Glossary of Crop Science Terms - Browse
C (1) Cytosine, a pyrimidine base in DNA and RNA; pairs with guanine. (2) Cytidine, the nucleoside having cytosine as its base.
C-banding Centromere banding. (1) Technique for chromosome identification, using modified Giemsa staining to reveal the distribution of constitutive heterochromatin, expressed at principal stages of meiotic and mitotic division. (2) The banding pattern thus revealed. See also G-banding; N-banding; Q-banding; R-banding.
calcined clay Clay minerals, such as montmorillonite and attapulgite, that have been fired at high temperatures to obtain absorbent, stable, granular particles; used as amendments in soil modification.
callus Undifferentiated tissue cultured in vitro on a synthetic medium.
callus culture See tissue culture.
calorie The amount of heat required to raise the temperature of 1 g of H2O by 1 °C. Synonym: gram calorie. Symbol: cal. 1 kilocalorie (kcal) = 1000 calories; 1 megacalorie (Mcal) = 1 000 000 calories. The SI equivalent is the joule (1 calorie ~ 4.19 J).
canopy The vertical projection downward of the aerial portion of plants, usually expressed as percent of ground so occupied.
cap site The probable site of transcription initiation for eukaryotic genes. The primary transcripts of most eukaryotic mRNAs have an A (adenine) in the first position and the cap is added 5' to it.
carbohydrates, structural Carbohydrates found in the cell walls (e.g., hemicellulose, cellulose).
carding The process of untangling and partially straightening fibers by passing them between two closely spaced surfaces, at least one of which is covered with sharp points, that move at different speeds, thus converting a tangled mass of fibers to a filmy web.
carrying capacity The maximum stocking rate that will achieve a target level of animal performance, in a specified grazing method, that can be applied over a defined period of time without deterioration of the ecosystem. Usage: Carrying capacity is not static from season to season or year to year and may be defined over fractional parts of years. Average carrying capacity refers to long-term carrying capacity averaged over years; annual carrying capacity refers to a specific year. Synonym: grazing capacity.
castings, earthworm Soil and plant remains excreted and deposited by earthworms in or on the turf surface or in their burrows. Castings form relatively stable soil granules that can, on closely mowed turf, produce an uneven surface. Synonym: earthworm casts.
CCC See covalently closed circle.
cDNA cloning The use of cDNA to clone the coding sequence of a gene or sets of genes by starting with mRNA. The cDNA from mature processed transcripts does not contain introns, the presence of which could act to prevent expression of plant or animal cDNAs when attached to a suitable promoter and cloned into a host organism such as bacteria or yeast.
cell culture The growing of cells in vitro, including the culture of single cells or suspensions of small aggregates of cells. In cell cultures, the cells are no longer organized into tissues. Compare tissue culture. See also callus; suspension culture.
cell generation time The interval between consecutive divisions of a cell. This interval can best be determined, at present, with the aid of cinephotomicrography. Usage: Not synonymous with population doubling time.
cell line (1) Descent, through cell division, from a single original cell. (2) More specifically: A cell line arises from a primary culture at the time of the first successful subculture. The term implies that cultures from a cell line consist of numerous lineages of cells originally present in the primary culture.
cell-free transcription See in vitro transcription.
cell-wall constituents Compounds that make up or constitute the cell wall, including cellulose, hemicellulose, lignin, and minerals (ash); i.e., neutral-detergent fiber.
cellulose A carbohydrate formed from glucose, and a major constituent of plant cell walls; a colorless solid, insoluble in water. Compare hemicellulose.
cellulose nitrate See nitrocellulose.
center of origin The geographic region in which a taxon (species, genus, family, etc.) or a crop originates.
centrifugal spreader An applicator from which dry particulate material is broadcast as it drops onto a spinning disk or blade beneath the hopper.
certified seed Certified seed is the progeny of breeder, select, foundation, or registered seed so handled as to maintain satisfactory genetic purity and identity, and which has been acceptable to the certifying agency. Certified tree seed is defined as seed from trees of proven genetic superiority, as defined by the certifying agency, produced so as to assure genetic identity. Seed from interspecific hybrids or forest trees may be included.
cesium sulfate Cs2SO4. A cesium salt that forms solutions of greater density than cesium chloride (CsCl) and is used for isopycnic or density-gradient centrifugation of double-stranded RNA molecules.
chain terminator The UAA, UAG, and UGA codons (stop or termination codons) that do not code for an amino acid but rather signal ribosomes to terminate protein synthesis. Two stop codons may often be found together at the end of a coding sequence of RNA.
chalky Color descriptor (related to hardness) characterizing kernel endosperm of cereal grains, especially rice. A rice kernel with a high level of chalk is generally undesirable. The chalky appearance arises from the structure of the endosperm, which has many small voids between the starch granules and the protein matrix. These voids cause light to be refracted and hence the endosperm appears white to reflected light and opaque to transmitted light. Synonyms: floury; soft endosperm. Compare: corneous; vitreous; flinty.
