Tissue Culture Glossary

Abaxial – On the side that is away from the axis or central line, usually on the underside of the explant – See here.
Abscisic AcidABA. A plant growth regulator involved in abscission, dormancy, stomatal opening/closure, and inhibition of seed germination. It also affects the regulation of somatic cell embryogenesis in some plant species.
Activated Charcoal – Charcoal which has been treated to remove hydrocarbons and to increase its adsorptive properties/
Adaxial – On the side that is towards the axis or central line, usually on the upper side of the explant – See here.
Adventitious Bud – Buds that develop in places other that at the end of a twig or in leaf axils. They appear when wounding stimulates their development.
Agar – A polysaccharide solidifying agent used in nutrient media preparations and obtained from certain types of red algae (Rhodophyta). Both the type of agar and its concentration can affect the growth and appearance of cultured explants
Antibiotic – Any chemical or biological agent that harms the growth of micro-organisms.
Apomixis – Replacement of the normal sexual reproduction by asexual reproduction, without fertilization. Thus “normal asexual reproduction” of plants, such as propagation from cuttings or leaves, has never been considered to be apomixis, but replacement of the seed by a plantlet, or replacement of the flower by bulbils are types of apomixis. Apomictically produced offspring are genetically identical to the parent plant.
Aseptic – The state of being free of contaminating organisms (bacteria, fungi, algae, and all micro-organisms except viruses). See Sterile.
Autoclave – 1. An enclosed chamber in which substances are heated under pressure to sterilize utensils, liquids, glassware, etc., using steam. The routine method uses steam pressure of 103.4×103 Pa at 121°C for 15 minutes, or longer to allow large volumes to reach the critical temperature.
2. A pressure cooker used to sterilize growth medium and instruments for tissue culture work.
Auxin – A group of plant growth regulators (natural or synthetic) that stimulate cell division, enlargement, apical dominance, root initiation, and flowering.
Axillary bud – when located in the axil of a leaf (lateral is equivalent but some adventitious buds may be lateral too)

Bleach – A fluid, powder or other whitening (bleaching) or cleaning agent, usually with free chlorine ions. Commercial bleach contains calcium hypochlorite or sodium hypochlorite and is a common disinfectant used for cleaning work surfaces, tools, and plant materials in plant tissue culture and grafting.
Bleeding – Used to describe the occasional purplish-black coloration of media due to phenolic products given off by (usually fresh) transfers.
Bud – An undeveloped or embryonic shoot and normally occurs in the axil of a leaf or at the tip of the stem. Once formed, a bud may remain for some time in a dormant condition, or it may form a shoot immediately.

Callus – A mass of thin-walled, undifferentiated plant cells, developed as the result of culture on nutrient media.
Cell Differentiation – Continuous loss of physiological and cytological characters of young cells, resulting in getting the characters of adult cells. The unspecialized cells become modified and specialized for the performance of specific functions. Differentiation results from the controlled activation and de-activation of genes.
CharcoalSee Activated Charcoal
Clone – Group of plants genetically identical in which all are derived from one selected individual by vegetative or in-vitro propagation, without the sexual process.
Cultivar – A category of plants that are, firstly, below the level of a sub-species taxonomically, and, secondly, found only in cultivation. It is an international term denoting certain cultivated plants that are clearly distinguishable from others by stated characteristics and that retain their distinguishing characters when reproduced under specific conditions.
Culture MediumSee Medium
Cutting – A detached plant part that under appropriate cultural conditions can regenerate the complete plant without a sexual process.
Cytokinin – Plant growth regulators (hormones) characterized as substances that induce cell division and cell differentiation (e.g., BAP, kinetin, and 2-iP). In tissue culture, these substances are associated with enhanced callus and shoot development.
Differentiation – A process in which unspecialized cells develop structures and functions characteristic of a particular type of cell. Development from one cell to many cells, accompanied by a modification of the new cells for the performance of particular functions. In tissue culture, the term is used to describe the formation of different cell types.

