Download File - nowyoudothemath

Plant Structure
• One of the distinguishing characteristics that you
may recall from the diversity unit is that all plants
carry out the process of photosynthesis.
• This process is essential not only for the survival
of a plant, but for the survival of all living things.
• The organelle whose duty it is to carry out this
daunting task is the chloroplast.
• The image on the next slide highlights all the
components of a plant cell.
• You should be able to describe the function of all
the organelles shown below. If not, then please
take the time to review.
Kind hearts are the gardens,
Kind thoughts are the roots,
Kind words are the flowers,
Kind deeds are the fruits,
Take care of your garden
And keep out the weeds,
Fill it with sunshine
Kind words and kind deeds.
Henry Wadsworth Longfellow
Please read the handout NOW.
Roots
• There are many analogies equating roots with
positive attributes like strength, stability, and
support.
• A person who has strong roots implies that he or
she has a solid foundation that is built upon firm
principles.
• It is no surprise then to learn that those qualities
that are assigned to people are the same qualities
that roots provide to plants.
• In addition to anchoring plants in soil, roots also
absorb and transport water and minerals to the
stems.
• Not all roots are the same.
• Tap roots grow deep into the ground in search of
nutrients. They are generally large and fleshy and
store food which is necessary for perennial plants
(plants that last more than two growing seasons)
which experience periods of dormancy.
• Fibrous roots do not dig deep into the soil; rather
they arrange themselves close to the soil surface
and collect water and nutrients before they sink
deep into the ground.
• Adventitious roots are found in climbing plants
like ivy. These roots develop from other plant
tissue like stems and leaves. Adventitious roots
can help support a plant.
• Roots contain tiny little projections called root hairs.
• The root hairs absorb water and nutrients from the
soil.
• Much like alveoli that increase surface area for gas
exchange, the root hairs amplify the surface area
which increases the rate of absorption.
Stems
• Stems provide the structural and physical support
to leaves and flowers.
• The stems hold the leaves and flowers in a
position that will allow for nutrient gathering and
reproduction.
• Xylem and phloem cells transport materials
within the stem from areas of plenty to areas of
need.
• The xylem and phloem cells are arranged in
vascular bundles.
• Within these bundles, the phloem cells are
always situated closer to the outside of the stem
while the xylem cells are located closer to the
centre of the stem.
• There is a thin layer of
tissue that separates
the xylem from the
phloem in dicot plants.
• Stems also store
nutrients for future use.
• Rhizomes, tubers, and
bulbs are all types of
stems that have been
modified to suit the
needs of a plant.
• Tubers grow underground and develop buds called eyes.
These buds grow into new shoots above the ground.
• Bulbs are small stems that grow underground. They
usually have short and thick leaves.
• Rhizomes grow just below the surface of the ground and
are thick and fleshy. They can survive through the winter
and develop buds in the spring.
• There are two main types of stems.
• Herbaceous stems are soft and green
and woody stems are more complex and are
hard.
• Most trees and plants that can survive
through winter have woody stems. Woody
stems grow thicker over time.
• Each year a new layer forms and the stem of
the tree widens.
• This is the result of new xylem being formed
each spring. The older xylem no longer
transports fluids and fills with oils and other
chemicals to become heartwood.
• The vascular cambium appears as rings when looking
at the cross section of a woody stem.
• The rings can be counted to determine the age of the
tree. The outer part of a woody stem is called the
bark. The bark is composed of phloem cells and cork
tissue. These cells and tissues protect the stem from
water loss.
Leaves
• The primary site of photosynthesis occurs at
the leaves.
• Leaves are positioned on trees to receive and
absorb the sun's rays.
• This is necessary to drive the process of
photosynthesis.
• Leaves have many variations in their shape,
size and structure.
• A compound leaf contains a leaf that is
divided into many smaller leaflets.
• A simple leaf has just one blade.
Compound Leaves
Simple Leaves
• A leaf is made up of many specialized cells and
tissues as illustrated in the image below:
• 1. Cuticle - The cuticle is a waxy, water resistant
covering that protects the leaf from excessive
absorption of light and evaporation of water.
• 2. Upper Epidermis - These cells appear on the top of
the leaf and are transparent and colourless. They allow
light to pass through to mesophyll cell where most of
photosynthesis takes place. The epidermis lack
chloroplasts therefore no photosynthesis takes place.
• 3. Palisade Mesophyll - These cells are arranged close
together and contain chloroplasts. These
photosynthetic cells form the bulk of plant leaf.
• 4. Spongy Mesophyll - These cells also contain
chloroplast, but not as many as the palisade cells. The
spongy mesophyll cells are not as densely packed
together. This allows more surface area for gas
exchange.
• 5. Lower Epidermis - These cells appear on the
bottom of the leaf and are transparent and
colourless. They allow light to pass through to
mesophyll cell where most of photosynthesis
takes place. The epidermis lack chloroplasts
therefore no photosynthesis takes place.
• 6. Stoma - Stomata (pl.) are small openings
located on the underside of the leaf of most
plants. These small openings allow for oxygen,
carbon dioxide, and water vapour to move into
and out of the leaf.
• 7. Guard Cells - Guard cells are specialized
epidermal cells that contain chloroplasts. Guard
cells regulate the opening and closing of the
stoma. When weather conditions are hot and dry,
the guard cells collapse and the stoma closes.
• The process that regulates the opening and
closing of the stoma involves the movement
of ions and water.
• This animation shows how the shape of the
guard cells affects the condition of the stoma.
• Well it would if it worked! Grrrrrr.
• 8. Xylem - Xylem are
specialized structures
that transport water
and minerals from the
roots to the rest of the
plant.
• 9. Phloem - Phloem
cells are specialized
structures that
• 10. Vascular Bundle - The
transport
veins of the leaf contain
carbohydrates
both xylem and phloem
produced in the leaves
cells.
to all parts of the
plant.
Homework
• Roots contain specialized cells and tissues.
• Determine the role of the:
Epidermis, Cortex, Endodermis and
Vascular Cylinder.
• If you use the Internet, be sure to use
academic sites.