The document summarizes key aspects of the epidermis and epidermal cells in plants. It describes the epidermis as the outermost layer of cells in organs. It then discusses the structure and types of ordinary epidermal cells, epidermal cells with special structures, cells associated with stomata, cuticle layers and wax, trichomes and root hairs. The main types of stomata are also summarized based on their ontogeny in both eudicots and monocots.

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EPIDERMIS
Outermost layer of cells of organs in primary
growth
In most plants, uniseriate
Multiseriate–
M lti i t may originate f
igi t from:
a] ground meristem hypodermis
b] protoderm multiseriate epidermis
EPIDERMIS
MULTISERIATE EPIDERMIS
Results from periclinal division of protoderm
Occurs late in ontogenic stages
eg. Ficus elastica
Moraceae, certain Begoniaceae
Velamen water storage
CELLS IN THE EPIDERMIS A. ORDINARY EPIDERMAL CELLS
A] ordinary epidermal cells Closely attached to form compact layer
B] single cell or groups of cells with special Devoid of intercellular spaces
structure; form or content Conifer very thick and lignified
C] cells connected with stomata
ll t d ith t t Cutin is present in the outer wall
D] epidermal appendages complex of lipid derivatives
deposition outside the cell forms CUTICLE
layer
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Cuticle proper cuticularization (secretion of
CUTICLE
cutin to the surface of the cell wall
Present in all parts of herbaceous stem, leaves Cuticular layer cutinization (deposition of
Absent in actively growing parts of the roots cutin between the cellulose microfibrils of the
outermost wall layers
Thicker plants in dry habitats
Pectin layer
Two layers: 1] cuticle proper (outer; cutin)
Epicuticular wax depostion of wax on the
2] cuticular layer(inner; cutin+wall surface of cuticle; granulated or rod-like or
materials) continuous layer
gives the “bloom” of many leaves and fruits
WAX
affects the cuticular permeability and the
degree to which a surface can be wetted
Reduces damage to photosynthesis and heat
load of leaves
LIGNIN
Rare
When present, it is found in all walls or only in
outer wall
Eg. Cycadaceae, needles of conifers
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STRUCTURE OF PROTOPLAST OF ORDINARY B. EPIDERMAL CELLS WITH SPECIAL
EPIDERMAL CELLS STRUCTURE OR CONTENT
Highly vacuolated In Gramineae:
Contain leucoplasts --- long cells and short cells
Numerous mitochondria, ER, spherosomes, *short cells silica cells and cork cells
dictyosomes
di t --- bulliform cells thin walled and large vacuole
chloroplasts - devoid of chloroplasts
Anthocyanins –in flowers, in boat of moses lithocysts– Acanthaceae, Moraceae,
Urticacaceae, Cucurbitaceae
C. CELLS ASSOCIATED WITH STOMATA
Minute openings or intercellular spaces limited
by guard cells– stomata
Stoma= opening +guard cells
Stomatal apparatus or comples = stoma +
St t l t l t
subsidiary cells
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TYPES OF STOMATA BASED ON ONTOGENY
a. mesogenous
-- subsidiary cells (SC) and guard cells
common origin
b. Perigenous
b P ig
-- SC develop from protodermal cells adjacent
to the stomatal mother cell
c. Mesoperigenous
- cells surrounding the stoma are of dual origin
STOMATA
aerial portion of plant; esp. on leaves
Absent in roots
Floating water plants – upper side of leaves
only
l
Land plants – lower surface or both
Plants in full sun environment /high
photosynthetic capacity--both
STOMATA
Arrangement
> random in plants with reticulate venation
> arranged in parallel row with parallel venation
Position relative to other epidermal cell
> level
> raised
> sunken
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Substomatal chamber
Opening of stomata
Shape
> kidney shaped
> dumb bell shape/ elongated (Gramineae;
Cyperaceae)
MAIN TYPES OF STOMATA (EUDICOTS)
Anomocytic (ranunculaceous)
Anisocytic (cruciferous)
Paracytic (rubiaceous)
Diacytic (caryophyllaceous )
Actinocytic --uncommon
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MAIN TYPES OF STOMATA (MONOCOT)
1] 4-6 subs. cells
2] 4-6 subs. cells; 2 round, smaller than the rest,
situated at the end of guard cell
3] Guard cells are accompanied laterally by 2
G d ll i d l t ll b
subs. Cells
4] guard cells are not assoc. with any subs. cells
ONTOGENY OF STOMATA
TYPES OF STOMATA DEVELOPMENT (BASED ON
ORDER OF APPEARANCE OF STOMATA)
STOMATA FREE REGIONS
Basipetal – parallel venation inhibition of additional stomata by already
--from the tip of the organ to its base differentiated ones
No pattern– reticulation venation Formation of stomata together with the
surrounding cells as part of the same
developmental pattern
Induction of stomata pattern by the pattern of
the underlying tissue (mesophyll)
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D. EPIDERMAL APPENDAGES TRICHOMES
Unicelluar and multicellular-- Trichome 1. Non-glandular
Massive structures such as warts, prickles a. simiple unicelluar or multicellular, uniseriate,
(epidermal and subepidermal)– emergences non-flattened hairs
TRICHOMES—may be lignified, with secondary
TRICHOMES b lig ifi d ith d b.
b squamiform h i fl t and multicellular
if hairs—flat d lti ll l
wall or lose their protoplast *sessile scale
-- has taxonomic implications *stalked peltate
*dendritic
c. multicellular hairs– stellate; branched
candelabrum-like
d. T-shaped hairs
TRICHOMES
2. Glandular d. Mucilage secreting
- secretion of various substances (salt, sugar as e. Glands of carnivorous plants
in nectar, lipids, gums)
f. Trichomes secreting lipophilic materials
-possess endodermal cells (prevents backflow)
possess
g. colleters- secreting sticky substances
- sessile or stalked
a. salt-secreting trichomes h. Stinging hairs
b. Trichome-hydathode
c. nectar-secreting
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3. Root hairs- tubular elongations of epidermal
cells
- appear beyond the meristematic region
- viable for a short period
i bl f h t i d
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