Tag: plant kingdom

The peristome, which lies immediately below the operculum consists of two sets of long, conical teeth, one within the other. The teeth of both the sets are on the same radii and thus opposite to each other. The tapering distal ends of the teeth of the outer set converge towards each other and are united terminally in a small central disc of tissue. The peristomial teeth are sculptured structures, that close the opening of the spore sac. They are attached at the base of the rim or diaphragm. The outer set of the peristomial teeth are hygroscopic and respond to the changes in humidity. The presence of peristomial teeth guarding the mouth of the theca region slows the rate of spore discharge.

The hygroscopic movement performed due to imbibition of water is called as hydrochasy. E.g., movement in the peristome of moss, elators in eqisetum. 

In Sphagnum, the stems themselves show a greater degree of internal complexity than most other mosses. The stem tissue can be divided into two regions, an inner pith (which may be subdivided into two layers) and an outer cortical layer of larger, usually dead cells. The pith is the site of food production and storage, which the cortical layer functions in water absorption and protection. Located in the cortical layer of many species are retort cells, so named, because they resemble the medieval chemical flasks called retorts. These cells are enlarged more than the surrounding cortical tissue, and have a pore, or opening, at one end. These cells are believed to help the moss retain water under intense sunlight, and they often are home to a wide variety of small invertebrates and other microorganisms.

Ferns and moss are both examples of 'primitive plants'. They have not developed all the specialised systems, that modern plants have, although ferns are more highly developed, than mosses. In mosses, sporophytes lack chlorophyll and depend on photosynthetic gametophyte for food, whereas, in ferns, sporophyte stage has true roots, stem and leaves and does not depend on gametophyte.

Capsule wall surrounds a wide air space. It is traversed by multicellular, narrow, uniseriate, green, elongated filamentous strands, known as trabeculae. Trabeculae connect the chlorenchymatous layer of wall with the spore sac.

Funaria possesses a juvenile filamentous autotrophic stage during life cycle, called as protonema. Moss plant (Funaria) develops on protonema as buds, while Marchantia is a liverwort in which distinct protonemal stage is absent.

Sphagnum that generally grows in bogs can absorb large amounts of water i.e., upto 18 times its weight. Therefore, it is extensively used by gardeners to keep seedlings and cut plant parts moist during transportation and propagation. In older times it was also used in place of absorbent cotton.

The gametophytic plant body of mosses are differentiated into prostate, branched filamentous, thalloid protonema and leafy erect gametophore.
Rhizoids are multicellular branched with oblique septa.
Sex organs develop from superficial cells at the apex of leafy gametophyte.
Stomata and chlorophyll are present in gametphyte for gaseous exchange, e.g., Funaria.