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The embryo proper is the entire embryo exclusive of the suspensor.

Has an outer epidermis (exothecium) and an endothecium and may have additional layers. If you are annotating to this structure for Zea mays or other grasses, please also add an annotation to the corresponding floret type. Choose the most specific term possible from: spikelet floret (PO:0009082), tassel floret (PO:0006310), lower floret of pedicellate spikelet of tassel (PO:0006313), lower floret of sessile spikelet of tassel (PO:0006315), upper floret of pedicellate spikelet of tassel (PO:0006314), upper floret of sessile spikelet of tassel (PO:0006316).

Examples include plant embryo (PO:0009009), megagametophyte (PO:0025279) and microgametophyte (PO:0025280).

In vitro growth is defined as microbe-free growth in a sterile, culture environment, usually in the laboratory. An example of a sterile culture environment is growth on or in a nutrient medium in a Petri dish, culture flask or test tube. Microbes may be intentionally added to the culture environment, such as in co-culture with Agrobacterium.

Includes isolated plant cells and small plant cell aggregates that proliferate while suspended in sterile liquid medium or spread on a solid agar medium.

The cell wall is generally removed using polysaccharide-degrading enzymes such as cellulase, pectinase and /or xylanase. The cultured plant cell may be in suspension culture or from callus culture on solid media.

May be derived from cultured plant callus or plant protoplast that was induced from a segment of leaf. In the case of the plant protoplast, after the re-establishment cell walls.

May be derived from cultured plant callus or plant protoplasts induced from a segment of root. In the case of the plant protoplast, after the re-establishment plant cell walls.

Cultured plant callus may induced to form from plant protoplasts or cultured plant cells in suspension culture. After supplementation with the appropriate plant growth regulators, further differentiation may lead to the development of plant tissues, plant organs and ultimately, a whole plant.

Includes isolated and maintained mature or immature zygotic embryos, somatic embryos or haploid embryos (derived from male gametophyte).

Cultured somatic plant embryos are commonly induced after the formation of callus from an explant and treatment with plant growth regulators.

In Arabidopsis, refers to the leaves that are borne on the elongated inflorescence branches. May ocur singly or pairs/whorls of leaves.

Arabidopsis, vegetative development is characterized by the production of the rosette leaves.

A lateral root primordium may arise from cells of a pericycle (PO:0006203) in a root, as in most seed plants (pericyclic lateral root primordium; PO:0025492), or from cells of an endodermis (PO:0000252) or other tissue in ferns and some seed plants (non-pericyclic lateral root primordium: PO:0025493). Transition from lateral root primordium to lateral root occurs with the formation of a root cap (PO:0020123), shortly after the development of a root apical meristem (PO:0020147), which can occur before the lateral root penetrates the exterior of the parent root.

The transition from ovule primordium to ovule occurs when an integument (PO:0020021) begins to develop from the protoderm (PO:0006210).

Use carpel primordium (PO:0004703) for the primordium (PO:0025127) of an individual carpel (PO:0009030).

Uninformative definition

The plant cuticle is produced in and secreted by epidermal cells (PO:0004013) of leaves (PO:0025034), stems (PO:0009047), fruits (PO:0009001), and other aerial plant structures. It has as parts an inner cuticle proper (PO:0025387) and an outer layer of epicuticular wax (PO:0025388).

Comment: this term is now available in the cellular_component aspect of the Gene Ontology (GO:0048226).

This term is now available in the cellular_component aspect of the Gene Ontology, GO:0043680.

This term was made obsolete because it is a subcellular component. See GO for the term pollen tube tip (GO:0090404). Since a pollen tube tip is part_of a pollen tube, which is part of a pollen cell, annotations for pollen tube tip may also go to the more general term pollen tube cell (PO:0025195).

This term was made obsolete because it is a subcellular component. Root hair tip (GO:0035619) has been added to GO. To annotate to a cell that has a root hair tip, consider root hair cell (PO:0000256).

