Funaria

Occurrence

Funaria is  terrestrial moss. It grows in the form of bright green velvety patches in shady and damp places. Genus Funaria is composed of 117 species. Funaria hygrometrica is most common and worldwide species. It grows well on burnt soil. It grows best in the presence of calcium, potassium, nitrogen and phosphorus.

Vegetative structure of gametophyte Structure of Thallus

Funaria plant is a gametophyte. Its plant body is composed of protonema and gametophore.

a)      Protonema: Protonema is a prostrate, green, branched filamentous structure. It gives rise to erect leafy shoots called gametophores. Protonema is short-lived.

b)      Gametophore: The adult plant consists of gametophores only. Each

a)  Protonema: Protonema is a prostrate, green, branched filamentous structure. It gives rise to erect leafy shoots called gametophores. Protonema is short-lived.

b)  Gametophore: The adult plant  consists of gametophores only. Each gametophores is differentiated into stem and leaves. They bear sex organs at their apices. Rh izoids arise from the base of each gametophores. Rhizoids anchor it into the soil. They absorb moisture and nutrients. The leaves are small, ovate, sessile and green. Leaves may be colourless or green.

• Colourless leaves are scale-like. They are found on prostrate branches and on lower portion of erect branches.
• Green leaves are larger in size. They are found on upper portion of an erect branch. These are called foliage leaves. They are spirally arranged.
• The leaves also surround sex organs. These leaves are larger in size and different in shape.

Internal Structure
Internal structure of stem
The stem has following internal structure:
1. Central cylinder: Central cylinder of stem is composed of two types of cells: leptoids and hydroids. Leptoids are elongated living cells. The hydroids are empty cells. Both these cells are Conducting in nature. The hydroids conduct water and the leptoids conduct food.

2. Cortex: Cortex is present outer to central cylinder. Cortex is composed Of many layers of thin-walled cells. The younger cells contain chloroplasts. The cortex contains leaf traces running from leaves to central cylinder.

3. Epidermis: A layer of epidermis present outer to the cortex. It is single layered thin walled cells. It is devoid of cuticle and stomata. It becomes double layered at certain places.

Structure of leaf

Leaf is composed of midrib and wings or lamina. Midrib is several celled thick. It is composed of elongate, thick-walled cells called stereids. The leaf lamina consists of a single layer of parenchyma. These cells contain chloroplasts in them. The chloroplast continuously divided again and again.

Reproduction in Gametophyte

Funaria gametophyte reproduces by vegetative and sexual reproductions.

Vegetative reproduction

It takes place by different ways:

a)   By decay: The prostrate branches die. Therefore, erect branches grow as independent plants.

b)   Gemmae formation: Small gemmae develop in groups along the midrib of leaves or at the tips of stem. Each gemma develops into a new plant.

c)   From fragmentation of protonema: A spore germinates into nrimary protonema. It breaks tip into fragments by death of cells. Each fragment develops into a new protonema. Each protonema form buds and give rise to gametophores.

d)   Apospory: In some cases, the sporophyte tissue is wounded. The wounded part produces a protonema. The buds develop on it and each bud grows into a diploid gametophore. It is called anosdory.

Sexual Reproduction

Funaria is monoecious. The sex organs, antheridia and archegonia develop at the apices of separate erect branches. These branches are called gametophores. The sex organs are intermingle4 with paraphyses. The paraphyses are 4-6 cellshigh and one cell wide sterile hairs. The paraphyses cells contain chloroplasts. The apical cell of each paraphyses is globose. Paraphyses meet over an antheridium to protect it. The paraphyses also hold water by capillarity action. So they prevent desiccation.

Male Branch

The leafy gametophore bearing antheridia is called male branch. Antheridia develop in group at the convex-shaped apex of a male bratich. The antheridia are intermingled with paraphyses. Antheridia are also surrounded by specialized leaves called perichaetal leaves. Perichaetal leaves form an envelope known as perichaetium.

Structure and Development of Antheridium

Structure: A mature antheridium is club-shaped. It borne on a stalk. The main body contains a mass of spermatogenesis cells. These cells are surrounded by a layer of jacket cells. The free distal end of the antheridium is differentiated into a caplike structure called operculum. It helps in dehiscence.

