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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

habit(us): the general appearance of a plant bot

habitat: the living place of an organism or community characterized by its physical or biotic properties eco

habituation: the diminishing requirement of some tissue cultures for growth-regulatory substances, possibly due to endogenous production biot

hair: a slender outgrowth of the epidermis, common on certain leaf or stalk structures bot >>> Picture 012

hairy root disease: a disease in some dicots; rootlike tissue is proliferated along segments of the stem; it is caused by Agrobacterium rhizogenes, if it carries a Ri plasmid phyt biot


half-diallel cross: the crossing of a series of genotypes in all combination except reciprocal combinations meth

half-grain method: a method in cereals separating the embryo from the endosperm by transversal dissection; it is applied when the endosperm is used for biochemical and molecular studies while the embryo can be grown for seed production; in this way preselected individuals and/or genotypes can be multiplied, it can reduce the breeding population and experimental costs meth biot

half-hardy annuals: plants that will survive some frost, but not a long freeze phys

half-life (time): the time required for one-half the atoms of a given amount of a radioactive substance to decay phy biot >>> radio carbon dating >>> isotope

half-shrub >>> suffrutex

half sibs: progeny with only one common parent gene

half-sib progeny selection >>> method of overstored seeds (syn remnant seed procedure) >>> Figure 4

halomorphic: a soil that has high levels of salt agr

halophilic >>> halophilous

halophilous: a salt-loving organism, adapted to a high-salt environment (e.g., in a salt marsh) bot

halophytes: plants that grow in saline soil bot

HANAHAN transformation procedure: an optimized procedure for the transformation of Escherichia coli with plasmid DNA using CaCl2 biot

hand-dibbed: sowing individual seeds by hand according to a special plot design; it is mainly used for F1 seeds when they are rare or seeds that need special care meth

hand weeding: manually removing the undesirable species inhibiting the growth of valued species meth agr

hanging-drop culture (technique): a method of microscopic examination of organisms or particles suspended in a drop on a special concave microscopic slide meth micr

haplodiploidy: sex differentiation in which males are haploids and females diploids bot

haploid: applied to a cell nucleus that contains one of each type of chromosome (i.e., one set of chromosomes); designated “n” gene >>> monoploid

haploid breeding: it is the production of >>> homozygous lines for >>> true-breeding lines; the desired trait will be carried through unchanged to subsequent generations only if the trait is present in homozygous form; to obtain homozygous breeding lines, originally self-pollination is needed over 6-8 generations, which is a very time-consuming and costly process; nowadays homozygous lines of some plant species (e.g. tobacco, barley, potatoes, rape, wheat etc.) can be produced from >>> gametes, which contain only one (haploid) set of chromosomes; in most cases unripe pollen is placed on a suitable >>> culture medium, where it develops into plants with a single set of chromosomes (haploid androgenesis); ovaries may also be used as the source material, although this is less common (haploid >>> parthenogenesis); following a cultivation period of 3-4 weeks, the haploid plantlets are treated with >>> colchicines in order to induce duplication of the chromosomes; resulting cells produce >>> "double haploids", fully homozygous plants which produce identical offspring meth

haploidization: the process whereby diploid somatic cells become haploid during a parasexual cycle or by experimental means cyto meth

haploid parthenogenesis: the situation in which the unfertilized egg hatches and develops normally to produce a viable male adult whose cells contain only the haploid number of chromosomes cyto

haplo-insufficiency: situation where one normal copy of a gene alone is not sufficient to maintain normal function; it is observed as a dominant mutation on one allele (or deletion of it) resulting in total loss-of-function in a diploid cell because of the insufficient amount of the wild-type protein encoded by the normal allele on the other haplotype gene >>> hemizygote

haplontic: organisms in which meiosis occurs in the zygote resulting in four haploid cells bot

haplophase: that part of the life cycle in which the gametic chromosome number is found in reproduction cells bot

haplosis: the meiotic division resulting in haploid cells and/or gametes bot

haplosomic: the situation in which the homologue of a pair of chromosomes is missing in somatic cells gene >>> monosomic >>> Figure 37

haplotype: a combination of alleles of closely linked loci found in a single chromosome; sometimes, a combination of particular nucleotide variants within a given DNA sequence gene biot

hardening (off): the gradual process of acclimating plants started indoors to outside conditions (e.g., placing them in a sheltered location outdoors for increasing lengths of time over a period of days) meth phys hort agr >>> acclimatization

hardiness: the capability of a plant to withstand environmental stress phys agr


hard-leafed >>> sclerophyllous

hard seed: a seed that is dormant due to the nature of its seedcoat, which is impervious to either water or oxygen seed

hardseedness >>> hard seed

hard-shelled seed >>> hard seed

hard wheat: tetraploid wheat, Triticum durum, used for high-quality noodles, bread, and pastas agr >>> Table 1


hardwood: a term used to describe broadleaf, usually deciduous, trees such as oaks, maples, ashes, elms, etc.; it does not refer to the hardness of the wood fore hort

