Dew Point

A measure of the amount of moisture within the air. It is the temperature of the air to what it has to be cooled to when it is saturated with water vapour. If air is in contact with a surface which is cooler than the air temperature, then water vapour will condense on that surface to form dew. A high dew point indicates that there is a high amount of moisture present.

  Dicotyledon

The name for one of the two former groups (the other being Monocotyledon) into which Angiosperms were categorized. However, the Angiosperm Phylogeny Group (AGP) has determined by molecular analysis that not all of the plants previously placed within the dicotyledon group had a common ancestor. The majority of dicotyledons are now classified in the Eudicot Clade. See Eudicots for typical dicotyledon characteristics.

  Dihydrogen Sulphate

An alternative name for sulphuric acid, H2SO4. It is used, for example, in the Quadrop System.

  Dioecious

A plant that has either male or female flowers on a separate plant, not both together on the same plant. Examples of dioecious plants include Holly (Ilex aquifolium), Yew (Taxus baccata), Poplars (Populus sp.), Willows (Salix sp.), and Common Ash (Fraxinus excelsior).

  Disorder

A feature or condition, especially environmental one, which affects and harms a turfgrass plant. Extreme or unsuitable growing conditions can create plant stress, which can result in disease-like symptoms, plant discolourations, unusual growth, or plant death. A disorder is not a direct result of disease or pest damage to leaves of roots, although in some cases it is a consequence of a secondary action from the presence of an organism, for example, animal urine will typically scorch a sward, often killing the leaves and in some cases killing off grass roots as well. A light forking and a thoro

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  Dispersant

A substance in suspension which helps to deflocculate and cleanse a contaminated soil.

  Dissociation

The breaking down of soil compounds into its individual parts when dissolved in water. Anions and cations can therefore be produced from the breaking up of a compound. These are then available for plant growth, being taken up from the soil solution in which they are present. Dissociation can result in an increase or decrease in soil pH, depending on whether the material releases hydrogen ions (H+) which will increase acidity, or hydroxide ions (OH-) which will reduce soil acidity, which can also be thought of as starting to neutralise acid soils. The dissociation process is influenced b

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  Distinctness

Plant Breeders have rights of protection over plant varieties they develop, and a variety must have distinct primary, and where required secondary characteristics, such as ploidy; Intensity of green colour of leaf; Numbers of tiller; and many more.

  Division

A taxonomic category that is used to group organisms: It is now more often referred to as a Phylum in botany. They are grouped from a similar Class. Similar Divisions or Phyla are in turn grouped into a Kingdom.

  Domain

The highest taxonomic category for a group of organisms in the three-domain system proposed by Carl Woese. The domains are Archaea, Bacteria and Eukarya. It is also referred to as Superkingdom.