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HORT 1102 - Botany > 8: Leaf Anatomy & Organ Modifications > Flashcards

8: Leaf Anatomy & Organ Modifications Flashcards

1
Q

What are the two outer layers of a dicot leaf called?

A

Upper epidermis and lower epidermis

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2
Q

What are the tissues within the two epidermal layers of a dicot leaf called?

A

Mesophyll tissues:

  1. Palisade mesophyll
  2. Spongy mesophyll
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3
Q

Describe the palisade mesophyll tissue and where it is located

A

thin walled, long parenchyma cells tightly arranged like a palisade (fence/stakes) in one or two layers nearest to the upper epidermis of dicot leaves
- contain chloroplast

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4
Q

Describe the spongy mesophyll tissue and where it is located

A
  • parenchyma cells
  • near the lower epidermis of a dicot leaf
  • shorter, wider cells that are loosely packed with lots of air spaces
  • contain chloroplast
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5
Q

Describe the upper epidermis in dicot leaves

A
  • transparent cells
  • covered by waxy cuticle
  • does not usually contain stomata
  • no chloroplasts
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6
Q

Describe the lower epidermis in dicot leaves

A
  • transparent
  • waxy cuticle covers it
  • guard cells located here which contain chloroplast
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7
Q

Describe guard cells

A

Part of the collective term: stomata

  • contain chloroplasts to generate energy
  • swell up or shrink to open/close the stoma depending on water flow
  • found in the lower epidermis of dicot leaves and both epidermal layers in monocot leaves
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8
Q

Describe stoma

A
  • The opening in the waxy cuticle of the epidermis
  • surrounded by guard cells
  • the site of gas exchange
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9
Q

Describe leaf veins

A

the vascular bundles that contain xylem on the top and phloem on the bottom

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10
Q

Describe bundle sheath

A

The ring of cells that surround the vascular bundles in the leaf

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11
Q

Describe air spaces

A

The space between cells throughout the leaf where gas exchange occurs

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12
Q

What is the main vein called in a dicot leaf with netted venation?

A

Midrib

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13
Q

How are the minor veins of a dicot leaf with netted venation arranged?

A

They branch off the main vein/midrib throughout the leaf tissue

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14
Q

What are 4 leaf adaptations for hot, sunny, arid conditions?

A
  1. thick waxy cuticle for water retention
  2. two full layers of palisade mesophyll with lots of chloroplasts
  3. leaf is thick
  4. sunken stomata
  5. hypodermis protects from UV damage
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15
Q

What are 4 leaf adaptations for shady conditions?

A
  1. wider, thinner leaves for larger surface area for sun collection
  2. one layer of palisade mesophyll that’s not super tightly packed
  3. spongy mesophyll very loosely packed - lots of air space
  4. mesophyll tissues have less chloroplasts
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16
Q

Describe leaf gap

A

When the continuity of the vascular bundle going vertically up the stem is broken by the growth of a leaf petiole a gap forms so the vascular bundle can go into the leaf

  • this also occurs with buds and is called bud gaps
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17
Q

Describe abscission and the steps

A

The process of leaves dropping from deciduous trees (ex. in temperate climates in the fall)

  1. after the chloroplast has been taken back into the stem, a gap will open up between the petiole cells and the main stem of the plan as the cells break away
  2. on the stem side, suberin gets pumped into the cells to seal them and form the leaf scar
  3. vascular tissues are the last part of the leaf holding it to the stem and eventually the wind will blow it off leaving a leaf scar that will be protected and sealed by suberin
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18
Q

During abscission, what is the layer of cells called that is on the stem side of the plant?

A

Protection layer

it secretes suberin to coat and protect the exposed cells while the petiole is breaking away and prevent water loss

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19
Q

During abscission, what is the layer of cells called that is on the petiole side of the plant?

A

Separation layer

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20
Q

In a monocot leaf, where are the upper and lower epidermis located?

A

Upper epidermis is on the inside of the V

Lower epidermis is on the underside of the V

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21
Q

T or F: Monocot leaves have both palisade and spongy mesophyll tissues

A

FALSE. Only contain spongy mesophyll leaves

22
Q

Describe bulliform cells

A

cells specific to monocot leaves that are located near the midrib

structure is like an accordion that swells up with water and pushes the grass blade open to create a flatter surface and will pull the blades in closer and curl up when dry

23
Q

T or F: Stomata can occur on the upper and lower epidermis of a monocot leaf?

A

TRUE

24
Q

Describe bundle sheath extensions

A

Common in monocot leaves

- cells that run right from the sheath to the epidermal surface to help stiffen the plant in upward growth

25
Q

What environmental conditions trigger a stoma to open/guard cells to become turgid?

A

Daylight triggers the stoma to open as water will flow into the guard cells and make them turgid

also moisture

26
Q

What environmental conditions trigger a stoma to close/guard cells to become flaccid?

