Classification and Characters of Polysiphonia

                                  Polysiphonia

 Classification :-              

                                           Division :- Rhodophyta

                                           Class :- Florideophyaecae

                                            Order :- Ceramiales

                                           Family :- Rhodomelaece

                                           Genus :- Polysiphonia

Occurrence of Polysiphonia:  

The genus Polysiphonia (Gr. poly — many; siphon — tube) is described by quite a hundred and fifty species, out of that concerning sixteen species ar according from Asian country.

 They grow in marine environs and ar cosmopolitan in distribution.

Commonly they're found in littoral and ocean floor zones.

 In Asian country they're found in western and southern coasts.

Commonly, they grow as lithophytes i.e., on rocks or stones (e.g., P. elongata), some species like P. urceola, P. terulacea grow as epiphytes on genus Laminaria.

P. fastigiata grows as semiparasite on rockweed.

Plant Body of Polysiphonia:

Polysiphonia

Plant body is multiaxial well branched plant part of dark brown, cerise or blue-black red colouration showing as a awfully little bush the peak of the bush varies from some to many centimeters.

Most of the species ar heterotrichous in habit, consisting of prostrate and erect systems.

Prostrate System:

It may be multiaxial and well developed. From the lower aspect of the prostrate system several living thing rhizoids ar developed .

The rhizoids ar abundant compound at the apex and type definite attach¬ment discs (e.g., P. urceolata, P. nigrescens).

In P. elongata and P. violacea, the prostrate system is absent and plenty of rhizoids develop from the lower most cells of the erect system and by aggregation they type huge attachment disc.

Erect System:

The erect filaments develop from the prostrate system.

 The erect system con¬sists of main axis and plenty of branches .

The branches ar of 2 types: long branch and short branch

The long branches ar referred to as branches of unlimited growth or long lateral branches and therefore the short branches i.e., branches of restricted growth ar referred to as trichoblasts.

The long bran¬ches develop during a spiral or balance.

The trichoblasts ar spirally organized, dichotomously branched, colourless and largely annual struc¬tures bearing sex organs.

The trichoblasts might develop each from main axis and long branches.

The main axis and long branches contains a central siphon of the many elongated cylindrical cells settled in vertical row .

it's encircled by 4-20 peripheral siphons. therefore the plant body is polysiphonous and named Polysiphonia. solely the central siphon is gift at the top region of each main axis and therefore the long branches.

In most of the species, pericentral siphon is roofed by three layers of animal tissue cells fashioned because of periclinal and anticlinal divisions of the cells of pericentral siphon.

All cells of the plant body ar connected with one another by pit connections (cytoplasmic connections).

The short branches or trichoblasts ar monosiphonous.

Cell Structure of Polysiphonia:

The cells have thick wall, differentiated into outer cellulose and inner plastic layers.

 The cells ar uninucleate  with several disklike chro-matophores while not pyrenoids. neighbour cells ar connected by pit connections.

 The cells contain massive central bodily cavity. Reserve food is floridean starch.

Important options of Polysiphonia:

1. Plant body is polysiphonous.

2. top growth takes place by single dome- formed top cell.

3. reproduction is of advanced ooga¬mous sort.

4. Post-fertilisation stage is far elaborate.

5. Cystocarp is well-developed.

Cystocarp

Reproduction in Polysiphonia:

Polysiphonia reproduces each asexually and sexually. reproduction is of oogamous sort. within the life cycle of Polysiphonia 3 types of plants ar recognised.

These are:

1. Diploid tetrasporophyte,

2. Haploid plant, and

3. Diploid carposporophyte 

1. Diploid Tetrasporophyte:

It develops on direct germination of spore (2n = 40), therefore the plant is diplsid (2n).

 it's associate degree freelance plant that, rather than developing sex organs develops tetrasporangia.

The diploid nucleus of tetrasporangia undergoes meiosis and develops four (4) haploid (n = 20) tetraspores.

2. Haploid Gametophyte:

It develops on direct germination of spore (n); therefore the freelance plant is haploid (n).

Most of the species ar heterothallic, therefore the spermatangia (male sex organ) and carpogonia (female sex organ) ar developed on totally different plants.

