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flowering > leaves > Flashcards

leaves Flashcards

1
Q

three ecological types of plants

A

mesophytes
xerophytes
hydrophytes

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2
Q

mesophytes

A

require moderate amounts of water

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3
Q

xerophytes

A

adapted to low levels of water

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4
Q

hydrophytes

A

adapted to high levels of water

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5
Q

eudicots leaves in sun vs shade

A
  • in sun leaves have denser palisade
    -shade have thinner less dense palisade
    ex of phenotypic plasticity
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6
Q

major veins

A
  • may have a bundle sheath of parenchyma (largest do not)
  • these veins have less exit/entry from the mesophyll
  • serve more as a transport function in/out of leaf
  • sometimes may undergo limited amount of secondary growth
  • also may have bundle extensions of collenchyma for support
  • some species move water to the epidermis by bundle extensions
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7
Q

minor veins

A
  • often lack bundle extensions
  • always have a bundle sheath with few chloroplasts
  • little space between bundle sheath cells
  • helps control exit/entry to veins
  • large degree of control because of large number of minor veins
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8
Q

netted (reticulate) venation

A

in a typical eudicot leaf

-mesophyll divided into subregions called areoles

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9
Q

a paradermal secttion

A
  • dense packing of the palisade mesophyll
  • vein network
  • more air spaces in spongy mesophyll
  • stomatal density of adaxial and abaxial differs
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10
Q

vascular tissue

A
  • bundle sheath is part of vascular tissue
  • xylem and phloem similar in c3 and c4 grass leaves
  • larger veins resemble stem bundles - have vessel elements, tracheids, parenchyma and a protoxylem lacuna
  • minor veins generally have few tracheids, and no vessels
  • sieve tube members and companion cells phloem
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11
Q

evergreen angiosperm leaves

A
  • some woody eudicots retain leaves year round
  • called broad-leaved evergreens
  • grow in low nutrient status habitats
  • slow growers and stress tolerators
  • plants conserve organs as some nutrients not salvageable but must be frost hardy and xerophytic (cold causes xerophytic things )
  • tolerant of ice crystal formation within tissues, not cells (a tolerance of all temperate woody species)
  • particularly found in ericaceae
  • ericoid describes general leaf morphology
  • example of convergent evolution
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12
Q

different leaf habitat

A

stays on plant of the winter

  • leaf said to be wintergreen = not true evergreen
  • turns red/purple in late fall
  • leaves senesce in spring
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13
Q

leaf abscission

A
  • controlled shedding of leaves
  • important in woody species ie. perennials
  • occurs yearly in deciduous species
  • or at longer intervals for evergreens
  • regulated by hormones
  • leaves drop in response to environmental cues
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14
Q

steps of leaf abscission

A
  1. environmental signal
  2. retrieval
  3. abscission layer formation
  4. protective layer formation
  5. vascular disconnection
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15
Q

environmental signal

A

Photoperiod more reliable
Temperature can also influence
Warm temperatures in fall can inhibit onset, especially in non-native species

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16
Q

retrieval

A

Plant recovers as many soluble nutrients as possible eg. Mg+2, sugars, amino acids
Stores in parenchyma in stem
Some minerals not mobile
ie. not retrievable eg. Ca+2

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17
Q

abscission layer formation

A

New thin-walled parenchyma cells form at base of petiole
From dedifferentiating parenchyma
Cell walls of pre-existing cells also begin breaking down here
Forms an even break line

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18
Q

protective layer formation

A

Another layer forms to the inside of the abscission layer
Is suberized to prevent or minimize water loss and pathogen entry
Creates a leaf scar on the stem

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19
Q

vascular disconnection

A 
Vessels in midrib of petiole still open 
Leaf may hang on for a time
Nearby xylem parenchyma produce outgrowths that enter pits of vessel
Is to seal off vessels
Outgrowths called tyloses
Can see bundle scars within leaf scars
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20
Q

fall colors in deciduous leaves

A

A shorter photoperiod and cooler temperatures initiate leaf fall
Chlorophyll broken down by light all summer, but is not replenished in fall
Fat soluble carotenoids more resistant
In some species, water soluble anthocyanins are produced de novo in vacuole
Other plants always contain anthocyanins
Anthocyanins are increased with cold nights and sunny days

