Tag: pictorial feature of plant kingdom

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.

In the fern Dryopteris, the sporangium wall has a specialized ring of cells with differentially thickened walls called the annulus. As the sporangium dries, the tension in the water inside the annulus cells causes them to contract, eventually tearing open the sporangium at the stomium to release the spores.

Option 'A' is correct

The gametophytic phase of Riccia begins with the haploid spore, which germinates to form the vegetative thallus. This thallus produces male and female gametes in the antheridia and archegonia, and their fusion (fertilization) results in the formation of a diploid zygote, which marks the end of the gametophytic phase.

In bryophytes like Riccia, the sporophyte is extremely simple, consisting only of a capsule embedded within the gametophytic thallus, completely lacking chlorophyll, a foot, or a seta. Consequently, it is entirely dependent on the gametophyte for nutrition, water, and physical protection. In contrast, pteridophytes and gymnosperms have dominant, independent sporophytes.

Polytrichum is a genus of mosses, and its sporogonium (sporophyte) is differentiated into three distinct regions: the foot (which anchors it to the gametophyte and absorbs nutrients), the seta (a long stalk), and the capsule (where spores are produced). This tripartite division is characteristic of advanced bryophyte sporophytes.