Bangiaceae Pigment Mutation Characteristics And Early Gametophyte Development Mode

Pigment mutants of P. yezoensis, P. haitanensis, P. oligospermatangia, P. katadai var. hemiphylla and Bangia sp. were obtained by using chemical mutagen MNNG on thalli, conchocelis and conchospores. The occurrence and expression regulation of pigment mutations in Bangiaceae were studied. Biological characterizations of the process of meiosis, early development mode, thalli formation and sex determination showed by the mutation regularity were also discussed in this group of seaweeds.The results revealed that identical behavior in Bangiaceae but vary expression characters in different life stages were showed within a suitable inducing dose. Spot-mutation modes with single cell as a unit appeared in the thalli, and randomly variegated organizations were obtained. Mutations of thalli were direct outcomes to the variation of haploid cells. Induced conchocelis seemly had lower mutation rates. However mutagenesis happened in their F₁ thalli widely. The regularity of mutation expression in diploid cells was showed. Mutations of conchospores happened directly at the spores' germination which indicated the change of the ploidy in cells.A lot of chimeras appeared among the offspring of induced conchocelis. It seems that the origin of pigment sectors in chimeras was connected with the first two divisions of conchospores, and each sector was only related to one original cell of the first four. These results showed the meiosis taken place in division of conchospores.Two different early development modes were showed in gametophyte, and they are linear mode in P. yezoensis et al. and zygomorphic pattern in P. katadai. There are at least two mechanisms of sex determination in Bangiaceae. Tetrad characterization, early development mode, position of initial cells and division of dominant cells in fronds, and even environment factors would play a part in thalli formation and sex behavior.