[A] [B] [C] [D] [E] [F] [G] [H] [I] [J] [K] [L] [M] [N] [O] [P] [Q] [R] [S] [T] [U] [V] [W] [X] [Y] [Z]
h2
The ratio between genetic variance and phenotypic variance used by
plant breeders in selecting for yield, resistance or other characteristics.
Habgood name
A number representing a combination of genes in the mathematical system
of nomenclature devised by Habgood (1970).
Habitat
A place with a particular kind of environment where plants and animals
live.
Habitat, duration stability
The length of time the particular habitat type remains in a particular
geographical location.
Habitat, temporal variability
The extent to which the carrying capacity (k) of a habitat varies during
the time that site is tenable by the organism (i.e. temporal heterogeneity).
Habitat, spatial heterogeneity
Spatial continuity versus patchiness.
Haemagglutination
Agglutination of red blood corpuscles.
Haemaglobinura
A condition in which the urine contains haemoglobin and is therefore
stained red.
Haematinic
A medicine which increases the haemoglobin content of the red cells
in the blood.
Haematuria
The presence of blood in the urine.
Half-reaction
A reduction or oxidation written alone. Two half-reactions may be
combined to form a complete electrochemical reaction.
Half saturation level
The level of some independent variable at which some process rate is
reduced to half its maximum relative to that independent variable. It
is applied to such processes as the effect of nutrient availability on
phytoplankton nutrient uptake or the effect of prey density on predator
feeding rate.
Half-sib
Having one parent in common.
Haller's organ
Depression on the first tarsi of ticks; functions as olfactory and
humidity receptor.
Halophile
Organism requiring salt for growth.
An organism that grows best at high concentrations of salts.
Halteres
Short-knobbed appendages of true flies; modified hind wings.
Vestigial wing on the metathorax of a fly of the order Diptera; necessary
for balance during flight.
Halzoun
Disease resulting from blockage of the nasopharynx by a parasite.
Hamuli
Large hooks on the opisthaptor of a monogenetic trematode, referred
to as anchors by American authors.
Handling time
The act of quelling, killing and eating a prey, and then cleaning and
resting by a predator are collectively known as the handling time.
Haploid
Having one set of chromosomes in a cell or an individual. Haploidy
is a characteristic of sex and germ cells.
Haploid parthenogenesis
The situation in which the unfertilised egg hatches and develops normally
to produce a viable male adult whose cells contain only the haploid number
of chromosomes.
Haptenes
A small, separable non-protein part of certain antigen molecules which
carries the chemical group that combines with the antibody. The injection
of a hapten into an animal does induce antibody formation.
Hardpan
A horizon of the soil that is hardened or cemented.
Hard water
Water which contains certain minerals, usually calcium and magnesium
sulphate, chlorides or carbonates in solution to the extent that a curd
or precipitate rather than a lather occurs when soap is added. Very hard
water may cause objectionable precipitates in some herbicidal sprays.
Harm
(1) A loss to a species or individual consequent on damage.
(2) A function of the concentration to which the organism is exposed
and of the time of exposure.
Harmfulness
Direct loss per plant or per part of plant.
Harmful organisms
Comprehensive term to include vertebrate or invertebrate pests, pathogen
and weeds.
Harvest aid chemical
Material applied to a plant before harvest to facilitate harvesting
by reducing plant foliage.
Harvest intervals
The period between the last application of a pesticide to a crop and
the harvest, usually defined by law.
Hatching factor
A material produced by the roots of certain plants that is believed
to increase the hatching of eggs of certain nematodes.
Haulm
Above-ground parts of a plant (stem and leaves), especially of potatoes.
Haulm killer
Chemical for killing off potato plant tops to facilitate harvest.
Haustorium
Absorbing organ of certain parasites. A projection of fungal hyphae
into host cells which acts as a penetration and absorbing organ.
Hay
The cured dry forage of the finer-stemmed crops e.g. grass.
Hazard
The probability that a substance will cause harm under conditions of
exposure.
Hazard identification
The identification of the chemical of concern, its adverse effects,
target populations and conditions of exposure.