HARDY-WEINBERG law (equilibrium): states that in an infinitely large, interbreeding population in which mating is random and in which there is no selection, migration, or mutation, gene and genotype frequencies will remain constant from generation to generation gene bio

harlequin chromosome >>> sister chromatid exchange (SCE)

harrow: an agricultural implement with spikelike teeth or upright disks, for leveling and breaking up clods in ploughed land or experimental plots; to draw a harrow over soil agr

harvest index (HI): a measurement of crop yield; the weight of a harvested product (e.g., grain) as a percentage of the total plant weight of a crop, or more general, the proportion of the biological yield to economic yield phys >>> Table 33

haulm: stems or stalks collectively, as of peas, beans, or hops, or a single stem or stalk bot

haustorium (haustoria pl): in certain parasitic fungi, an outgrowth from hypha that penetrates a host cell in order to absorb nutrients from it; in some parasitic angiosperms, outgrowth of the roots; in endosperm development, nutrient-gathering outgrowths toward surrounding tissue of the developing endosperm bot phyt phys

hay: herbage, as grass, clover, or alfalfa, cut and dried for use as forage agr

head: an inflorescence in which the floral units on the peduncle are tightly clustered, surrounded by a group of flowerlike bracts called an involucre (e.g., in sunflower) bot

head components: generally, all components of the inflorescence of grain and grass crops agr

head shattering: a preharvest lost of kernels in cereals caused by loose seeds inside the spikelets and mechanical shattering (wind, etc.) agr

heading: emerging spikes (i.e., from initial emergence of the inflorescence from the boot until the inflorescence is fully exerted) phys; in viticulture, to shorten or prune the trunk when it reaches the desired height; done in an effort to focus growth on the lower shoots hort

heartwood: the inner core of a woody stem, wholly composed of nonliving cells and usually differentiated from the outer enveloping layer (sapwood) by its darker color fore hort

heat filter: absorption glass filter that attenuates infrared radiation, but transmits light in the visible wavelength range micr

heat shock protein (HSP): when certain plants are exposed to high temperature, heat shock proteins are synthesized; they provide thermal protection to subsequent heat stress phys >>> stress protein(s)


heating: gentle heating of the slide over a spirit or other flame flattens the cells, sticks them to the glass slide and cover slip and spreads the chromosomes, whether in prophase or metaphase prep cyto

heaving: lifting effect of the soil due to alternate freezing and thawing; it may result in the lifting up of plants and may tear them loose from the soil or may shear off roots agr

heavy feeder: a plant that requires a great amount of nitrogen because of its speedy growth (e.g., squash, potato, tomato, etc.) agr

heavy soil: a soil that has a high content of clay and is difficult to cultivate agr

hectare: equals 10,000 square meters equals 2.471 acres agr

hedgerow: a row of bushes, trees, or special plants forming a hedge agr

heel: a piece of the old branch or shoot that is detached from the old branch or shoot along with a cutting made hort meth

heeling in: temporarily covering the base of a plant with soil for a short time (e.g., stecklings of sugarbeet during the winter) in order to prevent frost damage of cold-sensitive genotypes agr hort meth

heirloom plant: a plant that was developed and in cultivation sometime in the past agr evol >>> heirloom variety

heirloom variety >>> heritage seeds

hematoxylin staining: a method used as an early indicator of aluminum toxicity effects on the apices of young, developing roots of cereals grown in nutrient solution meth

hemialloploid: not a normal full alloploid but a segmental alloploid, in which some parts of the unified genomes show some degree of structural conformity cyto

hemiautoploid: autopolyploids with a certain degree of differentiation between the diploid sets of chromosomes, either by a subsequent differentiation of previously homologous sets of chromosomes or by spontaneous or induced intervarietal or subspecies hybridization cyto

