Pollination

Overview.

Flower.

Seed dispersal.

Overview.

Pollination is the process by which many plants species reproduce.

We will discuss the flowering species of plants.

Flowers are used by these plants, to facilitate pollination.

Flowers typically look bright and attractive.

They also tend to have a sweet smell.

Some flowers have nectar in them.

Plants use beautiful flowers and other attractions to attract pollinators.

The bee is a typical pollinator.

Many other insect or birds, can also be pollinators.

Pollinators carry pollen from flowers in one plant to flowers in another plant.

This results in pollination.

This ultimately enables the plant to produce seeds.

Seeds in turn are dispersed by insects, and other methods.

The seeds germinate in the soil, to grow new plants.

Pollinators and dispersion agents, play an important role, in the eco system.

They help plants to reproduce.

Flower.

Flowers have a male reproductive organ, called the stamen.

The stamen, has a filament, with a small head called the anther.

The anther produces pollen grains.

Each mature pollen grain, contains a tube cell.

This cell has a nucleus, and two male gametes.

The carpel is the female reproductive organ of the flower.

It comprises of a stem called style, with a head called stigma,

and with a ovary in the other end.

The stigma is the receptor for pollen.

Ovaries has ovules.

Ovules have a female gamete.

Bisexual flowers, have both male and female organs.

For example, the rose and hibiscus.

Unisexual flowers, have either a male or a female organ.

For example, papaya, watermelon and pumpkin.

For pollination to occur, pollen has to be transferred from,

the stamen to the stigma.

If the pollination happens in the same flower,

it is called self pollination.

In most other cases, pollination occurs by transferring to the flower,

of another plant of the same species.

This is called cross pollination.

The agents for cross pollination, could be insects and animals,

wind, and water.

Bees for example, sit on a flower, to extract nectar.

During this time some pollen sticks to them.

When they fly away and sit on another flower,

the pollen gets transferred, to the stigma of the flower.

This initiates pollination.

Some plants have pollen which are very light in weight.

This pollen is carried away by the wind,

to pollinate other flowers.

Wheat, Rice, maize, etc., are pollinated in this manner.

In the case of sea grass, water carries the pollen.

Small birds, like humming birds, can also pollinate plants.

When pollen lands on a stigma,

the tube cell produces a pollen tube,

through the style, into the ovule.

The male gametes travel along with the tube nucleus,

through the pollen tube.

The gametes reach the ovule.

One male gamete fuses with a female gamete.

This leads to fertilisation.

Zygote is formed.

Another male gamete, fuses with the polar nuclei,

to eventually form the endosperm.

The zygote divides many times to form the embryo,

within the ovule.

The endosperm surrounds the embryo, and provides,

nutrition to it.

The ovule eventually develops into a seed.

Seed dispersal.

The ovary develops into a fruit.

The seeds are encapsulated within the fruit.

Seeds can be dispersed by many agents, like animals.

The embryo in the seed develops into a baby plant.

Seeds have to disperse over a wide area.

This is to prevent over crowding of plants.

There are many ways, by which seeds are dispersed.

Birds and animals eat the fruit and dispose it else where, in the soil.

Some seeds have spines, which will stick to the fur of animals,

and feathers of birds.

In some cases, seeds are very light in weight.

These seeds are dispersed by wind.

Wheat, Rice, maize, etc., are pollinated in this manner.

Some seeds have tuft of hair, which help it to float in the air.

Cotton seeds and dandelion, have this feature.

Some seeds like sycamore seeds, have wing like features.

Some seeds are dispersed by water.

Lotus and water Lilly, are examples were seeds are dispersed by water.

Coconuts also can float on water bodies, and travel long distances.

Some plants explode the pods, containing the seeds, to disperse the seeds.

Pollination and seed dispersal, is enabled by many other species,

of insects, birds and animals.

All of them play an important role in the ecosystem.

Over use of pesticides often results in the destruction of many useful forms of life.

This damages the ecosystem.

We need to learn to farm and manage plant life, in an eco friendly way.