Botany and Plant Science

Bryophytes are gametophyte dominant, meaning that the more prominent, longer-lived plant is the haploid gametophyte. The diploid sporophytes appear only occasionally and remain attached to and nutritionally dependent on the gametophyte.

In the life cycle of mosses, haploid spores germinate to produce a filamentous, creeping, green, and branched structure called a protonema. The leafy gametophyte, which represents the mature moss plant, then develops as a lateral bud from this protonema stage.

In the hornwort Anthoceros, the sex organs (antheridia and archegonia) are deeply embedded within the dorsal tissue of the gametophytic thallus. They develop from hypodermal cells and do not project outward on stalks or specialized gametophores, unlike in many liverworts.

Elaters are present in hepaticopsida (marchantia). Pseudoelators are present in Anthocerotopsida. Single layered capsule wall splits into a number of longitudinal valves, which extend from apex towards the middle of capsule. The valves are rolled back due to annular thickenings in jacket cells. Jerky movement of elaters due to their hygroscopic nature leads to loosening up of spore mass and scattering of spores in air.

In Anthoceros, the sporogenous tissue (archesporium) develops from the outer layer of the capsule, which is the amphithecium, surrounding the central columella. In contrast, the sporogenous tissue in Riccia and Marchantia is of endothecial origin.

Marchantia has a dioecious gametophyte. Dioecy is a characteristic of a species, meaning that it has distinct male and female individual organisms or colonies, meaning that a colony contains only either male or female individual. 

In liverworts, spores germinate directly to form the flat, thalloid gametophyte without forming an intermediate stage. In contrast, moss spores germinate to form a filamentous juvenile stage called a protonema.

Pteris (a pteridophyte), Anthoceros (a hornwort), and Funaria (a moss) all produce motile, flagellated male gametes (antherozoids) that require water for fertilization. Other groups like angiosperms (Hydrilla, Calotropis) produce non-flagellated male gametes.

Mosses are non-vascular plants and therefore lack true vascular tissues like xylem and phloem. Instead, conduction of water and nutrients is carried out by specialized parenchymatous cells, such as hydroids and leptoids.

In bryophytes like mosses and Riccia, the gametophyte is the dominant, independent, and photosynthetic phase of the life cycle. In pteridophytes (ferns), gymnosperms (Cycas), and angiosperms, the sporophyte is the dominant phase.

In Riccia, true elaters are completely absent. Instead, some of the potential spore mother cells do not undergo meiosis and instead degenerate to form sterile nurse cells, which provide nutrition to the developing spores.

Mosses are characterized by a leafy gametophore with stem-like and leaf-like structures, the complete absence of true vascular tissues, and a filamentous juvenile gametophyte stage called the protonema. Therefore, all the given statements are correct.

The sporophyte (sporogonium) of Riccia is the simplest among bryophytes, consisting solely of a capsule. It completely lacks a foot and a seta.

Since the sporophyte of Riccia consists only of a capsule and lacks a stalk (seta), it remains completely embedded within the tissue of the gametophytic thallus.