for active transport of ions
  • Thin wall
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10
Q

How does water move across the root?

A
  • Endodermis actively transports the minerals into xylem
  • Water potential inn xylem decreases
  • Water moves into endodermal cells via osmosis
  • Water potential gradient established
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11
Q

What is the apoplast pathway?

A
  • Between cells and between cellulose fibres in cell walls
    DOES NOT CROSS MEMBRANE
    Path of least resistance
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12
Q

What is the symplast pathway?

A
  • From cell cytoplasm to cytoplasm via membranes/plasmodemata
    SYM —> CYTO
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13
Q

What is the vacuolar pathway?

A

-Same as symplast but through vacuoles as well
- Path of most resistance

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14
Q

What is the casparian strip?

A
  • Special cells with suberin (waterproof chemical) in cell walls
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15
Q

How does the caspariian strip stop toxins,ions etc. from entering xylem?

A

Forces water containing whatever to go through partially permeable cell membrane instead which will not take any toxins.

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16
Q

What is the plasmodesmata?

A
  • Small gaps in the cell wall which causes cytoplasm to join
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17
Q

What is root pressure?

A

Where water entering the xylem is forced up the xylem due to a constant pressure from active processes

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18
Q

What is cohesion tension theory?

A
  • Water molecules lost at top of xylem causes whole column of water to be pulled up under tension by mass flow due to cohesion between molecules.
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19
Q

How does capillary action apply to cohesion-tension theory?

A
  • Water molecules adhere to side of xylem
  • Xylem vessels are narrow so theyre pulled up the xylem vessel
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20
Q

What is transpiration?

A

The loss of water vapour from the leaves and stems of plants

21
Q

What is a transpiration stream?

A
  • COntinual movement of water from the roots up the stem into the leaves and out via stomata
22
Q

How does light intensity effect transpiration?

A
  • More open stomata
23
Q

How does humidity effect transpiration?

A
  • Higher water potential outside than normal so less transpiration
24
Q

How does wind affect transpiration?

A
  • Water potential gradient increases
  • Water is removed more quickly
25
Q

How does soil water availability affect transpiration?

A

Less soil water means less transpiration can occur

26
Q

What are the pores that most water is lost through on a leaf?

A

Stomata

27
Q

What is a xerophyte?

A

Plants in a dry habitat surviving on little water

28
Q

What adaptations do most plants have to minimise water loss?

A

Waxy Cuticle- Reduces rate of transpiration
Stomata- Closes to reduce evaporation
Roots- Grow down

29
Q

What adaptations do xerophytes have on top of normal adaptations?

A
  • Sunken Stomata- Reduce air movement so reduces water potential gradient
  • Reduced numbers of stomata
    -Less leaves- reduced SA:V ratio
  • Root adaptations= Large long tap roots to get water deep under surface or Widespread shallow roots to get rainwater before it evaporates
30
Q

What are hydrophytes?

A
  • Plants that live in water
31
Q

What problems do hydrophytes face?

A
  • Leaves need to float for photosynthesis
    -Water logging is a problem
32
Q

What adaptations do hydrophytes have?

A
  • Very thin or no waxy cuticle
  • Many open stomata on upper surface
    -Reduced structure
  • Small roots
    -Air sacs allowing flowers/leaves to float
33
Q

What is translocation?

A

Transport of assimilates throughout the plant in phloem tissue

34
Q

What is a source?

A
  • Where ever sucrose is released into the phloem
35
Q

What is a sink?

A
  • Where sucrose is removed from the phloem
36
Q

What structure does the phloem have?

A

-Thin layer of cytoplasm in sieve tube element to create more space for assimilates
- Companion cells
- Plasmodesmata linking companion cells and sieve cells

37
Q

Why is glucose turned into sucrose?

A

Glucose is too reactive so has to be turned into sucrose

38
Q

How does sucrose enter phloem?

A
  • H+ ions pumped into surrounding tissue
  • Diffusion gradient established
  • H+ diffuse back into cell passively bringing sucrose with them due to co-transporter proteins
  • Concentration of sucrose in companion cell rises
  • Establishes another concentration gradient and sucrose diffuses into phloem along gradient
39
Q

What happens where sucrose enters the phloem?

A

-Sucrose entering decreases water potential
- water enter phloem via osmosis
- Increased hydrostatic pressure which moves phloem along

40
Q

What happens at a sink in relation to sucrose?

A
  • Sucrose used by cells around phloem causes it to diffuse out
  • Water potential of cells surrounding phloem decreases
  • Water follows via osmosis
  • Decreased hydrostatic pressure
41
Q

What gradient is established between source and sink?

A

Hydrostatic pressure gradient causing water along with assimilates to move along gradient by mass flow

42
Q

Why are potometers used for measuring transpiration?

A
  • Water vapours are hard to collect
  • Hard to distinguish which process they’re from
43
Q

How is air prevented from getting in the potometer?

A
  • Shoot is cut under water
  • Apparatus is sealed with waterproof sealant
  • Taps,corks and pipes used to seal holes
44
Q

What does the rate of bubble movement in a potometer relate to in transpiration?

A
  • How much transpiration is occuring
45
Q

What is the evidence for active transport moving minerals and water into the root?

A
  • Administrating cyanide affects mitochondria and limits ATP needed for respiration- Causes root to disappear as no pressure can be maintained
  • Higher the temperature the higher the root pressure due to chemical reactions being involved
  • If respiratory substrates are reduced Root pressure falls because less ATP is produced
  • Xylem sap exits plant when transpiration is low indicates that there is less pressure
46
Q

What evidence is there for cohesion tension theory?

A
  • When transpiration is higher the tension is higher and in trees the diameter shrink (when transpiration is lower,less pressure is applied and xylem widens)
  • When a stem is cut air is pulled in due to pressure inside pulling water up under mass flow and the pressure continues even when cut
  • Plant can no longer pull water up if air gets in as water is no longer being forced in by Active transport so root pressure is weakened and hydrostatic pressure is destroyed
47
Q

What evidence is there for translocation?

A
  • Microscopy allows us to see adaptations in companion cells
  • Flow of sugars is 10000x faster than if it was diffusion alone
  • When given a metabolic poison translocation stops (Poison stops mitochondria) ATP is made by mitochondria proving its an active process
48
Q

What evidence is there against the loading of sugars into phloem?

A
  • Not all solutes in phloem move at same rate
  • Sucrose is always at the same rate
  • No one knows how sieve plates work

Biology (26 decks)

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