Gametogamy

Gametogamy is sexual fusion – copulation or fertlization – of two single-celled gametes of different sex and the union of their gamete nuclei (and corresponding extranuclear structures) giving the zygote nucleus, as well as whole zygotic content.^[1][2]

According to its morphology, size and other properties, most forms of gametogamy are as follows:

• fertilization includes two gametes fusion, when different mating types form a zygote.^[3]
• Heterogamy (Ancient Greek ἕτερος heteros = "other, another" + γάμος gámos = "marriage") – in cell biology – is a synonym of anisogamy, involving differently sized male and female gametes produced by different sexes or mating types in a species.
• fertilization. In this case, embryo occurs without fertilization or without the presence of pollen. A special form of apogamia is when the embryo develops klijavo seed. It is the phenomenon called parthenogenesis. So, fruits contain seeds, which although not fertilized, maintaining viability. In this case the embryo or germ arises from unfertilized oocyte. This phenomenon is widespread example in nuts
  .