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P
Number of searching adult parasites.

Paddy
The rice kernel with the husk on, sometimes referred to as rough rice.

Paint gun
Type of small, hand-carried air-blast nozzle for pesticide application.

Pair-bonding
A reciprocal 'mutual attachment' between two heterosexual, sexually mature, organisms such that aggressive tendencies are largely suppressed and sexual ones enhanced.

Paired-difference test
A test to compare two populations by using pairs of elements, one from each population, that are matched and hence nearly alike. Thus, the test involves two samples of equal size, where the members of one sample can be paired against members of the others. Comparisons are made within the relatively homogeneous pairs (blocks).

Palatable
Good to the taste, not necessarily healthful. Some poisonous plants that livestock usually avoid are made more palatable by treatment with certain chemicals and may cause injury to the animal.

Palea
In grasses the upper bract that with the lemma encloses the flower.

Palindrome
A nucleotide sequence on a DNA molecule in which the same sequence is found on each strand, but in the opposite direction, leading to the formation of a repetitious inversion.

Palisade cells
A layer of elongated cells, rich in chloroplasts, lying below the epidermis and perpendicular to the plane of a leaf.

Palisade parenchyma
Elongated cells found just beneath the upper epidermis of leaves and containing chloroplasts.

Palmate (leaves)
Radiantly lobed from a common point.

Palpation
The application of the fingers with light pressure to the surface of the body for the purpose of determining the consistency of the parts beneath.

PAN (Peroxacyl nitrates)
Air pollutants produced as by-products in the exhausts of internal combustion engines and injurious to plants.

Pandemic
A world-wide epidemic.

Panel consensus method
A method for forecasting in the absence of appropriate data where experts within the organisation derive a forecast from a consensus of the opinions of experts.

Panicle
A spreading type of inflorescence with stalked flowers e.g. oats and fescues.

Pansporoblast
Myxosporidean sporoblast that gives rise to more than one spore; also called a sporoblast mother cell.

Pantropic
Having an affinity for many tissues. A micro-organism that can attack more than one tissue of the body.

Pantropical
A species occurring widely throughout the tropical and subtropical parts of the world.

Panzootic
Denoting a disease affecting all, or a large proportion of the animals or a region; extensively epizootic.

Papatasi fever
Virus disease transmitted by sand flies; also called sand fly fever.

Papilionaceous
Butterfly-shaped. A term referring to flowers of legumes.

Papillate
Bearing a papillae, i.e. a hump or swelling.

Papular (skin lesion)
Pertaining to a papule or pimple.

Papule
A small hard-pointed swelling on the skin, usually inflammatory, but not suppurating.

Parabasal body
Golgi body located near the basal body of some flagellate protozoa, from which the parabasal filament runs to the basal body.

Parabasal filament
Fibril with periodicity visible in electron micro-graphs, that courses between the parabasal body and a kinetosome.

Paralysis, acute
A fatal disease of adult honey bees and of certain bumble-bees, caused by a virus.

Paralysis, bacillary
A disease of silkworm larvae caused by ingestion of spores and parasporal crystals of Bacillus thuringiensis.

Paralysis, chronic
A fatal disease of adult honey bees and of certain bumble-bees, caused by a virus of a different shape and size to that causing acute paralysis in bees.

Paramere
Copulatory appendage in male cimicid bugs.

Parameter
A numerical descriptive measure used in statistics, economics and modelling where it refers to a variable. Coefficients that control model process rates but do not change in the run of a model.

Parametric budget
A planning technique which takes varying prices and yields into account.

Parametric hypothesis
A statistical hypothesis about a population parameter.

Paraphyses
Sterile filaments or cells found in the fruiting bodies of some fungi.

Paraplegia
Paralysis of the hind legs and posterior part of the body.

Parapolar cells
Cells making up the ciliated somatoderm immediately behind the calotte of a mesozoan.

Parasexual cycle
A mechanism whereby recombination of hereditary properties is based on mitosis rather than meiosis.

Parasexualism
A mechanism whereby recombination of hereditary properties is based on mitosis.

Parasite
Organism or virus existing in intimate association with living organism from which it derives material essential for its existence while conferring no benefit in return (Marsh, 1969). An organism that lives at the host's expense, obtaining nutriment from the living substance of the latter, depriving it of useful substance, or exerting other harmful influence upon it (Cantwell, 1974). Any organism that lives in or one the body of another living organism and obtains nourishment from it (Pyenson, 1951). A plant or animal living on or in another plant or animal, which is called its host. The host continues, for some time at least, to live and feed its parasite (contrast predator) but may eventually be killed by it. A parasite of one host may itself be a host to another parasite, so the terms are relative. A crop-eating insect could be called a parasite or a herbivore, but is not usually so-called. It is usually simply called a pest, which may be subject to parasites, themselves perhaps subject to 'hyper-parasites'. A fungus living on the crop is always called a parasite (Hartley & West, 1966). An organism living in intimate association with a living organism (plant or animal) from which it derives material essential for its existence while conferring no benefit in return (Hill, 1983).

Parasitic castration
Condition in which a parasite causes retardation in development or atrophy of host gonads, often accompanied by failure of secondary sexual characteristics to develop.

Parasitism
Symbiosis in which the symbiont benefits from the association, whereas the host is harmed in some way.

Parasitoid
An organism that has a parasitic stage that feeds in or on another organism eventually destroying it, most parasitic Hymenoptera and Diptera fall into this category as usually only the larvae are parasitic.

Parasporal body
A particle in some bacteria which lies alongside the spore or is included in the sporangium along with the spore, formed during sporulation e.g. Bacillus species; if the inclusion is a crystalloid, the species is called crystalliferous.

Parasitophorous vacuole
Vacuole within a host cell that contains a parasite.

Paratenic host
Host in which a parasite survives without undergoing further development; also known as a transport host.

Paratope
The site within an immunoglobuline Fab that specifically interacts with an antigenic determinant (epitope) (King & Stansfield, 1990).

Parboiling
Hydrothermal treatment of paddy before milling. Includes soaking, treating with heat and re-drying.

Parenchyma
The plant tissue consisting of cells concerned with physiological activities i.e. capable of photosynthesis or storage, as distinguished from supportive tissue.

Parenterally
Referring to injections, given by subcutaneous intravenous or intra-muscular route, as distinct from administration by mouth.

Paresis
Paralysis which is partial only. Slight paralysis.

Pareto chart
A bar chart used in quality control to separate the important problem areas from the less important ones. The bars are drawn in order of decreasing height, from left to right.

Parial population curve
The population density of a given developmental stage plotted against time.

Parotid (lymph node)
A lymph node situated on the posterior surface of the masseter muscle, in cattle 4 or 5 cm below and forward of the base of the ear, and just under the skin. It drains the head.

Parr
The young of salmonid fish.

Pars prostatica
Dilation of the ejaculatory duct of a flatworm, surrounded by unicellular prostate cells.

Parthenocarpy
The development of the fleshy part of a fruit without fertilisation of the contained seed.

Parthenogenesis
Reproduction without fertilisation; usually through eggs but sometimes through viviparity e.g. aphids.

Partial budget
A budget which shows the expected extra expenses and extra returns for a change contemplated in the farm programme.

Partition coefficient
A constant ration that occurs when a heterogeneous system of two phases is in equilibrium; the ratio of concentrations (or strictly activities) of the same molecular species in the two phases is constant at constant temperature.

Partial correlation
A measure of the strength of the linear relationship between two variables after adjusting for any linear relationship the two variables have with a third (possibly more) variable.

Parthenocarpic
The production of fruit without pollination.

Particle size, Average
In terms of; arithmetical mean diameter, diameter of particle of average surface area, or of average volume

Parts per million
Proportion of toxicant present in relation to that of plant material on which it has been deposited. (Usually applied in connection with edible portion of crops).

Parturient
Referring to birth. Connected with the act of parturition.

Paruterine organ
Fibromusclar organ in some cestode that replaces the uterus.

Pasern
Birds belonging to the order Paseriformes, the perching birds; includes all songbirds.

Passive immunisation
Immune state in an animal created by inoculation with serum (containing antibody) or lymphocytes from an immune animal, rather than by exposure to the antigen.

Passive immunity
Immunity resulting from transfer of antibodies from an immune to a non-immune individual.

Passive resistance
Innate resistance which does not entail any defensive reactions of the host to the presence of the pathogen.

Paste
Water-based film-forming composition.

Pastern
The portion of a horse's foot between the fetlock and hoof.

