Seed Dispersal

After fertilisation the seeds are attached to the parent plant. These seeds need to be dispersed away from the parent plant and others to reduce competition for resources such as light energy and water. Your task for this forum is to investigate the variety of different ways in which plants are able to disperse their seeds.

1) Please read pages 192-193 ´Dispersal of seeds and fruits´for background information on this topic.

2) Watch the video below about some interesting ways in which seeds are dispersed.

3) Research on the internet to find one interesting example of seed dispersal. You must attach a picture of the seed and also write a summary of at least 150 words about its stucture and method of dispersal. You may include some other interesting information about the seed also.

IMPORTANT: You must not choose a seed from the textbook or the video. You must not choose a seed which your classmate has already chosen and added to the forum!!!

DUE DATE: You must post your forum by the start of your second class during Week 29 (11/10/10)

Structure:
The cherry seed has a fleshy covering and are obtained from cherry trees. The cherry fruits have a colorful skin, which attract different animals. The seed is resistant to digestive juices, so it can’t be digested by animals.

Seed dispersal:
Cherry seeds dispersal method is dispersal by animals or endozoochory, which means seed dispersal via ingestion. Cherries are edible fruits, which allow different animals, such as birds and mammals, to eat them. These animals eat the fruit, including the seed. When they ingest the cherry, the seed is egested intact, because of its hard covering which is not affected by the digestive juices. The seed is removed from the animal as feces. The seed, after all this process, has moved away from the tree where it had grown, because the animal digestion takes a certain time, in which the animal has managed to move a certain distance looking for more food.

Dispersal of seeds may occur in many ways: by wind, by animals, by water, or some times by an explosive mechanism. In the Water Lily’s case, it’s by water. The benefit of traveling by water is that they can travel extremely long distances, depending on the mode of water dispersal. This may be rivers, lagoons, sea, etc. However, Water Lilies don’t use this benefit, because this kind of flower makes a fruit that floats in the water for a while and then drops down the seed to the bottom to take root on the floor of the pond.
The specific or scientific name for the Water Lily is Nymphaeaceae. They live in freshwater areas in temperate and tropical climates around the world. Water lilies are rooted in soil in bodies of water, with round leaves and flowers floating on the water surface.
There are about 70 species of water lilies around the world, and they are divided into two main categories: hardy and tropical. Hardy Water Lilies bloom only during the day, but tropical water lilies can bloom either during the day or at night.

Seeds can be dispersed in four ways:
1. Wind dispersal: some plants have adapted so that the seeds can be carried away by the wind. These are mainly small seeds that have adapted to this king of dispersal. Dandelions for example.
2. Water dispersal: the seed of some plants are carried away by water. This is mainly when the plant’s fruit can float. Later they can germinated in new places.
3. Animal Dispersal: some seeds are made to get tangled in animal fur or feathers and others to eat them. All of these so that the seeds can be carried away from their plants, so they germinate in new places.
4. Explosions: when plants disperse their own seed. In some plants the fruits just split open or use ‘jet propulsion’ so that seeds can de dispersed away from their plants. In other cases the fruit is dropped to the floor and when making contact with the ground it opens; leaving the seed free to roll far from the tree/plant.

Coconut
Structure:
The coconut is seed fruit that grows in the coconut palm. On the outside it’s a husk, which is the brown part of the coconut. Then we have inside coat, which is like a “shell”. This part is made of fiber and it is called coir. This is the coat, which is thin. Then we can find the white flesh or “copra” and the ‘coconut milk’. The “copra” and the coconut milk are part of the seed



Seed Dispersal:
In the wild the coconut is dispersed from one place to another via flotation on the water, in other words by rivers, seas, etc. The coconut’s husk is light so it let’s the fruit float for days, even moths, without sinking. During this period the water does not damage the seed. When the coconut washes up in a different place, for example a beach, the seed germinates through one of the three thin (inside) layer of the coconut; leaving the husk and the inside coat apart.[code]

Structure:
The seed called “Polygala Arenaria” has a very particular structure. It is usually about 2.2 mm long, with short, spiky purple hair on top to protect that area of the seed since it is quite delicate. It also has a kind of shell made of bark – like tissue on the bottom that serves tha same purpose for the bottom of the seed. The body of the seed is of a shiny greenish colour and it is covered in an oily layer to prevent any damage on this part of the seed.

