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					  Introduction to
    Importance of Plants
Plant Parts & Their Functions
     The Importance of Plants
• Without plants, life on earth could not exist
• Plants are the primary source of food for
  humans and animals
 The Importance of Plants cont.
• Plants also:
  – Provide oxygen
  – Provide shade
  – Supply us with medicines
  – Renew the air
  – Slow down the wind
  – Hold soil in place
  – Are a home for wildlife
  – Furnish building materials and fuel
            Parts of the Plant
• Most plants are made
  up of four basic parts:
  – Leaves
  – Stems
  – Roots
  – Flowers (these later
    become fruit or seeds)
• Usually underground – not visible
• Functions:
  – Anchor the plant and hold it upright*
  – Absorb water and minerals from the soil &
    conduct them to the stem*
  – Store large quantities of plant food*
  – Propagate or reproduce in some plants

  * = essential to all plants
          Roots on the Inside
• Very similar to a stem
• Older roots of shrubs
  & trees have:
  – Phloem on the outside
    (old phloem is bark)
  – Cambium layer
  – Xylem (wood) on the
• Phloem
  – Carries manufactured food down to the root for food
• Xylem
  – Carries water and minerals up to the stem
        Roots on the Outside
• Different from a stem
• On a stem, the
  terminal bud
  initiates growth
• On a root,
  the root cap
  initiates growth
• Root cap continuously
  makes new cells that
  protect the root as it
  pushes into the soil
       Root External Structure
• Behind the root cap
  are root hairs
• Root hairs become
  side roots that branch
  out as the root grows
• Absorb moisture and
  minerals which are
  conducted up to the
  larger roots and the
              Roots as Crops
• Cash crops
  –   Carrots
  –   Beets
  –   Radishes
  –   Sweet Potatoes
           Root Propagation
• Plants with tuberous
  – Dahlia
  – Peony
  – Sweet Potato
• Are propagated by
  separating the root
  clump or by rooting
  spouts from the root
   Types of Root Systems
Fibrous Root System vs. Tap Root System
•   Stems have 2 main
    – The movement of
       • Movement of water and
         minerals from roots up
         towards the leaves
       • Movement of
         manufactured food from
         the leaves down to the
    – Support of the leaves
      and reproductive
       • Flowers and fruit or
                   Stems cont.
• Stems are also used
• Food storage
  – Irish Potato
• Reproductive
  – Stem cuttings or
• Green stems
  manufacture food just
  like leaves
       Stems on the Outside
• Lenticels
  – Breathing pores
   Stems on the Outside cont.
• Bud scale scars
  – Indicate where a
    terminal bud has been
  – The distance between
    two scars represents
    one year of growth
• Leaf scars
  – Show where leaves
    were attached
             Unique Stems
• Irish Potato & Gladiolus
  – Very different stems
  – Stems are used for food storage and plant
        Stems on the Inside
• In all stems:
  – Water and
    minerals travel
    up the XYLEM
  – Manufactured
    food travels
    down the
– Dicots (2 cotyledons - seed leafs) the xylem
  and phloem are separated by the cambium
– The cambium produces new cells
– Grow continually because the cambium builds
  new xylem and phloem cells
– Trees are a perfect example!
  • Sap = new xylem
  • Heartwood = old, inactive xylem
  • Tree bark = old, inactive phloem
• One cotyledon (seed leaf)
• Grasses, corn
• No outside cambium
• Vascular bundles that contain xylem &
• Cells don’t increase in number, they grow
  in size (won’t keep growing like a tree)
Monocots vs. Dicots
   What do we do with Stems?
• Food
  – Asparagus
  – Irish Potato
  – Celery
• Building Materials
  – Wood
• Which root system is
  easier to transplant?
  Fibrous roots or tap
• Answer: Fibrous
• Why? Because when
  plants are dug up out
  of the ground, a
  greater % of the
  fibrous roots system
  is saved.
• If a root loses to
  many root hairs
  while being
  transplanted, the
  plant will die.
• Larger roots only
  conduct & store
  water, nutrients,
  and food
• Root hairs absorb
  moisture from the
• Are the food factory of
  the plant
• They produce all of
  the food that is used
  by the plant and
  stored for later use by
  the plant or by
Leaves Come in All
Shapes and Sizes!
•   Needles are actually very narrow leaves
•   The thorns on a cactus are leaves
•   Some leaves are flat
•   Other leaves, like onion leaves, are cylindrical
•   The shape and size of leaves helps to identify
Leaf Arrangement
• Leaves are arranged
  in many different
  patterns and
  –   Alternate
  –   Opposite
  –   Whorled
  –   Compound
• Leaf Composition
  – Simple
  – Compound
       • Pinnate
       • Bi-Pinnate
       Leaves on the Outside
• Parts:
  - Petiole   - Blade             - Vein
  - Midrib    - Margin


