Plant Structure and Tissue

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Plant Structure and Tissue

• http//www.howe.k12.ok.us/jimaskew/

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I. Plant Tissue

• Ground Tissues - provides storage,
• metabolism, and support.

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• a. Parenchyma
• Large, loosely packed, rectangular cells with
  thin cell walls.
• Responsible for photosynthesis and food storage.
• Over 80 of the cells in non-woody plants.

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• b. Collenchyma
• Elongated cells with uneven, flexible, thicker
  cell walls.
• This tissue supports the growth regions of a
  plant.
• c. Sclerenchyma
• Cells are short-lived with thick cell walls. Has
  a second cell wall
• Serves to support the plant.
• The cells that give a plant its "woody"
  characteristics.

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• 2) Dermal Tissues - forms the outside covering of
  plants and provides protection.

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• a. Epidermis
• The outer layer of cells.
• Protects the plant and reduces water loss
  (cuticle)
• b. Stomata
• Regulate gases passing into and out of the plant
• Usually located on the under side of leaves.
• Guard cells regulate the opening by changing
  water pressure within the cell to swell or
  shrink.
• c. Cork closely packed cells protecting a woody
  stem.

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• 3) Vascular Tissues - transport water and food
  through the plant.

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• Phloem straw-like tubes conducting food downward
  in a plant.
• b. Xylem straw-like tubes conducting water and
  minerals upward in a plant.

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Water is moved to the tops of very tall trees by
capillary action, the adhesion/cohesion of water,
transpirational pull, and root pressure.PRESSURE-
FLOW HYPOTHESIS
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Warm-up (3/29 3/30)

• Turn in plant drawings and pick up a
  transpiration lab
• What type of plant has vascular tissue and no
  seeds?
• A flowering plant with 6 petals and parallel leaf
  veins is known as what?
• What type of tissue protects the plant from
  drying out?
• Which type of vascular tissue moves water up the
  plant?

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Objectives

• Mosses, Ferns, Gymnosperms, Angiosperms
• Ground, Dermal, and Vascular Tissue
• Primary vs. Secondary Growth
• Leaf, Root, Stem, Flower Parts
• Hormone functions in plants
• Plants responses to the environment

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II. Plant Growth

• Meristems growth regions where cells divide
  rapidly and tissue differentiation occurs.

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Two patterns of growth in seed plants 1) Primary
growth- elongation of stems and roots Apical
meristem - located at the tips of stems and
roots. Apical meristems produce growth in
length,
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• 2) Secondary growth - roots, stems and branches
  of certain seed plants grow wider
• Two types of lateral meristems
• Vascular cambium - located between the xylem and
  phloem, producing additional vascular tissues.
  (inside - creates rings)
• Cork cambium - located outside the phloem,
  producing cork replacing epidermis.

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III. Plant Structure
Plants have three basic parts
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A. Leaf

• Function
• - leaves capture light from the sun
• - leaves make glucose through photosynthesis
• - leaves take-in CO2 release oxygen O2

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• 2) Structure
• - top layer is made of a waxy cuticle (prevents
  H2O loss) and epidermis
• -middle layer is the mesophyll (spongy layer)
• -bottom layer exchanges gases through the stomata

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Image of a Stomata
Guard Cells
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B. Stems

• Function
• - stems support the plant
• - stems hold the leaves toward the sunlight
• - inside the stem water and nutrients travel
  to other plant parts
• - stems of some plants store glucose in the form
  of starch

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• 2) Types of stems
• a) Woody stem- found in trees and shrubs
• b) Herbaceous stem- found in flowers and grasses

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Stem (Wood)
SAPWOOD - Active xylem
HEARTWOOD - Inactive xylem
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Annual Rings
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C. Roots

• Function
• - Roots support and anchor the plant (Similar to
  Rhizoids)
• - Roots absorb water and minerals from the soil
• - Roots store glucose (starch)
• Root cell growth pattern Division, elongation,
  and differentiation

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• 2) Structure
• Taproot system - the primary root grows much
  larger than the other roots of the plant.
• Fibrous root system - the primary root does not
  grow large so that many roots of the plant are
  similar in size.
• Primary root - the first root to grow out of a
  seed.
• Adventitious roots - specialized roots that grow
  from plant stems or leaves.
• Root cap - a shield of parenchyma cells covering
  the apical meristem at the root tip.
• Root hairs - small extensions of a root, these
  greatly increase the surface area of the root for
  absorption.

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• 3) Typesof roots
• - Taproot
• - Fibrous
• - Aboveground

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Label the Roots
Fibrous
Taproot
Aboveground
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Epiphytes Plants that are not rooted in soil but
instead grow directly on the bodies of other
plants. Most are found in tropical rainforest
biomes and they are NOT parasitic.
Spanish Moss
Orchid
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IV. Plant HormonesChemical messengers that
affect a plant's ability to respond to its
environment.

• Auxins - hormones that promote plant-cell
  elongation, apical dominance, and rooting.

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IV. Plant HormonesChemical messengers that
affect a plant's ability to respond to its
environment.

• Gibberellins - a group of hormones that primarily
  stimulate elongation growth.

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IV. Plant HormonesChemical messengers that
affect a plant's ability to respond to its
environment.

• Ethylene - the hormone responsible for the
  ripening of fruit.

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IV. Plant HormonesChemical messengers that
affect a plant's ability to respond to its
environment.

• Cytokinins - a group of hormones that promote
  cell division.
• Abscisic acid - a hormone that generally inhibits
  other hormones.

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V. Plant Response

• 1) Tropisms plant movement toward or away from
  an environmental stimulus.
• Phototropism - a growth response to light. Solar
  tracking is the phototropism of leaves or flowers
  as they follow the sun's movement across the sky.

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Phototropism
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V. Plant Response

• 1) Tropisms plant movement toward or away from
  an environmental stimulus.

• Thigmotropism - a growth response to contact with
  a solid object. Thigmotropism allows vines to
  climb. It is thought that an auxin or ethylene
  are involved in this response.

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V. Plant Response

• 1) Tropisms plant movement toward or away from
  an environmental stimulus.
• Gravitropism - a growth response to gravity.
  Roots are positively gravitropic, usually growing
  downward and stems are negatively gravitropic,
  usually growing upward. Auxins are probably
  responsible for this growth.

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V. Plant Response

• 1) Tropisms plant movement toward or away from
  an environmental stimulus.
• Chemotropism - a response to chemicals. The
  growth of a pollen tube is in response to
  chemicals produced produced by the plant ovary.
• Hydrotropism - a response to water. Most plants
  have a positive response to water.

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• 2) Photoperiodism plant response to changes in
  the length of days and nights.
• Critical length is the length of daylight above
  or below which a species of plant will flower.
• Long-day plants flower only when exposed to day
  lengths longer than their critical length. These
  are usually late spring and early summer flowers.
  
• Short-day plants flower only when exposed to day
  lengths shorter than their critical length. These
  are usually early spring and fall flowers.
• Day-neutral plants are not affected by the length
  of days and nights.

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Plant Adaptations Aquatic plants To take in
sufficient oxygen, aquatic plants, have tissues
with large air-filled spaces through which oxygen
can diffuse. Stomata located on top of
leaf! Desert plants Have extensive
roots, reduced leaves, and thick stems that can
store water. Leaves are modified to reduce
evaporative water loss and, often, to deter
herbivores.
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Nutritional Specialists Plants that have
specialized features for obtaining nutrients
include carnivorous plants and parasites.
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Chemical Defenses Many plants defend themselves
against insect attack by manufacturing compounds
that have powerful effects on animals.