Transcript Plants & Civilization BIO 1785

TA Info
 Francis (Frank) Iosue
 [email protected]
 Office = 192 Mendel
 Monday 9-10 AM
 Tuesday 9-10 AM
 By Appointment
Attendance
 260 points (37%) of your grade for the course
will be based on lab
 Attendance is MANDATORY – NO Make-up
labs
 If you have a legitimate reason to miss lab,
contact me or Ms. Jamison Immediately
 2 Field Trips
Academic Integrity
 Policy set forth in the “Blue Book” will be strictly
enforced
 Unless specifically stated, all assignments are
to be done alone!
 If you are unsure, ASK ME!
Safety
 No food or drink
 Appropriate dress (no open-toe shoes, long
pants, no halter tops)
 NO CELL PHONES!!!
 Leave the lab clean
 Safety goggles and gloves when needed.
Plants & Civilization
BIO 1785
Lab #1:
The Microscope & Plant Cells
The Microscope…
A Review
Compound Light Microscope – useful for viewing
slides
vs.
Dissecting Microscope – useful for viewing 3-D
images.
ALWAYS HANDLE THESE EXPENSIVE PIECES OF
LAB EQUIPMENT WITH EXTREME CARE!
Compound Light Microscope
Identifying the parts of a microscope
Know where parts are
located & what each is
used for.
TA will demonstrate
proper use if you don’t
remember! Always ask
if unsure so that you do
not damage the scope!
Compound Light Microscope
Recall…
1. Total Magnification = objective lens (listed on
objective) x ocular lens (10x).
2. Field of View: what you see when you look
through the eyepiece.

How does this field change when switching to higher magnification?
3. Depth of Field: thickness of the object in
focus.

Are all layers of your specimen in focus at the same time? If not, what
does that indicate?
How to Make a WetMount Preparation
Solid Specimen
(e.g. potato)
 Drop of H2O onto slide
 Very thin slice of potato
onto drop
Liquid Specimen
(e.g. Oscillatoria)
 Use pipet to “mix up”
specimen, then draw up
 Place one drop of
specimen onto slide
TA will DEMONSTRATE Onion wet-mount….
FOCUSING
on your wet-mount
…“I can’t see anything on my slide!”
-first time scope user
1. First, fit slide securely into stage clip.
2. With scanning power objective lens (4x) in place, adjust the stage
upward using the coarse adjustment knob so that the lens is
almost touching the slide –DO NOT allow the lens to hit the slide &
DO NOT LOOK THROUGH THE EYEPIECE YET! (you should be
looking from the side)
3. Now, while looking through the eyepiece, use coarse focus knob
to “focus downward” on your specimen.
[Focusing “upward”, that is moving the stage upward toward the objective lens,
may result in breaking your slide & damaging the objective lens – never do this].
ALWAYS, ALWAYS, ALWAYS – FOCUS DOWNWARD!
Part II: PLANT CELLS
CELLS are the basic unit of life. All plants
are comprised of cells.
Prokaryotes vs. Eukaryotes
Prokaryotes: cells which do NOT contain a membrane-bound
nucleus or other organelles. Instead, prokaryotes have a plasma
membrane only.
Examples: bacteria & cyanobacteria.
PROKARYOTES
[The Cyanobacteria]
Largest prokaryotes = CYANOBACTERIA
[a.k.a. “blue-green algae”]
 Cyanobacteria contain chlorophyll a & other pigments
(phycobilins) needed for photosynthesis.
 Pigments are NOT contained in chloroplasts, but in
photosynthetic membranes called thylakoids.
 Perform photosynthesis similar to eukaryotic plants
 Important 10 producers (both on land in aquatic
ecosystems).
 Do they produce their own food???
YES!!
Examine Cyanobacteria
Prepare wet-mounts of & examine (sketch):
1. Oscillatoria – filamentous w/ rhythmic mov’t
2. Nostoc – filamentous w/ cell differentiation
(heterocysts)
3. Anabaena – filamentous w/ heterocysts
4. Gloeocapsa – heavy gelatinous sheath
holding uni-cells together
5. Cylindrospermum – filamentous with
heterocysts & akinetes
Cyanobacteria…
what can they do?
 Capable of photosyntheis - O2 evolving
 Heterocysts - N2 fixation (enriches
aquatic environments)
 Akinetes – provide survival support
Heterocyst
Akinete
Vegetative filament
http://www.dr-ralf-wagner.de/Bilder/Cylindrospermum.jpg
BACTERIA
 Are prokaryotes
 Not the same as cyanobacteria!
 How does the size of a bacterial cell
compare to that of cyanobacteria?
For answer: Compare your observations of
cyanobacteria to DEMOs of bacterial cells.
EURKARYOTES –
Plant Cells
 Eukaryotes: cells which do contain a membranebound nucleus & other organelles. The cytoplasm is
contained within the plasma membrane.
 Chloroplasts = green organelles which contain
chlorophyll. This is the site of photosynthesis in plant
cells.
 Another organelle = mitochondria where cellular
respiration occurs.
EukaryotesPlant Cells (con’d)
Structure of Plant Cells
Note:
cuboidal shape &
numerous
organelles
Specialized Plant
Cells & Tissues
Types by Function:
1. Support

Collenchyma, Sclerenchyma (includ. Sclerids)
2. Vascular

Xylem, Phloem
3. Storage, etc.

