B4 - Sexual Reproduction in Plants

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

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. 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.

Shown is a colour diagram of the reproductive parts of a flower.

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 nectar.

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 ovule.

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!