Botany and Plant Science

Bryophytes are composed of true parenchyma derived from three-dimensional growth usually from an apical meristem. Stems in mosses are multicellular and can show a surprising amount of tissue differentiation depending on the species of moss. Typically,  most mosses have cortical cells (also called parenchyma cells) that compose much of the stem, and thick walled cells, for structural support.

In Mosses, column of cells running up the middle of the sterile jacket is called as columella.

The protonema is an elongate, thread-like structure that develops from the germinated spore of mosses. The protonemal stage is the best-studied part of bryophyte development. 

Moss gametophytes are either erect or extensively branched prostrate plants, that consist of an axis (commonly called a stem) bearing spirally arranged leaf-like appendages (usually referred to as leaves); more often than not, they are anchored to the substratum by branched multicellular filaments called rhizoids. The leafy shoot of mosses is haploid and thus part of the gametophyte generation. Liverworts and Hornworts have dorsiventrally flattened plant body. 

The zygote, which develops into the sporophyte, is formed and begins its development within the venter of the archegonium.

The capsule of the Funaria sporophyte contains an apophysis region which possesses stomata for gas exchange.

Funaria is both monoecious and autoecious. The antheridium (male sex organ) are born on different heads of the same plant. Hence, it is both autoecious and monoecious.

Sex organs in Funaria develop at the tip of gametophore since the plant itself constitutes the gametophytic phase. After fertilization develops the capsule from which protonema develops from the spores that dehisces from the capsule. The capsule constitutes the sporophytic phase. The plant shows an alternation of generation, between the sporophytic and gametophytic phase.

The mature sporophyte of Funaria is much more complex than that of the liverworts. It is differentiated into foot, seta and capsule. The foot forms the basal portion of sporophyte. The seta is a long cylinder reddish brown, stalk-like structure. It carries the capsule at its top and raises it more than an inch above the apex of the leafy gametophore.

Funaria is monoecious and autoecious i.e., male and female reproductive structures develop on different branches of the same plant. Monoecious means both male and female sex organs are borne on the same plant body.

The diploid sporophyte or sporogonium reproduces by spores and represents the asexual generation. The mature sporophyte of Funaria is differentiated into foot, seta and capsule. 

The life cycle of Funaria is haplo-diplontic type. In the life cycle free living haploid gametophyte alternates with a semiparastitic diploid sporogonium (Sporophyte). In this type alternation of generations is called as heteromorphic or heterologous. In Funaria the main plant body is free-living gametophyte (n) which exist in 2 forms i.e. protonema (juvenile gametophyte) and leafy gametophore (adult gametophyte). The leafy gametophyte is the dominant phase of Funaria as the vegetative body of itself is represented by these leafy gametophores. It has two distinct growth stages, a prostrate filamentous alga-like protonema and an upright gametophore.

Apophysis is the solid, somewhat swollen basal, green photosynthetic portion of the capsule. It is sterile in nature. It also helps in conduction of water and food materials. It gradually narrows down into seta; hence it is also called as the neck of the capsule. Internally the apophysis is covered by epidermis. In capsule of Funaria stomata present only in apophysis.

In Funaria, stomata are absent in leaf and is present in capsule (apophysis). Internally the apophysis is covered by epidermis. The epidermis is interrupted by stomata, which leads into air space below, called as the sub stomatal cavity. Within the epidermis is a broad spongy zone of sterile cells, rich in chloroplasts. There are distinct intercellular spaces between these cells. Stomata in present only in the apophysis, which is present at the basal part of the capsule.

The spores of Funaria are 12 - 20 microns in diameter, and represent the first cell of the gametophytic generation. The spore wall consists of two layers, the outer smooth and brown coloured exosporium, and the inner colourless endosporium. The cytoplasm of spore is rich in oil globules and chloroplasts. The spore germinates under favourble conditions. The exospore is ruptured and the endospore produces a papilla. It soon forms a long filamentous protonema. The protonema shows apical growth and forms two types of branches, the chloronemal branches and the rhizoidal branches.