Transcript SAPS - African violets under the microscope powerpoint

What will I be learning today?
• Knowledge
• Plants have many different types of specialised cell
• Plant cells have similar features
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Investigation skills
Using / focusing a microscope
Making up your own slides
Interpreting what you see
African Violet
• Looking at some specialised cells using microscopes
African violet : Saintpaulia
Preparing a sample to investigate
• Take a small sample
from underneath a leaf
• Mount on a microscope
slide in a drop of water
• Care with scalpels and
glass
Stomata: what you can expect to see
• The pink pigment is
in some of the cells
• It is not in the guard
cells (or subsidiary
cells) so they look
white
Stoma (pore)
Subsidiary
Cell
Guard cell
Close up on guard cells
• Find a clear stoma
• Identify the guard cells
• Use x10 or x40 objective
lens
• Chloroplasts should be
clearly visible
chloroplasts
Trichomes (hairs)
• Made of several cells
• Form a physical barrier
• May produce chemicals
• May help conserve water
Air bubble
Trichomes
Close up on trichomes
• Find a big cell that’s part of
a trichome
• Focus it on the highest
magnification that you can
• Watch closely – you may
see the cell contents
moving
Other specialised cells
• Take thin slices
along leaf veins
• Or along leaf petioles
• You may see spirals
of lignin that
strengthen xylem cells
chloroplasts
Spiral lignin in xylem vessels
Pollen
• Set up a microscope slide with a
drop of water on it
• Remove a yellow anther from a
flower
• Crush a section of the anther into
the water using the blunt end of a
dissecting needle or tweezers
• Cover with a cover slip
Pollen grains
Petal Cells
• Prepare a slide with a drop
of water
• Tear a petal to expose a
ragged thin edge
• Place slices of the thin
edge into the water on the
slide
• Place a cover slip over the
petal tissue
Torn
thin
edge
Petal cells
• Dome shaped cells
• Maybe to allow
pollinators to get a
better grip on the
petals*
Leaf Structure
• Take thin cross sections
through a leaf
• Put these into a drop of
water on a microscope
slide
t
p
u
• Look for thin areas under
the microscope to
investigate the different
tissues
m
l
s
t
Successful learning today
Skills
- Did you learn any new skills today?
- What skills were they?
- If not – why do you think that was?
Knowledge
- What are hairs called on plants?
- Can you name more specialised cells in plants?
- Which cells that you have seen have chloroplasts?
- What else have you learned?
Follow on work
Building on the structures that students have seen, followon lessons could be developed to investigate:
• The function of guard cells
– experiments with long balloons and sellotape to show curving of the balloon
during inflation when one side has been taped
• The role of chloroplasts in photosynthesis
– why doesn’t onion epidermis have chloroplasts?
– why are they green? (pondweed stops photosynthesising in green light)
• The role of xylem
– why do xylem vessels need strengthening with lignin?
• The structure of leaves / leaf tissues
• The function of trichomes
– as a research / extension project