chemical tillage See chemical fallow.
chilling injury Damage to plants at low temperatures in the absence of freezing. Chilling injury is common in plants of tropical or subtropical origin at temperatures <10 °C (<50 °F) or, for some fruits, <15 °C (<59 °F). The cause usually is a change in viscosity of lipids in membranes.
chimera (1) A recombinant DNA molecule that contains sequences from more than one organism. (2) At the plant level, a mixture of tissues of genetically different constitutions that have resulted from mutation, grafting, or gene transfer.
chloroplast A plastid containing chlorophyll and other photosynthetic pigments within which photosynthesis takes place.
chloroplast genome See organelle genome.
chromic oxide Cr2O3. A completely indigestible chemical used as an indicator to estimate forage intake.
chromosome Part II.
chromosome walking The sequential isolation of clones carrying overlapping sequences of DNA. The technique allows large regions of a chromosome to be covered, and can be used to identify which clone in a gene bank contains a desired gene or sequence that cannot be easily selected directly. Initially, a known gene is used to identify a clone containing it in colony hybridizations and then to obtain adjacent sequences for a second round of hybridization to identify clones with even more distal sequences. By repeating this process, the distance between a known cloned gene and a second uncloned gene of interest can be spanned, provided that both genes are on the same chromosome and the gene bank contains clones with all the intervening sequences.
clean seed Usage: For tall fescue seed, endophyte-free seed is the preferred term.
cleared lysate The intracellular contents obtained by cell disruption, detergent treatment, and centrifugation to remove cell debris and large particles. The resulting solution contains primarily nucleic acids and protein. Preparation of a cleared lysate is usually the first step in plasmid DNA purification.
cline (1) A character gradient within a species, related to geographic distribution. (2) A more or less uniform series of variants from one extreme to the other.
clippings Leaves, and in some cases stems, cut off by mowing.
clonal propagation Asexual reproduction of plants that are considered to be physiologically and/or genetically uniform and to have originated from a single individual or explant.
clone All the asexually produced progeny of a single original individual that have been propagated vegetatively, usually by cuttings or natural propagation of bulbs, tubers, or rhizomes.
cloning efficiency See plating efficiency.
closed continuous culture A continuous culture in which inflow of fresh medium is balanced by outflow of corresponding volumes of spent medium. Cells are separated mechanically from outflowing medium and added back to the culture.
CoA Coenzyme A.
coated soluble fertilizer See slow-release fertilizer.
coding sequence That portion of a gene that directly specifies the amino acid sequence of its protein product. Noncoding sequences of genes include control regions, such as promoters, operators, enhancers, terminators, and introns.
codon A sequence of three nucleotide bases that specifies an amino acid or represents a signal to start or stop translation. Usage: Write codon names without intervening punctuation or spaces (e.g., UAU, UAG). Compare anticodon. See also start codon; termination codon.
cold test A seed vigor test in which seeds are planted for a period of time in cool, moist unsterilized soil before transfer to a higher temperature, designed to approximate unfavorable planting conditions.
cold-water insoluble nitrogen A form of fertilizer nitrogen not soluble in cold water (25 °C; 77 °F). Abbr.: WIN. See also nitrogen activity index.
cold-water soluble nitrogen A form of fertilizer nitrogen soluble in cold water (25 °C; 77 °F). Abbr.: WSN. See also nitrogen activity index.
colony-forming efficiency See plating efficiency.
colorant A dye, pigment, or paintlike material applied to turf to create a favorable green color when the grass is discolored or damaged.
combing Using a comb to lift stolons and procumbent shoots so that they can be cut by a mower; the comb typically has metal teeth or flexible tines and is fastened immediately in front of a reel mower.
companion crop One crop sown with another, used particularly of the small grains with which forage crops are sown. Synonym nurse crop. Usage: Companion crop is the preferred term.
complementary RNA See cRNA.
composite-cross population A population generated by hybridizing more than two varieties and/or lines of normally self-fertilizing plants and propagating successive generations of the segregating population in bulk in specific environments so that natural selection is the principal force acting to produce genetic change. Artificial selection may also be imposed. The resulting population is expected to have a continuously changing genetic makeup. Breeder seed is not maintained as originally released.
conditioned storage Storage of seed under controlled conditions of temperature and relative humidity.
conjugation The transfer of genetic material between mating types of bacteria involving donors (F+ type) and recipients (F-).
consumer acceptance The likelihood that the consumer will use the genotype, phenotype, or product by choice.
continuous culture A suspension culture continuously supplied with nutrients by the inflow of fresh medium. The culture volume is normally constant. Usage: Describes the methodology, not the cells. See also closed continuous culture; open continuous culture.