3. Diploid Carposporophyte:

Development of Carpospore

This stage is diploid (2n) and hooked in to haploid gameto¬phytic plants.

The union between haploid (n) spermatium (developed within spermatangium) and haploid feminine reproductive cell (developed within carpogonium) forms diploid (2n) nucleus within the carpogonium.

Further development of diploid nucleus forms diploid carposporophyte. Later carpospores ar fashioned by mitotic division of carposporangium.

The spore on direct germination forms diploid tetrasporophyte plant.

Asexual Reproduction:

Asexual reproduction takes place by haploid non-motile tetraspores.

The carpospores (2n) on direct germination develop diploid tetrasporophytic plants.

 The plants ar freelance and polysiphonous.

Some pericentral cells of the plant part close to top region develop sac-like tetrasporangia.

The diploid nucleus of spore case undergoes meiosis and forms four tetraspores. 

The spores ar organized tetrahedrally

Development of Tetraspores:

Tetraspores ar made in tetrasporangia. Single pericentral cell of every tier, towards top region functions as tetrasporangial initial .

this primary cell is smaller than different pericentral cells of any explicit tier. this primary cell divides vertically into inner and outer cells.

The inner cell func¬tions directly into sporangial cell and therefore the outer cell additional divides and forms 2 or additional cowl cells.

 The sporangial cell divides transversally into lower stalk cell and higher tetra- sporangial cell.

The latter undergoes additional enlargement and develops into a tetrasporan¬gium.

 The diploid nucleus of spore case undergoes meiosis and forms four tetraspores or meiospores.

The tetraspores ar organized tetra¬hedrally within the spore case.

The mature tetraspores ar liberated by rupturing the wall of the reproductive structure.

 On germination they develop gametophytic polysiphonous plant.

Being heterothallic, out of 4 tetraspores, 2 manufacture male and therefore the remaining 2 produce feminine gametophytic plants.

Sexual Reproduction:

Sexual reproduction is of oogamous sort. Plants ar normally dioecian.

The male sex organs i.e., spermatangia and feminine sex organs i.e., carpogonia, ar developed on male and feminine plants, severally.

1. Male Sex Organ:

It is referred to as spermatangium or reproductive structure.

Initially male trichoblast develops as aspect branch on the plant body 

.

It becomes branched. In some species each the branches become fertile, however in others only 1 remains fertile and therefore the rest endure perennial classification to make divided sterile structure.

The monosiphonous fertile branch(es) of male trichome bears several living thing and spherical spermatangia.

 every spermatangium could be a uni¬nucleate structure that produces single sper¬matium, the male reproductive cell.

During development of spermatangium ,all cells except some basal cells, divide periclinally and type pericentral cells on each the edges.

 every pericentral cell undergoes many divisions and forms spermatangial mother cells.

all cuts off 2-4 living thing bodies, the spermatangia.

every spermatangium develops into one non-motile male reproductive cell, the spermatium.

The spermatia ar liberated from the sper¬matangium, through a slim top slit on the wall. The spermatia ar distributed through water.

2.Female Sex Organ:

The female organ is termed carpogonium.

The carpogonium develops at the highest of 2-5 celled carpogonial filament . 

The carpogonial filament develops on the feminine tricho¬blast.

The carpogonium could be a flask-shaped body, with a basal swollen region containing associate degree egg associate degreed an higher elongated neck region, the trichogyne.

During development of carpogonium, ini¬tially a feminine trichoblast initial is developed on central siphon, some cells (3-4) below the top cell.

 the feminine trichoblast initial, then undergoes perennial divisions and forms a feminine trichoblast of 5-7 cells.

The bottommost 3 cells of the feminine trichoblast divide vertically and type 3 tiers of pericentral cells.

Any one of the pericentral cells of the center tier towards the mother axis becomes the supporting cell.

The supporting cell cuts off alittle initial at its outside, the procarp initial .

The procarp at first undergoes perennial divisions and forms a 4-celled branch, the procarp or carpogonial filament (branch).

The top cell of the carpogonial filament functions as carpogonium cell.

The cell additional develops into a carpogonium.

The carpogonium features a swollen basal region containing egg associate degreed an elongated cannular region, the trichogyne .