Hazard prediction/identification
The process of recognising a potential risk, involving both toxicity
assessment and exposure assessment. Toxicity assessment determines the
nature and extent of adverse health effects that the chemical in question
can exert related to dose. Exposure assessment characterises exposed populations
and where possible estimates exposure levels or doses incurred. The major
objective of this process is the integration of toxicity dose responses
and exposure data to provide dose-response relationships.
Head
A dense cluster of sessile, or nearly sessile, flowers on a very short
axis or receptacle, as in alsike clover and sunflower.
Head rice
The kernels of milled rice which are _ kernel size or larger.
Head yield
The amount of head rice obtained when paddy is milled. It is the total
rice less the brokens.
Heat
Oestrous, season, or bulling. The time when a female is receptive
to the bull. The phenomenon precedes ovulation when the ripe egg is shed
from the ovary and passes into the uterus.
Heath
Low vegetation with shrubs.
Heat test
Iberia heat-tolerance test. A measure of adaptation to high temperatures
as shown by the least rise in body temperature. The rectal temperature
in animals is measured in degrees Fahrenheit at 10 am. and 3 pm. on each
of three days when the air is still and in clear sunshine; the ambient
temperature should be 85-90°F. These six rectal temperatures are averaged.
Adaptability to heat = 100-10 (average rectal temperature - 101.0).
Heat therapy
High-temperature treatment for control of virus and other diseases.
Heel fly
Fly maggot of the family Hypodermatidae. Also called a warble.
Heifer
A bovine female from birth (heifer calf) to calving herself. Sometimes
used until she calves a second time but this is a confusion best avoided,
e.g. second-calf heifer.
Heliotropic
Turning toward the sun.
Helminth
A member of the large group of primitive worms including nematodes
and the worms parasitic in animal gut and tissues.
Hemagglutination
Agglutination of red blood cells.
Hemelytra
The top pair of wings of true bugs, which have their basal ends thickened
and their distal ends membranous.
Hemelytron
The partly thickened forewing of the order Heteroptera.
Hemicellulose
A group of polysaccharides resembling cellulose and occurring in the
cell wall.
Hemimetabolous
Insects having a simple metamorphosis, like that in the Orthoptera,
Heteroptera and Homoptera.
Hemimetabolous metamorphosis
Gradual metamorphosis in insects, in which the nymphs are generally
similar in body form to the adults and become more like the adults with
each instar.
Hemiparasite
An organism that is usually a parasite, but capable of leading a saprophytic
life.
Hemocoel
Main body cavity of arthropods, the embryonic development of which
differs from that of a true coelom but which includes a vestige of a true
coelom.
Hemoglobinuria
Bloody urine.
Hemolymph
Fluid within the hemocoel of arthropods; also, the pseudocoelomic fluid
of nematodes.
Hemolysis
Lysis of red blood cells.
Hepato
Pertaining to the liver.
Hepatosplenomegaly
Swollen liver and spleen.
Heptaotoxic
Harmful to the liver.
Hepatoxin
A substance that causes damage to the liver.
Herb
Any vascular plant which is not woody.
Herbaceous
Referring to plants with soft stems (not woody), such as annuals, biennials
and perennials that normally die back to the ground in the winter.
Herbage
Herbs, collectively, especially the aerial portion.
Low growing plants used for fodder.
Herbicide
Any substance or mixture of substances intended for preventing, destroying
or controlling any weed, including any algae or aquatic weed.
Herbicide chronicity
The concept where long-term exposure to low concentrations of a herbicide
is as, or more phytotoxic than short exposure to a high concentration of
herbicide.
Herbicide, hormone-type
Herbicide in which the active ingredient has growth-regulating properties.
Herbicide, residual
Herbicide showing persistent effect when applied to soil.
Herbicide, selective
Herbicide possessing differential toxicity to certain weeds and crop
plants.
Herbicide, total
Herbicide affecting all plants.
Herbivores
Organism that feeds on plant material, contrast with carnivore.
Heritability
That portion of the observed variance in a progeny that is inherited.
