a living flower of some kind/group. Almost any type of flower will work, however, you should avoid composite flowers (like dandelions, sunflowers, black-eyed susans, etc.). Composite flowers look like a single flower, but are actually a composite of many small flowers stuck together (each small flower has its own reproductive parts, which are smaller and difficult for students to see). We do this lab in the spring here in Missouri and use daffodil flowers.
1 dissecting needle/group
1 pair of dissecting scissors/group 1 pair of forceps/group
1 scalpel/group
1 stereomicroscope (dissecting microscope)/group – to view plant parts 1 microscope slide and cover slip/group – to place pollen on
1 beaker of water with dropper pipette in the front of the class – access to water to make pollen wet mount slide
1 compound microscope/group – to view pollen collected from the flower PART 2 and PART 3 – OBSERVING POLLEN FROM DIFFERENT PLANTS
1 set of “Pollen Reference Photographs – Pollen From Various Plants”/group – these pollen reference photographs are provided in the book and on the CD that comes with this book. There are photographs of eight different types of pollen. You can prepare black and white copies of the Reference Photographs for students to use (the pollen don’t have any specific colors for students to observe) OR print off color pages of the pollen photographs (the color Pollen Reference Photographs can be found on the CD that comes with this book – found in the file named “Pollen Training Lab Reference Photographs”. Place the Pollen Reference Photographs in clear, page protectors and you can use them for many years!
1 or 2 microscope slides/group – to collect pollen from outside
jar of Vaseline or similar petroleum jelly – students will use this to coat one side of their microscope slide and collect wind-blown pollen outside
location to place “pollen catching slides” outside where they can remain undisturbed for
24 hours
1 small container and dropper pipette to hold the Pollen Stain (placed in the front of the room
1 or 2 cover slips/group – to place on pollen slides before viewing 1 compound microscope/group – to view pollen slides
SAMPLE PAGES
Solutions To Prepare:
Pollen Stain – add together: 15ml distilled water + 10ml of 95% Ethanol + 5ml glycerin + 6 drops of 1% Safranin stain (Safranin and Safranin O are the same thing).
This amount should easily last through your day (students only need a 1-2 drops each). This preparation will stain the pollen a light pink color. If you want the pollen to stain a darker color simply add 1 or more extra drops of Safranin to the Pollen Stain
mixture.
Comments/Problems:
This Training Lab usually takes 3 days to complete. Typical Schedule: Day 1 – complete Part 1 (dissect flower) and begin Part 2 (place slides outside to collect pollen).
Day 2 – Part 2 (observe Pollen Reference Photographs and observe pollen collected outside on slides). Day 3 – Complete Questions
Schedule Option – students sometimes don’t have enough time to finish looking at their pollen collection slide on Day 2 – and it usually isn’t satisfactory to save this stained slide overnight to finish looking at it on Day 3 (the stain dries out). Simply have each group make TWO pollen-catching slides to place outside on Day 1. They can stain one slide on Day 2 and observe until they run out of time. They can then stain and look at the second slide on Day 3 to finish their observations before beginning their questions (unstained slides can be kept for days).
Try to coincide this lab with a time of the year when you know there are many plants flowering in your area (to catch the most pollen) – usually in the spring, although you can catch pollen in the fall as well.
Check to make sure it is not going to rain the night you plan on placing the pollen slides outside. Rain usually removes the petroleum jelly from slides and ruins the experiment. It takes time for students to take their slides outside, find a place to put them, then go back outside the next day to retrieve them. Here are some options for placing the pollen
collection slides outside that can save you time!
1. have students tape their slides to a windowsill outside your windows for 24 hours.
2. have students take slides home with them, place them somewhere around their house for 24 hours, then bring them back to the classroom for observation.
3. have students prepare the slides with petroleum jelly and place all the slides on a
cafeteria tray (or similar) to make them easy to carry. Then YOU take the trays of slides outside and bring them back inside 24 hours later (you could even take them home with you).
4. Here’s what we do. We place the slides outside (on trays) for 24 hours, then before carrying them in we walk by some of the different flowering trees on campus and shake the limbs over the trays. This makes sure there is plenty of pollen on the slides for students to observe!
SAMPLE PAGES
Students will probably not be able to identify many of the wind blown pollen grains they collect on their slides (unless they are similar to the pollen found on the Pollen Reference Photographs). You could give time for students to complete an Internet search to see if they can identify some of the different pollen they collect. It’s easiest if they search for the pollen of plants you know might be blooming in your area – then look to see if any of their collected pollen matches.
Some of the pollen grains collected on the petroleum jelly may actually begin to grow pollen tubes (these are the tubes that grow down to the ovary and fertilize the eggs). Leave the Pollen Reference Photographs out and available for students to use throughout this Training Lab (students may want to use the photographs to help them identify pollen they collect from outside, and help them answer Training Lab Questions).
Students will be required to use their Pollen Sketches they made in Table 2 (sketches of the eight different pollen grains found in the Pollen Reference Photographs) during the Job that immediately follows this Training Lab. Let students know they should be prepared to use their pollen sketches to identify pollen evidence collected at a crime scene – and will NOT be allowed to use the Pollen Reference Photographs during this upcoming Job without paying a fee! See the Job that follows for details.
A great optional activity, if you have a microscope camera, would be to have students collect pollen from known flowers in your area and photograph the magnified pollen for a reference collection (include a photo of the plant and flower as well). This reference collection might even be useful to your local crime lab!
Typical Results:
A key to Table 2 can be found immediately following these Teacher Notes. Table 1 results will vary depending on the flower your students dissect, and Table 3 results will vary depending on the wind blown pollen your students collect from outside.
SAMPLE PAGES
Plant Name Relative Size Of Pollen Shape Of Pollen Outer Covering Characteristics When Is Pollen Released? Sketch Of Pollen (viewed with High
Power) Crocus Dafodill Cherry Apple White Oak Pine Daylilly Ragweed
Table 2 – Characteristics of pollen from Pollen Reference Photographs
LARGE MEDIUM MEDIUM MEDIUM MEDIUM ROUND OVAL ROUND SMOOTH BUMPY WITH GROOVES SMOOTH MARCH/ APRIL TRIANGULAR ROUND OTHER – ROUND WITH “EARS” SMOOTH or PORES PRESENT PORES PRESENT BLADDERS
PRESENT SUMMER SPRING/
MEDIUM - LARGE SMALL OVAL PATTERNED SPIKES PRESENT ROUND MAY- SEPTEMBER AUGUST/ SEPTEMBER MEDIUM - LARGE MARCH/ APRIL APRIL/ MAY APRIL/ MAY APRIL/ MAY
KEY
SAMPLE PAGES
QUESTIONS – PLANT POLLEN AS EVIDENCE
NAME________________________________ 1. Neatly label the flower drawing below. Include the following structures: CALYX, SEPAL, COROLLA, PETAL, STAMEN, ANTHER, FILAMENT, PISTIL, STIGMA, STYLE, OVARY, LOCULE, OVULE.
2. What part of a flower releases the pollen? _________________________ 3. Why is plant pollen so common in the air?
4. How could you easily tell if you rubbed against a flower and got pollen on your clothing?
5. Explain how pollen can help determine WHEN a crime occurred.