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... more 10.000 glossed keywords and links to more than 100 figures and schemes, about 100 tables etc. can be obtained in addition to this limited INTERNET version either on CD-ROM or in modified design as book by CRC Press, Taylor & Francis Group, Boca Raton, USA

T chromosome: a chromosome in which a terminal (T) region shows neocentric activity cyto >>> neocentric activity

T1 (generation): a term used in plant genetics; it refers to the progeny resulting from self-pollination of the primary transformant regenerated from tissue culture gene

T4 phage: a type of a bacteriophage used as a source of commonly used ligase, DNA polymerase, and polynucleotide kinase biot

tabular root: the main, downward-growing root of a plant, which grows deeply and produces lateral roots along its length bot

tail: single-strand DNA extension added by terminal deoxynucleotidyl transferase biot

tailings: partly threshed material that has passed through the coarse shakers or straw walkers and is eliminated at the rear of a threshing machine seed

take-all >>> saponin >>> take-all disease

take-all disease: a fungal disease (Gaeumannomyces graminis, syn Ophiobolus graminis) that attacks wheat plant roots; it causes dry rot and premature death of the plant; certain strains of Brassica plants and Pseudomonas bacteria act as natural antifungal agents against the fungus phyt >>> biological control

tandem duplication >>> tandem repeat

tandem repeat: a chromosomal mutation in which two identical chromosome segments lie adjacent to each other, with the same gene order; the DNA, which codes for the rRNA, contains many tandem repeats gene

http://wheat.pw.usda.gov/ITMI/Repeats/index.shtml

tandem selection: in the case of successive multiple selection the selection concerns other traits in the first few generations than in later generations meth

tannic acid >>> tannin

tannin: a generic term for complex, nonnitrogenous compounds containing phenols, glycosides, or hydroxy acids, which occur widely in plants (e.g., in the testa of cocoa and beans) chem phys

Tapesia yallundae: sexual stage of Pseudocercosporella herpotrichoides phyt >>> white leaf spot >>> eyespot disease

tapetal cell >>> tapetum

tapetal layer >>> tapetum

tapetum: a layer of cells, rich in food, which surrounds the spore mother cells bot

tapping: driving spouts into the trunks of maple or pine trees to let the sap out for food and industrial use fore

taproot: a large, descending, central root bot >>> tabular root

Taq (DNA) polymerase: a DNA-dependent RNA polymerase from phage T7, which recognizes a very specific promoter sequence; it is used in many expression vectors biot

Taraxum type: diplospory where the spore mother cell enters the meiotic prophase but because of synapsis there is no pairing and the univalents remain scattered over the whole spindle; the first meiosis results in a restitution nucleus; the second meiosis results in an unreduced dyad bot

targeting-induced local lesionsin genomes (TILLING): a reverse molecular genetic method that combines random chemical mutagenesis with PCR-based screening of gene regions of interest; it provides a range of allele types, including mis-sense and knockout mutations; by comparing the phenotypes of isogenic genotypes differing in single sequence motifs, TILLING provides direct proof of function of both induced and natural polymorphisms without the use of transgenic modifications biot meth  >>> EcoTILLING

target population: the target population is the entire group of individuals a breeder is interested in; the group about which he or she wishes to draw conclusions by several means stat

tassel: something resembling this, as at the top of a stalk of maize bot >>> Picture 71

tasseling (of maize): the time or process when maize emerges tassels agr >>> tassel >>> detasseling >>> Picture 10

TATA box: a canonic DNA sequence; part of a plant promoter; promotes the transcription of DNA gene

taxis: a change of direction of locomotion in a motile cell, made in response to certain types of external stimulus, such as temperature, light, nutrients etc. bot

taxon (taxa pl): a group of organisms of any taxonomic rank (i.e., family, genus, species, etc.) tax >>> Tables 12, 17

taxonomy: the scientific classification of organisms tax bio >>> Tables 1, 12, 14, 17