Hermaphrodism
Possession of gonads of both sexes by a single (monoecious) individual.
Hermaphrodite
Bisexual. In a flowering plant, having both stamens and carpels in
the same flower; in an animal producing both male and female gametes.
Hessian
Cloth made from hemp or jute.
Heterocaryosis
A condition in which two or more genetically different nuclei occur
in one cell.
Heterocyst
Specialised cell in filamentous cyanobacteria frequently associated
with nitrogen fixation.
Heteroduplex
A double-stranded DNA in which one strand is from one source and the
other strand from another, usually related, source.
Heteroecious
With an annual alternation between primary and secondary hosts (usually
unrelated) (opposite of autoecious). Pertaining especially to rust fungi.
Heterofermentation
Fermentation of glucose or other sugar to a mixture of products.
Heterogeneous
Differing in kind; unlike qualities, different characteristics; dissimilar;
mixed.
Heterogonic life cycle
Life cycle involving alterations of parasitic and free-living organisms.
Heterokaryon
A cell which contains at least two nuclei from different cell types.
Heterokaryosis
The condition in which a mycelium contains two genetically different
nuclei per cell.
Heterologous antigen
An antigen reacting with an antibody other than the one it induced.
Heterologous reaction
A serological reaction in which an anti-serum is reacted against an
antigen other than the one used in its preparation.
Heterophile reaction
Antigen-antibody reaction, in which the antibody was not specifically
elicited by the antigen to which it binds.
Heterosis
Increased growth, vigour or yield frequently shown in the F1 generation
of a cross. Hybrid vigour.
Heterothallic
The condition in which fungi produce compatible male and female gametes
on physiologically distinct mycelia.
Heterotopy
Hyperplastic symptom in which an organ develops in a position other
than its normal one (e.g. the development of 'ears' in the tassels of corn
plants).
Heterotroph
Organisms which obtain energy and materials by eating other organisms;
contrast with autotroph, a consumer as opposed to a producer.
Heterotrophic
Refers to organisms that are dependent upon outside sources for growth,
being incapable of synthesising required organic materials from inorganic
sources. Heterotrophs obtain their food from other organisms, living or
dead.
Heteroxenous
Living within more than one host during a parasite's life.
Heterozygous
Having a dominant and a recessive gene of a pair in the same cell or
organism. An organism can be heterozygous for one or several genes.
Hexacanth
Oncosphere; a six-hooked larva hatching from the egg of a eucestode.
Hexose monophosphate pathway (HMP)
Reaction sequence used primarily to synthesise pentosese from hexoses.
Hibernation
Period of dormancy in winter or cool season during which metabolism
decreases; in mammals temperature drops close to that of surroundings.
Hierarchy
A structural relationship in which each unit consists of two or more
sub-units, the latter being similarly sub-divided.
Highly flammable liquid
A liquid having a flash point of less than 21°C as determined by
a closed cup method.
High-volume
See spray vii.
Hilum
The scar on a seed which marks the point of its attachment to the pod
or seed stalk.
Hirsuite
Having long stiff hairs e.g. hirsute leaves.
Histochemistry
The microscopic study of the chemical characteristics of tissues, through
the use of substances (dyes etc.) producing identifying chemical reactions.
Histology
The study of the anatomy of tissues and their cellular structure.
Histopathological
Pertaining to histopathology, i.e. the study of the minute structure
of diseased tissue, generally by staining and examination under the microscope.
Histopathology
A study of abnormal microscopic changes in the tissue structure of
an organism.
Historical analogy
A method for forecasting the sales of a newly introduced product (or
service) that uses the sales history of some previously introduced product
as a guide.
Historic cost accounting
The recording of transactions at the actual cost incurred at the time
of purchase irrespective of the item's current value.
Histozoic
Dwelling with the tissues of a host.
Holdfast
An adhesive material at a localised position on a cell, enabling the
cell to attach to a surface.
Holding capacity
The amount of paddy in a continuous-flow dryer at one time; however
it is not necessarily the drying capacity nor the throughput capacity of
the dryer e.g. a continuous-flow dryer may have a 6 ton holding capacity,
a 12 ton through put capacity and an average drying capacity of 2% pass
(Wimberley, 1983).
