Lecture 9: Leaf

Question 1

What is the stipule

Answer 1

protective leaf-like appendage at the base of the leaf

Question 2

What is the petiole

Answer 2

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

Question 3

What do you call a leaf with no petiole

Answer 3

sessile

Question 4

What is the lamina?

Answer 4

leaf blade

Question 5

What is a simple leaf?

Answer 5

an undivided leaf lamina (may be deeply lobed)

Question 6

What is a compound leaf?

Answer 6

lamina is divided into leaflets

Question 7

What are the two types of simple leaf?

Answer 7

entire margin

lobed margin

Question 8

What are the two types of compound leaf?

Answer 8

pinnate

palmate

Question 9

Define pinnate

Answer 9

leaflets borne on central rachis

Question 10

What does rachis mean?

Answer 10

stem of plant

Question 11

Define palmate

Answer 11

leaflets borne on top of petiole

Question 12

What are the differences between leaflets and leaves?

Answer 12

• 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

Question 13

What kind of venation do dicot leaves have?

Answer 13

netted venation

Question 14

What kind of venation do monocot leaves have?

Answer 14

parallel venation

Question 15

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

Answer 15

true

Question 16

What does phyllotaxis mean?

Answer 16

arrangement of leaves around a stem

Question 17

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

Answer 17

5
spiral
alternate
opposite
decussate
whorled

Question 18

What does spiral phyllotaxis mean?

Answer 18

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

Question 19

Why is the spiral arrangement more beneficial than other plants?

Answer 19

maximizes light interception, minimizes self- shading

Question 20

Describe alternate phyllotaxis

Answer 20

successive leaves are 180 degrees apart

Question 21

Describe opposite phyllotaxis

Answer 21

a pair of opposite leaves is formed at each node

Question 22

Describe Decussate

Answer 22

successive pairs of leaves are 90 degrees apart eg. mint

Question 23

Describe whorled

Answer 23

three or more leaves formed at each node

Question 24

Where is the leaf primordia initiated from

Answer 24

the shoot apical meristem

Question 25

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

Answer 25

tunica | corpus

Question 26

What does tunica mean

Answer 26

(outer layer) - cells usually divide anticlinally

Question 27

What does corpus mean

Answer 27

(inner layers)- cells divide in all direction

Question 28

Where are leaves derived from?

Answer 28

the founder cells in the peripheral zone

Question 29

When does cell division in a leaf stop?

Answer 29

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

Question 30

Where does the leaf stop divided first

Answer 30

- the tip first | - the base last

Question 31

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

Answer 31

true

Question 32

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

Answer 32

upper epidermis palisade mesophyll spongy mesophyll lower epidermis

Question 33

What are mesophytes

Answer 33

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

Question 34

Describe the epidermis

Answer 34

- on upper and lower sides - lack chlorophyll - trichomes - stomata especially on the lower surface

Question 35

Describe the palisade mesophyll

Answer 35

- long, narrow cells - sometimes branched - near upper surface of leaf (adaxial) - rich in chlorophyll - specializes in photosynthesis

Question 36

Describe spongy mesophyll

Answer 36

- first leaf cells to stop dividing - irregular shapes - large air spaces - chlorophyll

Question 37

What are vascular bundles

Answer 37

- xylem above phloem | - collenchyma and/or sclerenchyma may provide support

Question 38

What is used in garlic

Answer 38

bublets

Question 39

What is used in mustard

Answer 39

seed

Question 40

What is used in celery

Answer 40

fruit

Question 41

What is used in cumin

Answer 41

leaves and fruits

Question 42

What is used in bay leaves

Answer 42

leaves

Question 43

What is used in basil

Answer 43

leaves

Question 44

What is the effect of variation in leaf structure

Answer 44

- enhance their competitive performance

Question 45

What are the benefits of coiled organs?

Answer 45

they coil rapidly in response to contact stimuli

Question 46

What are the characteristics of shade plants

Answer 46

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

Question 47

Describe the features of xerophytes

Answer 47

- thick cuticle - hairs - recessed stomata - hypodermis - well developed palisade mesophyll - inclined leaves - solar tracking

Question 48

purpose of thick cuticle of x

Answer 48

reflects sunlight

Question 49

purpose of hairs of x

Answer 49

reduce water loss

Question 50

recessed stomata purpose of x

Answer 50

reduce transpiration

Question 51

purpose of hypodermia of x

Answer 51

reduce wilting injury

Question 52

purpose of well developed palisade mesophyll of x

Answer 52

optimise light use

Question 53

purpose of inclined leaves of x

Answer 53

lower temperature

Question 54

purpose of solar tracking of x

Answer 54

avoid intense sunlight

Question 55

What does rubisco do?

Answer 55

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

Question 56

How much O2 in atm

Answer 56

21%

Question 57

how much N2 in atm

Answer 57

78%

Question 58

how much CO2 in atm

Answer 58

0.036%

Question 59

What is photorespiration

Answer 59

- O2 substitutes for CO2 in the active site of the enzyme rubisco - the photosynthetic rate is reduced

Question 60

What happens to plants on hot, dry, days

Answer 60

plants close their stomata - conserving water but limiting access to CO2 - causing oxygen to build up

Question 61

What is the alternative carbon fixation in hot, arid climates

Answer 61

- 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

Question 62

What happens in C4 plants; spatial separation

Answer 62

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

Question 63

What happens in CAM plants

Answer 63

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