hemicellulose: a heterogeneous group of compounds that in plant cell walls form part of the matrix within which cellulose fibers are embedded chem phys

hemichromosome: a chromosome split into chromatids without previous reduplication at interphase cyto

hemigamy: where gametes fuse but the nuclei do not, forming a dikaryon bot

hemihaploid: individuals with half of the normal haploid chromosome number cyto

hemimethylation: the state in which a DNA duplex is methylated in one strand but unmethylated in the other gene biot

hemiploid: individuals with half of the somatic chromosome number cyto >>> haploid

hemizygous: an individual, generally diploid, having a given gene and/or allele present once (e.g., in monosomics or haploids) gene >>> Figure 37

herb(s): a small, nonwoody, seed-bearing plant in which all the aerial parts die back at the end of each growing season bot

herbaceous: nonwoody, as applied to kinds of plant growth bot >>> herb(s)

herbage: plant material used for animal feed agr

herbarium: a collection of dried, preserved, and systematically classified plants bot tax

herbarium beetle: Cartodere filum; eats the spores of certain fungi (e.g., Lycoperdon, smuts, etc.) that are attached to the plant material of a herbarium phyt

herbarium glue: an adhesive that minimizes cracking, discoloration, and shattering with age; it is used in fastening plant specimens to the herbarium sheet meth bot

herbarium paste >>> herbarium glue

herbicide: a chemical substance that suppresses or eliminates plant growth; it may be a nonselective or selective weed killer phyt

herbicide tolerance: the ability of some plants to tolerate herbicides; it is a task of genetic engineering to modify crop plants for this trait in order to apply herbicides against weeds in the field phyt biot

hercogamy >>> herkogamy

hereditary: transmissible from parent to offspring or progeny gene

hereditary determinant: any genetically acting unit of an organism that is replicated and conserved transferred from generation to generation gene

hereditary factor >>> hereditary determinant

heredity: the transmission of genetic characters from one generation to the next generation; it operates primarily by the germ cells in sexually reproducing species gene

heritability: a measure of the degree to which a phenotype is genetically influenced and can be modified by selection; it is represented by the symbol h²; this equals Vgen/Vphe where Vgen is the variance due to genes with additive effects and Vphe is the phenotypic variance; there are two types of heritability: (1) broad-sense heritability, hbb² = Vgen/ Vphe and (2) narrow-sense heritability, hnb² = Vadd/ Vdom gene stat >>> genetic variance (Vgen)  >>> Figure 38 >>> Table 34

heritable >>> hereditary

heritage seeds: nonhybrid seeds of old varieties that have been passed from generation to generation agr

herkogamy: pollination by the neighbor individual, population, or species bot

hermaphrodite: a plant having both female and male reproductive organs in the same flower bot >>> Table 18

hermaphroditic: reproductive organs of both sexes present in the same individual or in the same flower in higher plants bot >>> bisexual >>> Table 18

hesperidia: a berrylike fruit with papery internal separations or septa and a leathery, separable rind (e.g., orange, lemon, lime, grapefruit) bot

heteroallele: an allele that differs from other alleles of the same gene by nucleotide differences at different sites within the gene; in contrast with “true” alleles, of which only four are possible at each site within the gene gene

heteroallelic >>> heteroallele

heteroauxin: an obsolete term for the auxin 1H-indole-3-acetic acid (IAA) chem phys >>> indole-3-acetic acid

heterochromatic: of chromosome regions or whole chromosomes that have a dense, compact structure in telophase, interphase, and early prophase cyto

heterochromatin: the chromosome material that accepts stains in the interphase nucleus (unlike euchromatin); such regions, particularly those containing the centromeric and nucleolus organizers, may adhere to form a chromocenter; some chromosomes are composed primarily of heterochromatin; these are termed heterochromosomes, such as Y chromosome in some species cyto

heterochromosome: any chromosome that differs from the autosomes in size, shape, and behavior cyto

heteroduplex analysis - Heteroduplexanalyse f a method of detecting gene mutation by mixing PCR-amplified mutant and wild-type DNA followed by denaturation and reannealing; the resultant products are resolved by gel electrophoresis, with single base substitutions detectable under optimal electrophoretic conditions and gel formulations; large base pair mismatches may also be analyzed by using electron microscopy to visualize heteroduplex regions meth biot cyto