            Leaf Parts cont.
• Petiole - leaf stalk
• Blade - the larger, usually flat part of the
• Midrib - large central vein from which all
  other leaf veins extend
• Veins - form the structural framework
• Margins - edges of plant leaves
       Leaves on the Inside
• Leaves have specialized cells that perform
  very important, very specific tasks.
                     Leaf Cells
• Epidermis - skin of the
  – Single layer of cells
  – Chief function: protect the
    leaf from loosing too much
  – Guard Cells - open and
    close a small space or pore
    on the underside of a leaf
    called a stoma to allow the
    leaf to breathe (exchange
    O2 for CO2) and transpire
    (or give off moisture)
             Leaf Cells cont.
• Chloroplasts
  – Food making cells
  – Chlorophyll - green color
• Photosynthesis
  – Process by which chloroplasts make food
  – The oxygen created is used directly by people
    and animals
  – Without oxygen there would be no burning,
    rusting, or rotting
6H2O + 6CO2 ----------> C6H12O6+ 6O2

Six molecules of water
plus six molecules of
carbon dioxide in the
presence of light produce
one molecule of sugar
plus six molecules of
               Plant Food
• Food made in the leaves moves down the
  stem to the roots
• It is then used by the plant or stored in the
  roots or stem as sugar, starch, or protein
• The plant is also used as food for people
  and animals
• The leaves are usually the most nutritious
• Plants always breathe
• They consume oxygen
  and release carbon
• Roots, stems, and leaves
  all need oxygen to grow
• Plants produce more
  oxygen during
  photosynthesis than they
  consume while breathing
     Flowers, Fruits, & Seeds
• Flowers are pretty & contain nectar in
  order to attract insects
• These insects fertilize the flower by
• Pollination begins fruit and seed formation
            Fruits & Seeds
• Fruits and seeds are eaten, collected, and
  spread out by animals and people
• This reproduces the plant
• Seeds have special devices to ensure
• Some seeds are sticky (thistles), some
  float in the wind (dandelions), others can
  survive stomach acid (cherry pits)
              Flower Parts
• Flowers differ in shape, size, and color,
  but all have relatively the same parts
          Flower Parts cont.
• Seeds are the most common way plants
  reproduce in nature
  – Sexual process involving male and female
• A complete flower has both male and
  female parts
• Only one parent is needed if a plant is self-
  fruitful, or can pollinate itself
         Flower Parts cont.
• 4 main parts
  – Sepals
  – Petals
  – Stamens
  – Pistil
             The Sepals
• Green, leaf
  like parts of
  the flower
  that cover
  and protect
  the flower
  bud before it
  is open
• Are actually leaves
• Generally the most striking part of the
• Bright colors are used to attract insects for
              The Stamens
• Male reproductive part
• Each stamen consists of:
  – Filament
  – Anther – contains the pollen (male sex cell)
                   The Pistil
• Located in the center
   of the flower
• Female part
• Produces female sex
  cells (eggs or ovules)
• If fertilized, the eggs
  become seeds
             Parts of the Pistil
• 3 main parts:
  – Stigma – sticky,
    catches the pollen
  – Style – tube that leads
    to the ovary
  – Ovary – eggs develop
    here, after fertilization
    the ovary grows to
    become a fruit or seed
        Flower Construction
• Insects looking for nectar have to climb
  over the anther and brush pollen on their
• As they climb towards the center looking
  for food, they deposit pollen on the stigma
• After an insect deposits pollen, fertilization
• The pollen grain
  sprouts and sends
  a long stalk (pollen
  tube) down
  the style to the
           Fertilization cont.
• The pollen sperm cell can then fertilize the
  female egg cells and seeds begin to
• The ovary enlarges into a seed coat or
          Incomplete Flower
• Has ONLY male parts or female parts
• Male flower – sepals, petals & stamens
  but no pistil
• Female flower – sepals, petals, & pistil, but
  no stamens
• Examples: Kiwi, Ginkgo
       Flowers are Important!
• Many plants are grown only for their
• Floriculture industry in a multimillion dollar
 What is the major
function of flowers?
      What is a fruit?
• A ripened flower ovary
• Botanically, fruits = vegetables
  & vegetables = fruits
• In most plants, a fruit is
  formed following fertilization of
  the ovules
• They contain seeds
What about seedless fruit?
• Seedless fruit -- fruit that form
  without pollination or fertilization
• These fruit are called
• Examples: Banana, navel
• When the fruit ripens, the ovary
  wall thickens.
• This is called the pericarp
• The pericarp has three
• The endocarp
• The mesocarp
• The exocarp
        Types of Fruits
• Aggregate fruits

• Multiple fruits

• Simple fruits

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