Pasteur effect
The phenomenon in respiration in which, in the presence of oxygen, fermentation is suppressed.

Pasteurisation
A process using mild heat to reduce the microbial level in heat-sensitive materials.

Pasture
A crop harvested by the grazing of livestock.

Patchiness
The spatial process of the clumping of organisms. It has been observed in many biota; e.g. fish schools and willow thickets.

Pathodeme
A host population in which all individuals have a given resistance in common.

Pathogen
A specific cause of disease. A micro-organism capable of producing disease under normal conditions of host resistance and rarely living in close association with the host without producing disease; any micro-organism, virus, substance, or factor causing disease (Cantwell, 1974). A micro-organism (microbe) that lives and feeds (parasitically) on or in a larger, host organism and thereby injures it (van den Bosch, 1980).

Pathogenesis
The causing of a state of ill health, morbidity and in some cases premature death, in a host organism by a pathogenic micro-organism. That portion of the life cycle of a pathogen during which it becomes and continues to be associated with its suscept.

Pathogenicity
Ability of a pathogen to produce disease, i.e. to be pathogenic.

Pathognomonic
A pathognomonic symptom (or diagnostic symptom) is a specifici characteristic or state that clearly indicates a particular disease or malfunction.

Pathology
The science that deals with all aspects of disease.

Pathological
Pertaining to disease; pathological tissue or pathological samples are those derived from a diseased individual.

Pathosystem
An ecological sub-system defined by the phenomenon of parasitism. A plant pathosystem may include one or more host plant species along with the various parasites - insects, fungi, bacteria etc. - that utilise the hosts. Herbivorous birds and mammals, however, are generally not classified as parasites.

Pathotoxin
A toxin produced by a pathogenic organism and capable of simulating the disease.

Pathotype (pathovar)
A parasite population in which all individuals have a given parasitic ability in common i.e. they are distinguished by common characters of pathogenicity, particularly in relation to host range.

Payback period
The number of years taken to recoup the original investment.

Payoff table
In a decision analysis a two-way table displaying the payoffs, either opportunity losses or profits, for selecting a particular action given that a specific state of affairs is in effect.

Payment by result
A range of incentive payment schemes that are directly linked to levels of output.

Payment in kind
Non-cash payment (e.g. food) for a service received (e.g. labour).

Peat
A soil type; partly decomposed organic matter that has accumulated under excessive moisture.

Pebrine
A disease of the silkworm, Bombyx mori, caused by the micro-sporidian Nosema bombycis.

Pectin
A methylated polymer of galacturonic acid found in the middle lamella and the primary cell wall.

Pectinase
An enzyme that breaks down pectin.

Pedalfer
The soil of a humid region in which iron and aluminium have leached into the B horizon, but which has no carbohydrate zone.

Pedicel
Slender, second abdominal segment that forms a 'waist' in most Hymenoptera.

Pedicellate
Fungi having a slender stalk or peduncle that supports a larger fruiting or spore-bearing organ.

Pedipalps
Second pair of appendages in chelicerate arthropods, modified variously in different groups.

Pedocal
A soil of a semi-arid or arid region, having a distinct carbonate zone.

Pedology
Science that treats of soil.

Peduncle
See pedicellate. A stem; usually the stem or stalk connecting a body with an outgrowth.

Peer review
Usually a technical review of R & D work, conducted by people who are of similar technical calibre and level of authority as the person responsible for the work.

Pellet
Seed coated with inert material, often incorporating pesticides, to ensure uniform size and shape for precision drilling.

Pelleting
Coating of seed with inert material, often incorporating pesticides, to ensure uniform size or shape, and increase the amount of active ingredients that can be applied.

Penetrant
An additive or adjuvant added to a spray to enable it to penetrate the waxy insect cuticle or the outer surface of plant tissues more effectively.

Penetration
The initial invasion of a host by a pathogen.

Penetration pricing
An approach to pricing new products which involves setting an initially low price.

Penicillin
A broad-spectrum antibiotic produced by the mould Penicillium chrysogenum, which inhibits the formation of the bacterial cell wall.

Pentose pathway
Oxidation of glucose by elimination of one carbon atom as CO2 and formation of five-carbon sugars.

Peptide
Two or more amino acids bonded together by peptide bonds between amino (-NH2) and carboxyl (-COOH) groups.

Peptidoglycan
The rigid layer of bacterial cell walls, composed of alternating sugar units, N-acetyl glucosamine and muramic acid, cross-linked by short peptides.

Percentiles
The set of values that divide the total frequency of a set of data into 100 equal parts. The 100 pth percentile is a value such that at most 100p% of the measurements are less than the value and at most 100(1 - p)% are greater.

Percussion
The act of striking a part of the body with short sharp blows as an aid in diagnosing the condition of the parts beneath by the sound obtained.

Perennial
A plant that lives longer than 2 years from time of seeding, and usually flower each year. Plants may be herbaceous or woody.

Perennial mycelium
A mycelium which persists in a host plant from one season to the next.

Perfect competition
A market structure in which there are a large number of small firms producing identical products and where there is free entry to the industry.

Perfect flower
One that has both pistils and stamens.

Perfect reproduction
Reproducing with sexual processes.

Perfect stage
The sexual stage (e.g. fruiting bodies) in the life cycle of a fungus. The state of a life-cycle in which spores (such as ascospores and basidiospores) are formed after nuclear fusion or by parthenogenesis.

Perfect state
Stage in the life-cycle of a fungus characterised by sexual spores.

Performance review
A personnel evaluation method usually linked to a salary review procedure. The employee's performance is assessed against pre-determined tasks and objectives.

Pericardial (sac)
The membranous sac in which the heart is contained. The cavity between heart and pericardium contains a clear straw-coloured fluid when normal.

Pericarp
Matured or ripened walls of the ovary when it becomes a fruit.

Pericycle
Tissue generally found in the root and bound externally by the endodermis and internally by the phloem.

Periderm
The outer corky layer of a plant stem.

Peridermium
An aecium, of the sort found in Cronartium, Melampsora, and Coleosporium, with a peridium that extends prominently beyond the chains of aeciospores.

Peridium
A membrane of sterile cells that forms around the aecia produced in aecidia or in peridermia or roestelia. The external covering of certain fruiting bodies of some fungi.

Perikaryon
Portion of the cell that contains the nucleus (karyon), sometimes called the cyton or cell body, used in reference to cells that have processes extending some distance away from the area of the nucleus, e.g. nerve axons or tegumental cells of cestodes and trematodes.

Perineum
The area surrounding the anus.

Period
One of the important designations of time - a segment of the time beam with a finite length; the interval of time required for a periodic motion of phenomenon to complete a cycle and being to repeat itself; a chronological division as of a course, a development, a life; as the sporulation period.

Period of a cyclic or seasonal effect
The number of time points between identifiable points of recurrence - between peaks and valleys - in a time series. The number of time points for one complete cycle or for a complete seasonal pattern to be exhibited.

Periodic colonisation
The frequent release of natural enemies for short-term pest control rather than permanent establishment (see augmentation).

Periople
The smooth shiny layer on the outer surface of the hoof.

Periplasmic space
The area between the plasma membrane and the cell wall, containing certain enzymes involved in nutrition.

Perithecium
A flask-shaped structure containing the asci and ascospores produced by some ascomycete fungi during the sexual stage of their life cycle.

Peritoneal (fluid)
Pertaining to the peritoneum, the smooth serous lining of the abdominal cavity, covering the inside of the wall of the abdomen and reflected over the abdominal viscera. The cavity contained by the peritoneum is filled with a straw-coloured fluid when normal.

Peritrichous
Having a number of flagellae over the surface of a bacterium.

Peritrichous flagellation
Having flagella attached to many places on the cell surface.

Peritreme
Elongated sclerite extending forward from the stigma of certain mites, mainly in the suborder Mesostigmata.

Peritrohic membrane
Non-cellular, delicate membrane lining an insect's midgut.

Permanent parasite
Parasite that lives its entire adult life within or on a host.

Permanent pasture
One that is used in indefinitely for grazing for livestock.

Permeability
As used in insect toxicology refers to the ability of chemicals to penetrate the insect cuticle.

Permutation
An ordered arrangement of r distinct objects. The number of n objects selected in groups of size r is denoted by Pnr, where Pnr = n(n - 1)(n - 2) ...(N - r + 1)

Permuted sequence
The termini of DNA sequences on different viral particles of the same virus which are non-identical but overlapping.

Peroral
By way or through the mouth; per os.

