Transcript Meristematic tissue/meristems

Introductory Plant Biology
Ninth Edition
Kingsley Stern
Chapter 4
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Botany Chapter 4
Tissues
Overview
 4 organs of plants
1. Roots
2. Stems
3. Leaves
4. Flowers
All formed from tissues
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Meristematic Tissue
 Meristematic tissue/meristemspermanent regions of growth in
plants; 3 Types of Meristems
1. Apical meristem- found at or near
the tips of roots and shoots
- increases the length of plant; this
is primary growth
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Meristems cont.
2. Lateral meristems- produce tissues
that increase the girth of roots and
stems; secondary growth
2 types of lateral meristems
1. Vascular cambium/ cambiumproduces secondary tissues;
xylem and phloem
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Meristems cont.
-a thin cylinder of brick-shaped
cells that extends through root and
stems
2. Cork cambium-produces bark
- lies just inside the outer bark
- thin cylinder of cells that
runs length of roots and stems
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Meristems cont.
3. Intercalary meristems- found at
nodes in grasses and related plants
instead of vascular and cork
cambium
- node- point of leaf attachment
- develop at intervals along stems
- also add to stem length
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Fig. 4.1
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Tissues produced by meristems
 3 Types of Simple Tissues
1. Parenchyma tissue- made of
parenchyma cells; most abundant
- Cells generally have 14 sides and
large vacuoles
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Parenchyma cont.
- may contain numerous chloroplasts
(referred to as chlorenchyma)
- w/out chloroplast, function in food
and water storage
- can multiply and repair wounds
and form roots on a cutting
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Simple tissues cont.
2. Collenchyma tissue- made of
collenchyma cells
- found beneath epidermis
- provide flexible support
- “strings” of celery
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3 Simple tissues cont.
3. Sclerenchyma tissue - made of
sclerenchyma cells
- thick, tough, secondary walls with
lignin (a polymer)
- most are dead at maturity and
function in support
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2 Types of sclerenchyma tissue
1. Sclereids or stone cells- produce
gritty texture of pears and hardness
of shells and peach pits
2. Fibers- used to manufacture
textile goods, ropes, string, canvas
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Complex tissues-2 or more types
of cells
1. Xylem- plumbing and storage
systems
- chief conducting tissue throughout
all organs for water and minerals
absorbed by roots
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Xylem cont.
- consists of parenchyma cells,
fibers, vessels, tracheids and ray
cells
- vessels- made of dead cells called
vessel elements; straw-like with
bars of wall material across open
areas
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Xylem cont.
- tracheids- dead cells with thick cell
walls
- no vessel-like openings, but
have pits which allow water
to pass from cell to cell
-rays-long-lived parenchyma cells
produced in horizontal rows; conduct
water laterally
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Fig. 4.6
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Complex tissues cont.
2. Phloem- conducts food produced
by photosynthesis throughout the
plant
- made of 2 types of cells
1. Sieve tube members- cells layed
end to end forming sieve tubes
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Complex tissue cont.
1. Sieve tube members cont.
- Walls are full of small pores
through which cytoplasm
extends cell to cells
- sieve plates porous regions of
sieve tube members
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Complex tissues cont.
2. Companion cells - help control
transport of sugar through sieve
tube member
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Complex tissues cont.
3. Epidermis- outermost layer of
cells of all young plants
- one cell thick
- cuticle- protective layer on the
surface of the outer wall
- made of fatty cutin
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Complex tissues cont.
Epidermis cont.
-stomata- (sing. Stoma)- pores in
leaves
-guard cells- cells that border
stoma
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Complex tissues cont.
4. Periderm- consists of outer bark
(woody plants)
-made of cork cells- dead at maturity
- Suberin- fatty substance secreted
by cork cells that waterproofs and
protects the plant
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Complex tissues cont.
Periderm cont.
-lenticels- pockets of parenchyma
cells with no suberin (pg. 63)
- function in gas exchange
between air and interior of the
stem
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Secretory Cells and Tissues
Examples of secretions:
 nectar in flowers
 oils in citrus fruits and mint
 resins in pine trees
 opium
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Fig. 4.7
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Fig. 4.8
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Fig. 4.10
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Fig. 4.11
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Fig. 4.14
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