dATP Deoxyadenosine 5'-triphosphate.

dCTP Deoxycytidine 5'-triphosphate.

de novo Literally, 'from a new [beginning]' (Latin). (1) With reference to plant regeneration or developmental processes: arising from unorganized cells or tissues or from prodetermined cells. See also adventitious. (2) In molecular biology: not requiring a primer.

deferment Postponement or delay of grazing on an area, to achieve a specific management objective (e.g., to provide time for plant reproduction, establishment of new plants, restoration of plant vigor, a return to environmental conditions appropriate for grazing, or accumulation of forage for later use).

deferred grazing The deferment of grazing in a nonsystematic rotation with other land units.

degermed corn Grain (corn) from which the embryo (germ) has been removed.

dehumidification The process by which water is removed from a substance; used specifically of moisture vapor removed from air.

delayed-release fertilizerSee slow-release fertilizer.

denaturation (1) The breakdown of the secondary or tertiary structure of a protein or nucleic acid by physical or chemical means. (2) More specifically, the conversion of a double-stranded nucleic acid to the single-stranded state by destruction of the hydrogen bonds maintaining the double-stranded state. Compare renaturation.

density, shootSee shoot density.

deoxynucleotidyl transferaseSee terminal transferase.

desert Land on which the vegetation is absent or sparse, is usually shrubby, and is characterized by an arid climate, hot to cool.

detassel To remove, by cutting or pulling, the tassels that bear staminate flowers in order to prevent selfing during hybrid seed production of corn.

dethatch The procedure of removing an excessive thatch accumulation either (i) mechanically, as by vertical mowing, or (ii) biologically, as by topdressing with soil.

developmental stage Discrete portion of the life cycle of a plant, such as vegetative growth, reproduction, or senescence. Several published systems are in use for various crops to subdivide the broad stages. Usage: Preferred to growth stage (except when growth stage is part of the name of a published system). See also bloom, early; bloom, full; bloom, late; boot stage; grain maturity.

DFP Diisopropyl fluorophosphate.

dGMP Deoxyguanosine 5'-monophosphate.

diallelicSee balanced diallelic; unbalanced diallelic.

differential centrifugation A method of separating subcellular particles by centrifuging cell extracts at successively higher speeds. Separation is based on differences in sedimentation coefficients that are roughly proportional to particle size. Large particles (e.g., nuclei, chloroplasts, or mitochondria) are sedimented at lower speeds than small particles (e.g., ribosomes).

differentiation The process of biochemical and structural changes by which cells become specialized in form and function.

differentiation 2 The process leading to differences in the amount, character, and location of cellular components, cells, tissues, and organs of an organism: specialization physically, chemically, physiologically, and morphologically. In particular, the maturation of a cell with unique traits (e.g., a xylem vessel), different from the meristematic cells from which it arose and different from other cells of similar age that followed a different course. Compare development. See also Part II.

digestibility, dry matterSee in vitro dry matter disappearance.

digestible dry matter Feed intake minus feces expressed as a percent of feed dry matter consumed.

digestible energy intake Feed consumption expressed as units of digestible energy.

digestible protein Feed protein minus feces portion (nitrogen x 6.25) expressed as a percentage of amount in feed.

diploid (1) Characterizing a cell in which all chromosomes, except sex chromosomes, are two in number and are structurally identical within the limits of detection with those of the species from which it was derived. (2) Such a cell or organism. See also -ploid.

direct repeat Two or more regions of DNA that have identical (or nearly identical) nucleotide sequences in the same orientation within one DNA molecule. Direct repeats may be either contiguous or separated on the same molecule. Compare inverted repeat.

dirty seedUsage: For tall fescue seed, endophyte-infected seed is the preferred term.

divot A small piece of turf severed from the soil by a golf club or the twisting-turning action of a cleated shoe.

DNA polymerase One of several enzymes that synthesize a new DNA strand complementary to a template strand by adding nucleotides one at a time to a 3'-OH end. See also polymerase chain reaction.

DNase Deoxyribonuclease: Any enzyme that degrades DNA, including endonucleases and exonucleases.

dNTP deoxynucleoside 5'-triphosphate.

dormant seeding Planting seed during late fall or early winter after temperatures become too low for seed germination to occur until the following spring.

dormant turf Turfs that have temporarily ceased shoot growth as a result of extended drought, heat, or cold stress.

dry matter The substance in a plant remaining after oven drying to a constant weight at a temperature slightly above the boiling point of water.

dry matter disappearance (1) Grazing: Forage present at the beginning of a grazing period plus growth during the period minus forage present at the end of the period. (2) Digestibility: Loss in dry weight of forage exposed to in vitro digestion.

dry millingSee milling, dry.

dry weight Moisture-free weight.

dTDP Thymidine 5'-diphosphate.

dTTP Thymidine 5'-triphosphate.

dUTP Deoxyuridine 5'-triphosphate.