Reproduction in Psilotum

Questions and Answers

What are the two main types of structures found in antheridia?

Outer jacket cells and inner primary androgonial cells.

How do the rhizoids in gametophytes differ in structure?

They are long, unicellular, and brownish in appearance.

What role do mucilagenous contents in neck cells serve during fertilization?

They facilitate the free passage for the entry of antherozoids.

What is the significance of apical meristem in gametophyte growth?

Apical meristem allows vertical growth and differentiation of the gametophyte. Signup and view all the answers

What initiates the fertilization process in archegonia?

The union of multiflagellate sperm with the egg occurs in the presence of water. Signup and view all the answers

Describe the first division that occurs in the diploid zygote.

The first division is a transverse division producing an outer epibasal cell. Signup and view all the answers

What are the main features of the appendages of P.nudum?

The appendages of P.nudum are small scale-like structures, internal photosynthetic parenchymatous cells, lack stomata, and have no vascular traces. Signup and view all the answers

What type of sporangium development is observed in Psilotum?

Eusporangiate type. Signup and view all the answers

In what form does the embryo develop in sporophytic generation?

The embryo develops outward towards the neck of the archegonium. Signup and view all the answers

Describe the role of gemmae in the vegetative reproduction of Psilotum.

Gemmae are small, multicellular ovoid structures that develop on the rhizome or prothallus, which detach and can germinate to form new shoots or prothalli. Signup and view all the answers

Describe the structure and function of spores produced by Psilotum.

The spores are homosporous, kidney-shaped, colorless, and undergo meiosis. Signup and view all the answers

What is the structure and function of synangia in Psilotum's reproductive process?

Synangia are trilocular, three-lobed structures that produce spores; each lobe corresponds to a sporangium. Signup and view all the answers

What happens to the primary neck canal cell during maturation of archegonia?

It undergoes a transverse division producing two neck canal nuclei. Signup and view all the answers

Explain the significance of having no vascular trace in the appendages of P.nudum.

The absence of vascular traces in the appendages suggests a specialized adaptation for minimal resource transport, focusing on photosynthesis. Signup and view all the answers

How do the vascular tissues develop in Psilotum?

Vascular tissues develop during the gametophytic generation. Signup and view all the answers

What is the significance of the cutinised peripheral cells in the gametophyte of Psilotum?

They enclose many-layered thin-walled parenchymatous cells. Signup and view all the answers

How does spore dehiscence occur in mature synangia?

At maturity, the synangium undergoes dehiscence, allowing for the release of spores from the sporangia. Signup and view all the answers

Explain the reproductive method of Psilotum.

Psilotum reproduces through monoecious gametophytes with both antheridia and archegonia. Signup and view all the answers

What type of division occurs in the development of the sporangial wall in Psilotum?

Periclinal division. Signup and view all the answers

In what environment does the mature gametophyte of Psilotum grow?

It grows as a saprophyte with an associated fungus. Signup and view all the answers

What basic morphological characteristic defines the mature gametophyte of Psilotum?

It is brown and cylindrical. Signup and view all the answers

Study Notes

Reproduction in Psilotum

Type of Sporangium Development: EUSPORANGIATE; sporangium develops from superficial initial cells.
Initial Cell Division: Periclinal division produces primary wall initials and sporogenous cells.
Sporangial Structure: Comprised of 4-5 layers forming the sporangial wall and sporogenous tissue, containing spore mother cells.
Spore Characteristics: Homosporous, bilaterally symmetrical, colorless, and kidney-shaped spores produced through meiosis.

Gametophyte Characteristics

Internal Structure: Cross-section reveals cutinised peripheral cells and many-layered thin-walled parenchymatous cells.
Symbiotic Relationship: Internal parenchyma filled with hyphae of a symbiotic fungus; unique among plants as vascular tissues develop in the gametophytic generation.
Mature Gametophyte: Brown, cylindrical, subterranean with dichotomous branching and surface-long unicellular brownish rhizoids.
Growth: Gametophyte develops through apical meristem and grows as a saprophyte with an associated fungus.
Sexuality: Monoecious (homothallic) with sex organs (antheridia and archegonia) located on the surface, more antheridia than archegonia.

Antheridium Structure

Cell Layers: Composed of outer jacket initial and inner primary androgonial cells.
Projection: Antheridium extends above the prothallus surface; mass of androgonial cells (androcytes) spirally coiled.
Sperm Release: Antherozoids escape through disintegrating opercular cells.

Archegonium Structure

Cell Composition: Developed from outer primary cover and inner central cells. The neck contains 4-6 vertical rows of cells.
Neck Cell Characteristics: Lower tier has thickened, cutinized walls; apical tier breaks in the presence of water to release mucilagenous contents.
Fertilization Process: Allows entry of multiflagellate antherozoids, leading to formation of a diploid zygote from sperm and egg union.

Embryo Development

Zygote Characteristics: Diploid zygote becomes the sporophytic generation; first division leads to the outer epibasial cell.
Embryogeny Type: Exoscopic mode of development where the shoot-forming apical cell directs outward towards the archegonium's neck.
Structure of Embryo: Composed of small scale-like structures on the upper aerial system; internal parenchymatous photosynthetic cells, surrounded by cutinised epidermis, and lacking stomata and vascular traces.

Modes of Reproduction

Vegetative Reproduction: Occurs in both sporophyte and gametophyte through gemmae formation; gemmae are small, multicellular, and develop on rhizomes or prothallus.
Post-germination: Detached gemmae from sporophyte can form subterranean shoots; gemmae from prothallus form new prothalli upon germination.
Spores and Sporangia: Aerial shoots develop dichotomously into trilocular sporangia known as synangia; each lobe corresponds to a sporangium, located at the tip of a short axis and measuring 1-2 mm in diameter.
Dehiscence: Mature synangium exhibits dehiscence, releasing spores.

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Description

This quiz explores the reproductive structures of Psilotum, focusing on the development of eusporangiate sporangia. It covers concepts such as superficial initial cells and periclinal division critical to the understanding of this plant's reproductive process.