- CFL: Acronym for "compact
- Chlorosis: The yellowing or
whitening of normally green plant tissue because of a decreased amount of
chlorophyll (Fig 15.1).
- CO2: Chemical symbol for “carbon
- Conductivity: See
- EC: Acronym for "".
- 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.
- Make-up water: Water used during the
process of making a fresh batch of nutrient solution.
- MH: Acronym for "metal
- 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
- NFT: Acronym for "nutrient
- 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
- O2: Chemical symbol for “oxygen”.
Oxidizing agents: For the purpose of this book, this term is used
to describe substances which attack organic material such as bacteria and
- PGR: Acronym for "plant
- 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
- RO: Acronym for "reverse
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
- Top-up water: Extra water added to a
nutrient solution to increase the dilution factor or maintain a desired
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