Dispersal Mechanism:
This plant has a remarkable dispersal mechanism which consists basically in making sure its seeds transport to other places through water currents like rivers. This is why these plants grow near river banks, and their seeds have a lower density than water so they can float. As they reach the water, the seeds have a high impermeable nature that allows them to stay for a rather long period in water until it reaches new land to grow in.

These seeds are characteristic because they form big fluffy-like lumps of seeds, hence the name cottony seeds. These lumps contain dense number of seeds, each with its own silky hairs that stick them together. Their size, very small; their weight, extremely light; and their shape, dandelion like, make it the perfect seed for it to be transported by the wind. And that is the case. When a gust of wind passes through this cottony seeds, they get loose and fly away in those lumps of seeds far from their parent plant. This is good because it increases the chance of the plant becoming a different kind of plant different to the parent plant (variability). As they move through the air, these lumps divide into smaller and smaller groups of seeds, making the chances of variability even greater. Also the plant releases an immense number of seeds, and this makes the growth of offspring more certain, because maybe some seeds will be eaten or just destroyed, but as the number is great, the plant has a million opportunities and will almost certainly achieve that an offspring can grow and develop in some place.

Each plant develops a different way to disperse their seeds, so that there is more variety. One of this ways is by using animals to transport the seeds; and there are also several ways to do this. They can be dispersed externally by animals, by using adhesive mucus, barbs, hooks or spines so that the seed gets adhered into the animal’s fur. This is a very strange way of seed dispersal, though it is very effective, especially with wide-ranging animals.

Other way of seed dispersal by animals is by ingestion. Plants that use this method are those that have nutritious fruit so that the animal eats it. This is the most common one, especially in tropical rainforests. Birds and mammals are the most important seed dispersers, but there are also some reptiles, fish or turtles. Negative aspect of this is that they depend on one animal species; the extinction of the animal that eats this fruit will decrease the amount of this plant or simply make it vanish.

Structure:
The Malus Domestica, or better known as Apple, matures in Autumn, and it is typically 5 to 9 centimeters in diameter. The center of the apple contains five carpels arranged like a star, each one containing one to three seeds.


Dispersal Method:
When the fruit is mature enough, it falls to the ground, ready for animals to eat it. The animal ingests the fruit with the seeds in it, which are resistant to the acid on the stomach. Later on, the animal eliminates the seed from the body, preferably, far from the parent plant, for the offspring not to use the parents space or nutrients.

Seeds can be dispersed in seven different ways:
Wind: Some fruits are adapted to catching the wind and being blown away such as sycamore "helicopters" or dandelion "clocks".
Bursting: These fruits suddenly burst open throwing the seeds in all directions such as peas, laburnum or gorse.
Shakers: Poppy seed heads, when dried by the sun, have little holes all around their top (like a pepper shaker). These shake when it's windy and the and the tiny seeds are thrown out of the shaker through the holes.
Water: some fruits are waterproof and can float. Coconuts are a good example.
Catching a lift: Some fruits have little tiny hooks on them such as burdocks and cleavers. These little hooks catch on passing animals if they brush against the plant and get carried away.
Animal food: Lots of fruits are really tasty to animals, such as blackberries, apples and gooseberries. When an animal eats these fruits the little seeds are not digested and pass through the animal, unharmed and surrounded by fertiliser.
Drop and roll: The casing of the fruits from trees such as horse chestnuts (conkers) split when they land on the ground. The fruit then rolls away from the tree.

The fruit I chose was a tomato. In the wild, original state, tomatoes required cross-pollination; they were much more self-incompatible than domestic cultivars. As a floral device to reduce selfing, the pistil of wild tomatoes extends farther out of the flower than today's cultivars. The stamens were, and remain, entirely within the closed corolla.

As tomatoes were moved from their native areas, their traditional pollinators, (probably a species of halictid bee[citation needed]) did not move with them. The trait of self-fertility became an advantage, and domestic cultivars of tomato have been selected to maximize this trait.

This is not the same as self-pollination, despite the common claim that tomatoes do so. That tomatoes pollinate themselves poorly without outside aid is clearly shown in greenhouse situations where pollination must be aided by artificial wind, vibration of the plants (one brand of vibrator is a wand called an "electric bee" that is used manually), or more often today, by cultured bumblebees[citation needed]. The anther of a tomato flower is shaped like a hollow tube, with the pollen produced within the structure, rather than on the surface as in most species. The pollen moves through pores in the anther, but very little pollen is shed without some kind of outside motion. The best source of outside motion is a sonicating bee such as a bumblebee or the original wild halictid pollinator. In an outside setting, wind or animals provide sufficient motion to produce commercially viable crops.