Holidic
Pertaining to a medium (used for growing organisms) whose intended
constituents, other than purified inert materials, have exactly known chemical
structure before the medium is compounded.
Hollow cone
Spray jet for pesticide application having a core of air breaking to
give drops in an annular pattern.
Hollow fibres
A formulation for controlled release of chemicals based on a reservoir
of active chemical held in the bore of the fibre and released by diffusion
through the air layer above the chemical. Other systems relevant to pest
control include foams and impregnated porous plastics e.g. polyvinyl chloride
(PVC).
Holoblastic cleavage
Each nuclear division in an early embryo that is accompanied or closely
followed by complete cytokinesis, the nuclei being separated by cell membranes.
Holocarpic reproduction
In fungi, reproduction in which the entire fungal body (thallus) is
segmented into spores.
Holocyclic
Having an annual sexual phase in which parthenogenesis is interrupted
by the production of male and female sexual morphs (opposite of anholocyclic).
Holometobola
Insects which undergo a complete metamorphosis i.e. insects with a
larva, pupa and adult.
Holonecrosis
The condition of being dead.
Holophytic nutrition
Formation of carbohydrates by chloroplasts.
Holozoic nutrition
Feeding by active ingestion of organisms or particles.
Homeostasis
Maintenance of constancy or a high degree of uniformity in functions
of an organism or interactions of individuals in a population or community
under changing conditions, because of the capabilities of organisms to
make adjustments.
Hoemothermic
Pertaining to 'warm-blooded' animals that regulate their body temperature;
contrast with poikilothermic.
Homeotherms
'Warm-blooded' animals, whose body temperature is maintained above
that of usual surroundings.
Homofermentation
Fermentation of glucose or other sugar leading to virtually a single
product, lactic acid.
Homogeneous
Uniform as to kind; showing no variability.
Homogonic life cycle
Life cycle in which all generations are parasitic or all are free living;
there is no (or little) alteration of the two.
Homologous antigen
An antigen reacting with the antibody it had induced.
Homologous chromosomes
Chromosomes which pair at the first division in meiosis; each member
of a pair has a corresponding sequence of gene loci and is derived from
a different parent.
Homologous reaction
A serological reaction in which an anti-serum is reacted against the
antigen used for its preparation.
Homology
Similarity in the sequence of monomers which make up different polymers;
e.g. similarity in the base sequence of two different DNA or RNA molecules.
Homothallic
The condition in which sexual reproduction can only occur within the
fungal mycelium; compare with heterothallic.
Homothetogenic fission
Miotic fission across the rows of cilia of a protozoan.
Homozygous
Of a cell or organism having both genes of a pair dominant or recessive
an organism may be homozygous for one, several or all genes.
Homozygote
An individual the parent of which contributed to it a similar number
of any given number pair of genes and whose germ cells are all alike in
regard to the genes for that character.
Honey-dew
Liquid with high sugar content discharged from the anus of some insects
of the order Homoptera.
Hood
Dorsal wall of the camerostome that extends over the capitulum.
Hop blower
Rotary-blower duster for hops.
Horizon (soil)
A layer of soil, roughly parallel to the surface of the soil, with
distinct characteristics which were produced by soil-forming processes.
Horizontal resistance
A resistance trait that does not involve a gene-for-gene relationship,
i.e. any resistance that is not vertical resistance.
Horizontal transmission
Transmission between plants that are contemporaneous with each other.
Hormogonium
A motile segment of a filamentous cyanobacteria, usually involved in
dispersal.
Hormone
A chemical agent that controls various physiological processes within
an organism e.g. adrenaline stimulates the heart; auxins and cytokinins
in plants stimulate cell proliferation and growth.
Hormone spray
See spray viii.
Hornworm
A caterpillar with dorsal spine or horn on the last abdominal segment
- larvae of the family Sphingidae.
Host
Organism that furnishes food, shelter or other benefits to another
organism of a different species.
