What is the Difference Between Marchantia and Riccia

The main difference between Marchantia and Riccia is that Marchantia contains a dorsiventral, prostrate flat with a prominent midrib and dichotomous branching whereas Riccia is rosette-like, dorsiventral flat, green thallus with dichotomous branching. Furthermore, the sex organs of Marchantia are heterothallic while the sex organs of Riccia are homothallic. 

Marchantia and Riccia are two genera of the order Marchantiales under the division Marchantiophyta or liverworts. Generally, liverworts are one of the three representative groups of the phylum Bryophyta. 

Key Areas Covered 

1. What is Marchantia
     – Definition, Taxonomy, Structure
2. What is Riccia
     – Definition, Taxonomy, Structure
3. What are the Similarities Between Marchantia and Riccia
     – Outline of Common Features
4. What is the Difference Between Marchantia and Riccia
     – Comparison of Key Differences

Key Terms 

Gametophyte, Gemma Cup, Marchantia, Riccia, Sporophyte, Thallus

What is Marchantia 

Marchantia is a genus of liverworts characterized by the presence of tiny, cup-like structures known as gemma cups. These gemma cups are used for asexual reproduction. Another characteristic feature of this genus is the combination of the barrel-shaped pores. The third characteristic feature of the genus is the differentiation of the plant body into two cell layers. Here, the upper cell layer is photosynthetic, while the lower cell layer serves as a storage layer. Moreover, the upper layer consists of a well-defined upper epidermis with pores.

Figure 1: Marchantia

Furthermore, the plant body of Marchantia is a thallose. On the ventral surface of the thallose, a multicellular, purple colored scales occur with a single-cell thickness. Furthermore, the ventral surface contains unicellular rhizoids. On the other hand, the development of sex organs and sporophyte occur on the dorsal surface. 

What is Riccia 

Riccia is another genus of liverworts. Its plant body is a thallose, and it is not differentiated into stem, leaves, and roots. Generally, it produces a small thallus, which can be about 0.5 to 4 mm wide. Further, the thallus can be strap-shaped. It may contain dichotomous branches, form rosettes or hemirosettes. 

Figure 2: Riccia

Moreover, the thallus of Riccia is dorsoventrally differentiated. Here, the upper or the dorsal surface of the thallus contains chlorophyll; hence, it is green in color. The surface contains mid-dorsal, longitudinal grooves. Occasionally, air pores break through the dorsal surface. Furthermore, the lower or the ventral surface contains a mid-ventral ridge with multicellular scales. These scales also contain anthocyanin and have a purple color.  

Similarities Between Marchantia and Riccia 

• Marchantia and Riccia are two genera of liverworts. 
• Both belong to the order Marchantiales under the division Marchantiophyta. 
• Generally, they undergo an alteration of generations with sporophytic and gametophytic stages. 
• The gametophyte is the dominant stage of life of both genera. 
• Also, their plant body is a thallose and it is not differentiated into the stem, roots, and leaves. 
• Moreover, the cells of the thallus have chlorophyll and undergo photosynthesis. 
• Their thallus is liver-like. It is prostrate and dichotomously branched. 
• Additionally, the root-like rhizoids attach the plant to the substrate. 
• However, they are non-vascular, non-flowering, and spore-producing plants. 
• Besides, both undergo both sexual and asexual reproduction.  
• In addition, the gametophyte is responsible for the production of gametes. 
• Sex organs occur on the dorsal surface of the thallus. They are developed from the superficial cells. 
• Their antheridia are shortly stalked, surroun­ded by a jacket of a single layer of cells and con­tains sperm mother cells, each of which gives rise to a biflagellate sperm.  
• Their archegonia are shortly stalked and flask-shaped. 
• Fertilization of gametes gives rise to the zygote, which develops into the sporophyte. 
• Furthermore, the sporophyte partially depends on the gametophyte for nutrition, and it produces spores. 
• Their sporogonium is a complex structure. 

Difference Between Marchantia and Riccia 

Definition 

Marchantia refers to a genus of Marchantiaceae, comprising of liverworts, which reproduce asexually by gemmae and have stalked antheridiophores while Riccia refers to a genus of the family Ricciaceae resembling duckweed and characterized by a dichotomously branched thallus, which may be floating, submerged, or rooted on damp soil. 

Gametophyte Structure 

Marchantia contains a dorsiventral, prostrate flat with a prominent midrib and dichotomous branching while Riccia is rosette-like, dorsiventral flat, green thallus with dichotomous branching. Thus, this is the main difference between Marchantia and Riccia.

Air Pores 

Air pores occur in the dorsal surface of Marchantia, giving rise to large air chambers with filamentous chloroplasts while Riccia contains air pores and its air chambers occur between the vertical rows of cells with chlorophyll. 

Sex Organs 

Another difference between Marchantia and Riccia is their sex organs. The sex organs of Marchantia are heterothallic while the sex organs of Riccia are homothallic. 

Antheridia Development 

Besides, antheridium develops in groups on the upper surface of the lobes of antheridiophores in Marchantia, while individual antheridia develop within apex anth­eridial chambers in Riccia. 

Archegonia Development 

Archegonia are deep­ly embedded into the thallus in Marchantia while the archegonia develop on the upper surface of the lobes of archegoniophores in Riccia.  

Embryo 

The zygote of Marchantia gives rise to an eight-celled embryo while the zygote of Riccia gives rise to a four-celled embryo. 

Sporogonium Differentiation 

Moreover, the sporogonium of Marchantia is differentiated into foot and capsule while the sporogonium of Riccia is differentiated into the foot, seta, and capsule. 

Jackets of the Sporogonium 

The sporogonium of Marchantia is surrounded by a jacket of 4-6 cell layers while the sporogonium of Riccia is surrounded by a jacket of one layer of cells. Hence, this is another difference between Marchantia and Riccia.

Columella 

Furthermore, the capsule of the sporogonium of Marchantia contains a columella while the capsule of the sporogonium of Riccia lacks a columella. 

Conclusion 

Marchantia is a genus of liverworts with a thallose gametophyte, which is flat. Moreover, it produces heterothallic sex organs. On the other hand, Riccia is another genus of liverworts, which contains a rosette-like thallose. But, it produces homothallic sex organs. Both genera produce dichotomous branching. Furthermore, their prominent life stage is the gametophyte. However, the main difference between Marchantia and Riccia is the structure of gametophyte and sporophyte. 

References:

1. “Marchantia.” Encyclopædia Britannica, Encyclopædia Britannica, Inc., 7 Oct. 2016, Available Here.
2. “Riccia.” Encyclopædia Britannica, Encyclopædia Britannica, Inc., 17 July 2008, Available Here.

Image Courtesy:

1. “MarchantiaPolymorpha” (CC BY-SA 3.0) via Commons Wikimedia  
2. “Riccia huebeneriana Lindenb. Kohatakegoke” By Show_ryu – Own work (CC BY-SA 3.0) via Commons Wikimedia