Rose:

The primary vector for seed dispersal in roses is by birds. The fleshy fruit (rose hips) is highly attractive to birds and the prickly seeds are either discarded or pass unharmed through the bird's digestive system.

Another method that is by humans is the grafting method, this can be by:

1) Cut: Cut off a branch of the understock, leaving a stub at least a foot long.
2) Union: Match the two parts together

Interesting fact:
Native Americans made medicinal tea from wild roses, which were used as a remedy for diarrhea and stomach maladies. They sometimes smoked the inner bark. The Crow used a solution made by boiling rose roots in a compress to reduce swelling. The same solution was drunk for mouth bleeding and gargled as a remedy for tonsillitis and sore throats; vapor from this solution was inhaled for nose bleeding.

The gomphocarpus physocarpus, better known as Hairy Balls.



It is an undershrub, that can grow to over six feet. The plant blooms in warm months with flowers of white colour and slight aroma. It performs sexual reproduction, it requires pollen (male gametes) and an ovum to be fertilised (female gametes). These are pollinised primarily by monarch butterflies and their young caterpillars.



This plant has its seeds inside ballon like structures which grow in size as the seeds develop, which are attached to feather like projections, because they are dispersed by wind, to avoid competition for space. Once the seeds are ready and mature, they break open the carpel where they were being held, and if there is enough wind, they may even end up kilometres away from the parent plant.



It is very useful that there are specimens far away from each other because this means variation (which is basicly differences between a same specie) , as it generates the possibility of resistance to certain diseases, so if one which is immune to a certain disease is able to carry its pollen (via the butterflies) to another's stigma which is not immune, their offspring are likely to have that same treat.

'Chrysanthemum

Structure: The chrysanthemum flower has a plate like flower, much like the daisy's, its petals colours are usually bright colours like white, yellow, red and purple, the flower is supported by a strong stalk which help makes the flower raise. It has its reproductive organs in the center of the petals forming a circle, in the outer part of the circle we find the anthers which have a small filament so that it can brush insects and the stigma is found in the center of the circle, the stigma has a reduced style too.
Some of the chrysanthemums variate, giving them different petal shapes, we should also mention that this flowers release a strong scent, sometimes it differs depending on the type of chrysanthemum.

Seed Dispersal: The mechanism this flowers uses to disperse its pollen is by animals, especially insects. The chrysanthemum has bright colours and scents which attracts insects, it also produces nectar which will clearly attract more insects, when the insect goes to consume nectar in the flower, the pollen in the outer ring of the circle hooks itself to the insect, when the insect travels to another flower the pollen is deposited in the sticky stigma. This is what we call pollination.



A bee pollinating a yellow chrysanthemum.

Night blooming Cereus (Epiphyllum oxypetalum)

Structure: It is part of the cactus family so it holds some characteristics with them, like being adapted to dry enviroments. This plant has slightly thin branches with large and broad leaves, from this branches a large white flower blooms, this flower has a powerful smell. A special characteristic of this flower's that its flower only blooms for one night. Its petals are long
and not specially wide. It's stamen and stigma are not very different from other flowers.



Seed Dispersion: This plant disperses its seed by nocturnal animals like bats and moths. It attracts them with its powerful smell so that they drink its nectar, sticking its pollen into the bat or moth which will then take it to another plant to breed. It only blooms for one night, meaning that its smell has to be very powerful so that at least one animal can spread its seeds.

Video showing the flower bloom:

Seed dispersal is very important for the continuality of plants. When seeds do not disperse and fall very near the plant, those plants will grow very near and this will be bad for them, because they will have to share nutrients. But if seeds are dispersed, plants may grow alone and not share essential nutrients.


Parachute method

Another way of seed dispersal is the Parachute method, this include seeds or achenes (one-seeded fruits) with an elevated, umbrella-like crown of intricately-branched hairs at the top, often produced in globose heads or puff-like clusters. The slightest gust of wind catches the elaborate crown of plumose hairs, raising and propelling the seed into the air like a parachute. This is the classic mechanism of dispersal for the Eurasian dandelion (Taraxacum officinale) and includes numerous weedy and native members of the Sunflower Family (Asteraceae). A giant Eurasian version of the dandelion called salsify or goat's beard (Tragopogon dubius), is one of the most successful wind-travelers in North America. Its seeds have literally blown across mountain ranges, colonizing vast fields of open land.
In some parachutes, the crown of silky hairs arises directly from the top of the seed (not on an umbrella-like stalk). Again, the Sunflower Family (world's largest plant family with about 24,000 described species) contains many weedy representatives with this type of parachute seed.

