Summary of Changes to PO April 2012

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More detailed descriptions of the changes made to the Plant Ontology file are available on the POC Meetings Minutes and the SourceForge tracker.

New and Obsolete Terms

102 new terms for plant anatomical entities and 34 new terms for plant structure development stages were added in this release.

See separate page for a complete list of New_terms_and_obsolete_terms-April_2012_Release.

General changes

We have begun including the ids of PO and GO terms used in PO definitions and comments. This allows users to link directly to those terms from the AmiGO browser and provides additional quality control. An id is listed in parentheses after the first mention of a term in a definition or comment. All new definitions have ids in them, and ids are being added to older definitions as part of an ongoing process.

Changes to plant structure development stages

The release marks a major revision to the plant structure development stage branch of the PO. The bulk of the changes were in to whole plant development stage and its subtypes, but there were substantial changes made throughout this branch of the PO.

The decision was made to define stages as occurring during the interval between two landmarks (e.g., the sporophyte development stage occurs between fertilization and death). This means that any stage which occurs during that interval is a subtype of the longer stage, rather than a part of it (e.g., sporophyte vegetative stage is_a sporophyte development stage, not part_of sporophyte development stage). The part_of and has_part relations can still be used for development stages where appropriate, e.g., seed development stage has_part embryo development stage.

Change to root node

Plant structure development stage (PO:0007021) was merged into the original root node plant growth and development stage (PO:0009012) and plant structure development stage was made the primary name. The definition of this term was also updated.

The aspect (namespace in OboEdit) was changed from plant_growth_and_development_stage to plant_structure_development_stage.

Changes to whole plant growth stage and its subtypes

Made whole plant growth stage (PO:0007033) is_a plant structure development stage, renamed whole plant development stage and updated the definition.

Added a new term for life of whole plant (PO:0025337). The only instances of life of whole plant are a maximal gametophyte development stage and a maximal sporophyte development stage. Gametophyte development stage and sporophyte development stage are part_of life of whole plant but remain as subtypes of whole plant development stage, because not every gametophyte or sporophyte development stage is a life of whole plant, but all are part_of some life of whole plant .

Made the following terms subtypes of sporophyte development stage (were subtypes of whole plant development stage), because they were already defined for sporophytes:

  • sporophyte vegetative stage (PO:0007134)
  • sporophyte reproductive stage (PO:0007130)
  • sporophyte senscent stage (PO:0007017)
  • sporophyte dormant stage (PO:0007132)

Added new terms for corresponding stages in gametophytes:

  • gametophyte vegetative development stage (PO:0025340)
  • gametophyte reproductive development stage (PO:0025341)
  • gametophyte dormant stage (PO:0025342)
  • gametophyte senescent stage (PO:0025343)

Made protonema whole plant development stage (PO:0030006) is_a gametophyte vegetative development stage (was a whole plant development stage) and updated definition.

Renamed "embryo development stages" (PO:0007631) to plant embryo stage, made it is_a sporophyte vegetative stage, and updated the definition.

Renamed "A zygotic stage" (PO:0001097) to plant zygote stage, made it is_a sporophyte development stage, and updated the definition.

Added relation seed dormant stage has_part plant embryo dormant stage.

Changes to other types of development stages

The subtypes of plant structure development stage were organized to reflect the structure of the plant anatomical entity branch of the PO. These subtypes include whole plant development stage (existing term, see details above), plus new terms for collective plant structure development stage, plant organ development stage, plant tissue development stage, and trichome development stage. Seed development stage was made a subtype of plant structure development stage, rather than a subtype of sporopyhyte vegetative development stage.

  • Flower development stage, fruit development stage, and inflorescence development stage are now subtypes of collective plant structure development stage (PO:0025338).
  • Leaf development stage and root development stage are now subtypes of plant organ development stage.
  • Leaf trichome development stage is now a subtype of trichome development stage.

Added new terms for seed trichome development stage and its subtypes, at the request of annotators describing cotton development.

