Transcript Plant Tissues - PPT - BIOLOGY LEARNING BLOG

Plant Tissues: Overview
Meristems, Simple Tissues, &
Complex Tissues
Many of the figures found in this presentation are from the internet site
http://botit.botany.wisc.edu/images/130/ and a CD entitled “Plant Anatomy” by
Richard Crang & Andrey Vassilyev published by McGraw Hill.
I. Meristematic Tissue
Origin
Location
II.
: Promeristem, Meristem Primer,
Meristem Sekunder
(cambium)
: apical, intercalar, lateral
Permanent Tissue
Epidermis
: silica cell, stomata, trichomata, spine,
velamen, fan cells.
Parenchyme: assimilation, storage, water, vascular,
aerenchyme, wound covering.
Supporting : collenchyme,sclerenchyme (schlerenchyme
fiber, sclereid)
Vascular
: xylem (tracheid, vessel element), phloem
(sieve tube element, companion cells)
Cork
: feloderm, felem
Specialized Tissues in Plants
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Roots
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Absorbs water and
nutrients
Anchor plant to the
ground
Hold soil in place and
prevent erosion
Protect from soil bacteria
Transport water and
nutrients
Provide upright support
Specialized Tissues in Plants
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Stems
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Support for the plant
body
Carries nutrients
throughout plant
Defense system to
protect against predators
and infection
Few millimeters to 100
meters
Specialized Tissues in Plants
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Leaves
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Main photosynthetic
systems
Suseptable to extreme
drying
Sight of oxygen/carbon
dioxide intake and
release
MERISTEMATIC TISSUE
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The cells of meristematic tissue are similar in structure
& have thin cellulose cell walls.
The meristematic cells may be spherical,oval,polygonal
or rectangular in shape.
The meristematic cells contain few vacuoles
Cells of meristems divide continuously
Occurrence-Meristematic tissues are growth tissues & are
found in those regions of the plant that grow. According to
their position in the plant, meristems are apical, lateral &
intercalary.
Function-the main function of meristematic tissue is to
continuously form a number of new cells.
Intercalary Meristem
Meristematic tissues – localized regions
of cell division
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Apical meristems:-these are situated at the growing tip of
the stems & roots. At shoot apex & root apex. It brings
about the elongation of the root & stem. It results in
increase in the height of the plant, which is called primary
growth.
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Lateral meristems-these are found beneath the bark (cork
cambium) & in vascular bundles of dicot roots &
stems(cambium).They occur in thin layers. Cambium is the
region which is responsible for growth in thickness. It
causes the organ(stem or root) to increase in diameter .
This is called secondary growth.
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Intercalary meristems-they are located at the base of leaves
or internode,e.g., Stem of grasses & other monocots.
Root Apical Meristem
1. Root cap
initials
2. Protoderm
3. Ground
meristem
4. Procambium
5. Root cap
Lateral Meristems – secondary
growth in woody plants
Basswood – root in cross section
Basswood – stem in cross
section; 1, 2, 3 year old stems
PARENCHYMA
Parenchyma cells are oval,round,polygonal or elongated in
shape. The cell wall is thin & encloses a dense cytoplasm which
contains a small nucleus & surrounds a large central vacuole.
Occurrence-the parenchyma is widely distributed in stem,roots,
FunctionsParenchyma maintain the shape & firmness of the plant due to
its turgid cells. The main function of parenchyma is to store &
assimilate food. Parenchyma serves as food storage tissue .
Transport of materials occurs through cells or cell walls of
parenchyma cells. Parenchyma cells are metabolically active;
their intercellular air spaces allow gaseous exchange.
Isodiametric Parenchyma Cell containing
Chromoplasts: Each red dot is a Chromoplast that
Contains Carotenoids.
Elongate Palisade Parenchyma with
Chloroplasts
Parenchyma from Potato with large
Amyloplasts
Parenchyma Cells containing
Amyloplasts.
Shoot Apical Meristem
PERMANENT TISSUE
These tissues derived from the meristematic tissues but
their cells have lost the power of division & have
attained their definite forms. Permanent tissues are
classified into two-simple & complex.
Permanent tissue-these tissues are composed of cells
which are structurally & functionally similar. They are
:
Epidermis
II. Connective
III.Vascular
I.
Parenchyma
Surface View of Epidermis from a Leaf: Note the
undulating Epidermal Cells plus the Stomata (S) and
Trichomes (T).
COLLENCHYMA
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It shows many of the features of parenchyma but is
characterized by the deposition of extra cellulose at
the corners of the cells. In collenchyme ,intercellular
spaces are generally absent. Collenchyme cells are
elongated in shape. They often contain a few
chloroplasts.
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Occurrence-the cells of collenchyma are located below
the epidermis of dicotyledon stem & petiole.
Collenchyma is absent in monocot stems,roots &
leaves.
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Functions- collenchyma is a mechanical tissue;it
provides mechanical support & elasticity.
SCELERENCHYMA
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Composed of dead cells and sclerenchyma are
greatly thickened with deposition of lignin. The
cells of sclerenchyma are closely packed without
intercellular spaces.
Found in stems,roots,veins of leaves.
Functions-the sclerenchyma is mainly mechanical
&
protective
in
function.
It
gives
strenght,rigidity,flexibility & elasticity to the plant
body &,thus,enables it to withstand various
strains.
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i.
ii.
XYLEM
Nature-xylem is a vascularXylem is composed of cells
of four different types:
tracheids and vessels element (bounded by thick
lignified. Vessels are very long tube-like structures
formed by a row of cells placed end to end. They
conduct water).
FunctionsThe main function of xylem is to carry water & minerals
salts upward from the root to different parts of shoots.
Since walls of tracheids,vessels of xylem are lignified,
they give mechanical strength to the plant body.
PHLOEM
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Nature-Phloem is composed of following two
types : 1.sieve tubes;2.companion cells;
Functions-phloem transport
photosynthetically prepared food materials
from the leaves to the storage organs & later
from storage organs to the growing regions of
the plant body.
Collenchyma
Sclerenchyma
SCLERIDS
Right-hand illustration modified from: Weier,
Stocking & Barbour, 1974, Botany: An
Introduction to Plant Biology, 5th Ed.
FIBERS
Epidermis – stoma, trichomes, & root hairs
http://www.ucd.ie/botany/Steer/hair/roothairs.html
Xylem
Phloem
Vascular Bundles with xylem & phloem
Maize or Corn – vein in cross
section
Alfalfa – vein in cross section
Periderm – cork & parenchyma
TWIG WITH LENTICELS
Secretory Structures
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nectar (flowers) from nectaries
oils (peanuts, oranges, citrus) from accumulation of
glands and elaioplasts.
resins (conifers) from resin canals
lacticifers (e.g., latex - milkweed, rubber plants,
opium poppy)
hydathodes (openings for secretion of water)
digestive glands of carnivorous plants (enzymes)
salt glands that shed salt (especial in plants adapted to
environments laden with salt).