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Glossary of Terms

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A localised proliferation of plant tissue caused by the irritation of bacteria, fungi, mites or insects.

Hyphal portions of Zygomycetes which fuse to form zygospores in sexual recombination.

The cell or organ in which gametes develop.

A reproductive cell or germ cell (in plants the ova and pollen grains), usually haploid in chromosome number, and capable of uniting with another gamete of the opposite sex to form a new plant or animal.

Game theory
A technique for predicting the actions which interdependent rivals may take in their relations with each other.

The sexual cell in the life cycle of a protozoon which gives rise to a gamete when taken into the body of the vector. It may be male (micro-gametocyte) or female (macro-gametocyte).

A phase in the life history of a plant that arises from a haploid spore resulting from meiosis in a diploid sporophyte; plants have haploid nuclei during the gametophyte phase.

Gamic females
Sexual, egg-laying females (= oviparae).

Gamma function
A function, denoted by _(x), that for integers has the value (x-1)!. A normalised version is used here as a prototype fro the effect of temperature on various processes.

Gantt chart
Simply another name for a 'bar chart'; sometimes called this because it was refined as an instrument for planning by a man named Gantt.

Gastrocnemius (muscle)
The large muscle, posterior to the upper part of the tibia, attached at its upper end to the femur, and merging at its lower end into the tendon of Achilles (the 'hamstring').

Gas vesicle
A gas-filled structure in certain procaryotes that confers ability to float. Sometimes called gas vacuole.

Gause's Principle
See competitive exclusion.

Gear pump
See pump iii.

A jelly-like collodial mass.

The process by which starch granules change to a jelly-like form and fill the voids in the grain and cement the fissions together during parboiling.

Gelatinisation temperature
The temperature at which gelatinisation takes place. It is between 55 - 75°C depending on variety.

A molecular sieving procedure, by which viruses are separated from different sized molecules when passed through the pores of gel beads such as agarose. Used for virus purification.

Gel double-diffusion
A serological test in which the antibody and antigen reactants diffuse towards each other in gel and react to form a visible precipitation line.

The unit of inheritance found in the chromosome. The linear units of heredity transmitted from generation to generation during sexual or asexual reproduction. Each gene is a segment of nucleic acid carried in the DNA encoded for a specific protein. More generally, the term 'gene' may be used in relation to the transmission and inheritance of particular identifiable traits. Minor gene: a gene that has small observable effects upon the phenotype Major gene: a gene that has large observable effects upon the phenotype.

Study of population genetics in relation to the habitat conditions, the study of species and other taxa by the combined methods, and concepts of ecology and genetics.

Gene expression
Evidence or manifestation of a genetically controlled characteristic. All of the chromosomal genes in an organism are not active at all times. In a plant nucleus as little as 5% of the DNA may be producing protein at any one time.

Gene-for-gene concept
The concept that corresponding genes for resistance and virulence exist in host and pathogen respectively.

Gene-for-gene hypothesis
The concept that corresponding genes for resistance and virulence exist in host and pathogen, respectively.

Gene-for-gene resistance
See vertical resistance.

Gene mapping
Determining the relative locations of different genes on a given chromosome.

Plural of genus, the term used in classification for a group or category of plants or animals subordinate to a tribe or family, and superior to a species.

General resistance
Analogous to horizontal resistance, biotype non-specific resistance. Sometimes used to designate resistance to more than one disease.

General use pesticide
A pesticide that can be purchased and used by the general public without undue hazard to the applicator and environment as long as the instructions on the label are followed carefully. For comparison see Restricted-use pesticide.

The period from any given stage in the life cycle (usually adult) to the same stage in the offspring.

Generation curve
The population density of a given developmental stage plotted against generation number for a sequence of generations.

Generation time
Time needed for a population to double.

Pertaining to the action of a chemical that prevents sporulation.

Genetic base
Genetic constitution.

Genetic code
The nucleic acids, DNA (deoxyribonucleic acid) and RNA (ribonucleic acid) are the molecular substances in the cell nucleus, that are carriers of genetic information and are thus the basic genetic material in all living things. DNA occurs in the form of a double helix which acts as a template to reproduce itself. RNA is concerned with carrying the genetic information to the cytoplasm of the cell and establishing the genetic specifications there. Each of the various DNA assemblies can be called a gene.

