Occurrence l The genus Funaria comprises species. In India, it is represented by 15 species. The plants grow in dense mats over moist shady places, especially during rains. They show gregarious habit.
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Occurrence l The genus Funaria comprises species. In India, it is represented by 15 species. The plants grow in dense mats over moist shady places, especially during rains. They show gregarious habit. Morphology l The adult plant body is foliose, i.
It has cm height. The plant body is differentiated into root-like, stem-like and leaf-like structures, called rhizoid, cauloid and phylloid, respectively. The rhizoids are septae. The cauloid axis0 is aerial, erect, slender and monopodially branched.
They are ovate and distinguishable into midrib and lamina. There is no venation. Vegetative Reproduction l The primary protonema developed as a result of the spore germination multiplies vegetatively either by breaking up of branches or small terminal groups of cells, the-buds. Each such branch or the group of cells becomes separated by certain intercalary colourless cells and develops into a new plant.
In their function and behaviour they are similar to the primary protonema. Secondary protonema may be formed from any of the detached living part of the leafy gametophore such as from the axis, leaves, paraphysis and sex organs or form the rhizoids.
When developed from the wounded parts of the sporophyte such as from sterile cells of the capsule and seta, they exhibit a phenomenon of apospory. These detached secondary protonema form the new plant. The gemmae or tubers develop into new plants under favourable conditions. Sexual Reproduction l The plants are monoecious, autoecious and protandrous, i.
The sex organs are borne in terminal groups on the species of fertile branches, the gametophores. They are surrounded by a large number of closely set perigonial leaves spreading out like a rosette of petals and forming a perigonial cup that provides protection to the developing antheridia. Paraphyses l A large number of sterile structures, the paraphyses occur intermixed with the antheridia. They occur in clusters and are green.
Each paraphysis is multicellular, cells high, filaments structure i. The terminal cell of the paraphyses is large, nearly subspherical and capitate, but the cells below it are narrow, elongated and rich in chloroplasts. They hold water in between them and secrete mucilage that assists in the liberation of antherozoids and protects the young antheridia from drying.
Structure of mature antheridium l A mature antheridium consists of a short massive multicellular stalk on which lies a club-shaped antheridial body.
Within the jacket of the antheridium lies a mass of androcytes of which each later changes into a single biflagellate spermatozoid.
The opercular cell becomes mucilaginous, absorbs water and swells. It causes a pressure that ruptures its inner wall. Soon after the disorganisation of the outer wall, the opercular cell breaks its connections with the neighbouring cells and a narrow pore is formed.
As a result of contraction of the distended wall of the antheridium, a hydrostatic pressure is developed within the antheridial cavity causing androcytes to ooze out in the form of a viscous fluid that reaches the air-water interface within the perigonium. The androcytes separate and get metamorphosed into spermatozoids very soon as in Riccia and Anthoceros.
The protonema branches freely and forms the green filaments. The filaments, which are erect or very close to the substratum, develop thick colourless cell walls and cross walls at right angles to the lateral walls and below the substratum and away from the light develop brown thin cell walls, oblique cross walls and a few inconspicuous chloroplasts or leucoplasts. These are known as rhizoidal filaments and are primarily meant for fixing the protonema to the substratum.
The rhizoidal branches when exposed to light behave as chloronemal filaments. The formation of these two type of filaments depends on the environmental conditions in response to which the protonema is extremely plastic. On account of variability in the morphological and genetic behaviour caused under the influence of environmental factors, they do not exhibit and stabilized pattern of growth. Soon after the formation of the buds near a cross wall towards the base of the choloronemal branches or even on the rhizoidal branches the growth of protonema stops.
The buds after becoming celled develop the tetrahedral apical cell with three cutting faces and cut segment to form and three rows of leaves. The development of the rhizoids takes place from the base of the stem.
The gametophores are usually very large in number even in the protonema formed by the germination of a single spore, become independent as soon as the protonema dies off. The germination of a large number of spores develops several protonema intermingled due to which a large gametophores are developed. A dense growth of plants is seen because of this property. Click here for Test of the chapter. The leaves that enclose the group of archegonia and sterile paraphyses are similar to the ordinary foliage leaves.
The female shoot emerges laterally from the base of the male shoot and goes higher up. It is usually larger than the male shoot. Structure of archegonium l The massive multicellular stalk of the archegonium is comparatively larger than that of the antheridium. The jacket or wall of the archegonium in the region of the venter is two layered thick but in the region of the neck it is single layered thick.
