Final answer:
In seed germination, the union of gametes is not a stage as it occurs before seed formation. Seed germination consists of stages like metabolism activation, food digestion, cell division, and water absorption. The hormone abscisic acid is involved in ending seed dormancy.
Step-by-step explanation:
The stage in seed germination that is not a part of the process is e) the union of gametes. Seed germination includes various stages such as a) activation of metabolism, b) digestion of stored food, c) cell division, and d) imbibition, which is the absorption of water by the seed. The union of gametes is a part of sexual reproduction and occurs before seed formation, not during the germination process. A decrease in the level of abscisic acid releases seeds from dormancy, which is essential for the commencement of germination. Moreover, apart from germination stages, processes such as propulsion and absorption occur throughout the alimentary canal, the digestion of sucrose is an example of a catabolic process, and the formation of a diploid cell in a life cycle is due to fertilization.