## Part 542.1 Terms Commonly Used in Plant Materials Work (Glossary)

The following list of terms, although not complete, defines some terms
commonly used by plant scientists.

**9 million numbers** - NRCS numbers used to identify plant accessions;
i.e., 9056783

**900 numbers** - NRCS numbers used to identify plant accessions, now
referred to as 9 million numbers; i.e., 9056783

**Accession** - Plant material (plant, seed, or vegetative part)
collected and assigned a number to maintain its identity during
evaluation, increase, and storage.

**Acid Equivalent** - The theoretical yield of parent acid from an
active ingredient.

**Active Ingredient** - The chemical compound in a product that is
responsible for the herbicidal (or other chemical) affect.

**Advanced Evaluation** - The more intensive testing of plants that have
been selected as being superior in one or more attributes to the initial
evaluation.

**Aggressiveness** - Seedling vigor related to ease of establishment.
Also capacity of well-established plants to compete with or outcompete
associated grasses, legumes, or woodies.

**Alien Species** - A species introduced and occurring in locations
beyond its known historical range. This includes introductions from
other continents, bioregions, and also those not native to the local
geographic region. Executive Order (E.O.), Invasive Species, February 3,
1999, more narrowly defines an alien species and ties the definition to
an occurrence outside a native.

**Allele** - One member of a pair or series of genes occupying a
specific position (locus) in a specific chromosome; one of the
alternative forms of a gene. Normally an individual has only two alleles
for any trait ‑ one gene derived from its male parent, the other from
its female parent.

**Allopolyploid** - A polyploid containing genetically different sets of
chromosomes; for example, sets from two or more species.

**Amphidiploid** - A polyploid whose chromosome compliment is made up of
the entire somatic complements of two species.

**Aneuploid** - An organism whose somatic number is not an even multiple
of the haploid number.

**Annual** - A plant that completes its life cycle from seed in a single
year or growing season.

**Apomixis** - Reproduction in which sexual organs or related structures
take part but fertilization does not occur, so that the resulting seed
is vegetatively reproduced. Only a single parent contributes genes to
the offspring.

**Apparent Trend** - An interpretation of trend based on a single
observation. Apparent trend is described in the same terms as measured
trend except that when no trend is apparent it shall be described as
\"not apparent\". See "Trend".

**Assembly** - A systematic collection of plants (seed or vegetative
material) of one or more species to be evaluated for a planned purpose.

**Autopolyploid** - A polyploid arising through multiplication of the
complete haploid set of one species.

**Backcross** - The crossing of a hybrid with either of its parents. In
genetics, the crossing of a heterozygote with a homozygous recessive.

**Band Applications** - An application to a continuous restricted area
such as in or along a crop row, rather than over the entire field area.

**Bare-root** - A plant harvested from a field without any soil on its
roots.

**Basal Treatment** - Herbicide applied to the stems of woody plants at
or just above the ground.

**Biennial** - A plant that completes its life cycle in 2 years. The
first year it produces leaves and stores food. The second year it
produces fruits and seed.

**Biodiversity** - The total variability within and among species of
living organisms and the ecological complexes that they inhabit.
Biodiversity has three levels - ecosystem, species, and genetic
diversity - reflected in the number of different species, the different
combination of species, and the different combinations of genes within
each species.

**Biotype** - A group of individuals within a population occurring in
nature, all with essentially the same genetic constitution. A species
usually consists of many biotypes. See also "ecotype".

**Blend** - A mixture of seed of known proportions of two or more lots
or variation of the same species.

**Blind Cultivation** - Cultivating before a seeded or planted crop
emerges.

**Botanical Variety** - The botanical nomenclature division consisting
of more or less recognizable entities within species that are not
genetically isolated from each other, below the level of subspecies, and
is indicated by the abbreviation "var." in the scientific name; Usage:
the abbreviation in roman type; the name in italics; no capitals. See
also "variety".

**Breeder Seed** - Seed or vegetative propagating material which is
directly controlled by the originating or, in some cases, the sponsoring
plant breeder, institution, or firm, and which supplies the source for
initial and recurring increase of foundation seed. See also "seed
certification classes".

