POLLINATION.....
By definition,
Pollination is the transfer of pollen grains from the anthers to the stigma. It is a necessary process in the life of a plant because it is the very trigger of reproduction in the group of plants we are studying. That is, flowering plants. Somehow, the male gametes have to make it to the female ones in order for reproduction to occur, and this is the process by which this occurs.

There are two main ways in which pollination can occur and these are:

1:Self pollination;
This occurs in the same flower, or on the same plant, thus the name 'self':

It is favoured in some flowers by adaptations within the flower itself. For example, some flowers have the stigma growing against the anthers such that pollen naturally transfers from one to the other.
However, self pollination is discouraged in most plants, by mechanisms that favour the other kind of pollination.


2:Cross pollination
This kind occurs between flowers on different plants. Pollen 'crosses over' thus the name 'cross'.
It is encouraged in most plants, as said earlier by such mechanisms as these:
-In some flowers the stamens ripens first and shades its pollen before the stigma mature. In such flowers the stigmas do not ripen until the stamen have withered for example protogy.
-In protogeny the carpels ripen before the stamen.
-In unisexual flowers (staminates) or (pistilates) cross-pollination is inevitable.
-Another mechanism is Heterostyly;
This is where some flowers (pins) possess long pistils and short stamens, while others (thrums) possess the opposite.
Cross pollination is encouraged because nature, it is thought, would rather have a mixture of gene material sent down to the off-spring….this favours adaptation and evolution.


Agents of pollination.
These are the 'carriers of pollen' from the anthers to the stigma.
They include wind and insects.

Differences between wind pollinated and insect pollinated flowers.
-Insect pollinated flowers have large brightly colored petals while wind pollinated flowers do not have brightly colored petals.
-Insect pollinated flowers have a scent while wind pollinated do not have a scent.
-Insect pollinated flowers secrete nectar while wind pollinated do not.
-Insect pollinated have Pollen grains which are rough sticky surface and can therefore get stuck on body surfaces of insects while wind pollinated produce light, smooth and often produced on stamens with long filaments hence can easily be carried by wind.
-In insect pollinated flowers the surfaces of the stigmas is sticky while in wind pollinated the surfaces of the stigma is feather like and stigmas are usually large. The styles are long so that the stigma can project from the flower catching pollen floating in the near by air.
-In insect pollinated they may be specially shaped to make it possible for certain insects to visit the flower while in wind pollinated the pollen distribution is not hindered by the size of the leaves because the flowers are arranged in long tubed inflorescence.
-The nectary is so situated that in order to reach it an insect becomes dusty with pollen while in wind pollinated there are no nectaries .

All in all without pollination there would be no reproduction and thus no plants.

After pollination comes fertilisation.

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