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Biology Module 3 > 3.1.3 > Flashcards

3.1.3 Flashcards

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1
Q

What are Dicotyledonous Plants?

A

Dicots make seeds that have 2 cotyledons

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2
Q

What are cotyledons?

A

Organs to act as food stores

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3
Q

What are the two different dicots?

How are they different?

A
  • Herbaceous: soft tissue and short life-cycle

- Arborescent: hard lignified tissues and long life cycle

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4
Q

What is the vascular system?

A

It’s made up of two types of transport vessels: xylem, phloem
Has vascular bundles in roots stems leaves

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5
Q

What are the other tissues associated with herbaceous dicots?

A

Thick-walled xylem parenchyma, packs around the vessels and stores food and has tannin deposits

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6
Q

What is the purpose of tannin deposit?

A

Is bitter tasting

Protects plants against herbivores

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7
Q

What are the small unlignified areas of the xylem? What happened here?

A

Bordered pits

Water leaves the xylem

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8
Q

What does the phloem transport?

A

Sugar and amino acid is needed for cellular respiration and synthesis of other useful molecules

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9
Q

How do sieve plates?

A

Walls become perforated
Large pores appear in the cell walls,
Tonoplast, nucleus and other organelles breakdown

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10
Q

What is the tonoplast?

A

Vacuole membrane

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11
Q

Where are companion cells found?

A

Linked to Sieve tube elements by many plasmodesmata

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12
Q

What is plasmodesmata?

A

microscopic channels through cellulose cell walls linking the cytoplasm of adjacent cells

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13
Q

What 2 ways help reduce water loss from the leaves?

A
  • Waxy cuticle: waterproof

- stomata is shut during the night

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14
Q

How does stomata close?

A

Turgor-driven process

When turgor is low (scarce water), guard cell walls close the pore

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15
Q

List the six factors that affect water loss

A
  • Light
  • humidity
  • dry air
  • temperature
  • air movement
  • soil water availability
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16
Q

Explain how temperature affects the rate of transpiration

A

-Increase in kinetic energy
Increases rate of evaporation
-Increases concentration of water vapour external air can hold

Both increase diffusion gradient therefore increases the rate of transpiration

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17
Q

Explain how Air movement affects the rate of transpiration

A

There is a layer of trapped air rather leave
Air movement increases the rate of transpiration

Long periods of still air are reduces transpiration

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18
Q

How does soil water availability affect the rate of transpiration?

A

If the plant is very dry
(under water stress)
Rate of transpiration decreases

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19
Q

Explain how light affects the rate of transpiration

A

Stomata open to lets gas exchange happen for photosynthesis (as light is needed)
Number of stomata open increases
Water vapour loss increases
Rate of transpiration is increased

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20
Q

Explain how humidity affects the rate of transpiration

A

-Water vapour is lost decreases
Due to reduced water vapour potential between inside leaf and outside air
Rate of transpiration decreases

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21
Q

Explain how dry air affects the rate of transpiration

A

It has the opposite effect of humidity

Therefore transpiration rate increases

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22
Q

Give five reasons as to why water is important for structure and metabolism in plants

A
  • Photosynthesis
  • transports minerals and irons
  • lots of water keeps plants cool
  • Turgor (hydrostatic) pressure gives a hydrostatic skeleton to support the stem and leaves
  • Turgor, Drive cell expansion enabling plant roots to force their way through tarmac and concrete
23
Q

How root hairs has adapted?

A
  • Microscopic size to penetrate
  • large surface area: volume ratio
  • thin surface layer
  • concentration of solutes in cytoplasm maintains water potential gradient
24
Q

How does water moves into the roots?

A

Soil water has low concentration of dissolved minerals, high water potential
Cytoplasm and vacuolar sap has many solvents, low water potential
Water moves in

25
Q

What is the symplast pathway?

A

Continuous cytoplasm connect through plasmodesmata by osmosis

26
Q

How does all to move through the symplast pathway?

A

Root hair cell has higher water potential the next cell, so water moves through osmosis until the xylem is reached
water leaves, water potential drops leaving a steep concentration gradient
More water enters

27
Q

What is the apoplast pathway?

A

Movement of water through cell walls and intercellular spaces

28
Q

How does water move through the apoplast pathway?

A

Water fills spaces between loose open network of fibres in Celulose cell wall
As water moves into the xylem, more is pulled due to cohesive forces
Cohesive forces cause tension meaning there is continuous flow
The open structure has little to no resistance

29
Q

What is the Casparian strip?

A

Band of waxy material around each endodermal cell (waterproof layer)

30
Q

What happens to the water once it reaches the Casparian strip and why?