A spike covered fruit, it has a yellow colour, and a green coloured flesh, it has hard black seeds and a boring taste.

Dispersion Method: The Horned Melon is coated by horn-like projections, it has the characteristic it can be eaten any time of its growth period, and taste the same, this provides the fruit will be dispersed at a random moment, once the carrier has decided to take the fruit due to its colours, or the fact it is the only source of food available momentarily, several things can happen, the carrier may taste the fruit and dislike the boring taste and throw the fruit, leading to it rotting and the seeds getting planted, eat all the flesh and spit out the seeds on various locations, or in some cases (human cases) take the fruit as decoration,this making it travel further and even out of the country, the horned melon, native to Africa is now cultivated in: California, Chile, Australia and New Zealand

Dispersal is necessary for plant because that is the only way the younger plants can survive for a longer time. There are several ways of dispersion:
1. Wind: When wind blows hard enough it catches the seeds and blow them away until they find a new location. Example: dandelion, sycamore
2. Animals: When an animal eats a fruit, the seed is not digested so is expelled away by the animal faces. Example: plum
3. Water: waterproof fruits travel by water until they find their new location. Example: Coconut
4. Catching a lift: Some seeds have tiny hooks that attaches to the animal fur or clothes and carried away until they fall out. Example: aven
5. Explosive mechanism: some trees have casings that split and twist, throwing the seeds away. Example: lupin

SUNFLOWER SEED
The sunflower have enormous amount of seeds. This seeds are dispersed by wind, animal, catching a lift and water
1. Wind: the sunflower seed have a structure similar to a parachute. It is composed by a papus (the parachute), the stem and the seed, which is found at the end of the stem. When the wind blows, it catches the papus with the seed and throws it away.
2. Animal: the “large sunflower” is a bigger type of sunflower that does not produce a papus. The way it is dispersed is by the birds, which the catch the seed and throw them away.
3. Catching a lift: the “notorious cocklebur” produces a type of hook that attaches to the animal fur and carried away until they fall.
4. Water: sometimes the seeds land in water. They are carried away until they find their new location. This is considered the less effective way of dispersion.

Seed dispersal is the movement and the transport of seeds away from the parent plant. Seeds can be dispersed by wind, animals and also by water.

Sunflower (Helianthus annuus)

Its made by many small flowers crowded together. The outer flowers (ray florets) are often yellow, brown and orange. The flowers inside the circular head (disc florets) mature into seeds.

Wind: When the flower goes to seed, they form structures similar to parachutes. The top part of the tiny parachute is called the pappus, has hair and its very light. The stem attaches to the pappus and the bottom of the seed or fruit of the sunflower. Wind catches the hairy part of the pappus and lifts the seed from the plant into the air. When the wind is strong enough it can carry the pappus for miles, but when it’s to weak, the pappus comes to rest and attaches in a new location.

Animals: some types of sunflowers do not have pappus so animals also may help on the transport. The big seed are the favourite of birds for example, they carry them away or cause them to fall. Some seeds can get caught into the animals fur.

Water: some seeds might get into rivers and streams for example. The water carries the seed downstream until it becomes settled or picked up again by another animal. This is the less efficient form of dispersion according to the sunflower



PD: sorry, I just realized (after I posted in the forum) I did the same flower as Macarena Moreno, but I didn't notice page 2 existed before I post this, and we posted on the forum nearly the same time.

Leguminosae: explisive seed dispersal.

Seed dispersal is very important for the reproduction of plants first because if the seed falls too near to the mother plant, the mother plant will take all the nutrients from the ground and will not let the near plant to grow. Also if the plant manages to grow and pollinates his mother plant, there will be no variation in the genetic material.

Explosive seed dispersal is the kind of dispersal when the fruit bursts open by elastic contraction in tissue. The fruits of leguminosae is shaped in order to burst open through two “weak points” so when the fruit bursts open, the seeds will go further away from the mother plant as possible.

The mayor advantage of this method is that the seeds go in different directions when the fruit bursts, contrary to animal and wind dispersal when all the seeds go the same direction.