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Biology AS > Exchange and Mass Transport - Plants > Flashcards

Exchange and Mass Transport - Plants Flashcards

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1
Q
A
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2
Q

What is the order of layers in a plant leaf cell?

(top to bottom)

A

Waxy Cuticle

Upper Epidermis

Palisade Mesophyll

Spongy Mesophyll and Vascular Bundle

Lower Epidermis

Waxy Cuticle

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3
Q

What is the function of the waxy cuticle?

A

contains lipids so waterproofs the leaf to prevent water loss

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4
Q

What is the function of the upper epidermis?

A

To provide an extra layer of protection and contains a few stomata for gas exchange

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5
Q

What is the function of the palisade mesophyll?

A

Main site of photosynthesis

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6
Q

What is the function of spongy mesophyll?

A

Increases the surface area of the leaf for efficient gas exchange

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7
Q

What is the function of the vascular bundle?

A

Transport of minerals and water (phloem and xylem)

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8
Q

What is the function of the lower epidermis?

A

Adds an extra layer of protection and has more stomata to allow for gas exchange

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9
Q

Why does the lower epidermis contain more stomata than the upper epidermis?

A

The underside of a leaf is cooler, so less water is lost by evaporation.

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10
Q

What is each stomata surrounded by?

A

2 guard cells

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11
Q

How and why does a guard cell close?

A

To conserve water:

K+ ions diffuse into cell when it is turgid

Water potential inside of cell increases

Cell becomes flaccid and less curved

Stomata pore closes, reducing airflow and transpiration

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12
Q

How and why does a guard cell open?

A

To lose water and allow for gas exchange:

K+ ions diffuse out of cell when it is flaccid

Water potential inside cell decreases

Cell becomes turgid and more curved

Stomata pore opens, increasing airflow and transpiration

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13
Q

What happens to the concentrations of CO2 and O2 when photosynthesis is taking place?

A

CO2 conc decreases

O2 conc increases

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14
Q

What happens to the concentrations of CO2 and O2 when respiration is taking place?

A

CO2 increases

O2 decreases

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15
Q

Define a xerophyte

A

Plants adapted to dry habitats

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16
Q

What are the adaptations of cacti to warm environments?

A
  1. Being as thin as vertically possible
  2. Roots spread sideways not downwards
  3. Spines formed by rolled leaves
  4. Fuz between spines
  5. Projections from the main body
17
Q

How does being thin vertically help a cactus?

A

It allows the cactus to catch as little sunlight as possible, keeping it cooler.

18
Q

Why do the roots spread sideways in cacti?

A

When it rains, the roots can catch as much water as possible

19
Q

What are the advantages of spines on cacti?

A
  1. Produces their own microclimate inside the leaf - the water gets trapped inside the leaf which decreases transpiration
  2. They can concentrate to provide protection from the sun
  3. Reduced SA:V
20
Q

What are the advantages of cacti having fuz between their spines?

A
  1. Protection from the sun
  2. Captures water in mists / rain
21
Q

What are the advantages of cacti having projections from the main stem?

A

Only a few at a time will catch the sun, allowing the rest of the plant to be in the shade

22
Q

What is the function of xylem?

A

to transport water and ions up the plant

23
Q

What is the structure of xylem vessels?

A

narrow tubes consisting of dead, empty cells

cells have no end walls

walls strengthened by lignin

24
Q

What features of a xylem vessel reduces resistance?

A

empty, dead cells

no end walls

25
Q

What is cohesion?

A

a force resulting from attraction between molecules of the same substance

26
Q

What is adhesion?

A

a force resulting from attraction between molecules of different substances

27
Q

Where is adhesion found in xylem vessels?

A

between water molecules and the sides of the xylem

28
Q

What is the cohesion tension theory?

A

water is drawn out of xylem vessels, developing tension and a water potential gradient

water is drawn up the xylem in a continous column due to cohesive forces

adhesive forces prevents water dropping under gravity

this mechanism is called the transpiration pull

Biology AS (17 decks)

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