#508 embryo sac cell

[Ramona Walls]

We have a term called megagametophyte cell ( (PO:0025026) , which is defined as a plant cell that is part of an embryo sac. I suggest that we rename this embryo sac cell, and add intersection of relations.

Made these changes to dev version, based on our Skype meeting on 10-4-12.

[Laurel Cooper]

Moved to be is_a native plant cell and updated the def'n:

embryo sac cell :PO:0025026
A native plant cell (PO:0025606) that is part of an embryo sac (PO:0025074).
OBO_SF2_PO:508

See: [plant-ontology-po-term-requests:#586]