Plant Reproduction

Plants are living organisms. That means they need to reproduce in order to pass on their genesgenes to future generations. Plants can create offspringoffspring through either sexual or asexual reproduction.

Sexual Reproduction

Sexual reproduction requires genetic material (DNADNA) 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. We call this process fertilization. The product of sexual reproduction are seeds.

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. Flowers contain male sex organs called stamens and female sex organs called pistils. The anther is the part of the stamen that contains pollen. Pollen contains the male gametes. Pollen must be moved to a part of the pistil called the stigma for reproduction to take place. 

The outermost parts of the flower are green structures called sepals. They protect the flower before it opens. Inside the sepals are the petals. These are usually colourful. Petals on flowers are actually modified leaves. Within the petals are the stamens. Each stamen contains a filament topped by pollen-producing cells. The innermost part of the flower is the carpel. The carpel contains the ovary. This is where the eggs, or ovules, are located. The pollen from another flower must enter the ovary and fertilize an ovule in order for a seed to start developing. 

Misconception Alert

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. 

Sometimes plants pollinate themselves. Other times plants pollinate other plants.

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 another. The advantage of cross-pollination is that it helps keep a species genetically diverse. Genetic diversity comes in handy when conditions change and organisms need to adapt to the change. Some plants have features that actually prevent self-pollination. This includes things 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 nectarnectar. 

Fertilization is the next step after pollination. During fertilization, the male gametes from the pollen join with the female gametes in the egg. The egg, or eggs, are found inside the stigma. The scientific word for an egg is an ovuleovule.

Fertilization creates fruit that contain seeds. Some fruits are fleshy, like oranges and watermelons. Others are dry, like acorns or walnuts. Fruits are an attractive food for various animals. After eating fruit, animals expel waste that contains seeds. This way, seeds can take root and grow in places far from the plants that produced them!

Misconception Alert

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

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 less able to fight 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 need 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 base 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 base.
• 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. Tubers produce new plants from stems or growing points called eyes.
• Ginger plants reproduce using rhizomes. These are stems that grow sideways along the soil or just below the surface. They branch out 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. The roots grow into new plants.

Misconception Alert

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 a parent plant that fall to the ground. 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 or a stem 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!