Introduction to Horticulture

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Introduction to Horticulture

• By Carrie Carson

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The Importance of Plants

• Without plants, life on earth could not exist
• Plants are the primary source of food for humans
  and animals

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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

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Parts of the Plant

• Most plants are made up of four basic parts
• Leaves
• Stems
• Roots
• Flowers (these later become fruit or seeds)

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Leaves

• 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
  animals

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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
  plants

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Leaf Arrangement

• Leaves are arranged in many different patterns
  and positions
• Alternate
• Opposite
• Whorled
• Simple
• Pinnate
• Bi-Pinnate
• Palmate

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Leaves on the Outside

• Parts
• - Petiole - Blade - Vein
• - Midrib - Margin

Tip
Margin
Midrib
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Leaf Parts cont.

• Petiole - leaf stalk
• Blade - the larger, usually flat part of the leaf
• Midrib - large central vein from which all other
  leaf veins extend
• Veins - form the structural framework
• Margins - edges of plant leaves

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Leaves on the Inside

• Leaves have specialized cells that perform very
  important, very specific tasks.

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Leaf Cells

• Epidermis - skin of the leaf
• Single layer of cells
• Chief function protect the leaf from loosing too
  much moisture
• 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)

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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 O2 there would be no burning, rusting, or
  rotting

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6H2O 6CO2 ----------gt C6H12O6 6O2
Photosynthesis
LIGHT
Six molecules of water plus six molecules of
carbon dioxide in the presence of light produce
one molecule of sugar plus six molecules of oxygen
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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 part

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Respiration

• Plants breathe 24/7
• They consume O2 and release CO2
• Roots, stems, and leaves all need O2 to grow
• Plants produce more O2 during photosynthesis than
  they consume while breathing

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Stems

• Stems have 2 main functions
• The movement of materials
• Movement of water and minerals from roots up
  towards the leaves
• Movement of manufactured food from the leaves
  down to the roots
• Support of the leaves and reproductive structures
• Flowers and fruit or seeds

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Stems cont.

• Stems are also used for
• Food storage
• Irish Potato
• Reproductive methods
• Stem cuttings or grafting
• Green stems manufacture food just like leaves

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Stems on the Outside

• Lenticels
• Breathing pores

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Stems on the Outside cont.

• Bud scale scars
• Indicate where a terminal bud has been located
• The distance between two scars represents one
  year of growth
• Leaf scars
• Show where leaves were attached

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Unique Stems

• Irish Potato Gladiolus
• Very different stems
• Stems are used for food storage and plant
  reproduction

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Stems on the Inside

• In all stems
• Water and minerals travel up the XYLEM
• Manufactured food travels down the PHLOEM

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Dicots

• Dicots (2 cotyledons) 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

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Monocots

• One cotyledon (seed leaf)
• Grasses, corn
• No outside cambium
• Vascular bundles that contain xylem phloem
• Cells dont increase in number, they grow in size
  (wont keep growing like a tree)

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Monocots vs. Dicots
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What do we do with Stems?

• Food
• Asparagus
• Irish Potato
• Celery
• Building Materials
• Wood

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Roots

• 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

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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 inside

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• Phloem
• Carries manufactured food down to the root for
  food storage
• Xylem
• Carries water and minerals up to the stem

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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

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Root External Structure

• Behind the root cap are root hairs
• Root hairs become side roots that branch out as
  the root grows older
• Absorb moisture and minerals which are conducted
  up to the larger roots and the stem

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Roots as Crops

• Cash crops
• Carrots
• Beets
• Sugar Beets - Sugar
• Radishes
• Sweet Potatoes

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Root Propagation

• Plants with tuberous roots
• Dahlia
• Peony
• Sweet Potato
• Are propagated by separating the root clump or
  by rooting spouts from the root

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Types of Root Systems

• Fibrous Root System vs. Tap Root System

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• Which root system is easier to transplant?
  Fibrous roots or tap roots?
• Answer Fibrous roots
• Why? Because when plants are dug up out of the
  ground, a greater of the fibrous roots system
  is saved.

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• 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 ground

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Flowers, Fruits, Seeds

• Flowers are pretty contain nectar in order to
  attract insects
• These insects fertilize the flower by pollination
• Pollination begins fruit and seed formation

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Fruits Seeds

• Fruits and seeds are eaten, collected, and spread
  out by animals and people
• This reproduces the plant

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Seeds

• Seeds have special devices to ensure propagation
• Some seeds are sticky (thistles), some float in
  the wind (dandelions), others can survive stomach
  acid (cherry pits)

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Flower Parts

• Flowers differ in shape, size, and color, but
  all have relatively the same parts

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Flower Parts cont.

• Seeds are the most common way plants reproduce in
  nature
• Sexual process involving male and female parents
• A complete flower has both male and female parts
• Only one parent is needed if a plant is
  self-fruitful, or can pollinate itself

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Flower Parts cont.

• 4 main parts
• Sepals
• Petals
• Stamens
• Pistil

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The Sepals

• Green, leaf like parts of the flower that cover
  and protect the flower bud before it is open

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Petals

• Are actually leaves
• Generally the most striking part of the flower
• Bright colors are used to attract insects for
  pollination

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The Stamens

• Male reproductive part
• Each stamen consists of
• Filament
• Anther contains the pollen (male sex cell)

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The Pistil

• Located in the center
• of the flower
• Female part
• Produces female sex cells (eggs or ovules)
• If fertilized, the eggs become seeds

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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 coat

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Flower Construction

• Insects looking for nectar have to climb over the
  anther and brush pollen on their legs
• As they climb towards the center looking for
  food, they deposit pollen on the stigma

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Fertilization

• After an insect deposits pollen, fertilization
  begins!
• The pollen grain
• sprouts and sends
• a long stalk (pollen
• tube) down
• the style to the
• ovary

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Fertilization cont.

• The pollen sperm cell can then fertilize the
  female egg cells and seeds begin to develop
• The ovary enlarges into a seed coat or fruit

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Pollen
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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

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Flowers are Important!

• Many plants are grown only for their flowers
• Floriculture industry in a multimillion dollar
  business!!!