Development

1. Each antheridium develops from a superficial cell of apex. It becomes papillate. It divides to form an outer and an inner cell.

2. The inner cell gives rise to lower embedded part of the stalk. The outer cell divides by transverse divisions to produce a filament of 2-3 cells. The terminal cell of the filament differentiates into apical cell. It has two cutting faces.

3. The terminal cell of the filament cuts off 5-15 segments arranged in two rows. A segment, 2-3 cells away from the apical cell, divides. It forms a smaller jacket initial and a larger primary spermatogenous cell. Primary spermatogenous cell cuts off a second jacket initial.

4. The jacket initials divide anticlinally to a single layered jacket. The primary spermatogenous cell undergoes repeated divisions to produce sperm mother cells. Each sperm mother cell metamorphosed into a biflagellate male sperm. The apical cell itself changes into operculum.

Female Branch

The gametophore bearing archegonia is called female branch. It arises from the base of male branch. The apex of the branch flattens into a receptacle. Archegonia develop in clusters on this receptacle. These archegonia are intermingled with paraphyses.

Structure and Development of Archegonium

Structure: A mature archegonium is flask-shaped. It is borne on short stalk. It has a basal swollen part called venter, and elongated neck. The venter is surrounded by a two-layered jacket. But the jacket around the neck is single layered.

Development: Archegonium develops from an apical cell. This cell has two cutting faces.

I . The apical cell cuts off 4- 8 segments. They develop into stalk.

2. Afterwards the apical cell becomes three sided. It cuts off three peripheral cells. Apical cell itself becomes an axial cell. The peripheral cells surround the axial cell.

3. The peripheral cells divide to form jacket initials. These initials divide to form jacket layers around the venter and neck. The axial cell divides to form primary cover cell and central cell.

4. The central cell divides to form primary canal cell. It gives rise to neck canal cells and venter cell.

5. The venter cell divides to produce venter canal cell and an egg.

Fertilization and Post-Fertilization Changes

a)     Formation of zygote: Rain water or dew drops collect at the apical end of the male branch. It causes dehiscence of antheridium. The jacket cells imbibe water and split open at operculum. Thus a pore is formed. The male sperms move out in a mass. At the same time neck canal cells and venter canal cell disintegrate to form mucilage. This mucilage absorbs moisture, swell up. It forces disintegration of apical cells of the neck. The male sperms are attracted chemotactically. It swims towards archegonium. It enters into it and fertilizes the egg to form the zygote.

b)     Formation of calyptra: The zygote enlarges in size. It fills up the venter and secretes a thick wall around it. The stimulus of fertilization initiates divisions in the cells of venter. Thus venter form protective sheath called calyptra. Calyptra surrounds the developing sporogonium.

Sporogonium or sporophyte

The sporophyte in Funaria is commonly called sporogonium. Spores are produced in it asexually. Meiosis takes place before spare formation.

Structure of Sporogonium

A mature sporogonium is borne at the end of a female branch. It is differentiated into a massive foot, a long seta, and a pear-shaped capsule.

1.  The foot is embedded in the apical tissue of female branch. It absorbs water and nutrients from the gametophyte.

2. The seta is a long stalk. It carries capsule at its apex.

3. The capsule is pear-shaped highly organized spore-producing structure. The young capsule is green. But later it becomes dark brov.R. The apical part of the capsule is covered with remains of ruptured calyptra. The capsule has considerable differentiation of :issues.

Internal Structure of Sporogonium

The foot is bulbous mass of tissue. It gives rise to seta. The seta consists of central conducting strand. These strands are composed of thin-walled cells. These cells are surrounded by cortex and epidermis. The epidermis is covered with cuticle.

The capsule is differentiated into three regions, the aophysis, theca and operculum.

