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OCR A Level Biology > Module 3.3 Transplant In Plants > Flashcards

Module 3.3 Transplant In Plants Flashcards

1
Q

Why do plants need a transport system

A

Plants are multicellular organism
They have a high metabolic rate
Plants have a small surface area to volume ration
Rate of diffusion would be slow because of large distance

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2
Q

Can you draw the cross section of a vascular section in the root

A
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3
Q

Can you draw cross section of vascular bundle in a stem

A
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4
Q

Can you draw the cross section of a vascular bundle in a leaf

A
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5
Q

What is the function of the xylem vessels

A

To transport water up the plant
Supports the plants (lignin)

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6
Q

What the the function of the phloem

A

To transport assimilates from source to sink

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7
Q

What features does the xylem have

A

It is hollow,
there are no end walls,
contains dead cells,
contains lignin,
has pits
Also has a ring or spiral structure for flexibility

Also has xylem parenchyma which stores food also contains tanin which prevents herbivores from eating the xylem

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8
Q

State the function of lignin in the xylem and explain why it’s important

A

It also helps strength the cell

How?

prevents walls from collapsing when there is low turgor pressure.

Spiral band of lignin is flexible

Also helps reduce loss of water

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9
Q

State the function of bordered pits

A

Reason

is to allow water to go out of the xylem

Why?

so tissues can be supplied with water.

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10
Q

What substances are transported in the xylem vessel

A

Water and minerals

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11
Q

What three parts of phloem tissue

A

Phloem paracheyma
Sieve tube elements
Companion cells

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12
Q

What is the function of sieve tube elements

A

Living cells which form tube for transporting sugars.

They have holes which allow solutes to pass through

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13
Q

What is the function of companion cells

A

Carry out living functions for themselves and sieve tube elements.

For example provide energy for active transport of solutes

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14
Q

What is meant by the term source?

A

Where assimilâtes are loaded into to the phloem

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15
Q

What is meant by the term sink

A

Where assimilates unload

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16
Q

Exam Question

When a bark is removed from a tree, the phloem was removed. If a complete ring of bark is removed, the tree trunk will swell above the cut

Suggests two reason why

A

Sugar cannot pass where it’s been cut

So…

This decreases water potential and the water moves into the cells.

Another answer could be

The damage causes cell division, so it can produce cells to store sugar

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17
Q

What is a dicotyledonous plant

A

A plant that has seeds made out of two parts

18
Q

What two ways can water move through the plant

A

Symplast
Apoplast

19
Q

Describe the apoplast pathway

A

At first the water goes through this pathway

  • water is absorbed into cell wall
  • travels through cortex (non living parts)
  • via mass flow from high hydrostatic pressure to a low hydrostatic pressure
20
Q

Describe the symplast pathway

A

Through living parts of the cell

  1. Water moves in through osmosis into the roots
  2. Moves through the cytoplasm and plasdostomata
21
Q

Why do plants have a casparian strip

A

Forces water to move through plasma membrane
So what goes in is selected and others will be filtered out

22
Q

How does the water get loaded into the xylem

A

1- endodermis moves mineral ions into xylem first through active transport
2- this decreases wp in xylem
3- so water will move into xylem through osmosis down wp gradient
4- generates root pressure which pushes water up xylem

23
Q

Define transpiration

A

Loss of water vapour by evaporation through the stomata

24
Q

What are the benefits and the opposite of benefit of transpiration

A
  1. Cools plant down
  2. Causes a transpiration stream (movement of water and minerals ions up the stem)

Downside
1. May cause loss of water, which means less turgor pressure, so plant will wilt

25
Q

What factors affect transpiration

A

Temp
Humidity
Wind speed
Light intensity

26
Q

How does temperature affect transpiration

A

The water molecules have more KE so they vibrate more,
Makes it easier for water to evaporate from leaf
Wp inside the leaf increases making water diffuse of leaf

27
Q

How does humidity affect transpiration

A

As humidity increases the rate of transpiration decreases

More humid the more water vapour there in the air (the air is moister)
Decreases wp gradient between leaf and air

28
Q

How does wind affect transpiration rate

A

Increases rate of transpiration

Water molecules will be blown away from the stomata Increases water potential gradient
So faster rate of transpiration

29
Q

How does light intensity affect the rate of transpiration

A

More stomata will open
So greater photosynthesis
More CO2 means more gas exchange happens
So rate of transpiration increases

30
Q

What does a potomètre measure

A

Measures water uptake by plant by estimating transpiration rate

31
Q

How is water used up in plants

A

Turgor pressure
Photosynthesis

That’s why a potomètre is gives an estimation

32
Q

…………..

A

………….

33
Q

Define translocation

A

Movement of assimilâtes from source to sink

34
Q

Why do plants use sucrose instead of glucose

A

Glucose can react
Can change wp of cells
Sucrose is big

35
Q

How does phloem loading work

A
  1. H+ pumped out of companion cell through H+ pumps by active transport
  2. Which increases H+ concentration is in outside cell
  3. H+ wants to diffuse back into companion cell, so it’s gets co transported into Compnaian cell with sucrose
  4. Sucrose diffuses from companion cell into sieve tube element
  5. Which decreases wp inside sieve tube element
  6. Water moves into sieve tube element by osmosis which generates turgor pressure for mass flow
36
Q

How does mass flow work

A
  1. Water has a high turgor pressure at source
  2. This flows down from source to sink down the pressure gradient
37
Q

How does phloem unloading work

A
  1. Sucrose diffuses from phloem into sink
  2. Sucrose moves into cells which maintains concentration gradient between cells and phloem
  3. Loss of assimilates increases wp in the sieve tube element
    H20 moves into cells via osmosis or enters xylem
38
Q

What is a xérophytes

A

Plants like cacti which are adapted to live in dry environments
So their adaptions prevent them from losing water

39
Q

Examples of xerophytes

Cacti

A

Thick waxy cuticle: reduces water loss by evaporation

Spines instead of leaves: reduces SA for water loss

Close their stomata: during the hottest time of the day when transpiration rates are high

Green stem: stem has lost of chlorophyll as cacti don’t have leaves

Shallow widespread roots: take advantage of an water

Fleshy stem: store water as they are ribbed so stem expands when there’s water

40
Q

Examples of xerophytes

Marram grass

A

Sunken stomata in pits: sheltered from wind. Also can trap air in pits with help slow transpiration down

Hairs on epidermis: traps air around stomata which reduces wp between leaf and air

Roll up their leaves: in hot or windy conditions to trap air and to reduce SA

Thick wavy cuticle: to prevent water loss from epidermis

Dense spongy mesophyll: leaves fewer air spaces so less SA for diffusion

Tap root: grow vertically specialised for food storage

41
Q

What is a hydrophyte

A

A plant that grows in water that need adaptions to cope with oxygen levels

42
Q

Hydrophytes adaptions

Lillies,

A

Large flat leaves: contain air spaces which make them float, helps increase SA so they can absorb more sunlight

Open stomata on upper epidermis: exposed for efficient gas exchange as it’s hard to get air in water

Large air spaces: help plant float, act as store for oxygen, float on surface to obtain more light for photosynthesis

Small roots: Roots needed for anchorage not to absorb minerals

Thin or no wavy cuticle: don’t need them, they’re already in water

OCR A Level Biology (24 decks)

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