Peroxisome
A cytoplasmic organelle within which photo-respiration occurs in animal and plant cells, characterised by its content of catalase and other (peroxidase) oxidative enzymes.

Persistence
The relative term applied to chemicals or microbial insecticides that remain active for a long period of time after application. With chemicals, persistence is due to low volatility and chemical stability. Certain organochlorine insecticides are highly persistent. With reference to a disease agent, one that remains in a virulent state in the vector's system for more than 100 hs or the lifetime of the vector.

Persistent herbicide
Herbicide that, when applied at the recommended rate, will harm susceptible crops planted in normal rotation after harvesting the treated crop, or that interferes with re-growth of native vegetation in non-crop sites for an extended period of time.

Persistent transmission
A type of insect transmission in which the virus is acquired by the vector only after a long acquisition feeding period, and in which there may be a latent period following the acquisition feed, before the vector can transmit the virus. The vector remains viruliferous for a long period, often throughout its life span. The virus sometimes multiplies within the vector.

Persistent virus
One which is retained for long periods, and sometimes through life, by vectors transferred from infected to healthy plants.

Person differential interaction
A mathematical technique for demonstrating the existence of a gene-for-gene relationship between host and pest.

PERT
Programme Evaluation and Review Technique is the name given to a network approach to planning, monitoring, controlling and evaluation. Designed for particularly complex tasks, and detailed planning, it can be applied in a highly quantitative format. Otherwise it consists of a two-dimensional schematic diagram of the relationships among tasks in a R & D project.

Perthophyte
A parasitic organism that kills host tissue before invading it.

Perturbation
Any change to any ecosystem.

Pest
An insect, pathogen, weed, mammal, bird that is judged by man to cause harm to himself, his crops, animals or property.

Pest assessment
The process of counting pests or of eliminating their effect on plants, crops or the environment.

Pest attack
Includes both infestation and injury caused by pests.

Pest density
The population level at which a pest species causes economic damage.

Pest prevalence
The proportion of crops or stands affected by pests in a defined geographical area.

Pesticide
Any substance (chemical or microbial) which by virtue of its toxicity is used to control harmful organisms. ("Pesticide" includes acaricide, bactericide, fungicide, herbicide, insecticide, nematicide, rodenticide etc.).

Pesticide resistance
Genetically selected tolerance of pest populations to pesticides, brought about by the pests' repeated exposure to treatment. Resistance develops to both chemical and microbial pesticides.

Pest intensity
The total number of pests per unit of habitat or same area.

Pest management specialist
A person with sufficient training and experience to successfully manage pest populations.

Pest resurgence
The rapid numerical rebound of a pest population after use of a broad-spectrum pesticide, brought about usually by the destruction of natural enemies that were otherwise holding the pest in check.

Pest spectrum
The complete range of pests attacking a particular crop.

Petal
In plants a division of the corolla in the flower.

Petechiae
Small pinpoints of haemorrhage usually numerous and giving the tissue a red-spotted appearance. They indicate a pathological condition.

Petechiation
The condition shown by a tissue covered with petechiae.

Petiole
The slender stem that supports the blade of a foliage leaf.

Petri dish
A flat, circular dish about 7 cm in diameter and 1 cm high, usually with a matching dish slightly larger in diameter. One fits loosely as a lid to the other. It is used widely in bacteriology to hold culture media, and also as a temporary sterile container for tissues, parasites, blood or body fluids.

Peyer's patches
Lymphoid tissue in the wall of the intestine; not circumscribed by a tissue capsule.

pH (value)
An expression used to designate degree of acidity or alkalinity in a substance. A pH of 7.0 is neutral, below 7.0 is acid, and above 7.0 is alkaline.

Phage (Bacteriophage)
A virus which attacks bacteria, also called bacteriophage.

Phage conversion
A process in which a normal temperate phage modifies the phenotype of a host cell in a way unrelated to the phage immunity system.

Phagocytes
Cells which devour; fixed or moving cells capable of engulfing and/or digesting/destroying some micro-organisms and inanimate particles.

Phagocytosis
Ingestion of particulate material such as bacteria by protozoa and phagocytic cells of higher organisms.

Phagocytise
To exert a phagocytic action. To cause a micro-organism or other small extraneous object to engulfed and digested by a phagocyte.

Pharmaceutical
A chemical produced industrially, which is useful in preventative or therapeutic treatment of disease.

Pharmacodynamics
The study of the way in which xenobiotics exert their effects on living organisms. Also sometimes known as toxicodynamics.

Pharmocokinetics
The study of the movement of xenobiotics within an organism. Such a study must consider absorption, distribution, bio-transformation, storage and excretion. Also sometimes known as toxicokinetics.

Pharyngeal (muscle)
Muscles which surround the pharynx and control the act of swallowing and respiration.

Pharynx
A sac of muscle and membranes at the back of the mouth. At its posterior end is the entrance to the oesophagus; on its floor is the larynx.

Phase 1 reactions
Enzymic modification of a xenobiotic by oxidation, reduction, hydrolysis, hydration, dehydrochlorination or other reactions.

Phase 2 reactions
Enzymic modification of a xenobiotic by conjugation.

Phase separation micro-encapsulation
Micro-capsules are formed by emulsifying or dispersing the core material in an immiscible continuous phase in which the wall material is dissolved and caused to physically separate from the continuous phase and deposit around the core materials. Useful method for micro-encapsulation of pesticides, but suffers from process control and pesticide-loading limitations.

Phasmid
Pore-like structures located in the lateral fields of the tails of nematodes belonging to the class Secerentea. These structures are believed to be chemo receptive and function as sensory organs.

Phellogen
Also called cork cambium; it is cambium giving rise externally to cork and in some plants internally to phelloderm.

Phenolic
Applied to a compound that contains one or more phenolic rings.

Phenolic compound
An aromatic hydroxylated compound or a derivative thereof.

Phenology
Study of the periodic (seasonal) phenomena of animal and plant life and their relations to the weather and climate (e.g. the time of flowering in plants).

Phenotype
Expression of the characteristics of an organism (physical or external appearance) as determined by the interaction of its genetic constitution and the environment; contrast with genotype.

Pheromones
Chemical substance which when released by an animal influences the behaviour of other individuals of the same species, e.g. sex-pheromones, the sexual attractants of insects but pheromones may also elicit a mating response or aggregation response.

Phloem
Living conducting tissue of a plant, a system basically composed of sieve tube, comparison cells, fibres and sclereids to convey the products of photosynthesis, particularly sucrose, from the leaves to growing tissues.

Phoresis
A form of symbiosis when the symbiont, the phoront, is mechanically carried about by its host. Neither is physiologically dependent on the other.

Phoresy
A type of symbiotic relationship in which one organism associates with another species for transportation.

Phospholipid
Lipids containing a substituted phosphate group and two fatty acid chains on a glycerol backbone.

Phosphoroclastic reaction
Breakdown of pyruvate in reactions involving inorganic phosphate and coenzyme A and resulting in the formation of acetylphosphate.

Phosphorylation
(i) The attachment of the phosphate moiety of an organophosphate insecticide to one of the OP-sensitive enzymes (for example, cholinesterase, acetyl-cholinesterase, aliesterase, carboxyesterase), rendering it inactive. (ii) The coupling of inorganic phosphate to adenosine diphosphate (ADP) to form the high-energy molecule adenosine triphosphate (ATP). Addition of phosphate to a molecule, often to activate it prior to oxidation.

Photo-autotroph
An organism able to use light as its sole source of energy and CO2 as sole carbon source.

Photochemical reactions
Or resulting from the chemical action of light.

Photochromogen
An organism (e.g. a Mycobacterium) forming pigment only when exposed to light.

Photoheterotroph
An organism using light as a source of energy and organic materials as carbon source and/or electron donor.

Photoinhibition
Reduction in photosynthesis rate at high light intensities that has been observed for both phytoplankton and terrestrial plants.

Photolysis
The splitting or degradation of a molecule by light, usually ultraviolet; thus, the chemical decomposition of molecules by sunlight.

Photoperiod
Light period of a day. The optimum duration of light and darkness for the normal growth and maturity of a plant in nature.

Photoperiodism
Response of plants and animals to the relative duration of light and darkness.

Photophosphorylation
The formation of high energy compounds by chemical reactions in which light is involved e.g. the synthesis of high-energy phosphate bonds as ATP, using light energy.

Photosensitizer
A chemical that causes increased sensitivity to light.

Photosynthate
Product of photosynthesis, where sun energy fixes carbon dioxide as plant carbohydrate.