http://www.ars-grin.gov/cgi-bin/npgs/html/index.pl?language=en

t-distribution >>> STUDENT’s test

T-DNA >>> Ti plasmid

TE: Tris-EDTA buffer prep chem

teleutospore >>> teliospore

teliospore: a thick-walled resting spore produced by rust and smut fungi bot

telium (telia pl): pustule containing teliospores bot

telocentric (chromosome): the chromosomal centromere lies at the end cyto >>> Figures 11, 37

telochromomere: a chromomere that is terminally located cyto >>> chromomere

telochromosome >>> telosome

telomere: one of the two terminal chromomeres of a chromosome; telomeres certain nucleotide sequences, which promote the replication of the DNA double strand; a telomere also plays a role in the spatial orientation of chromosomes within the interphase nucleus cyto

telophase: the fourth and final phase of mitosis and the two divisions of meiosis, during which (1) the spindle disappears, (2) nucleoli reappear, (3)  the nuclear membrane start to develop around the two groups of daughter chromosomes and/or chromatids, and (4) the chromosomes return to their extended state, in which they are no longer visible; the nuclei then enter a resting stage as they were before division occurred cyto

telosome: shorthand of telochromosome; a chromosome with a terminally located centromere cyto >>> Figures 11, 37

telosomic >>> telosome

telotrisomic: in allopolyploids, such as hexaploid wheat, a cell or individual with one missing chromosome but having a telocentric and an isochromosome for the same arm of the missing one cyto >>> Figures 11, 37

temuline >>> Table 46

temperate grass(es): the most important sown temperate grasses are species of the genera Lolium, Festuca, Dactylis, Phleum, and Bromus agr bot

temperature gradient capillary electrophoresis (TGCE): a molecular method that can be used to distinguish heteroduplex from homoduplex DNA molecules and can thus be applied to the detection of various types of DNA polymorphisms; unlike most single nucleotide polymorphism (SNP) detection technologies, TGCE can be used even in the absence of prior knowledge of the sequences of the underlying polymorphisms; TGCE is both sensitive and reliable in detecting SNPs, small InDel (insertion/deletion) polymorphisms (IDPs) and simple sequence repeats, and using this technique it is possible to detect a single SNP in amplicons of over 800 bp and 1-bp IDPs in amplicons of approximately 500 bp; genotyping data obtained via TGCE are consistent with data obtained via gel-based detection technologies; for genetic mapping experiments, TGCE has a number of advantages over alternative heteroduplex-detection technologies, such as celery endonuclease (CELI) and denaturing high-performance liquid chromatography (dHPLC); multiplexing can increase TGCEs throughput to 12 markers on 94 recombinant inbreds per day; given its ability to efficiently and reliably detect a variety of subtle DNA polymorphisms that occur at high frequency in genes, TGCE shows great promise for discovering polymorphisms and conducting genetic mapping and genotyping experiments biot meth

template: the DNA single strand, complementary to a nascent RNA or DNA strand, that serves to specify the nucleotide sequence of the nascent strand gene

temporary resistance: vertical resistances are temporary in that they stop functioning on the appearance of a matching vertical >>> pathotype; they are within the capacity for micro-evolutionary change of the parasite phyt

T-end: a chromosome showing a terminal centromere cyto

tendril: part of a stem, leaf, or petiole that is modified as a delicate, commonly twisted, thread-like appendage; it is an aid to climbing (e.g., in pea) bot

tepal: one of the perianth members in those flowers where there is no distinction between calyx and corolla bot

teratology: the science of malformation bio

terminal association: in meiosis, the achiasmatic association of homologous chromosomes just by unspecific end-to-end attachments cyto

terminal centromere >>> telosome

terminalization: a progressive shift of chiasmata from their sites of origin to more terminal positions cyto

terminase: an enzyme of phage lamda, which generates the staggered cuts at the “cos” sites during packaging biot >>> lamda phage

termination: the incorporation of the final amino acid into a polypeptide chain and the release of the complete chain from the ribosomes during protein biosynthesis gene

termination codon >>> stop codon

terminator: a nucleotide sequence that acts as a signal for the termination of transcription biot

