Tag: classification of bryophytes

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.

Antheridia (male sex organs) and archegonia (female sex organs) are multicellular, jacketed reproductive structures characteristic of bryophytes (such as mosses), pteridophytes, and gymnosperms. Spirogyra (a green alga), Mucor (a fungus), and Puccinia (a fungus) do not possess these complex, jacketed sex organs.

In Riccia, the sporophyte is extremely simple, consisting only of a capsule that remains permanently embedded within the tissue of the gametophytic thallus. Because it lacks any specialized dehiscence mechanism like elaters or peristome teeth, the spores are only released when the surrounding thallus and outer capsule wall decay and decompose.

In mosses like Funaria, stomata are present exclusively on the apophysis, which is the sterile basal region of the capsule. These stomata are considered primitive because they often consist of a single ring-like guard cell with a central pore, rather than two distinct kidney-shaped guard cells.

In Riccia, the sporophyte is the simplest among bryophytes, lacking a foot and seta. During its development, some of the sporogenous cells do not form spores but instead differentiate into sterile nurse cells (nutritive cells) that provide nourishment to the developing spores, while elaters are completely absent.

In the liverwort Riccia, the sex organs (antheridia and archegonia) develop on the dorsal surface of the thallus and become deeply embedded within cavities of the photosynthetic tissue as the thallus grows. In mosses and ferns, the sex organs are typically superficial or borne on specialized structures rather than being embedded deep within the vegetative thallus.