Photosynthesis
The enzymatic conversion of light energy into chemical energy and use of this to form carbohydrates (as a by-product) and oxygen from CO2 and H2O in plant chloroplasts.

Phototaxis
Movement towards light.

Phototroph
An organism that obtains energy from light.

Phototropic
The tendency of an organism to turn or move toward light, i.e. positive phototropism; or away from light, i.e. negative phototropism.

Phycology
The study of algae.

Phycomycetes
A class of fungi (the 'algal fungi') characterised by coenocytic (no cross walls) mycelium and sexual reproduction by the union of two sex cells.

Phyla
Name given to an animal group. The characteristics commonly used to group animals into phyla are: type of symmetry, number of cells, number and nature of appendages, internal and external arrangement of body organs, nature of the skeletal system.

Phyllody
The replacement of floral parts by leaf-like structures.

Phylloplane
The two-dimensional micro-environmental space at the leaf surface.

Phyllosphere
The three-dimensional micro-environmental space surrounding a leaf.

Phylogeny
The ordering of species into higher taxa based on evolutionary relationships.

Phylum
A taxonomic entity embodying a group of other taxonomic entities of lesser rank (e.g. the bacteria comprise one phylum).

Physical micro-encapsulation
The wall material and core particles are physically brought together and the wall flows around the core particle to form the micro-capsule.

Physical selectivity
Refers to the use of broad-spectrum insecticides in such ways as to obtain selective action. This may be accomplished by timing, dosage, formulation etc.

Physiologic race
One of a group of forms that are alike in morphology but unlike in certain cultural, physiological, biochemical, pathological or other characteristics e.g. biotypes of a species that differ in the ability to infect particular varieties of the susceptible plant species.

Physiological selectivity
Selective action of insecticides that are inherently more toxic to some insects than to others.

Physiological longevity
Maximum life-span of individuals in a population under specified conditions; the organisms die of senescence.

Physiopath (physiogenic disease)
Any physical or environmental factor capable of producing symptoms of disease in plants.

Physiopathology
Pathophysiology; the study of abnormal function; involving pathological alteration of bodily function.

Phytoalexin
A substance in plants that inhibits the development of micro-organisms produced in response to chemical or physical injury, or when they are infected by a fungus. A large number are now known.

Phytocide
Pesticide compound toxic or injurious to plants in leaf when applied at normally recommended dosages.

Phytopathogen
An organism or virus able to induce disease in plants.

Phytopathogenic
Term applicable to a micro-organism that can incite disease in plants.

Phytopathometry
The measurement of disease.

Phytophagous
Plant-eating pests. Greek form of Latin-based adjective herbivorous.

Phytopharmaceutical
Chemicals applied to plant to control harmful organisms.

Phytoplankton
Plant portion of the plankton; the plant community in marine and freshwater situations which floats free in the water and contains many species of algae and diatoms.

Phytosanitary certificate
A certificate of health which accompanies plants or plant material to be exported.

Phytosanitation
Measures requiring removal or destruction of infected or infested plant material likely to form source of re-infection or re-infestation.

Phytotoxic
Liable to damage or kill plants, especially higher plants, used generally to include the action of intentional herbicides but by some restricted to adverse side-effects to the crop caused by fungicides, insecticides or formulating agents.

Phytotoxin
A substance poisonous to plants.

Pica
Depraved appetite, e.g. the eating of bones or carcasses. May be observed when cattle are fed on a diet deficient in common salt or phosphorous. Care must be taken in the interpretation of pica.

Piecework
A remuneration system where the wage level is directly related to output levels.

Pie chart
A descriptive technique used to exhibit the way in which a single total quantity is apportioned to a group of categories. Each category is assigned a sector of the circle according to the percentage of the total it represents.

Pigeon fly
Family Hippoboscidae, a parasite of pigeons.

Pileus
The cap of a mushroom, bearing the hymenium on its lower surface.

Pilose
Covered with short, usually soft hair or pubescence.

Pilus
A tube-like protein structure that is present on fertile cells, both Hfr and F+, and is involved in DNA transfer during conjugation. Sometimes called sex pilus.

Pinkeye
Bacterial conjunctivitis, sometimes transmitted by flies of the genus Hippolates.

Pinnate leaf
Leaflets arranged along both sides of a common petiole, as in peas.

Pinocytosis
In protozoa, the uptake of macro-molecules into a cell by a drinking type of action.

Pipestem fibrosis
Thickening of the walls of a bile duct as the result of the irritating presence of a parasite.

Piroplasm
Any of the class Piroplasmea, while in a circulating erythrocyte.

Piscicide
Chemical used to kill fish.

Pistil
The female part of a flower (gynoecium) consisting, when complete, of ovary, styles and stigmas, of one or more carpels.

Piston (or Ram) pump
See pump v.

Pit
A small membranous area of a generally thick cell wall.

Pith
The parenchymatous tissue in the central area of a stem.

Pitting
The process of making shallow pits in the soil to retain precipitation. It is usually done with a pitting machine or offset disk in the short-grass region.

Placenta
The membrane, together with its accessories which covers the foetus in the uterus, that established communication including blood supply between mother and foetus. At birth the membrane is broken to release the offspring, and soon after, the umbilical cord which is integral with the placenta is detached from the umbilicus. Later, the placenta is detached from the inner surface of the uterus of the mother and is shed.

Plane of nutrition
Level of feeding.

Planidium
First instar of hymenetamorphic, parasitic Diptera and Hymenoptera, which is apodous but moves actively by means of thoracic and caudal setea.

Planidium larva
A type of first instar larva in some Diptera and Hymenoptera which undergoes hypermetamorphosis.

Plankton
Organisms existing floating or suspended freely in a body of water.

Planning
Setting appropriate objectives for R & D work; then selecting courses of action which are most likely to result in their effective fulfilment.

Planning horizon
Some period of time over which an optimisation algorithm is to be performed.

Plant
Belonging to the plant or vegetable kingdom or to set plants or sow seeds.

Plant food
See plant nutrient.

Plant growth regulator
A chemical other than a nutrient which can be used to modify plant growth.

Plant habit
Plant structure or erectness.

Plant nutrient
A chemical compound used by plants to promote growth, development or reproduction.

Plant pathology
The branch of science concerned with the study of plant disease.

Plant regulator
Any substance or mixture of substances intended through physiological action for accelerating or retarding the rate of growth or rate of maturation, or for otherwise altering the behaviour of plants.

Plaque
A localised circular area of viral lysis of host cells on a lawn of such cells.

Plasma
The non-cellular portion of blood.

Plasmagene
A cytoplasmic-borne unit of heredity.

Plasmalemma
The cytoplasmic membrane found on the outside of the protoplast adjacent to the cell wall.

Plasma membrane
The thin structure enclosing the cytoplasm, composed of phospholipid and protein, in a bio-molecular leaflet structure.

Plasmid
A self-replicating piece of DNA not essential for survival which is found outside the chromosomes of an organism. Typically, plasmids are found in bacteria are used in biotechnology as cloning vectors to introduce foreign DNA into a host cell.

Plasmodesma
A fine protoplasmic thread connecting two protoplasts and passing through the wall which separates the two protoplasts.

Plasmodesmata
Fine protoplasmic connections between cells which extend through the wall.

Plasmodium
A naked multi-nucleate, vegetative body capable of amoeboid motion.

Plasmogamy
A union of cytoplasmic material. The initiation of the diploid phase in the life cycles of certain fungi; nuclei or different mating types come together and divide conjugately as dicaryons but do not fuse until later.

Plasmolysis
Shrinkage of cell protoplasm away from its wall due to removal of water from its large central vacuole.

Plasmotomy
Division of a multi-nucleate cell into multi-nucleate daughter cells, without accompanying mitosis.

Plastic sheeting
A trend towards early harvest of vegetables involves early planting and growing them under plastic sheets to achieve high soil temperatures.

Plastid
Specialised cytoplasmic structures in a cell which are the centre of chemical activity.

Pleiotropic
Having multiple phenotypic expressions.

Pleiotropy
The phenomenon by which a single gene has more than one phenotypic expression.

Pleomorphic
Able to exist in a variety of shapes or forms.

Pleomorphism
(Polymorphism) The occurrence of several forms in the life cycle (e.g. many rust fungi are pleomorphic in that they produce as many as different spore forms in their complete life cycles).

Pleopods
Abdominal appendages of Crustacea.

Plerocercoid
Metacestode that develops from a procercoid. It usually shows little differentiation.