Genetic control
A pest control method which makes use of selected strains of the target species that possess genetic abnormalities. When released into the target population they mate with wild individuals and produce sterile offspring (see sterile insect technique).

Genetic engineering
Procedures involved in the isolation, manipulation and expression of genetic material, combining DNA from two different organisms, either for basic research or in the development of industrial processes.

Genetic marker
Any mutant gene useful in genetic analysis.

Genetic pool
The total genetic information possessed by the reproductive members of a population of sexually reproducing organisms (King & Stansfield, 1990).

Genetic toxicology
The study of chemicals which can produce harmful heritable changes in the genetic information carried by living organisms in the form of DNA.

The science dealing with heredity.

Genetic shift
Change in genetic constitution.

Of or relating to a gene or genes.

Genital artrium
Cavity in the body wall of a flatworm into which male and female genital ducts open.

Genitointestinal canal
Duct connecting the oviduct and intestine of some polyopisthocotylean Monogenea.

The entire hereditary message of an organism. The total genetic composition of the chromosomes in the nucleus of a gamete. The nucleic acid component of a virus.

Genomic library
A collection of recombinant DNA molecules or clones which collectively comprise the total genome of an organism.

Able to cause harmful heritable changes in DNA.

The entire genetic make up of an organism, expressed and latent, dominant and recessive. The individuals of the same genotype breed alike. A group of organisms with the same genetic make up. Contrast with phenotype.

The principal subdivision of a family next above a species. A group of related species with similar characteristics and appearing to have a common ancestry.

An area around the pod of a groundnut plant. It is usually used to describe the area in which the pod influences the microbial complement of the soil.

Eating earth or clay.

A compound produced by many cyanobacteria and streptomycetes which cause the 'earthy' odour of soil.

Turning downward in response to a stimulus caused by the force of gravity.

Germ free
Devoid of micro-organisms.

Germ-free animals
Animals that have been raised since birth in a sterile environment and which contain no microbial flora.

A substance that inhibits or kills micro-organisms.

Capacity to germinate or form seedling from seed.

The process in which a dispersal unit, e.g. a fungal spore or seed, under specific environmental conditions, assumes increased metabolic activity, resulting in the production of new structures, most often a germ tube or growth of embryo in a seed.

Often synonymous with 'genetic material' it is the name given to seed or other material from which plants are propagated. An early theory of inheritance advanced the notion that hereditary characters were contained in an immutable 'plasm' transmitted unchanged from parent to offspring (literally (Greek): a plasm is a mould or matrix in which materials may be cast or formed: a 'plasma' is the result). A germplasm bank is an organised collection of seed or other genetic material (each genotype entered being called an accession) from which new cultivars may be generated. In a zoological context germplasm banks would include collections of preserved sperm or ova and in some cases the animals from which they are derived.

Germ tube
The initial hyphal growth from a germinating fungal spore which develops into a mycelium.

A genus of bugs (hemiptera) with long legs, adapted to resting and moving upon the surface of water of normal surface tension.

Gestation period
The period of embryonic development in mammals.

Giant cell
A multi-nucleate mass of protoplasm formed by coalescence of several adjacent plant cells. Also called a syncytium. Found in plants infected by certain nematodes.

A group of plant growth-regulating substances with a variety of functions.

Disorientation caused by cysticerci in the brain; usually manifested by staggering or whirling.

A lamella of a gill fungus.

Gill fungi
Mushrooms; members of the family Agaricaceae of the class Basidiomycetes which produce fruiting bodies consisting of a stipe that supports a pileus whose lower surface has radially arranged lamellae bearing the hymenium.

The second stomach in birds, in which the food is ground.

Hairless or smooth; the opposite of pubescent, usually in reference to plant surfaces.

Having or bearing secreting organs or glands.

Covered with a whitish, waxy bloom.

Waterlogged, usually with white or blue-grey sub-soil.

