Transcript Plant Tissues

Plant Tissues
 Tissue – group of vegetative cells with one or more
specific functions.
 Two kinds based on state of development:
 Meristematic tissues or Meristems
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Actively engaged in cell division (production of new cells)
Enlarge and differentiate to become permanent tissues
Remain meristematic or repeatedly divide (initials)
 Permanent tissues
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Attained mature form and perform their specific functions
No longer divide and give rise to new cells
All are derived from meristematic tissues
Kinds of Meristems
 Based on position or location within the plant
body:
 Apical meristems (promeristems)
 Found at the tips or apices of stems and roots
 Responsible for the increase in length of stems and roots
 3 meristematic zones:
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Protoderm, Ground meristem, Procambium
 Lateral meristems (or cambia)
 Found along the sides of certain roots and stems
 Responsible for the increase in width or diameter
 Dicots have cambia whereas monocots have no cambia
 Types: vascular cambium and cork cambium (phellogen)
 Intercalary meristems
 Found at the bases of young leaves and internodes
 Considered temporary (short-lived) meristems
Kinds of Meristems
 Based on origin, meristems may be classified as:
 Primary meristems
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Originate in the embryo and persist throughout the lifetime
Apical meristems or their meristematic zones
Intercalary and the vascular cambium
 Secondary meristems
 Derived from permanent tissues
 Cork cambium
 Living permanent tissues lining injured or wounded portions
of plants become meristematic to heal the injured portions
resulting in formation of “callus” or scar tissue.
Kinds of Permanent Tissues
 Based on the number of cell types/kinds of cells:
 Simple permanent tissues
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for the most part consist of only one kind of cell
Composed of similar in structure and function
 Complex permanent tissues
 Consist of several kinds of cells working together as a unit in
carrying out one or more specific functions
Different Kinds of Simple Permanent Tissues
 Epidermis
 External tissue consists of single layer of living cells
 Serves as outermost tissue of leaves, young roots and
young stems; also in old roots and old stems of monocot
plants and herbaceous dicot plants
 Appear cubical or rectangular in shape
 In terms of function, a protective tissue
 In leaves and stems:
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2 kinds of cells:
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Ordinary epidermal cells
Guard cells (kidney-shaped) which occur in pairs and bound by tiny
openings or pores called stomata
epidermis
cortex
vascular bundle
pith
Different Kinds of Simple Permanent Tissues
 Epidermis
 In leaves and stems:
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2 kinds of cells:
 Ordinary epidermal cells
 Guard cells (kidney-shaped) which occur in pairs and bound
by tiny openings or pores called stomata.
Outer wall is coated with a heavy waxy substance (cutin or
cuticle) that prevents excessive transpiration or evaporation of
water from the leaves and stems; roots not cutinized
Epidermal hairs (trichomes) for protective function
Different Kinds of Simple Permanent Tissues
 Parenchyma
 Internal tissue
 Consists of living cells with uniformly thin cell walls
 Large intercellular spaces
 In cross section, appear rounded
 Chlorenchyma – parenchyma with chloroplastids
 Involved in food manufacturing and in food storage
Parenchyma Cells
- Parenchyma cells are living cells
with uniformly thin walls. They
comprise the photosynthetic
tissue of a leaf, the soft flesh of
fruits, and the storage tissue of
roots and seeds.
epidermis
collenchyma
parenchyma
- A widely distributed tissue
located beneath the collenchyma
between the vascular bundles
(consisting of vascular tissues and
at the center of the section.
Different Kinds of Simple Permanent Tissues
 Collenchyma
 Also an internal tissue
 Consists of living cells with unevenly thickened walls–
thin on the sides but thickened at the angles where two
or more cells meet
 Appear cubical or slightly rectangular and are more or
less compactly arranged
 A strengthening or support tissue; storage of food
Collenchyma Cells
Collenchyma cells have
unevenly thickened cell
walls, which are their
distinguishing
characteristic. They form
strands along veins in
leaves and beneath the
epidermis in stems to
provide support and
strength against the
onslaught of strong winds
and rains.
Different Kinds of Simple Permanent Tissues
 Sclerenchyma
 Also an internal tissue
 Consists of dead cells when mature, with heavily
thickened cell walls mainly due to the deposition of
lignin
 It may appear in the form of fibers or sclerids
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Fibers –elongated cells with tapering ends occurring in groups;
appear as cells with tiny empty cell cavities or cell lumina with
heavy and uniformly thickened cell walls in cross section
Sclerids –irregularly-shaped cells and typically not elongated;
various forms but the most common are stone cells (isodiametric
and like sand particles occur singly or in groups)
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Found in fruits: coconut shell is sclerids, coconut husk is fibers
gritty texture of sugar apple (atis) and chico due to stone cells
 Strengthening or supportive tissue
Sclerenchyma Cells
- Sclerenchyma cells
have thick and rigid
cell walls. They serve
as strengthening
elements to support
mature plant parts.
