Question Prompts:
What microscopic structures inside flowers support plant reproduction, and how do they function?
What microscopic interactions between flowers and pollinators help make plant reproduction possible?
Whether you choose to address these prompts or create your own questions, you and your students can discover the answers with a classroom set of Foldscopes.
Figure 1. Montage of flowers and pollinators
(Photo Credit: Holly A. Stuart)
Background:
Summertime is when flowers are in full bloom. While some flower parts are macroscopic, there are many ways that a microscope can help you to learn more about the invisible side of plant reproduction. Here is a list of macroscopic and microscopic descriptions of flower parts, sample and slide preparation techniques, and student research ideas to get you started!
Materials:
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Dissecting Kit or Set of Tweezers
Figure 2. Montage of flower parts viewed under a Foldscope 2.0
(Photo Credit: Holly A. Stuart)
Petals
Beyond the obvious macroscopic properties of flower petals like color, shape, and scent - which attract various pollinators - there are also microscopic structures at play. The shape of the cells on flower petals is thought by researchers to aid insects in gripping the surface as they move. For further details, read the Foldscope Explores blog post titled "Shape Shifting Flower Petal Cells."
Figure 3. Flower petals viewed under a Foldscope 2.0 at 140X magnification plus 5X digital zoom on phone
(Photo Credit: Holly A. Stuart)
To view a flower petal with a Foldscope, sandwich the petal between two clear stickers on a blank trading card or place the petal on a glass slide.
Figure 4. Flower petal mounted on a blank trading card
(Photo Credit: Holly A. Stuart)
Students can expand their understanding of life's fundamental building blocks by undertaking a scientific study that compiles data on the shape, size, and color of flower cells. Encourage your students to generate graphical representations of their data to tell the unseen story of floral diversity at a cellular level.
Stigma, Ovary, and Ovules
The female parts of a flower are the stigma, ovary, and ovules. The stigma sits at the top of a tube called the style. When pollen grains, the male cells that fertilize the ovules, land on the stigma, they travel down the style to the ovary which holds the ovules. When an ovule is fertilized by pollen it becomes a seed. Stigmas, styles, and ovaries are large enough to be seen with your eyes, but the microscopic “fingers” on the surface of the stigma and the ovules tucked in the ovary require a microscope for observation.
Figure 5. Tip of a stigma (140X magnification plus 5X digital zoom on phone - left) and ovules (50X magnification with reflective lighting - right) viewed under a Foldscope 2.0
(Photo Credit: Holly A. Stuart)
To mount the stigma onto a slide, grasp it with tweezers, remove it from the flower, and place it directly on a slide.
Figure 6. Stigma being removed from the flower with tweezers (left) and the stigma mounted on a glass slide with a glass cover slip (right)
(Photo Credit: Holly A. Stuart)
The ovary and ovules are at the base of the style. You can use a scalpel or razor to cut a very thin slice and place it on a slide.
Figure 7. Ovary being sliced with a scalpel to obtain the ovules
(Photo Credit: Holly A. Stuart)
Not all flowers have a stigma, and those that do can have one or multiple stigmas. Students can look for patterns in the shape, size, and number of stigmas and ovules of flowers in the garden. Have your class reflect on the biological advantages these differences might offer the plants. Students should take into account the entire ecosystem and habitat of the plants as they reflect on the cause and effect of flower structures and survival.
Anther & Pollen
The anther is the part of the flower that produces the male reproductive cells called pollen. The anther sits on top of stalks called filaments. Both the anther and pollen are visible without the aid of a microscope, but the pollen usually just looks like powder. However, when pollen is viewed under a microscope you can see that it actually comes in a variety of sizes, shapes, colors, and textures.
Figure 8. Anther with pollen spilling out (140X magnification with darkfield lighting - left) and pollen grains (340X magnification plus 5X digital zoom with reflective lighting - right) viewed under a Foldscope 2.0
(Photo Credit: Holly A. Stuart)
Anthers can be mounted in the same manner as a stigma. Use tweezers to pull them off of the flower and place them directly on a slide.
Figure 9. Anther being removed from the flower with tweezers (left) and the anther mounted on a glass slide with clear tape (right)
(Photo Credit: Holly A. Stuart)
Pollen can be collected by touching the sticky side of a piece of tape to the anther and then placing the tape on a slide.
Figure 10. Using clear tape to collect pollen (left), pollen stuck to the clear tape (middle), pollen and tape mounted on a glass slide (right)
(Photo Credit: Holly A. Stuart)
To the naked eye, pollen may look like a powder showing no differences from flower to flower other than the color, but a microscope reveals a world of wonder and diversity! Student investigations into the variety of shapes, sizes, colors, and textures of pollen grains can give them a better understanding as to just how different and beautiful pollen can be. Have your class design scaled up models of the pollen that they find in the garden to help them relate to what insect pollinators might encounter when visiting that flower.
Pollinators
While wind, rain, and gravity all have their roles in pollination, insects and other animals also play a large part in spreading pollen from plant to plant. Insects are attracted to flowers because of their colors, shapes, scents, and the promise of pollen and nectar. Most insects are covered with hairs that can best be seen with a microscope. Pollen gets trapped in these hairs and as the insects go from flower to flower, they are pollinating the plants by spreading the pollen.
Figure 11. Fly in the garden (left) and fly wing (140X magnification plus 5X digital zoom on phone - right) viewed under a Foldscope 2.0
(Photo Credit: Holly A. Stuart)
To find pollinators to observe, search the ground for dead insects and use tweezers to pick them up, separate the wings, legs, and antennae, and mount the insect parts on slides.
Figure 12. Insect wings mounted on glass slides
(Photo Credit: Holly A. Stuart)
Students can study the relationship between microscopic structures on insects and the pollen they collect by searching for pollen grains on the insects. Let students observe and record which pollinators are visiting each flower in the garden. Can they find evidence of these visitations on the insect parts being studied under the microscope?
Connect:
Remember, these are only suggestions to guide you along your garden study. What questions do your students want to answer? What flowers are blooming in your garden now? And which pollinators are visiting your flowers? Let us know! Share your observations, discoveries, and pictures with the Foldscope community on the Microcosmos. Your contributions will build up a strong scientific database that can help support new and innovative scientific research. Tag us on social media, too. We love to see how Foldscopers around the world are using their Foldscopes in new and innovative ways!
Next month we’ll look at fruits in the garden. Until then, happy gardening and Foldscoping!
Figure 13. Fruits growing in my garden!
(Photo Credit: Holly A. Stuart)
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