Added new terms for 'vascular tissue development stage, phloem development stage, and xylem development stage as subtypes of plant tissue development stage.

Added secondary xylem development stage and its subtypes, as part of an ongoing project to add terms to the PO for wood anatomy and development, in collaboration with a group of wood scientists (see Wood anatomy ontology meeting, 2012 at NYBG, agenda.

Updated definitions of radicle emergence stage, coleoptile emergence stage, epicotyl emergence stage, hypocotyl emergence stage so that they are now defined as emerging from the seed coat, rather than the soil.

See New_terms_and_obsolete_terms-April_2012_Release#New_plant_structure_development_stage_terms for a complete list of new and renamed terms. No plant structure development stage terms were made obsolete in this release.

General changes to plant structure development stage terms

A decision was made not to prefix new plant structure development stage terms with numbers or letters, and number/letter prefixes are being removed from existing terms as we update them. This means that terms may not be displayed in chronological order in the PO browser but makes the names clearer. Chronological order may be described by comments such as "stage X precedes stage Y", "stage Y is preceded by stage X", or "stage Y succeeds stage X". In future releases, this temporal relations may be specified in the PO.

"Stage" has been appended to the end of most plant structure development stage term names.

All term names are now singular.

Changes to plant anatomical entities

Major revisions to the overall structure of the plant anatomical entity branch of the PO were completed during previous revisions. Ongoing work on this branch is aimed at refining definitions (including converting text definitions to genus-differentia form and adding logical or cross-product definitions) and adding new terms to meet users needs.

Definition updates

Definition updates to the terms listed below the updates converted the definitions to the genus-differentia format and made them clearer and/or more precise.

As part of a PO-led initiative to incorporate term to describe wood anatomy, development, and phenotypes, the definitions of most vascular tissue and cell types and related terms were reviewed, and many were updated. Updated terms include: portion of vascular tissue (PO:0009015), vascular bundle (PO:0005020), phloem (PO:0005417), primary phloem (PO:0006075), secondary phloem (PO:0005043), protophloem (PO:0006077), metaphloem (PO:0006076), secondary phloem (PO:0005043), xylem (PO:0005352), primary xylem (PO:0005849), protoxylem (PO:0000272), metaxylem (PO:0000372), secondary xylem (PO:0005848), tracheid bar (PO:0019026), leaf lamina vein (PO:0020138), leaf midvein (PO:0020139), secondary leaf vein (PO:0020140), lateral leaf vein (PO:0006011), tertiary leaf vein (PO:0008021), quaternary leaf vein (PO:0008022), higher order leaf vein (PO:0008023), lateral meristem (PO:0020145, cambium (PO:0005597), vascular cambium (PO:0005598), cork cambium (PO:0005599), sieve tube element (PO:0000289), tracheary element (PO:0000290), xylem fiber cell (PO:0000274), fiber tracheid (PO:0000355), libriform fiber cell (PO:0004520), secondary xylem parenchyma (PO:0004532), axial secondary xylem parenchyma (PO:0004533), ray secondary xylem parenchyma (PO:0004534), secondary xylem parenchyma cell (PO:0004525), ray secondary xylem parenchyma cell (PO:0004527), upright ray secondary xylem parenchyma cell (PO:0004528), procumbent ray secondary xylem parenchyma cell (PO:0004529), axial secondary xylem parenchyma cell (PO:0004526), tracheary element (PO:0000290), tracheid (PO:0000301), xylem vessel member (PO:0002003), schlerencyma cell (PO:0000077), companion cell (PO:0000071), sapwood (PO:0004513), heartwood (PO:0004512), early wood (early wood), late wood (PO:0004516), growth ring (PO:0004516), growth ring boundary (PO:0004517), cambial initial cell (PO:0000295), plant fiber cell (PO:0025407), xylem fiber cell (PO:0000274), phloem fiber cell (PO:0004519), and septate fiber cell (PO:0004521).