A septum is formed by the fusion of the walls of two adjacent organs (ovary walls or anther walls), for example, the partition between two sections of an orange, seen in cross-section.

Lenticels are produced by the cork cambium (PO:0005599) and facilitate gas exchange.

A valve may develop from an entire carpel (as in Brassicaceae) or from part of a carpel (as in Fabaceae). If you are annotating to this term, please add an additional annotation to the specific type of fruit (PO:0009001), such as achene fruit (PO:0030107), berry fruit (PO:0030108), capsule fruit (PO:0030091), caryopsis fruit (PO:0030104), drupe fruit (PO:0030103), follicle fruit (PO:0030105), legume fruit (PO:0030100), nut fruit (PO:0030102), samara fruit (PO:0030099), schizocarp fruit (PO:0030098), silique fruit (PO:0030106), or their subclasses, depending on the species.

A vascular system consist of the totality of the portions of vascular tissue in their specific arrangement in a plant structure. May include other portions of plant tissue or plant cells (PO:0009002) of other types, such as parenchyma (PO:0005421) or fiber cells (PO:0025407).

Can occur in a stem or branch.

Unlike the root nodules, these contain functioning chloroplasts in the nodule cortex and are therefore capable of carbon fixation. Note: stem nodule is commonly used term for this structure, although the nodules are formed at positions of dormant adventitious root primordia.

Developmentally different from periderm cork cell (i.e., phellem), produced by cork cambium. If you are annotating to this term, please add an additional annotation to vascular leaf (PO:0009025).

This term is perhaps best defined functionally to prop the plant up, but sometimes prop roots may also act as breathing roots. Compare to pneumatophore (PO:0025357), which is a lateral root that grows upwards from below the soil or water surface.

If you are annotating to this term, please add an additional annotation to vascular leaf (PO:0009025) or non-vascular leaf (PO:0025075), depending on the species. All annotations for angiosperms, gymnosperms, and pteridophytes should go to vascular leaf and all annotations for bryophytes should go to non-vascular leaf.

If you are annotating to this term, please add an additional annotation to vascular leaf (PO:0009025) or non-vascular leaf (PO:0025075), depending on the species. All annotations for angiosperms, gymnosperms, and pteridophytes should go to vascular leaf and all annotations for bryophytes should go to non-vascular leaf.

If you are annotating to this term, please add an additional annotation to vascular leaf (PO:0009025) or non-vascular leaf (PO:0025075), depending on the species. All annotations for angiosperms, gymnosperms, and pteridophytes should go to vascular leaf and all annotations for bryophytes should go to non-vascular leaf.

If you are annotating to this term, please add an additional annotation to vascular leaf (PO:0009025) or non-vascular leaf (PO:0025075), depending on the species. All annotations for angiosperms, gymnosperms, and pteridophytes should go to vascular leaf and all annotations for bryophytes should go to non-vascular leaf.

Leaf procambial cells may be derived from the shoot apical meristem or can arise throughout the mesophyll of a developing leaf.

Xylem pole pericycle cells are cells in the pericycle that are adjacent to the protoxylem pole of a vascular bundle. Pericycle cells that are adjacent to other xylem cells in the vascular bundle are not considered xylem pole pericycle cells. Xylem pole pericycle cells may retain some meristematic activity and are the site of lateral root initiation.

Phloem pole pericycle cells are cells in the pericycle that are adjacent to the protophloem pole of a vascular bundle. Pericycle cells that are adjacent to other phloem cells in the vascular bundle are not considered phloem pole pericycle cells. Phloem pole pericycle cells are distinct from xylem pole pericycle cells in that they display cytoplasmic characteristics of a more differentiated status.

Proposed to be involved in the retrieval of solutes from the xylem sap.

The terms proteoid root, cluster root, and root cluster have all been used in the literature to describe either the proteoid root axis or clusters of rootlets, and caution should be taken when comparing studies because the definitions of these terms vary (Watts and Evans, 1999; Plant Physiology).

