Dr. Malik| The life cycle of bryophytes and the alternation of generation in bryophytes

 

The life cycle of bryophytes and the alternation of generation in bryophytes 

First, we look at the alternation of generation in bryophyte.

Simply it is the existence of two different stages in the life cycle of any organism. These stages are the sporophyte stage and the gametophyte stage. In bryophytes, the main body is gametophyte.

Now, what is meant by the main body of Bryophyte?

The simple meaning of this sentence is main or long-time bryophytes live as gametophytes in nature or haploid in nature or the thallus of bryophyte produces gametes.

This gametophyte forms a sporophyte stage during its life cycle and the conversion of gametophyte to sporophyte or sporophyte to gametophyte is called alternation of generation.

Alternation of generation in bryophyte:

• The Gametophyte stage is the main stage in bryophytes.
• The sporophyte stage is dependent on gametophytes because it is short-lived while the gametophytic stage is long-lived in bryophytes.
• The Gametophyte stage is haploid while the sporophytic stage is diploid in nature.
• The gametophytic body produces gametes after mitosis. 
• The sporophyte body produces spores after meiosis.
• The Sporophyte stage develops a structure called the sporophyte. 
• This sporophyte is divided into three parts: 

1. Foot
2. Seta 
3. Capsule

• Spores are produced in the capsule after meiosis

The life cycle of bryophyte:

• Usually, bryophytes produce two types of gamete, one is small and motile, which is called a male gamete, while the other is large but non-motile which is called a female gamete.
• The male gamete is produced in a structure called antheridium while the female gamete is produced in a structure called archegonium.
• Both male and female gamete is haploid and produced by mitosis.
• Both gametes fuse and form a zygote, which is diploid.
• The zygote then further divided to form a structure called the sporophyte.
• This sporophyte can be divided into three parts i.e. foot, seta, and capsule.
• This sporophytic body is also diploid.
• The sporophyte is dependent on the gametophytic body.
• Spores are released from the capsule after meiosis and are haploid.
• These spores can form a new bryophyte.

 

Points to be remembered:

1. Main body of bryophyte is gametophyte.
2. The Gametophyte stage is always haploid.
3. Mitosis occurs at the gametophyte while meiosis takes place in the capsule of the sporophyte.
4. The sporophyte is always diploid.
5. Every single spore can form a new bryophyte.
6. Spores undergo mitosis to form a new thallus of bryophyte.
7. Water is very essential to complete its life cycle.