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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 or in modified design as book by CRC Press, Taylor & Francis Group, Boca Raton, USA

Paris green: a very nasty pesticide containing copper and arsenic, which was widely used until replaced with DDT phyt

parthenote: a cell or individual resulting from parthenogenesis cyto

partially balanced design (partially balanced incomplete block design) - teilweise balancierte Versuchsanlage f: a design is partially balanced with respect to an association scheme if the number of blocks containing two points depends only on which class of the partition contains the given pair of points stat

partially balanced incomplete block design (PBIB): it refers to an experimental design where the residual variance of the difference between the candidates may adopt one out of only two different values stat meth >>> partially balanced design

partial Latin square: an n x n array whose cells are either empty or contain a symbol from an alphabet of size n, such that each symbol occurs at most once in each row or column, e.g., a >>> Latin rectangle stat

pasteurization: named after the French L. PASTEUR; a technique of heating wine, milk, food, or soil to about 80 °C in order to destroy harmful >>> microorganisms; this temperature does not lead to a complete sterilization, for which a temperature of about 120 °C is required meth phyt

PBCC >>> Plant Breeding Coordinating Committee

..... more on CD-ROM

pedology: the science of soils, including their classification, formation, structure, and composition agr

perennial: a plant that normally lives for more than two seasons and that, after an initial period, produces flowers annually; among perennial crops are: oil palm, cacao, rubber tree, rye grass, tall fescue, alfalfa etc bot

persistence: the act or fact of persisting phyt

persistent >>> persistence

persistent modification: nonheritable morphological or physiological changes over a more or less long period of generation cycles induced by varying abiotic or biotic influences gene

pest: any form of plant or animal life, or any pathogenic agent, injurious or potentially injurious of plants or plant products phyt

pest resistance: resistance to any form of plant or animal life or any pathogenic agent phyt

pesticide: a chemical preparation for destroying plant, fungal, or animal pests phyt

petal: one of the inner floral leaves, usually brightly colored and borne in a tight spiral or whorled carolla bot

petiole: the stalk by which a leaf is attached bot

PETRI dish: a covered glass container in which cells, organs, seeds, or microorganisms are cultured prep

P1 generation >>> parental generation

PGIPs >>> polygalacturonase-inhibiting proteins

phage: the abbreviation for bacteriophage (i.e., a virus that infects bacteria) bio

phase-contrast microscopy: light rays passing through an object of high refractive index that will be retarded in comparison with light rays passing through a surround medium with a lower refractive index; the retardation or phase change for a given light ray is a function of the thickness and the index of refraction of the material through which it passes; thus in a given unstained specimen, transparent regions of different refractive indexes retard the light rays passing through them to differing degrees; such phase variations in the light focused on the image plane of the light microscope are not visible to the observer; the phase contrast microscope is an optical system that converts such phase variations into visible variations in light intensity or contrast; it allows observation of the cell and structures (even living) without staining and degrading treatments micr

phasmid: a cloning vector that has the possibilities to replicate as a plasmid or as a phage; the two modes of replication are usually functional in different bacterial species biot

phellogen: a layer of plant tissue outside of the true cambium, giving rise to cork tissue bot

phene: the phenotype of the plant, which is a product of the gene (gene > DNA > transcription > RNA > processing > translation > protein) and the interaction with the environment gene >>> phenotype

phenocopy: a nonhereditary phenotypic change that is environmentally induced during a limited developmental phase of an organism; it may mimic the effect of a known genetic mutation gene

phenogenetics: a branch of genetics that studies the interaction of the genotype and its manifestation gene

phenol: a chemical used to remove proteins from DNA preparations biot

phenol test (reaction): the color produced in the grain of, for example, wheat and barley, by treatment with a one percent solution of phenol in water seed meth

phenology: the study of the impact of climate on the seasonal occurrence of flora eco

phenotype: the observable manifestation of a specific genotype (i.e., those properties on an organism, produced by the genotype in conjunction with the environment) gene

phenotypic expression: the manifestation of a particular gene resulting in a particular phenotype gene

phenotypic plasticity: the capability of a genotype to assume different phenotypes gene

phenotypic segregation: the phenotypic differentiation patterns of cells or individuals in segregating populations, as opposed to genetic segregation gene >>> Table 2

phenotypic selection: development of a variety based on its physical appearance without regard to its genetic constitution gene

phenotypic variance (VP): the total variance observed in a character; it includes experimental error, genotype × environment interaction and the genotypic variance stat

phenylalanine (Phe): an aromatic, nonpolar amino acid chem phys

pheromone: a chemical exchanged between members of the same animal species that effects behavior (sex attractants, alarm substances, aggregation-promotion substances, trail substances, etc.) phyt bio

Ph locus: a gene that controls homoeologous chromosome pairing in wheat and, similarly, in other allopolyploid plants; the Ph gene restricts pairing between homologous chromosomes in a polyploidy; during evolution a subtelomeric heterochromatin block became inserted into a group of cdc2-like genes on 5B; Ph1 is involved in the regulation of chromatin condensation; it seems likely that this insertion event generated a functional and/or regulatory change at the 5B cdc2-like gene family gene

phloem: a tissue comprising various types of cells that transports dissolved organic and inorganic materials over long distances within vascular plants bot

phosphatase: an enzyme that catalyzes reaction involving the hydrolysis of esters of phosphoric acid chem phys

phosphorus (P): an element that is required by plants in the oxidized form; it is utilized in reactions in which energy is transferred, often involving ATP chem phys >>> mitochondrion

phosphorylation: the addition of a phosphate group to a compound, involving the formation of an ester bond between the reactants phys

photobleaching: photochemical reaction of fluorophores, light, and oxygen that causes the intensity of the fluorescence emission to decrease with time micr

photoinhibition: the slowing or stopping of a plant process by light (e.g., the germination of some seeds) phys

photo-insensitive plants >>> daylength insensitivity

photometry: the measurement of the intensity of light or of relative illuminating power meth micr

photomorphogenesis: changes in plant growth due to light; there is a main plant regulator protein Cop1 that suppresses genes controlling the photomorphogenesis; for example, when a seedling gets exposed to light the Cop1 protein is reduced in the nucleus and photosynthesis is initiated—the seedling becomes green; cryptochromes may interact with photoreceptor-proteins, which can recognize blue light; thus the interaction can “switch-off” the Cop1 protein phys

photon: a packet of light energy phy

photonasty >>> nasty

photoperiod: the relative length of the periods of light and darkness associated with day and night; in many species, floral induction occurs in response to daylength; species have been categorized according to their daylength requirements as short-day, long-day, intermediate-day, or day-neutral phys

photoperiodism: the response of a plant to periodic, often rhythmic, changes in either the intensity of light or to the relative length of day phys

photoreceptor: a pigment that absorbs the light used in various metabolic plant processes that require light phys

photosynthesis: the series of metabolic reactions that occur in certain autotrophs, whereby organic compounds are synthesized by the reduction of carbon dioxide using energy absorbed by chlorophyll from light phys >>> Table 33