Companion cells are connected to sieve tube elements through plasmodesmata and function in phloem loading of small molecules, including photosynthate (either sucrose or raffinose-family oligosaccharides). May participate in phloem sucrose loading (GO:0009915). Molecules can be loaded into the companion cells from surrounding cells through either symplastic (via plasmodesmata) or apoplastic (transmembrane) transport. Unlike sieve tube elements, companion cells retain their nuclei and other organelles at maturity. A sieve tube element may have one or more or no companion cells associated with it. This term should not be used for other types of parenchyma cells (PO:0000074) that do not arise from the same phloem mother cell as a sieve tube element. Companion cells are found in angiosperms, as compared to albuminous cells (PO:0025412), which are found in non-angiosperm vascular plants. Companion cells may be specialized as transfer companion cells (PO:0025458), ordinary companion cells (PO:0025459), or intermediary companion cells (PO:0025460). Multiple types of companion cells may be found in the same plant.

May be dead at maturity. The secondary cell wall of a sclerenchyma cell is often thicker than other cell types in the same plant structure, but it is not always easy to distinguish from tracheary elements (PO:0000290) or sclerified parenchyma cells (PO:0000074). Compare with collenchyma cells (PO:0000075) that are always alive at maturity, have irregularly thickened primary cell walls, and do not have lignified secondary cell walls. Collenchyma cells provides flexibility while sclerenchyma cells provide hardness. Sclerenchyma cells include plant fiber cells (PO:0025407) and sclerid cells (PO:0025418).

Appear to be specialized for short-distance transfer of solutes. Transfer cells can occur anywhere there is a junction between two individuals, such as between a sporophyte and a gametophyte, or between a parasitic plant and its host.

This term was made obsolete because it is not appropriate. It is replaced by sieve element, tracheary element, and fiber cell.

The sperm cell is usually smaller than the egg cell. Male gametes may be defined as the motile gamete, rather than the smaller gamete. Plant sperm cells lack a cell wall.

Can occur on a stem or branch.

Not in current literature. More like an attribute.

Can occur in a stem or branch.

Functions as a population of stem cells that replenishes the meristem.

In Zea mays and other grasses, the floret meristem is part of a spikelet and develops into a specific type of floret. If you are annotating to this structure for Zea mays or other grasses, please also add an annotation to the spikelet type that the meristem is part of. Choose the most specific term possible from: spikelet (PO:0009051), ear spikelet (PO:0006320), ear pedicellate spikelet (PO:0006348), ear sessile spikelet (PO:0006349), tassel spikelet (PO:0006309), tassel pedicellate spikelet (PO:0006312), tassel sessile spikelet (PO:0006311).

If you are annotating to this structure for Zea mays or other grasses, please also add an annotation to the corresponding floret type. Choose the most specific term possible from: spikelet floret (PO:0009082), ear floret (PO:0006354), upper floret of pedicellate spikelet of ear (PO:0006350), upper floret of sessile spikelet of ear (PO:0006352).

If you are annotating to this structure for Zea mays or other grasses, please also add an annotation to the corresponding floret type. Choose the most specific term possible from: spikelet floret (PO:0009082), ear floret (PO:0006354), upper floret of pedicellate spikelet of ear (PO:0006350), upper floret of sessile spikelet of ear (PO:0006352).

Forms a sheath around the vascular system. It may have secondary walls later, part_of cortex.

Compare with non-hair root epidermal cell (PO:0000263). This term is for an entire epidermal cell that contains a root hair extension. To describe only the cell extension, see root hair (GO:0035618) or root hair tip (GO:0035619).

In dicots and gymnosperms, the cortex consists of mainly parenchyma cells. In monocots sclerenchyma develops in addition to parenchyma.

Compare to root hair cell (PO:0000256), which develops from a trichoblast (PO:0000262).

