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The Life Cycle of a Tomato Plant

Above: Image © brovoza, iStockphoto.com

Reproduction

Tomato plants belong to the plant group known as flowering plants or angiosperms. The tomato plant reproduces sexually, meaning that it requires both female and male organs to produce seeds. Every tomato seed has a tiny tomato plant inside. When the conditions are just right, tomato seeds will germinate.

For more information about tomato seed germination, read the backgrounder:

Seed Germination

As the seed germinates, the radicle or young root first appears and grows down into the ground. The cotyledons or seed leaves then appear and grow up towards the Sun and the young plant develops true leaves. As the plant matures, more leaves develop and flower buds form (see Figure 1). On mature tomato plants, flowers develop and this is where sexual reproduction occurs.

Flower Structure

Flowers are important for reproduction and the production of seeds. A tomato flower is sometimes referred to as a perfect flower because both male and female organs are located within the same flower (see Figure 2).

The tomato flower consists of four main parts:

  1. Sepal: This part of the flower, which is green in colour, is first visible when the bud forms. It protects the flower bud before it opens.
  2. Petal: This is the part of the flower that attracts bumble bees. In tomato flowers, the petals are usually yellow in colour.
  3. Stamen: This is the male part of the flower. It usually consists of the filament and an anther with pollen which is found at the top of the filament. The pollen contains the male genetic information. In tomato flowers, the stamens are fused into a tube-shaped structure. They are also yellow like the petals.
  4. Pistil: This is the female part of the flower. It consists of the stigma, style, and ovary and is located at the centre of the flower, surrounded by the stamens.

The female reproductive organ, the ovary, is located at the base of the pistil. The ovary contains the ovules. Once the ovules are fertilized, an embryo can develop and form seeds that will be found inside the tomato fruit.

Fruit Development

For flowers to develop into the tomato fruit that we eat, two things need to happen in the flowers: pollination and fertilization.

  1. Pollination: This is a process where the pollen, from anthers, is deposited onto the stigma. This can be done by the wind (wind pollination) or by bumble bees through buzz pollination.
    Buzz pollination occurs when a bee lands on a flower and vibrates its flight muscles. This movement can shake loose pollen from the flower. Some of these pollen grains may land in other flowers, resulting in pollination.
  2. Fertilization: During this process, the male and the female gametes, from the pollen and ovule, combine. This is similar to when sperm and egg cells combine in animals. The two gametes come together in the ovary and develop into a seed, which contains the embryo, endosperm, and seed coat. Once the seeds are formed, the tomato life cycle can begin all over again.

Fruit or Vegetable?

Is tomato a fruit or a vegetable? From a culinary (cooking) point of view, tomato is considered a vegetable primarily because it is not sweet and not usually used in desserts. From a botanical point of view, a tomato is in fact a fruit. A fruit is defined as a part of a plant that develops from a flower’s ovary and contains seeds. Since a tomato develops from its flower’s ovary and contains seeds, then a tomato is in fact a fruit and not a vegetable.

Glossary

Angiosperm

Flowering plant.

Anther

Part of the stamen where pollen is produced.

Buzz Pollination

This process occurs when bumble bees land on flowers and shake the pollen off of the stamens by contracting their flight muscles causing vibrations.

Cotyledons

The part of an embryonic plant that will become the first leaves. These are also known as seed leaves.

Embryo

Tiny immature plant inside a seed.

Endosperm

The part of a seed that stores food for use by the embryo during germination.

Fertilization

The process when two gametes come together and develop into a seed.

Gametes

Cells that can fuse during sexual reproduction and that each contain half of the genetic information. In flowering plants the male gamete is found in the pollen and the female gamete is found in the ovule.

Germination

The process of a plant starting to grow from a seed. This usually happens after a period of dormancy. Good environmental conditions are important to start germination.

Filament

Part of the stamen that supports the anther.

Ovary

Part of the pistil that contains the ovules.

Ovule

Located within the female ovary. It contains female genetic information and after fertilization can develop into a seed.

Pedicel

The stem that attaches a flower to the main plant.

Petal

This is the part of the flower that attracts bumble bees. In tomato flowers, the petals usually are yellow in colour.

Pistil

The female part of the flower. It consists of the stigma, style, and contains the ovary and the ovules, which contain the female genetic information.

Pollen

Is found on the anther at the top of the filament, which contains the male genetic information.

Radicle

The part of an embryo that will become the root.

Seed Coat

Protective covering of a seed.

Seedling

Young plant that develops from a seed.

Sepal

This part of the flower, which is green in colour, is first visible when the bud forms. It protects the flower bud before it opens.

Sexual Reproduction

In plants, this type of reproduction occurs when male pollen is deposited on the female plant organs in order to produce seeds.

Stamen

This is the male part of the flower. It consists of the filament and anther with pollen, which contains the male genetic information.

Stigma

This is a part of the pistil. It is located on the top of the style, above the ovary. This is where the pollen is deposited to allow fertilization.

Style

Part of the pistil above the ovary and below the stigma.

Wind Pollination

This is a process that occurs when flowers are pollinated with the help of wind.

References

EXTERNAL RESOURCES