Plerocercus
Tapeworm metacestode in the order Trypanorhyncha in which the posterior forms a bladder, the blastocyst, into which the rest of the body withdraws.

Plerome
The plant tissues inside the cortex.

Plesionecrosis
A symptom exhibited by tissues not yet dead but in the process of dying (wilting for example).

Pleurite
Lateral sclerite of a somite in an arthropod.

Ploidy
The degree of replication of chromosomes (e.g. haploid, diploid, tetraploid etc.) in an organism or cell.

Plumule
The growing point of a plant shoot.

Pneumonia
An infection that results in inflammation of the lungs.

Pneumotropic
Having a selective affinity or predilection for the lungs.

Pod
A dry dehiscent fruit or seed vessel.

Podomere
More or less cylindrical segment of a limb of an arthropod, generally articulated at both ends.

Podosoma
Portion of the body of a tick or mite that bears the legs.

Podsolisation
The process by which soils become depleted of bases and increase in acidity, and leached surface layers are developed and the clay is removed.

Podzolic
Used of acid sandy soils with contrasting red, yellow or black subsoil.

Poikilothermic
Of or pertaining to 'cold-blooded' animals; organisms having no rapidly operating heat-regulatory mechanism; contrast with homeothermic.

Poikilotherms
'Cold-blooded' animals whose body temperature varies, to a large extent depending on the environment.

Point estimator
A single number computed from a sample and used as an estimator of a population parameter.

Point sample
A method of sampling designed to relate the number of individuals or their damage to the number of plants and/or plant parts per unit area.

Points rating
A job evaluation scheme where the 'value' of a job is assessed by totalling points that have been allocated to selected job functions.

Poison
Any chemical or agent that can cause illness or death when eaten, absorbed through the skin, or inhaled by humans or animals (see pesticides).

Poison bait
Attractant foodstuff for insects, molluscs or rodents mixed with an appropriate pesticide.

Poison control centre
Information source for human poisoning cases, including pesticide poisoning, usually located at major hospitals.

Poisson distribution
A discrete probability distribution defined on the non-negative integers having a single parameter. It is commonly used to describe events that occur randomly in time or space.

Poisson probability distribution
A model for finding the probability of count data resulting from any experiment, where the count x represents the number of rare events observed in a given unit of time or space.

Polar flagellation
Condition of having flagella attached at one end or both ends of the cell.

Polar granule
Refractile granule within a coccidian oocyst.

Polarity
Refers to the electronically lop-sided condition of a molecule that has one half more negative than the other half. A state or condition of having poles or possessing parts or regions of opposite or contrasting effects. Polar (hydrophobic) and apolor (hydrophilic) portions of a molecule may be present on a surfactant or a pesticide.

Polar ring
Electron-dense organelles of unknown function, located under the cell membrane at the anterior tip of sporozoites and merozoites.

Polarplast
Organelle, apparently a vacuole, near the polar filament of a micro-sporidean.

Policy
Principles of management established by a leadership to guide research managers at all levels of an organisation.

Polled
Having no horns. Naturally polled, genetically hornless, cf. dis-budded or de-horned by destruction of the horn buds with heat or caustic in calfhood, or amputation of horns when adult.

Pollen
In plants, the male germ cells produced in the anther. When ripe, pollen sacs at the end of the anthers split open to release the pollen. Each ripe pollen grain contains two male nuclei equivalent to male gametes.

Pollen culture
A culture of plant cells derived from pollen in a synthetic medium. The culture will generate progeny with a single set of chromosomes and is a useful means of producing homozygous plants.

Pollination
The transfer of pollen from the male anther to the female stigma of a flower. Pollen carried between anther and stigma of the same flower is called self-pollination while pollen carried from the flower of one plant to another of the same species is called cross-pollination.

Polyandry
Mating of a single female with several males.

Polyarthritis
Inflammation of a number of joints at the same time.

Poly-ß-hydroxybutyric acid
(PHB) A polymer of ß-hydroxybutytric acid; an energy storage compound in procaryotes.

Polyclonal antibodies
An antibody preparation that is the product of more than one clone of plasma cells. Such antibodies react with different components of the antigen (after King & Stansfield, 1990).

Polycross
Selected plants allowed to open-pollinate in isolation, after which the offspring of each may be grown and compared in order to determine the value of the parents.

Polycyclic
Having more than one cycle of infection during a growing season.

Polycyclic pathogen
One that has more than one generation and often many generations per cropping season.

Polydisperse
A collodial sol in which the particle sizes vary within wide limits.

Polyembryony
Development of a single zygote into more than one offspring. However, as Michael Becwar has pointed out, there is a type of polyembryony where more than one egg is fertilized per ovule, therefore, resulting in multiple zygotes per each seed.

Polyetic
Pertaining to a sequence of least two years, as in polyetic epidemic, one in which disease progresses for more than one year.

Polyetic pathogen
One in which the innoculum does not increase during a single growing season but does increase from season to season.

Polygenic
Governed by several or many genes. (See also monogenic and oligogenic).

Polygenic resistance
Resistance to parasites based on many genes, i.e. a series of genes controlling a quantitative character.

Polygyny
Mating of one male animal with several females.

Polyhedron
A spheroidal particle or crystal with many plane faces.

Polyhedrosis
A virus disease of certain insects characterised by the formation of polyhedral inclusions in the tissues of the infected insect; if the inclusion bodies (polyhedra) are formed in the nuclei of the infected cells, the disease is known as a 'nuclear polyhedrosis' and 'nucleo-polyhedrosis'; if the inclusions are formed in the cytoplasm, the disease is known as a 'cytoplasmic polyhedrosis'.

Polymer
A macro-molecular substance made up of many repeating smaller units (monomers) bonded together in chain-like sequences which may or may not be cross-linked. Some monomers such as ethylene (the related polymer is polyethylene) are simple molecules; others, such as the nucleotides of which DNA and RNA are constructed, are large and complex.

Polymeric release systems
The simplest and least expensive way to control the release of an active agent through its dispersion in an inert polymeric matrix. The active agent is physically blended with the polymer powder and then fused together by compression moulding, injection moulding, screw extrusion, calendering or casting (common processes in the plastics industry).

Polymorphic (plemorphic)
Having more than one independent form or spore stage in the life-cycle.

Polymorphonuclear leukocyte
One type of phagocyte, numerous during the acute phase of infection.

Polyphagous
Feeding on or utilising a wide range of organisms e.g. an insect such as an aphid feeds on various secondary host species.

Polypeptide
A peptide composed of many amino acids; a protein.

Polypod larva
Caterpillar type of larva found in Lepidoptera and some Hymenoptera; has thoracic appendages and abdominal locomotory processes (prolegs) also called cruciform.

Polysaccharide
A large organic molecule consisting of many units of a simple sugar.

Polysome
A cluster of ribosomes associated with a messenger RNA.

Polythetic
Positing many essential elements; in classifications, defining groups on the basis of many characteristics, not just one.

Polyvalent (vaccine)
A vaccine containing more than one strain of antibody-producing antigens.

Polyzoic
Strobila, when consisting of more than one proglottid.

Population
An aggregation of similar individuals in a continuous area that contains no potential breeding barriers or a finite or infinite collection of measurements or individuals that comprises the totality of all possible measurements within the context of a particular statistical study.

Population density
The number of individuals of one population per unit area or volume.

Population dynamics
The study and modelling of changes in population size over time.

Population projection matrix
Represents the change in population size in one time step with age-specific fecundities in the first row and survival probabilities on the sub-diagonal. Also called the survival-fecundity matrix or the Leslie matrix.

Porose area
Sunken areas on the basis capituli of certain mites and ticks.

Portal of entry
Point at which the invading micro-organism enters the body of an animal.

Positive displacement (of pumps)
Term applied to pumps (piston, gear etc.) in which liquid will be emitted, regardless of pressure built up, when pump is run.

Positive stain
Procedure in which specimen is stained while background is not.

Positive theories
Theories concerned with 'what is', rather than 'what ought to be'.

Post-emergence herbicides
Applied to control weeds which have emerged in competition with a developing crop. Selectivity may involve differences in herbicide retention, leaf absorption, translocation or metabolism, differences in susceptibility of the ultimate enzyme target sites may also play a part.

Post-emergence treatment
Any treatment made after a the specified weed or crop plants emerge. Application of herbicide to crop after seedlings have emerged from soil and are growing.

Post-emergent
When above-ground seedling growth has appeared.