Disinfection – Full elimination of internal micro-organisms from a culture.
Distal – The side of an explant furthest from the point of attachment (i.e. the tip of a leaf)
Donor Plant – An explant, graft, or cutting used as a source of plant material for micro-propagation purposes.

Established Culture – An aseptic viable explant.
Ethanol – C2H6O, Commonly used to disinfest plant tissues, glassware utensils, and working surfaces in tissue culture manipulations. The concentration used is 70% (v/v) for disinfecting and 95% (v/v) when flaming tools.
Excision – Cutting out and preparing a tissue, organ, etc., for culture.
Explant – Tissue aseptically obtained and prepared from the donor plant for culture(flower stalk, leaves, roots)
Exponential phaseSee Logarithmic phase
Ex Vitro – Organisms removed from tissue culture and transplanted; generally plants to soil or potting mixture.
Filter Sterilization – Process of sterilizing a liquid by passage through a filter with pores so small that they prevent the passage of micro-organisms and microbial spores.
Flaming – A technique for sterilizing instruments. The instrument is dipped in alcohol (usually 95% (v/v) ethanol) and then the alcohol on the instrument is ignited, thus heat-sterilizing the tool surface.
FormulationSee Medium
Fungicide – An agent, such as a chemical, that kills fungi.

Gelatin – A glutinous, proteinaceous gelling and solidifying agent. Occasionally used in place of agar in tissue culture.
Gibberellins – Plant growth regulators involved in elongation, enhancement of flower, fruit and leaf size, germination, vernalization, and other processes.

Hardening off – Adapting plants to outdoor conditions by gradually withholding water, lowering the temperature, increasing light intensity, or reducing the nutrient supply. The hardening-off process conditions plants for survival when transplanted outdoors. The term is also used for gradual acclimatization to in vivo conditions of plants grown in vitro, e.g., a gradual decrease in humidity. cf acclimatization; free-living conditions.
HEPA Filter – (high-efficiency particulate air filter) A filter capable of screening out particles larger than 0.3 µm. HEPA filters are used in laminar air flow cabinets (hoods) for sterile transfer work.
Hormone – A specific organic product, produced in one part of a plant, and transported to another part where, at low concentrations, it promotes, inhibits or quantitatively modifies a biological process.
Hypochlorite – Generic term for aqueous solutions of sodium hypochlorite, potassium hypochlorite or calcium hypochlorite, which are oxidizing agents and used for disinfecting surfaces and surface-sterilizing tissues, and for bleaching.

Initiation – Early steps or stages of a tissue culture process (culture growth, organogenesis, embryogenesis)
Inoculum – A small piece of tissue cut from callus, or an explant from a tissue transferred into fresh medium for the continued growth of the culture.
Inositol – C6H6(OH)6, A water-soluble nutrient frequently referred to as a “vitamin” in plant tissue culture.
In vitro – Living in test tubes, outside the organism or in an artificial environment, typically in glass vessels in which cultured cells, tissues, or whole plants may reside.
In vivo – The natural conditions in which organisms reside. Refers to biological processes that take place within a living organism or cell under normal conditions.

Kinetin – One of the cytokinins, a group of growth regulators that characteristically promote cell division in plants.
Kinin – A substance promoting cell division. In plant systems, the prefix cyto- has been added (cytokinin) to distinguish it from kinin in animal systems. See cytokinin.

Lag phase – The initial growth phase after inoculation, during which cell number remains relatively constant, prior to rapid growth.
Laminar Flow Hood – Cabinet for inoculation of cultures. The working area is kept sterile by a continuous, non-turbulent flow of sterilized air through a HEPA filter. See HEPA filter
Log phaseSee Logarithmic phase
Logarithmic phase – The steepest slope of the growth curve; the phase of vigorous growth, during which cell number doubles every 20-30 minutes.
Longitudinal edge – The direction parallel to the ridge, following the greatest length of an area or object.