Parenchyma
4. Protection

Epidermis, Cork, Cork Cambium
Specialized Plant
Cells & Tissues
SUPPORT:
 Collenchyma cells– provide mechanical support w/
irregularly thickened cell walls esp. while cells are
growing.
 Thickened at corners; Cells just beneath epidermis; reddish in
color & appear ‘star or hexagon-shaped’ under scope.
 Sclerenchyma fibers– long & slender support occuring in
bundles w/ heavy 2o cell walls made of lignin.
 Strong polymer; rigid support; If cell dies lignin can still provide
support; also appears reddish in color.
 Sclerids: type of sclerenchyma cell variable in shape for strength
& rigidity, often branched & ‘gritty’ in appearance.




Provides heavy 2o cell wall support
Lignified (so it appears pink/reddish)
Connects two air spaces
Example: Stellate sclerid – named due to shape.
Examples of:
Support Cells & Tissues
Collenchyma
Sclerenchyma
Sclerids
http://www.rhodes.edu/biology/stinemetz/sclerid1.jpg
http://www.vet.purdue.edu/bms/intl/nourpix/an0020.jpg
http://www.sc.chula.ac.th/courseware/2303105/spec/03.JPG
http://www.nsci.plu.edu/~jmain/b359web/images/sclerid(2TN).jpg
Specialized Plant
Cells & Tissues
Vascular:
 Xylem cells- modified elongated cells that conduct
H2O by capillary action.
 Xylem vessel elements (1 cell) align end-to-end forming
xylem vessels.
 Lignified 2o walls, thickened in various patterns (e.g. annular,
reticulate, sclariform).
 Xylem rings are deposited yearly – used to age a tree!
 Phloem cells- modified cells for transport of
organic solutions.
 Consist of sieve tube members & companion cells.
 At maturity, differentiated for conducting materials, loses
nucleus, but remains fully functional.
Examples of:
Vascular Cells & Tissues
Xylem & Phloem, c.s.
A = Phloem
(green cells)
B= Xylem
(red cells)
http://www.life.uiuc.edu/ib/202/labs/structure/plant_transpiration/buttercup400x.jpg
Xylem: A Closer Look
Longitudinal sections: note patterns of
lignified cell walls
http://www.skidmore.edu/academics/biology/plant_bio/
Anatomy-stems,seeds,embryos/Xylem%20fibers%20&%20vessels%20l.s..jpg
http://www.rothamsted.bbsrc.ac.uk/notebook/courses/guide/images/xilem.jpg
Phloem: A Closer Look
Longitudinal section: showing
sieve tube members with “sievelike” end wall & associated
companion cells.
Cross section: showing green
phloem cells in a vascular bundle
w/ xylem.
http://www.bbc.co.uk/scotland/education/bitesize/standard/img/biology/structure_phloem.gif
http://botit.botany.wisc.edu/images/130/Stem/Zea_cross_section/Phloem.low.jpg
Specialized Plant
Cells & Tissues
Storage, etc.

Parenchyma cells – thin-walled living cells that are
most abundant cell type in plants.

Many kinds of parenchyma cells that perform diverse
functions including:
1. Photosynthesis (in leaves)
2. Intercellular communication
3. *Food (starch) storage (in roots & stem of plant)
Parenchyma Cells
Cross section: showing cellular inclusions.
What are these inclusions & what do they tell
you about the function of this type of
parenchyma???
Plant stem – parenchyma
cells make up the cortex
http://members.tripod.com/ashley_tan/histology/images/plant_histology-root_dicot_ts.jpg
http://members.tripod.com/ashley_tan/histology/images/plant_histology-basic_tissues_parenchyma_ts.jpg
Specialized Plant
Cells & Tissues
Protection:
 Epidermis – outermost layer of cells of leaf, stem, &
roots exposed to environmental stresses.
 Covered by cuticle (waxy layer)
-prevents H2O loss
 Where guard cells & subsidiary cells are found
around stomata openings.
-regulate CO2 in & O2 out of plant cells
 Periderm – consists of Cork & Cork Cambium which
replaces epidermal tissue that is worn away by
environmetal wear & developmental/mechanical
stresses.
Epidermis
http://images.botany.org/set-13/13-021v.jpg
Outermost layer of
cells = epidermis
Guard cells surrounding stomata
opening (within epidermal layer)
Trichomes =
extensions
of epidermis
http://www.emc.maricopa.edu/faculty/farabee/BIOBK/92462b.jpg
http://bugs.bio.usyd.edu.au/2003A+Pmodules/graphics/A62a.jpeg
Cork & Cork Cambium
Found in roots &
stems.
http://www.botany.hawaii.edu/faculty/webb/BOT201/PrimSec/Peri-2240Lab.jpg
•
Cork cambium cells undergo active mitotic division, then migrate to the
outside to form cork.
•
Cork cells form waxy material called suberin which provides protection,
but seals cork off from other cells of the plant. Cork cells are still
functional even when dead.
TODAY’S PLAN:
Summary
Part I - Microscope
Refresher Course
Part II – Specialized Plant
Cells & Tissues
Lab Manual pp. 1-20

Label parts of microscope &
recall proper usage (proper
focusing technique, field of
view, depth of view,
magnification).
Lab Manual pp. 21-42

 Cyanobacteia wet-mounts &
sketches (label diagrams!)
 Bacteria types DEMO slide


vs.
Eukaryotes
 Plant cell general structure
 Elodea wet-mount
Making wet-mounts of potato,
onion…for practice.
 Study wet-mounts of
cyanobacteria in part 2.
Prokaryotes

Specialized Cells & Tissues
 Support, Vascular, Storage &
Protective types
 View various slides of each,
sketch, & label.