heteroduplex DNA: a double-stranded DNA molecule formed by the annealing of strands from two different sources, as opposed to homoduplex, which has homologous strands; as a result, there are regions noncomplementary and showing abnormalities in the form of extra loops gene

heteroecious: a species that produces male and female gametes on different individuals bot >>> dioecious; the requirement of a pathogen for two host species to complete its life cycle phyt

heterofertilization: fertilizing of the nuclei of endosperm and embryo-forming cells by genetically different gametes bot

heterogamete >>> anisogamete

heterogam(et)ic: a species that sexually reproduces by two types of gametes bot

heterogamy: reproduction involving two types of gametes bot

heterogeneity index: a measure for genetic differences within populations gene

heterogenetic: chromosome pairing between more or less different genomes in amphiploids cyto

heterogenic: gametes or populations differing in alleles or genes gene

heterograft: heterologous graft; the scion and rootstock derive from different species hort

heterohistont: an individual or cell aggregate that is composed of tissues of genetically different origin bot

heterokaryon: cells with two or more nuclei that are genetically non-identical bot

heterokaryotype: a chromosome complement that is heterozygous for any sort of chromosome mutations cyto

heterolabeling: a chromosomal labeling pattern due to induced or spontaneous exchange of labeled and nonlabeled half-chromatids cyto

heterologous gene expression: expression of a gene in another host biot

heterologous probing: probing at low stringency with a DNA fragment that originates from another organism and thus does not have an identical counterpart in the target DNA; often it gives significant signals because of sequence conservation biot

heteromeric: genes that control the determination of a trait by joint gene action, but each of them shows a definitely different contribution to the final product gene

heteromorphic: chromosomes that differ in size and/or shape; the term is also used for meiotic pairing configuration, which is composed of different chromosomes and/or chromosome segments gene

heteromorphic bivalent: a bivalent consisting of nonhomologous chromosomes or segments cyto

heteromorphous >>> heteromorphic

heteromorphy >>> heteromorphic

heterophylly: the production of more than one leaf form on a plant species; in developmental heterophylly, juvenile leaves may differ from adult ones bot

heterophyte: a plant that is dependent upon another, obtaining its nourishment from other living or dead organisms, such as parasites or saprophytes bot

heteroplasmic >>> alloplasmic

heteroplasmonic >>> alloplasmic

heteroplastidic: cells whose plastids are different in shape bot

heteroploid: deviating chromosome numbers from the standard chromosome set cyto

heteropycnotic: chromosomes or chromosomal segments that show a different coiling or staining pattern cyto

heterosis: the increased vigor of growth, survival, and fertility of hybrids, as composed with the two homozygotes; it usually results from crosses between two genetically different, highly inbred lines; it is always associated with increased heterozygosity; in breeding, three types of heterosis are distinguished: (1) F1 yielding more than the mean of the parents, (2) F1 yielding more than the best yielding parents, (3) F1 yielding more than the best yielding variety; for the genetic basis of heterosis two hypotheses have received the most attention: dominance hypothesis and overdominance hypothesis gene >>> Figure 2 >>> Table 35

heterosomal: a chromosome mutation involving nonhomologous chromosomes cyto

heterosome: a chromosome that is deviating from the standard chromosomes in size, shape, or behavior cyto

heterospory: the production of spores of two different types of the same plant bot

heterostyly: a polymorphism among flowers that ensures cross-fertilization through pollination by visiting insects; flowers have anthers and styles of different length bot

heterothallic: describes yeast strains that have a fixed mating type and as a result can only mate when mixed with a strain of the opposite mating type bot

heterotroph: an organism that is unable to manufacture its own food from simple chemical compounds and, therefore, consumes other organisms phys

heterozygosity: the presence of different alleles of a given gene at a particular gene locus gene >>> Tables 9, 10

heterozygote: a diploid or polyploid individual that has different alleles on at least one locus gene >>> Tables 9, 10

heterozygotic >>> heterozygous

heterozygous: the condition of having unlike alleles at corresponding loci gene

hexaploid: with six sets of chromosomes cyto

hexasomic: a cell or individual showing one chromosome six times cyto

hexokinase: an enzyme that catalyzes the phosphorylation of hexose sugars chem phys

hexose: a monosaccharide sugar that contains six carbon atoms chem phys

HI >>> harvest index

hibernaculum: the winter resting body of some plants, generally a bud-like arrangement of potential leaves bot

hibernating organ >>> hibernaculum

hidden hunger: the nutritional status of a growing plant when it is experiencing the deficiency of a nutrient but this effect is not severe enough to produce visible deficiency symptoms, i.e., one stage below the critical level; it results in loss of yield phys agr