pH value: the negative logarithm of the hydrogen-ion activity, expressed in terms of the pH scale from 0-14 chem

phyletic: the evolution by which a race or line is progressively transformed from its ancestral form without branching or separating into related parts evol

phyletic gradualism: the process of gradual evolutionary change over time evol

phyletic series >>> phyletic

phyllode: an expanded petiole resembling and having the function of a leaf, but without a true blade bot

phyllody: the condition in which parts of a flower are replaced by leaf-like structures; often it is a symptom of certain diseases bot

phyllosphere: the surface of a living leaf bot

phyllotaxis: the active arrangement of leaves on a stem or axis bot

phyllotaxy >>> phyllotaxis

phylogenesis >>> phylogeny

phylogenetic: of, pertaining to, or based on phylogeny evol

phylogenetic tree: a diagram showing evolutionary lineages of organisms evol

phylogeny: evolutionary relationships within and between taxonomic levels, particularly the patterns of lines of descent, often branching, from one organism to another evol >>> Figure 10 >>> Tables 1, 14, 17, 49, 50

phylum (phyla pl): an important group of organisms bot

physical map: map of the locations of identifiable landmarks on DNA (e.g. restriction enzyme cutting sites, genes) regardless of inheritance, the distance is measured in base pairs >>> mapping

physiological races: pathogens of the same species with similar or identical morphology but differing pathogenic capabilities phyt

physiologic specialization: the existence of a number of races or forms of one species of pathogen based on their pathogenicity to different cultivars of a host phyt

physiological maturity: the maturity of a seed when it reaches its maximum dry weight; this usually occurs prior to the normal harvest date seed

physiological race: pathogens of the same species with similar or identical morphology but differing pathogenic capabilities phyt

physiologist: a specialist dealing with the functions and activities of living organisms and their parts phys

phytase: an enzyme that catalyzes the breakdown of phytin, the source of inorganic phosphorus in seed metabolism chem phys >>> phytic acid

phytic acid: a myo-inositol 1,2,3,4,5,6-hexakisphosphate and the major storage compound of phosphorous in plants, predominantly accumulating in seeds (up to 4-5 % of dry weight) and pollen; in cereals, phytic acid is deposited in embryo and aleurone grain tissues as a mixed "phytate" salt of potassium and magnesium, although phytates contain other mineral cations, such as iron and zinc; during germination, phytates are broken down by the action of >>> phytases, releasing their phosphorous, minerals and myo-inositol, which become available to the growing seedling; phytic acid represents an anti-nutritional factor for animals phys

phytoalexin(e): an antifungal substance that is produced by a plant in response to damage or infection phyt phys

phytochrome: a photoreversible pigment that occurs in every major taxonomic group of plants; it exists in two interchangeable forms with respect to absorption, a red and a far-red form; Pr phytochrome is receptive to orange-red light (600-680 nm) and inhibits flowering; Pf-r phytochrome is receptive to far-red light (700-760 nm) and induced flowering phys

phytogenetics: synonymous to plant genetics, dealing with inheritance in plants gene

phytohormone >>> plant hormone

phytoncide >>> herbicide

phytopathology: the study of plant diseases phyt

phytosanitary certificate: a certificate from a recognized plant quarantine service that indicates that a sample is substantially free from diseases or pests seed

phytosiderophore(s): nonproteinogenic amino acids developed by plants under conditions of mineral deficiency (especially under iron and zinc deficiency); the production and exudation of phytosiderophores is controlled by several genes; there are crop plants, such as rye, showing a high level of phytosiderophore production and/or exudation toward the rhizosphere phys

phytotoxic: being poisonous to plants phyt

phytotoxin >>> pathotoxin

phytotron - Wachstumskammer f: a group of rooms or a room for growing plants under controlled and reproducible environmental conditions prep meth

pick-up reel: a special device on some harvesters for taking up lodging straw agr

picotee: a type of edging on a daylily flower where the edge is a completely different color than the tepals hort

pigment - Farbkörber m: an organic compound that produces color in the tissue of the plant bot

pileorhiza >>> root cap

piliferous layer >>> root hair

pilose: hairy bot

pilosum: used for describing a hairy ventral furrow, for example, barley grain bot

pilot test: preliminary test or study of the program or evaluation activities to try out procedures and make any needed changes or adjustments stat meth

pin flower: flowers with long styles and short stames bot >>> Table 18

pincers - Pinzette f: a gripping tool consisting of two pivoted limbs forming a pair of jaws and a pair of handles prep

pinching (pinching back, pinching out) >>> disbud

pinna: one of the leaflets of a pinnate leaf bot

pinnate - gefiedert adj: feathered, i.e., a compound leaf that has leaflets arranged on either side of a stalk bot

pinnate leaf >>> pinnate

pinninervate: pinnate-veined; feather-veined bot

pipette: a slender, graduated tube for measuring liquids or transferring them from one container to another prep

pistil: the gynoecium of a syncarpous flower; a pistil includes an ovary, style, and stigma; the stigma is the receptor of the pollen bot >>> Figure 35

pistillate flower: designating a flower having one or more pistils and no stamens bot

pistillody: the conversion of any organ of a flower into carpels (e.g., stamens into pistils or pistillike structures) bot >>> pistillate flower

pistillum >>> pistil

pit: in botany, a term used for the widening in the center of the ventral furrow in some wheat and barley grains bot

pith: a tissue that occupies the central part of a stem (composed of parenchyma cells) bot

pixel: a picture (pix) element (el); it refers to points of information used to map images; pixels exist in arrays with specific x- and y-coordinates phy meth

placenta: the part of the ovary wall formed from the fused margins of the carpel or carpels on which the ovules are carried bot

placentation: the position of the placenta within the carpel; it may be parietal (on the walls), axile (on the axis), basal (on the basis), or free-central bot

plan apochromatic objective lens (plan apo): a modern, high-resolution microscope objective lens designed with high degrees of corrections for various aberrations; it is corrected for (1) spherical aberration in four wavelengths (dark blue, blue, green, red), (2) for chromatic aberration in more than these four wavelengths, and (3) for flatness of field; a single plan apo may contain as many as 11 lens elements micr

plantation:an area under cultivation; a closely set stand of trees or special crops that has been planted by humans; a large estate or farm on which crops are raised, often by resident workers; a newly established settlement or a colonyagr hort

plant breeder: a person or organization actively engaged in the breeding and maintenance of varieties of plants, applying a wide range of methods of different scientific disciplines

plant breeding: the application of genetic principles and practices to development of individuals or cultivars more suited to the needs of humans; it uses knowledge from agronomy, botany, genetics, cytogenetics, molecular genetics, physiology, pathology, entomology, biochemistry, statistics, etc.

