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Biology A level > Transport in plants > Flashcards

Transport in plants Flashcards

Module 2

1
Q

What is the cuticle

A

A waterproofing layer of cutin

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2
Q

What is the epidermis

A

A single layer of cells, transparent to sunlight
secretes cutin

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3
Q

What is the parenchyma

A

Unspecialised cells
Make up the pith and cortex

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4
Q

What is the function of the xylem

A

To transport water and minerals up the plant

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5
Q

What is the structure of the xylem

A

Made of elongated lignified dead cells
Undergoes spiral lignification
Inside is Hydrophillic

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6
Q

What is the purpose of spiral lignification within xylem vessels

A

Lignification -waterproofing, prevents collapse, provides adhesion
Spiral - allows xylem to stretch as plant grows, allows branch/stem to bend

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7
Q

What are the two types of phloem cells

A

Companion cells
Sieve tube elements

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8
Q

What are the features of the sieve tube elements in the phloem

A

little cytoplasm
no nucleus
have mitochondria + RER
have pores
have sieve plates

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9
Q

Features of the companion cells in the phloem

A

Large nucleus
Dense cytoplasm
Lots of mitochondria
Carry out metabolic processes required by sieve tubes

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10
Q

What are plasmodesmata

A

Gaps within cell walls that connect the cytoplasm of two adjacent cells

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11
Q

What are the three pathways that water and minerals get to the xylem

A

Apoplast
Symplast
Vacuolar

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12
Q

What is the Vacuolar pathway

A

Water enters through plasma membrane and passes through the plasmodesmata from one cell to the next
Can pass through the vacuoles

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13
Q

What is the symplast pathway

A

Water enters through plasma membrane and passes through the plasmodesmata from one cell to the next

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14
Q

What is the apoplast pathway

A

Water passes through spaces in the cell wall and between cells

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15
Q

How is water moved from the outside to the xylem

A

Minerals are actively transported into the root hair cell - lowering w.p. Water then moves in through osmosis. It then follows three different pathways (down a wp grad). When it gets to the casparian strip, water is forced into the cytoplasm. Minerals are actively transported into xylem and water follows through osmosis. No leaks due to casparian strip

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16
Q

What is transpiration

A

The process of water moving through a plant and it’s evaporation from aerial parts

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17
Q

How does water move up the stem

A

root pressure
transpiration pull
capillary action

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18
Q

What is root pressure

A

When osmosis is driven by minerals moving into cells by active transport
Gets water from outside to xylem
More water entering means more water will be pushed up the stem

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19
Q

What is transpiration pull

A

Cohesion causes water molecules to be pulled up when water molecules evaporate as they stick together, this pull from above causes tension

20
Q

What is capillary action in plants

A

Adhesion causes water molecules to be attracted to the lignin
The narrowness of the xylem causes these forces of attraction to pull up water via the sides of the xylem

21
Q

How does water leave the leaf

A

Water moves from xylem to a spongy mesophyll cell via a pit
Water evaporates
Water vapour diffuses down a water vapour potential gradient across the airspace and out the stomata
Water vapour is taken away by air currents

22
Q

What steps should be taken when setting up a potometer

A

Cut shoot underwater
Make sure there are no air bubbles
Make sure shoot is healthy
Cut end off shoot

23
Q

Why does the plant use the transpiration stream

A

Photosynthesis
Growth
turgidity
mineral/ion transport
keeps plant cool

24
Q

What factors effect rate of transpiration

A

Number of leaves
Temperature
Features of stomata
Thickness of cuticle
Light
Humidity
Air movement
Water availability

25
Q

How does light effect the rate of transpiration

A

Opens stomata
Increases rate of photosynthesis

26
Q

How does temperature effect the rate of transpiration

A

Increase in KE
More evaporation from spongy mesophyll
increase rate of diffusion
decreases water vapour potential in air
increases water vapour potential gradient

27
Q

How does humidity effect the rate of transpiration

A

Higher humidity = less water loss
smaller water vapour potential gradient

28
Q

How does air movement effect the rate of transpiration

A

Carries away water vapour
Maintains a high water vapour gradient

29
Q

Why is transpiration unavoidable during the day?

A

Stomata have to be open to allow for gaseous exchange for photosynthesis

30
Q

What is the name of plants adapted to live in very dry or arid conditions

A

xerophytes

31
Q

What are the adaptations to reduce water loss

A

lose leaves in winter
smaller leaves (needles)
Densely packed spongy mesophyll
Thick waxy cuticle
Hairs on surface
Sunken stomata
Rolling leaves
High salt conc in cells

32
Q

Why does having densely packed spongy mesophyll reduce water loss

A

reduces SA exposed so less water evaporates into air spaces

33
Q

How does hairs on the surface of plants reduce water loss

A

Traps a layer of air that is saturated with water vapour
decreases water vapour potential gradient

34
Q

How does sunken stomata reduce water loss

A

Traps a pocket of air saturated with water vapour
reduces water vapour potential gradient

35
Q

How does rolling leaves reduce water loss

A

Traps a pocket of air saturated with water vapour
reduces water vapour potential gradient

36
Q

How does maintaining a high salt concentration in cells reduce water loss

A

Lowers water potential, means more water can enter through osmosis

37
Q

What are the features of marram grass

A

xerophytes
Thick waxy cuticle
rolled leaves
leaf hairs
sunken stomata

38
Q

Features of cacti

A

No or thin leaves
small surface area
stores water in stem
have shallow wide spreading leaves

39
Q

What are hydrophytes

A

Plants adapted to live in and on water

40
Q

What are feature of hydrophytes

A

Air spaces in leaves so they can float
Air spaces in roots and stem so O2 can move from leaves to underwater parts
Stomata on upper surface
Flexible leaves and stems

41
Q

What do companion cells contain

A

Many plasmodesmata
All major organelles
Many mitochondria

42
Q

What do sieve tubes contain

A

mitochondria
sieve plate

43
Q

What is translocation

A

Movement of assimilates from source to sink
Sugars in the form of sucrose are transported via phloem

44
Q

How does the process of translocation occur

A

H+ are actively moved from companion cell to source cell by proton pump
H+ move back into companion cells down a conc grad through the H+ sucrose cotransporter - this means sucrose is moved in too
Conc of sucrose builds up in companion cell, this means it will diffuse down a concentration gradient into phloem via plasmodesmata
water potential in phloem decreases so water moves into phloem from xylem by osmosis
this causes an increase in hydrostatic pressure
Water moves down xylem to a lower hydrostatic pressure at sink, this carries assimilates with it

45
Q

What are some differences between the xylem and phloem

A

Xylem has no cytoplasm, Phloem does
Xylem is lignified, phloem isn’t
Xylem has bordered pits, phloem doesn’t

Biology A level (20 decks)

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