indexed terms
Teaching Healthy Cultivation · Reference
Plant Science Glossary
Use the same vocabulary across lessons, diagnostic cases, plant-health references, and field observations. Definitions describe the term itself; visible symptoms such as chlorosis or necrosis are not treated as diagnoses.
subject categories
aliases and abbreviations
77of 77 terms
Plant signalingAlso: ABA
Abscisic acid (ABA)
A plant hormone involved in stress responses, seed dormancy, stomatal regulation, and coordination of water-conservation responses.
Plant health
Abiotic stress
Plant stress caused by nonliving factors such as heat, cold, drought, excessive water, salinity, light, or chemical injury rather than by a pest or pathogen.
Plant physiology
Acclimation
A reversible adjustment in plant structure or physiology that develops after exposure to a changed environment.
Plant architecture
Apical dominance
The tendency of an actively growing shoot tip to suppress or reduce growth of axillary buds below it, largely through coordinated hormone signaling.
Plant anatomyAlso: shoot apical meristem, SAM
Apical meristem
A region of actively dividing cells at a shoot or root tip that produces new primary growth and developing organs.
Plant signaling
Auxin
A class of plant hormones involved in cell expansion, apical dominance, tropisms, vascular development, rooting, and many other developmental processes.
Genetics & reproductionAlso: day-neutral cannabis
Autoflower
A common horticultural term for cannabis with day-neutral flowering behavior, meaning floral development is less dependent on a short-day photoperiod trigger than in typical photoperiod cultivars.
Plant health
Biosecurity
Practices designed to reduce the introduction and spread of pests, pathogens, contaminated plant material, and other biological hazards.
Plant health
Biotic stress
Plant stress caused by living organisms such as insects, mites, fungi, bacteria, viruses, viroids, or other biological agents.
Plant anatomy
Bract
A modified leaf associated with a flower or inflorescence. In female cannabis flowers, bracts surround reproductive structures and can carry dense glandular trichomes.
Plant chemistryAlso: phytocannabinoid
Cannabinoid
A class of specialized compounds that includes phytocannabinoids produced by Cannabis, many of which accumulate in glandular trichome secretions.
Root zoneAlso: CEC
Cation exchange capacity (CEC)
A measure of a material's capacity to retain and exchange positively charged ions. It influences how soils and some substrates buffer nutrient cations.
Plant physiology
Chlorophyll
A group of green pigments that absorb light energy used in photosynthesis.
DiagnosticsAlso: yellowing
Chlorosis
Loss or reduction of normal green coloration caused by reduced chlorophyll or impaired chlorophyll development. Chlorosis is a symptom, not a diagnosis.
Plant health
Chilling stress
Physiological stress caused by low, nonfreezing temperatures that impair temperature-sensitive plant processes.
Seed biologyAlso: seed leaf
Cotyledon
An embryonic seed leaf that supports early seedling development and can contribute stored reserves and early photosynthesis.
Genetics & reproduction
Cultivar
A cultivated plant variety selected and maintained for particular characteristics. A cultivar name does not guarantee that every individual plant is phenotypically identical.
LightAlso: DLI
Daily light integral (DLI)
The total amount of photosynthetically active photons delivered to a surface over a day, usually expressed as moles of photons per square meter per day.
Genetics & reproductionAlso: autoflowering
Day-neutral flowering
Flowering behavior in which floral initiation is comparatively less dependent on day length than in obligate or strongly photoperiod-sensitive plants.
Genetics & reproduction
Dioecious
A reproductive system in which male and female flowers normally occur on separate individual plants.
Root zone
Dryback
The decrease in substrate water content between irrigation events. Its interpretation depends on substrate, container, root occupancy, climate, and measurement method.
Root zoneAlso: EC
Electrical conductivity (EC)
A measure of a solution's ability to conduct electrical current that is commonly used as an indirect indicator of total dissolved ionic concentration.
Plant healthAlso: oedema
Edema
A physiological disorder in which water uptake and tissue hydration exceed the capacity for normal water loss or tissue accommodation, producing blister-like or corky injury in susceptible tissues.
Plant physiology
Etiolation
A pattern of elongated, pale, weak growth associated with development under insufficient light or darkness.
