The angiosperms are heterosporous. The microsporophyll (stamen) bears the microsporangia which produce the microspores. These are haploid cells produced as a result of meiosis. The microspores germinate to produce the microgametophyte which bears microgametangia in which the male gametes are produced. Similarly in the female side the sequence is megasporophyll (carpel) – megasporangium – megaspore (haploid)- megagametophyte – megagametangium –female gamete. During fertilization the male and female gametes fuse to form the diploid zygote which develops into the embryo. The embryo develops into the adult sporophyte.
1. It is meiotic formation of haploid microspores from diploid microspore mother cell.
2. The arrangement of microspores in a tetrad is generally tetrahedral.
3. All the four microspores of a spore tetrad are functional.
1. It is meiotic formation of haploid megaspore from diploid megaspore mother cell.
2. The arrangement of megaspores in a tetrad is commonly linear.
3.Only one megaspore of a spore tetrad remains functional, other three degenerate.