Other terms with modified definitions include: intercalary meristem (PO:0006073), leaf intercalary meristem (PO:0006346), stem intercalary meristem (PO:0006347), seed trichome (PO:0004511), carpel anlagen (PO:0006005), stipule (PO:0020041), stolon (PO:0003024), arilloid (PO:0019022), strophiole (PO:0019023), caruncle (PO:0020060), aril (PO:0009090), elaiosome (PO:0020062), tassel inflorescence branch meristem (PO:0009107), ear inflorescence branch meristem (PO:0009110), fruit nucellus (PO:0008005), and leaf lamina (PO:0020039).

Made seed is_a plant structure, instead of is_a whole plant and updated the definition. Removed the relation seed part_of fruit and added seed develops_from ovule, seed has_part embryo.

Renamed "spore" (PO:0025017) plant spore and made it is_a whole plant as well as is_a plant cell. Updated the definition to refer to the plant spore stage (PO:0025375).

Renamed "atrichoblast" (PO:0000263) non-hair root epidermal cell, made "atrichoblast" an exact synonym, and updated definition. Also updated definition of root hair cell (PO:0000256).

other changes

  • Replaced "wood" in term names with "secondary xylem" (e.g., wood parenchyma became secondary xylem parenchyma), but kept names with wood as synonyms. However, the commonly used terms late wood, early wood, heartwood, sapwood, and reaction wood were kept as primary names.
  • Changed name of "awn" (PO:0006032) to lemma awn, because it was already part_of lemma. Modified text definition to reflect that it is part of lemma. Added new general term for awn (PO:0025349), plus new subtypes for palea awn (PO:0025350) and glume awn (PO:0025351)
  • Made flower meristem is_a reproductive shoot apical meristem, revised definition
  • Added comment to all leaf vein orders that they should not be used with dichotomously branching vein patterns.
  • Changed phellem and phelloderm to part_of periderm, instead of part_of shoot axis periderm, because it can also be found in roots.

Revised def'ns:

  • Sporophyte vegetative stage (PO:0028002): A sporophyte development stage (PO:0007134) that occurs during the interval between fertilization and the first cell division of the plant zygote. Revised comment: Precedes the plant embyro stage (PO:0007631). Refers to the GO Biological Process term: fertilization (GO:0009566).
  • sporophyte development stage (PO:0028002), sporophyte vegetative stage (PO:0007134) and seedling development stage (PO:0007131) with Po ids.

Changes to radicle emergence stage (PO:0007015), coleoptile emergence stage (PO:0007045) and related terms:

