In the plants , and those algae that share with the first having alternation of generations heterophasic, called sporophyte phase to diploid multicellular, which produces by meiosis spores haploid (meiosporas), whose development derived haploid individuals called gametophytes .A sporophyte develops by cell proliferation (mitosis) from a zygote formed by fertilization , ie, the fusion of two gametes or sex cells haploid, arising in specialized organs called gametangia which develop on the gametophyte .The explant or explant is a living tissue removed from his own body and transferred to an artificial medium for growth . In the particular case of plant biotechnology , the explant is a small fragment of a plant that is cleaved and is prepared Aseptic for cultivation in a nutrient medium and which, therefore, functions as a generator of new plants through tissue culture in vitro .The fertilization or fertilization , also called syngamy , is the process by which two gametes fuse to create a new individual with a genome derived from both parents. The two main purposes of fertilization is the combination of genes derived from both parents and the generation of a new individual ( reproduction).In the case of seed plants , one must differentiate the phenomenon of fertilization itself (intimate union of two sex cells to their respective hubs confused and, to a greater or lesser degree, their cytoplasm), a biological process that precedes : the pollination , in which the grains of pollen , developed in librariescontaining each anther of a stamen (male reproductive sheet) are transported by wind or insects to the stigmas, where they germinate issuing a pollen tube that grows toward the ovary. In this case it is not gametes but spores , since each pollen grain contains two gametes or male reproductive cells, which are transported to a carpel (female reproductive sheet) of another flower (pollination) or the same flower.ProcessFertilization details are as diverse as the species, but there are four events that are constant in all of them:1. The first contact and recognition between egg and sperm , which in most cases is of great importance to ensure that the gametes are of the same species.2. Regulation of the interaction between sperm and the female gamete. Only a male gamete to fertilize a female gamete. This can be achieved by allowing only one sperm enters the egg, thus preventing the entry of others.3. The fusion of genetic material from both gametes4. The formation of the zygote and the beginning of its developmentAccording to the similarities and differences between the gametes? Isogamica fertilization: union of two gametes identical in size and structure, occurs only in some groups, such as protozoa .? Anisogamica Fertilization: Union of two different gametes, both in size and structure, one male and one female. Occur in most groups.? Ovogamica fertilization: gametes very different: the female is large and immobile and provides all the nutritional reserves to the zygote, while the male is small and mobile.