terminator seeds: a descriptive term used for seeds that have been genetically engineered to produce a crop whose first generation produces sterile seeds, thus preventing a second generation from being grown from seeds saved from the first; it might be a way to build patent protection directly into high-value, genetically engineered crop variety and thus recoup high research investment costs biot

terpene: a hydrocarbon that is composed of two or more isoprene units; they may be linear or cyclic molecules or combinations of both, and include important biological compounds, such as vitamins A, E, and K chem phys >>> growth inhibitor

terracing: converting hillsides into terraces that follow the contour is a method of soil conservation; it is an expensive and laborious process but, once completed, it is both effective and easily maintained; it is common in mountain regions of the world where soil for cropping is rare agr

terracotta pot(s): flower pots made of terracotta (baked clay) were common in the past; they are more expensive than plastic pots, but they provide a superior aeration to plant roots hort

tertiary gene pool: gene transfer from a species of the tertiary gene pool to the cultivated species, since the primary gene pool usually requires special crossing and embryo rescue techniques in order to get viable hybrids evol >>> primary gene pool >>> secondary gene pool

tertiary tiller >>> secondary tiller

tertiary trisome: a chromosome present in addition to the normal diploid complement but as a result of a reciprocal interchange between two standard chromosomes; frequently it occurs in the progeny of a translocation heterozygote cyto >>> balanced tertiary trisomic >>> Figure 14

test cross: a cross between a heterozygote of unknown genotype and an individual homozygous for the recessive genes in question; in general, each cross that contributes to the solution of an experimental question by using more or less defined crossing partners meth

test mating >>> test cross

test of significance >>> significance test

test tube: a hollow cylinder of thin glass with one end closed; used to hold chemicals or specimens in laboratory experimentation and analysis prep

testa: the seed coat; it derives from secondary outgrowths of the nucellus, and later the ovule; they are called collars or integuments; the inner and outer integuments become the testa of the mature ovule; it is commonly composed of cuticle, palisade layer, sandwich cells, and parenchym cells bot >>> caryopsis >>> seed coat

tester (plant): plants of like kind and similar physiological condition used in experiments to measure performance or quality characters meth >>> Figure 30

tetraallelic: in tetraploids, when multiple alleles loci all have different (e.g., four alleles,  A1A2A3A4) gene

tetracycline: an antibacterial antibiotic from Streptomyces spp. chem phys >>> achromycin

tetrad: four homologous chromatids in a bundle during the first meiotic prophase and metaphase cyto; in meiosis, the four haploid cells resulting from a single diploid cell during gametogenesis bot

tetrad analysis: the use of tetrads to study the behavior of chromosomes and genes in crossing-over during meiosis; particularly used in studies of fungi gene

tetraploid: having four sets of chromosomes in the nucleus gene cyto

tetraploidization: the mitotic or meiotic procedure in order produce tetraploids meth cyto

tetraploidy >>> tetraploid

tetrasome: a chromosome present four times cyto >>> tetrasomic

tetrasomic: having one or more chromosomes of a complement represented four times in each nucleus cyto >>> Figure 37

tetrasomy: the state of having one or more chromosomes as four copies cyto >>> Figure 37

tetrazolium test: a quick test to determine seed viability; tetrazolium is a class of chemicals that have the ability to accept hydrogen atoms from dehydrogenase enzymes during the respiration process in viable seeds; it is the basis of the test during which the tetrazolium chemical undergoes a color change, usually from colorless to red (formazan); the method was developed in Germany in the early 1940s by G. LAKON; the test is used throughout the world as a highly regarded method of estimating seed viability; it can be completed in only a few hours seed

