Year 1 · Reproduction in plants and animals · Section 6.5
Asexual reproduction
A new plant
In sexual reproduction, a male sex-cell nucleus fuses with an egg-cell nucleus. In flowering plants, this can lead to seed formation.
In asexual reproduction, part of a plant grows into a new plant without fertilisation. For example, tiny plantlets may develop along a leaf edge, fall off and grow independently.
Cell division
Most nucleated cells of a plant contain the same genetic information in their chromosomes. Before ordinary cell division, DNA is copied. Each daughter cell normally receives a complete set of chromosomes.
Plants produced asexually are therefore genetically almost identical to the parent: they are clones, except for differences that may arise through mutations.
Tubers
A potato is a stem tuber: a swollen underground stem storing food and carrying buds, often called eyes. A bud can grow into a new plant, which can produce more tubers and repeat the cycle.
Bulbs
Bulbs, such as those of tulips and onions, consist of a short stem called the basal plate, fleshy scale leaves storing food, and buds.
One bud can develop into a shoot, while other buds form new bulbs. These offspring are genetically almost identical to the parent.
Runners and rhizomes
Strawberry plants produce runners, horizontal stems above the ground that form young plants at points along their length.
Plants such as lily-of-the-valley produce new shoots from rhizomes, horizontal underground stems.
Propagation and tissue culture
Growers use asexual reproduction to propagate plants:
- Cuttings: A piece of stem or leaf develops into a new plant.
- Tissue culture: Small pieces of growing tissue, often from a bud, are placed on a suitable sterile nutrient medium. Many genetically similar plantlets can develop, allowing thousands of plants to be produced from one parent.
Other organisms
Unicellular organisms also reproduce asexually: bacteria divide, and many yeasts reproduce by budding.
Some animals, including many jellyfish, have an asexual stage. In a typical jellyfish life cycle, a polyp produces young jellyfish asexually. They grow into adults, which reproduce sexually. The resulting larvae can develop into new polyps.
Glossary
- Bulbs
- Underground organs with a short stem, fleshy scale leaves containing food reserves, and buds.
- Basal plate
- The short stem at the base of a bulb, to which its scale leaves attach.
- Sexual reproduction
- Reproduction involving the fusion of male and female sex-cell nuclei during fertilisation.
- Growing point
- A region of dividing plant cells, often in a bud, producing new tissues.
- Stem tubers
- Swollen stem structures storing food and bearing buds, as in potatoes.
- Buds
- Structures containing growing points that can develop into shoots or flowers.
- Asexual reproduction
- Production of offspring without the fusion of sex cells; offspring are genetically almost identical to the parent.
- Scale leaves
- Thickened leaves storing food in a bulb.
- Runners
- Horizontal above-ground stems that form new plants, as in strawberries.
- Propagation
- Producing new plants, for example through cuttings or tissue culture.
- Tissue culture
- Growing small pieces of plant tissue on a nutrient medium to produce new plants.
- Rhizomes
- Horizontal underground stems that can produce new shoots, as in lily-of-the-valley.
Frequently asked questions
What is asexual reproduction?
A new organism is produced without fertilisation. The offspring is genetically almost identical to its parent.
How can plants reproduce asexually?
Through structures such as tubers, bulbs, runners and rhizomes, or through methods such as cuttings and tissue culture.
How do jellyfish reproduce?
In many jellyfish species, polyps produce young jellyfish asexually. Adult jellyfish reproduce sexually, producing larvae that can develop into new polyps.