Polysiphonia (Rhodophyta) | General Characteristics of Polysiphonia | Reproduction and Life cycle of Polysiphonia (Rhodophyta) |

 Polysiphonia

 (Rhodophyta)

 General Characteristics of Polysiphonia:

• Most of the species of Polysiphonia are lithophytes so they are mostly found on rocks. 
• Some of the species are epiphytic. It means that they can be grown on other plants and algae.
• Polysiphonia is a dioecious alga, which means both male and female sex organs are present in different organisms.
• The cell wall of Polysiphonia is composed of two layers. 
• The outer layer is made of pectin while the inner cell wall layer is made of cellulose. 
• The cell contains a large central vacuole which helps in the storage purposes. 
• The cytoplasm is present between the cell wall and the central vacuole. 
• The cell contains several red discoid chromatophores which lack pyrenoids.
• The chromatophores contain pigments like chlorophyll a, chlorophyll d, and carotene.

 Reproduction: 

The life cycle of Polysiphonia exhibits triphasic alternation of generation. In the life cycle, three distinct phases occur. These are:

1. Gametophytic phase
2. Carposporophyte phase
3. Tetra sporophyte phase 

• Both male and female organisms of Polysiphonia are haploid in nature means they produce haploid gametes.
• The haploid male gametophytic algae bears sex organs called spermatangia. 
• Spermatangia produce haploid spermatia. 
• The haploid female gametophytic algae bear the sex organ called Carpogonium. 
• Carpogonium produces haploid egg cells.
• Both haploid male and female gametes fuse and make fertilization between them and form a zygote which is diploid in nature.

• The zygote develops in the second phase of the life cycle. 
• The Carposporophyte is dependent upon female gametophytic algae. 
• The Carporophyte forms diploid carpospores inside the Carposporangia.
• The carpospores germinate to make diploid tetra sporophytic algae. 
• The tetra sporophytic alga bear tetra sporangia.
• The diploid tetra sporangial nucleus divides meiotically to form four haploid tetra spores which again make gametophytic male and female algae. 

In the life cycle of Polysiphonia two diploid phases Carposprophyte and tetra sporophyte alternate with one haploid gametophytic phase. 

The life cycle of Polysiphonia can be called a triphasic diplobiontic with isomorphic alternation of generation.