TGCE >>> temperature gradient capillary electrophoresis

TGW >>> thousand-grain weight

THC >>> hemp

theca: usually referring to the pollen sac in flowering plants or the capsule in bryophytes bot >>> Figure 35

theobromine: a mutagenically active purine analogue chem phys

thermoperiodism: in some plants (e.g., Chrysanthemum, tomato), the floral induction is accomplished by repeated exposure to low night temperatures, separated by periods of higher temperature bot

thermophil(ic) (plants): plants preferring moderate temperature and/or those that cannot cope with low temperatures or frosts phys

thermotaxis >>> taxis

thiamine: contributes to the formation of the important coenzyme thiamine pyrophosphate, which is involved in the oxidative decarboxylation of alpha-keto acids and transketolase reactions phys

thin: in a cultivated crop, to remove some plants in order to increase the area available to others agr; in forestry, removal of trees in an overstocked stand to give the remaining trees adequate room for growth fore

thinning >>> thin

thiol: any of a class of odiferous, sulfur-containing compounds chem phys

thorn: a hard, sharp outgrowth on a plant (e.g., a sharp-pointed aborted branch) bot

thousand-grain weight (TGW): equals 1,000-grain weight given in grams; it refers to a measure for seed weight, and thus indirectly for seed size; from a seed lot 1,000 seeds are randomly taken and get balanced in grams meth

three-parent cross >>> three-way cross

three-point cross: a series of crosses designed to determine the order of three, nonallelic, linked genes upon a single chromosome on the basis of their crossing-over behavior gene >>> three-point test cross

three-point test cross: cross involving one parent with three heterozygous gene pairs and another (tester) with three homozygous recessive gene pairs gene meth >>> three-point cross

three-way cross: a first generation hybrid between a single-cross and an inbred line or pure line variety meth >>> Figure 31

three-way hybrid: a hybrid between an inbred line and single cross hybrid seed meth >>> Figure 31

threonine (Thr): an aliphatic, polar alpha-amino acid chem phys

threshing: breaking the seeds free from the seedpods and other fibrous material or the separation of seed from chaff agr

threshing machine: a device that breaks the seeds free from the seedpods and other fibrous material or the separation of seed from chaff agr

threshold value: a critical value on an underlying scale of liability above which individuals manifest a trait or disease stat

thrips: any of several minute insects of the order Thysanoptera that have long, narrow wings fringed with hairs and that infest and feed on a wide variety of weeds and crop plants zoo phyt

throat: the center of a daylily where the pistil and stamens join, often contrasting in color to the base blossom color; breeding for green throats that remain sunfast or non-fading throughout the day, as green is wished to improve overall aesthetic appeal of a cultivar; older varieties of daylilies, many now regarded as obsolete, have gold, yellow, or melon-colored throats hort

throw-back >>> atavism

thylakoid: one of the membranaceous discs or sacs that form the principal subunit of a granum in chloroplasts bot

thymidine: a nucleoside with thymine as its base; it acts as an essential growth factor for microorganisms chem phys

thymine (T): the pyrimidine base that occurs in DNA chem gene

TI >>> transcript imaging

tiered: a breeding population may be tiered in different compartments, which can not be considered as sublines, rather elite and mainline meth

tigella: a short stem bot

tillage: the preparation of soil for seeding; it includes manuring, ploughing, harrowing, and rolling land, or whatever is done to bring it to a proper state agr

tiller(s): shoots, some of which will eventually bear spikes, which arise from the base of the stem in the grasses bot >>> Figure 28

tillering >>> tiller

tillering node: a node on the base of the stem in grasses from which shoots arise bot

tilling: a technique to screen a population that has either been deliberately mutagenised or possesses natural biodiversity (ecotilling) to identify those plants with a change in a specific gene of interest; the technique uses high-throughput methods useful to plant breeders meth

TILLING >>> targeting induced local lesions in genomes

tilth: the condition of the soil after preparation for seeding agr

timberline US >>> tree limit

time components: basic operations take time, e.g., recombination, time before the test, testing time and time after the test; breaking of cycling time into components can be used in optimization of breeding strategies, e.g., choice of the most efficient testing or selection method meth

time isolation: an isolation practice to prevent crossing; it is used  when distance isolation is a problem, caging is too costly or troublesome, or when only growing a couple varieties in a season; it works with any two varieties or species that shed pollen over a limited time and have sufficiently different rates of maturation; to use time isolation, planting dates of two similar varieties are staggered so that by the time the later of the two varieties is flowering, the earlier variety has already finished flowering and is no longer producing or receptive to pollen; the earlier, faster-maturing crop is planted a couple or three weeks before the later, slower-maturing one meth

