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Plants are living organisms. That means they need to reproduce in order to pass on their genes to future generations. Plants can create offspring through either sexual or asexual reproduction.
Sexual reproduction requires genetic material (DNA) from two parents. The parent plants have male and female sex cells, called gametes. The genetic material from the male and female gametes combines to produce offspring. This process is called fertilization.
Seeds produced through fertilization contain genetic material from both parents. As a result, the offspring are not genetically identical to either of the parent plants. This genetic diversity can help them survive if the environment changes.
Flowering plants reproduce sexually through a process called pollination. The flowers contain male sex organs called stamens and female sex organs called pistils. The anther is the part of the stamen that contains pollen. This pollen needs to be moved to a part of the pistil called the stigma.
Not all flowers are large and brightly coloured! Some flowering plants, like grasses, have flowers that are tiny and may even be green, which can make them hard to see.
Plants can either self-pollinate or cross-pollinate. Self-pollination happens when a plant’s own pollen fertilizes its own ovules. Cross-pollination happens when the wind or animals move pollen from one plant to fertilize the ovules on a different plant. The advantage of cross-pollination is that it promotes genetic diversity. Some plants have features that prevent self-pollination, such as pollen and ovules that develop at different times.
Pollinators are animals that carry pollen between plants. Many pollinators are insects, like bees, butterflies, moths and beetles. Some birds, including hummingbirds, also play a part. Likewise, certain mammals, like bats and rodents, move pollen between plants. The colours and smells of flowers often attract pollinators. Pollen will stick to a pollinator’s body as it feeds on the flower’s nectar.
Fertilization is the next step after pollination. Once it reaches the pistil, the pollen needs to fertilize an egg inside the stigma. This egg is called an ovule.
Fertilization creates fruits that contain seeds. Some fruits are fleshy, like oranges and watermelons. Others are dry, like acorns or walnuts. These fruits are an attractive food for various animals. After digesting fruit, animals expel waste that contains seeds. This way, seeds can take root and grow in places far from the plants that produced them!
Some plants have no flowers at all. Flowering plants are a group of plants called angiosperms. There are also non-flowering plants. These include mosses, ferns and conifers.
Asexual reproduction only requires DNA from one parent. It creates offspring that are genetically identical to the parent. Genetically identical offspring are called clones. Clones lack genetic diversity. This makes them more susceptible to disease. It also makes them less adaptable to changes in the environment.
There are different methods of asexual reproduction. They include vegetative propagation and fragmentation.
Vegetative propagation does not require seeds or spores. Instead, offspring grow from a part of the parent plant. In different plants, vegetative propagation happens in different ways. Here are a few examples.
- Garlic, onions and tulip plants all reproduce using true bulbs. These short underground stems are also called scaly bulbs. They have a basal plate that is usually surrounded by modified leaves. These leaves form a papery covering called a tunic. New bulbs grow off of the parent bulb’s basal plate.
- Crocuses reproduce using corms, which are similar to true bulbs. However, a corm doesn’t have as many layers. Corms are used up during the growing season and get replaced by one or more new corms.
- Potato plants reproduce using tubers. These underground growths produce new plants from stems or growing points called eyes.
- Ginger plants reproduce using rhizomes. These stems that grow sideways along the soil or just below the surface. They branch apart to produce new points of growth.
- Strawberry plants reproduce using stolons. They look like branches growing along the ground. Stolons anchor themselves to the ground and develop roots. And these roots grow into new plants.
A tuber isn’t a root. It’s a modified stem that grows underground. Corms and rhizomes are other examples of specialized stems.
Did you know?
Apomixis is a form of asexual reproduction in some species of grasses. The parent plant produces seeds without fertilization.
Fragmentation is another form of asexual reproduction. It involves new plants growing from small parts of the parent plant that fall to the ground. For example, animals or the wind can break stems or leaves off plants. This is one of the ways that plants like liverworts and mosses reproduce.
Horticulturists are people who study plants. They often use asexual reproduction through fragmentation to grow new plants. They do this by cutting a leaf off a plant and placing it in water or soil. This process is often called propagating from cuttings.
Did you know?
The coco de mer (sea coconut) produces the largest seed of any plant. It grows in the Seychelle Islands. On average, the seeds weigh 25 kg. They can grow to 500 cm in diameter!