Plant Breeding Coordinating Committee (PBCC): it serves as a forum regarding issues and opportunities of national and global importance to the public and private sectors of the USA national plant breeding  effort; office at Raleigh (North Carolina State University), USA org

plant density: the rate at which seed or vegetative propagules are placed in a field or experimental planting meth agr

plant hair >>> trichome

plant hormone: a compound that is synthesized by a plant, but is not a nutrient, coenzyme, or detoxification product, and which regulates growth, differentiation or other specific physiological processes phys

plantibodies: antibodies produced in transgenic plants expressing the antibody-producing gene(s) of an animal, e.g., mouse, that had been previously injected with a pathogen (usually a virus) and that infects the plants phyt biot

planting cord: a string of different manufacturing and length used for marking experimental plots, paths, margins between landmarks or applied to mark planting rows prep

plant label: plastic, wood, or other stakes for gardens or experiments to indicate what seeds or material are planted where until they appear, which varieties are included, what sort of evaluation is carried out, etc.; in plant conservation, paper forms to include in drying plant samples, with formal printed forms as permanent labels on herbarium specimens; the minimum information includes the name of the collector, the location collected, the date collected, and the correct identification of the specimen meth agr hort

plantlet: a stage of in vitro culture; the stage after torpedo stage and usually one of the last before a whole plant is generated biot

plantling >>> plantlet

plant passport: an official seed label used for forthcoming marketing; it shows the crop, crop class, e.g., European community grade, inspections, etc. seed >>> passport data

plant pathogenesis-related proteins (PPRP): groups of proteins with different chemical properties produced in a cell within minutes or hours following inoculation, but all being more or less toxic to pathogens phyt

plant pathology >>> phytopathology >>> biological control

plant protection >>> phytopathology >>> biological control

plant variety protection >>> plant variety rights

Plant Variety Protection Act: enacted in 1970 in the United States to provide patentlike protection for seed plant species; prior to 1970, breeders in the industry worked primarily with maize and sorghum, with some efforts directed to alfalfa, cotton, sugarbeet, and certain vegetables; the purpose of the PVPA was to stimulate private plant breeding research and to provide better seed cultivars to farmers and gardeners

plant variety rights: the legal rights of a plant breeder (not necessarily as a person) who has developed a new variety seed

plantation: a closely set stand of trees or special crops that has been planted by humans agr hort

plantibodies: antibodies produced in transgenic plants expressing the antibody-producing gene(s) of an animal biot

planting bar: a hand tool used in making a slit-hole in which trees are planted fore hort

planting cord: a string of different manufacturing and length used for marking experimental plots, paths, margins between landmarks, or applied to mark planting rows prep

plantlet: a stage of in vitro culture; the stage after torpedo stage and usually one of the last before a whole plant is generated biot

plantling >>> plantlet

plant quarantine: the isolation of newly imported plants to ensure that they are not introducing any foreign parasites; the term quarantine may refer to the quarantine station itself, or to the process of testing and purifying the plant material seed meth

plaque: a circular zone of lysis produced by bacteriophage in a colony of bacteria on an artificial medium meth

plaque lift: impression of bacteriophage particles blotted to a filter membrane; the technique is used to screen both with radioactively-labeled DNA or RNA probes or with serological screening of eukaryotic expression libraries biot

plasmagene: an extranuclear hereditary determinant showing no Mendelian inheritance gene

plasmalemma >>> cell membrane

plasmatic: all functions, processes, or properties of the cytoplasm bot >>> cytoplasm

plasmic >>> plasmatic

plasmid: any extrachromosomal hereditary determinant of bacteria; such ring-shaped structures are intensively used for amplification of DNA segment in recent bioengineering approaches; it is capable of self-replication; it can carry genes into a host cell gene >>> Figure 27

plasmid vector: a plasmid or plasmidlike structure used as a carrier for alien DNA segments or genes biot >>> Figure  27

plasmodesm(a) (plasmodesmata pl): cytoplasmic bridges, lined with a plasma membrane that connect adjacent cells; they provide major pathways of communication and transport between cells bot

plasmodium: in cellular slime molds, a vegetative structure consisting of a noncellular, mobile mass of naked protoplasm containing many nuclei bot

plasmogamy: the fusion of the cytoplasm of two or more cells after karyogamy during the process of fertilization cyto

plasmolysis: the result of placing plant cells in a hypertonic solution so that water is drawn out of the cell; the cytoplasm shrinks and the cell membrane is pulled away from the cell wall phys

plasmon: all the extrachromosomal hereditary determinants gene >>> plasmotype

plasmon mutation: a mutation that genetically changes the cytoplasm and/or its hereditary determinants gene

plasmotype: the sum of the extrachromosomal hereditary determinants gene

plastid: one of a group of double-membrane-bound plant-cell organelles that vary in their structure and function (e.g., chloroplasts, leucoplasts, amyloplasts) bot

plastid DNA: organelle DNA that is present in a plastid gene

plastid inheritance: non-Mendelian inheritance that is caused by hereditary factors present in the plastids gene

plastidome >>> plastome

plastidome mutation: mutations that genetically change the DNA of the plastids of a plant cell gene

plastogene: the hereditary determinants located in the plastid gene

plastome: a term usually used for the plastids of a cell or for the genetic information of the plastid DNA bot gene

plastom mutation >>> plastidome mutation

plate: to place on or in special media in a culture dish prep

plating efficiency: an estimate of the percentage of viable cell colonies developing on an agar plate relative to the total number of cells spread onto the plate; the plating efficiency is a function of the tissue, medium composition, plating density, and the phase of the stock culture biot

pleiotropic: an allele or gene that affects several traits at the same time gene

pleiotropy: the phenomenon of a single gene being responsible for a number of different phenotypic effects that are apparently unrelated gene

plesiomorphy: ancestral state of a particular character bot

ploidy: the number of complete chromosome sets in the cell nucleus (e.g., diploid, tetraploid, etc.) cyto

plot: in field experiments, more or less large pieces of land used for planting and evaluation; in forestry, a group of trees, all from the same entry (family, clone, provenance) planted together; a five-tree-plot row is the most common design for forest genetics experiments; in statistics, an experimental unit, to which a single treatment is applied meth agr fore hort stat

plot size: in field experiments, the size, number, and distribution of plots are essential elements; an efficient combination of plot size and plot number is required; larger plots offer smaller between-plot variance, long measurement time per plot, shorter walking time between plots, less edge, and less statistical error; small plots require a higher number of plots in order to achieve the same level of precision of estimates; plot size and shape vary with crops and stage of testing, and among characters under selection; plots are generally small at the initial stage of testing and reach a maximum size during the second and third years of replicated trials; unbordered plots with few replications at one or few locations are used for traits with low heritability; row spacing and plant populations are chosen to be similar to commercial production of crop; seedbed preparation, fertilization, weed control practices, etc., are generally the same as those used for commercial production; the mechanization and computerization of most plant breeding programs have greatly increased a breeder’s ability to handle more plots, populations, etc. meth stat

plot structure: the need for experimental design, even when comparing an unstructured set of treatments, is caused by inhomogeneity in the set of plots; a common form of structure consists of one or more partitions; in the case of a single partition a >>> block design is used; for a pair of partitions >>> nested block designs are applied or a row-column design if the partitions are nested or crossed, respectively stat

plumula: the undeveloped shoot consisting of unexpanded leaves and the growing point (i.e., the terminal bud of developed embryo) bot