Posterior probability
The probability p1 of an event at the outset of an experiment might be modified to p2 in light of experimental evidence. The posterior probability p2 is usually determined by employing Bayes' Theorem.

Posterior station
Development of a protozoan in the hindgut of its insect host, such as in the section Stercoraria of the Trypanosomatidae.

Post-harvest
The period between maturity of the crop and the time of its final consumption.

Post-mortem
Subsequent to death. Often used as a term to describe an examination after death, the word examination being inferred.

Post-planting
Applied after transplanting a crop.

Post-planting treatment
A treatment after the crop is planted.

Post-production losses
Losses consisting of the combined harvest losses and post-harvest losses.

Post-translational modification
Modification of a protein after it has been synthesised by enzymatic action.

Potentiation
A term used to describe the enhanced toxicity attained by combining two or more toxicants giving more killing power than the sum of the individual toxicities. Used primarily in pharmacology, synergism being commonly used in insect toxicology.

Pour-on
In relation to pesticides, a solution poured on the skin of animals in a high volume (normally more than 100 ml per animal).

Pour point
The pour point of an oil is the temperature below which the oil will not flow.

Powder for dry seed treatment
A powder for application in the dry state directly to the seed.

Powdery mildew
A growth on a plant surface due to a member of the Erysiphales.

Power of a statistical test
The probability that the statistical test reject the null hypothesis when some particular alternative is true. Power equals (1 - ß). The power is greatest when the probability of a type II error is least.

ppb
Parts per billion (parts in 109 parts) e.g. the number of parts of active ingredient per billion parts of the substance in question.

PPBS
Programme Planning and Budgeting System is a very comprehensive budgeting process which requires considerable effort to develop refined goals, objectives, tasks and costs per each, for all activities in a research organisation. The process is far more accurate than most budgeting techniques - but its level-of-effort precludes the wisdom of doing it annually.

ppm
Parts per million (parts in 106 parts) e.g. the number of parts of active ingredient per million parts of the substance in question. They may include residues in soil, water or whole animals. 10 ppm is equivalent to 0.001%.

Prairie
An extensive, level treeless tract of highly fertile land.

Praniza
Parasitic larva of the isopod sub-order Gnathiidae; parasitises fishes and feeds on blood.

Pre-access interval
The interval of time between the last application of pesticide to an area and safe access to the area for domestic livestock and man.

Precipitation
A reaction between antibody and soluble antigen resulting in a visible mass of antibody-antigen complexes.

Precipitin
An antibody that causes precipitation of soluble antigens.

Precipitin test
A serological test in which the reaction between soluble antigen and antibody results in the formation of a visible precipitate.

Precural (lymph node)
A lymph node situated in the grove of the flank, lower than mid-way between the hip and the patella (or knee bone). It is about 7 cm in length and can be palpated in the live animal. It drains the skin, prepuce and superficial muscles.

Predation
Animal interaction in which the predator kills the prey outright; it does not subsist on the prey while it is alive.

Predator
An animal (or, rarely, a plant) which feeds upon other animals, called its prey. The prey is killed and consumed by its predator which generally devours many individuals during its life (contrast parasite). There are borderline cases between predation and parasitism e.g. species of insects which inject a permanent paralysing drug into a caterpillar before laying eggs in it.

Predicted environmental concentration
The concentration in the environment of a chemical calculated from the available information on certain of its properties, its use and discharge patterns and the associated quantities.

Prediction equation
In regression the equation used to predict the value of the dependent variable y for specified values of the independent variables x1, x2, ..., xk. This equation is generally obtained using the method of least squares.

Predisposing factors
Factors (genetic, cultural or environmental defects) which, by their actions, render an organism susceptible to a certain disease i.e. conferring a tendency to disease.

Predisposition
State or condition resulting from act of predisposing (i.e. inclining or conditioning beforehand, giving a tendency to, a propensity for) as a predisposition to disease.

Pre-emergence damping off
Death of seedlings, as a result of disease, before they have emerged above the soil surface.

Pre-emergence herbicides
A treatment of a fully cultivated field after sowing of the crop seed but before it has emerged. Selectivity may depend partly on differences on the rooting depth of crop and weed.

Pre-emergence spraying
Spraying the soil after the crop has been planted and before the seedlings have emerged.

Pre-emergence treatment
Any treatment made after a crop is planted but before a specified weed emerges. 1. Contact pre-emergence: an application made after weed emergence. 2. Residual pre-emergence: an application which kills weeds as the seed germinates or as they emerge either before or after the crop has emerged.

Pre-emergent
Before above-ground seedling growth has appeared.

Preference
Insect response to plant characters (morphology, architecture, odour, colour) that leads to the use of a particular plant or variety for oviposition, food or shelter (see antixenosis).

Pre-harvest interval
The interval of time between the last application of pesticide and the safe harvesting of edible crops for immediate consumption.

Prehension
The act of seizing, usually the act of taking food with the mouth.

Premune
A type of resistance shown by an animal to a disease micro-organism. This is caused by infection with a sub-clinical amount of that micro-organism. The animal is infected but not affected.

Premunition
Resistance to re-infection or super-infection conferred by a still existing infection, but which does not destroy the organisms of the infection already present.

Pre-nymph
Non-feeding, quiescent stage in the life cycle of a chigger mite.

Pre-oviposition period
The period of time between the emergence of an adult female insect and the start of its egg laying.

Prepenetration period
The period between the time that a vector or propagule is placed on a plant and the time that the host tissues are penetrated.

Pre-planting (pre-sowing)
Applied before planting a crop. A pre-sowing chemical treatment may include a cultivation operation to mix in the chemical, which when the treatment has a herbicidal effect, must enter the plant from the soil.

Pre-planting treatment
Any treatment made before the crop is planted. A treatment to the weeds or soil before the crop is planted.

Prepuce
The fold of skin covering the anterior end of the penis.

Pre-pupa
A quiescent stage between the larval period and the pupa; found in some Diptera and Thysanoptera.

Preputial cavity
The cavity enclosed by the prepuce and surrounding the anterior end of the penis.

Prescapular (lymph node)
The lymph node situated in the groove between the shoulder and the neck. It lies about 10 cm above and in front of the point of the shoulder and is partly covered by the shoulder muscles. It lies rather deep, but can generally be palpated in the live animal. It drains the neck, shoulder and fore-limb.

Presoma
The proboscis, neck and attached muscles and organs of an acanthocephalan.

Pre-sowing herbicide application
Used in situations where difficult perennial weeds require the use of herbicides which are not selective in relation to the proposed crop; the persistence of the compound must be taken into account.

Prevalence (of a disease)
The total number of cases of a particular disease at a given moment of time, in a given population.

Preventative
A measure applied in anticipation of pest attack.

Preventive treatment
Treatment designed to prevent a plant becoming infected.

Prey
An animal when fed upon by a predator. A predator of one species can itself be prey to another.

Price effect
The change in the basket of goods selected by a consumer which takes place when the price of one of the goods changes.

Pride
A mating group of lions.

Primary amino acid sequence
The order of amino acids in a peptide or protein; determines the active three-dimensional structure of a protein.

Primary budgets
The general term used to describe the sales production and finance budgets. All other budgets (except the master budget) are then referred to as subsidiary budgets.

Primary consumer
Animals that consume plants.

Primary culture
A culture started from cells, tissues or organs taken directly from organisms not including cultures started from explants of tumours developed by injecting cultured cells into animals.

Primary cycle
The first cycle of a pathogen initiated after a period of pathological inactivity, usually after rest or seasonal inactivity (dormancy).

Primary electron donor
The first molecule to donate electrons in an electrochemical sequence.

Primary host
Plant on which the sexual and overwintering phase of the aphid occurs.

Primary infection
The first infection of a plant in the spring by the overwintering pathogen.

Primary inoculum
Propagules of the parasite that cause initial infection on the host. The overwintering pathogen or its spores that cause primary infections.

Primary migrants
In insects synonym of alate fundatrigeniae.

Primary noxious weeds
Perennial weeds that are difficult to control and that have been designated by the state as primary noxious.

Primary parasite
A parasitoid that develops in or on non-parasitic hosts.

Primary producers
Plants, biota that convert carbon dioxide and water into carbohydrates.

Primary production
The initial synthesis of organic matter from inorganic nutrients in an ecosystem; carried out by either phototrophic or lithotrophic autotrophs.

Primary root
The first or seminal root.

Primary symptoms (infection)
The symptoms that develop at the site of virus entry.

Prime costs
The total of all direct labour, direct material and direct expenses.

