mega- and microgametophyte

[planteome-user]

We should obsolete PO:0020092 megagametophyte and PO:0020091 microgametophyte, and create new terms that can encompass dioicous bryophyte gametophytes as well as the gametophytes in angiosperms. Embryo sac and pollen will be children of these terms, as well as archegonial megagatephyte and antheridial microgametophyte. See separate trackers for embryo sac and pollen.

Proposed definitions:

megagametophyte: A whole plant in the gametophytic phase that produces only egg cells.

Comment: Megagametophytes in bryophytes only produce egg cells, but do not develop from megaspores, because there is no heterospory in bryophytes. In some pteridophytes, megagametophytes develop from megaspores. In angiosperms, Gnetum and Weltwischia the megagametophyte is greatly reduced. The megagametophyte in angiosperms is an embryo sac.

microgametophyte: A whole plant in the gametophytic phase that produces only sperm cells.

Comment: Microgametophytes in bryophytes only produce sperm cells, but do not develop from microspores, because there is no heterospory in bryophytes. In some pteridophytes, microgametophytes develop from microspores. In seed plants the male gametophyte is reduced to a pollen grain.

archegonial megagametophyte: A megagametophyte that has as parts one or more archegonia.

Comment: Megagametophytes in bryophytes only produce egg cells, but do not develop from megaspores, because there is no heterospory in bryophytes. In some pteridophytes, megagametophytes develop from megaspores.

only_in_taxon bryophyte plus pteridophytes

antheridial microgametophyte: A microgametophyte that has as parts one or more antheridia.

comment: Microgametophytes in bryophytes only produce sperm cells, but do not develop from microspores, because there is no heterospory in bryophytes. In some pteridophytes, microgametophytes develop from microspores.

only_in_taxon bryophyte plus pteridophytes

Reported by: rlwalls2008

Original Ticket: obo/plant-ontology-po-term-requests/318