Develops while the vascular tissue (PO:0009015) is still elongating. When protoxylem tracheary elements (PO:0025575) are destroyed they may become obliterated by surrounding parenchyma cells (PO:0000074). Protoxylem has smaller elements than the metaxylem (PO:0000372).

This term was made obsolete because it was not appropriate. Replaced by tracheary element (PO:0000290) and xylem fiber cell (PO:0000274).

It may be difficult to distinguish xylem fiber cells, especially fiber tracheids (PO:0000355), from tracheary elements (PO:0000290). Fiber tracheids have bordered pits with smaller pit cavities than the vessel members (PO:0002003) or tracheids (PO:0000301) of the same wood and a distinct pit cavity leading to the cell lumen through the cell wall.

This class is the union of unicellular trichome (PO:0025537) and multicellular trichome (PO:0025162). A trichome can vary in length and shape and may be branched or unbranched. It may be glandular or non-secretory.

Often contains deposit of minerals or products of secondary metabolism. May have a specialized function.

Sieve tube elements have sieve areas that are specialized into those with wide pores in sieve plates and those with narrow pores in lateral sieve areas. Sieve tube elements may have inclined end walls with compound or simple sieve plates. Typical of angiosperms. Differ from sieve cells (PO:0025415), which have less pronounced specialization of sieve areas and no sieve plates.

Tracheary elements are dead at maturity, are more or less elongated, and have pits of various types in the cell wall. Tracheary elements function in the conduction of water and dissolved substances such as mineral nutrients from the roots to the shoot system. Tracheary elements can be distinguished from fiber cells (PO:0025407) by the presence of bordered pits, although there are intermediate forms called fiber tracheids (PO:0000355).

They cause the opening and closing of the pore by changes in turgor.

May have any of the kinds of secondary wall thickenings found in tracheary elements. The area of contact between two tracheids has only bordered pits, whereas in vessel members (PO:0002003), it has openings in the cell wall called perforations, organized into perforation plates (term has been requested in GO).

May have sinuous anticlinal cell walls that overall give a jigsaw like appearance to the epidermis. Pavement cells are epidermal cells that are not directly associated with a stomatal complex or trichome at maturity, but they share similar developmental origins.

Fiber tracheids generally have pointed ends and bordered pits that have lenticular to slit-like apertures. If both libriform fiber cells (PO:0004520) and fiber tracheids are present, the libriform fiber cells usually have thicker walls. Fiber tracheids have bordered pits with smaller pit cavities than the vessel members (PO:0002003) or tracheids (PO:0000301) of the same wood and a distinct pit cavity leading to the cell lumen through the cell wall.

Metaxylem has larger tracheary elements (PO:0000290) than the protoxylem (PO:0000272), and develops after the formation of the protoxylem, once elongation of the plant axis (PO:0025004) has completed.

Functional term

Phloem islands can be formed in the middle of the xylem.

A plant zygote is a whole plant that is a single cell formed by fertilization (syngamy).

If you are annotating to this structure for Zea mays or other grasses, please also add an annotation to the corresponding floret type. Choose the most specific term possible from: spikelet floret (PO:0009082), ear floret (PO:0006354), upper floret of pedicellate spikelet of ear (PO:0006350), upper floret of sessile spikelet of ear (PO:0006352).

This term has been obsoleted to keep the structure simple.

Defined by characteristic morphological, structural, histological or other visible features of a fruit. Includes as subclasses fruit formation stage (PO:0025501) and fruit ripening stage (PO:0025502). May have as part a seed development stage (PO:0001170). This stage applies to an individual fruit. For development stages of a whole plant (PO:0000003) based on fruit development, use whole plant fruit development stage (PO:0025500) or its subclasses.

The initial stage of leaf development when cells in the shoot apical meristem (PO:0020148) are already determined to form a vascular leaf primordium (PO:0000017), but the primordium is not yet morphologically distinguishable.