Glial cells
Non-nerve cells in a brain or ganglion; their function is obscure, but they may support the life processes of the neurons.

Gliding motility
A property found in many bacteria of motility without the agency of flagella or other exterior organs of motility.

Global stability
Ability to withstand perturbations of a large magnitude and not be affected; compare with neighbourhood stability.

Global variables
Variables appearing in a number of simulation subroutines.

A disease of minor importance in cattle and horses in Africa characterised by dermatitis. It is caused by a protozoan, Globidium besnoiti. The dermatitis which may be severe, is accompanied by a nasal discharge, and sometimes severe diarrhoea.

Tongue-like mouthpart in Hymenoptera (considered a hypopharynx by some authors).

Synthesis of glucose from smaller molecules.

In grasses, either of two empty bracts at the base of a spikelet.

The protein in wheat flour which gives dough strength, plasticity and rising power.


Finely filamentous layer of polysaccharide found on the outer surface of many cells, from 7.5 to 200 hm thick.

Reactions of the Embden-Meyerhof pathway in which glucose is oxidised to pyruvate.

An enzyme capable of splitting a glycosidic bond.

Glyoxylate cycle
A pathway which is a branch from the tricarboxylic acid cycle; useful in replenishing oxalacetate for further TCA cycle activity.

Prehensile appendages of some Crustacea, e.g. the second and third thoracic legs of Amphiphoda and the first thoracic legs of some Isopoda.

Adjective used to describe the condition of being free of microbial contamination e.g. a plant that has been grown from a surface sterilised seed in a sterile environment.

Field of biology concerned with breeding or culturing of organisms by themselves or in association with other completely known kinds of organisms.

Goal congruence
When the objectives of an individual manager coincide with those of the organisation.

General statements of the desired outcomes of R & D.

Markings on the stigmatal plants of certain hard ticks.

A warehouse used for storing paddy or rice either in bulk or bag.

Golgi apparatus
A secretory body found in the cell; named after the Italian biologist C Golgi.

A system, usually animal, in which the composition of the microbial flora is known.

Muscular sucker or other perigenital specialisation surrounding or associated with the genital atrium of a digenetic trematode.

Goodness of fit
A measure of agreement between the observed values of a random variable and corresponding values derived according to a theoretical model, or an hypothesis under test.

Head of pesticide sprayer lance inclined at 60 to shaft.

A pigment C30H30O that occurs naturally in cotton plants and is toxic to some insect pests.

Governance structure
The framework which governs a transaction.

A slope or incline. In plant pathology, an observed progressive change with distance of the concentration of spores, lesions or diseased plants, or in the value of an environmental attribute.

The separation of produce into different categories according to size, weight, colour, quality

Totality of all factors that impinge on a population, including biotic agents and abiotic factors.

Gradual metamorphosis
The growth changes in insects from newly hatched nymphs to adults.

A method of plant propagation by transplantation of a bud or a scion of a plant on another plant. Also, the joining of cut surfaces of two plants so as to form a living union.

Caryopsis or 'naked seed' of large-seeded grasses; a collective term for the cereals.

Grain bait
Special form of bait.

Grain loss
The loss in weight, occurring over a specified period and expressed on a moisture-free basis, of grain which would otherwise have been available as human food.

Gram negative
Bacteria not capable of being stained by the standard Gram stain.

Gram-negative bacteria
Bacteria which stain pink in the differential stain, called the Gram stain; contain an outer membrane outside of the cell wall.

Gram positive
Bacteria capable of being stained by the Gram stain.

Gram-positive bacteria
Bacteria which stain blue in the differential stain, called the Gram stain; possess a thick cell wall with no outer membrane.

Derived from granite.

A dry formulation of pesticide and other components in discrete particles generally less than 10 mm3 in size.

Granular bait
Special form of bait.

Granular formulation
A free-flowing solid product of a defined particle size range, ready for use.

A pesticide formulation (incorporating inert material) in the form of discrete dry particles of uniform size for application as dry dressing without further preparation or dilution.

Granule applicator
Machine designed to apply measured quantities of granules.