  • coleoptile (PO:0020033): A plant organ (PO:0009008) that surrounds the plumule (PO:0020032) of a plant embryo (PO:0009009) or the emerging shoot apex (PO:0000037) of a seedling. (is_a plant organ).
  • embryo coleoptile (PO:0025286) and seedling coleoptile (PO:0025287)
  • plumule (PO:0020032): The shoot apex (PO:0000037) of the plant embryo (PO:0009009), above the cotyledonary node (PO:0025321).
  • cotyledon (PO:0020030): A vascular leaf (PO:0009025) formed at the first shoot node (PO:0005004) of a plant embryo (PO:0009009) or a seedling (PO:0000003). (added new child terms: embryo cotyledon (PO:0025470) and seedling cotyledon (PO:0025471)).
  • radicle (PO:0020031): An embryo root (PO:0000045) that is the basal continuation of a hypocotyl (PO:0020100) in a plant embryo (PO:0009009) or a seedling (PO:0000003).
  • embryo radicle (PO:0025296) (is_a embryo root), seedling radicle (PO:0025297)
  • coleorhiza (PO:0020034): A sheath-like plant organ (PO:0009008) that surrounds the radicle (PO:0020031) of a plant embryo (PO:0009009) or the emerging root (PO:0009005) of a seedling (PO:0000003).
  • embryo coleorhiza (PO:0025288), seedling coleorhiza (PO:0025289)
  • hypocotyl (PO:0020100): A stem internode (PO:0020142) below the cotyledonary node (PO:0025321) and transitional to a root (PO:0009005) of a plant embryo (PO:0009009) or a seedling (PO:0000003).
  • embryo hypocotyl (PO:0025290) and seedling hypocotyl (PO:0025291)
  • epicotyl (PO:0020035): The first stem internode (PO:0020142) above the cotyledonary node (PO:0025321) of a plant embryo (PO:0009009) or a seedling (PO:0000003).
  • embryo epicotyl (PO:0025292) and seedling epicotyl (PO:0025293)
  • plant embryo stage (PO:0007631) and plant embryo (PO:0009009): removed reference to cotyledons in pteridophytes, added Po ids and terms names.
  • Updated the comment on plant embryo (PO:0009009) to include the details of the end of the plant embryo stage in various taxa.
  • radicle emergence stage (PO:0007015): A root development stage (PO:0007520) during which a radicle (PO:0020031) emerges from the seed coat (PO:0009088). (part_of seed germination stage (PO:0007057)).
  • coleoptile emergence stage (PO:0007045): A sporophyte vegetative stage (PO:0007134) during which the coleoptile (PO:0020033) emerges from the seed coat (PO:0009088).
  • cotyledon emergence stage (PO:0007049): A seedling development stage (PO:0007131) during which the cotyledon (PO:0020030) emerges from the seed coat (PO:0009088).
  • epicotyl emergence stage (PO:0007054): A seedling development stage (PO:0007131) during which the epicotyl (PO:0020035) emerges from the seed coat (PO:0009088).
  • hypocotyl emergence stage (PO:0007043): A seedling development stage (PO:0007131) during which the hypocotyl (PO:0020100) emerges from the seed coat (PO:0009088).

Added relations:

  • seedling hypocotyl (PO:0025291) participates_in seedling development stage (PO:0007131)
  • plant zygote (PO:0000423) participates_in plant zygote stage
  • primary root develops from seedling radicle
  • plant zygote stage (PO:0001097) is_a sporophyte development stage (PO:0028002)

Created new terms

  • embryo cotyledon (PO:0025470) and seedling cotyledon (PO:0025471)
  • coleorhiza emergence stage (PO:0025475): A root development stage (PO:0007520) during which a coleorhiza (PO:0020034) emerges from the seed coat (PO:0009088). Added relation part_of the seed germination stage (PO:0007057).

Summary of new and obsolete terms

For a complete list of new, renamed, and obsolete terms, see New_terms_and_obsolete_terms-April_2012_Release#New_plant_anatomical_entity_terms.

New term highlights:

New plant anatomical spaces: intercellular space (PO:0025379), leaf mesophyll intercellular space (PO:0025380), spongy mesophyll intercellular space (PO:0025381), palisade mesophyll intercellular space (PO:0025397), substomatal cavity (PO:0025382), phyllome substomatal cavity (PO:0025398), leaf substomatal cavity (PO:0025399), phyllome sinus (PO:0025383), leaf sinus (PO:0025384)

New portion of plant substance terms: cutin (PO:0025385), cuticular wax (PO:0025386), plant cuticle proper (PO:0025387), epicuticular wax (PO:0025388), intercuticular wax (PO:0025389), leaf primary vein (PO:0025413)

New meristems: phyllome adaxial meristem (PO:0025400), leaf adaxial meristem (PO:0025401), phyllome abaxial meristem (PO:0025402), leaf abaxial meristem (PO:0025403), phyllome marginal meristem (PO:0025404), leaf marginal meristem (PO:0025405), secondary thickening meristem (PO:0025414), phyllome plate meristem: (PO:0025428), leaf plate meristem: (PO:0025429), phyllome anlagen: (PO:0025430), leaf anlagen (PO:0025431), cotyledon anlagen (PO:0025432), root anlagen (PO:0025433), shoot axis cork cambium (PO:0025435), root cork cambium (PO:0025436), shoot axis vascular cambium (PO:0025437), root vascular cambium (PO:0025438), cambial zone (PO:0025439), shoot axis cambial zone (PO:0025440), root cambial zone (PO:0025441), stem secondary thickening meristem (PO:0025442), root secondary thickening meristem (PO:0025443)