Hieracium type: apospory where the embryo sac is derived from a somatic cell, usually from the center of the nucellus; three mitoses lead to a mature eight-nucleate, unreduced embryo sac bot

hierarchical classification: the grouping of individuals by a series of subdivisions or agglomerations to form characteristic “family trees” or dendrogram of group stat

high oleic: in sunflower breeding, seeds that contain a trait for high oleic fatty acid content in its oil; a premium oil used in the snack food industry agr

high oleic: in sunflower breeding, seeds that contain a trait for high oleic fatty acid content in its oil; a premium oil used in the snack food industry agr

high-velocity microprojectile transformation: a procedure for introduction of DNA into plant cells; for example, gold particles are coated with DNA and propelled at high speed through the target cell walls by means of an electrical or gunpowder discharge biot

high yielding variety: the phrase refers to "modern" (post 1960) crop varieties having a much higher grain yield potential (5-10 t/ha) than traditional tall varieties; in maize, usually hybrids or composites are meant; in wheat and rice, usually stiff strawed, short-statured varieties, also hybrids were developed; high yielding varieties are more responsive to fertilizer application than local tall varieties and their large-scale cultivation triggered the >>> "Green Revolution" agr

hill plot >>> Figure 33

hilum (hila pl): the scar on a seed that marks the point at which it was attached to the plant bot

hips: seed pods (fruits), for example, in roses or apples, that are formed after a flower’s petals fall if the bloom was pollinated hort

histidine (His): a basic, polar amino acid that contains an imidazole group chem phys

histogram: a bar graph of a frequency distribution in which the bars are displayed proportionate to the corresponding frequencies stat

histone: one of a group of basic, globular, simple proteins that have a high content of the amino acids arginine and lysine; it forms part of the chromosomal material of eukaryotic cells and appear to play an important role in gene regulation chem phys cyto

hitchhiking effect: genes favored in a population by close linkage with other genes, which are positively selected evol gene

hole seeding >>> dibbling (seed)

holocentric: applied to chromosomes with diffuse centromeres such that the properties of the centromere are distributed over the entire chromosome cyto

holokinetic >>> holocentric

homeobox: a characteristic DNA sequence of 180 bp that codes for the 60-amino-acid DNA-binding domain of some developmentally important regulatory genes; mutations in the homeobox can have homeotic effects gene biot

homeostatic mechanism: a physiological process that contributes to the maintenance of a relatively stable internal environment in a multicellular organism phys

homeotic gene(s): a class of genes that determines the identity of an organ, segment, or other structural unit during development; it controls the identity of, for example, floral organs gene

homeotic mutation: a mutation that causes one body structure to be replaced by a different body structure during development gene

homoallelic: applied to allelic mutants of a gene that have different mutations at the same site gene

homoduplex DNA >>> heteroduplex DNA

homoeologous: partially homologous; chromosomes or genomes that are believed to have originated from ancestral homologous chromosomes cyto

homoeologous group: series of two or more chromosomes with similar but not homologous chromosomes (e.g., in hexaploid wheat or oat) cyto

homoeostasis: the tendency of a biological system to resist change and to maintain itself in a state of stable equilibrium bio >>> genetic equilibrium

homogametic: producing only male or female gametes bot

homogamic: of matings between individuals from the same population or species gene

homogamous: hermaphroditic flowers showing synchronized function of male and female sex organs bot

homogamy: the preference of individuals to mate with others of a similar genotype or phenotype; in botany, the condition in which male and female parts of the flower mature simultaneously bot

homogenic: in cytology, sometimes it refers to chromosome pairing between morphologically identical genomes in amphiploids cyto

homograft >>> heterograft

homologous: applied to organs and chromosomes; both showing identical structures cyto bot

homologous genes: genes with a common ancestor, generally used to describe genes from different species but which are similar and have the same function gene

homology: fundamental similarity; in molecular biology, the degree of identity between two sequences from related organisms biot

homomeric: genes that control the determination of a trait by joint gene action, and each of them shows a similar contribution to the final product gene

