POC Conf. Call 4-12-11
POC meeting, Webex Conference Call; Date: Tuesday April 12th, 2011 10am (PDT)
In attendance:
POC members:
Absent:
Collaborators:
Acceptance of the minutes from the POC_Conf._Call_4-5-11?
Items arising from last week's meeting:
Sporangium
We currently have the class sporangium (PO:0025094), which is a cardinal organ part.
In bryophytes, the sporangium is a plant organ. In seed plants, it is a cardinal organ part (part of a sporophyll). In ferns, it grows on the surface of a leaf. Would it be legitimate to say that in seed plants, the sporangium is a reduced organ that is located in another organ?
Current def: A hollow cardinal organ part in which spores are produced. [source: ISBN:0716710072]
Comment: May be multicellular or unicellular. In bryophytes, particularly in mosses, a sporangium is referred to as a capsule
We also have:
megasporangium (PO:0025201): A sporangium in which megaspores are produced. [source: ISBN:0716710072]
microsporangium (PO:0025202): A sporangium in which microspores are produced. [source: ISBN:0716710072]
nucellus (PO:0020020): A megasporangium in a seed plant, composed of fleshy subepidermal tissue inside an ovule and surrounding a megasporocyte. [source: POC:rw]
Comment: In seed plants, the megaspores and megagametophyte are retained within the nucellus.
pollen sac (PO:0025277): A microsporangium that is part of a sporophyll where the pollen grains developed and are contained after they develop. [source: POC:curators]
Comment: A pollen sac is a microsporangium in seed plants. In angiosperms, a single, unfused pollen sac may contain an anther locule or several pollen sacs may fuse so they contain a single anther locule.
Proposed def. nucellus: A megasporangium in a seed plant, composed of fleshy subepidermal tissue located in an ovule and surrounding a megasporocyte.
Proposed def. pollen sac: A microsporangium that is located in a sporophyll and where the pollen grains developed and are located after they develop. [source: POC:curators]
(comments stay the same)
We could continue to use the more general part_of relation for located_in
Sporangium parts
This is continued from our discussion at the POC_Conf._Call_3-8-11
Currently classes like exothecium, endothecium, primary parietal cell layer and tapetum are part of anther wall (PO:0000002). However, these layers and their constituent cell types can be part of any sporangium, not just an anther. Proposed making them part of a general class sporangium wall (as we did for parts of leaf).
From Smith:
Liverworts: Embryo divides to form outer layer (ampithecium) that gives rise to jacket layer and inner mass (endothecium) that gives rise to archesporium (cells of which divide to produce sporocytes and nurse cell, may also produce elators).
Hornworts: Embryo divides to form ampithecium that gives rise to jacket layer and primiary sporogenous layer, and endothecium that gives rise to sterile columella in all but one species (where it gives rise to sporagenous tissue). Jacket layer is 4-6 cells thick, and outer layer develops into epidermis. Sporagenous tissue gives rise to sporocytes and filaments of sterile cells called pseudoelators.
Sphagnum: Upper tier of cells in the embryo divides to form endothecium that gives rise to sterile columella and ampithecium that gives rise to outer sterile layer and inner archesporium. Archesporium gives rise to sporogenous layer two to four cells thick. Outer sterile layer gives rise to jacket layer 3 or 4 cells thick.
Eubrya: Early division of capsule gives rise to multilayered ampithecium and endothecium (with ampithecial cells and endothecial cells). Endothecium (usually) gives rise to archesporium and columella. Columella cells adjacent to archesporium remain small and develop into inner spore sac. Ampithecium develops into a multilayered structure, including layers with and without chloroplasts and an epidermis.
Psilophyta: Paired sporangia (a synangium or maybe a reduced sporangiophore) develop from a single cell. First cell division leads to a jacket initial and an archesporial (primary sporogenous) cell. Repeated periclinal divisions of jacket initial lead to jacket layer four or five cells thick and divisions of archesporial cell lead to many sporogenous cells. No tapetum develops. Near maturity, irregular clumps of sporogenous tissue divide to give rise to spore mother cells, remainder disintegrate
Lycopods: Sporangia borne on sporophylls.