Ti plasmid: Ti = tumor inducing; established tumors in plants contain only a part of the total plasmid (about 10 %); this part is called T-DNA; this part of the pathogen is integrated into the chromosomes of the host cell gene

tissue: a group of cells with similar origin and structurally organized into a functional unit; the organs of multicellular organisms are made up of combinations of tissues, of one or more types of cells bot

tissue: a group of cells with similar origin and structurally organized into a functional unit; the organs of multicellular organisms are made up of combinations of tissues, of one or more types of cells bot

tissue culture: the maintenance or growth of tissue in vitro in a way that may allow further differentiation, preservation, or regeneration biot

titer: the amount of a standard reagent necessary to produce a certain result in a titration chem

tocopherol (vitamin E): a fat-soluble vitamin in eight forms that is an important antioxidant; it is often used in skin creams;  it is claimed to play a role in encouraging skin healing and reducing scarring after injuries, such as burns; vitamin E exists in eight different forms or isomers, four tocopherols and four tocotrienols; all isomers have a chromanol ring, with a hydroxyl group, which can donate a hydrogen atom to reduce free radicals and a hydrophobic side chain which allows for penetration into biological membranes; there is an alpha, beta, gamma and delta form of both the tocopherols and tocotrienols, determined by the number of methyl groups on the chromanol ring; each form has its own biological activity; wildtype sunflower (Helianthus annuus) seeds are a rich source of α-tocopherol phys

tolerance: the ability of a plant to endure attack by a pathogen without severe loss of yield phyt

tolerant: the ability of a host plant to develop and reproduce fairly efficiently while sustaining disease phyt

tollocan: a Mexican >>> short-day >>> potato, which has an exceptionally high level of >>> horizontal resistance to >>> blightagr phyt

tonoplast: a membrane that borders the vacuole of a cell bot

topcross: a cross between a selection, line, clone, etc. and a common pollen parent, which may be a variety, inbred line, single cross, etc.; the common pollen parent is called the top cross or tester parent; in maize, a top cross is commonly called an inbred-variety cross; usually, it is used in order to test the “general combining ability” meth >>> Figure 19

topcross hybrid: the first generation of a cross between an inbred line and an open pollinated variety seed meth

topcross progeny: progeny from outcrossed seed of selections, clones, or lines to a common pollen parent meth >>> Figure 19 >>> topcross

topcross test >>> topcross

top-dressing: fertilization when crop plants are already developed, usually before flowering (i.e., an additional fertilization to the basic dressing before sowing or close behind); in horticulture, using material, such as compost or manure, that is applied to the surface around the plant to aid in drainage, decrease erosion, prevent moisture loss, and keep weeds down agr hort

topsoil: the fertile, upper part of the soil agr

top-watering: a method whereby water is simply poured into the soil from the top; when employing a top-watering method with some ornamental plants, it is crucial to avoid overwatering and to minimize the amount of water which might splash on the leaves; at the very least, improper watering can cause >>> watering spots; in the worst cases, improper watering can encourage the growth of deadly fungi, such as those which cause crown rot, root rot, and Pythiumhort meth

torpedo stage: the stage of somatic and zygotic embryogenesis in which the embryo or mass of cells are torpedo-shaped biot

torus: the receptacle of a flower bot

total mean square >>> variance

totipotency: the potential ability of a cell to express all its genetic information under appropriate conditions and to proceed through all the stages of development to produce a fully differentiated adult gene

totipotent(ial) >>> totipotency

tough rachis: a nonbrittle rachis of a spike; for example, in wheat, the nonbrittleness is determined by two recessive genes on the short arms of chromosomes 3A and 3B; the consequence of threshing is spikelets, rather than grains gene bot agr

toxicity: the quality, relative degree, or specific degree of being toxic or poisonous meth prep

toxigenic >>> toxicity

trabant >>> satellite

trace element: an element required only in minute amounts by an organism for its normal growth phys >>> micronutrient

trachea: wood vessel bot

trade: a pair of collections of blocks of a >>> block design, or rows of an array, such that some property of the design or array is preserved if the first set of blocks is removed and replaced by the second stat

