Plant Structure

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Plant Structure
Station 10

• Roots
• Absorb water and nutrients
• Anchor plants in ground
• Stems
• support plant body
• transport nutrients among
• plant parts
• Leaves
• carry out photosynthesis
• funnel water to root
• exchange sites for oxygen and carbon dioxide

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Station 10
Root, Stem and Leaf The Wetlands Vital Tissues
WHEN WE TALK ABOUT a land-loss crisis in
coastal Louisiana, were really talking about a
plant-loss crisis, says Rex Caffey, wetlands and
coastal resources specialist at Louisiana State
University. Land loss is just the inevitable
consequence of losing vegetation. Although
wetland plants may seem to lack allure,
professionals like Caffey insist that they are
the foundation of coastal restoration. And with
good reason when you consider the significance
and scope of plants four basic functions
Plants build and stabilize soil. Trapping
particles of waterborne sediment among their
roots, stems and leaves, plants slowly accumulate
the thick mud of the marshes and keep soil from
washing away. Vegetative cover protects existing
soil substrates from erosion and nutrient loss,
while dead and decomposing plant biomass further
increases soil volume and improves soil
structure. Plants create habitat. All organisms
in the wetlands, from microbes to alligators,
depend on plants or plant-eating animals for
nutrition. As well as supplying food, wetland
vegetation provides shelter, breeding grounds and
nurseries for a profusion of marine organisms,
waterfowl and terrestrial wildlife. Plants
purify water. Plants contribute to aquatic health
by absorbing large quantities of nutrients and
chemicals from water and sediment. By diminishing
the nutrient load and immobilizing toxins, plants
reduce contamination both in groundwater and
downstream. Plants shield infrastructure. The
physical barrier of a single stem appears
negligible, but thousands of acres of plants
effectively absorb destructive wave energy and
reduce damaging storm surge. Plants are a living
shield against the sea, protecting Louisianas
coastal infrastructure as well as its natural
environment.
http//www.lacoast.gov/WaterMarks/2005-04/1vitalTi
ssue/index.htm
Versatile, hardy and fast-growing, smooth
cordgrass is a popular choice for holding soil
and stabilizing land. The Chandeleur Islands
Restoration Project, shown here, planted smooth
cordgrass to stabilize more than four miles of
barrier island shoreline. NOAA Restoration
Center, Erik Zobrist
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Specialized Plant Tissue
Station 11

• 1. Meristematic Tissue - plant tissue found only
  in the tips of shoots and roots responsible for
  plant growth
• Apical Meristem group of cells that divide to
  produce increased length in stems and roots

• 2. Dermal Tissue
• outer covering of plants
• single layer of epidermal cells
• covered with waxy cuticle that protects against
  water loss
• 3. Vascular Tissue
• Transports water and nutrients
• Xylem up and Phloem down
• Consist of tracheids and vessel elements
• 4. Ground Tissue Tissue between the dermal and
  vascular tissue

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Station 11
5
Ground Tissue
Station 11
These cell types are all found in ground tissue
which forms most of the bulk of a plant.
Parenchyma are the least specialized. They have
thin walls, numerous plastids including
chloroplasts, and can revert to meristem in
response to injury. Collenchyma are elongated
cells with thick walls. They provide flexible
support. Sclerenchyma have very thick walls and
are dead at maturity. They may form long fibers,
as in flax, or be short as in nut shells and the
gritty material in pear fruits.
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Fibrous Roots vs. Taproots
Station 12
Fibrous roots are shallow and wide-reaching mono
cots tend to have fibrous roots Taproots are DEEP
and concentrated downwards dicots tend to have
taproots
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Root Structure and Growth
Station 12
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Water Transport in a Root
Station 12
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Station 13
Stems

• Node - point on a stem where a leaf is attached
• Internode - region between nodes on plant stems
• Bud - plant structure containing undeveloped
  tissue that can produce new stems and leaves

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Stems
Station 13
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Station 13
Layers of a Tree Trunk
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Transport in Plants 
Station 14

