Glossary of Crop Science Terms - Browse
NAD(P)+ Either NAD+ (oxidized nicotinamide-adenine dinucleotide) or NADP+ (oxidized nicotinamide-adenine dinucleotide phosphate).
NAD+ Oxidized nicotinamide-adenine dinucleotide.
NADP+ Oxidized nicotinamide-adenine dinucleotide phosphate.
nap (1) Fuzzy or protruding fibers on the surface of a finished fabric or material. (2) Large masses of curled and more or less loosely matted fibers found in raw cotton.
native species A species indigenous to an area; i.e., not introduced from another environment or area.
naturalized plants Introduced species that have become established in a region. Compare native or indigenous.
NDP Nucleoside 5'-diphosphate.
near-isogenic lines Two distinct composites of F3 lines from a single cross, one consisting of lines homozygous recessive and the other consisting of lines homozygous dominant for specific genes. That is, the paired composite lines have the same genetic background, differing only in being homozygous dominant vs. recessive for the specific genes.
net assimilation rate See assimilation.
neutral-detergent fiber Neutral-detergent insoluble residue, primarily cell-wall constituents. Abbr.: NDF.
nick A break in DNA. More specifically, the absence of a phosphodiester bond between adjacent nucleotides in one of the two strands of a DNA duplex.
nick 2 (1) The state or condition in which two parents for producing hybrid seed mate well to produce superior yields or progeny. (2) See also Part II.
nitrate toxicity A variety of conditions in animals, resulting from ingestion of feed high in nitrate; the toxicity actually results when nitrate (NO3) is reduced to nitrite (NO2) in the rumen.
nitrocellulose A nitrated derivative of cellulose that is made into membrane filters of defined porosity (e.g., 0.45 (m, 0.22 (m). These filters have a variety of uses in molecular biology, particularly in nucleic acid hybridization experiments, in which the nucleic acids are transferred from an agarose gel to a nitrocellulose filter. Synonym: cellulose nitrate.
nitrogen-free extract The unanalyzed portion of a plant, consisting mostly of carbohydrates, that remains after the protein, ash, crude fiber, ether extracts, and moisture content have been determined. Abbr.: NFE.
NMP Nucleoside 5'-monophosphate.
no-till A method of planting crops that involves no seedbed preparation other than opening small areas in the soil for placing seed at the intended depth. There is generally no cultivation during crop production; instead, chemicals are used for vegetation control. Synonym: zero till.
nonenzymatic browning See browning.
nonnutritive fiber That portion of fiber in a feed that is not digestible and hence is of no nutritive value.
nonselective grazing Utilization of forage by grazing animals sot hat all forage species and/or all plants within a species are grazed. Usage: Nonselective grazing is generally attempted by using high stocking rates or high stocking densities during short time periods. It is rarely achieved in practice. See also mob grazing.
nopaline A rare amino acid derivative that is produced by a certain type of crown gall tissue. The nopaline synthase gene is located in the T-DNA of the Ti plasmid of Agrobacterium tumefaciens.
northern hybridization See northern blot.
NTP Nucleoside 5'-triphosphate.
nuclear magnetic resonance (NMR) spectroscopy A type of radio-frequency or microwave spectroscopy, based on the magnetic field generated by the spinning of the electrically charged nucleus of certain atoms. This nuclear magnetic field is caused to interact with the very large magnetic field of the instrument magnet. Each nuclear species requires a different instrumental setting to obtain resonance of the magnetic field frequency of the instrument with that of the nucleus. The setting also varies with the electron distribution around each atom, so it is possible for instance to distinguish among the three isotopes of hydrogen in ethyl alcohol. The direct relation of the NMR spectral bank height to the concentration of the chemical compound allows NMR to be used for quantitative analysis and for observing rates of reaction and equilibrium of chemicals in solution. Abbr.: NMR.
nucleic acids The class of long-chain acids (e.g., DNA, RNA) found especially in cell nuclei; composed of deoxyribose or ribose sugars, phosphate groups, and bases.
nucleosome The basic subunit structure of chromatin. Chromatin has a beads-on-a-string appearance, with regions of DNA tightly complexed with protein, separated by relatively naked stretches of the nucleic acid. The beadlike structures are the nucleosomes and consist of ~145 bp of DNA wound around a core particle that is an octomer of two molecules each of histones H2A, H2B, H3 and H4. In the linker regions between nucleosomes, the histone H1 is associated with the DNA.
nurse crop See companion crop.
nursery, stolon See stolon nursery.
nutrient, animal Food constituent or group of food constituents of the same general chemical composition required for support of animal life.
nutritive value index Daily digestible amount of forage per unit of metabolic body size relative to a standard forage. Abbr.: NVI.