Apophysis: Apophysis is slightly swollen basal sterile region of the capsule. Its wall consists of epidermis that contains stomata. Beneath it is photosynthetic spongy layer. It is formed of parenchyma cells. These cells have intercellular spaces. Strand of thin-walled, vertically elongated cells is present in the center. These cells are conducting in nature.

a) Theca: It is central part of the capsule. It consists of following parts:

• It has sterile central column of tissue called columella.
• The columelta is surrounded by barrel-shaped spore sac The spore sac contains spore mother cells.
• • A wide air space is present outer to spore sac. This air space is traversed by transverse strands called trabeculae. These trabeculae connect the capsule wall with the wall of the spore sac.
  • The wall of the theca consists of epidermis, hypodelmis and two cells thick photosynthetic spongy layer.

  b) Operculum: The operculum is conical cap-like terminal region of the capsule. It consists of 3-4 layers of thin-walled cells. These cells are covered with epidermis.

  • Immediately below the operculum is peristome. Peristome is a ring of tooth-like segments. It is double. Thus it consists of 16 long, incurved teeth and 16 thin-walled inner segments. The peristome is attached to a ring of thin-walled cells. These cells form rim of the capsule. The peristome teeth are hygroscopic. They respond to slight changes in humidity.
  • The region of capsule above the theca consists of 4-5 layers of epidermal cells. The lower two layers of cells are thin-walled. They form annulus. The degeneration of annulus cells cause dropping off of operculum.

  Development of Sporogonium

  1.  The zygote enlarges. It divides by a transverse division into an upper epibasal and a lower hypobasal cell.
  2.  Both epibasal and hypobasal cells divide by two oblique divisions. They produce two apical cells. The segments cut off from upper apical cells form capsule and upper part of the seta. The segments cut off from lower apical cell develop into lower part of seta and foot.
  3.  The segments cut off by upper apical cell divide vertically. It appears as a quadrant in transverse section. A vertical wall perpendicular to an inner cell is formed. It forms a triangular and a rectangular cell in each quadrant.
  4. The four rectangular cells divide by a periclinal wall to produce endothecium and amphithecium. Endothecium is 4-celled. It is surrounded by an 8-celled amphithecium. These layers act as fundamental embryonic layers of the sporogonium.
  5.  Endothecium: In the theca region of the capsule, the endothecium cell divides first by a curved vertical wall. It separates a triangular and a rectangular cell. Then periclinal wall produce four central cells and a ring of eight peripheral cells.

  • The central cells divide and differentiate into central columella.
  • The peripheral cells divide periclinally into an outer layer and an inner layer. The cells of outer layer divide repeatedly to form sporogenous tissue (archesporium).
  • The cells of inner layer give rise to inner spore sac.
    

    Development of Sporogonium

    The cells of amphithecium divide periclinally. They form outer and inner layers of eight cells each.

    • The inner layer is called first ring. Its cells divide and mature into outer spore sac.
    • The cells of outer layer divide anticlinally first and then periclinally. They produce an inner 16-celled second ring. These cells give rise to trabeculae.
    • The cells outer to second ring divides again anticlinally and periclinally. I hey produce a 32-celled inner third ring. The cells of this layer differentiate into spongy layer.The cells external to third ring divide periclinally to separate fourth and fifth rings. Each ring is 32-celled. The cells of these rings differentiate into hypodermis and epidermis.Dehiscence of Capsule and Dispersal of Spores

      After development, the capsule starts ripening. The thin-walled operculum cells below the epidermis and at the base of annulus become dry. They start shrinking. It loosens the connection between operculum and underlying tissue. Finally the operculum is shed It exposes the peristome. Teeth of the peristome peristome regulate the dispersal of spores.

      Germination of Spores and Development of Protonema

      The spore shed from the capsule and it start germination. The spore increases in size and the outer spore wall ruptures. The inner spore wall grows out. It forms one or two germ tubes. A cross wall is formed near its point of emergence. It separates the germ tube from the spore. The cell cut off soon develops into a branched multicellular filament, the protonema.

      A protonema is differentiated into two kinds of branches:

      a)        C’hloroneina: It grows along the surface of the substratum or into the air.

      b)        Rhizoids: They penetrate into the substratum.

      The chloronemal stage grows extensively. After 20 days, most of the cells of chloronema degenerate. Only a few apical cells are left. These cells give rise to another type of filaments, the caulonema. Buds develop on the caulonema filaments. This bud gives rise to gametophores.