phloem
Enable an agent to recognise phloem as plant vascular tissue, assess its transport and tissue condition, and judge how observation or intervention may affect source-sink connections.
Research draft, second pass
A second pass drafted this model: the structure a model of this thing needs, and what is known about it in the world. The line under this one says how the second half was obtained - researched against sources, or recalled without web access, in which case nothing here was read anywhere and every claim is a lead to verify. Unreviewed either way.
recalled by Codex without web access - no source was read
Researched by: Codex
Purpose and description
Enable an agent to recognise phloem as plant vascular tissue, assess its transport and tissue condition, and judge how observation or intervention may affect source-sink connections.
Phloem is the vascular tissue of vascular plants that transports sugars and other organic solutes between source and sink tissues through sieve elements, together with associated cells that support transport, storage and sometimes mechanical reinforcement.
It can be Locate and classify phloem using plant context and tissue anatomy.; Map an observed source-sink connection and identify evidence gaps in its continuity or direction.; Select imaging, tracer, or sap-sampling methods appropriate to the plant and the question.; Compare transport and tissue condition across developmental stages, seasons, or treatments.; Assess whether a proposed incision, sampling operation, or girdling treatment would disrupt phloem continuity.; Distinguish evidence of impaired phloem function from symptoms that require whole-plant or disease assessment..
Distinguishing features
Identify sieve elements and their conducting connections; sugar content alone does not establish that tissue is phloem.
Distinguish sieve-tube elements with companion cells in angiosperms from sieve cells and associated cells in other vascular plant groups.
Separate phloem from xylem using cellular anatomy and conductive structures rather than assuming that every vascular tissue transports the same material.
Treat bark as a broader anatomical region that can include secondary phloem; bark and phloem are not interchangeable names.
Distinguish phloem sap from the tissue containing it, and separate identifiable phloem from phloem demonstrated to be actively conducting.
Scope
+ Identification and anatomical boundaries of phloem in roots, stems, leaves, and other vascularised organs
+ Sieve elements, associated support cells, phloem parenchyma, and fibres where present
+ Primary and secondary phloem development, maturation, and functional status
+ Source-sink connections, loading, unloading, and transport through sieve pathways
+ Phloem-specific damage, occlusion, recovery, and constraints on sampling
- Whole-plant taxonomy, geographic range, and conservation assessment
- Xylem anatomy and water transport except where they interact with phloem
- Whole-organ bark, wood, leaf, and root models beyond phloem boundaries
- Whole-plant photosynthesis, growth, and carbon budgeting beyond their source-sink relationships
- Independent models of phloem-feeding organisms, pathogens, and plant diseases
Characteristics
- Plant and organ context
- Host plant identity; organ; developmental stage; anatomical position The expected cell types, arrangement, and source-sink role depend on the plant and the sampled location.
- Developmental origin
- Primary: protophloem or metaphloem; secondary; unresolved Distinguishes tissues formed during primary growth from those produced by vascular cambium.
- Sieve-element organisation
- Sieve-tube elements; sieve cells; unresolved; associated cell types recorded separately Supports identification without imposing angiosperm anatomy on every vascular plant.
- Conducting status
- Conducting demonstrated; conduction undetermined; nonconducting demonstrated; mixed Anatomically recognisable phloem may not currently carry long-distance flow.
- Source-sink connection
- Named source and sink tissues, connecting segment, direction, and observation interval Transport direction must be interpreted for a particular pathway and time rather than assigned universally as downward.
- Loading and unloading route
- Symplastic; apoplastic; mixed; unresolved; loading and unloading assessed separately Transport interfaces differ among species, organs, and developmental conditions.
- Sap solute composition
- Concentration of named sugars, amino acids, and other solutes in mmol/L or other explicitly stated units; collection method required Describes transported material while allowing assessment of contamination and collection bias.
- Transport velocity
- mm/s or cm/h along an identified pathway; method and time window required Quantifies movement without confusing velocity with the total amount of material transported.
- Sieve-element turgor pressure
- MPa; location, method, and whether measured or inferred Helps assess the pressure conditions associated with transport without treating a single pressure reading as proof of flow.
