One group is illustrated by the figure, which shows the organization of the genome in Marchantia polymorpha, a liverwort.Although they all contain the same genes, they fall into two distinct groups with respect to the organization of their genes. Chloroplast genomes have been sequenced from representatives of most of the plant groups. The chloroplasts of mosses and liverworts, like those of all photosynthetic eukaryotes, contain multiple copies of a small genome: circular DNA molecules encoding some - but not all of the genes needed for their own replication and photosynthesis. The sporophyte generation is responsible for dispersal. Thus the gametophyte generation is responsible for sexual reproduction. Soon buds appear and develop into the mature leafy shoots. If a spore reaches a suitable habitat, it germinates to form a filament of cells called a protonema. These tiny spores are dispersed so effectively by the wind that many mosses are worldwide in their distribution. Late in the summer, the calyptra and operculum become detached from the sporangium allowing the spores to be released. It is responsible for the common name ("haircap moss") of this species.ĭuring the summer, each spore mother cell undergoes meiosis, producing four haploid spores - the start of the new gametophyte generation. The calyptra develops from the wall of the old archegonium and so is actually a part of the gametophyte generation. A stalk, at the tip of which is formed a sporangium (the brownish objects in the photo).A foot, which absorbs water, minerals, and food from the parent gametophyte.Mitosis of the zygote produces an embryo that grows into the mature sporophyte generation. The Sporophyte Generation Figure 16.3.2.3 Moss sporophyte
0 kommentar(er)
