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do all plants grow from seeds

Plant reproduction without seeds

Not every plant grows from a seed. Some plants, like ferns and mosses, grow from spores. Other plants use asexual vegetative reproduction and grow new plants from rhizomes or tubers. We can also use techniques like grafting or take cuttings to make new plants.

Plants that reproduce from spores

Ferns are very common in New Zealand. If you turn over a fern frond (leaf), you might see some unusual structures called sporangia. The sporangia produce very tiny spores. Spores are different to seeds. They do not contain plant embryos or food stores. When the sporangia break open, the spores are released and dispersed by the wind. If the spore lands in a suitable environment, it can grow into a tiny plant called a gametophyte.

The gametophyte looks like a little, thin green plate. It does not have roots, stems or leaves. The gametophyte is a short-lived plant that has both male and female reproductive organs. These produce male and female gametes that combine in fertilisation to produce an embryo. Once fertilisation takes place, a new fern plant starts to grow into the plant we recognise as a fern. Ferns are the only land plant that has these two separate independent living stages.

Ferns are not the only plants to reproduce from spores. Mosses, liverworts and green algae also have spores.

Plants that reproduce from asexual vegetative reproduction

New plants are sometimes made by asexual vegetative reproduction. These new plants have exactly the same genes as the parent. Some plants – like strawberries – have stems called stolons that grow out sideways above the soil, and new plants grow up along them. Other plants send out underground stems called rhizomes, which form new plants at a distance from the parent. Tubers (for example, potatoes) and bulbs (for example, onions) are also special underground structures that can grow into new plants.

People also make new plants using asexual reproduction. Gardeners grow plants from cuttings. They do this by snipping a young shoot off a plant, dipping it in rooting hormone and placing the cutting in a mixture of sand and potting mix. The cutting soon grows roots and can be transferred outdoors.

Grafting

Grafting and budding are two ways to make new plants. This video, Grafting and budding, demonstrates these two techniques.

Fruit tree breeders often use grafting to make new plants. Grafting allows them to have large plantings of the same fruit variety with exactly the same genetic material. Grafting uses the rootstock of a plant that grows well in the soil and joins it to the plant the breeder wishes to produce.

Nature of science

Although we think of science as always advancing at a steady pace, techniques like cutting and grafting have been around for thousands of years. Science has helped us understand how these techniques work and improve them with advances like rooting hormones and breeding new plant cultivars.

Activity idea

In this video clip, Parts of a fern, Dr Patrick Brownsey from Te Papa Museum shows us the different parts of a fern. As the language used may be too complex for younger students, consider muting the audio and providing your own simpler narration.

Not every plant grows from a seed. Some plants, like ferns and mosses, grow from spores. Other plants use asexual vegetative reproduction and grow new plants from rhizomes or tubers. We can also use techniques like grafting or take cuttings to make new plants.

DK Science: Seed Plants

Most plants grow from seeds. These seed plants fall into two groups, angiosperms and gymnosperms. Angiosperms are the flowering plants. Their seeds develop inside a female reproductive part of the flower, called the ovary, which usually ripens into a protective FRUIT. Gymnosperms (conifers, Ginkgo, and cycads) do not have flowers or ovaries. Their seeds mature inside cones. Seeds may be carried away from the parent plant by wind, water, or animals.

FLYING FRUIT

Dandelion seeds have feathery parachutes to help them fly far from their parent plant. A dandelion flower is actually made up of many small flowers, called florets. Each develops a single fruit. The fruits form inside the closed-up seed head, after the yellow petals have withered away. When the weather is dry, the seed head opens, revealing a ball of parachutes. The slightest breeze lifts the parachutes into the air.

INSIDE A SEED

A seed is the first stage in the life cycle of a plant. Protected inside the tough seed coat, or testa, is the baby plant, called an embryo. Food, which fuels germination and growth, is either packed around the embryo or stored in special seed leaves, called cotyledons.

SPREADING WITHOUT SEEDS

Seeds are not the only means of reproduction. Some plants create offshoots of themselves ? in the form of bulbs, tubers, corms, or rhizomes ? that can grow into new plants. This type of reproduction is called vegetative reproduction. As only one parent plant is needed, the offspring is a clone of its parent.

A bulb is an underground bud with swollen leaf bases. Its food store allows flowers and leaves to grow quickly. New bulbs develop around the old one.

Tuber

A tuber is a swollen stem or root with buds on its surface. When conditions are right, the tuber?s food store allows the buds to grow.

A corm is a swollen underground stem that provides energy for a growing bud. After the food in the old corm is used up, a new corm forms above it.

Rhizome

A rhizome is a horizontal stem that grows underground or on the surface. It divides and produces new buds and shoots along its branches.

GERMINATION OF A RUNNER BEAN

Most seeds require damp, warm conditions in order to sprout. During germination, the seed absorbs water and the embryo starts to use its food store. A young root, or radicle, begins to grow downward. Then a young shoot, or plumule, grows upward. This develops into the stem and produces leaves. The first leaves, called seed leaves or cotyledons, fuel the early growth until the plant?s true leaves appear.

FRUITS

A flower?s ovary usually develops into a fruit to protect the seeds and help disperse them. A fruit may be succulent (fleshy) or dry. Fruit is often tasty and colourful to attract fruit-eating animals. Its seeds can pass through an animal unharmed, falling to the ground in droppings. Seeds may also be dispersed on animals? coats, by the wind, or by the fruit bursting open.

DRY FRUITS

The seeds of dry fruits are dispersed in various ways. Peapods are dry fruits that split and shoot out their seeds by force. The hogweed fruit forms a papery wing around the seed, helping it to float on the breeze. The strawberry is a false fruit, but it is covered by tiny dry fruits, each with a seed.

STRAWBERY

SUCCULENT FRUITS

Fleshy, brightly coloured, and often scented, succulent fruits are designed to attract the animals that eat and disperse them. Fleshy fruits such as apricots and cherries have a woody stone or pip that protects the seed. Called drupes, these fruits form from a single ovary. Many drupes, formed from many ovaries, may cluster to form a compound fruit, such as a raspberry.

Most plants grow from seeds. These seed plants fall into two groups, angiosperms and gymnosperms. Angiosperms are the flowering plants. Their seeds de