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Biosci 102 Plant structure and function > Lecture 9: Leaf > Flashcards

Lecture 9: Leaf Flashcards

1
Q

What is the stipule

A

protective leaf-like appendage at the base of the leaf

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2
Q

What is the petiole

A

the stalk of a leaf. When there is no petiole, the leaf is SESSILE

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3
Q

What do you call a leaf with no petiole

A

sessile

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4
Q

What is the lamina?

A

leaf blade

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5
Q

What is a simple leaf?

A

an undivided leaf lamina (may be deeply lobed)

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6
Q

What is a compound leaf?

A

lamina is divided into leaflets

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7
Q

What are the two types of simple leaf?

A

entire margin

lobed margin

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8
Q

What are the two types of compound leaf?

A

pinnate

palmate

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9
Q

Define pinnate

A

leaflets borne on central rachis

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10
Q

What does rachis mean?

A

stem of plant

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11
Q

Define palmate

A

leaflets borne on top of petiole

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12
Q

What are the differences between leaflets and leaves?

A
  • buds are found at the axils of leaves; but not on leaflets

- leaves extend from stem in various plants; leaflets lie on the same plane

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13
Q

What kind of venation do dicot leaves have?

A

netted venation

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14
Q

What kind of venation do monocot leaves have?

A

parallel venation

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15
Q

true or false; monocot leaves have a sheath surrounding the stem

A

true

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16
Q

What does phyllotaxis mean?

A

arrangement of leaves around a stem

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17
Q

how many types of phyllotaxis are there; and name them all

A 
5
spiral
alternate
opposite
decussate
whorled
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18
Q

What does spiral phyllotaxis mean?

A
  • most common arrangement
  • leaves are 137.5 degrees apart (2.6 leaves/360 degrees)
  • this is the ideal angle
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19
Q

Why is the spiral arrangement more beneficial than other plants?

A

maximizes light interception, minimizes self- shading

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20
Q

Describe alternate phyllotaxis

A

successive leaves are 180 degrees apart

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21
Q

Describe opposite phyllotaxis

A

a pair of opposite leaves is formed at each node

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22
Q

Describe Decussate

A

successive pairs of leaves are 90 degrees apart eg. mint

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23
Q

Describe whorled

A

three or more leaves formed at each node

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24
Q

Where is the leaf primordia initiated from

A

the shoot apical meristem

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25
Q

What are the two zones of shoot apical meristem (SAM)

A

tunica

corpus

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26
Q

What does tunica mean

A

(outer layer) - cells usually divide anticlinally

27
Q

What does corpus mean

A

(inner layers)- cells divide in all direction

28
Q

Where are leaves derived from?

A

the founder cells in the peripheral zone

29
Q

When does cell division in a leaf stop?

A

when the leaf is very small eg. 10% final length

30
Q

Where does the leaf stop divided first

A
  • the tip first

- the base last

31
Q

true or false; the tip of the leaf differentiates before the base

A

true

32
Q

What is the structure of a typical leaf; from adaxial to abaxial

A

upper epidermis
palisade mesophyll
spongy mesophyll
lower epidermis

33
Q

What are mesophytes

A

plants that require a weather that is neither too hot nor too dry

34
Q

Describe the epidermis

A
  • on upper and lower sides
  • lack chlorophyll
  • trichomes
  • stomata especially on the lower surface
35
Q

Describe the palisade mesophyll

A
  • long, narrow cells
  • sometimes branched
  • near upper surface of leaf (adaxial)
  • rich in chlorophyll
  • specializes in photosynthesis
36
Q

Describe spongy mesophyll

A
  • first leaf cells to stop dividing
  • irregular shapes
  • large air spaces
  • chlorophyll
37
Q

What are vascular bundles

A
  • xylem above phloem

- collenchyma and/or sclerenchyma may provide support

38
Q

What is used in garlic

A

bublets

39
Q

What is used in mustard

A

seed

40
Q

What is used in celery

A

fruit

41
Q

What is used in cumin

A

leaves and fruits

42
Q

What is used in bay leaves

A

leaves

43
Q

What is used in basil

A

leaves

44
Q

What is the effect of variation in leaf structure

A
  • enhance their competitive performance
45
Q

What are the benefits of coiled organs?

A

they coil rapidly in response to contact stimuli

46
Q

What are the characteristics of shade plants

A
  • thin leaves
  • chloroplasts in epidermis
  • poorly developed palisade mesophyll
  • low chlorphyll a:b ratio (more b)
  • undulated epidermal cells
  • anthocyanins on undersurfaces
47
Q

Describe the features of xerophytes

A
  • thick cuticle
  • hairs
  • recessed stomata
  • hypodermis
  • well developed palisade mesophyll
  • inclined leaves
  • solar tracking
48
Q

purpose of thick cuticle of x

A

reflects sunlight

49
Q

purpose of hairs of x

A

reduce water loss

50
Q

recessed stomata purpose of x

A

reduce transpiration

51
Q

purpose of hypodermia of x

A

reduce wilting injury

52
Q

purpose of well developed palisade mesophyll of x

A

optimise light use

53
Q

purpose of inclined leaves of x

A

lower temperature

54
Q

purpose of solar tracking of x

A

avoid intense sunlight

55
Q

What does rubisco do?

A

evolved under low o2 conditions
binds both CO2 and O2
photorespiration (if O2 is bound)

56
Q

How much O2 in atm

A

21%

57
Q

how much N2 in atm

A

78%

58
Q

how much CO2 in atm

A

0.036%

59
Q

What is photorespiration

A
  • O2 substitutes for CO2 in the active site of the enzyme rubisco
  • the photosynthetic rate is reduced
60
Q

What happens to plants on hot, dry, days

A

plants close their stomata

  • conserving water but limiting access to CO2
  • causing oxygen to build up
61
Q

What is the alternative carbon fixation in hot, arid climates

A
  • by incorporating CO2 into four carbon compounds in mesophyll cells
  • these four carbon compounds are exported to bundle sheath cells, where they release CO2 used in the Calvin Cycle
62
Q

What happens in C4 plants; spatial separation

A

in C4 plants carbon fixation and the Calvin cycle occur in different types of cells

63
Q

What happens in CAM plants

A

carbon fixation and the calvin cycle occur at the same cells at different times

Biosci 102 Plant structure and function (9 decks)

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