plurannual >>> perennial

plus tree: a tree phenotype judged (but not proved by testing) to be unusually superior in some qualities (e.g., growth rate relative to site, growth habit, high wood quality, resistance to disease and insect attack, or to other adverse local factors) fore

pneumatophore: a specialized root in certain aquatic plants that performs respiratory functions bot

pod: a fruit that dehisces down both sides into two separate valves that are most typically dry and somewhat woody; they are characteristic fruits of the Leguminosae bot >>> legume

pod drop: losses due to the premature drop of pods; phys agr

pod shattering: seed losses due to the premature shattering of pods; for example, in oilseed rape it can be as great as 50 % of the potential yield in some seasons; average losses are around 10-15 %, equivalent to 500 kg/ha or ten times the sowing rate agr

poikiloploid >>> mixoploid

point mutation: a mutation that can be mapped to one specific locus; it is caused by the substitution of one nucleotide for another; it may also be caused by deletion and inversion gene

poison >>> toxicity

poisonous >>> toxicity

POISSON distribution: the basis of a method whereby the distribution of a particular attribute in a population can be calculated from its mean occurrence in a random sample of the population, provided that the population is large and the probability that the attribute will occur is less than 0.1 stat

polar mutation: a mutation of one gene that affects the expression of the adjacent nonmutant gene on one side, but not of that on the other side gene

polar nuclei >>> pole nucleus

polar plate: the functional center for meiotic division of chromosomes; spindle fibers converge on it cyto

polarization: restriction of the orientation of the vibration of electro-magnetic waves of light phy micr >>> polarization microscope

polarization microscope: a compound light microscope used for studying the anisotropic properties of objects and for rendering objects visible because of their optical anisotropy micr >>> polarization

pole: one of the two ends of the cell spindle toward which chromosomes move during mitotic and meiotic anaphase cyto

pole nucleus (pole nuclei pl): the two haploid nuclei present in the center of the embryo sac after division of the megaspore; they may fuse to form a diploid definitive nucleus before fusing with the male gamete to form the triploid primary endosperm nucleus prior to double fertilization bot >>> Figure 25

pollard: a tree cut back almost to the trunk in order to form a thick head of spreading branches, which are cut for basket-making and kindling (e.g., poplars and willows can be pollarded) bot

pollen: collectively, the mass of microspores or pollen grains produced within the anthers of a flowering plant; it is a highly specialized tissue whose function is the production of two sperm cells and their subsequent delivery through the style and ovary to the embryo sac cells where the double fertilization takes place; it is a highly reduced structure consisting of only three cells; the processes of pollen development, germination, and fertilization involve the specific expression of a large number of genes bot >>> Figure 35

pollen analysis: a method to study pollen grains, particularly their size, shape, and surface; since those characters are highly specific for species the method is used for taxonomic classifications bot

pollen barrier: in seed production, the separation of the varieties, lines, etc. (mostly in allogamous crops) in order to prevent intercrossing; it is done by different means, such as strips of other plants (e.g., hemp or maize), which prevent the free flow of pollen, or by isolation walls of tissue seed

pollen contamination: refers often in connection with seed orchards to the phenomenon that some of the pollen fertilizing orchard genotypes origins outside the seed orchard gene >>> alien pollen >>> pollen migration >>> wild pollen >>> gene flow

pollen culture >>> microspore culture

pollen embryoids: embryoids that derive from anther culture biot

pollen grain: a microspore in flowering plants that germinates to form the male gametophyte, a structure made up of the pollen grain plus a pollen tube bot >>> Figure 35 >>> pollen

pollen grain mitosis: in microsporogenesis, a nuclear division that occurs in the pollen grain after the formation of tetrads; it results in a smaller generative nucleus and a larger vegetative nucleus bot

pollen mixing: cross-incompatibility in interspecific crosses is associated with proteins of the pistil that interact with proteins of the pollen to prevent normal pollen tube germination and growth; this unfavorable reaction may be avoided in certain combinations by mixing pollen from a compatible species with pollen from an incompatible parent meth

pollen mother cell (PMC): the microsporocyte, which undergoes two meiotic divisions to produce four microspores; each microspore becomes a pollen grain bot

pollen parent: the parent that furnishes the pollen and that fertilizes the ovules of the other parent in the production of seed meth

pollen sac: a sac within the anther of a stamen within which microspores are produced bot

pollen-shedding: the status or process when the pollen grains are released from the anthers bot

pollen sterility: pollen that is not able to fertilize an egg cell phys

pollen transfer: refers to the kind of pollen transfer from the male to female organs (e.g., mediated by wind, insects, by hand, etc.) bot

pollen tube: the tube formed from a germinating pollen grain and down which the two male gametes pass to the ovum bot >>> Figure 35

pollen tube competition >>> certation

pollinarium (pollinaria pl): a functional unit in orchid pollination that consists of two or more pollinia, stalk, or stipe, and a viscidium bot

pollinate: to transfer pollen from the anther to the receptive surface of the stigma of the same or another flower in angiosperms and from male to female in gymnosperms; this process usually requires a vector in outbreeding plants meth >>> Figure 35

pollination: the transfer of pollen grains from the anther to the stigma of a flowering plant; pollination can also be done in artificial culture (i. e., in vitro pollination) bot >>> Figure 35

pollinator: that parental individual, line, variety, or species, which is used as a donor of pollen in a cross meth

polyacrylamide gel: a gel used to separate biological molecules (proteins); it is prepared by mixing a monomer (acrylamide) with a cross-linking agent (N,N'-methylene-bisacrylamide) in the presence of a polymerizing agent; it leads to the formation of an insoluble three-dimensional network of monomer chains, which become hydrated in water prep

polyacrylamide gel electrophoresis (PAGE): a method for separation of proteins and amino acids on the basis of their molecule size; the molecules move through the gel under the influence of an electric field meth

polyadenylation: posttranscriptional addition of 50-200 adenine residues to the 3' end of eukaryotic mRNA; the poly-A tail can be used to separate eukaryotic mRNA from other RNA species with oligo T cellulose biot

polyandrous: having many stamens bot

polyandry: the state of having more than one male mate at one time; in fertilization, the fusion of one female and two or more male pronuclei within an egg cell bot

polycarpellary: composed of several carpels bot

polycarpic: in general, bearing many fruits (i.e., producing fruit many times or indefinitely); in botany, having a gynoecium forming two or more distinct ovaries or carpels bot

polycarpous >>> polycarpic

polycentric: a chromosome that shows more than two centromeres cyto >>> centromere

polycistronic RNA: mRNA that codes for more than one polypeptide gene

polycotyledonous embryo(s): embryos having more than two cotyledons or seed leaves (e.g., in pines and conifers) bot

polycross: open pollination of a group of genotypes (generally selected) in isolation from other compatible genotypes in such a way as to promote random mating inter se; it is a widely used procedure for intercrossing parents by natural hybridization meth >>> Table 35

polycross test: a progeny test to assess general combining ability from crosses among selected parents; identities can be maintained only for the seed parents; a mixture of pollen is artificially applied to each female parent meth >>> topcross

