Lesson Plan - Get It!
How does the smell of a flower help a plant reproduce? Does it wear special perfume to attract a mate?
Spring is usually marked by blooming flowers, but flowers are a lot more than just a beautiful part of a plant.
They are the reproductive system of angiosperms. We learned in a previous Plants lesson that vascular plants are organized based on how they reproduce. If you missed or need to review the previous series lessons, find them in the right-hand sidebar under Related Lessons.
Now, we will take a more in-depth view of plant reproduction. If you remember, there were three modes of reproduction: spores, cones, and flowers.
Spores are released by plants like ferns. These are very small structures that are capable of growing into a new organism on their own. This is the simplest form of reproduction in plants.
Spores allow for wide distribution of offspring, but they do not increase genetic diversity for a species. Genetic diversity is all of the genetic make-up in a species. Species with high genetic diversity are able to survive disease and changes in the environment, while species with low genetic diversity can be vulnerable to damage and death.
If a plant does not use spores, it will use seeds to develop offspring. Seeds are a product of sexual reproduction in plants, and provide necessary nutrients to developing plants.
Sexual reproduction helps provide genetic diversity for species. Both gymnosperms — plants with cones — and angiosperms — plants with flowers — carry out sexual reproduction, but angiosperms use flowers to hold developing seeds. Pollen is the "male" cell that fertilizes a plant's egg cell.
In a gymnosperm, pollen reaches the egg when wind blows the pollen onto a female cone. Female cones hold eggs, but do not store them inside like a flower; therefore, pollen can easily meet an egg cell. Once the pollen and egg are united, fertilization occurs and a seed develops in the cone. These cones provide minimal protection to the developing plant seeds.
Angiosperms have flowers that are able to better protect the developing seed. Flowers have several important parts:
You will learn more about flower components in the Got It? section, where you will complete a virtual flower dissection! For now, just focus on what drives the actual creation of a new plant: pollination.
Pollination occurs when pollen is transferred from the male anther to the female stigma. This can happen through self-pollination, where the plant pollinates itself, or through cross-pollination, where other flowers pollinate the stigma. Cross-pollination is the process aided by insects like bees and butterflies, and animals like hummingbirds.
Once the pollination occurs, a tube starts to grow down into the flower. This tube allows the pollen to reach the egg cell, leading to fertilization. Pollination must occur before fertilization can occur! A zygote forms that will eventually develop into a whole new plant. This zygote will be the developing plant found within a seed. Seeds are an important part of plants, because they protect and support plants as they develop from fertilization into a new plant. Seeds have a seed coat that protects the inside of the seed from damage. Inside the seed, there is a large store of food and nutrients for the developing plant.
Plants use a wide variety of reproductive strategies to continue producing plants, ranging from simple spores to complex flower interactions. Plant reproduction happens throughout the year, so pay attention the next time you are walking outside.
- Do you see pollen and flowers ready for seed development?
- What questions do you still have about plant reproduction?
Discuss what you have learned with a parent or teacher before moving on.
In the Got It? section, you will learn more about flowers and the role they play in reproduction.