Question

Gametophyte is a dominant phase in the life cycle of a bryophyte. Explain.

Answer 1

Introduction:

The life cycle of bryophytes is haplo-diplontic and divided into two stages:

• Gametophytic phase
• Sporophytic phase

Gametophytic phase:

The gametophytic phase is dominant.

• It is haploid, long-lived, photosynthetic and independent.
• It is in the form of thalloid (thallus like structure) or leafy shoot with a central stem and leaf-like appendages.
• The roots are not developed, they are present in the form of thread-like rhizoids.
• The male gametophyte (thallus) contains the male sex organs (antheridium) and female gametophyte contains the female sex organs (archegonium).
• Antheridium gives rise to biflagellate antherozoids while archegonium gives rise to the egg by mitosis. The fusion of gametes form the zygote (diploid phase).
• The zygote gives rise to the sporophyte.

Sporophytic phase:

The sporophytic phase formed from the zygote is diploid and short-lived. It is dependent on the photosynthetic gametophyte and gets retained there. It produces haploid spores by meiosis that then germinates to form gametophytes.