Question

Why is dikaryon phase not present in Phycomycetes?​

Answer 1

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Sexual reproduction in Fungus involves the formation and the union of two gametes or their nuclei. Sexual reproduction is absent in the artificial group of fungi called Fungi imperfecti or Deuteromycetes. Depending upon the compatibility in sexual reproduction, fungi are of two types_ Homothallic and Heterothallic.

In Heterothallic forms sexual reproduction involves fusion between two genetically different mating types. In Homothallic forms fusion occurs between genetically similar types. Fusion involves the union of cytoplasms as well as nuclei. The former is called Plasmogamy while the latter is called Karyogamy.

In higher fungi, karyogamy is delayed and occurs just before meiosis. In the stage intervening between plasmogamy and karyogamy the cells often contain two nuclei or Dikaryons (n+n). Such cells are called dikaryotic cells. The phase is known as Dikaryophase which takes place in Ascomycetes and Basidiomycetes.

In such fungi life cycle is completed in three phases instead of two_ Haplophase, Dikaryophase and Diplophase (2n). Meiosis occurs in diplophase.

Answer 2

In Phycomycetes, the plasmogamy is immediately followed by karyogamy. There is no intermediate dikaryon phase

• Phycomycetes are lower-order fungi.
• Dikaryon phase is an intermediate phase in the sexual reproduction of certain fungi, but not all fungi
• In normal sexual reproduction of fungi the order will be plasmogamy. dikaryon phase and karyogamy.
• But in Phycomycetes without any delay karyogamy follows plasmogamy.
• So no intermediate dikaryon phase is involved.
• #SPJ3