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Lecture
PLANTS TISSUES
Authors
as. Kernychna I.Z.
Plan
1.Meristematic tissues.
2. Dermal tissues.
3. Secretory tissues.
4. Parenchyma.
In the body plants cells not isolated, but placed groups - on the basis of
community of origin, structure and functions. These groups of cells name
tissues.
Many classification
Living and dead;
meristematic and constant;
Simple and complex;
Primary and secondary
The tissues of a plant are organized into
three tissue systems: the dermal tissue
system, the ground tissue system, and
the vascular tissue system
Simple tissues are:
Classification
tissues
Parenchyma
Chlorenchyma
Collenchyma
Sclerenchyma
Complex tissues are:
DERMAL
XYLEM
PHLOEM
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Meristematic
tissues:
the cells are
small,
the cells walls
are thin,
cells have large
nuclei,
vacuoles are
absent or very
small, and
there are no
intercellular
spaces.
Plants have four types of meristems:
apical, lateral, intercalary, and wound
(or regeneration).
Dermal tissues
cover the plant body
There are two types of dermal tissue:
The primary is:
epidermis
The secondary is:
periderm
Epidermis is closely packed,
without intercellular spaces
or chloroplasts. The outer walls
may be covered waxy, waterproof
cuticle
Guard cells contain
chloroplasts and regulate
gas exchange between the
inside of the leaf and the
surrounding air.
Trichomes- on plants are epidermal outgrowths of various kinds.
Trichomes
may be unicellular
or multicellular,
branched or unbranched
Branched hairs can be dendritic
(tree-like),
tufted, or stellate (star-shaped).
Epidermal hairs
lower water loss by
decreasing the flow
of air over the plant
surface, which in
turn, slows the loss
of water from the
plant.
Glandular hairs
(secretory) prevent
herbivory by storing
substances that are
harmful to insects.
Root hairs
increase water
uptake by
increasing the
surface area
of the cell.
Epidermis is short lived in many plants.
When epidermis ruptures a secondary dermal
tissue periderm that concist of phellogen (cork cambium),
phellem (cork),
phelloderm (secondary cortex) replaces it.
SECRETORY TISSUES OF PLANS
secretory structures:
external secretory structures (nectaries, hydathodes, secretory hair)
- internal secretory structures
(secretory cells, canals, ducts, cavities, laticifers).
Resin canals
Internal secretory structure:
- laticifers (of dantelion);
OIL CANALS
Parenchyma
Types parenchyma
1. Chlorenchyma
2. Aerenchyma
3. Storage parenchyma
Chlorenchyma
:
contains
chloroplasts
and functions
in
photosynthesis
Chlorenchyma of leaves
STORAGE
PARENCHYMA:
characterized by
large
accumulations
of storage
products such
as starch,
protein, oil,
hemicellulose or
water.
Aerenchyma
contains large
intracellular air
spaces and
functions in
gas exchange.