Granulomatous (pus)
Pus in which there are small granules, usually clumps of pyogenic micro-organisms.

A virus disease of certain insects characterised by the presence of minute granular inclusions in infected cells.

Grape stage
See fruit-bud stage v.

Botanically, a plant of family Gramineae.

Nuclepolyhedrosis of the silkworm, Bombyx mori.

A method of feeding by herbivores characterised by repeated removal of only a part (generally the leaf) of the plant (most commonly herbage, such as grasses and clovers).

Grazing capacity
The number of animals a specified pasture will carry for a specified period.

Very viscous formulation based on oil or fat.

Grease band
Adhesive material (e.g. resin in castor oil) applied as band round tree trunk to trap ascending wingless female moths.

Green bridge
Living plant material used by biotrophs to overwinter.

Green-flower (green -cluster) stage
See fruit-bud stage vi.

Green island effect
A green ring of tissue in a senescent leaf surrounding an individual rust pustule.

Green manure
A crop grown and ploughed under to improve the soil.

Green muscardine
A mycosis of various larval, pupal and adult insects, caused by hyphomycetous fungus Metarrhisium anisopliae.

Gregarious parasite
A parasitoid whose food requirements are such that from several to many can develop simultaneously in or on the body of the host.

The ease with which material may be broken down by mechanical means.

In relation to pesticide formulations, hard non-friable particles present in a material.

Gross income
The total value of a farm activity, i.e. during a production period (usually 1 year) whether the product is sold, consumed or stored.

Gross margin
Gross income minus variable costs.

Gross margins planning
A procedure whereby activities are selected on the basis of the gross margin from a unit of only one key constraint, usually labour or land.

Gross pathology
The study of macroscopic structural lesions and abnormalities distinguished from histopathology.

Gross production
Production before respiration losses are subtracted; photosynthetic production for plants and metabolise production for animals.

Gross profit
The difference between sales and the cost of sales before charging general overhead expenses.

Gross profit margin
Gross profit expressed as a percentage of sales.

Ground itch
Skin rash caused by bacteria introduced by invasive hookworm larvae.

A self-sown plant, especially potato.

The vegetative development of plants expressed in terms other than market or monetary units; e.g. the size or number of leaves, shoots, ears etc.

Growth factor
An organic compound required in very small amounts as a nutrient.

Morphological categories of plants, such as trees, shrubs and vines.

Growth inhibitor
A natural substance that inhibits the growth of a plant.

Growth 'profit'
Increase in equity or savings.

Growth rate
The rate at which growth occurs, usually expressed as the generation time e.g. increase in cell number or mass per unit time.

Growth regulators
Organic substance (often hormones) that are effective in minute amounts for controlling or modifying (plant or insect) growth processes.

Growth stage
A morphologic phase of plant or crop development that can be easily recognised in the field.

Growth stage keys
A series of diagrams or of descriptions illustrating and coding sequential phases of plant or crop development which can be easily recognised and recorded.

Growth stages of grain crops
1. Tillering stage: when a plant produces additional shoots from a single crown, as in wheat. 2. Jointing stage: when the internodes of the stems are elongating. 3. Boot stage: when the leaf sheath swells up due to the growth of developing spike or panicle. 4. Heading stage: when the seed head of a plant begins to emerge from the sheath.

The larvae of a beetle.

Grub (White)
General term for larvae of Coleoptera. They tend to be thick bodied, with a well developed head and thoracic legs, without abdominal prolegs, usually sluggish in behaviour.

Digging out roots.

Complex polysaccharidal substances formed by cells in reaction to wounding or infection.

Production of gum by or in a plant tissue.

Gun, Spray
Lance with nozzle incorporating variable-depth swirl chamber, instantly adjustable by operator.

The process by which plants expel water from uninjured leaves in excess of transpiration. Exudation of water from plants, particularly along the leaf margin.

Maturation first of the female gonads within an individual, then of the male organs; also called protogny.

Gynocophoral canal
Longitudinal groove in the ventral surface of a male schistosome fluke.

Female part of flower.

Parthogenetic females which produce sexual females; in heteroecious aphids, the return migrants to primary host in the autumn.