Post Fertilisation events in Polysiphonia
Polysiphonia is a Red Marine Alga and a good number of siphon-like cells constitute the thallus structure of it . A series of events take place after the formation of the zygote which are as follows:.
(1) At first an auxillary cell is formed from the supporting cell and placed in between the carpogonium and the supporting cell.
(2) Then a tube is formed to connect the carpogonium and the auxillary cell.
(3) Next the 2n zygote nucleus divides mitotically to form it's replica and one of them is migrated to the auxillary cell from the carpogonium.
(4) The haploid nucleus of the auxillary cell degenerates and the migrated diploid nucleus divides into two .
(5) One of these 2n nucleus migrates into the newly formed outgrowth of the auxiliary cell which converts into the gonimoblast initial by a cross-wall formation.
(6) In this way many more gonimoblast filaments are formed and each of them divides and redivides to form short gonimoblast filaments whose tip swell up to form the carposporangium.
(7) The contents of each of the carposporangium develops into diploid carpospore.
(8) Meanwhile a placenta is formed by the joint activity of the carposporangium, auxillary cell, supporting cell,basal cells,and sterile filamets.
(9) In the next step an urn-shaped cystocarp is formed by the developing vegetative filaments enclosing the whole content which were previously formed .
(10) The 2n part of the cystocarp is the Carposporophyte which parasites on the female gametophyte .After the the liberation of each carpospore through the ostiole of the cystocarp germinates into a diploid tetrasporophytic plant which bears haploid tetraspores in each sporangia which after liberation and germination gives rise to haploid gametophyte.
(1) At first an auxillary cell is formed from the supporting cell and placed in between the carpogonium and the supporting cell.
(2) Then a tube is formed to connect the carpogonium and the auxillary cell.
(3) Next the 2n zygote nucleus divides mitotically to form it's replica and one of them is migrated to the auxillary cell from the carpogonium.
(4) The haploid nucleus of the auxillary cell degenerates and the migrated diploid nucleus divides into two .
(5) One of these 2n nucleus migrates into the newly formed outgrowth of the auxiliary cell which converts into the gonimoblast initial by a cross-wall formation.
(6) In this way many more gonimoblast filaments are formed and each of them divides and redivides to form short gonimoblast filaments whose tip swell up to form the carposporangium.
(7) The contents of each of the carposporangium develops into diploid carpospore.
(8) Meanwhile a placenta is formed by the joint activity of the carposporangium, auxillary cell, supporting cell,basal cells,and sterile filamets.
(9) In the next step an urn-shaped cystocarp is formed by the developing vegetative filaments enclosing the whole content which were previously formed .
(10) The 2n part of the cystocarp is the Carposporophyte which parasites on the female gametophyte .After the the liberation of each carpospore through the ostiole of the cystocarp germinates into a diploid tetrasporophytic plant which bears haploid tetraspores in each sporangia which after liberation and germination gives rise to haploid gametophyte.
Comments
Post a Comment