Funaria

Funaria is a genus of the funariaceae family which comes under division bryophyta. They are generally known as mosses. The family comprises about 200 species which are placed under 9 genera.

1.0Classification of Funaria

Kingdom: Plantae: Funaria belongs to the plant kingdom, consisting of multicellular, photosynthetic organisms characterized by cell walls containing cellulose.

Division : Bryophyta: Funaria is part of the division Bryophyta, which includes non-vascular plants. Bryophytes are characterized by their simple structure, lack of true roots, stems, and leaves, and their reliance on moisture for reproduction.

Class: Bryopsida: Funaria is a member of the class Bryopsida, a class of mosses known for their leafy structures and the presence of a seta (stalk) that supports the capsule where spores are produced.

Order: Funariales: Funaria belongs to the order Funariales, a taxonomic group of mosses.

Family: Funariaceae: Funaria is part of the Funariaceae family, which includes various moss species with similar characteristics.

Genus: Funaria: Funaria is a genus of mosses and is the namesake for the Funariaceae family. It contains species commonly known as cord-mosses or cordworts.

2.0General characteristics of Funaria

Funaria is commonly found in terrestrial habitats, it usually grows in moist shady places such as damp soil, shady banks. They are cosmopolitan, found everywhere from arctic to tropic regions. 

Gametophyte phase : This phase in the life cycle of funaria consists of two growth stages namely the Juvenile stage represented by primary protonema and the leafy stage which represents the leafy gametophyte. 

The adult gametophyte (haploid) is differentiated into rhizoids, axis or ‘stem’ and ‘leaves’. Rhizoids arise from the base of the axis. Axis or stem is green, erect, upright and branched, each branch arise below the leaf. Rhizoids are multicellular, branched with oblique septa which arise from the basal part of the stem which is brown. They perform some function of roots such as anchorage and absorption of water and solutes from the soil.

Leaves are sessile, oblong-ovate with entire margin, pointed apex and are arranged spirally on the branches and ‘stem’. Each ‘leaf’ is traversed by a single mid rib. Vascular bundles are absent in them. 

The gametophytic plant body of funaria is monecious, male (antheridium) and female archegonium) reproductive organs are borne on the same plant. Antheridia are borne on the main shoot of the plant. The female branch develops as a side shoot, which grows more vigorously and becomes longer than the male branches. Both antheridium and archegonium are borne on the top of branches respectively. 

3.0Reproduction in Funaria

The leafy gametophyte reproduces by means of vegetative reproduction and sexual reproduction. 

1. Vegetative reproduction :  

• Fragmentation of primary protonema : the primary protonema develops from the germination of spore. It is filamentous multicellular, the body of protonema usually breaks into several fragments, each fragment develops into the new adult gametophyte plant. 
• Secondary protonema : protonema develops from any part of plants other than the spores is called secondary protonema. Usually they are formed from any cell of a detached injured portion of stem, leaves or rhizoid. 
• Bulbils : these are the multicellular resting bud-like structures found on branches of rhizoids, when the conditions are suitable for growth they detach from the parental plants and produce protonema which further develops into the new plant. 
• Gemmae : these are the multicellular green bodies formed from the terminal cells of the protonema. They remain dormant throughout the unfavourable condition. However, on return of favourable conditions, a gemma detaches from the parent plant body and later germinates into a new plant.
• Apospory : Apospory is the condition in which the gametophyte is developed from the diploid (2n) sporophyte without the formation of spores. In case of funaria gametophytic  protonema develop from any unspecialized cells of the sporophyte. This protonema later gives rise to the gametophyte plant body. The gametophyte produced by apospory is normal in appearance but genetically it is diploid (2n). 

2. Sexual reproduction : Sexual reproduction in funaria takes place by the formation of antheridia and archegonia. Sex organs are developed in terminal clusters and develop on separate shoots of the same plant. Antheridia are borne on the main shoot of the plant and the female branch develops as a side shoot, which grows more vigorously and becomes longer than the male branches. This type of arrangement is autoecious.

• Antheridium : the antheridia are borne in clusters at the apex of the main axis. Cluster of antheridia is surrounded by leaves which are known as perigonial leaves. The antheridial cluster with surrounding perigonial leaves is called perigonium. A number of long multicellular hair-like filaments are also associated with the antheridia which is known as paraphysis; these filaments have large heads and usually have height of 4-6 cells.

• Structure of antheridium : Antheridium of Funaria is multicellular, elongated, club-shaped which is orange in coloured. The body has a jacket layer of cells, initially these cells contain chloroplast and which later change into chromoplast. The apical cell of the jacket differentiated into a cap-like structure operculum. Inside the antheridial wall there is a dense mass of cells that are androcyte. Each androcyte produce a single, biflagellated sperm. 
• Dehiscence of antheridium : The dehiscence of the mature antheridium only takes place in presence of water.

The opercular cell absorbs dew or rain water and swells up. The pressure thus created ruptures the inner wall and eventually a pore is formed at the distal end of the antheridium.

• Archegonia : The archegonia are borne in clusters at the apex of the archegonial branch. It arises from the base of male branch. Clusters of archegonia are surrounded by leaves which are known as perichaetial leaves. The archegonial cluster along with the perichaetial cluster is called perichaetium. 

Structure of archegonia : archegonium consists of a long stalk, a basal swollen venter and an elongated neck. The venter consists of a double layer of sterile cells which enclose a cavity known as the ventral cavity which contains an egg cell and a ventral canal cell. The elongated neck consists of 6-10 neck canal cells.