- Occlusion and tissue injury
- Observed callose deposition, protein-associated plugging where applicable, collapse, discontinuity, or no detected lesion; extent and evidence recorded Local sealing or damage can alter transport, but observations require distinction from preparation artefacts.
Where this came from
wikidata · CC0 1.0
Also registered as vr.tr.phloem
Drafted structure
Bundle to layer to finding to question, as the second pass will find it: 5 bundles · 9 layers · 13 findings · 24 questions.
Phloem identity and anatomy Establish what tissue is being called phloem and which anatomical features support that identification.
An agent must distinguish phloem from neighbouring tissues and accommodate different vascular plant anatomies.
Organ location and boundaries
Locate the tissue within a specified plant organ and delimit the observed region.
Delimited phloem region
Record the anatomical evidence defining the phloem region, including its relationship to xylem, cambium where present, and surrounding tissues.
- Which plant, organ, developmental stage, and section orientation define the tissue under examination? provenance
- Which observed boundaries separate this phloem from xylem, cambium, and other tissues included in the specimen? boundary
Sieve and associated cells
Describe the conducting cells and the associated cellular organisation relevant to this plant.
Diagnostic cellular organisation
Identify sieve-element type and associated cells without requiring every phloem region to contain the same cellular complement.
- What evidence identifies sieve-tube elements or sieve cells in this tissue? definition
- Which companion cells, other associated cells, parenchyma, or fibres are observed, and which remain unresolved? measurement
Phloem development and persistence Track developmental origin, maturation, and the distinction between retained tissue and functional conducting tissue.
Phloem identity persists across developmental changes that can substantially alter its transport role.
Primary and secondary origin
Connect the observed phloem to the growth process that produced it.
Developmental assignment
Support assignment to primary or secondary phloem and, where resolvable, to protophloem or metaphloem.
- Does the tissue derive from primary development or vascular cambial activity, and what observations establish this? provenance
- If primary phloem is present, can protophloem and metaphloem be distinguished in this specimen? definition
Maturation and conducting lifetime
Assess maturity and current function separately from tissue age or position.
Functional tissue status
Distinguish developing, conducting, and nonconducting regions using evidence appropriate to the plant and season.
- What evidence shows that the identified sieve elements are mature and currently conducting? measurement
- Does the region contain older, collapsed, or otherwise nonconducting phloem that must be excluded from estimates of active transport area? boundary
Source-sink transport and cargo Describe transport endpoints, loading and unloading interfaces, movement, and transported material.
Phloem function requires a connected pathway and defined cargo; tissue presence or sap chemistry alone cannot establish transport.
Source-sink interfaces
Identify the tissues supplying and receiving transported material during the observation interval.
Supported source-sink pathway
Record the proposed connection and distinguish observed loading and unloading routes from assumptions.
- Which tissues act as source and sink for the specified transported material at this developmental stage and time? boundary
- What evidence supports the assigned loading and unloading routes at the two ends of this pathway? provenance
Flow, cargo, and signals
Characterise movement and composition while distinguishing transported substances from demonstrated signals.
Transport measurements and interpretation
Record velocity, direction, pressure, or solute measurements with their spatial and methodological limits.
- Which measurements establish movement along this phloem pathway, and over what distance and time? measurement
- How were cargo identity and concentration established, and could the collection method introduce material from other tissues? provenance
- For any proposed signalling cargo, what evidence distinguishes transport or detection from a demonstrated response in a receiving tissue? definition
Phloem integrity and intervention Assess transport disruption and select observations or interventions with explicit effects on tissue continuity.
Sampling and damage can change the phloem state being assessed, while similar visible symptoms can have different causes.
Occlusion, injury, and recovery
Evaluate local lesions, sealing responses, and evidence of functional recovery.
Supported transport disruption
Relate observed structural changes to transport impairment without assigning causation from appearance alone.
- What occlusion, collapse, or discontinuity is observed, and how much of the conducting pathway does it affect? measurement
- What evidence distinguishes a pre-existing lesion from wound sealing or artefacts induced by sampling? provenance
- Which follow-up observations would demonstrate restored transport rather than only visible wound closure? action
Sampling and continuity decisions
Match a proposed procedure to the information needed and the pathway it may disturb.
