Question

Compare the internal structure of sporophyte of riccia and marchantia

Answer 1

Answer:

Comparison # Riccia:

(A) The Gametophyte:

1. Plant is rosette-like dorsiventral flat, green thallus with dichotomous branching and attached to the substra­tum by scalar and rhi­zoids (both smooth and pegged).

2. Air-pores and air chambers present, the latter occur between vertical rows of cells containing chlorophyll.

3. Sex organs usually homothallic.

4. Antheridia develop singly within apex anth­eridial chambers em­bedded into the dorsal surface of the thallus.

5. Each antheridium is shortly stalked, surroun­ded by a jacket of single layer of cells and con­tains sperm mother cells, each of which gives rise to a biflagellate sperm.

6. Archegonia are deep­ly embedded into the thallus, when mature they are shortly stalked and flask-shaped; the neck consists of row of neck canal cells, ven­ter with a ventral canal cell and a large egg.

(B) The Sporophyte:

1. Zygote divides by a transverse wall forming a two-celled embryo.

2. Sporogonium is very simple erect and embed­ded into the thallus. It is not differentiated into foot, seta, stem and cap­sule, and is surrounded by a jacket of one layer of cells.

3. Absence of columella.

4. Sporogenous tissue is differentiated into spores only.

5. Sporophyte is completely dependent on the gametophyte for nutrition.

Comparison # Marchantia:

(A) The Gametophyte:

1. Plant is dorsiventral, prostately, flat thallus with prominent midrib and dichotomous bran­ching, and attached to the substratum, by scales and rhizoids (both smoo­th and pegged).

2. Air-pores present on the dorsal surface, lead into large air chambers containing filamentous chloroplasts.

3. Sex organs are usually heterothallic.

4. Antheridium deve­lops in groups on the upper surface of the lobes of antheridiophores and remains inside the antheridial chambers and arranged in centrifugal order.

5. Same as in Riccia.

6. Archegonia develop on the upper surface of the lobes of archegoniophores and later on when inserted they are arranged in centripetal order; the structure of archegonium is similar as in Riccia.

(B) The Sporophyte:

1. Zygote divides by transverse and longitudinal wall forming a four-celled embryo.

2. Sporogonium is a complex structure, inves­ted and is surrounded by pseudo-perianth and calyptra. It is differen­tiated into foot, seta and capsule and has a jacket of one layer of cells.

3. Absence of columella.

4. Sporogenous tissue is differentiated into spores and elaters.

5. Same as in Riccia.

Comparison # Anthoceros:

(A) The Gametophyte:

1. Plant is lobed, dor­siventral green thallus with irregular branch­ing and attached to the substratum by rhizoids only.

2. No air-pores or air chambers present, the cells on the dorsal surface contain large chloroplasts and prominent pyrenoids, on the ventral sur­face slits are present which has been Nostoc.

3. Sex organs are homothallic.

4. Antheridia develop in clusters (4-6) within, antheridial chambers deeply embedded into the dorsal surface of the thallus.

5. Same as in Riccia, but each antheridium is long-stalked.

6. Archegonia develop singly on the dorsal sur­face of the thallus and almost embedded into it; the neck consists of 4-6 neck canal cells, venter with a ventral canal cell and an egg.

(B) The Sporophyte:

1. Zygote divides by three successive walls for forming an eight-celled embryos.

2. Sporogonium is also complex structure, erect and arises from the up­per surface of the thal­lus. It is differentiated into foot and capsule only and surrounded by a jacket of 4-6 layers of cells. The capsule is meristematic, green and possesses stomato on the epidermis, and enclosed by a sheath at the base.

3. Presence of colu­mella in the capsule.

4. Same as in Marchantia.

5. Sporophyte is partly dependent on the gametophyte for nutrition

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