Water relationsAlso: ET
Evapotranspiration
The combined movement of water to the atmosphere through evaporation from surfaces and transpiration from plants.
Genetics & reproduction
Fertilization
Fusion of male and female gametes that initiates embryo development. Pollen contact alone is not the same as successful fertilization.
Genetics & reproduction
Feminized seed
Cannabis seed produced through breeding methods intended to strongly favor female offspring rather than the approximately mixed-sex outcome expected from many conventional male-by-female crosses.
Genetics & reproduction
Genotype
The genetic constitution of an organism. Observed traits arise from genotype interacting with development and environment.
Seed biology
Germination
The sequence by which a viable seed resumes metabolism and embryo growth under suitable conditions, commonly culminating in radicle emergence.
Plant signalingAlso: GA
Gibberellin
A class of plant hormones involved in processes including stem elongation, seed germination, developmental transitions, and reproductive growth.
Plant anatomy
Glandular trichome
A specialized epidermal structure with secretory cells that produces and stores specialized metabolites. Cannabis inflorescences carry abundant glandular trichomes.
Water relations
Guttation
Release of liquid water droplets from specialized leaf structures, typically driven by root pressure under conditions of low transpiration. It is distinct from dew condensation.
Propagation
Hardening off
A gradual acclimation process used before moving plants into a more demanding environment, allowing physiology and structure to adjust to changed light, wind, temperature, or humidity.
Plant healthAlso: HLVd
Hop latent viroid (HLVd)
A small infectious RNA viroid that can infect cannabis and is associated with reduced vigor, altered development, and crop-quality losses. Laboratory testing is important because symptoms are not reliably diagnostic by appearance alone.
Root zoneAlso: low oxygen
Hypoxia
A condition in which oxygen availability is below the level needed to support normal tissue function. In root zones, persistent saturation can slow oxygen replenishment and impair respiration.
Seed biology
Imbibition
Initial water uptake by a dry seed, rehydrating tissues and enabling metabolic processes associated with germination to resume.
Plant anatomy
Inflorescence
A flowering shoot system or cluster containing flowers and their supporting structures.
Plant healthAlso: IPM
Integrated pest management (IPM)
A decision framework that combines prevention, monitoring, correct identification, thresholds or action criteria, and compatible cultural, biological, physical, and chemical controls.
Plant anatomy
Internode
The stem segment between two adjacent nodes. Internode length contributes to plant height, branch spacing, canopy density, and the visible architecture produced during development.
Environment
Leaf temperature
The temperature of leaf tissue, which can differ from surrounding air temperature because of radiation, airflow, conduction, and evaporative cooling.
Plant anatomy
Meristem
Plant tissue containing actively dividing, relatively undifferentiated cells that generate new growth and organs.
Environment
Microclimate
The environmental conditions immediately around a plant or within a canopy zone, which can differ from a room-level or weather-station measurement.
Root zoneAlso: mycorrhizal association
Mycorrhiza
A symbiotic association between certain fungi and plant roots in which both partners can exchange resources. Effects depend on plant, fungal species, root-zone conditions, and management.
Diagnostics
Necrosis
Death of plant cells or tissues, visible as dead, dry, collapsed, or discolored areas. Necrosis describes damage and does not identify its cause.
Plant anatomy
Node
A position on a stem where leaves, buds, branches, or reproductive structures can originate.
Water relations
Osmotic stress
Stress caused when a low external water potential makes it harder for roots or cells to acquire water, as can occur during drought or high dissolved-salt conditions.
Genetics & reproduction
Ovule
A structure within the ovary that contains the female gametophyte and can develop into a seed after successful fertilization.
LightAlso: photosynthetically active radiation
PAR
Photosynthetically active radiation, conventionally the 400–700 nanometer waveband used when describing photons available for photosynthesis.
Root zone
pH
A logarithmic measure related to hydrogen-ion activity. Root-zone pH influences chemical speciation, nutrient availability, and biological processes but is not itself a nutrient concentration measurement.
Genetics & reproduction
Phenotype
The observable characteristics of an organism produced by interactions among genotype, development, environment, and history.
Plant anatomy
Phloem
Living vascular tissue that distributes sugars and other transported compounds among source and sink tissues.
