|MICROSCOPY / SIZE / FOCUS|
|Microscopy||Cell Size||Preparing microscope slides Onion and cheek|
|Stage Micrometer||Metric Measurements||Silk Thread Slide - Depth of Focus|
|Cells Biology - Introduction to Microscopy||Virtual Microcope - Flash|
|Cork image of Hook 1665||Robert Hooke||Cork tree to bottle|
|Onion - bulb showing leaves and scales||Onion - Scanning power Onion -||Onion Low power|
|Onion High power Onion - high power||Onion - stained||Onion High Power - stained|
|Onion - cytoplasm and cell wall||Onion - nucleus + nucleolus|
|Elodea -||Elodea - the plant||Elodea - high magnification|
|Elodea - chloroplast||Elodea - vacuole located||Elodea - cell wall|
|Elodea - high magnification||Elodea - plasmolysed||Elodea Cytoplasmic Streaming (large file - video)|
|Elodea - Elodea - thumbnails||Links to Elodea movies, etc.|
|Physarum - An introduction||Physarum On Oatmeal||Images of Physarum|
|Plasmodial strands - link||Physarum Sporangia - EM||Physarum - Sporangium|
|Slime molds -|
|Amyloplasts||Starch Grains bean embryo||Starch Grains in chloroplasts|
|Starch - potato||Starch
grains Google search engine
|Starch - potato e.m.|
|druses -||Raphides||cystolith - with label|
|*The plant cell|
|The Plant cell - electron micrographs||Cells and organelles -||Electron Micrographs - Plants|
|EM - plant cell near end|
I selected links with images and information related closely to the observations described in lab Exercise 2 (Plant Cells) of your botany lab manual. Preview these resources as you prepare for the laboratory exercise and review these resources as you write your lab reports and study for tests. The emphasis of today's laboratory is microscopic technique and critical observations of plant cells. In addition to proper microscopic techniques, I am interested in your mastering the concepts of magnification, cell and organelle size, and recognizing differences between what can be seen with the the light and electron microscopes.
The keys to success in this exercise are to be prepared, and to follow instructions. Read the exercise in advance. Examine the illustrations in the links so you will know what the cells and their organelles look like when viewed properly.
Remember to bring your culture of Physarum !
I. THE COMPOUND MICROSCOPE
Microscopy -- this link leads to a variety of background sites dealing with microscopy Cell Size -- this link leads to the Bio. 1000 web site and contains a calculator and general information about expected measurements of plant and animal cells Silk Thread Slide - Depth of Focus - explanation of the focusing procedure, see lab manual for details Stage Micrometer - explanation of the measurement procedure, see lab manual for details
II. THE DISSECTING MICROSCOPE
I did not provide any links. See lab manual for details and illustrations. I will be happy to work with you individually in lab
III. MICROSCOPIC OBSERVATIONS
A. Silk Thread
B. Cork Cells-- links lead both to Robert Hooke and his observations of cork and to a discussion of the process by which cork is obtained from oak bark
C. Onion Bulb Epidermal Cells-- links to onion epidermal cells viewed at various magnifications
D. Elodea Leaf Epidermal Cells- - links lead both to macroscopic illustrations of this water plant and to a variety of microscopic images of Elodea in which the organelles are shown and identified
E. Cytoplasmic Streaming-- students usually observe streaming both in onion and Elodea. The movement in Elodea is often quite dramatic. One link leads to a video (large file) that you can view if you have time and the proper resources on your computer Physarum - cytoplasmic streaming -- this organism and its pulsing, reversing protoplasm are quite unique. Links lead to a number of views of Physarum.
F. Potato Parenchyma Starch Granules- links illustrate potato starch at various magnifications
G. Crystals in Zebrina Stem Cells- links illustrate Raphides
H. Enhancing Observations of Cells- I did not include any specific links to the procedures (stains, etc.) described in the lab manual. You may locate some information by following microscopy links.
Electron Micrographs- Electron micrographs are on display in this lab. Links lead to sites with transmission and scanning electron micrographs of plant cells.
Stage MicrometerThe stage micrometer slides are prepared slides that contain a tiny ruler beneath the coverglass. The rulers on these particular slides are two millimeters long and subdivided into smaller increments. The increments are marked at lines corresponding to 0, .5, 1 , 1.5 and 2 mm. Place the stage micrometer slide on the stage of your microscope and locate and focus on the ruler as directed in the lab manual. Measure, or estimate as accurately as possible, the distance across the diameter of the field of view. Record the value to the nearest tenth of a millimeter for scanning, low, high and oil immersion lenses.
Convert these measurements to micrometers and record the converted values in your laboratory manual.
Assume that a meter repeatedly is divided into smaller units, and that each time the units are one tenth as large as before.
How Divided unit symbol Initial Size = one meter meter m Divided into 10 pieces decimeter Divided into 100 pieces centimeter cm Divided into 1,000 pieces millimeter mm Divided into 10,000 pieces Divided into 100,000 pieces Divided into 1,000,000 pieces micrometer um Divided into 10,000,000 pieces Divided into 100,000,000 pieces Divided into 1,000,000,000 pieces nanometer nm Divided into 10,000,000,000 pieces Angstrom oA
The silk thread slides are intended to allow you to practice focusing with the microscope. Each slide contains three silk thread, one placed on top of the other, between the glass slide and the coverslip. One silk thread is colored red, a second is colored yellow, and the third is colored green (or blue). Observe the threads at low power (100X) at a region where the threads overlap.
Silk Thread Slide - Depth of Focus
While watching from the side, turn the coarse adjustment knob to lower the objective lens as far as it will go. When the objective lens is this close to the slide, none of the threads will be in focus because the depth of focus of the microscope is quite shallow.
Now, look into the eyepiece of the microscope, and very slowly turn the adjustment knob to raise the objective lens away from the slide. The first silk thread to come into focus is the one on the bottom. Continue slowly to raise the objective lens away from the slide. The second silk thread to come into focus is the thread in the middle, and the last silk thread to come into focus is the thread on top, nearest the coverglass.
Don't be mislead by the intensity of the color (one color may be faint and another very dark). Instead observe the ultrastructure of the threads. Each is composed of very fine linear strands and these can be resolved fairly easily, but only when t he thread is in sharp focus.
Now that you have mastered the skill of focusing at different depths, be sure that you use this almost continually as you examine the organelles within cells, and layers of cells within a tissue.