Plants Lab
Spring 2013

Radish Root Hairs

Question
• Newly-formed cells soon will differentiate into
different types of cells and form tissues. Plant
regions having undifferentiated cells are
known as meristems. We find meristematic
tissues at root tips.
• Where else in a plant should you expect to
find meristems?

Leaves

Dermal Tissue

Plant Crystals: Raphides

Plant Crystals: Druses

Question
• Crystals in different plants occur as raphides
(sharp needles), druses (star shaped) and
other forms. Most are composed of calcium
oxalate.
• How might a plant benefit from having
needles or other crystals in its leaves?

Lower Epidermis

Question
• Another way plants protect themselves
against excessive water loss is by secreting a
waxy sort of substance to form a cuticle on
the surface of a leaf. The cuticle is quite
apparent in some leaf peels and cross sections
• In which types of habitats do you think
you’re most likely to find plants with
significant cuticles?

Ranunculus Cross section

Xylem and Phloem

Plasmolysis
• Elodea leaves again!!
• This time concentrate on
chloroplast
• Work in partners
– One scope has water the
other has salt water
– Use the wet slide mount
technique
– Wait 15 minutes for salt
water drawing
• While we wait lets move to
photosynthesis and respiration

Photosynthesis and Respiration
• Recall from Window into a cell
• Plants contain chloroplasts and
mitochondria
• While the chloroplasts are active
during the day they are creating
sugars in the form of glucose
• When the mitochondria are
active they use the glucose
(sugar) to produce energy in the
form of ATP

Question
• Most living things require oxygen.
– How can we breathe during the winter months in
temperate zones? How do polar organisms
manage?
• Some people enjoy plants in a closed/sealed
container called a terrarium.
– How can the plants thrive with no access to the
outside air?

Plasmolysis
Before adding salt After adding salt

Why does this Happen? Osmosis
• Osmosis example animation:
– http://www.stolaf.edu/people/giannini/flashanim
at/transport/osmosis.swf
– In addition to the molecules and other structures,
cells contain lots of water. Water is made of two
hydrogen's and one oxygen molecule
– Molecules are in constant motion. Molecules that
are crowded into one area (higher concentration)
will Spread out into an area of lower
concentration

Elodea Osmosis Explanation
• Plant cell in water:
– Water molecules Enter the cell
because the environment has
higher concentration of water
– Result = cell membrane is
pushed outward by higher water
pressure, giving the appearance
to be spread out
• Plant cell in salt water:
– Water molecules Leave the cell
to the environment because it
has a lower concentration due
to the salt
– Result = cell membrane lacks
water pressure and it appears to
shrivel up

Starch and Plastids
• Crackers
• in finger bowl
– What color are the following items when Iodine is
applied (iodine reacts with starch it turns blue-
black)
• Potato
• Been
• Cornstarch
• sugar

Starch and Plastids
• Plastids are cells that store specific things
– Chloroplasts is a plastid that stores chlorophyll
– Amyloplasts are specific plastid and it stores
starch grains

Amyloplasts

Reminders
• Lecture:
– Lecture Exam #1 Tuesday
• Lab:
– Quiz 5 – Take home quiz