Affiliation:
1. Herzen State Pedagogical University of Russia
2. Komarov Botanical Institute of RAS
Abstract
The paper analyzes data on the processes occurring before and during fertilization in flowering plants. At the gametophyte stage, the gametes are formed from haploid microspores and megaspores. They are sperms, egg and central cell. The fusion of male and female gametes occurs after the pollen tube enters any synergid. One sperm fuses with the egg cell, and another from the same pollen tube joins with the central cell.
The angiosperms are likely to have four types of fertilization. These types differ in the degree of completion of syngamy. Premitotic and postmitotic types are characterized by complete syngamy, and androgamic and gynandrogamic types are inherent in incomplete syngamy. In this case, the behavior of the sperm nuclei is of great significance. They, as a rule, combine with the nuclei of female gametes (premitotic and postmitotic types), but the sperm nuclei can remain independent (gynandrogamic type) or a female nucleus is replaced by a male one (androgamic type). The premitotic type of fertilization follows the way in which the gamete protoplasts and nuclei are united before the mitosis in the zygote nucleus. As for the postmitotic type, it is carried out on a completely different basis. It is possible that in angiosperms the chromosomes of sperm and egg cell do not unite during mitosis. They further divide independently, and a diploid set of chromosomes arises in a 2-celled embryo.
Publisher
The Russian Academy of Sciences
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