Tag: classification of bryophytes

Stomata in mosses are restricted to the sporophyte generation, specifically on the apophysis region of the capsule. The gametophytic structures like the stem and leaves lack stomata entirely. This localization helps in gas exchange and transpiration during the development of the capsule.

Riccia is a liverwort that possesses unicellular rhizoids of two distinct types: smooth-walled and tuberculate. Smooth-walled rhizoids have smooth inner walls, while tuberculate rhizoids have peg-like internal projections extending into the lumen. Multicellular rhizoids are characteristic of mosses, not liverworts like Riccia.

The stem (axis) of the Funaria gametophyte is covered by a single-layered epidermis. This epidermis lacks both a protective cuticle and stomata, which allows for direct absorption of water and gases. Stomata in Funaria are only found on the apophysis of the sporophytic capsule.

The archegonium of Riccia is a flask-shaped structure consisting of a neck and a swollen venter. The neck contains a row of 4 neck canal cells, while the venter contains a single venter canal cell and a single large egg cell (oosphere). This cellular composition is characteristic of many primitive bryophytes.

The protonema is a filamentous, branched, and multicellular green structure that develops from a germinating moss spore. Because of its photosynthetic nature and filamentous growth, it closely resembles a multicellular green alga. This structural similarity is often cited as evolutionary evidence linking bryophytes to green algae.

Paraphyses are sterile, multicellular, uniseriate hair-like structures found interspersed among the sex organs in the receptacles of mosses. They help in retaining water through capillary action and protect the developing sex organs from drying out. Apophysis and hypophysis, on the other hand, refer to parts of the sporophyte capsule.

The main, conspicuous, green leafy plant of a moss is the gametophyte, which represents the dominant haploid phase of its life cycle. The diploid sporophyte is physically dependent on the gametophyte and is only present temporarily for spore production.

Peristome teeth are specialized structures found at the mouth of the moss capsule. They are hygroscopic, meaning they bend outwards or inwards in response to changes in humidity, which actively aids in the gradual dispersal of spores. Other parts like the columella provide support, while the operculum acts as a lid.

The protonema is the juvenile, filamentous stage in the life cycle of a moss that develops directly from the germination of a spore. It eventually gives rise to the leafy gametophore (the adult moss plant) through the development of lateral buds. Prothallus is the gametophyte of pteridophytes, not mosses.

The columella is a central, sterile column of parenchymatous tissue found in the capsule of mosses. It provides structural support to the surrounding spore sac and helps in the conduction of water and nutrients to the developing spores.