- CFL: Acronym for "compact fluorescent”.

- Chlorosis: The yellowing or whitening of normally green plant tissue because of a decreased amount of chlorophyll.

- CO2: Chemical symbol for “carbon dioxide”.

- Conductivity: See EC.

- EC: Acronym for "electrical conductivity".

- Ground water: Under-ground water deposit e.g. artesian bore.

Hardness (or “hard”).

- HID: Acronym for "high intensity discharge" lamp.

- HPS: Acronym for "high pressure sodium" lamp.

Inorganic nutrient

- Make-up water: Water used during the process of making a fresh batch of nutrient solution.

- MH: Acronym for "metal halide" lamp.

- Mottling: Spots or blotches of different shades or colors commonly found on leaves.

- mS: Short-hand representation of "mS/cm".

- Natural water: Water supply that is uncontaminated by pollution.

- Necrosis: Death of plant cells resulting in dead/brown spots on foliage (Fig 15.1).

- NFT: Acronym for "nutrient film technique".

- Nutrient solution: The diluted nutrient that is fed to plants. It is usually comprised of a nutrient concentrate, water and nutrient additives. For the purpose of clarity, the nutrient solution is sometimes referred to as the "working nutrient solution".

- O2: Chemical symbol for “oxygen”.

Organic nutrient.

Oxidizing agents: For the purpose of this book, this term is used to describe substances which attack organic material such as bacteria and viruses.


- PGR: Acronym for "plant growth regulator".

- ppm: Acronym for "parts per million”. “ppm” has the same meaning or numerical value as “mg/L”.


- Precipitate (or “precipitation”): Insoluble solid deposit that forms within a nutrient solution or water which eventually sinks to bottom of reservoir or adheres to sidewalls.

- Recirculating nutrient (or “recirculating system”): The process (or system) where the working nutrient solution is recirculated.

Respiration (or “respire”).

- RH: Acronym for "relative humidity".

- RO: Acronym for "reverse osmosis".

Run-to-waste: Type of growing system or method.

- Saline (or “salinity” / “salty”): A water that contains excessive salt levels - usually sodium chloride.

- Scheme water: Water supply provided by a local authority.

- Surface water: Above-ground water deposit e.g. river, stream, lake, dam, soak.

- TDS: Acronym for "total dissolved salts".

- Top-up water: Extra water added to a nutrient solution to increase the dilution factor or maintain a desired level.

Transpiration (or “transpire”)

- Wilt (or “wilting”): The drying out, drooping, and withering of the leaves of a plant due to inadequate water supply, excessive transpiration, or vascular disease.

- Working nutrient solution: See "nutrient solution".

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