- Found in groups of
cluster among the
parenchyma cells
around the vascular
tissues
Different Kinds of Simple Permanent Tissues
 Cork
 External tissue serving as outermost tissue or covering of
old stems/roots of woody dicot plants
 Consists of several layers of dead cells when mature
 Cell walls are impregnated with waxy substance
(suberin) – impermeable to substances, resulting to the
death of cells upon reaching maturity
 Rectangular in shape and arranged in layers in crosssection
 Protective tissue
BARK
epidermis
phellem (cork)
phellogen (cork cambium)
phelloderm
cortical parenchyma
periderm
phellem
phellogen
phelloderm
Plant Cell Types
PLANT CELL
TYPE
PROTOPLASM
+/-, CELL LIVING
OR DEAD
CELL WALL CHARACTERS
CELL THICKNESS
FUNCTION
CHEMICAL
COMPOSITION
Parenchyma
+, living
Uniformly thin
Cellulose,
hemicellulose
may have cutin
Food storage,
food
manufacture
Collenchyma
+, living
Irregularly thick
Cellulose,
hemicellulose
Food storage,
strengthening
Sclerenchyma
-, dead
Uniformly thick
Cellulose,
hemicellulose
added suberin or
lignin
Strengthening
and support
1. sclereid
2. fiber
CELL SHAPE
Polyhedral to much branched sclerenchyma cells
Long and slender sclerenchyma cells
Kinds of Complex Permanent Tissues
 Phloem
 Function: mainly conductive or vascular tissue
 Conducts dissolved organic food materials
 Consists of the following cell types:
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Phloem fibers
Phloem parenchyma
Sieve tube elements
Companion cells
Kinds of Complex Permanent Tissues
 Phloem: cell types
 Phloem fibers
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appear like ordinary schlerenchyma fibers
 Phloem parenchyma
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appear like ordinary parenchyma cells
Kinds of Complex Permanent Tissues
 Phloem: cell types
 Sieve tube elements
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conducting cells of the phloem
living, non-nucleated cell when mature
elongated in form and uniformly thin-walled with the end
walls perforated to form sieve plates that are attached end-toend forming long conducting tubes (sieve tubes)
consists of protoplasmic connections between adjacent cells plasmodesmata
Kinds of Complex Permanent Tissues
 Phloem: cell types
 Companion cells
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parenchymatous cells which are always found beside the sieve
tubes
small, elongated and nucleated living cells when mature
plasmodesmata have also been observed to occur between
the companion cells and the sieve tubes
Kinds of Complex Permanent Tissues
 Xylem or Wood
 Function: mainly conductive or vascular tissue
 Conducts water and mineral salts
 The main strengthening tissue of the plant
 Consists of the following cell types:
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Xylem fibers
Xylem parenchyma
Vessel elements
Tracheids
Kinds of Complex Permanent Tissues
 Xylem: cell types
 Xylem fibers
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appear like ordinary schlerenchyma fibers
 Xylem parenchyma
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structurally similar but much smaller than the ordinary
parenchyma cells
Kinds of Complex Permanent Tissues
 Xylem: cell types
 Vessel elements
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main conducting cells of the xylem
Elongated in shape and dead when mature
Heavily thickened cell walls
Have relatively large cavities or lumina which generally
appear rounded in cross section
Vessel elements are attached end-to-end with their end walls
perforated to form long conducting tubes (xylem vessels)
Perforation plate – perforated wall having one or more
openings
Kinds of Complex Permanent Tissues
 Xylem: cell types
 Tracheids
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simplest conducting cells of the xylem
dead cell when mature
elongated in shape and square-like in cross section with
heavily thickened cell walls
Tracheary elements – consists of the vessel elements and the
traceheids; have different types depending on how lignin is
deposited on their cell walls
bundle sheath
companion cell
phloem
sieve tube
Cross section of a monocot stem
vessel
xylem
vessel
air space
vascular bundle
phloem fiber
phloem parenchyma
sieve tube
companion cell
vascular cambium
Tracheid (schlerenchyma)
vessel
xylem parenchyma
xylem fiber
Kinds of Complex Permanent Tissues
 Main types of tracheary elements:
 Annular type – thickening of the cell wall is in the form
of rings
 Spiral type – the thickening is in the form of a spiralling
or helical structure
 Scalariform – the thickening is ladder-like
 Reticulate – the thickening is net-like
 Pitted type – the uniformly thickened cell walls show
the presence of more or less rounded depressions or
pore-like structure (pitts) representing the non-lignifed
portions of a wall
reticulate
Plant Trichomes
 Trichomes or epidermal hairs
 appendages of the epidermal cells
 may be unicellular or multicellular
 glandular and non-glandular structures
 Glandular trichomes – consist of living cells and produce
secretions
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Types: glandular and stinging trichomes
 Non-glandular trichomes – consist of dead cells and
non-secretory
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Kinds: bristles, scales, stellate, and branched (dendroid)
Plant Trichomes
 Glandular Trichomes
 Glandular trichomes
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produce secretions in enlarged terminal portions
Examples: ratilis, oregano and malvarosa
 Stinging trichomes
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Consist of enlarged base containing secretion from which
projects a stiff, slender structure that ends in a sharp point
Example: lipang kalabaw
Plant Trichomes
 Non-glandular Trichomes
 Bristles - stiff, sharp pointed hairs which may be barblike protuberances along the sides as in lipa
 Scales - flattened structure as in alingaro
 Stellate trichomes – star-like structure as in ratilis and
Mallotus
 Branched trichomes (dendroid) – as in the velvet dock
Glandular trichomes
Glandular trichomes - Enlarge terminal portions
Glandular trichomes - Enlarge terminal portions
Non-gladular