Rather than having a lesson today, I thought we’d have a short intermission and take a look at a book (written at the adult level) about seeds that came out recently . Seeing Seeds: A Journey into the World of Seedheads, Pods, and Fruit by Teri Dunn Chace and Robert Llewellyn could be used as a coffee table book due to the superb illustrations, but the informative text makes it something much more.
The first thing you will notice about this book are the illustrations. Robert Llewellyn uses a relatively new technique called “image stacking,” which involves take multiple images at different levels and then melding them together using computer software to create a crisply-focused, almost three dimensional image. When you first pick up the book, you will be mesmerized by these images, which grace every page (Timber Press shows previews on its website.)
What is even more thrilling about this book, however, was the quality botanical information. For example, the spread on spider flower reveals that what look like seed pods are actually called “siliques.” Because members of the Brassicaceae have similar structures, the plants were originally assigned to that family. Looking a DNA, however, botanists have now moved these plants to their own family, the Cleomaceae. Fascinating!
If you are a regular reader of this blog, you know we’ve been featuring mystery seeds and Seed of the Week for several years. Seeing Seeds is a wonderful resource to expand and continue studies on seeds and seed pods.
Disclosure: This book is my own copy. I am an affiliate with Amazon so I can provide you with cover images and links to more information about books and products. As you probably are aware, if you click through the highlighted title or image link and purchase a product, I will receive a very small commission, at no extra cost to you. Any proceeds help defray the costs of hosting and maintaining this website.
As we embark on a grand adventure into plant science, let’s start by thinking about what we mean by the term “plant” (links go to prior posts here at Growing With Science or to Wikimedia, as indicated).
Scientists currently group living organisms into three domains: the Bacteria, the Archaea and the Eukarya. Within the Eukarya are four divisions known as kingdoms. They are the Protista, Fungi, Animalia and Plantae.
So, basically we are asking what criteria scientists use to classify a given kind of living thing as belonging to the Kingdom Plantae.
Activity: Brainstorm about Plants (Prior Knowledge)
When you think of plants, what features or traits come to mind? Leaves? Flowers? Things that are green? Things that don’t move around? On a board or sheet of paper, brainstorm all the qualities of plants you know.
Now let’s take a look at what features that separate plants from other kinds of living things.
1. Do plants all have leaves?
Not all plants have leaves. Some types of plants, like these cacti, don’t have obvious leaves (although the spines are actually modified leaves). Parasitic plants also lack obvious leaves (see dodder below.)
Although most plants are green because of chemicals called chlorophyll, there are also plants that are red like the Japanese maple tree in the photograph above or these pitcher plants.The red pigments in the leaves are called carotenoids. Carotenoids also give fall leaves their color when the predominant cholorophyll pigments are lost.
Plants may also be golden yellow, or have white and green patterns.
4. Do plants make their own food?
One important aspect of plants is that they can make their own food via a process known as photosynthesis.
This is not an exclusive characteristic, however. There are some other organisms – particularly protists- that can also do this, and a few parasitic plants obtain their food entirely from other plants without making any themselves.
The yellow strands in the photograph are from a parasitic plant named dodder (public domain image retrieved from Wikimedia). The green leaves are from the host plant.
Along with making their own food, plants also store the excess food as starch.
5. Can plants move?
Seeds can move, passively for the most part (which we will learn about in an upcoming post), but once the plant has set down roots it is no longer capable of movement. Plants lack the ability to move about via contracting fibers like animals can.
6. So, if something can’t move, is it a plant?
Fungi were once lumped with plants because they can’t move on their own either. Now scientists consider fungi to belong their own kingdom because they have many important differences from plants.
7. Do plants live in the water?
With a few exceptions, plants live on land. That means they have special structures to keep from drying out that organisms living in the water wouldn’t need. For example, seeds have a tough outer seed coat to protect them from the relatively harsh environment of dry land.
Some plants like cattails and water lilies appear to live in water, but most of their structures are actually above the water.