continuous stocking A method of grazing livestock on a given unit of land where animals have unrestricted and uninterrupted access throughout the time period when grazing is allowed. Usage: Specify the length of the grazing period. Synonym (not recommended): continuous grazing. See also rotational stocking; set stocking.
controlled-availability fertilizer See slow-release fertilizer.
conventional planting Planting that takes place days to months after a fallow period; usually involves primary and numerous secondary tillage operations. Synonym: delayed planting.
convergent improvement A breeding method involving the reciprocal addition to each of two inbred lines of the dominant favorable genes lacking in one line and present in the other. Backcrossing and selection are performed in parallel, each of the original lines serving as the recurrent parent in one series.
cool-season turfgrass Turfgrass species best adapted to growth during cool, moist periods of the year, commonly having temperature optimums of 15 to 25 °C (60-75 °F).
copy number (1) The number of plasmid molecules per cell. (2) The number of times a specific gene is present per haploid genome. See also low-copy; multicopy; single-copy.
cored hay samples Samples taken from stored hay, using a hollow cylinder to remove a core.
corneous Characterizing hard, vitreous, or horny endosperm in cereal grains. See also chalky.
coumestrol Estrogenic compound occurring naturally in forage crops, especially in ladino clover, strawberry clover, and alfalfa.
covalently closed circle A double-stranded DNA molecule with no free ends that has a naturally supercoiled configuration. The two strands are interlinked and remain together even after denaturation if there are no single-strand nicks. Abbr.: CCC.
cover, winter protection See winter protection cover.
creeping growth habit Plant development by extravaginal stem growth at or near the soil surface, with lateral spreading by rhizomes and/or stolons. Synonym: spreading growth habit.
critical level As applied to plant response functions, that level of a factor which is just limiting to plant performance; sometimes specifically defined as 95% of the performance when the factor is nonlimiting. Usage: Widely used in plant and soil analysis for evidence of nutrient deficiency or toxicity. With leaf-area index, used as the index sufficient for near-maximum light interception or growth rate.
crop residue Portion of plants remaining after seed harvest; refers mainly to grain crop residue, such as corn stover, or of small-grain straw and stubble.
cross-pollination Pollen of one flower on one plant applied (artificially or naturally) to the stigma of a flower on another plant.
crossing over Exchange of genes between two paired chromosomes.
crossover Part II.
crown gall A tumor formed predominantly on the stems of broad-leaved plants when infected with Agrobacterium tumefaciens containing a Ti-plasmid. Part of the Ti-plasmid (T-DNA) is transferred into the genome of the affected plant cells due to action of the Ti-plasmid vir genes. Expression of T-DNA genes for auxin and cytokinin synthesis cause gall formation even in the absence of the bacterium. Whole plants can sometimes be regenerated from crown gall tissue and some of these still contain T-DNA.
CTP Cytidine 5'-triphosphate.
cubing Process of forming hay into high-density cubes to facilitate transportation, storage, and feeding.
cultivar (1) A variety, strain, or race that has originated and persisted under cultivation or was specifically developed for the purpose of cultivation. (2) For cultivated plants, the equivalent of botanical variety, in accordance with the International Code of Nomenclature of Cultivated Plants-1980. Usage: Cultivar names are not italicized, and are indicated by single quotes at first use, or the word cultivar (but not both). The abbreviation cv. is properly used only with a binomial name: Genus species cv. cultivarname. Omit the abbreviation if single quotes are used: Genus species 'cultivarname'.
culture Part II.
culture medium Any nutrient system for the artificial cultivation of bacteria or other cells; usually a complex mixture of organic and inorganic materials. Plural: media.
cup cutter A hollow cylinder with a sharpened lower edge used to cut the hole or cup in a green, or to replace small spots of damaged sod.
cut (1) To make a double-stranded break in DNA, usually with a Type II restriction endonuclease. Usage: 'Cut' is a popular term; the more specific term is cleave. (2) Such a break.
cuticle A waxy layer secreted by epidermal cells on the outer surface of plants.
cutout In cotton: the occurrence of physiologically indeterminate growth.
cyanogenesis The release of hydrocyanic acid (HCN), in the process of chemical change. adj. Cyanogenetic, cyanogenic. Usage: Cyanogenetic is the preferred adjectival form.
cytidine See C. See also CMP; CTP; dCMP; dCTP.
cytokinins A class of plant growth regulators (chemically and functionally related to the natural hormone zeatin) that cause cell division, cell differentiation, shoot differentiation, etc. Cytokinins commonly used in tissue culture include kinetin, benzylaminopurine (BAP), and 2-isopentenyladenine (2-iP).
cytoplasmic inheritance Traits controlled by organelle genes in the chloroplast or mitochondrial genomes; such traits usually express the phenotype of the maternal parent, although examples of biparental or paternal transmission of organelle genomes do occur.
cytosine See C.