Fertilization

The process of fusion of male gamate and female gamate to form zygote ids called fertilization.
First pollination takes place. The pollen grains are produced in male reproductive organs the anther. The pollen grains reach the stigma of gynoecium (female organ) either of the same flower or another flower by some agents like insects. The pollination occurs. The transfer of pollen grains from anther to stigma by agents like insects, wind or water is called pollination. Each pollen grains contains male sex cells.                  
After pollination, pollen grains start germinating on the stigma and each pollen grains form a tube called pollen tube which carries two male sex cell (male gametes) in it. The pollen tube grows and penetrates through the stigma and style. It further grows towards the ovary and reach the ovary. It then enters the embryo sac through micropyle and makes its way to the ovule. The ovule contains female sex cells (female gamate) the egg. The pollen tube burusts within ovule and a male gametes fuses with female gamate and fertilization is completed to form zygote. The zygote is also known as oospore in plants.               
 After fertilization, many changes take place. The sepals, petals and stamens all dry up and fall off. The stigma and style also dry up and the overy grows larger. The fertilized eggs all change into embryo, the ovule into seed and the ovary into fruit.    

When the seeds mature, the fruit dries up and burusts to release the seeds. Each seed germinates and grows into a new plant when they get a favorable conditions like availability of water, heat, light, air etc. In this way, the life cycle of a seed bearing plant completes.