What about organisms that live underwater, like kelp? Although kelp may look like a plant, it is actually a form of algae. According to current classification schemes, algae are not plants.
7. What differences are there inside plants? What about the cells?
If you could look at plant cells under the microscope, you could find two other features of plants. One is that plants are multicellular, which means they have many cells, not just one. That is a feature of the Domain Eukarya.
Secondly, plants have a cell wall around the outside of the cell, which is made up of cellulose (public domain image from Wikimedia).
Finally, with more advanced study, scientists have determined that plants have what is called an alternation of generations during the life cycle. We’ll learn more about that later.
In summary, plants
have cells surrounded with cell walls made of cellulose
live mostly on the land
make their own food via photosynthesis
store their excess food as starch
lack the ability to move
have alternation of generations during their life cycle
Activity 2. Which Are Plants Quiz
Now that you are an expert on the characteristics of plants, pick out the organisms below that are plants.
A. Is this a plant?
B. Is this a plant, yes or no?
C. Are these plants?
D. Are the things growing on the rock below considered to be plants?
Building and maintaining a terrarium or an “ecosystem under glass” can be a fun science project.
I. Choose the habitat you would like to study.
Do you want a natural terrarium? A traditional deciduous hardwood forest terrarium might include mosses, ferns and woodland plants. Other terrarium ideas are tropical rain forest, desert or boggy/swampy with carnivorous plants. Research the soil types, plant species you will need, amount of water to provide and what type of sunlight the plants will need. For example, a terrarium that represents the rain forest floor will need a lot less sunlight than one that represents the upper canopy.
Younger children may enjoy a less complicated project, such as simply a few dandelions and some grass from the yard.
1. Clear container of plastic or glass
a. Examples: a food container, such as a large plastic bin that prepared lettuce comes in, a plastic pet habitat, or an aquarium
b. Tops are optional, but helpful. You will need plastic wrap if you don’t have a top.
3. Soil, selected to match habitat
4. Plants – either native or houseplants that are small enough to fit your habitat
5. Items to add visual interest, such as twigs, rocks, seashells…
6. Gardening trowel or old spoon (digging implement)
III. Basic instructions
1. Layer the pebbles in the bottom of the container, roughly one inch deep.
This is a garage sale aquarium.
2. Add soil until the container is roughly one third full. Create dips, mounds and valleys to add visual interest.
3. Decide on which side of the container will be the front. Plant the taller plants towards the back, smaller, low growing plants towards the front.
4. Water thoroughly, taking into consideration the type of habitat you have prepared.
5. Cover the terrarium. Use plastic wrap and a string or large rubber band to hold it on if you don’t have a cover.
Watch as condensation forms on the sides of the container during certain times of the day. You can even see droplets form on the top and “rain” down. A terrarium can be used to study the water cycle.
Once your plants are established, you may consider adding soil creatures. The soil creatures can add an element of interest, but also require more care. Also keep in mind that many soil creatures are active at night.
If you try earthworms, make sure you have the right kind of earthworm. The red wigglers used in worm bins live in leaf litter at the surface of the soil in nature. They do better in bin than a terrarium unless you provide leaves for them.
Slugs and snails eat plants. They will both require extra food, such as vegetable scraps, and snails need a calcium source like a clean eggshell. Rolypolies or sow bugs do well in a terrarium, but also need added food. Carrots are good for rolypolies. If you add creatures, be sure to keep the terrarium clean. Vegetables can harbor small mites and/or springtails as well as become moldy.
A well-maintained terrarium may be an interesting science project. Study how fast the plants grow and which types survive best under the conditions provided. If you can keep the mosses happy, you will be able to see the different reproductive structures such as the sporangium and gametophyte. Mosses are non-vascular plants so they must absorb water directly from the soil. They do not have true roots or leaves. Spend time observing different types of mosses and learning about them.
Carnivorous plants require very special care but are also fascinating.
These are pitcher plants. Insects fall into the “pitcher” and can’t crawl out again.