A

It can’t go any further,
Forced into cytoplasm to join symplast pathway
Passing through semipermeable cell surface membrane excludes potentially toxic solutes

31
Q

How does water moves into the xylem?

A

Solute concentration is more dilute in endodermal cells compare to xylem cells.
Mineral ions are moved into the xylem by active transport
Water potential of xylem decreases
This increases the rate of water moving into xylem by osmosis

32
Q

What happens to water once in vascular bundle? (To do with movement of water into xylem)

A

Once in the VB, water returns to apoplast pathway to enter xylem and move up
Active pumping of minerals into the xylem results in a root pressure that gives water push up the xylem

33
Q

Describe the transpiration stream

A

Water is lost from leaves, Water potential is lowered
Water moves in by osmosis

Water molecules from Hydrogen bonds with carbs on xylem vessels (adhesion)
As well as each other (cohesion)
Cohesion + adhesion->Capillary action

34
Q

What is capillary action?

A

Where water can rise up another tube goes to gravity in a continuous stream
The continuous stream results in a transpiration pull, which results in tension that helps or to move across roots from soil

35
Q

What is the cohesion tension theory?

A

Water moves from soil in continuous stream up the xylem and across to leaf

36
Q

What are xerophytes?

A

Plants in dry habitats

37
Q

List the ways that xerophytes are adapted to conserve water.(10 ways)

A
  • Thick waxy cuticle
  • sunken stomata
  • less stomata
  • reduced leaves
  • hairy leaves
  • curled leaves
  • succulents
  • Leaf loss
  • root adaptations
  • avoiding the problems
38
Q

Xerophytes
How does hairy leaves and curled leaves help conserve water?
What else can do this?

A

Microclimates of humid air reduces water vapour potential gradient
Reduces transpiration
The sunken stomata that is located in the pits

39
Q

Xerophytes

How does losing leaves help conserve water?

A

Limits transpiration as there is no surface water to be lost

Trunk and branches turn green and photosynthesise

40
Q

Xerophytes

How do you root adaptations help conserve water loss?

A

Long to penetrate several layers

Shallow with large surface area to get rainwater before it’s evaporated

41
Q

What are hydrphytes?

A

Plants that live in the water
Submerged/on surface/edge of bodies of water
-leaves need to float near surface to get lights
-waterlogging is a problem (airspaces set up with water when it should be air)

42
Q

What are the adaptations of hydrophytes that help decrease water loss?

A
  • Thin or no waxy cuticle
  • stomata always open
  • reduced structure
  • wide flight leaves
  • small roots
  • large SA of stems and roots and the water
  • air sacs
  • aerenchyma
43
Q

What is aerenchyma?

A

-Specialised parenchyma (Packing) tissue

Large air spaces

44
Q

What is the function of aerenchyma?

A

-Buoyancy of leaves and stems
-forms low resistance pathway for movement of substances e.g.O2 under water
Helps plant cope with anoxic conditions by transporting O2 to tissues

45
Q

What is translocation?

A

Organic compounds are transported in the phloem from sources to sinks (tissues that need them)

46
Q

Assimilates are also transported, what are they? give an example

A

Products of photosynthesis that are transported

E.g. sucrose

47
Q

What are the three main sources of assimilates?

A
  • Green leaves and stems
  • storage organs
  • food stores in seeds when they germinate
48
Q

What are the main sinks in a plant?

A
  • Roots that are growing/actively absorbing mineral irons
  • meristems actively dividing
  • parts that are laying down food stores
49
Q

Describe phloem loading

A

Soluble products are moved in by active process
(Apoplast route)
Soluble products travel through: cell walls, intercell-to companion cells and sieve elements
Sucrose increase causes water to move in, turgor pressure increases
Water carrying the assimilates moves into tubes of sieve elements to reduce pressure (Up/down by mass flow to areas of lower pressure)

50
Q

What happens in the companion cells during phloem loading?

A

Hydrogen ions are pumped out of companion cells using ATP
Hydrogen ions are returned (down a concentration gradient) via cotransport protein, sucrose is the molecule being cotransported
Sucrose concentration increases in companion cells and sieve elements

51
Q

How are companion cells adapted to help with translocation?

A
  • infoldings large SA:V for active transport

- many mitochondria for transport pumps

52
Q

Describe phloem unloading

A

At any point into cells that need it (diffusion)

Sucrose may be converted into starch (to maintain concentration gradient)

53
Q

What does the loss of solutes mean in translocation?

A

-Rise in water potential so water moves out into transpiration stream in xylem

Biology Module 3 (3 decks)

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