polyembryonic >>> polyembryony

polyembryony: the condition in which an ovule has more than one embryo like in certain grasses or cereals; in the past, the phenomenon was used for haploid selection among the embryos, which show often different ploidy levels bot meth >>> Figure 17

polyethylene glycol (PEG): a polymeric substance of molecular weight between 1,000-6,000; it is used for stimulation of protoplast fusion chem biot

polygalacturonase-inhibiting proteins (PGIPs): leucine-rich repeat (LRR) proteins involved in plant defence system;  a number of PGIPs have been characterized from dicot species, whereas only a few data are available from monocots phys biot phyt

polygamous: plants that show male, female, and hermaphrodite flowers on the same or different plants bot

polygenes: one of a group of genes that together controls a quantitative character; individually each gene has little effect on the resulting phenotype, which instead requires the interaction of many genes gene >>> Table 33

polygenic: of traits determined by many genes, each having only a slight effect on the expression of the trait gene >>> multifactorial >>> Table 33

polygeny: a trait that is controlled by many genes gene >>> Table 33

polygynoecial: having a number of pistils joined together, as in aggregate fruits (e.g., raspberry) bot

polygyny: the state of having more than one female mate at one time; in fertilization, the fusion of one male and two or more female pronuclei within an egg cell bot

polyhaploid: haploid plant derived from a polyploid individual cyto

polyhybrid: individuals that are heterozygous with respect to the alleles of many gene loci or of crosses involving parents that differ with respect to the alleles of more loci gene

polykaryotic: cells showing many nuclei cyto

polylinker: synthetic oligonucleotide with recognition sites for several restriction endonucleases biot

polymerase: an enzyme that catalyzes the replication and repair of nucleic acids gene

polymerase chain reaction (PCR) technique: a technique for continuous amplification of DNA and/or DNA fragments in vitro; the DNA sequence must be known so that oligonucleotides can be synthesized that are complementary to the extremes of the fragment that is to be amplified; heat stable DNA polymerase (e.g., from Thermus aquaticus) is used for DNA synthesis gene

polymeric genes: genes with equal effects but cumulative action gene

polymery: the production of a trait by cooperation among several polymeric genes gene

polymix breeding: an alternative method to full-sib crossing and testing; the alternative solution is to apply a pollen mix of many male parents rather than a single pollen for each cross; polymix breeding is easy to implement, ensures good estimates of breeding values of the parent being pollinated, and provides for increased genetic gain opportunity because of the significantly increased number of effective parental combinations tested; however, it has found limited use because inbreeding and pedigree control is lost meth stat

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polymorphic: occurring in several different forms bot gene

polymorphism: the existence of two or more forms that are genetically distinct from one another but contained within the same interbreeding population gene

polynemic chromosome: describes metaphase chromosome and/or chromatids with more than two DNA helices cyto

polynucleotide: a sequence of many nucleotides gene

polypeptide: a linear polymer that consists of ten or more amino acids linked by peptide bonds chem

polyphenol oxidase (PPO)it is one of the major enzymes responsible for browning of wheat food products; wheat cultivars differ in PPO activity and plant breeders wish to select germplasm and cultivars with low PPO activities agr phys

polypheny >>> pleiotropy

polyphylesis: originating from several lines of descent bot

polyphyletic: designating a group of species arbitrarily classified together, some of the members of which have distinct evolutionary histories, not being descended from a common ancestor evol

polyploid: an individual carries more than two complete sets of homologous chromosomes cyto

polyploidization: the spontaneous or induced multiplication of a haploid or diploid genome of a cell or individual cyto >>> Table 35

polyploidy: the condition in which an individual possesses one or more sets of homologous chromosomes in excess of the normal two sets found in diploids; it can be produced in nature by somatic doubling due to irregular mitosis in the meristematic cell and by unreduced gametes due to irregular reductional division during meiosis; for example, approximately 70 % of grass species and 20 % of legumes are polyploid cyto >>> Tables 17, 35

polysaccharide: a molecule composed of chains of sugar units phys

polysome: a polyribosome, consisting of two or more ribosomes bound together by their simultaneous translation of a single mRNA molecule gene phys

polysomy: the reduplication of some but not all of the chromosomes of a set beyond the normal diploid number cyto

polyspermy: the entry of more than one sperm cell into an egg cell, irrespective of whether or not the additional sperm cells fertilize bot

polytene chromosome: a chromosome that is formed by repeated reduplication of single chromatids; sections may appear to puff or swell due to differential gene activation; it is visible through the light microscope cyto >>> puff >>> lampbrush chromosome

polyteny >>> polytene chromosome

pomaceous fruit >>> pome

pome: a fruit (e.g., apple, pear, quince) in which the seeds are protected by a tough carpel wall and the entire fruit is embedded in a fleshy receptacle bot

pomology: the science or study of growing fruit hort

population: a community of individuals, which share a common gene pool bot gene; in statistics, a hypothetical (often infinitely large) series of potential observations among which observations actually made constitute a sample stat >>> Figure 38 >>> Table 35

population, closed: a group of interbreeding plants (occurring in a certain area or in an experimental design) or a group of plants originating from one or more common ancestors, where there is no immigration of plants or pollen stat eco

population density: the number of individuals of a population per unit area of a particular habitat bot eco; in biotechnology, the cell number per unit area or volume of a medium biot >>> plant density

population genetics: the study of inherited variation in populations and its modulation in time and space; it relates the heritable changes in populations to the underlying individual processes of inheritance and development gene

population, Mendelian: a group of (potentially) interbreeding plants (cross-fertilizing crops), which may occur in a certain area or in an experimental design gene stat

population size: the number of individuals in a population that are included in reproduction during a certain generation meth stat

population variance: a measure of dispersion defined as the average of the squared deviations between the observed values of the elements of a population and the corresponding mean of those values stat

population waves: irregular or rhythmic changes of the number of individuals in a population that are included in reproduction during certain generations meth stat

porosity: the proportion, as the percentage volume, of the total bulk volume of a body of rock or soil occupied by pore space agr

position (positional) effect: the change in the expression of a gene with respect to neighboring genes gene

positional cloning: a process of molecular cloning of a gene with reference to its position on the genetic or physical map biot

positive screening: a selection technique in which the best individuals in a genetically diverse population are preserved to become the parents, either of the next screening generation, or of new >>> cultivar meth >>> negative screening

postemergence herbicide: a herbicide that affects the weeds after emergence phyt

postgamous incompatibility >>> crossbreeding barrier

postharvest loss(es): crop losses due to parasites that occur after harvest, usually in the store; it can be reduced or prevented by ensuring that the stored product is dry, to prevent moulds developing, and that the product is in an airtight container that lacks oxygen, to prevent various animal pests from eating it agr phyt

poststratification: an estimation method that adjusts the sampling weights so that they sum to specified population totals corresponding to the levels of a particular response variable stat