homomorphic bivalent: a bivalent that is composed by two homologous chromosomes (i.e., in size and shape) cyto

homoplasmic: cells or individuals that carry two or more different types of cytoplasmic components bot

homoplasmonic >>> homoplasmic

homopolymer-tailing: attachment of identical nucleotides to the 3' end of a DNA molecule that can be achieved with terminal deoxynucleotide transferase biot

homothallic strains: in yeast, strains that are capable of switching mating type and thus of mating with themselves, forming zygotes, asci, and spores under appropriate conditions bot

homospory: a condition in which an organism produces only one type and size of spore, e.g., microspores bot

homozygosity: the presence of identical alleles at one or more loci in homologous chromosomal segments gene >>> Table 9

homozygote: a cell or organism having the same allele at a given locus on homologous chromosomes gene >>> Table 9

homozygous: having identical rather than different alleles in the corresponding loci of a pair of chromosomes and therefore breeding true gene >>> Table 9

honeybee: any bee that collects and stores honey (e.g., Apis mellifera) and contributes to improved seedsetting in cross-pollinating crops (e.g., rapeseed, fruit trees, etc.) zoo seed

honeycomb design: in a honeycomb design, the plant at the center of the hexagon is compared with every other plant within the hexagon; a plant is chosen only if it is superior to every other plant in the hexagon; it was developed for selecting individual plants in a population; seeds or plants are usually spaced equidistantly from one another in a hexagon pattern; plants are spaced far enough apart that they cannot compete with adjacent individuals; homogeneous checks can be included; the size of the hexagon determines the selection intensity; it is used to minimize adverse effects of interplant competition stat >>> Figure 32

honeydew: a sticky exudate containing conidia, which is produced during one stage of the life cycle of the fungus Claviceps purpurea phyt bot >>> ergot

hook climber: a plant that climbs by the aid of hooks or prickles (e.g., roses) hort >>> climbing plants

hordecale: an amphiploid hybrid between cereal species of the genera Hordeum and Secale, in which Hordeum species served as donors of the cytoplasm bot

hordein >>> prolamin

Hordeum bulbosum procedure: a method for producing zygotic haploids in barley by crossing Hordeum bulbosum with Hordeum vulgare genotypes; after formation of zygotes the wild H. bulbosum chromosome are subsequently eliminated during embryogenesis, which results in haploid H. vulgare plants biot >>> Figures 17, 26 >>> Table 7

horizontal resistance: resistance conditioned by polygenes or quantitative genes; it is race nonspecific in nature and does not reveal a gene-for-gene hypothesis; the type of resistance is difficult to identify phyt

hormone: a regulatory substance, active at low concentrations, that is produced in specialized cells but that exerts its effect either on distant cells or all cells to which it is conveyed via tissue fluids in the organism phys

horticulture: the science or art of cultivating flowers, fruits, vegetables, or ornamental plants (e.g., in a garden, orchard, or nursery) hort

hortus siccus: a collection of specimens of plants carefully dried, preserved, and described for botanical purposes and comparisons of mutants, etc. bot meth >>> herbarium

host - Wirt m: a living organism harboring a parasite and its cells and metabolism are used for the growth of pathogens; plant host can be classified by: (1) importance: (a) primary or principal hosts, (b) secondary hosts, (c) intermediate hosts, (d) accessory hosts, (e) accidental hosts, and (f) definite or final hosts; (2) season: (a) winter hosts and (b) spring hosts; (3) other functions: (a) alternative, alternate, or differential hosts, (b) transport or transfer hosts phyt

host cell - Wirtszelle f: a cell whose metabolism is used for the growth of a pathogen phyt

host-mediated restriction: a mechanism by which bacteria prevent infection by phages originating from other bacteria; restriction also acts against unmodified plasmid DNA in transformation experiments; restriction endonucleases cleave the foreign DNA while the host DNA is protected from cleavage by specific methylation biot

host plant >>> host

host-parasite specificity: the ability of a pathogen to pathogenize a specific group of plants phyt

host range: the spectrum of genotypes that can infect a specific pathogen or pest; in molecular biology, hosts in which a phage or plasmid can replicate; restriction is one factor that can limit the host range of plasmids or phages phyt biot

host resistance - Wirtsresistenz f: the result of genetic manipulation of the host which renders it less susceptible to pathogens that would or do attack the host phyt

