Self-pollination facts for kids
Self-pollination is a special way plants make seeds. It happens when a plant's own pollen lands on the part of its flower that receives pollen, called the stigma. Think of it like a plant fertilizing itself! This is different from cross-pollination, where pollen travels from one plant to a different plant.
There are two main types of self-pollination:
- Autogamy: This is when pollen moves from the male part (anther) to the female part (stigma) within the same flower.
- Geitonogamy: This happens when pollen moves from one flower to another flower on the same plant.
Some plants have clever ways to make sure self-pollination happens. For example, some flowers do not fully open, keeping their pollen inside to reach the stigma.
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How Plants Self-Pollinate
Many plants use self-pollination. This often happens in plants with small, less colorful flowers. These flowers might drop their pollen directly onto their own stigma. Sometimes this even happens before the flower bud fully opens!
Plants that self-pollinate do not need to spend a lot of energy making bright colors, sweet smells, or nectar. These features usually attract insects or other animals. This is a big advantage in places where pollinators like bees or butterflies are rare. Such places include very cold regions or high mountains.
Why Plants Self-Pollinate
Self-pollination offers several benefits for plants:
- Reliable Reproduction: Plants do not have to rely on wind or animals to carry pollen. This means they can still make seeds even if pollinators are scarce.
- Stable Traits: If a plant has traits that help it survive well in its environment, self-pollination helps keep those traits strong in future generations.
- Less Pollen Waste: Since pollen does not travel far, less of it is lost during the process.
- Purity of Features: The unique characteristics of a plant species can be maintained over time. This is because the plant is essentially making copies of itself.
Challenges of Self-Pollination
While self-pollination has advantages, it also has some downsides:
- Less Variety: When a plant self-pollinates, its offspring are very similar to the parent. This means there is less genetic variety. This can make it harder for the plant species to adapt to new diseases or changes in the environment.
- Reduced Strength: Over many generations, a lack of new genetic material can sometimes lead to plants that are less strong or healthy. This is why many plants that can self-pollinate also have ways to encourage cross-pollination as a backup.
Plants That Self-Pollinate
Many different plants can self-pollinate. Some common examples include:
- Peanuts and Soybeans: These legumes often self-pollinate. Soybean flowers can even self-pollinate as they close if insects have not cross-pollinated them during the day.
- Orchids: Many types of orchids, like the Ophrys apifera shown in the image, use self-pollination.
- Peas and Sunflowers: These familiar plants also have the ability to self-pollinate.
- Dandelions: These common flowers are capable of self-pollination, but they can also cross-pollinate.
Mixed Mating Systems
About 42% of flowering plants use a "mixed mating system." This means they can do both self-pollination and cross-pollination!
- Some plants produce a single flower type where fruits may contain self-pollinated or cross-pollinated seeds.
- Other plants have two types of flowers. They have open flowers that can be cross-pollinated, and closed flowers that always self-pollinate. This gives them the best of both worlds!
Amazing Self-Pollinating Plants
Let's look at some fascinating examples of plants that self-pollinate:
Orchids with Unique Methods
- The slipper orchid Paphiopedilum parishii has a clever trick. Its anther (the pollen-producing part) changes from a solid to a liquid. It then directly contacts the stigma, without needing any help from insects or wind.
- The tree-living orchid Holcoglossum amesianum performs an amazing feat. Its flower actually rotates its anther 360 degrees against gravity to place pollen into its own stigma! This happens when there is no wind or insects around. This ensures the plant can still make seeds.
- The Madagascan orchid Bulbophyllum bicoloratum also has a special way to self-pollinate. It uses a part of its flower called the rostellum.
Caulokaempferia coenobialis
This Chinese herb uses an oily liquid to move its pollen. A film of pollen, mixed with oil, slides sideways along the flower's style (a stalk-like part) to reach its own stigma. This method is very useful in its shady, humid home where pollinators might be scarce.
Capsella rubella (Red Shepherd's Purse)
This plant is a great example of how self-pollination can be a successful long-term strategy. It started self-pollinating between 50,000 and 100,000 years ago! Its ancestor, Capsella grandiflora, relied on cross-pollination. This shows that self-pollination can be a very good adaptation for survival.
Arabidopsis thaliana
This small plant is a favorite for scientists to study. It mostly self-pollinates, with very little cross-pollination happening in the wild. Scientists believe it evolved to self-pollinate about a million years ago.
Tomato Plants
Tomato plants can also self-pollinate automatically. They have special flower structures that help enclose the stigma. This makes it easier for pollen to reach it without external help.
Why Meiosis is Still Important
Even though self-pollinating plants do not create much new genetic variety, they still use a process called meiosis to make their reproductive cells. Meiosis is important because it helps repair damage to the plant's DNA in each new generation. This keeps the plant healthy and strong, even if it is mostly self-pollinating.
See also
- Self-incompatibility: How some plants prevent self-fertilization.
- Reproduction: The general process of making new living things.
- Monocotyledon reproduction: How a specific group of plants reproduces.