post-transcriptional gene silencing (PTGS): silencing of an endogenous gene caused by the introduction of a homologous dsRNA, transgene or virus; in PTGS, the transcript of the silenced gene is synthesized but does not accumulate because it is rapidly degraded; this is a more general term than RNAi, since it can be triggered by several different means; it was initially considered a bizarre phenomenon limited to petunias and a few other plant species; in the 1990th, a surprising observation was made in petunias; while trying to deepen the purple color of these flowers, R. JORGENSEN introduced a pigment-producing gene under the control of a powerful promoter; instead of the expected deep purple color, many of the flowers appeared variegated or even white; the observed phenomenon was named "cosuppression", since the expression of both the introduced gene and the homologous endogenous gene was suppressed; meanwhile, it became one of the most important phenomenon in molecular biology; it has become clear that PTGS occurs in both plants and animals and has roles in viral defense and transposon silencing mechanisms; most exciting is the emerging use of PTGS and, in particular, RNA interference (RNAi) - PTGS initiated by the introduction of double-stranded RNA (dsRNA) - as a tool to knock out expression of specific genes biot meth

postzygotic incompatibility: a condition where, in the case of incompatible or wide crosses, the zygote fails to develop, often for nutritional reasons; in some cases embryo culture can be used to rescue the embryo bot

potassium (K): an element that is required for plant growth; deficiency leads to reduced growth and to dark or blue-green coloration in the leaves chem phys

potassium iodide >>> chemical desiccation

pot-bound: used when a plant has an overly extensive root system in a too-small container hort

pot feet: supports placed under pots and planters to raise them off the ground for better drainage and air circulation hort

power (of statistical test): it is the probability that a statistical test will detect a defined pattern in data and declare the extent of the pattern as showing statistical significance stat

PPA: Plant Patent Act; in 1930, the PPA was enacted into law in the United States; the plant patent grants the breeder the exclusive right, for 17 years, to propagate the patented plant by asexual reproduction; the purpose of the PPA was to encourage research investment in asexually reproduced plant species; since 1930, more than 6,000 plant patents have been issued by the Patent and Trademark Office, primarily for fruit trees, flowers, ornamental trees, grape, and other horticultural species

ppm >>> parts per million

PPRP >>> plant pathogenesis-related proteins

preadaptation: an adaptation evolved in one adaptive zone, which proves especially advantageous in an adjacent zone and so allows the organism to radiate into it; in breeding, the pretreatment of plants under moderate climatic (light, temperature, or nutrient) conditions in order to gradually accustom them to stress conditions phys evol


prebasic seed: an OECD class of pedigreed seed which is considered as equivalent to breeder seed and is used for the production of basic seed or foundation seed agr seed >>> breeder(‘s) seed

prebloom: the stage or period immediately preceding blooming agr

prebreeding: all research and screening activities before a plant material enters the directed breeding process (e.g., the development of germplasm to a state where it is viable for breeder’s use); primarily, it involves the evaluation of traits from exotic material and their introduction into more cultivated backgrounds meth

prechilling: the practice of exposing imbibed seeds to cool (+5 to +10°C) temperature conditions for a few days prior to germination at warmer conditions seed >>> stratification

precipitant: a substance or process that causes precipitation chem

precision: the difference between a sample-based estimate and its expected value; it is measured by the sampling error (or standard error) of an estimate stat

precision farming: a farming system which uses global positioning (GPS) technology involving satellites and sensors on the ground and intensive information management tools to understand variations in resource conditions within fields; the information is used to more precisely apply fertilizers and other inputs and to more accurately predict crop yields. Also see global positioning system agr

precision seed: calibrated or pelleted sorts of seeds used for precision drilling agr

precleaning: the process for removing the bulk of foreign materials grossly different in size from the harvested seed or other crop products seed

precocious embryo development: asexual development of the embryo before the flower opens and anthers dehisce bot

predecessor: within the crop rotation, the crop before the recent cropping agr

predisposition: an increase in susceptibility resulting from the influence of environment on the suspect phyt

preferential pairing: chromosome pairing in allopolyploids in which the most structurally similar chromosomes preferentially pair with another cyto >>> Ph locus

prefoliation >>> vernation

preharvest loss(es): crop losses from parasites that occur in the field, as opposed to >>> postharvest losses that occur in the store agr phyt

preharvest sprouting >>> sprouting

premium wheats: wheat grades segregated on the basis of their specific quality characteristics to meet particular market requirements; these may include high or low protein content, combined respectively with hardness or softness of the grain; there will generally also be the specification of certain varieties known to meet or exceed the quality requirements agr

prepotency: the capacity of a parent to impress characteristics on its offspring so they are more alike than usual gene

preselection: selection of some individuals for further tests or studies meth

presoaking: presoaking of seeds in water has been suggested as a means to speed up germination meth

pretest: in order to determine performance prior to the organization or administration of a data collection activity stat

prevalence: the observed frequency of a trait or disease in a population, often at a particular age or time gene

prezygotic incompatibility: in the case of incompatible or wide crosses the inhibition of pollen germination or the prevention of pollen tube growth, among other possible barriers of plant fertilization; in some cases the barrier can be overcome by in vitro pollination bot

pricking off: a method of transplanting tiny seedlings; the blade of a knife or plant marker is used to remove each plant from one spot and move it to another meth hort

pricking out: a method of thinning seedlings by cutting them off at soil level so as not to disturb the roots of the other plants hort meth

pricking-out peg: an adjusted peg used for thinning or transplanting seedlings by cutting them off at soil level meth hort

prickle pollination >>> tripping mechanism

prickly: having thorns bot

primary constriction: the centromeric region of a chromosome cyto

primary culture: a culture resulting from cells, tissues, or organs taken from an organism biot

primary fluorescence: fluorescence originating from the specimen itself micr

primary gene pool: it includes the cultivated species of a crop and related species from which useful genes can be most readily obtained for breeding; in general, it is the total sum of all the genetic variation in the breeding population of a species and closely related species that commonly interbreed with, or can be routinely crossed with, the species evol

primary host >>> host

primary infection: the first infection of a plant by the overwintering or oversummering pathogen phyt

primary inoculum: spores or fragments of a mycelium capable of initiating a disease phyt

primary leaf: one of the first pair of leaves to emerge above the cotyledon during the development of a seedling; it is often morphologically distinct from subsequent leaves bot

primary sex ratio >>> sex ratio

primed in situ labeling: a technique that labels specific sequences in whole chromosomes by in situ DNA chain elongation or >>> PCR meth biot cyto

primer: an oligonucleotide that forms a double strand by using a complementary segment; the primer is prolonged till the double strand is completed biot

priming: the treatment of seeds with an osmotic solution (e.g., polyethylene glycol, which allows controlled hydration); the seed embryo develops to the point of germination and then is dried; it is applied for more uniform and rapid germination of certain vegetable seeds seed

primitive form: in phylogeny, seedless vascular plants with underground rhizomes; they grow in tropical to subtropical areas and are terrestrial or epiphytic; in botany and breeding, as compared to cultivated crops, plants still show wild characteristics, such as brittle rachis, seed shattering, and others bot

primordium (primordia pl): the early cells that serve as the precursors of an organ to which they later give rise by mitotic development bot