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21
Q

morphology

A
  • major ps organ
  • important for other metabolic functions like synthesis of amino acids and secondary metabolites
  • most variable organ in form and anatomy
  • different environments have differing selection pressures
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22
Q

blade/lamina

A

-flattened portion

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23
Q

petiole

A

leaf stalk

24
Q

sessile

A

no petiole

25
Q

stipules

A

base of leaf

26
Q

exstipulate

A

if no stipule

27
Q

in most monocots the base of blade is

A

enlarges and forms a sheath around the stem

28
Q

axillary bud

A

in axil

29
Q

simple leaf

A

blade on surface

30
Q

compound leaf

A

blade subdivided into leaflets

31
Q

pinnately compound

A

leaflets off a rachis

32
Q

palmately compound

A

leaflets off the tip of petiole

-may also have petiolules

33
Q

margins

A

page 38

34
Q

leaf base in grasses

A
  • grass leave have sheathing base
  • extends down stem
  • has meristematic regions at base of leaf
  • ligule is membrane or hairy fringe at collar
  • ligule can have extensions called auricles
35
Q

leafs and branches

A

both can have a central axis bearing leaf like structures

36
Q

reliable criteia

A
  • is there a SAM
  • presence of axillary buds (or stipules for some)
  • plane of leaves
37
Q

is there a SAM

A
  • branch has SAM, but not leaf

- reflects indeterminate status of branch versus determinate leaf dimensions

38
Q

presence of axillary buds

A

-in the axil of all simple leaves but not of leaflets

39
Q

plane of leaves

A
  • leaflets lie in same plane

- different leaves on branch are usually in different planes

40
Q

phyllotaxy

A

patterns of leaf arrangment

  1. alternate is 1 leaf per node
  2. opposite is 2 leaves per node
  3. whorled is 3 or more leaves per node
41
Q

alternate

A

most common subtype of alternate is spiral/helical

42
Q

opposite

A

if each successive pair is at right angles to the next them it is termed decussate

43
Q

whorled

A

a rosette is a dense cluster of leaves, really a spiral arrangement without internodal elongation

44
Q

which leaf pattern most common

A

helical

45
Q

the smaller the angle

A

the more files of leaves possible but still minimizing overlap

  • rosette has small angle
  • selected for light limiting habitats
46
Q

distichous pattern allows much

A

overlap

  • feasible in a hight light habitat
  • allows for the increased packing of shoots in a crowded area
47
Q

leaf limitations

A

Must access CO2 but H2O exits as C02 enters
Compromises in form therefore essential
Flat, 2-D shape facilitates light capture, gas exchange
But, this shape also exacerbates desiccation risk
So, leaf success in differing habitats involves a combination of anatomy and morphology in concert with physiology and stomatal opening/closing

48
Q

why leaf morphology

Page 48)

A

Leaf features used greatly in plant identification (also floral morphology)
Shape and size of leaves varies with habitat
Water availability especially influences leaf morphology
Smaller leaves tend to be found in hotter and drier habitats
Usually less divided in shape
Larger leaves tend to be found in moister habitats
Also more divided in shape
Submerged plants often have highly divided leaves
A greater surface area is beneficial because the entire leaf surface takes up gases from the water

49
Q

heterophylly

A
  • leaves on one plant can differ in form and function
  • eg. submerged versus floating leaves of some aquatic angiosperms
  • reflects phenotypic plasticity
  • responding to greatly differing microhabitats
50
Q

leaf development

A

Patterns of leaf development observed by analyzing genetic mosaics called chimeras
Causes layers of cells of differing genetic composition
Leaves arise from peripheral meristem as leaf primordia
First apparent as a bulge on side of SAM
Bulge called a leaf buttress
Flanking bulges produce opposite leaves eg. Coleus
Primary meristems later visible in the primordium
Cells differentiate as primordia are displaced by continued growth
Bud primordia develop in the axils of leaf primordia

51
Q

when buttresses get larger they are called

A

bud primordium

52
Q

grass leaf development

A

Exhibit basal growth
SAM remains basal in vegetative phase
Leaf primordia appear as hood-like structures
These enfold the SAM and alternate sides
These leaves retain a meristematic zone at the base of leaf
Cell elongation after cell divisions causes leaves to increase in size

53
Q

vascular differentiaion

A

1 priority, as it is critical for leaf development

Need to establish long distance source of energy
eg. From starch stored in cortex of stem or root
Major leaf veins differentiate from stem bundles into the leaf (still primordial)
But, minor veins differentiate from tip back towards the base of leaf
Also, major veins differentiate from mid-regions towards leaf margins
But, minor veins begin at leaf margins and develop inwards
Means a completed network of veins is first present towards the tip of a leaf, and not the base
Oldest part of a leaf is the tip

54
Q

differentiation in eudicot leaves

A
  • three leaf traces per leaf
  • each from a different stem bundle
  • leaves die from tip back
55
Q

grass leaves differentiation

A

Because grass leaves retain meristematic zone at base
Vascular differentiation originates in mid-portion of blade
Major veins (parallel) differentiate back to base AND up to tip
Minor veins (cross) differentiate back from tip

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