host species >>> heteroecious

hot spot: in genetics, one of sites tending to mutate frequently gene

housekeeping enzymes: enzymes present in all cells capable of normal metabolism; they are essential for the synthesis or breakdown of proteins, nucleic acids, and lipids, for glycolysis and respiration and for many standard metabolic pathways phys

housekeeping genes: genes whose products are required by all cells at all times gene >>> housekeeping enzymes

hull - Spelze f: usually the hard, tightly adhering, outer covering of a seed or caryopsis, which is composed of the pericarp in some species and the lemma and palea in others seed; the persistent calyx at the base of some fruits, such as strawberry bot

hull: to remove the hull seed prep >>> dehull

huller-scarifier: a seed conditioning machine; it removes hulls or pods from seeds by an abrading or rubbing action seed >>> Table 11

humic acid - Huminsäure f: a mixture of dark-brown organic substances that can be extracted from soil with dilute alkali agr

humification: the development of humus from dead organic material agr

humus - Humus m: decomposed organic matter of soils agr

husk: the leaf sheaths of an ear of maize; the lemma and palea in other grass species or the dry outer cover of a coconut; the dry outer covering of some fruits or seeds (e.g., cereal grain) bot >>> dehusk

hyaline: clear, transparent bot

hyaline grain >>> hyaline

hypersensitivity >>> resistance

hybrid: any sort of sexual or somatic combination of genetically more or less differentiated parental cells, individuals, or taxa; specifically, an individual plant from a cross between parents of differing genotypes; any heterozygote represents dissimilar alleles at a given locus; or a hybrid graft gene >>> Figures 2, 18, 31

hybrid breakdown >>> hybrid lethality

hybrid breeding syn heterosis breeding: the discovery of heterosis has been recognized as one of the major landmarks of plant breeding; in comparison to inbred lines and homozygous material, the phenotypic superiority of heterozygotes is the basis of hybrid breeding; it is exploited for production of hybrid, synthetic, and composite varieties; hybrid breeding can be performed using traditional breeding techniques, or the process can be hastened using gene marker technology to rapidly identify parents with desired genes for certain attributes; numerous commercial crops are hybrids with increasing tendency; seeds from a hybrid variety, if planted, will not deliver the same benefits as the original seeds and after several offspring will have lost the desired qualities from the original hybridization meth

hybrid chlorosis: plant and/or leaf chlorosis due to interacting genes and/or cytoplasm of parental lines in a hybrid gene

hybrid complex: masking morphological differences of parental lines in a hybrid plant gene

hybrid heterosis >>> heterosis

hybrid inviability: reduced vigor of hybrid plants compared to their crossing parents gene

hybridization: a method of breeding new varieties that applies crossing to obtain genetic recombination; in genetics, the fusion of unlike genetic material, such as sexual organs or DNA; in molecular biology, pairing of complementary DNA and/or RNA meth biot >>> Figure 31

hybridization probe: labeled nucleic acid molecule used to detect complementary DNA sequences after hybridization biot

hybridization stringency - Hybridisierungsgrad m: the percentage of nucleotides, which must match on two unrelated single-stranded nucleic acid molecules before they will base pair with each other to form a duplex, given a certain set of physical and chemical conditions; the hybridization stringency is used to determine when a hybridization probe and a target nucleic acid will come together, and can be set by varying the conditions; in general, if the percentage of matching nucleotides is lower than 70 %, the two single-stranded nucleic acid molecules are considered nonhomologous and any hybridization is considered nonstringent prep biot

hybrid lethality syn hybrid sterility: the failure of hybrids to produce viable offspring gene

hybrid necrosis >>> hybrid lethality

hybrid plant >>> hybrid

hybrid seed production: the production of hybrid seeds by combination of more or less defined parental forms; usually those hybrid seeds are more productive or more suitable than pure lines; they are used for subsequent growing and commercial production of a crop seed >>> Figures 2, 18, 22, 23, 29 >>> Table 5

hybrid selection: the process of choosing plants possessing desired traits among a hybrid population meth

hybrid sterility syn hybrid lethality: the failure of hybrids to produce viable offspring gene

hybrid variety: a variety produced from the cross fertilization of inbred lines with favorable combining ability; the progeny is homogeneous and highly heterozygous; it can be produced by (a) two inbred lines, (b) single crosses, (c) a single cross and an open-pollinated or a synthetic variety, or (d) two selected clones, seed lines, varieties, or species seed >>> Figures 2, 29