principal host >>> host

PRISM: an integrated software solution for plant researchers and agronomists; it provides user-friendly tools to manage experimental data; PRISM consists of several different book types, e.g., an experiment field book; each book type is used to classify information and to execute business rules; many of the book types are configured to produce a spreadsheet-like interface; it can create and print own reports and labels (including barcodes) meth stat


probability sample: a sample selected by a method such that each unit has a fixed and determined probability of selection stat

probe: a radioactively or nonradioactively labeled and defined nucleic acid sequence that can be used in molecular hybridization; usually it is used for ex situ or in situ identification of specific, complementary nucleic acid sequences biot

processing of seeds: the complex of measures in order to clean, calibrate, disinfect, store, and pack seeds seed

prochromosome: a heterochromatin block that is seen during the interphase of cell division and which is related to the number of chromosomes per complement or less cyto

procumbent: trailing or laying flat on the ground bot

proembryo: the young embryo in its early stages of development after zygote formation bot >>> direct embryogenesis

professional plant breeding: there were no professional plant breeders before about 1900; >>> plant breeding was undertaken by farmers and amateurs

progenitor: the original, ancestral, or parental cell, individual, or species bot gene evol

progenitor cell: undifferentiated cell (i.e., immature cell) which will go on to develop into any cell type biot

progeny: offspring; plants grown from the seeds produced by parental plants bot gene >>> Figure 19

progeny selection: selection based on progeny performance meth >>> pedigree breeding

progeny test(ing): a test of the value of a genotype based on the performance of its offspring produced in some definite system of mating meth >>> pedigree breeding >>> Figure 19

prokaryote: the class of organisms that does not have discrete cell nuclei in a nuclear envelope, including bacteria, but shows single, circular DNA molecules within the cytoplasm bio

prokaryotic >>> prokaryote

prolamin: a protein; it is soluble in 70-90 % ethyl alcohol but not in water; it is found only in cereal seeds (e.g., gliadins in wheat and rye, zein in maize); upon hydrolysis they yield proline, glutamic acid, and ammonia chem phys >>> Table 15

proliferation: successive development of new parts, organs, etc. phys

proline (Pro): a heterocyclic, nonpolar imino acid, which is present in all proteins; the major pathway for proline synthesis, which takes place in the cytoplasm, is from glutamate, through gamma-glutamyl phosphate and glutamyl-gamma-semialdehyde, a two-step reaction that is catalyzed by a single enzyme, D1-pyrroline-5-carboxylate synthetase chem phys >>> osmolyte

prometaphase: the stage in mitosis between the dissolution of the nuclear membrane and the organization of the chromosomes on the metaphase plate cyto

promiscuous: heterogeneous or haphazard mixture gene

promiscuous soybean: naturally-nodulating varieties of soybean that fix nitrogen with a wider range of native Rhizobia, and do not require external inoculation agr

promoter: a nucleotide sequence within an operon, lying between the operator and the structural gene or genes, that serves as a recognition site and point of attachment for the RNA polymerase; it is the starting point for transcription of the structural gene(s) in the operon, but is not itself transcribed; the promoter controls where (e.g., which portion of a plant) and when (e.g., which stage in the lifetime) the gene is expressed; for example, the promoter Bce4 is seed-specific gene biot >>> cauliflower mosaic virus (CaMV)

promoter sequence >>> promoter

propagate: to reproduce or cause to multiply or breed agr

propagating bench: a stationary, shallow box (sometimes covered by a glass pan or other means); it is usually filled with fine sand or certain soil (often sterilized), which is kept moist; cuttings, slips, or shoots after in vitro culture are inserted into the growing medium until they form roots meth hort

propagating case >>> propagating bench

propagation: various methods by which plants are increased (e.g., seeds, division, separation, softwood cuttings, slips, grafting, budding, or layering) meth hort agr

propagule: any type of plant to be used for reproduction (e.g., seedling, a rooted or unrooted cutting, a graft, a tissue-cultured plantlet, etc.) meth hort

proper block design: a >>> block design is proper if all blocks have the same cardinality, i.e., contain the same number of plots; for binary designs, this just means that all blocks contain the same number of points stat

prophage: the noninfectious form of a temperate bacteriophage in which the phage DNA has become incorporated into the lysogenic, host bacterial DNA biot

prophase: the first phase of mitosis and meiosis cyto

prophyll(um): the first leaf or protective scale of a lateral shoot bot

proplastid: a colorless, double-membrane-bound organelle with little internal structure that acts as a precursor in the development of all plastids bot

protandry: the maturation of anthers before carpels (e.g., in sugarbeet, sunflower, or carrot) bot >>> Table 18

protease: an enzyme that catalyzes the hydrolysis of the peptide bonds of proteins and peptides chem phys >>> proteinase

protected variety: a variety that is released and granted a certificate of plant variety protection under the legal statutes of a given country; the owner of a protected variety has the right of selling, offering, reproduction, import, export, or using for hybrid seed production seed

protein: a polymer that has a high relative molecular mass of amino acids; it has many functions in the living cell chem phys >>> Tables 15, 16, 33, 48

protein engineering: production of altered proteins by site-directed mutagenesis biot >>> biotechnology

proteinase: an enzyme that hydrolyzes protein molecules chem phys

proteome: the complete set of proteins detectable in a tissue phys

proteome analysis: the basis of proteome analysis is an electrophoretic separation of the proteins on a two-dimensional protein gel, silver staining of proteins, followed by an image analysis of the stained gel; interesting protein spots identified on the gel can be excised; the critical protein can be extracted from the excised spot and further analysis of the protein (amino acid composition, partial amino acid sequence, isoelectric point, molecular weight) may result in protein identification meth phys biot

proteomics:  systematic characterization of proteins, which are found in a tissue or in a specific physiological condition; the proteins can be identified using mass spectroscopy

protoclonal variation: variability of somatic cells derived from protoplast culture biot

protoclone: a plant regenerated from a protoplast culture biot

protogyny: a condition in which the female parts develop first (e.g., in rapeseed) bot >>> Table 18

protoplasm: a complex, translucent, colorless, colloidal substance within each cell, including the cell membrane, but excluding the large vacuoles, masses of secretions, ingested material, etc. gene

protoplast: that part of a cell that is actively engaged in metabolic processes or a cell without a cell wall; protoplasts are produced by enzymes, which digest the wall; they are used for production of hybrid cells by protoplast fusion or for injection of foreign DNA bot biot

protoplast culture: the isolation and culture of plant protoplasts by mechanical means or by enzymatic digestion of plant tissue, organs, or cultures derived from these; protoplasts are utilized for selection or hybridization at the cellular level and for a variety of other purposes biot

protoplast fusion: a technique used in somatic hybridization experiments; it is used for overcoming crossing barriers; protoplasts are placed together and induced to fuse, applying fusogenic agents, such as polyethylene glycol or physical means; subsequent regeneration of the cell wall allows the propagation and regeneration of a somatic hybrid plant biot

prototroph: a strain of organisms capable of growth on a defined minimal medium from which they can synthesize all of the more complex biological molecules they require, as opposed auxotroph phys

provenance: the geographical source and/or place of origin of a given lot of seed, propagules, or pollen fore