Host plant resistance
A method of pest control in which resistant, tolerant or unattractive
host organisms are used. The inherited qualities of resistance influence
the extent of pest damage.
Host range
The various kinds of host plants that may be attacked by a parasite.
Host specificity
The degree of restriction of the number of different plants or animals
species that can serve as a food source for herbivorous or carnivorous
species.
Hot fogging concentrate
A formulation suitable for application by hot fogging equipment.
Hull or husk
The lemma and palea attached to the caryopsis after threshing. To
remove hulls from seeds.
Human resource accounting
Attempts by accountants to place a value on human assets in an enterprise.
Humectant
Material added to a spray to delay evaporation of the water carrier.
Humic
Moist.
Humid climate
A climate with sufficient precipitation to support forest vegetation:
50 cms or more in cool regions; up to 152 cms in hot regions.
Humidity
The condition of the atmosphere in respect of its water vapour content.
The word 'humidity' used alone generally signifies relative humidity,
but various other measures are employed such as humidity mixing ratio,
vapour concentration, vapour pressure, specific humidity, dew point etc.
Humoral immune response
Binding of antigen with soluble antibody in blood serum; also, the
entire process by which the body responds to an antigen by producing antibody
to that antigen.
Humoral immunity
An immune response involving the activities of antibodies.
Humus
The well-decomposed, more or less stable part of the organic matter
of the soil.
Husking or dehusking
The process of removing the husk from the hulling or shelling grain
during milling.
Hyaline
Transparent, colourless.
Hyalommine toxin
Toxin derived from a tick of the genus Hyalomma.
Hybrid
The first generation offspring of a sexual cross fertilisation between
two individuals differing in one or more genes i.e. a heterozygote.
Hybridoma
The fusion of a malignant cell with a single B-lymphocyte to produce
a malignant lymphocyte producing monoclonal antibody.
Hybrid vigour
see Heterosis.
Hybridisation
The process by which organisms of unlike hereditary constitution are
crossed to produce F1 progeny with genes for the characteristics of both
parents i.e. cross breeding.
Hybridoma
An antibody-secreting cell line which is immortal. A hybrid cell resulting
from the fusion of a tumour (cancer) cell and a normal cell such as a lymphocyte
from the spleen. The fused cells can be cloned and, being derived from
a simple spleen cell, will secrete a pure antibody.
Hydatid cyst
Metacestode of the cyclophyllidean cestode genus Echinococcus, with
many protoscolices, some budding inside secondary brood cysts.
Hydatid sand
Free protoscolices forming sediment in a hydatid cyst.
Hydathodes
Structures with one or more openings that discharge water from the
interior of the leaf to its surface.
Hydration
The addition of water.
Hydraulic sprayer
See sprayer iii.
A machine which applies pesticides by using water at high pressure
and volume to deliver the pesticide to the target. Same as high pressure
sprayer.
Hydrocarbon
Compounds consisting essentially of carbon and hydrogen. The important
classes of hydrocarbons are paraffins, naphthaenes, olefins and aromatics.
Ordinary commercial products derived from crude oil are normally made
up of these four classes of compounds in varying proportions.
Hydrolysis
Chemical process of breakdown or decomposition involving a splitting
of the molecule and addition of water molecule. e.g. during pesticide breakdown.
Hydrolytic
Causing hydrolosis or the reaction between a compound and the hydrogen
and hydroxyl ions.
Hydropericardium
A condition in which the pericardial sac (the fibrous tissue sac in
which the heart is contained) is filled with an excess of fluid.
Hydrophilic
Describes the molecule or group of atoms having, usually because of
hydrogen bonding, a strong affinity for water i.e. water attracting.
Hydrophilic/lipophilic balance
The ratio of the water/oil affinities of an emulsifier.
Hydrophobic
Opposite of hydrophilic. Water repelling.
Hydrophyte
Plant that grows wholly or partly immersed in water; compare with xerophyte
and mesophyte.
Hydroponics
The growing of plants in aqueous chemical solutions.
Hydrosis
Necrotic symptom of disease characterised by water-soaking of tissues.
