Flowers serve one purpose for the plant and that is to attract a pollinator. They may be scented, offer sweet nectar but it is attracting the pollinator- be it bat, moth, bee or other insect or even wind or water, which is their aim. Pollen is held in anthers which are part of the male reproductive system and are usually borne on filaments (stalks). Thepollinator , seeking food usually, is dabbed with pollen as it enters or leaves the flower. As it enters another floer, it will bruch past the female reproductive organ called the style, at the end of which is a sitcky pad called the stigma, On this, the pollen is deposited. This process of the transfer of pollen grains from one flower to another is pollination.
Fertilisation occurs when the pollen grows a pollen tube (it is said to have germinated) and this tube grows down the style, which is tubular, and into the ovary, which is at the end of the style. In the ovary are the ova or egs and, so long as the pollen is suitable, the male gamete is released into the ovary and fertilises the ova. This is fertilisation.
For pollination to be automatically followed by gertmination is unusual because each stigma may receive hundreds of pollen grains from pollinators who may have visited several flowers. Some only serve a sinlge pollinator but most flowers feed a fair range of them and only if they deposit the right pollen (from the same species) on the stigma when the ova is ready for fertilisation will germination of the pollen grain and the growth of the pollen tube occur.
Chemical inhibotors may prevent pollen grains from germinating unless they are deposited on the same species of plant. This prevents strange crosses in nature and usually prevents inter-generic hybrids from occuring naturally (although it does happen!).
Once the ova is fertilised the ovary swells to become the fruit (in angiosperms), or part of the cone (in gymnosperms). The seeds form and fall to the ground – they may be dispersed in the fruit but eventually they reach the ground. The fruit or body dies away and the seed itself will hopefully find itself in the ideal place to grow. So long as conditions are right (for tropical trees this may be right away or for temperate plants this may mean waiting during a dormant period, which is controlled by other processes), germination in the true sense will occur which is when the radicle grows up to create new leaves and the hypocotyl grows downwards to create new roots. This is seed germination and a new plant may be formed, all being well!
