Bryophyte Reproductive Cycle    

We don't have time to review the Life Cycles for all of the plant Divisions we examined earlier. We will examine some typical Life Cycles of the most important taxa.

We are going to use the Moss Reproductive Cycle because these plants are rather familiar and because Hornworts (Anthocerophyta) and Liverworts (Hepatophyta) have similar Life Cycles!

All of these plants are Homosporous!

 
The Gametophyte is the Complex Photosynthetic Organism for Mosses (Bryophyta).

The Gametophytes are HAPLOID!!!!!!!!!

Moss Gametophytes have Leaf/Stem organization.

                                        
The Gametangia are formed at the apex of the stems which are called "Leafy Gametophores".

Male Plants produce Antheridia and tend to have an open, cup-shaped apex with reflexed Leaves. This forms a bowl-like structure.

     
Elongated Antheridia are produced in the Bowl.

  
These produce thousands of Motile Sperm.

The Sperm are ejected by rain drops and they can also swim away in thin films of water.

Stems that produce Archegonia have pointed apices because the leaves enclose the Archegonia.

       
Sperm must swim to the Archegonia. This requires free water.

When Sperm arrive at the Archegonia they swim down the
Neck Canal and Fertilize the Egg.

Consequently, Free Water (not bottled) must be available for sperm ejection and locomotion!

The ZYGOTE marks the start of the Diploid (Sporophyte) Generation!

      
The Zygote develops into an Embryo.

The Shoot Apex of the Embryo grows directly out of the Archegonial Neck (Exoscopic).

The Archegonial Neck grows to enclose the developing Sporophyte. This forms the Calyptra.

      The Sporophyte eventually causes the Calyptra to rupture but some of it is carried aloft by the elongating Sporophyte.

    
The Sporophyte may be green at first but it depends on photosynthate from the gametophyte in order to grow.

The Sporophyte eventually becomes tan/brown in color.

 The Sporophyte has 3 parts.

The Foot anchors the Sporophyte in the Gametophyte and it absorbs nutrients from the Gametophyte, and conveys them to the Sporophyte.

  
The Sporangium (Capsule) develops at the Apex of the Sporophyte.

    
Sporangia contain Sporogenous Cells which undergo MEIOSIS to produce Meiospores.

A Seta connects the Sporangium to the Foot.

Meiosis marks the start of the
Haploid Gametophyte Generation

  The Meiospores are Green.

    
They need light and water to germinate and grow. This creates a problem because sufficient light and water are not always present where spores land.  Moss spores do not have many adaptations that allow them to remain dormant and survive for long.
They must grow or perish!

Spore Germination produces a photosynthetic filament of cells called the Protonema (Proto = First & Nema = Thread).

  
Leafy Buds are produced by the Protonema as it Matures.

The Buds form the Leafy Gametophores which produce the Gametangia (Antheridia or Archegonia)

Moss Life Cycle