Bio 101: Plant Epidermis

Front 1

Due to the extreme environments plants live in, structures that could adapt evolved.

Back 1

For protection, retention of water, entry restriction of organisms and toxic substances, and strengthening and supporting the plant.

Front 2

Epidermis definition

Back 2

Superficial layer of cells of all parts of the primary plant body, but not found in the root cap and not differentiated as such on apical meristem.

Front 3

Epidermis origin

Back 3

Outermost cell layer of apical meristem/tunica layer (if tunica-corpus present)

Roots: may be related developmentally to cortex or root cap

Front 4

"Protoderm"

Back 4

Undifferentiated epidermis, regardless of origin

Haberlandt's term: "primordial epidermis" or epidermis from separate initials

Front 5

Retains epidermis?

Back 5

Organs with little or no secondary growth.

Front 6

Epidermis with one layer cells in thickness

Back 6

Uniseriate

Front 7

More than one layer cells in thickness; Due to what?; Example.

Back 7

Multiseriate; Periclinal division/unsynchronized division layers; Velamen of orchid plants

Front 8

First protective barrier between aerial surface of plant and environment + principal barrier to movement of water.

Back 8

Cuticle

Note: superficial, but if in terms of cells, epidermis is superficial.

Front 9

General structure of plant cuticle.

Back 9

Epicuticular wax

Cuticle proper

Cuticular layer

Pectin

Cell wall

Front 10

Factors that affect cuticular permeability.

Back 10

Structure and amount of wax

Front 11

2 lipid components of cuticle

Back 11

1. Insoluble cutin - in the matrix

2. Soluble cutin - some at the surface; some in the matrix called cuticular wax

Front 12

Cuticularization

Back 12

Secretion of cutin to surface of cell wall

Front 13

Cutinization

Back 13

Deposition of cutin between cellulose microfibrils of outermost layers, where pectin and hemicellulose may also be present.

Front 14

Distinct region formed by cuticularization; Presence of cellulose?

Back 14

Cuticle proper; No cellulose

Front 15

Distinct region formed by cutinization

Back 15

Cuticular layer

Front 16

Layer under cuticular layers is rich in?; Continuous with?

Back 16

Pectin; middle lamella

Front 17

Structural composition: epidermal cell proper

Back 17

-least specialized, ground mass

-mostly parenchyma cells

-tabular cells

-deficient in chlorophyll (plastids with few grana)

Front 18

Has morphologic variability @ epidermal cell proper

Back 18

Gramineae (grasses)

Front 19

(*) morphologic variability in cells due to?

Back 19

Long cells

Short cells

a.) silica cells - contains silicon dioxide (smaller)

b.) cork cells - suberized walls (larger)

Front 20

Bulliform cells: brief description

Back 20

"bubble-like", thin-walled, highly vacuolated, water containing cells

Front 21

Bulliform cells: walls

Back 21

thin radial walls

outer walls as thick/thicker than those of adjacent ordinary epidermal cells

composed of cellulose and pectic substances

outer walls are cutinized + bear cuticle

Front 22

Bulliform cells: expansion tissues

Back 22

cause rapid expansion of leaf

Front 23

Bulliform cells: motor cells

Back 23

cause changes in turgor in opening/closing movement of leaf

Front 24

Other specialized epidermal cells

Back 24

Lithocysts

Front 25

Guard cells

cells turgid? ; cells flaccid?

Back 25

stoma open; stoma closed

Front 26

Guard cells control diameter of stoma. How?

Back 26

Changing shape thru osmosis. (note: constant length)

Taking in water = more turgid (due to orientation of cellulose microfibrils, cells buckle outward) = open

Losing water = more flaccid = close

Front 27

Cause of change in turgor pressure that open and close stomata

Back 27

Result primarily from reversible uptake and loss of K+ by guard cells

-uptake of K+ from adjacent epidermal cells to vacuole: osmotic flow of water due to decreased water potential

-loss of K+: osmotic loss of water

Front 28

Stomatal rims or ledges

Back 28

elevated extensions of cuticular membrane

Front 29

Types of stomates (dicot)

Back 29

Anomocytic (subsidiary cells = ordinary cells)

Anisocytic (3 SCs)

Diacytic (2 SCs, perpendicular)

Paracytic (2 SCs, parallel)

Front 30

Types of stomates (monocot)

Back 30

Type I (4-6 SCs; usually "boxed in")

Type II (4-6 SCs; rounded top+bottom and smaller than lateral SCs)

Type III (paracytic)

Type IV (anomocytic)

Front 31

Guard cells: Gramineae and Cyperaceae (describe)

Back 31

dumb-bell shaped; when turgid, expanded ends swell, pulling the elongated parts apart (open)

Front 32

Stomata in some xerophytes

Back 32

Located @ abaxial leaf surface. Usually found in stomatal crypts.

Front 33

Stomata in some xerophytes: stomatal crypts

Back 33

sunken areas of leaf surface to protect pores from dry winds

Front 34

Stomata in some xerophytes: trichomes

Back 34

"hair"; minimize transpiration by breaking up flow of air keeping crypt more humid than in the surrounding atmosphere

Front 35

Sunken stomate

Back 35

Subsidiary cells overarch guard cells (i Pinus i) or formed epidermis with thick cuticular wall (i Franklandia i)

Front 36

Stomata positions

Back 36

amphistomatic (both surfaces)

epistomatic (upper surface)

hypostomatic (more commonly on lower surface)

Front 37

Stomatal development: stomata arise through?

Back 37

Differential division of protodermal cell

Front 38

Stomatal development: guard mother cell

Back 38

-product of the division; immediate precursor of guard cells

-2 guard cells arise after 1-3 divisions

-occur @ same level as adj epidermal cells; rising or sinking of stomate occurs during maturation

Front 39

Stomatal development: pores

Back 39

-before pores separate, area where they form contains pectic enzymes

-formation is initiated enzymatically

Front 40

stomatal development: separation of guard cells

Back 40

occur thru starch hydrolysis

Front 41

(*) Stomatal development: anisocytic

Back 41

asymmetric division of EC => meristemoid + non-stomatal EC1 => 2nd division (meristemoid) => EC2 => 3rd division (M) => EC3 + Guard mother cell => division of GMC => 2 guard cells, no pore yet

Front 42

Trichomes: brief description

Back 42

-hair

-epidermal appendages

-may occur on all parts of plant; may persist or fall off early

Front 43

Trichomes: functions

Back 43

-reduces transpiration rate by increasing boundary layer (still air thru which water vapor must diffuse)

-defense against insects

-secretory may provide defense

Front 44

Dendritic trichome

Back 44

Branched along an axis

Front 45

Glandular trichome @ stinging hair of i Urtica i

Back 45

Pressure on unsilicified base forces liquid into wound

contain histamine, acethylcholine, serotonin (irritation maybe)

Front 46

Common type of trichome

Back 46

Scale or peltate hair: found in mint, shield-shaped cluster of cells

Front 47

Secretion: Internal secretory structures

Back 47

Idioblasts (tannin, calcium oxalate)

Lithocyst

Laticifers

Front 48

Secretion: external secretory structures

Back 48

Hyathodes-modified stomates where excess water is released thru guttation

*epithem-parenchyma tissue lacking chlorophyll between vein and external pore

glandular trichomes