training: the operation of forming (young) tree plants to a wall or espalier, or causing them to grow in a desired shape hort meth

trait: a recognizable quality or attribute resulting from the interaction of a gene or group of genes with the environment meth gene >>> character

tramlines: unseeded, equispaced tracks established in a field at seeding time to provide a pass in the field for tractors to use to aid in the application of chemicals and fertilizer agr meth

transaminase (aminotransferase): an enzyme that catalyzes a transamination reaction chem phys

transamination: the transfer of an amino group from an amino acid to a keto acid in a reaction catalyzed by a transaminase chem

transcript: the RNA product of a gene gene

transcript imaging (TI): a technique based on AFLP analysis applied to cDNA; it provides a quantified view of all the transcripts in a sample on an electronic image where approximately 20,000 AFLP bands, each representing a transcript, can be detected and quantitated; differences between strains, samples, or treatment can be detected and the differential bands can be sequenced; the sequence of the band leads to the identification of the transcript meth biot

transcription: the polymerization of ribonucleotides into a strand of RNA in a sequence complementary to that of a single strand of DNA; by this means the genetic information contained in the latter is faithfully matched in the former; the process is mediated by a DNA-dependent RNA polymerase gene

transcriptome: DNA sequences of the expressed genome biot

transduce >>> transduction

transduction: the transfer of bacterial genetic material from one bacterium to another via phage gene

transfectant: a genetic transformation of a cell by free (naked) DNA gene

transfection: introduction of pure (naked) phage DNA into a cell biot

transferase: an enzyme that catalyzes the transfer of a functional group from one substance to another chem phys

transfer RNA (tRNA): a generic term for a group of small RNA molecules, each composed of 70-80 nucleotides arranged in a clover-leaf pattern stabilized by hydrogen bonding; they are responsible for binding amino acids and transferring these to the ribosomes during the synthesis of a polypeptide gene

transformant: the cell or individual that was transformed during a transformation procedure biot

transformation: in general, the heritable modification of the properties of a plant; in biotechnology, the transfer of genetic information to a recipient strain of bacteria by DNA extracted from a donor strain, and recombination of that DNA with the DNA of the recipient biot

transformation efficiency: the number of bacterial and/or plant cells that uptake and express plasmid DNA and/or a foreign gene, respectively, divided by the mass of plasmid used biot

transgene: a gene introduced into a host genome by transfection or other similar means biot

transgenic >>> transgenic plants

transgenic genotype >>> transgenic plants

transgenic plants: a plant that contains an alien or modified DNA (gene) introduced by biotechnological means, and which is more or less stable inherited biot

transgression: segregants in a segregating population that fall outside the variation limit of parental lines gene

transgressiv(e) >>> transgenic plants

transgressive segregation: the segregation of individuals in the F2 or a later generation of a cross that shows a more extreme development of a character than either parent gene

transient expression: the temporary expression of a gene or genes shortly after the transformation of a host cell (i.e., cells in which the transgene has not been physically incorporated into the genome [stable transformation], but is carried as an episome that can be lost) biot

transition: a type of mutation that involves the replacement in DNA or RNA of one purine with another or of one pyrimidine with another gene

translation: the polymerization of amino acids into a polypeptide chain whose structure is determined genetically gene

translocation: a change in the arrangement of genetic material, altering the location of a chromosome segment; the most common forms of translocation are reciprocal, involving the exchange of chromosome segments between two nonhomologous chromosomes cyto

translocation tester set: a series of more or less defined homozygously reciprocal translocations; they may be utilized in test crosses to identify accessory or unknown chromosomes by homologous pairing in MI of meiosis (e.g., this sort of tester set was produced in diploid rye and barley) meth cyto

transmission: the spread of a disease agent among individual hosts phyt

transpiration: the loss of water vapor from a plant to the outside atmosphere; it takes place mainly through the stomata of leaves and the lenticels of stems phys

transplant: to relocate or remove to a new growing place meth; in biotechnology, the cultured tissue or explant, relocated or transferred to a new site in vitro biot