provenance test: an experiment, usually replicated, comparing trees grown from seed or cuttings that were collected from many geographical regions of a species distribution fore

proximal: toward or nearer to the place of attachment cyto >>> centromere >>> chromosome arm

prune >>> pruning

pruning: trimming branches or parts of trees and shrubs in order to trim a plant or to bring the plant into a desired shape; in addition, the removal of the growing point from a plant frequently causes the initiation of tillering or branching; the onset of flowering on the new vegetative growth may be delayed compared with that of unpruned plants; the method may be also used for synchronization of flowering prior to hybridization; branches on trees strive in an upward direction; the internal struggle is all about reaching up for the light; the result can be branches that are so intertwined that they themselves create shade for each other; that affects the formation of flower buds and, thereby, fruits; the best shape a fruit tree can have is one central trunk, with branches that grow as close to a right angle as possible and that are at the most half as thick as the trunk; the tree is usually pruned to help it achieve this shape; however, once a branch is cut off, it does not bear fruit; if the branch is cracked, it still hangs on and it will try and save the situation by forming more flowers and, thereby more fruits; e. g., in pear trees where the crack-method gave an up to 50 % higher yield, but the method can also be used on apple, cherry and plum trees; the branch is cracked relatively close to the trunk; on plum trees, where the branches are more brittle, one can twist the branch instead of snapping it, the cracking should be done in the early spring when the sap in tree is rising; the wound will heal quickly and there is no entry for fungal diseases; besides resulting in a greater yield, the cracked branches also provide for more comfortable fruit-picking hort meth

pseudoallele: genes that behave as alleles in the allelism test but that can be separated by crossing-over gene

pseudoallelism >>> pseudoallele

pseudobivalent: a bivalent-like association of two mitotic chromosomes due to reciprocal chromatid exchange cyto

pseudocarp: a fruit consisting of one or more ripened ovules attached or fused to modified bracts or other nonfloral structures bot

pseudocereals: the grain amaranths, mainly quinoa (Chenopodium quinoa), and buckwheat (Fagopyrum spp.), are cereal-like grains that are not of grass origin agr

pseudocompatibility: the occurrence of fertilization that normally is prevented by incompatibility mechanisms; it is caused by specific environmental or genotypic conditions; for example, in rye, by high temperature (about +30°C) self-incompatibility can be broken so that seeds are set bot

pseudodominance: the apparent dominance of a recessive gene (allele), owing to a deletion of the corresponding gene in the homologous chromosome gene

pseudodominant >>> pseudodominance

pseudofertility >>> pseudocompatibility

pseudogamous heterosis: increased vigor of maternal offspring due to male parent influence on the endosperm bot gene

pseudogamy: a type of apomixis in which the diploid egg cell develops into the embryo without fertilization of the egg cell, although only after fertilization of the polar nuclei with one of the sperm cells from the male gamete to form a normal triploid endosperm bot

pseudogene: genes that have been switched off in evolution and no longer have any function; they are entirely neutral and evolve at a constant rate gene

pseudoheterosis: luxuriance; it designates hybrids between species, varieties, or lines that exceed the parents in some traits, however, neither by sheltering deleterious genes nor by balanced gene combinations gene >>> heterosis

pseudoisochromosome: a chromosome that shows only equal ends as a result of interchanges cyto

pseudostem: a false stem; for example, bananas have pseudostems which look like tree trunks but are no; each banana stem consists of layers of leaf sheaths, with the flower peduncle growing up through the centre and emerging at the centre of the crown bot

pseudovivipary: vegetative proliferation of plantlets in the inflorescence axes bot

Pto: a specific  resistance gene  in tomato, which controls resistance against the bacterium Pseudomonas syringae pv. tomato; the gene encodes a cytosolic protein kinase; the Pto system remains the best characterised specific resistance gene system phyt

pubescent: covered with soft hairs, downy bot

pUC18 vector: a plasmid cloning vector; size: 2.7 kb; about 100 copies per chromosome; it shows ampicillin resistance for selection and alpha complementing fragment of beta-galactosidase with in-frame polylinker for cloning biot

puff: a structural modified region of a polytene chromosome; it originates from the despiralization of deoxyribonucleoprotein cyto >>> polytene chromosome >>> lampbrush chromosome

puffing >>> puff

pulp: the soft, succulent part of a fruit, usually composed of mesocarp and/or the pith of a stem bot

pulse: the edible seeds of any leguminous crop bot >>> legume(s)

pulsed-field gel electrophoresis: an electrophoretic technique in which the gel is subjected to electrical fields alternating between different angles, allowing very large DNA fragments to move through the gel, and hence permitting efficient separation of mixtures of such large fragments meth biot

PUNNETT square: a diagrammatic representation of a particular cross used to predict the progeny of the cross; a grid is used as a graphic representation of the progeny zygotes resulting from different gamete fusions in a specific cross meth

pure bred: derived from a line subjected to inbreeding gene

pure line: a number of individuals of a successive, self-pollinated crop, which derives from a single plant; a strain homozygous at all loci gene meth

pure line breeding >>> true breeding

pure-live seed: the percentage of the content of a seed lot that is pure and viable; it is determined by multiplying the percentage of pure seed by the percentage of viable seed (germination percentage) and dividing by 100 seed

purity testing: determination of the degree of contamination of seed lots with genetically nonidentical, damaged, or pest-infected seeds seed

puroindoline protein(s): small, basic, cysteine-rich proteins found in bread wheat (Triticum aestivum); the wheat puroindoline genes affect wheat milling and baking quality through their effects upon grain hardness; puroindoline a and b together comprise the wheat hardness locus and control whether wheat is soft or hard textured, and they represent the grain hardness gene on chromosome 5DS; in hexaploid wheat, soft kernel texture is the wild type, whereas hard texture (hardness) results from any one of several mutations in the puroindolines;mutations in either puroindoline result in hard texture;  puroindoline a and b interact to create grain softness by binding cooperatively to starchgranules;  by engineered introduction of a puroindoline gene the hard textured grain of durum wheat (Triticum durum) and other cereals, including maize and barley, can be converted into soft texture (MORRIS and GEROUX, 2000) phys gene >>>


pustule: a blisterlike spot or spore mass developing below the epidermis, which usually breaks through at maturity phyt

P value: probability value; a decimal fraction showing, e.g., the number of times an event will occur in a given number of trials stat

PVPA >>> Plant Variety Protection Act

pycnidium (pycnidia pl): a flask-shaped fungal receptacle bearing asexual spores (i.e., pycniospores) bot

pycniospore: a spore from a pycnidium bot phyt

pycnotic: the concentration of the nucleus into a compact, strongly stained mass, taking place as the cell dies cyto

pyrenoid: it refers to a proteinaceous region of chloroplast, sometimes the site of accumulation of carbohydrate reserves bot phys

pyriform: pear-shaped bot

pyrimidine: a basic, six-membered heterocyclic compound; the principal pyrimidines uracil, thymine, and cytosine are important constituents of nucleic acids chem phys

© by R. Schlegel 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019