planteome-user
commented
12 years ago The definitions for phloem, primary phloem, and secondary phloem were accepted at the POC meeting on 1-24-12 and has been updated in the file.
Revised definitions for protophloem and metaphloem were accepted at the POC meeting on 1-31-12 and have been added to the file.
protophloem (PO:0006077), revised definition: A portion of primary phloem tissue has as parts the first-formed sieve elements at a particular location and does not have companion cells (in angiosperms) or albuminous cells (in gymnosperms) associated with the sieve cells. comment: Protophloem is the first primary phloem to differentiate in any particular level of a vascular bundle. Sieve elements in the protophloem are smaller than in the metaphloem. The protophloem usually only lasts a short time before it is replaced by metaphloem.
metaphloem (PO:0006076), revised definition: A portion of primary phloem that has as parts companion cells (in angiosperms) or albuminous cells (in gymnosperms) associated with the sieve cells and that develops after the protophloem. Comment: Metaphloem develops after the vascular bundle has stopped elongating, in the same location as the primary phloem, replacing the protophloem. Sieve elements in the metaphloem are larger than in the protophloem. Differentiates before the secondary phloem, if any is formed.
Original comment by: rlwalls2008
The following suggestions have been reviewed by RW, DWS, and MAG. All definitions will reference Esau's Anatomy of Seed Plants.
phloem (PO:0005417) current def.: A portion of vascular tissue whose principal function is conducting organic substances. [GR:pj]
proposed definition: A portion of vascular tissue that has as parts sieve elements. Comment: Functions in the conduction of organic substances in vascular plants.
Note: currently, sieve element is listed as a synonym of sieve tube member, but this does not correctly follow Esau's usage. It was okay when we only had angiosperms in PO, but is no longer valid. Will create a separate tracker item for sieve elements.
metaphloem (PO:0006076) current def.: Part of the primary phloem that differentiates after the protophloem and before the secondary phloem, if any of the latter is formed.
proposed definition: A portion of primary phloem that differentiates after the protophloem. Comment: Differentiates before the secondary phloem, if any is formed.
protophloem (PO:0006077) current def.: The first-formed elements of the primary phloem.
proposed definition: A portion of primary phloem tissue that has as parts the first-formed sieve elements of the primary phloem.
primary phloem (PO:0006075) current def.: A portion of phloem tissue of the primary plant body.
proposed definition: A portion of phloem tissue that develops from the procambium. Comment: Primary phloem develops as part of GO:xxxx primary growth. develops_from PO:0025275 procambium
secondary phloem (PO:0005043) current def.: A portion of phloem tissue formed by the activity of the vascular cambium.
proposed definition: A portion of phloem tissue that develops from the vascular cambium. Comment: Secondary phloem develops as part of GO:0080117 secondary growth. develops_from PO:0005598 vascular cambium
See also tracker for primary and secondary vascular tissue: https://sourceforge.net/tracker/?func=detail&aid=3476726&group\_id=76834&atid=835555
Reported by: rlwalls2008
Original Ticket: obo/plant-ontology-po-term-requests/433