Phloem-aware procedure selection
Specify sampling location, expected disturbance, and the functional inference the procedure can support.
- Which imaging, tracing, or sap-collection procedure can answer the question in this plant, and what limitations affect its interpretation? action
- Would the proposed incision or removal interrupt phloem locally or around the organ circumference, and which source-sink connections could be affected? action
- What controls or baseline observations are needed to separate the procedure's effects from the original phloem condition? measurement
Evidence and external alignment What the world already says about this thing, gathered so the model can be checked against it.
A model that cannot be lined up against existing standards, identifiers and practice cannot be adopted by anyone who already uses them.
Reported evidence
Findings from the breadth pass, kept separate from the structural claims.
Check these first
Recalled without web access and unsourced; every item is a lead to verify.
- This describes a plant tissue, not an organism or taxon; species identifiers and conservation assessments do not apply.
- Cell composition depends on plant lineage: angiosperms typically have sieve-tube elements and companion cells, whereas gymnosperms have sieve cells associated with albuminous cells.
- Transport rates, sap composition and tissue dimensions require species, organ, developmental stage and environmental context; no universal typical ranges are supplied.
- Which of these check these first hold for the sense of phloem this model covers, and on what evidence? provenance
Kinds and varieties
Recalled without web access and unsourced; every item is a lead to verify.
- Primary phloem, derived from procambium
- Secondary phloem, produced by vascular cambium
- Protophloem, the first-formed primary phloem
- Metaphloem, the later-formed primary phloem
- Which of these kinds and varieties hold for the sense of phloem this model covers, and on what evidence? provenance
Real-world use
Recalled without web access and unsourced; every item is a lead to verify.
- Distributes photosynthetic products to growing tissues, roots, fruits, seeds and storage organs.
- Transports signalling molecules involved in coordinating growth and responses to environmental conditions.
- Provides bast fibres used in textiles and cordage, including flax and hemp.
- Informs grafting and girdling practices through its role in transport between shoots and roots.
- Which of these real-world use hold for the sense of phloem this model covers, and on what evidence? provenance
Failure modes and hazards
Recalled without web access and unsourced; every item is a lead to verify.
- Girdling interrupts phloem transport and can starve roots, eventually killing a woody plant.
- Phloem-feeding insects remove sap and can transmit plant pathogens.
- Phloem-limited pathogens, including phytoplasmas, can disrupt growth and assimilate distribution.
- Wounding triggers sieve-element sealing, which limits sap loss but interrupts transport locally.
- Drought can impair transport through changes in water availability, pressure gradients and sap viscosity.
- Which of these failure modes and hazards hold for the sense of phloem this model covers, and on what evidence? provenance
Neighbouring kinds and how to tell them apart
Recalled without web access and unsourced; every item is a lead to verify.
- xylem - Xylem conducts water and mineral nutrients mainly through cells that are dead at functional maturity; phloem conducts organic solutes through living sieve elements.
- bark - Bark comprises tissues outside the vascular cambium in woody stems and roots; secondary phloem is one component of bark.
- sieve element - A sieve element is a conducting cell within phloem; phloem is the tissue containing those cells and associated cell types.
- vascular cambium - Vascular cambium is a lateral meristem that produces secondary phloem outward and secondary xylem inward.
- phloem sap - Phloem sap is the transported fluid; phloem is the tissue through which it moves.
- Which of these neighbouring kinds and how to tell them apart hold for the sense of phloem this model covers, and on what evidence? provenance
What the second pass must settle
- Which existing Vercy world model, if any, already owns phloem or vascular tissue, and should this registry entry link to it?
- Which authoritative references should establish anatomical terminology and associated-cell distinctions across the vascular plant groups covered?
- What evidence and thresholds should qualify a phloem region as conducting, impaired, or nonconducting for each plant and observation method?
- Which sampling methods yield interpretable sap composition and pressure measurements in the target plants, and how should their biases be recorded?
- How should species-specific seasonal changes, loading strategies, and reversible occlusion be represented without treating one plant's behaviour as universal?