PenetranceThe proportion of individuals in a population that express the phenotype expected from their genotype with respect to a specific gene.
peptidaseAn enzyme that catalyzes the hydrolysis of a peptide bond.
peptideAny compound consisting of two or more amino acids, the building blocks of proteins.
peptide bondThe chemical bond holding amino acid residues together in peptides and proteins.
peptide expression libraryA collection of peptide molecules, produced by recombinant cells, in which the amino acid sequences are varied.
peptide nucleic acid(Abbreviation: PNA). A synthetic oligonucleotide analogue, in which the sugar backbone is replaced by a peptide chain, upon which the nucleoside residues…
peptide vaccineA short chain of amino acids that can induce antibodies against a specific infectious agent.
peptidyl transferaseAn enzyme bound tightly to the large sub-unit of the ribosome, that catalyses the formation of peptide bonds between amino acids during translation.
peptidyl-tRNA binding site(Abbreviation: P-site). The site on a ribosome that hosts the tRNA to which the next amino acid for the growing polypeptide chain is attached.
perennialA plant that flowers continuously for several years.
pericentric inversionA chromosomal rearrangement in which a segment of chromosome, including the centromere, is rotated.
periclinalThe orientation of cell wall or plane of cell division parallel to the reference surface.
periclinal chimera1. Genotypically or cytoplasmically different tissues arranged in concentric layers. 2.
pericycleRegion of the plant bounded externally by the endodermis and internally by the phloem. Most roots originate from the pericycle.
periplasmThe space between the cell (cytoplasmic) membrane of a bacterium or fungus and the outer membrane or cell wall. Synonym: periplasmic space.
permanent wilting point(Abbreviation: PWP). The moisture content of a soil below which plants wilt to such an extent that they fail to recover even when fully watered.
PermeableReferring to a membrane, cell or cell system through which small molecules can diffuse.
persistenceAbility of an organism to remain in a particular setting for a period of time after it is introduced.
PersistentChemicals with a long inactivation or degradation time, such as some pesticides.
PERVAbbreviation for porcine endogenous retrovirus.
Pesticide(PES-tih-side) Any substance that is used to kill insects and other pests.
Pesticide resistanceA genetic change in response to selection by a pesticide, resulting in the development of strains capable of surviving a dose lethal to most individuals…
petalOne of the parts of the flower that make up the corolla.
Petri dishFlat round glass or plastic dish with a matching lid, used for small-scale culturing of organisms, germinating seeds etc.
PFGEAbbreviation for pulsed-field gel electrophoresis.
PGOne of several hormone-like substances made by the body. Different PGs control blood pressure, contraction of smooth muscles, and other processes within…
pHA measurement for liquids to determine acidity or alkalinity. On a scale of one to 14, seven is considered neutral.
pH-electrode-based sensorSensor in which a standard pH electrode is coated with a biological material. Many biological processes raise or lower pH, and the changes can be detected…
phagemidsCloning vectors that contain components derived from both phage and plasmid DNA.
phagocytesImmune system cells that ingest and destroy viruses, bacteria, fungi and other foreign substances or cells.
phagocytosis(FA-goh-sy-TOH-sis) The process by which a phagocyte (a type of white blood cell) surrounds and destroys foreign substances (such as bacteria) and removes…
pharmacokinetics(FAR-muh-koh-kih-NEH-tix) The activity of drugs in the body over a period of time, including the processes by which drugs are absorbed, distributed in the…
Phase ChangeA method of storing information on rewritable optical discs.
phase stateThe coupling or repulsion of two linked genes.
PhenocopyAn environmentally induced, non hereditary variation in an organism, resembling a genetically determined trait.
phenolic oxidationCommon aspect of the wound response in plants. Phenolic oxidation is often indicated by blackening of tissue and it may be a precursor to growth…
phenolicsCompounds with hydroxyl group(s) attached to the benzene ring, forming esters, ethers and salts.
PhenotypeThe observable characteristics of an organism, the expression of gene alleles (genotype) as an observable physical or biochemical trait. See Genotype.
PheromoneA hormone-like substance that is secreted into the environment.
phloemSpecialized vascular plant tissue for the transport of assimilates (generally sugars) from the point of synthesis (in the leaf) to other parts of the…
PhosphataseAn enzyme that hydrolyzes esters of phosphoric acid, removing a phosphate group.
photosynthetic photon flux(Abbreviation: PPF). A measure of the intensity of light utilized by plants for photosynthetic activity.
photosynthetically active radiation(Abbreviation: PAR). The part of the radiant energy that is capturable by natural photosynthetic systems (approximately equivalent to the natural light…
phototropismThe tendency of plants to direct shoot growth towards the source of light.
phylogenyThe deduced evolutionary history of related organisms.
Physical mapA map showing physical locations on a DNA molecule, such as restriction sites, and sequence-tagged sites. (See Mapping.)
phytochemical(FY-toh-KEH-mih-kuhl) A substance found in plants. Some phytochemicals may reduce the risk of cancer.
phytochromeA pigment, found in the cytoplasm of green plants, which can exist in two forms Pr (biologically inactive) and Pfr (biologically active).
phytohormoneA substance that stimulates growth or other processes in plants. Major species are auxin s, abscisic acid, cytokinin s, gibberellin s and ethylene.
phytoremediationThe use of plants actively to remove contaminants or pollutants from either soils (e.g. polluted fields) or water resources (e.g. polluted lakes).
phytostatApparatus designed for the semi-continuous chemostatic culture of plant cells.
phytosterolA plant-based compound that can compete with dietary cholesterol to be absorbed by the intestines, resulting in lower blood cholesterol levels.
pigmentA substance that gives color to tissue. Pigments are responsible for the color of skin, eyes, and hair.
pinocytosisThe engulfing of a minute droplet of liquid by a living cell.
pipetteWidely used device for accurate dispensing of small volumes of liquids.
pistilCentral organ of the flower, typically consisting of ovary, style and stigma. Usually referred to as the female part of a perfect flower.
plant breeders' rights(Abbreviation: PBR). Legal protection of a new plant variety granted to the breeder or his successor in title.
plant cell immobilizationEntrapment of plant cells in gel matrices so that they are protected from physical damage.
plant genetic resources(Abbreviation: PGR). The reproductive or vegetative propagating material of: 1.
plant growth regulatorAn organic compound, either natural or synthetic, and other than a nutrient, that modifies or controls one or more specific physiological processes within…
Plant-incorporated protectantsFormerly referred to as plant-pesticides, plant-incorporated protectants (PIPs) are substances that act like pesticides produced and used by a plant to…
plantibodyAn antibody expressed transgenically in an engineered plant.
plantletA small rooted shoot regenerated from cell culture following embryogenesis or organogenesis.
plaqueA film of mucus that traps bacteria on the surface of the teeth. Plaque can be removed with daily brushing and flossing of teeth.
Plasma(PLAZ-muh) The clear, yellowish, fluid part of the blood that carries the blood cells. The proteins that form blood clots are in plasma.
plasma cellsAntibody-producing white blood cells derived from B lymphocyte s.