A

Darkness will trigger the stoma to close as water will leave the guard cells and they will become flaccid and close the stoma

also drought

27
Q

Describe trichomes

A

Leaf hairs that aid in water loss as they interrupt the air flow on the leaf surface

28
Q

T or F: the conifer needle is an adapted leaf for living in dry or arid conditions

A

True

29
Q

What 3 adaptations does the conifer needle have?

A
  1. Thick cuticle to prevent water loss
  2. Sunken stomata
  3. Hypodermis layer and an endodermis containing suberin
30
Q

Describe hypodermis. Which leaves have this adaptation?

A

A layer of thick collenchyma cells beneath the epidermis that protects from UV damage.

Conifer needles have this

31
Q

Describe resin ducts. which leaves have this adaptation?

A

Resin is a defensive compound to repair or coat a wound if a plant gets injured. It is also a feeding deterrent

conifer needles have this

32
Q

What is the purpose of a sunken stomata?

A

Stomata (guard cells and stoma) are recessed into the epidermal surface to create a boundary layer to protect excess water loss

33
Q

T or F: Conifer needles have an endodermis that contains suberin surrounding the vascular tissues?

A

TRUE

34
Q

What are the 10 stem modifications?

A
  1. cladophyll
  2. prickle
  3. stolon/runner
  4. succulent stem
  5. climbing
  6. thorn
  7. bulb
  8. corm
  9. rhizome
  10. tuber
35
Q

Describe cladophyll, provide the function, and give an example

A

A stem modification

Flattened stems to photosynthesize instead of leaves

Function: photosynthesis/nutrient capturing

ex. Christmas cactus

36
Q

Describe prickles, provide the function, and give an example

A

A stem modification

Found randomly on the stem, petioles, and leaves of some plants. Superficially embedded on the stem

Function: protection

ex. roses, salmon berries, etc.

37
Q

Describe stolons/runners, provide the function, and give an example

A

stem modification

an elongates stem that stays above the ground and will root and grow a new plant when a node touches the ground

function: reproduction/propagation
ex. Strawberries, spider plants

38
Q

Describe succulent stems, provide the function, and give an example

A

stem mod

store water and can take over the role of photosynthesis

function: photosynthesis/storage/nutrient capturing
ex. succulents

39
Q

Describe the two climbing stems, provide the function, and give an example

A

modified stem

two kinds:

  1. twining stems: stem twists around an object to climb upwards
    ex. wisteria
  2. Tendrils: coils around something and tightens grip to climb
    ex. hops, quinquefolia
40
Q

Describe thorns, provide the function, and give an example

A

Modified stem

appears ONLY at the nodes and is not superficial like prickles

ex. hawthorns

41
Q

Describe bulbs, provide the function, and give an example

A

modified underground storage stem

The bulb is a bunch of fleshy leaves pushed together
the stem is at the very bottom of the bulb where the roots emerge

ex. tulips, onions

42
Q

Describe corms, provide the function, and give an example

A

Modified vertical underground stem.

Structure:
papery leaves surround the vertical storage stem that is hard and in the centre. The previous year’s corm can be found at the bottom of the structure and is very dense and roots grow.

Function:
storage

Ex. Crocus

43
Q

Describe rhizomes, provide the function, and give an example

A

Modified horizontal storage stem.

Thick, fleshy rhizomes used for storage and propagation (asexual reproduction). The rhizomes can have nodes

ex. ferns, iris

44
Q

Describe tubers, provide the function, and give an example

A

Modified underground storage stem

structure: rounded with ‘eyes’ or nodes and internodes. Filled with parenchyma cells
function: Storage and reproduction

Ex. potatoes

45
Q

What are the 6 leaf medications?

A
  1. carnivorous leaves
  2. bracts
  3. spines
  4. spiny stipules
  5. succulent leaves
  6. tendrils
46
Q

Describe carnivorous leaves, provide the function, and give an example

A

Leaf modification

Cells will lose water rapidly to contract leaves and trap insects inside then secrete a substance to digest the insect

function: captures nutrients
ex. Venus fly trap

47
Q

Describe bracts, provide the function, and give an example

A

Leaf modification

structure: leaf-like appendages found under a flower
function: can be for attracting pollinators
ex. poinsettia (the red is actually the bracts), lilies

48
Q

Describe spines, provide the function, and give an example

A

Leaf modification

spiky modified leaves found on cacti for protection

ex. Cacti

49
Q

Describe spiny stipules, provide the function, and give an example

A

Leaf modification

a pointy appendage at the base of the petiole

function: protection
ex. barberry

50
Q

Describe succulent leaves, provide the function, and give an example

A

Leaf modification

thick, water-filled leaves that are modified for a specific kind of photosynthesis

function: water storage supports drought tolerance; nutrient capturing (photosynthesis)

51
Q

Describe tendrils, provide the function, and give an example

A

Leaf modification

grow off the compound leaves and will wrap around objects with which they come in contact

function: climbing
ex. peas

HORT 1102 - Botany (11 decks)

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