T (1) Thymine, a pyrimidine base in DNA; pairs with adenine (in RNA, uracil substitutes for thymine in pairing with adenine). (2) Thymidine, the nucleoside having thymine as its base.
tailingSee terminal transferase.
TATA box A highly conserved, AT-rich, 7-base sequence found ~25 bases prior to the transcription start site of RNA polymerase II-transcribed eukaryotic genes. The TATA sequence facilitates, but is not essential for, transcription. Synonym: Goldberg-Hogness box; Hogness box; Pribnow box. See also CAT box.
temperature index of physiological timeSee heat sum.
tempered Brought to predetermined moisture characteristics or temperature (or both) before further processing.
template strand The nucleic acid strand that is copied during replication or transcription. Usage: Often shortened to template.
tenacity The tensile stress expressed as force per unit linear density of the unstrained specimen (e.g., of cotton).
terminal (1) Of or relating to an end or extremity. (2) Growing at the end of a branch or stem.
termination codon The trinucleotide sequences in mRNA molecules that terminate protein synthesis. There are three termination codons: UAA (ochre), UAG (amber) and UGA (opal). Synonym: stop codon. Compare start codon. See also nonsense mutation; suppressor mutation.
tester animals Animals of like kind and similar physiological condition used in grazing experiments to measure animal performance or pasture quality; usually assigned to a treatment for the duration of the grazing season, as opposed to grazer animals that may be assigned temporarily.
texture (1) The surface, appearance, and hand of a textile material. (2) In turf, leaf texture refers to leaf width, taper, and arrangement.
thatch control Preventing excessive thatch accumulation by cultural manipulation and/or reducing excess thatch by mechanical or biological means.
thymidineSee T. See also dTDP; dTMP; dTTP; TDP; TMP; TTP.
Ti plasmid A class of large, conjugative plasmids found in the soil bacterium Agrobacterium tumefaciens and responsible for the crown gall disease of broad-leaved (dicotyledonous) plants. The T-DNA region on the Ti plasmid is inserted into the genome of infected host cells or plants, which makes Ti plasmids and T-DNA especially useful for transformation of foreign genes into certain plants.
till-plant Seedbed preparation and planting completed in the same operation, or one immediately following the other, leaving a protective cover of crop residue on and mixed in the surface layer. In some areas, referred to as minimum tillage.
tillageFor other entries, see also bare fallow; chemical fallow; conventional tillage; minimum tillage; no-till; primary tillage; reduced tillage; secondary tillage; summer fallow; till-plant; zero till.
tissue culture Part II.
TMP Ribothymidine 5'-monophosphate.
tolerance range Range of environmental conditions in which an organism can survive; set mainly genetically, but modified by previous environmental history of the individual.
top cross The first generation of a cross between an open-pollinated variety and an inbred line, a foundation backcross, or a foundation single cross.
topdressing A prepared soil mix added to the turf surface and worked in by brooming, matting, raking, and/or irrigating to smooth a green surface, firm a turf by working soil in decomposition, cover stolons or sprigs during vegetative decomposition, and cover stolons or sprigs during vegetative planting. Also the act of applying topdressing materials to turf.
total digestible nutrients Sum total of the digestibility of the organic components of plant material and/or seed (e.g., crude protein + nitrogen-free extract + crude fiber + fat). Abbr.: TDN.
total nonstructural carbohydratesAbbr.: TNC. See carbohydrates, nonstructural.
toughness That property of a material by virtue of which it can absorb work.
toxicity (1) Being poisonous or toxic. (2) Injury, impairment, or death resulting from a poison or toxin; i.e., a toxic reaction. Synonym: toxicosis.
toxoid Toxin that has been treated to make it nontoxic, but that will still induce the formation of antibodies.
transcript The RNA product of a gene. The primary transcripts initially synthesized by RNA polymerases must often be processed or modified in order to form the mature, functional mRNA, rRNA, or tRNA species.
transcription Synthesis of an RNA from a DNA template.
transfection The transfer, to cells in culture, of a gene(s) from another cell. See also transduction.
transferred DNASee T-DNA.
transformation (1) Genetic transformation is the transfer and incorporation of DNA, especially recombinant DNA, into a cell. The cells, plants, or progeny resulting from this process are said to be transformed upon demonstration of the expression in the recipient organism of unique marker genes carried by the transferred DNA. (2) Biochemical transformation (or biotransformation) is the process of using cultured cells to convert substrates into other desirable organic compounds by virtue of an endogenous enzyme system that catalyzes the reactions.
transient expression The short-term detectable expression of the product of a gene that has been transferred into protoplasts, cells, or plants. Marker genes on the DNA construct (such as (-glucuronidase) that are readily assayed in plant tissues are often used to determine whether DNA has been transferred into the cells. Transient expression indicates only that the marker gene is transcribed and translated in the cells assayed, and does not imply that the gene or DNA construct has been heritably incorporated into the plant genome.
transitional climatic zone The suboptimal zone between the cool and warm climates, where both warm- and cool-season grasses can be grown.
transplacementSee gene replacement.
transposition The process whereby a transposable element or insertion sequence inserts into a new site on the same or another DNA molecule. The exact mechanism is not fully understood, and different transposable elements may transpose by different mechanisms. Transposition in bacteria does not require extensive DNA homology between the transposon and the target DNA and therefore is described as illegitimate recombination.
trench drain A trench backfilled to the surface with a coarse material, such as sand, gravel, or crushed rock, for the purpose of removing excess surface water rapidly. See also slit-trench drain.
trichome A filamentous outgrowth; specifically, an epidermal hair structure on a plant. Collectively, trichomes make up pubescence.
triplet A sequence of three nucleotides (i.e., a codon) that specifies an amino acid via recognition by specific charged tRNA species.
true digestibilitySee digestibility, true.
TTP Ribothymidine 5'-triphosphate.
turf A covering of mowed vegetation, usually a turfgrass, growing intimately with an upper soil stratum of intermingled roots and stems.
turfgrass color The composite visual color of a turfgrass as community perceived by the human eye.
turfgrass culture The composite cultural practices involved in growing turfgrasses for purposes such as lawns, greens, sports facilities, and roadsides.
turfgrass quality The composite, subjective visual assessment of the degree to which a turf conforms to an agreed standard of uniformity, density, texture, growth habit, smoothness, and color.