Primer
A short oligonucleotide that base-pairs to a region of a single-stranded template oligonucleotide. Primers are used to copy adjacent sequences of mRNA and cDNA's.

Priming
A term to designate the harvesting of ripe tobacco leaves from the stalk as they ripen, beginning at the bottom and progressing upward.

Primite
Anterior member of a pair of gregarines in syzygy.

Principle of comparative advantage
An economic principle recognising that various crops and livestock should be produced in areas where the physical and other resources most favour such production.

Principle of diminishing returns
The generalisation that as more and more of a variable factor is added to a fixed factor, in order to produce more output, the additional output per unit of variable input must decline.

Prion
Protein infectious agent; a sub-cellular entity composed only of protein and containing no DNA or RNA, which causes infectious diseases such as scrapie in sheep, prions are reproduced during the infection.

Prior probability
The probability representing the likelihood of occurrence of an event before experimental evidence relevant to the event has been observed. The unconditional probabilities used in Bayes' Theorem are prior probabilities.

Probabilistic model
A model that incorporates some random element in its formulation as opposed to a deterministic model.

Probability density function
The derivative of a continuous cumulative distribution function. Denoted by f(x).

Probability distribution
A formula, table or graph providing the probability associated with each value of the random variable if the random variable is discrete or if continuous providing the fraction of measurements in the population falling in specific intervals. Denoted by p(x).

Probability of an event
The probability of an event A is equal to the sum of the probabilities of the sample points in A.

Probability transition matrix
A matrix of probabilities of transition in one time step between discrete states in a Markov chain model.

Probability tree
A visual model to display the outcomes of an experiment in which each successive branch of the tree corresponds to a step necessary to generate the possible outcomes of an experiment.

Probe
A piece of labelled DNA or RNA which is used to locate another piece of nucleic acid by complementary base pairing. The reaction is monitored by auto-radiographic or enzymatic detection of the hybridisation.

Procaryote
A simple type of cellular organism which lacks a nucleus, organelles, chromosomes, and is unable to carry out sexual reproduction; bacterium (both archaebateria and eubacteria).

Procercoid
Cestode metacestode developing from a coracidium in some orders. It usually has a posterior cercomer.

Procuticle
Thicker layer beneath the epicuticle of arthropods that lends mass and strength to the cuticle; it contains chitin, sclerotin and also inorganic salts in Crustacea; layers within procuticle vary in structure and composition.

Prodromal
Premonitary; a symptom of sign of disease, which appears very early and indicates the presence of the disease.

Prodrome
A premonitory symptom or sign, indicating the onset of a disease.

Producer
An auto-trophic organism or population, usually of green plants, that procures energy from outside the ecosystem and through the process of photosynthesis converts this energy into living organic matter within the system.

Production
Amount of energy (or material) formed by an individual, population or community in a specified time period; see primary production, secondary production, gross production, net production.

Production (or response) function
The relationship between the levels of inputs and the level of output for a production process.

Productivity
Productiveness; the quality or state of being productive; a measure of the utilisation of available resources (including time) by soil, an organism or a population or community of organisms.

Profile
A vertical section of a soil through all its horizons.

Profit
A general term indicating some kind of surplus from the years farming operations.

Profit centre
A type of responsibility centre where the manager is responsible for costs and revenues and therefore profit. Managers have no authority over the level of investment in this case.

Profit margin
A ratio used to measure performance, calculated by expressing gross or net profit as a percentage of sales value.

Profit sharing
A group incentive payment scheme that is supposed to improve employee goodwill towards the enterprise.

Profit/volume chart
A chart or graph depicting profit or loss at all levels of activity.

Profitability
A relative measure of performance found by expressing profit as a percentage of capital employed and/or turnover.

Proglottid
One set or reproductive organs in a tapeworm stroliba; it usually corresponds to a segment.

Prognosis
Forecast of the probable course of a disease.

Programme
A group of R & D projects which are related either by a common technology, a common sponsorship organisation or a common executing unit of a research organisation.

Progressive infection
An interaction between an infectious agent and its host, resulting in overt disease of the host.

Prohaptor
Collective adhesive and feeding organs at the anterior end of a mono-genetic trematode.

Project
A discrete collection of R & D tasks which are required to fulfil a specific set of related R & D goals, and/or resolve a specific development problem.

Project planning
Focuses on R & D projects; generates specific project objectives, tasks, resource requirements and schedules.

Prokaryote
An organism (bacterium or blue green algae) which has its genetic material in diffuse filaments scattered within the cell and not within the confines of a nucleus.

Prolegs
The fleshy, unsegmented leg-like structures on the abdomens of some larvae e.g. those of Lepidoptera and sawflies.

Prolepsis
A hyperplastic symptom of disease in which organs appear before the natural time (e.g. the sprouting of shoots from adventitious buds after disease has impaired the metabolism of the organ in question).

Proliferation
A rapid and repeated production of micro-organisms, new cells, tissues, or organs; specifically, a hyperplastic symptom of plant disease in which organs continue to develop after they have reached the point beyond which they normally do not grow.

Promastigote
Form of Trypanosomatidae with the free flagellum anterior and the kinetoplast anterior to the nucleus, as in Leptomonas.

Promiscuous
Mating system in which males and females are not restricted to one sexual partner. Also of legume root-nodule bacteria: forming nodules with any local strains.

Promoter
The region of DNA which binds RNA polymerase and directs the enzyme to the correct site where transcription of the gene will begin. Also, an agent which increases tumour production by a chemical when applied after exposure to the chemical.

Promycelium
The short hyphal filament of basidium produced meiotically by the germinating rust spores (Chlamydospores) of the smuts, or tiliospores of the rusts.

Pronotum
The dorsal sclerite of the prothorax in insects.

Propagative virus
A virus which multiplies in its vector.

Propagule
Any structure specialised for the reproduction or dispersal of the species. In plants a propagable shoot.

Propellant
An inert ingredient in self-pressurised products e.g. aerosol cans that produces the force necessary to dispense the active ingredient from the container.

Prophage
The state of a temperate virus when it is integrated into the host genome. A lysogenic bacterial virus which is integrated into the host cell DNA.

Prophylactic
Pertaining to prophylaxis, the prevention of disease. Treatment, usually immunologic, designed to protect an individual from a future attack by a pathogen.

Prophylactic control
The control decision is made prior to pest attack and applied irrespective of level of attack subsequently obtained. In many cases the measures will be strictly pre-emptive e.g. use of resistant cultivars. Spraying pesticides to a fixed calendar schedule is also a form of prophylactic control, since again the decision is made in advance of any knowledge of actual levels of pest attack.

Prophylaxis
Treatment, usually immunologic, designed to protect an individual from a future attack by a pathogen.

Propioceptor
A receptor that responds to stimuli arising within the organism.

Propodeum
First abdominal segment of hymenopterans, fused to the thorax.

Propodosoma
Portion of the podosoma that bears the first and second pairs of legs of a tick or mite.

Propolar cells
Anterior tier of cells in the calotte of a dicyemid mesozoan.

Proportional allocation
An allocation procedure in stratified random sampling that partitions the sample size among the strata proportional to the size of the strata.

Proposal
A statement of the objectives, methods, resources and management plan for a R & D project.

Proprietary compound
Distinguishing name applied by manufacturer to his formulated product.

Proprietary technology
Technological knowledge which can only be used with the permission of its owner.

Prosoma
Anterior tagma of arachnids, consisting of cephalothorax; fused imperceptibly to opisthosoma in Acari.

Prostheca
A cytoplasmic extrusion from a cell such as a bud, hypha or stalk.

Prosthetic group
The tightly bound, non-protein portion of an enzyme; not the same as coenzyme.

Protandrous
Stamens shedding pollen before the stigma is receptive.

Protandry
Maturation first of the male gonads, then of the female organs, within a hermaphroditic individual; also called androgyny.

Protease
An enzyme which degrades protein into their component amino acids.

Protectant
A substance that protects an organism against infection by a pathogen.

Protectant fungicide
Fungicide applied to plant surface to inhibit germination of colonising pathogens.

Protection
As a principle of plant-disease control, the placing of a barrier between suscept and pathogen (e.g. the use of protective chemical dusts or sprays).

Protective clothing
Clothing protecting spray operator from adverse effects of crop protection chemicals: may include rubber gloves, rubber boots, apron or overall, respirator, face-mask, etc.

Protein
High molecular weight compounds containing nitrogen, carbon, hydrogen, oxygen and usually sulphur (amino acids). It is an essential part of the protoplasm of all living cells. Proteins may be structural or an enzyme.

