It involves formation of haploid gametes which fuse to form a diploid Zygote. Meiosis occurs during germination Zygote and the resultant new plant is a haploid gametophyte. Based on the size and movement of gametes, following types of sexual reproduction have been recognised.
In this type, either both gametes or at least one is flagellated and. therefore, motile. Plasmogamy is of following types…
Both the motile gametes are Similar in shape, size and structure, i.e., they are morphologically similar, e.g., Ulothrix, etc. However, in most of the isogametes male is more active than the female. Thus ,gametes which are morphologically similar are generally physiologically anisogamous. Both the gametes are
flagellated and motile. The male gamete is smaller in size and invariably more active than the female e.g., Caulerpa, etc.
The male gamete is smaller and flagellated while the female gamete 1s larger and non-flagellated and thus passive. The male and female gametes are produced in specialised structures called antheridia and oogonia respectively. Oogamy is found in Oedogonium, Vaucheria, etc.
Most of the algae reproduce by flagellated gametes (planogametes). However,in some algae like Spirogyra, diatoms, etc., Gametes lack flagella and are called aplanogametes. Such gametes fuse by a special process called conjugation.