Tissues Flashcards
All tissues that are
neither dermal nor vascular in plants :
Ground Tissue.
Tell all components and function of Dermal tissue:
Components :
- Epidermis
- Periderm
Function:
- Protection
- Prevent Loss of Water
Tell all components and function of Ground tissue:
Components:
- Parenchyma
- Collenchyma
- Sclerenchyma
Functions:
- Metabolism
- Storage
- Support
Tell all components and function of Vascular tissue:
Components:
- Xylem
- Phloem
Function:
- Transport
Parenchyma, Collenchyma, and Sclerenchyma are…
Simple tissue
Xylem, Phloem, Epidermis, Peridermis, and Secretory Cells and
Tissues are…
Complex tissue
Parenchyma
- Most abundant tissue find in plants.
-have large vacuoles - may contain: Starch grains, Oils, Tannins, Crystals, and Other secretions.
-Mostly found in aquatic and wetland plants.
-Parenchyma cells have spaces between
them.
Parenchyma tissue with extensive connected air spaces is referred to as…
Aerenchyma
(give plant ability and stability to float)
Parenchyma cells containing numerous chloroplasts and tissues functioning mainly in photosynthesis:
Chlorenchyma
Chlorenchyma vs. Aerenchyma
Chlorenchyma –> lot of chloroplast
Aerenchyma –> lot of air cavity
What parenchyma is capable of:
- Mature parenchyma cells can divide long after they were produced by a meristem. Parenchyma cells live a long time.
- When a cutting (segment of stem) is induced to grow, parenchyma cells start dividing and give rise to new roots.
- Capacity of Parenchyma cells to multiply is important in repair of tissues.
Collenchyma cells :
- Have living cytoplasm
and may remain alive a long time. - Generally thicker walls and more uneven in thickness than those of
parenchyma cells. Unevenness due to extra primary wall in corners. - Often occur just beneath
the epidermi. - flexible support for growing organs and mature organs.
Sclerenchyma tissue :
- Cells have thick, tough,
secondary walls, normally
impregnated with lignin.
_ Cells are dead at maturity and function in support - Two forms of sclerenchyma occur :
- Sclereids
- Fibers
Are the reduced form of
sclerenchyma cells with highly thickened, lignified walls. May be randomly distributed in other tissues….
Sclereids (stone cells)
May be found in association with
different tissues in roots, stems, leaves, and fruits.
They are usually much longer than wide and have a proportionately tiny cavity, or lumen,
in the center of the cell…
Fibers
Main transport
systems of plants. Typically occur together in vascular bundles in all plant organs.
Xylem and Phloem
Xylem
- Transports water and minerals absorbed by the roots throughout
all organs. - Consists of a combination of:
- Parenchyma cells
- Fibers
- Vessels
- Tracheids
- Ray cells
Vessels
- Have thick secondary
cell walls and are open at their ends. - Stacked end-on-end to form long tubes.
- Perforation plate with bars or holes may be found between the end walls of each pair of vessels elements.
- Found in Vessels
- Flow of fluid through the vessels is not blocked by it.
- But may block the
movement of objects, such as fungal spores that may invade the xylem.
What is it ?
Perforation Plates
Tracheids
- Dead at maturity and have thick secondary cell walls.
- Ends overlapping with those of other tracheids.
- Usually, pairs of pits are present wherever two
tracheids are in contact with one another. - Pits allow water to pass from cell to cell.
Ray Cells
- Lateral conduction takes place in the rays.
- Long-lived parenchyma cells produced in horizontal rows by
special ray initials of the vascular cambium - Function in food storage
Phloem
- Phloem tissue conducts dissolved food materials (primarily sugars) PS throughout the plant.
- Composed mostly of 2 types of cells without secondary walls : Sieve tube members (relatively large and cylindrical) and Companion cells(narrower)
- Includes fibers, parenchyma, and ray cells
- End walls full of small pores (sieve plates) through which the cytoplasm extends
from cell to cell.
Sieve tubes members
- No nuclei at maturity
- Cytoplasm very active in conduction of food materials.
- Laid end to end in Phloem.
Companion cells
- Found in Phloem
- Form a close relationship with the sieve tubes and aid in the conduction of the food.
Sieve cells
- Similar to sieve tube members but tend to
overlap at their ends rather than form continuous tubes - Found in ferns and cone-bearing trees
- Have no nuclei at maturity and no adjacent companion cells
- Have adjacent albuminous cells (Equivalent to companion cells)
Dermal Tissues
- Meristematic tissues
- The outer layer of tissue
surrounding the entire plant,
covers and protects the plant, and
controls gas exchange and water
absorption.
Epidermis
- The outermost layer of
cells of all young plant
organs. - Since it is in direct contact with the environment, it is subject to modification by the environment and often includes several different kinds of cells.
- one cell thick
Vallen roots
- Few plants produce aerial roots called
velamen roots. - The epidermis may be several cells thick, with the outer cells functioning something like a sponge.
Cutin
- Fatty substance within and on the outer
walls - Forms a protective layer called the
cuticle - The epidermis secrets a wax on top
of the cuticle - Prevents water loss
- Protects from bacteria and other
disease organisms
They are ubular extensions of roots formed by epidermal cells. They greatly increase the absorptive area of the surface.
Some of different nature occur on the
epidermis (Trichomes) of above-ground
parts of plants.
What are they ?
Root Hairs
The stomata are bordered by pairs of specialized epidermal cells called…
Differ in shape from other epidermal cells
Contain chloroplasts.
Guard Cells
Other epidermal cells
- Glands that secrete protective or other
substances - Hairs that either reduce water loss or repel insects
and animals
Periderm
- In woody plants, the epidermis is sloughed off and replaced by a periderm after the cork cambium begins producing new tissues that increase the girth of the stem or root.
- Constitutes the outer bark, primarily
composed of somewhat rectangular and boxlike cork cells, which are dead at maturity. - While the cytoplasm of cork cells is
functioning, it secretes a fatty substance,
suberin, into the walls. - Makes cork cells waterproof and helps
them protect the phloem and other tissues
beneath the bark from: - Drying out
- Mechanical injury
- Freezing temperatures
Lenticels
- Loosely arranged parenchyma cells
that are not impregnated with
suberin. - Function in gas exchange between
the air and the interior of the stem.
Secretory Cells and Tissues
- Cells or tissues often derived from
parenchyma, can occur in various places in a plant. - Common secretory tissues include those that secrete:
- Nectar in flowers;
- Oils in citrus, mint, and other leaves;
- Mucilage in the glandular hairs of sundews and other insect-trapping plants
- Latex in members of several plant families, such as the Spurge Family
- Resins in coniferous plants, such as pine trees