• The combination of root pressure, capillary
  action, and transpiration provides enough force
  to move water through the xylem tissue of even
  the largest plant.
• Capillary action water moves upward through
  narrow tubes against the force of gravity
  (adhesion and cohesion)
• contributes to the movement of
• water up the cells of xylem tissue

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Food Transport
Station 14

• Phloem
• Movement from source (where sugars are produced
  by photosynthesis) in leaves to where sugars are
  used or stored
• When nutrients are pumped into or removed from
  the phloem system, the change in concentration
  causes a movement of fluid in that same
  direction. As a result, phloem is able to move
  nutrients in

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Stem adaptations
Station 14
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Leaves
Station 15
SIMPLE LEAVES Botanists have established the
ground plan for a leaf as consisting of a broad
blade, on a leaf stalk (petiole) and with two
broad places where the leaf joins the stem which
are called stipules. Some or all of these may be
missing.
Compound leaves The blade part separated into
smaller pieces.This Peltophorum leaf has the
leaflets coming off what would be the midrib of
the leaf blade. It is a little like a feather in
its form The botanical term is pinnate.(This
leaf is actually twice- or bipinnate because each
leaflet is divided into smaller pieces.)
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Station 15
The Internal Structure of a Leaf
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Tendrils, pea plant (top left) spines, cacti
(top right) succulents Modified leaves (bottom
left) brightly-colored leaves, poinsettia
(bottom right)
Station 15
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Station 16
Controlling Transpiration Function of Guard
Cells in gas exchange

• To understand what regulates the rate of
  transpiration, it helps to follow the path water
  takes through a leaf.
• Water enters the leaf through the xylem and moves
  into the spongy mesophyll.
• This movement of water into the leaf raises the
  water pressure in the guard cells, opening the
  stomata.

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Station 17
Plant Hormones

• Substance that is produced in one part of an
  organism that affects another part of that same
  organism
• Main plant hormones
• Auxins
• Gibberellins
• Ethylenes

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Station 17
Auxins

• Result in plant bending in response to light
• Also result in stems going up and roots going
  down
• Plants that have their tops trimmed out will get
  bushy plants that are slimmed from the sides
  will be thinner and taller

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Station 17
Gibberellins and Ethylene

• Giberellins produce dramatic increases in size
  particularly in stems and fruit
• Ethylene in response to auxins, fruit tissues
  release ethylene which causes ripening

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Other Important Plant Chemicals
Station 17
Abscisic acid Abscisic acid suppresses cell
growth. It also promotes leaf senescence (death)
which results in the color changes of leaves in
autumn before they are dropped from deciduous
plants. Abscissic acid also appears to be
involved in stomatal opening and closing. It may
have a role in root gravitropism.
Phytochromes These chemicals change in
concentration in plants in response to changes in
length of dark (night)/light (day) periods. In
turn, these changes in phytochromes stimulate or
repress the flowering of plants. There are two
categories of plants with respect to flowering.
Short day plants flower in response to long
nights. Long day plants flower in response to
short nights. (The names now seem silly, as it is
the night length rather than day length which is
the stimulus for the response. But this is an
example of many scientific discoveries the
response was observed, and named, long before the
mechanism of its action was worked out.)
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Station 18
Plant Responses and Adaptations

• Tropisms responses of plants to environmental
  stimuli
• Types of tropisms
• gravitropism
• phototropism
• thigmotropism

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Station 18
Gravitropism and Phototropism
Gravitropism response of a plant to gravity
stems go up, roots go down Phototropism
response of a plant to light (bending toward
the light)
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Station 18
Thigmotropism

• Response of plants to touch
• Can stunt growth
• Can cause twining of plant tendrils with vines
  and climbing plants
• Can have as a quick response Venus flytrap

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Compare/Contrast Table plant adaptations
Station 18
Section 25-3
Comparing Carnivorous Plants, Epiphytes, and
Parasites
Characteristics Environment Method of obtaining
nutrients Examples
Carnivorous Plants bog leaves that trap and
digest insects pitcher plant, sundew, Venus
flytrap
Epiphytes host plant gather moisture from
rainfall and produce their own food Spanish moss,
orchid
Parasites host plant extract moisture and
nutrients from host plant dodder, mistletoe