Question

what is dispersal ? why do plants disperse their seeds

Answer 1

Seed dispersal is the movement or transport of seeds away from the parent.
Seeds are dispersed for multipe reason. The first one being if they were not spread out, then over crowding would occur, if each individual plant doesn’t have enough room for root growth, then they could all die. The second being that seeds spread all over the place help the plant’s species survive.

Answer 2

Plants make seeds that can grow into new plants, but if the seeds just fall to the ground under the parent plant, they might not get enough sun, water or nutrients from the soil. Because plants cannot walk around and take their seeds to other places, they have developed other methods to disperse (move) their seeds. The most common methods are wind, water, animals, explosion and fire.



Have you ever blown on a dandelion head and watched the seeds float away? This is wind dispersal. Seeds from plants like dandelions, swan plants and cottonwood trees are light and have feathery bristles and can be carried long distances by the wind. Some plants, like kauri and maple trees, have ‘winged’ seeds. They don’t float away but flutter to the ground. With wind dispersal, the seeds are simply blown about and land in all kinds of places. To help their chances that at least some of the seeds land in a place suitable for growth, these plants have to produce lots of seeds.

Water dispersal

Many plants have seeds that use water as a means of dispersal. The seeds float away from the parent plant. Mangrove trees live in estuaries. If a mangrove seed falls during low tide, it can begin to root in the soil. If the seeds fall in the water, they are carried away by the tide to grow somewhere else. Kōwhai trees also use water dispersal. They have a hard seed coat that allows them to float down streams and rivers. That is one of the reasons kōwhai trees are commonly found on stream banks.

Animal dispersal





ARTICLE

 

Seed dispersal 

EXPLORE

Plants make seeds that can grow into new plants, but if the seeds just fall to the ground under the parent plant, they might not get enough sun, water or nutrients from the soil. Because plants cannot walk around and take their seeds to other places, they have developed other methods to disperse (move) their seeds. The most common methods are wind, water, animals, explosion and fire.



Dandelion seeds

Dandelion seeds float away in the wind. To make sure at least some of the seeds land in a suitable growing place, the plant has to produce lots of seeds.

Wind dispersal

Have you ever blown on a dandelion head and watched the seeds float away? This is wind dispersal. Seeds from plants like dandelions, swan plants and cottonwood trees are light and have feathery bristles and can be carried long distances by the wind. Some plants, like kauri and maple trees, have ‘winged’ seeds. They don’t float away but flutter to the ground. With wind dispersal, the seeds are simply blown about and land in all kinds of places. To help their chances that at least some of the seeds land in a place suitable for growth, these plants have to produce lots of seeds.

Water dispersal

Many plants have seeds that use water as a means of dispersal. The seeds float away from the parent plant. Mangrove trees live in estuaries. If a mangrove seed falls during low tide, it can begin to root in the soil. If the seeds fall in the water, they are carried away by the tide to grow somewhere else. Kōwhai trees also use water dispersal. They have a hard seed coat that allows them to float down streams and rivers. That is one of the reasons kōwhai trees are commonly found on stream banks.

Animal dispersal



Kererū feeding on kawakawa

The kererū is important in the seed dispersal of large native berries in forest ecosystems. Trees such as the kawakawa rely on native birds for seed dispersal.

Over 70% of plants in our woody forests in New Zealand have fleshy fruit that is eaten by birds. Chemicals in our native birds’ digestive systems help to weaken the tough coats around these seeds. Birds often fly far away from the parent plant and disperse the seeds in their droppings. The kererū, tūī and bellbird play an important role in seed dispersal. Trees that produce the largest fruit – miro, pūriri, tawa and taraire – rely on the kererū because it has such a large, wide beak to eat the fruit.

Some seeds have hooks or barbs that catch onto an animal’s fur, feathers or skin. Plants like pittosporum have sticky seeds that can be carried away by birds. Humans can also spread seeds if they get stuck to our clothing or shoes – and if we throw fruit pips and stones out of the car window!