Light
Photoinhibition
A reduction in photosynthetic efficiency that occurs when absorbed light exceeds the capacity of photosynthetic systems to use or safely dissipate that energy.
Light
Photoperiod
The duration and timing of light and darkness within a repeating day-night cycle.
Plant physiology
Photosynthesis
The set of processes by which plants capture light energy and use it to support carbon fixation and chemical energy storage.
LightAlso: photosynthetic photon flux density
PPFD
Photosynthetic photon flux density: the rate at which photons in the photosynthetically active waveband arrive at a surface, usually expressed as micromoles per square meter per second.
Seed biology
Radicle
The embryonic root, commonly the first root organ to emerge during germination.
EnvironmentAlso: RH
Relative humidity (RH)
The amount of water vapor in air expressed relative to the maximum amount that air could hold at the same temperature before saturation.
Root zone
Rhizosphere
The zone of soil or substrate directly influenced by roots, root exudates, microorganisms, water, gases, and nutrient exchange.
Root zone
Root hair
A short-lived extension of a root epidermal cell that increases contact between the root and its surrounding water, nutrients, and substrate.
Plant healthAlso: salt stress
Salinity stress
Physiological stress associated with excessive dissolved salts, which can create osmotic difficulty and specific ion imbalances or toxicity depending on composition and exposure.
Plant health
Sanitation
Cleaning and hygiene practices used to reduce contamination, pest reservoirs, pathogen spread, and movement of unwanted biological material.
Plant physiology
Senescence
A regulated developmental process in which tissues age and resources may be remobilized before tissue death or abscission.
Genetics & reproductionAlso: intersex expression
Sex-expression plasticity
The capacity for reproductive expression to vary with genotype, development, hormonal signaling, or environmental context rather than behaving as an absolutely fixed visible trait.
Plant physiologyAlso: source sink
Source–sink relationship
The relationship between tissues that export assimilates or resources and tissues that import them for growth, metabolism, storage, or reproduction.
Genetics & reproduction
Stigma
The receptive part of a flower's pistil on which compatible pollen can land and germinate.
Plant anatomyAlso: stoma
Stomata
Microscopic pores, mainly in the epidermis of leaves and other aerial tissues, whose guard cells regulate gas exchange and water-vapor loss.
Root zoneAlso: growing medium, media
Substrate
The physical medium surrounding roots in a container or cultivation system. Its pore structure, water retention, aeration, chemistry, and biology affect root-zone function.
Root zone
Taproot
A dominant primary root that develops from the radicle and may remain prominent while lateral roots branch from the root system.
Water relations
Transpiration
Loss of water vapor from plant tissues, predominantly through stomata, coupled to water transport through the plant and influenced by environmental and physiological conditions.
Plant anatomy
Trichome
An epidermal outgrowth such as a hair or gland. Cannabis carries both glandular and nonglandular trichome types with different structures and functions.
Water relationsAlso: turgor pressure
Turgor
Pressure generated when water inside plant cells pushes the cell membrane and contents against the cell wall, contributing to tissue rigidity and growth.
EnvironmentAlso: VPD
Vapor pressure deficit (VPD)
A measure of the difference between the vapor pressure at saturation and the actual vapor pressure. In plant work, leaf temperature and air humidity are important to interpreting the leaf-to-air vapor-pressure gradient.
Plant health
Viroid
A small infectious circular RNA molecule that lacks a protein coat and can cause disease in susceptible plants.
PostharvestAlso: aw
Water activity
A measure of the energy status or effective availability of water in a material relative to pure water, used to understand moisture-dependent chemical and microbial behavior.
Water relations
Water potential
A thermodynamic measure describing the potential energy of water and the direction in which water tends to move between connected regions.
Plant health
Waterlogging
Persistent saturation of a root zone that fills pore space with water, restricts gas exchange, and can create root hypoxia.
Plant anatomy
Xylem
Vascular tissue that conducts water and dissolved mineral nutrients primarily from roots toward aerial tissues and also contributes structural support.
Reference policy
Definitions support reasoning; they do not replace diagnosis.
Terms are written to preserve distinctions that matter in plant science—for example, EC is not a direct nutrient assay, pollen contact is not fertilization, relative humidity is temperature-dependent, and a symptom name does not identify a cause.