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Module 3 > Transport In Plants > Flashcards

Transport In Plants Flashcards

1
Q

Why do plants need a transport systems

A

High metabolic rate
Have a small SA:V ratio
Large diffusion distance
Rate of diffusion too small
Multicellular

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2
Q

Function of guard cells

A

They bend to open & close stomata + control gas exchange

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3
Q

How are guard cells adapted

A

Many chloroplasts & mitochondria to provide ATP
Cells able to change shape
Transport proteins in CSM
Wall thicker on one side

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4
Q

Action of guard cells

A

Mineral ions actively transported into the cell
Decreased water potential & increased w.p. gradient
Water enters the cell via osmosis -> cell = turgid & stomata opens

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5
Q

Vascular system in leafs, stem & root

A
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6
Q

Features of the xylem

A
  • dead cells
  • lignified walls
  • empty lumen
  • bordered pits
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7
Q

Function of the xylem

A

Transport water & dissolved minerals
- up the plant
- from roots to leaves & other upper parts of plant

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8
Q

What’s good about each of the xylem components

A
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9
Q

Features of the phloem

A
  • sieve tube elements
  • peforations
  • companion cells
  • parenchyma cells
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10
Q

Function of phloem

A

Transport assimilates
Such as amino acids & sucrose from source to sink (up & down)

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11
Q

How is the sieve tube element adapted for its function

A

No nucleus & little cytoplasm
Allows for mass sap flow
As it is arranged end to end to form continuous sieve tubes

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12
Q

What are sieve plates

A

Separate sieve tube elements and these also filter out organelles between sieve tube elements

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13
Q

What do perforations in sieve plates do

A

These allow the mass flow of sap between sieve elements

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14
Q

What do parenchyma cells do

A

They’re packing cells which fill spaces between sieve tubes

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15
Q

What do plasmosdesmata do

A

These are gaps in the cell wall between companion cells, & sieve tube elements

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16
Q

Differences between Xylem & phloem

A
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17
Q

Similarities between xylem & phloem

A
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18
Q

How are stems dissected for observation

A
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19
Q

What is transpiration

A

The loss of water vapour from the aerial parts of a plant (especially from the stomata) as a consequence of gas exchange

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20
Q

Why is transpiration important

A
  • maintains cell turgidity
  • coding of plant by water evaporating out of stomata
  • supplies water for growth, cell elongation & photosynthesis
  • the stream transports mineral ions up the plant
21
Q

Why is transpiration unavoidable

A

Stomata has to be open
To allow for gas exchange
Gas exchange required for photosynthesis & so water vapour leaves the lead

22
Q

Why is transpiration diffusion not osmosis

A

As it doesn’t occur over a partially permeable membrane

23
Q

Environmental factors to increase transpiration

A
24
Q

Measuring transpiration using a Potometer

A
25
Q

Safety measures using a Potometer

A
  • use healthy shoot
  • cut stem at a slant underwater
  • dry leaves
  • use petroleum jelly to ensure seal between shoot & potometer is airtight (so no leaks in apparatus)
26
Q

Why do we use these safety measures in a Potometer

A
27
Q

Movement of water into plants -> how does H2O enters via roots

A
  1. Root hair cells actively take up mineral ions
  2. Reduces the water potential of the root hair cells
  3. Water moves by osmosis, down w.p. gradient into root hair cells
  4. Through aquaporins
28
Q

How is root pressure generated

A

-> active transport by endodermis of mineral ions into xylem & medulla
-> lowers w.p.
-> water enters medulla & xylem of roots by osmosis
-> this increases hydrostatic pressure of roots

29
Q

How does water move up the stem

A

Root pressure = high pressure @ bottom of plant
Evaporation / water loss @ top = low pressure @ top of plant
-> pressure gradient created therefore tension in the xylem
Cohesion between H2O molecules = they stick together, forming continuous therefore, water is then pulled up by mass flow down the pressure gradient

30
Q

What’s another way water can move up the stem

A

Capillary action
- water molecules attracted to side of narrow xylem vessel by adhesion therefore, H2O is pulled up the side of a xylem vessel

31
Q

What are the 3 pathways from the root hair to the xylem

A

Vacuolar
Symplastic
Apoplast

32
Q

Vacuolar pathway

A

Passes through vacuoles & cytoplasm of cells by osmosis

33
Q

What is the symplastic pathway

A

Passes through the cytoplasm of cells using plasmosdesmata by osmosis

34
Q

What is the apoplastic pathway

A

Passes through gaps in the cell wall via mass flow:
At endodermis, blocked by Casparian strip & water + dissolved minerals forced to enter symplastic pathway
-> casparian strip is impermeable to wax / waterproof

35
Q

How is H2O loss from the top of the plant replaced

A

1, apoplastic/symplastic/vacuolar pathway
2, down water potential gradient,
3, by water from xylem

36
Q

Endodermal cells -> xylem (h2o movement)

A

Endodermal cells actively transport mineral ions from cortex into medulla & xylem therefore reducing their w.p.
Water moves into medulla & xylem by osmosis down w.p. gradient

37
Q

H2O -> out of leaf

A

Xylem water - > via osmosis / apoplastic pathway - > spongy mesophyll
Evaporates out of the cell walls into spaces in leaves
Diffuses out of open stomata down water potential gradient
H2O can be lost via stomata / the epidermis

38
Q

What is translocation

A

The movement of assimilates up & down the plant

39
Q

How are assimilates actively loaded into the phloem at the source

A
40
Q

Where does sap move

A

From source to sink

41
Q

Movement of sap at source versus at sink

A
42
Q

How can the roots act as a source & a sink

A

Converts starch into sugars, which are loaded into phloem
Stores sugars into starch, which requires sugars to be unloaded from the phloem

43
Q

Why are sugars transported as sucrose

A

Because it’s metabolically inactive
Soluble
Doesn’t get used up by respiration during transport

44
Q

Mass flow attempts to explain how solutes more from source to sink. What’s some evidence for and against it

A
45
Q
A
46
Q
A
47
Q
A
48
Q

What is meant by the term transpiration stream

A

The movement of water from roots to leaves

Module 3 (11 decks)

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