hybrid vigor: the increase in vigor of hybrids over their parental inbred types gene >>> heterosis >>> Figure 18

hybrid weakness: the decrease in vigor of hybrids below their parental inbred types; e.g., in rice a hybrid weakness phenomenon is controlled by a set of complementary genes, Hwc1 (hybrid weakness c) and Hwc2; the Hwc2 gene is prevalent among temperate Japonica rice but not among tropical Japonica or Indica rices; the chromosomal location of the Hwc2 locus was determined from the segregation in the F1 hybrids made between recombinant inbred lines and the cultivar `Jamaica'; Hwc2 was located between the two restriction fragment length polymorphism loci, XNpb264 and XNpb197 on chromosome 4 (ICHITANI, K. et al., 2001) gene

hybrid zone: a geographic area where different populations of species meet and hybridize after a period of geographic isolation eco

hydathode: an epidermal structure specialized for the secretion or exudation of water bot >>> guttation

hydratation: the status of imbibition of the cytoplasm phys

hydrate: any of a class of compounds containing chemically combined water chem

hydration: the process whereby a substance takes up water agr

hydraulic seeding: a method of planting grass seed by spraying it in a stream of water, which may contain other materials such as nutrients meth agr

hydrogen peroxide test: a quick test to determine seed viability; in response to a hydrogen peroxide soak, viable seeds elongate their roots through a cut in the seedcoat; frequently used in conifer seeds seed

hydrolase: an enzyme that catalyzes reactions involving the hydrolysis of a substrate chem phys

hydrolysat(e): any compound formed by hydrolysis chem

hydrolysis: in soil science, the process whereby hydrogen ions from water are exchanged for cations such as sodium, potassium, calcium, and magnesium, and the hydroxyl ions combine with the cations to give hydroxides chem agr

hydrophytes >>> hygrophytes

hydroponics: the cultivation of plants by placing the roots in liquid nutrient solutions rather than in soil hort

hydroseeding: dissemination of seed hydraulically in a water medium, supplemented by mulch, lime, and fertilizer meth fore hort

hydrotaxis: movement of an organism toward or away from water bot

hydroxide: a chemical compound containing the hydroxyl group chem

hygrometer: any instrument for measuring the water-vapor content of the atmosphere prep

hygrophytes: plants that can tolerate excess of water bot

hygroscopic(al): water attracting; plants or part of them becoming soft in wet air and hard in dry air bot

hygroscopic water: water that is adsorbed on to a surface from the atmosphere agr

hypanthium: a cup-like or tube-like enlargement of the floral receptacle or base of the perianth that surrounds the gynoecium and fruits bot

hypermorph: a mutant gene which causes an increase in the activity that it influences gene

hyperplasia: the enlargement of tissues by an increase in the number of cells by cell division bot

hyperploidy: having additional chromosome complements compared to the standard chromosome set cyto

hypersensitive resistance >>> hypersensitivity

hypersensitive site: a region of DNA located in a chromatin structure that makes it more sensitive to attack by endonucleases than DNA sites, located elsewhere in the chromatin; the presence of hypersensitive sites is correlated with transcription of adjacent DNA sequences in eukaryotic cells gene

hypersensitivity: the response to attack by a pathogen of certain host plants in which the invaded cells die promptly and prevent further spread of infection phyt; resistance

hypertonia >>> hypertonicity

hypertonic: a solution whose osmotic potential is less than that of living cells, causing water loss, shrinkage, or plasmolysis of cells phys

hypertonicity >>> hypertonic

hypertrophy: the enlargement of tissues by an increase of the size of the cells bot >>> hyperplasia

hypha (hyphae pl): a tubular, threadlike filament of fungal mycelium bot

hypocotyl: part of the embryonic shoot or seedling located below the cotyledon and above the radicle bot

hypogeal: living or growing underground bot

hypogeal emergence: a type of emergence characterized by the elongation of the epicotyl and the cotyledons remaining below ground that is common in monocots bot

hypogean >>> hypogeal

hypoplasia: abnormal deficiency of cells or structural elements bot

hypoploidy: having missing chromosome complements compared to the standard chromosome set cyto

hypostatic epistasis >>> epistasis

hypotonic: of or designating a solution of lower osmotic pressure than another, as opposed to hypertonic phys

hypsometer: any of several tools or instruments designed to measure the height of trees fore

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