transplanting board: a simple device having regularly spaced slots for the individual plants in order to ensure proper spacing and lining out in the new bed fore hort

transplastomic plants: plants with genetic modifications in the DNA of their chloroplasts; plant cells contain chloroplasts, cell organelles responsible for photosynthesis; these chloroplasts contain their own DNA which is separated from the cell's nuclear DNA; in transplastomic plants, the DNA in the chloroplasts has been genetically engineered; since only the nuclear DNA is inherited, the genetic modification in the chloroplasts will not be passed on to the next generation; therefore, transplastomic plants may be a solution for ensuring biocontainmentbiot meth

transposable element: a chromosomal locus that may be transposed from one spot to another within and among the chromosomes of the genome; it happens through breakage on either side of these loci and their subsequent insertion into a new position either on the same or a different chromosome gene

transposition: in molecular biology, the process of moving a transposon or other inserts from one position to another within a genome cyto >>> translocation

transposon: chromosomal loci capable of being transposed from one spot to another within and among the chromosomes of a complement gene >>> transposable element >>> transposition

transposon tagging: the blocking activity of functional genes by insertion of foreign DNA biot

transverison: a mutation in which a purine is replaced with a pyrimidine or vice versa biot

transversal design: a >>> group-divisible design in which every block is a transversal to the groups stat

trap nursery: sets of plant genotypes are assembled that carry specific resistance to the pathogen in question; it is grown in different geographic locations; it provides information on pathogen populations and may provide resistant genotypes for local breeding phyt

trap plants >>> trap nursery

tree: a woody plant, which may grow >10 m tall; trees developed during the Devon about 385 million years ago; they were like palm or tree ferns in habit bot

tree injector: certain types of equipment specially designed to inject chemicals, usually phytocides, into the trunk of a tree fore phyt

tree limit: the altitude above sea level at which timber ceases to grow eco

tree line >>> tree limit

tree ring >>> annual ring

tree shelter: a plastic tube or other tissue that can be wrapped around the stem of hardwood seedlings to increase survival and growth fore meth

trench planting: setting out young trees in a shallow trench or a continuous slit meth fore hort

triazine: any of a group of three compounds containing three nitrogen and three carbon atoms arranged in a six-membered ring and having the formula C3H3N3; some of these compounds are used as herbicides chem phys phyt

tribe: a rank between family and genus, comprising genera whose shared features serve to distinguish them from other genera within the family tax >>> Table 12

trichome: a hairy outgrowth on a plant’s surface, as a prickle bot

trier: a hand manipulated probe for sampling seeds seed

trigeneric hybrid: a spontaneous or experimental hybrid consisting of three genomes of different genera bot cyto gene

trihybrid: progeny resulting from a cross of parents differing in three genes gene

triisosomic: in allopolyploids, such as hexaploid wheat, when a cell or individual lacks one chromosome pair while three homologous isosomes for the same arm are present cyto >>> Figure 37

trioecious: species having male, female, and hermaphroditic flowers on different individuals bot

triple superphosphate: a fertilizer obtained by treating phosphate rock with phosphoric acid and containing about 46% P2O5, mainly in water-soluble form, unlike single superphosphate, it contains very little sulphur chem agr

triplet: a unit of three successive bases in DNA and RNA, which code for a specific amino acid gene

triplex (type) >>> autotetraploid >>> nulliplex type

triploid: applied to a cell or individual with three sets of chromosomes in its nucleus cyto

triploidy: a state in which three chromosome sets are present cyto

tripping mechanism: a pollen dispersal mechanism of some legumes, in which the staminal column is sprung free of the keel and exposed; it can also be initiated by hand in order to imitate insect activity and to stimulate self-pollination, for example, in broad bean (Vicia faba) bot

triradial (chromosome configuration): a chromosomal pairing configuration of three in which the homologous chromosomes are arranged like star cyto >>> Figure 15

trisome >>> trisomic

trisomic: a genome that is diploid but that contains an extra chromosome, homologous with one of the existing pairs, so that one kind of chromosome is present in triplicate cyto >>> Figures 14, 15, 37

