XVI International Botanical Congess

Fertilization is an essential process in sexual reproduction, involving the union of two specialized haploid cells, the gametes, to give a diploid cell, the zygote, which then develops to form a new organism. In flowering plants or Angiosperms the fertilization mechanism is unique because two simultaneous fertilization phenomena occur. Such a unique phenomenon discovered one century ago remains still obscure even some progresses have been reported during the last few years. Firstly, in vitro fertilization methods in a broad sense have been developed in flowering plants, such as the in vitro pollination of isolated female flowers or ovules and the in vitro fertilization of isolated embryo sacs. Secondly, in vitro fusions of completely isolated gametes, i.e., in vitro fertilizations in a strict sense, have been achieved. It leads to true zygote formation and regeneration of fertile plants is feasible. This review focuses on maize studies with successively: in vitro pollination, in vitro manipulation of the embryo sac, then, in vitro fusion of isolated gametes and culture of zygotes. The micromanipulation and in vitro culture gametophytes open new research avenues to analyse fertilization as well as natural or experimental embryogeneses.