4.0Fertilization in Funaria

During fertilisation, the ventral canal cell and the neck canal cells of the archegonium disintegrate forming a mucilaginous substance. Latter absorbs water and swells up, creating pressure which breaks apart the terminal cell cover. The liberated antherozoids are now attracted chemotactically towards the archegonia. A large number of antherozoids enter the neck, but only one of them fuses with the egg nucleus to form the diploid zygote. The source of attraction is the cane sugar present in the slimy mass given out from open archegonial necks.

Sporophytic generation:

The sporophyte is formed from the zygote, it is diploid The zygote divides transversely to form an upper epibasal cell and a lower hypobasal cell. Both the hypobasal and epibasal cells divide repeatedly to form an young embryo with two growing points at the two opposite ends, each representing an apical cell with two cutting faces.

The epibasal cell gives rise to the capsule and the upper part of the seta, while the hypobasal cell forms the lower part of the seta and the foot.

Foot : The foot forms the basal portion of the sporophyte which is embedded in the apex of the archegonial branch. It functions as an anchorage and absorbing organ. 

Seta : It is a long, slender green in colour when it is young, but becomes reddish brown at maturity. Transverse of seta shows a single-layered epidermis, a central conducting strand of thin-walled cells (medulla) which is surrounded by a cortex made up of comparatively thick-walled cells. Seta helps in conduction of nutrients and water from gametophyte to capsule.

Capsule : The capsule is pear-shaped and green at first but later turns yellow. In the initial stages the capsule is covered with calyptra which is protective in nature.

Externally it shows three well marked regions. Each regions have distinct function these are as follows : 

1. Apophysis : it is the lowermost sterile part of the capsule which is photosynthetic in nature, due to this sporophyte of funaria is not fully dependent on the gametophyte for nutrition. Transverse section of apophysis shows an outer epidermal layer, where stomata occur for gaseous exchange, a middle cortex portion of chlorenchyma cells which is photosynthetic in nature, and central conductive strand.

2. Theca : it is the central zone of the capsule situated in between the apophysis and the operculum. Within the central region of theca a mass of parenchyma cells are present which is sterile and referred to as columella. This portion of the theca is surrounded by two elongated spore-sacs. 

3. Operculum or lid : cap-like portion of capsule is termed as operculum. It is 5-6 layers of cells in thickness. The innermost layer of the cells is 3-4 layers of cells that form the major portion of the operculum which is composed of small thin-walled cells of parenchyma. Initially the operculum is continuous with the theca and is separated by circular construction below this an  outer layer of 2-3 layers of thick-walled cells is present. These form a circular rim or diaphragm. Under the operculum lies the peristome. It consists of two rings of long triangular teeth, one within the other. The teeth are not cellular in nature and are made up of cuticle. Each ring of peristome possesses 16 teeth. The outer teeth and inner teeth are known as exostome and endostome respectively. It functions as dispersal of spores. 

5.0Dehiscence of capsule and spore dispersal

At maturity, the operculum, a lid-like structure at the tip of the capsule in Funaria moss, begins to desiccate due to limited water supply to the capsule. As a result, the thin-walled cells of the operculum, including the annulus—responsible for holding the operculum in place—shrink and dehydrate. Subsequently, the annulus ruptures, causing the release of the loosened operculum, exposing the peristome teeth. The exposed peristome, a ring of specialised teeth beneath the operculum, plays a vital role in spore dispersal.

The peristome teeth exhibit hygroscopic movements, reacting to changes in humidity levels. These movements are crucial in spore discharge. As environmental humidity varies, the peristome teeth respond by changing position, gradually opening and closing, thereby regulating the release of spores from the capsule. 

Germination of spores 

The haploid spore is the first gametophytic germination. The spore wall is differentiated into an outer wall exine and inner wall intine. Under the favourable conditions spore germinates. The exine is ruptured and the intine protrudes out as a germ tube. The germ tube elongates, becomes septate and produces a filamentous protonema. 

The protonema branches freely and forms two types of branches viz., chloronemal branches and rhizoidal branches. The chloronemal branches possess conspicuous chloroplasts in their cells and become green in colour.

The rhizoidal branches develop below the substratum, brown in colour and the partition walls are oblique to the lateral wall. The rhizoidal filaments are primarily meant for anchoring the protonema in the substratum.

6.0Life cycle of Funaria

Funaria hygrometrica is the most widespread species also known as “cord moss”, is a twisted seta that is extremely hygroscopic. It untwists when wet. Latin for “funis” means “a rope”.

7.0Multiple choice questions(MCQs)

Q.1 Sensor mechanism of spore dispersal is seen in

1. Fer                                 2. Funaria

3. Pinus                      4. Selaginella

Ans. (2) Funaria

Q.2 In Funaria, the peristomial teeth are

1. Xeric 2. Mesic

3. Hydric 4. Hygroscopic

Ans. (4) Hygroscopic

Q.3 In Funaria, the sporophytic phase is well-developed, comprising

1. Foot and capsule 2. Spore sac

3. Only capsule 4. Seta, foot and capsule

Ans. (4) Seta, foot, and capsule

Q.4 Gametophytic generation is dominant in

1. Funaria  2. Cycas

3. Selaginella 4. Mangifera

Ans. (1) Funaria 

Q.5 In Funaria, the leaves are arranged on the stem 

1. Spirally 2. Oppositely 

3. Alternately 4. Whorly

Ans. (1) Spirally