New vascular and wood related terms: shoot axis cork cambium (PO:0025435), root cork cambium (PO:0025436), shoot axis vascular cambium (PO:0025437), root vascular cambium (PO:0025438), cambial zone (PO:0025439), shoot axis cambial zone (PO:0025440), root cambial zone (PO:0025441), primary xylem tracheary element (PO:0025444), secondary xylem tracheary element (PO:0025445), primary xylem tracheid (PO:0025446), secondary xylem tracheid (PO:0025447), primary xylem vessel member (PO:0025448), secondary xylem vessel member (PO:0025449), primary xylem vessel (PO:0025450), secondary xylem vessel (PO:0025451), primary phloem sieve element (PO:0025452), secondary phloem sieve element (PO:0025453), primary phloem sieve cell (PO:0025454), primary phloem sieve tube element (PO:0025455), secondary phloem sieve cell (PO:0025456), secondary phloem sieve tube element (PO:0025457), transfer companion cell (PO:0025458), ordinary companion cell (PO:0025459), intermediary companion cell (PO:0025460), early wood tracheary element (PO:0025461), late wood tracheary element (PO:0025462), reaction wood (PO:0025472), compression wood (PO:0025473), tension wood (PO:0025474)

Obsolete terms:

Only two terms were made obsolete (depricated) for this release:

  • xylem element (PO:0000273), consider tracheary element (PO:0000290) or xylem fiber cell (PO:0000274)
  • axial cell (PO:0000081), consider fiber cell (PO:0025407), sieve element (PO:0025406), or tracheary element (PO:0000290)

These terms were made obsolete because they did not represent valid anatomical groupings.


Many synonyms were added to the PO (see New_terms_and_obsolete_terms-April_2012_Release#New_synonyms), including 333 synonyms based on entries from the Flora of North America Glossary that mapped to existing terms.

Relation changes

Added new relation has_participant. Following BFO, the domain is occurent and range is continuant, which correspond to plant structure development stage and plant anatomical entity, respectively, in the PO.

Added has_participant relations between a number of terms, such as:

  • whole plant development stage (PO:0007033) has_participant whole plant (PO:0000003)
  • trichome development stage (PO:0025368) has_participant trichome (PO:0000282)
  • leaf trichome development stage (PO:0007039) has_participant leaf trichome (PO:0006504)
  • xylem development stage (PO:0025425) has_participant xylem (PO:0005352)

plus other plant structure development stages, as appropriate

Added xrefs to BFO or RO for develops_from, has_part, part_of, and adjacent_to. This makes the PO file more compatible with other ontologies.

Changed the id of derives_by_manipulation_from from "derives_from" to "derives_by_manipulation_from", so it will not be confused with the more general relation derives_from.

Logical definitions

The PO currently has 64 terms with logical or "cross-product" definitions, and more of these relations are being incorporated into the PO as we move forward.

Examples of new cross-product (XP) relations added for this release include:

  • shoot lateral meristems and root lateral meristems as XPs of lateral mersistem and part_of shoot system or root, respectively
  • primary vascular tissue and secondary vascular tissue as XPs of vacular tissue and develops_from procambium or cambium, respectively
  • plant embryo stage as XP of sporophyte development stage and has_participant plant embryo
  • plant spore development stage as XP of sporophyte development stage and has_participant plant spore
  • xylem fiber cell and phloem fiber cell as XPs of plant fiber cell and part_of xylem or phloem, respectively


Links to images

We have added several test links to images on

PlantSystematics_image_archive:1597 to septum (PO:0000030) and fruit septum (PO:0025268)

PlantSystematics_image_archive:14891 and PlantSystematics_image_archive:8662 to pappus (PO:0025393) and pappus element (PO:0025394)

These show up as External References (near the bottom of the page) on AmiGO.

Glossary of PO terms

The definitions of all plant anatomical entities are now available in glossary form: Glossary of Plant Anatomy.

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