Plant Tissues

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Plant Tissues
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Plant Organ Systems

• Shoot system
• Leaves
• Fruits
• Flowers
• Stems, branches
• Root system
• Primary root
• Lateral root

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shoot tip (terminal bud)
lateral (axillary) bud
flower
node
internode
EPIDERMIS
node
leaf
VASCULAR TISSUES
seeds (inside fruit)
GROUND TISSUES
withered cotyledon
SHOOT SYSTEM
ROOT SYSTEM
primary root
root hairs
lateral root
root tip
root cap
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Major Plant Groups

• Green Algae ancestral group
• Mosses, Liverworts
• Ferns, Horsetails
• Gymnosperms Conifers (Pine trees, Redwood,
  Spruce, Cedar, etc.)
• Flowering Plants Well study these in lab
• Monocots
• Dicots

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Monocots and Dicots

• Monocots include all the grasses
• All cereal grains wheat, rice, corn, etc.
• Bamboo,
• Also monocots orchids, lilies, palms
• Dicots are much more numerous
• many common flowers, fruits, vegetables
• grapes, tomatoes, poppies, celery , carrots,
  lettuce, potatoes, etc.
• Also include all the true woody flowering plants
  / trees oaks, apples, oranges, etc.

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In seeds, two cotyledons (part of the embryo)
In seeds, only one cotyledon
Usually four or five floral parts (or
multiples of these)
Usually three floral parts (or multiples of three)
Usually a netlike array of leaf veins
Usually a parallel array of leaf veins
Basically, three pores or furrows in pollen grain
Basically, one pore or furrow in pollen grain
vascular bundle
Vascular bundles distributed in ground tissue of
stem
Vascular bundles arrayed as a ring in stem
DICOTS
MONOCOTS
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Dicot
Monocot
Ring of vascular bundles dividing ground tissue
into cortex and pith
Vascular bundles distributed throughout ground
tissue
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petiole
axillary bud
blade
node
sheath
blade
stem
node
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Taproot system of a California poppy
Fibrous root system of a grass plant
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Cell types

• Parenchyma Thin cell wall, still can divide.
  Forms all new growth, and wound repair.
• Collenchyma Cell wall thick in the corners,
  gives elastic support to leaf petioles, young
  stems
• Sclerenchyma Very thick cell walls (has a extra
  3 layers) can not divide. Forms fibers and wood.
• Paper, cloth, wood

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Do not post on Internet
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Vascular Tissues

• Xylem carries water up from the roots
• Xylem is dead and hollow at maturity
• Functions like straws
• Tracheids, Xylem vessels, and fibers for support
• Phloem carries sugars through out the plant
• Alive at maturity. Uses active transport
• Sieve tube members and Companion Cells

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pit in cell wall
one vessel member
sieve plate
cytoplasm absent (cells dead at maturity)
sieve-tube member
companion cell (living)
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Leaf Structure

• Leaves do most of photosynthesis, export excess
  sugar in phloem.
• Middle, Mesophyll layer has all the chloroplasts.
• Stomata in epidermis layers open to let carbon
  dioxide in, oxygen out. As oxygen leaves so does
  water vapor.
• Stomata close if plant looses too much water.

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cuticle
upper epidermis
leaf vein
xylem
palisade mesophyll
phloem
spongy mesophyll
lower epidermis
water, minerals
products of photosynthesis
cuticle-coated cell of lower epidermis
one stoma
oxygen and water vapor
carbon dioxide
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Plant growth

• Meristems
• Primary growth
• Apical meristem
• Shoot and root
• Secondary growth
• Lateral meristem
• Vascular cambium
• Shoot and root
• Cork cambium

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activity at meristems
SHOOT APICAL MERISTEM Source of primary growth
(lengthening) THREE PRIMARY MERISTEMS Protoderm
epidermis Ground
meristem ground
tissue Procambium primary vascular
tissues
new cells elongate and start to differentiate into
primary tissues
new cells elongate and start to differentiate into
primary tissues
ROOT APICAL MERISTEM Apical meristem near all
root tips gives rise to protoderm, ground
meristem, and procambium These give rise to the
roots primary tissue systems epidermis, ground
tissues, and vascular tissues
activity at meristems
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vascular cambium
secondary phloem
cork cambium
secondary xylem
thickening
LATERAL MERISTEMS Two lateral meristems in older
stems and roots of woody plants produce
secondary growth (increases in diameter) Vascula
r cambium secondary vascular
tissues Cork cambium periderm
(replaces epidermis)
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Primary Growth

• Shoot apical meristem
• Adds height to stem, depth to root system
• Forms Primary Tissues
• Protoderm becomes epidermis
• Ground meristem becomes ground tissue
• Procambium becomes vascular tissues

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VASCULAR CYLINDER
endodermis
fully grown root hair
pericycle
xylem
phloem
cortex
epidermis
Vessels have matured root hairs and vascular
cylinder about to form
Cells elongate sieve tubes form and mature
vessel members start to form
Most cells have stopped dividing
Cells are dividing rapidly at apical and primary
meristems
quiescent center
root cap
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primary xylem
terminal bud
lateral bud
primary phloem
VASCULAR CAMBIUM
secondary xylem
secondary phloem
Twig from a walnut tree (Juglans) in winter,
after its leaves dropped
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Secondary Growth

• Starts after primary growth has move farther up
  stem/root.
• Vascular cambium adds more cells, adding girth to
  stem/root.
• Secondary xylem is wood accumulates as long as
  plant is alive.
• Secondary phloem becomes part of bark and falls
  off with bark as trunk expands.

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Pattern of activity at vascular cambium
outer surface of stem or root
division
division
One of the cells of vascular cambium at the
start of secondary growth
One of the two daughter cells differentiates into
a xylem cell (coded blue), and the other remains
meristematic
One of the two daughter cells differentiates into
a phloem cell (coded pink), and the other remains
meristematic
The same pattern of cell division and
differentiation into xylem and phloem cells
continues through the growing session
direction of growth
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Bark Protects the outer layers
secondary phloem
HEARTWOOD
SAPWOOD
periderm
BARK
vascular cambium
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Winter twig shows both primary and secondary
growth
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Roots
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Dicot Root

• 10 xylem
• 10 phloem
• Vascular cambium
• Pericycle
• Endodermis

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Monocot Root
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Monocot Root

• Epidermis
• Endodermis
• Pith
• Pericycle
• Xylem
• Phloem

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Leaves
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Monocot leaf