Transcript Ground Tissues

I. Parenchyma – These are the most abundant
and versatile cells found in plants.
A. Storage - Plants store nutrients in
Parenchyma cells.
B. Basic Metabolism – parenchyma cells are
the primary sites of photosynthesis and
protein synthesis.
 Differentiation – When a cell changes to
another type of cell to carry out a different
function.
 Redifferentiation – When that same cell
changes back to carry out its original function
II. Collenchyma: support growing
regions of shoots and therefore are
found in stems and petioles.
These cells actually develop from
parenchyma cells, especially during
mechanical stress.
 III. Sclerenchyma – are rigid,
nonstretchable secondary cells that
support and strengthen nonextending
portions of plants such as mature stems
and are usually dead at maturity. The
support of Sclerenchyma is usually
attributed to it’s thick cell walls.
 A. The first type of sclerenchyma cells are
called sclereids, which are relatively short,
and have a variety of shapes and are found
singly or in groups.
 B. The second type are fibers, which are long
slender cells which usually occur in strands
or bundles.
 More about Sclereids:
 They are found throughout plants
such as in roots, leaves, stems, seed
coats, and even in peanut hulls.
 They usually form hard layers, such as
in the core of an apple or the shell of
walnuts.
 More about Fibers – there are a number of uses
of fibers.
 Manila hemp – used for making ropes and cords
 Agave – used to make course ropes and twines.
 Cannabis – used to make rope and twine
 Flax – used to make linen and other flexible, soft
items such as sheets and even money.
 Jute – used to make very coarse fabrics such as
burlap, bags and sacks. This is the second most
important fiber in the world behind only cotton.
 Cotton – the single most important fiber in the
world. however, cotton is not a sclerenchyma fiber,
but a trichome, which is an extension or outgrowth
of epidermal cells.
Cotton
Flax linens
Manila hemp
Jute burlap sack
Agave Plant
Agave fiber weaving
Cannabis fiber plant
Cell Types
 The Epidermis –
 The outer walls of the epidermis are covered with
a waxy , fatty, waterproof layer of cutin called a
cuticle.
 On the underside of wax palms is a thick layer of
waxy epithelium called carnauba wax which is
used to make candles, polishes and lipsticks.
Gas Exchange
 Gas exchange is carried out through spaces or
holes in the epidermis called stomata.
 These Stomata are surrounded by cells known
as guard cells which regulate gas exchange and
the loss of water.
stomata
Guard cell
 The flat bricklike cells that lack chloroplasts and
are transparent are called epidermal cells.
 The structures inside plant cells that enable them
to carry out photosynthesis are called
chloroplasts.
Trichomes
 Single celled or multicellular outgrowths of
epidermal cells, often used to protect the
seed.
 The most economically valuable trichomes are
cotton seed epidermis.
 Some trichomes are used by carnivorous
plants to to secrete enzymes used to liquify
trapped prey and digest them
 Root hairs are also trichomes.
 Trichomes are also used by seeds for dispersal,
especially those that are light and airy.
Vascular Tissues: Xylem and Phloem
 Xylem carries water and dissolved nutrients in an
unbroken stream from the roots upward to all
parts of the plant.
 Phloem transports dissolved organic materials,
especially sucrose, for transport to all parts of the
plant, NOT just downward.
Secretory Structures
 Nectaries: structures that secrete nectar, a
sugary substance that attracts insects, birds,
bats, or other animals .
 Internal secretory cells are large cells that
contain tannins, resins, mucilage, and
crystals.
 Laticifers are secretory cells that contain
latex.
 Salt Glands secrete salt from marsh plants
such as spartina
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