The terminal cells cover cells separate apart and later are thrown off, thus a passage is left for the cavity within the archegonium. Fertilization l The antherozoids are attracted chemotatically. The antherozoids reach the archegonium by the agency of water perhaps by splashing and trickling of rain drops from male shoot to underlying female shoot. The antherozoids passing through the mucilage filled neck canal reach the egg containing venter cavity where finally one of them fuses with the egg nucleus and form and zygote.
The Sporophyte Structure of Mature Sporogonium l The mature sporophyte is a complex and highly elaborated structure differentiated into the foot, seta and capsule.
It functions both as an absorbing and anchorage organ. It bears capsule at the top. It is chiefly concerned with the formation and dispersal of the spores. Externally it is differentiated into three well marked regions i sterile basal region the apophysis ii central fertile region, the theca and iii upper region the operculum enclosing peristome. It consitutes the basal zone of the capsule that gradually narrows below. Its outermost boundary is surrounded by a single layered thick epidermis, interrupted at places by stomata.
Each stoma has an annular guard cell with an opening in the middle that opens into a small air space. Within the epidermis is a broad spongy zone of sterile cells rich in chloroplast.
The intercellular spaces occurring in between these chlorophyllous cells make it as an organ of active photosynthesis. The central tissue of this zone that consists of vertically elongated achlorophyllous cells and is collectively called as central strand.
It is in continuation with the central strand of the seta below. Central strand is connected with columella by few bundles of filaments the cells of which are thin walled, vertically elongated and fewer in number.
The wall of this zone is several cells thick and highly differentiated. A clearly defined row of cells form the outermost covering of the wall, the epidermis with few stomata. Internal to the epidermis are colourless compact parenchymatous cell arranged in 1 or 2 layers. It constitutes the hypodermis. The cells continuous with the inner side of the hypodermis constitute spongy layer. The spongy layer is also 1 or 2 cells thick.
The cells of this zone are loosely arranged and contain chloroplasts. A large number of wide, cylindrical air spaces occurring within the capsule wall are formed in between transversely oriented strands of narrow, green elongated cells the trabeculae which connect the innermost wall of the capsule with the outer most wall of the spore sac. The spore sac on its outer side is surrounded by a single layer of cells inner spores sac representing the inner wall.
Spore sac is a barrel shaped structure open at both the ends. It is situated in between the wall of the capsule and the columella and contains numerous spores. The central part of the theca, the columella looks like a sole cylinder composed of delicate, colourless compact parenchymatous cells.
The columella is expanded above whereas its narrow basal part is connected with the central strand of the apophysis. It looks like an obliquely placed conical cap and is known as operculum. It consists of 4 or 5 layers of cells, of which the outer most layer with thick walled cells forms the epidennis.
The thin parenchymatous cells of other layers occupy the major part of the operculum. The operculum is separated from the theca by a narrow circular construction below which occurs a rim or diaphragm of 2 or 3 layers of radially elongated cells.
Just above this rim of theca lies the annulus that consists of 5 or 6 layers of cells, of which the upper most layer of elongated cells constitute the line along which the operculum separates from the theca. Each ring of peristome possesses 16 teeth.
The teeth of inner ring of peristome are colourless and delicate with their bases covered by the outer peristomical teeth that are placed opposite to that of inner ones. The outer teeth are conspicuous, red in colour and possess thick transverse bands.
The opening of the spore sac is closed by these elaborately sculptured and highly hygroscopic teeth Dehiscence of Capsule l In dry atmosphere, capsule begins to dry up loosing water from the thin walled cells. Thus a tension is developed which ruptures the spore sac. Thin walled delicate cells of the annulus break away, the operculum is thrown off and the peristome teeth are exposed. The outer peristome teeth, which by this time remain bent so as to cover the open spore sac, jerk and bend back dispersing the spores.
The peristome teeth form a finge around the mouth of the capsule. These by their hygroscopic movements assist in liberating the spores from the spore sac. The inner peristomial teeth usually do not exhibit hygroscopic movements but act as a further check over the spore sac.
The mechanical jerk exercised over the capsule by twisting and untwisting of the sets usder the influence by hygroscopic movements further aids in the dispersal of spores.
The presence of filaments of cells connecting theca and apophysis facilitate the wind effect on dispersal and at the same time provide mechanical support against wind. The whole capsule body bends easily.
Funaria life cycle Class 11 Biology
The group is represented by about genera and 24, species. Structure of Gametophyte: It shows two parts a prostrate underground protonema and an erect leafy … b : Protonema occurs in the life cycle of Funaria. Twisting and swinging of seta in dry weather further aids in the dispersal of spores. Funaria is terrestrial moss. Funaria hygrometrica is the most common species.