At the later stage, the carpogonium develops 2 initials from the supporting cell, one at the bottom, the basal sterile filament initial and another at the lateral aspect, the lateral sterile filament initial. The lateral sterile initial divides transversally and forms two-celled lateral sterile filament .

The carpogo¬nium is prepared for fertilisation at this stage

.

The pericentral cell adjacent to the supporting cell starts growing to hide the fertile carpo¬gonium.

afterward they type sheath (the protecting covering) round the fruit body, referred to as as cover.

Fertilisation:

The spermatia ar distributed with the assistance of water. some spermatia become hooked up at the tip of the. receptive trichogyne.

Out of the many, only 1 becomes productive.

The common wall of productive spermatium and trichogyne dissolves at the purpose of contact and therefore the male nucleus passes to the feminine nucleus gift at the bottom of the carpogonium.

 The fusion between the nuclei leads to the formation of fertilized ovum.

Post-Fertilisation Changes:

At the beginning of this section, associate degree radical cell is developed from the supporting cell settled slightly below the basal region of the carpogonium .

at the same time, the lateral,.sterile filament will increase long (4-10 celled) by cellular division still as elongation and therefore the basal sterile initial divides to make a 2 (2)-celled filament.

The radical cell features a single haploid nucleus.

A cannular affiliation is then developed between the radical cell and carpogonium . 

The carpogonial nucleus (2n) divides mitotically into 2 nuclei, of that one is transported to the radical cell and therefore the different one remains within the carpogonium.

 therefore the radical cell contains one haploid and one migrated diploid nuclei.

The haploid nucleus (n) is degenerated. bit by bit the trichogyne shrivels .

Many vegetative filaments then develop from the adjacent vege¬tative pericentral cells, that bit by bit develop the overall covering.

 The diploid nucleus of radical cell then divides mitotically and forms 2 nuclei. one among them then migrates into the outgrowth developed on the radical cell.

This outgrowth when separating by a partition wall forms goni¬moblast initial .

during this manner several gonimoblast initials will develop on radical cell. every initial by perennial mitotic divisions forms gonimoblast filament.

 The terminal cell of the gonimoblast filament develops into carpospo¬rangium, that forms single diploid spore within .

During this development the radical cell, supporting cell, carpogonium and a few cells of basal associate degreed sterile filaments fuse along and type an irregular cell, the placental cell .

The haploid nuclei (n) of the placental cell bit by bit degenerate and have merely a nutritious perform.

The placental cell, gonimoblast filament associate degreed carpogonia ar coated by several vegetative filaments and type an urn-shaped structure, the cystocarp .

The outer cove¬ring of cystocarp is termed cover.

The diploid a part of the cystocarp represents the carpo¬sporophyte. Some cells of basal and sterile fila¬ment at the side of some cells of carpogonial fila¬ment bit by bit degenerate.

The carposporangium develops single diploid spore. when liberating from the carpogoni¬um they are available out through the pore of cysto- carp

Germination of Carpospore:

Coming connected with any solid surface, the diploid spore gets hooked up then undergoes 1st mitotic division and forms massive higher and little lower cells .

each the cells endure mitotic division and type four celled stage.

The lower most cell forms the strand, the higher one functions as top cell and therefore the rest cells endure additional development and type the polysiphonous body.

This plant body is diploid i.e., the tetrasporophytic plant, that later develops the tetraspores and complete the cycle.

Life Cycle of Polysiphonia:

Life cycle of Polysiphonia consists of 3 distinct phases: diploid tetrasporophyte, haploid gametophytes and diploid carposporophyte.

Out of four tetraspores made in tetraspo¬rangia on diploid tetrasporophytic plant, 2 tetraspores develop haploid (gametophytic) male and different 2 haploid (gametophytic) feminine plants.

The male gametophytic plants develop male gametes within spermatangia {and feminine|and feminine} gametophytic plants develop female gametes within carpogonigia.

Zygote develops within carpogonium when gametic fusion.

With gradual development gonimoblast filament, carposporangia and carpospores ar developed within a composite structure, the cystocarp. it's the carposporophytic stage.

Diploid spore on germination produces the diploid tetrasporo¬phytic plant once more.

Thus the life cycle is triphasic and haplo- diplobiontic sort