Protein binding
The process by which drugs and toxins are bound to proteins other than the receptor, in the plasma or (less common) intra-cellularly. The bound fraction is inactive by is in equilibrium with the free fraction in the cell or plasma.

Protein biotoxins
Proteinaceous toxins derived from micro-organisms, e.g. Bacillus thuringiensis endotoxin or invertebrates e.g. spider venom, that can be used as an insecticide.

Protein subunit
A small protein molecule that is the structural and chemical unit of the protein coat of a virus; a capsomere.

Protein synthesis
The production within a cell of proteins encoded by information in the DNA; involves the processes of transcription and translation.

Protelean parasite
Organism parasitic during its larval or juvenile stages and free living as an adult.

Protersoma
Combination of the gnathosoma and propodosoma of the body of a tick or mite.

Prothorax
The first segment of the thorax, which bears the first pair of legs.

Protista
Taxonomic classification including all micro-organisms.

Protogynous
When the stigma is receptive before the pollen is shed.

Protomerite
Anterior half of a cephaline gregarine protozoan.

Proton gradient
A separation of protons (H+) such that there are more on one side than on the other side of a membrane.

Proton-motive force
The force established by a proton gradient; the mechanism by which energy released in respiration reactions is stored before being converted to chemical energy in the form of ATP.

Protonymph
Early, bloodsucking stage in the life cycle of some mesostigmatid mites.

Protonymph
The second instar of mites.

Protopam chloride (2-pam)
An antidote for certain organophosphate pesticide poisoning, but not for carbamate poisoning.

Protophloem
The conductive tissue of actively growing parts of the plant. Its sieve tubes function for a brief period, and are replaced by metaphloem elements.

Protoplasm
The only known form of matter in which life is manifest. The essential material of all animal and plant life. It is the main part of the cell; it is composed of proteins, lipids, carbohydrates and salts.

Protoplasmic cylinder
The central structure of a spirochete, consisting of the cytoplasm and regular wall units. Outside the protoplasmic cylinder are the axial fibrils and the outer envelope.

Protoplast
The unit of living substance, a cell from which the cell wall has been removed by mechanical or enzymatic means. Protoplasts consist of plasma membrane, cytoplasm, nucleus and other organelles and can be prepared from primary tissues of most plant organs as well as from cultured plant cells.

Protoplast fusion
Any induced or spontaneous union between two or more protoplasts to produce a single bi- or multi-nucleate cell. In particular, a tissue culture procedure for somatic hybridisation that is used in cell manipulation studies.

Protopod
Coxa and basis together.

Protopod larva
Larva found in some parasitic Hymenoptera and Diptera; limbs rudimentary or absent; internal organs incompletely differentiated; requires highly nutritive and sheltered environment for further development.

Protoscolex
Juvenile scolex budded within a coenurus or hydatid metacestode of a taeniid cestode.

Prototroph
The wild-type parent from which an auxotrophic mutant has been derived.

Protoxylem
The conductive tissue that appears at the beginning of vascular differentiation and usually matures before the organ completes its elongation; it is followed by formation of metaxylem which matures after tissue elongation is finished.

Protozoa
Eucaryotic single-celled animal-like micro-organisms including amoebas, flagellates, ciliates and sporozoans.

Proventriculus
The anterior part of the stomach of a bird. Also the anterior part of the stomach of a fly.

Provirus
A non-infectious intra-cellular form of a virus; the genome of a virus - essentially a nucleic acid; it is perpetuated in stable association with the internal structure of the host cell.

Proximal
Situated towards the centre of the body.

Proximate factors
In evolutionary terms the mechanisms responsible for an adaptation with reference to its physiological and behavioural operation; the mechanics of how an adaptation operates; opposite of ultimate factors.

Pruritis or Pruritus
Intense itching.

Pseudolabia
Bilateral lips around the mouth of many nematodes of the order Spirurata; they are not homologous to the lips of most other nematodes but develop from the inner wall of the buccal cavity.

Pseudomyiasis
Presence within a host of a fly not normally parasitic.

Pseudopodia
Protrusions, finger-like processes put out by an amoeba and used as a means of locomotion.

Pseudorandom numbers
Numbers generated by an algorithm that appear to be random (when in fact they are not).

Pseudo-recombinants
New strains of a virus that result from the re-assortment of genome nucleic acids during the replication of viruses with divided genomes in mixed infections.

Pseudo-resistance
Apparent resistance in a potentially susceptible host resulting from chance, from transitory (non-heritable) traits, or from environmental conditions.

Pseudothecium
A fruiting body of some fungi containing asci similar in appearance to a perithecium, but produced in an aggregation of vegetative hyphae.

Psoroptic mange
Disease caused by mites of the genus Psoroptes.

Psychrophile
An organism able to grow at low temperatures. An organism that grows best at cold temperatures.

Psycotroph
A facultative psychrophile; an organism able to grow at 0°C but also able to grow at temperatures of 25 to 30°C.

Pterostigma
A thickened opaque or dark spot along the costal margin of the insect wing, near the tip.

Ptilinum
Balloon-like organ in the head of teneral dipterans that pushes off the operculum of the puparium.

Pubescent
Covered with fine, short hairs.. In plants may affect wetting of foliage and retention of spray.

Pubis
The ventral bone of the pelvic girdle, lying between the two hip joints.

Public health impact assessment
Applying the risk assessment to a specific target population. The size of the populations needs to be known. The end product is a quantitative statement about the number of people affected in this specific target population.

Pulling resistance
Resistance of plants to being pulled out of ground or uprooted by pulling.

Pulmonary septa
The walls between the lobules of the lung.

Pulse
Large-seeded legumes.

Pump
i) centrifugal. Pump in which liquid is thrown into delivery volute by centrifugal force from vanes of rapidly rotating impeller ii) diaphragm. Pump similar in action to piston pump but with oscillating plate and flexible membrane in place of piston iii) gear. Pump in which liquid is transferred from inlet to outlet in spaces between teeth on two meshing gears and casting iv) injector. Device through which residual liquid in sprayer can be circulated, so as to draw in water at greater rates than can be achieved by using pump directly v) piston (or Ram). Pump in which liquid is in turn drawn in and expelled from cylinders by reciprocating pistons vi) roller-vane. Pump in which liquid is transferred between vanes formed by rollers bedded in surface of rotor

Punctiform
Shaped like a dot.

Punky
Biting midge of the family Ceratopogonidae.

Pupa
An inactive stage in the life cycle of some insects with complete metamorphosis; a non-feeding and usually inactive stage, pl. pupae.

Pupariation
Formation of a puparium by third-stage larvae of certain families of Diptera.

Puparium
Pupal stage of certain families of Diptera.

Pure culture
An organism growing in the absence of all other organisms.

Pure line
A strain in which all members have descended by self-fertilisation from a single hymozygous individual.

Purification
The separation of virus particles in a pure form free from cell components, and their concentration.

Purpura haemorrhagica
A disease of horses usually seen as a sequel to upper respiratory infection and characterised by oedema of subcutaneous tissue. It is mostly encountered in horses during and after shipment.

Purulent
Full of discharging pus.

Pus
The fluid containing cellular debris, pathogens and phagocytic cells which accumulates in some areas of inflammation and is characteristic of pyogenic infections.

Pustule
A blister-like fungal spore mass breaking through a plant epidermis. A pimple-like, eruptive fruiting structure, such as a uredinium of a rust fungus.

p-value
The smallest value of _ (the probability of make a type I error) for which test results become statistically significant.

Pycnidiospore
An asexual spore produced in a pycnidium.

Pycnidium
An asexual, spherical or flask-shaped fruiting body lined inside with conidiophores and producing conidia.

Pycniospore
Also called a spermatium. A spore produced in a pycnium.

Pycnium
Also called a spermagonium. A fruiting body of the rust fungi that produces small spores called pycniospores or spermatia which cannot infect plants but function as gametes or gametangia.

Pycnospore
An asexual spore produced in a pycindium.

Pygidium
Sensory organ of a posterior tergite of fleas, which apparently detects air currents.

Pygmism
The state of being dwarfed or reduced in size.

Pyloric region
The area of the stomach adjacent to the pyloris, i.e. the opening from the stomach into the intestine.

Pyloric sphincter
The ring of muscle which contracts and expands to close or open the pylorus, so regulating the flow of food from the stomach to the intestine.

Pyogenic
Pus-forming; causing abscesses.

Pyrogenic
Fever-inducing.