Macronutrient – For growth media: an essential element normally required in concentrations >0.5 millimole/l.
MediaSee Medium
Medium – In plant tissue culture, a term for the liquid or solidified formulation upon which plant cells, tissues or organs develop.
Medium Formulation – Medium formulation In tissue culture, the particular formula for the culture medium. It commonly contains macro-elements and micro-elements, some vitamins (B vitamins, inositol), plant growth regulators (auxin, cytokinin, and sometimes gibberellin), a carbohydrate source (usually sucrose or glucose), and often other substances, such as amino acids or complex growth factors. Media may be liquid or solidified with agar; the pH is adjusted (ca. 5-6) and the solution is sterilized (usually by filtration or autoclaving). Some formulations are very specific in the kind of explant or plant species that can be maintained; some are very general.
Meristem – Undifferentiated tissue, the cells of which are capable of active cell division and differentiation into specialized and permanent tissue such as shoots and roots.
Micronutrient – For growth media: An essential element normally required in concentrations < 0.5 millimole/litre.
Mother plantSee Donor plant
Myo InositolSee Inositol
MS – Murashige and Skoog media

Nutrient mediumSee Medium

Organized tissue – Composed of regularly differentiated cells.

pH – A measure of acidity and alkalinity. Equal to the log of the reciprocal of the hydrogen ion concentration of a solution, expressed in grams per liter. A reading of 7 is neutral (e.g., pure water), whereas below 7 is acid and above 7 is alkaline.
Phenolic Exudation – Many plant species contain phenolic compounds that blacken through exudation. The process is initiated after plants are wounded. Phenolic exudation may lead to growth inhibition or, in severe cases, to tissue necrosis and death. Antioxidants are incorporated into the sterilizing solution or isolation medium to prevent or reduce exudative browning (activated charcoal).
ppm – Parts per million.
PPM – Plant Preservative Mixture – a broad-spectrum biocide/fungicide for plant tissue culture.
Propagule – Any structure capable of giving rise to a new plant by asexual or sexual reproduction, including seeds, leaves, buds, etc.
Proximal – The side of an explant closest to the point of attachment (i.e. the base of a leaf)

Radicle – That portion of the plant embryo which develops into the primary or seed root.

Scarification – The chemical or physical treatment given to some seeds (where the seed coats are very hard or contain germination inhibitors) in order to break or weaken the seed coat sufficiently to permit germination.
Semi-solid – Gelled but not firmly so; small amounts of a gelling agent are used to obtain a semi-solid medium; called also semi-liquid.
Spore – A small, protected reproductive form of a micro-organism, often synthesized when nutrient levels are low.
Stationary phase – The plateau of the growth curve after log growth, during which cell number remains constant. New cells are produced at the same rate as older cells die.
Sterile – Medium or object with no perceptible or viable micro-organisms.
Sterilize – The process of elimination of micro-organisms, such as by chemicals, heat, irradiation or filtration.
Sub-culture – Division and transfer of a portion or inoculum of a culture to fresh medium. Sometimes used to denote the adding of fresh liquid to a suspension culture.

Terminal bud – when located at the tip of a stem (apical is equivalent but rather reserved for the one at the top of the plant)
Tissue culture – A general term used to describe the culture of cells, tissues, or organs in a nutrient medium under sterile conditions
Transverse – Across the width of the explant, the direction perpendicular to the ridge, the perpendicular side of the longitudinal side.

Undefined medium – A medium or substance added to medium in which not all of the constituents or their concentrations are chemically defined, such as media containing coconut milk, malt extract, casein hydrolysate, fish emulsion, or other complex compounds.
Undifferentiated – Lacking the specialized or differential gene expression characteristic of specialized cells.
Vessel – A container, such as a Petri dish, jar, baby food jar, or test tube, used for tissue culture.

Viability – The capability to live and develop normally.
Viable – Capable of germinating, living, growing, and developing.

w/v – Weight per volume; the weight of a constituent in 100 cm3 of solution, expressed as a percentage.

Zone of elongation – The section of the young root or shoot just behind the apical meristem, in which the cells are enlarging and elongating rapidly.

Majority of glossary terms sourced from http://www.fao.org FAO RESEARCH AND TECHNOLOGY PAPER No. 7