trisomic analysis: a method for mapping gene loci on individual chromosomes by comparing disomic and trisomic segregation patterns of a series of individuals gene >>> Figure 37 >>> Table 4

trisomic series: a complete set of trisomics of a given plant species, in which all different chromosomes of the complement are available as trisomics in appropriate individuals (e.g., in barley, rye, tomato, maize, etc.) cyto >>> Figures 14, 15, 37

tristeza: Spanish: sadness; a virus disease of citrus; the diagnostic symptom is a flattening of the branches and, when the bark is peeled off, there are pits in the wood, with corresponding projections in the bark; diseased trees usually die, following severe dieback; it is a graft incompatibility disease, and it is serious mainly on trees grafted on to sour orange rootstocks; resistant scion-stock combinations have rootstocks of sweet orange, rough lemon, and “Cleopatra mandarin”, the disease is also known as “stem pitting” hort phyt

tristyly: three lengths of the style relative to the anthers (short, medium, long) bot

trivalent: an association of three homologous chromosomes in meiosis cyto >>> Figures 14, 15

tRNA >>> transfer RNA

trophic >>> tropism

tropical grass(es): the most important cultivated tropical grasses are species of the genera Digitaria, Eragrostis,Chloris, Cenchrus, Melinis, Panicum, Pennisetum, Cynodon, or Paspalum agr bot >>> temperate grasses

tropism: a directional response by a plant to a stimulus bot

truck crop US: vegetables and fruits grown in large quantities for the market hort

true breeding: a situation in which a group of identical individuals always produce offspring of the same phenotype when intercrossed meth gene

truncated: appearing as though abruptly cut across toward the apex bot

truncation selection: a breeding method in which individuals in whom quantitative expression of a phenotype is above or below a certain value (i.e., truncation point) are selected as parents for the next generation meth

trunk >>> stem

trunkless >>> boleless

truthfully labeled seed: seed with label of the producer with information on the seed quality seed

tryphine >>> entomophilous

trypsin: an enzyme of the pancreatic juice, capable of converting proteins into peptone chem phys

tryptophan(e) (Trp): a heterocyclic, nonpolar, alpha-amino acid chem phys

tube nucleus >>> vegetative nucleus

tube planting: setting out young plants in narrow, open-ended cylinders of various materials meth hort fore

tuber: a swollen stem or root that functions as an underground storage organ bot

tuber blight >>> late blight

tuberous >>> bulbous

tuberous roots: they look like tubers, but are actually swollen, nutrient-storing root tissue (e.g., in dahlias); during the growing season, they put out fibrous roots to take up moisture and nutrients; new growth buds, or eyes, form at the base of the stem; this area is called the crown bot

tubiform floret: a small flower in a flower head or other cluster showing a tubelike shape bot

tubular floret >>> tubiform floret

tuft: many stems in a close cluster at ground level; not spreading (e.g., as in some grasses) bot

tunic: a loose, outer covering or skin surrounding some corms and bulbs (e.g., in onion and tulip) bot

turf: the surface of grassy land, consisting of soil or mold filled with the roots of grass and other plants agr

turgescent >>> turgid

turgid: the crisp, fresh condition found when the cells of the plant are amply supplied with water to the extent that they are fully extended, as opposed to wilted bot

turgor: the rigidity of a plant and its cells and organs resulting from hydrostatic pressure exerted on the cell walls phys

turgor pressure >>> turgor

twig: a shoot or small branch of a tree or shrub bot

twin: a pair of individuals produced at one birth gene

twin seedling: a common feature of plants; frequently, one of the seedlings is diploid, while the other is haploid via apomictic development (e.g., in asparagus, rye, etc.); in the past, twin seedlings were used for haploid selection bot meth >>> haploid

two-rowed >>> barley

tyrosinase - Tyrosinase f: an enzyme that converts tyrosine to dopa and oxidizes this to dopa quinone chem phys

tyrosine (Tyr) - Tyrosin n: an aromatic, polar alpha-amino acid chem phys

© by R. Schlegel 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014

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