Model Answer
0 min readIntroduction
Bryophytes, including mosses like *Funaria*, represent a crucial evolutionary step between algae and vascular plants. They exhibit a distinct alternation of generations, with the gametophyte being the dominant phase. The antheridiophore is a specialized reproductive structure in *Funaria* responsible for producing and releasing antherozoids (male gametes). Understanding its morphology is fundamental to comprehending bryophyte reproduction. This answer will detail the longitudinal section of the antheridiophore, highlighting its key components and their roles in the sexual reproduction of *Funaria*.
Longitudinal Section of Antheridiophore of *Funaria*
The antheridiophore of *Funaria* is a stalk-like structure arising from the protonema. A longitudinal section reveals a distinct organization of tissues and reproductive structures. The following describes the key features, moving from the base to the apex:
1. Foot and Stalk (Seta)
The antheridiophore is connected to the protonema via a foot, which absorbs nutrients. Above the foot is the stalk (seta), a slender, cylindrical structure composed of elongated, colorless cells. The seta provides support and elevates the capsule (in this case, the antheridium) for better dispersal of antherozoids.
2. Antheridial Capsule
The apex of the seta swells to form the antheridial capsule. This is the main reproductive part. The capsule is generally ovoid or spherical.
3. Capsule Wall
The capsule wall is composed of a single layer of cells. These cells are relatively thin-walled and lack chloroplasts.
4. Antheridia
Embedded within the capsule are numerous antheridia. These are the male sex organs. Each antheridium is a globular or ovoid structure. A longitudinal section of an antheridium reveals:
- Antheridial Wall: A single layer of sterile cells surrounding the fertile cells.
- Androcytes: Numerous cells within the antheridium that undergo mitotic divisions to form antherozoids.
- Antherozoids: Multiflagellate, spirally coiled male gametes. They are released through an apical pore in the antheridium.
5. Operculum and Peristome Teeth (Absent in *Funaria* Antheridiophore)
Unlike the sporophyte capsule, the antheridial capsule of *Funaria* lacks an operculum and peristome teeth. The antherozoids are released directly through the rupture of the capsule wall.
6. Central Sterile Column
A central sterile column of elongated cells runs through the length of the capsule, providing support to the antheridia.
Diagrammatic Representation (Imagined by Examiner): A clear, labelled diagram would show the foot, seta, capsule, capsule wall, antheridia (with androcytes and antherozoids), and central sterile column. The relative positions and shapes of these structures should be accurately depicted.
Functional Significance
The antheridiophore’s structure is directly related to its function. The elevation of the antheridia via the seta facilitates the dispersal of antherozoids, which require water to swim to the archegonia (female sex organs) located on separate gametophytes. The numerous antheridia ensure a greater chance of successful fertilization.
| Component | Function |
|---|---|
| Foot | Anchorage and nutrient absorption |
| Seta | Support and elevation of capsule |
| Antheridial Capsule | Houses and protects antheridia |
| Antheridia | Produce and release antherozoids |
| Antherozoids | Male gametes; swim to archegonia for fertilization |
Conclusion
The antheridiophore of *Funaria* is a remarkably adapted structure for sexual reproduction in bryophytes. Its distinct components – the foot, seta, and antheridial capsule – work in concert to produce, protect, and release antherozoids, ensuring successful fertilization in a moist environment. Understanding the morphology and function of the antheridiophore is crucial for appreciating the evolutionary significance and reproductive strategies of bryophytes. Further research into the genetic control of antheridiophore development could provide insights into plant evolution.
Answer Length
This is a comprehensive model answer for learning purposes and may exceed the word limit. In the exam, always adhere to the prescribed word count.