Examine archegonia and antheridia of liverworts How do the positions of the arch

Question

Examine archegonia and antheridia of liverworts How do the positions of the archegonium and antheridium relate to their reproductive function? Examine archegonia and antheridia of mosses (Phylum Bryophyta). What is the difference between the archegonium and antheridium? Are sperm haploid or diploid? Examine ferns (Phylum Pterophyta). How does the size of the gametophyte compare with that of the sporophyte? In ferns, how is the role of the fern gametophyte different than that of the bryophytes? What key adaptations do vascular, seedless plants such as ferns have which allow them to be successful in habitats which bryophytes may not be?

Explanation / Answer

Marchantia is gametophytic, thalloid, flat, prostrate, 2-10 cm. long and dichotomously branched. A distinct m8drib is present in each branch of thallus which is marked on the dorsal surface by a shallow groove.

The dorsal.surface of thallus bears Velma cupsbalobg mid run. They are crescent shaped structures with smooth, spiny margins. These gemma cups bear gemma which help in vegetative propagation.

Each branch of thallus grows indefinitely by means of growing point situated at the apex of thallus in a groove called apical notch.

The central surface of thallus bears rhizoids and scales in both sides of the midrib.

Rumours are usually colorless and unicellular. They are of two types; smooth walled and tuberculate.

The main functions of the rhizoids are to anchor the thallus on the substratum and to absorb water and mineral nutrients from the soil.

Epidermal region, photosynthetic region and storage region.

Epidermal region; It includes upper amd lower epidermis. Upper epidermis forms protective covering above photosynthetic region. It is interuppted by many barrel shaped air pores that open internally into aur chambers. Pores are analogous to stomata but cells of pore wall do not control pore size like guard cells.

Photosynthetic region; Upper epidermis is followed by a large number of aur chambers which are separated by a single layered partition wall made up of 4-6 chloroplast contain8ng thin walled cells. Many simple or branches photosynthetic filaments arise from the floor of each chamber. Filaments are composed of chloroplasts containing cells.

Storage region; This region lies immediately below the photosynthetic region as a compact z9ne of several layers of polygonal cells. The cells of this region are devoid of chloroplasts and do not have intracellular space between them. Most of these cells contain starch or protein granules.

Rhizoids are short, more "root-like" in appearance. Hyphae are longer (usually), can travel along the surface of the substratum.

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