Hydrothorax
A condition in which the thoracic cavity is filled with excess fluid.
Hygroscopic
Having a marked ability to accelerate the condensation of water vapour.
Hymenium
A fertile layer of regularly arranged asci or basidia in fungal fruiting
bodies.
Hyperaemia
Excess of blood, usually to a tissue or organ.
Hyperaesthesia
Excessive sensitiveness of the skin, usually in the area of a diseased
tissue.
Hyperaminoacidemia
Presence of amino acids in the blood or hemolymph in excess of the
normal amount.
Hypergeometric probability distribution
Appropriate when sampling from a finite population of N elements of
which k are identified as 'successes' and (N - k) are 'failures'. Then
p(x) gives the probability of observing x successes in a sample of n selected
from the population.
Hyperimmune
Having a very high antibody titre.
Hypermetamorphosis
A type of complete metamorphosis in insects in which the different
larval instars represent two or more different types of larvae.
Hyperparasite
A parasite whose host is another parasite.
Hyperplasia
A malformation caused by an increased number of functional units of
an organ (organelles, cells, tissues), excluding tumour formation, whereby
the bulk of the organ is increased in response to increased functional
demands.
Hyperpolysis
Detachment of a tapeworm proglottid while still juvenile, before eggs
are formed.
Hypermetamorphosis
Type of metamorphic development in which different larval instars have
markedly dissimilar body forms.
Hyperparasitism
Condition in which an organism is a parasite of another parasite.
Hypersensitive
Usually used to characterise a host whose initial reactions to infection
are so strong as to limit further development of the invading parasite.
Hypersensitive reaction
A rapid response of a host to a parasite in which death of a portion
or all of the host ensues.
Hypersensitivity
Excessive sensitivity of plant tissues to certain pathogens. Affected
cells are killed quickly, blocking the advance of obligate parasites.
Also an immune reaction, usually harmful to the animal, caused either by
antigen-antibody reactions or cellular-immune processes.
Hypertrophy
Abnormal increase in size (weight) and functional capacity of an organ
or tissue, without an increase in the number of structural units upon which
their functions depend; hypertrophy is usually stimulated by increased
functional demands.
Hypha (pl. hyphae)
One of the simplest branched filaments of the mycelium of a fungus
that is composed of one or more cylindrical cells and that increases in
length by growth at its tip. New hyphae arise as lateral branches.
Hyphopodium
A short mycelial branch.
Hypocholesterolaemia
A lowering of the cholesterol content of the blood.
Hypocotyl
The stem of the embryo or young seedling below the cotyledons.
Hypodermis
The cellular layer beneath the cuticle of a nematode.
Hypolimnion
The lower region of a stratified lake, not subject to wind mixing during
at least part of the year. Below the thermocline.
Hyponasty
More rapid growth of the lower side of an organ (e.g. a petiole) than of the upper side.
Hypopharynx
Tongue-like lobe arising from floor of mouth in insects; variously
modified for feeding in many groups.
Hypoplasia
A malformation caused by the underdevelopment of cells, tissues or
organs. A hypoplastic organ or tissue is one that never reaches normal
size; sometimes used to indicate an atrophy caused by the destruction of
some of the elements (e.g. cells) rather than a general reduction in size.
Hypostatic gene
A gene whose properties are suppressed in the presence of another (epistatic)
gene.
Hypostome
Portion of the mouthparts of acarines; composed of fused coxae of pedipalps.
Hypotheca
Inner half wall of a diatom cell.
Hypotrophy
Underdevelopment of a tissue or plant due to abnormally reduced cell
enlargement.
Hypovirulence
The phenomenon by which a strain of a pathogen is less virulent than
normal. In some fungi infection with dsRNA is thought to be responsible.
Hysterosoma
Combination of the metapodosoma and opisthosoma of the body of a tick
or mite.
Hyterozygous
An organism that for any given character possesses different genes
inherited from the male and female parents. Heterozygous plants do not
breed true.
Hythergraph
A polygonal diagram resulting from plotting temperature means against
rainfall.
