CASE STUDY SCENARIO

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• CASE STUDY SCENARIO
• In order to discuss plants in a meaningful way,
  it is important to know the proper names for all
  the different parts a plant can have.
• Flowering plants have four major part types
• Leaves
• Flowers
• Stems
• Roots
• LeavesLeaves make all the food for the plant.
  They do this by changing light, water and gases
  into food. This process is called photosynthesis.
• How are the leaves structurally adapted as
  photosynthesizing organs?

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• EXTERNAL STRUCTURE
• This refers to the morphology of the leaf(outer
  side)
• All leaves are responsible for absorbing the
  sun's rays
• the majority of photosynthetic production (which
  can take place in any green part of a plant),
• taking in carbon dioxide and releasing oxygen and
  water vapor (breathing)
• removing waste products from the plant
• using osmotic pressure to draw water up from the
  roots
• PARTS OF A LEAF
• Tip of the terminal point of the leaf is the
  leaf Apex. Lamina the flattened, green, expanded
  portion of a leaf. Margin edge of a leaf.  Midrib
  the most prominent central vein in a leaf. 
  Lateral veins secondary veins in a leaf.  Petiole
  the leaf stalk (connects blade to stem).

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• INTERNAL STRUCTURE
• The leaf is covered by two layers. The Upper
  epidermis and the Lower epidermis. Between these
  two layers is a Mesophyll tissue layer made up of
  the Palisade cells and the spongy cells.

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Cuticle - Is non-cellular, water proof and
transparent. It allows light to pass through.
Upper epidermis - Is a single layer of cells on
the upper surface of a leaf. It allows light to
pass to the cells below. Palisade mesophyll -
has cells vertically arranged such that many can
fit into a small space. The cells have large
number of chloroplasts. Chloroplasts- contain
chlorophyll for absorbing sunlight. Spongy
mesophyll - Have large air spaces for fast
diffusion of gases to and from the
photosynthesizing cells. The cells have few
chloroplasts. Veins (Vascular bundles) - They
act as drain pipes distributing raw materials to
the leaves and conducting away manufactured food
to other parts of a plant. Stoma - A pore that
allows gaseous exchange to take place. Carbon
dioxide enters and oxygen leaves the leaf through
stomata. Thin lamina - Provides a short
distance over which diffusion of gases take
place. Broad lamina - Some leaves have a broad
lamina which provides a large surface area for
absorbing sunlight energy.
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• EXCERCISES
• QUESTION 1
• Name 4 main parts of the leaf
• Which of these above mentioned parts serve a
  vital role for photosynthesis?

QUESTION 2 Fill in the missing words ----------
Is non-cellular, water proof and transparent. It
allows light to pass through. ----------------
Is a single layer of cells on the upper surface
of a leaf. It allows light to pass to the cells
below. ----------------- has cells vertically
arranged such that many can fit into a small
space. The cells have large number of
chloroplasts. ---------------- contain
chlorophyll for absorbing sunlight.
---------------- Have large air spaces for fast
diffusion of gases to and from the
photosynthesizing cells. The cells have few
chloroplasts. ---------------- A pore that
allows gaseous exchange to take place. Carbon
dioxide enters and oxygen leaves the leaf through
stomata.
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References 1.Mckean D.G (1973), introduction to
Biology, Hodder Murry (UK) London. 2. Ian J.
Burton (2001), the Cambridge Revision Guide GCE,
level Biology,    Cambridge University
Press. 3.Maxwell Ojo.B (1998), Modern Tropical
Biology, Evans and Brothers London(UK) 4.Stone
R.H and Cozens A. B. (2002), New Tropical Biology
(3rd Edition)    Longmans, London (UK).