**Breeder\'s Rights** - The assurance that the owner of a crop variety
has exclusive control over the increase, distribution, and merchandising
of a variety. The protection may be afforded by legislation and
regulatory control by agreement among individuals concerned, or by
biological factors inherent in the variety. The breeder is assured that
his/her authorization must be obtained before the variety can be
reproduced or sold by anyone else. See "Plant Variety Protection Act.\"

**Breeding System** - A system of use to select or modify a plant to
yield new progeny with desired characteristics.

**Business Plan -** A document to indicate how the PMC resources are to
be used and action items to be completed. It should be brief, flexible,
realistic, and open-ended. It should be consistent with NRCS guidelines.

**C-3 Plants** - Species having a photosynthetic pathway which results
in 3-carbon compounds as initial products of photosynthesis. Includes
most legumes, forbs and cool season grasses, as well as most trees and
shrubs. Usually significantly less efficient users of soil and water
nitrogen than are C-4 plants. Optimum temperature for photosynthesis and
growth is 18 to 25° Celsius (64 to 77° Fahrenheit). See also
"photosynthesis".

**C-4 Plants** - Species having a photosynthetic pathway which results
in 4-carbon compounds as initial products of photosynthesis. Includes
most warm season grasses, tropical grasses, a few forbs, and at least
one shrub. Usually significantly more efficient users of soil nitrogen
and water than are C-3 plants. Total biomass production is generally
substantially greater than plants with other photosynthetic pathways.
Optimum temperature for photosynthesis and growth is in the range of 27
to 35° Celsius (84 to 100° Fahrenheit). See also "photosynthesis".

**CAM Plants** - Abbr. for "Crassulacean Acid Metabolism". Species whose
photosynthetic pathway primarily involves fixation of carbon dioxide
during the dark period. Includes desert succulent plants such as cactus.
Under good moisture and temperature conditions, carbon fixation may
occur in the light via either C-3 or C-4 pathways. Generally the least
productive of the three photosynthetic pathways. See also
"photosynthesis".

**Carrier** - A liquid or solid material added to a chemical compound or
seed to facilitate its application in the field.

**Center of Diversity** - The geographic region in which the greatest
variability of a species occurs. A primary center of diversity is the
region of true origin and secondary centers of diversity are regions of
subsequent spread of a species.

**Center of Origin** - The geographic region containing a concentration
of genetic diversity of one or more species; also called a gene center.

**Certified Seed** - The progeny of breeder, foundation, or registered
seed that is so handled as to maintain satisfactory genetic identity and
purity and that has been approved and certified by the certifying
agency. Certified tree seed is defined as seed from trees of proven
genetic superiority, as defined by the certifying agency, produced so as
to assure genetic identity. See also "seed certification classes".

**Chasmogamous** -- Plant type in which the perianth of flowers opens
for pollination to occur. See also "cleistogamous".

**Cleistogamous** -- plant type in which flowers self-pollinate inside
the closed buds.

**Climax** -- (1) The final or stable biotic community in a successional
series that is self‑perpetuating and in dynamic equilibrium with the
physical habitat; (2) the assumed end in succession. See also "historic
climax plant community".

**Cline** -- a gradual morphological or physiological change in a group
of related organisms across their range, usually associated with
environmental or geographic transition.

**Clone** - A group of genetically identical plants produced by
vegetatively propagating a single plant over one or more vegetative
generations.

**Combining Ability** -- In general, the average performance of a strain
in a series of crosses. More specifically, deviation from performance
predicted on the basis of general combining ability.

**Commercial Seed** - Seed produced by commercial industry; may or mat
not be recognized improved varieties of seed.

**Common Seed** - Non-certified seed. Such seed may be a named variety
but are not grown under the certification program. Also a term applied
to seed that cannot be identified as to variety; sometimes used to
denote local strains resulting from natural selection.

**Community** - An assemblage of one or more populations of plants
and/or animals in a common spatial arrangement.

**Community (Plant Community)** - An assemblage of plants occurring
together at any point in time, while denoting no particular ecological
status. A unit of vegetation.

**Community Type** - An aggregation of all plant communities
distinguished by floristic and structural similarities in both overstory
and undergrowth layers. A unit of vegetation within a classification.

**Companion Crop** - A crop sown along with another crop; used
particularly for small grain with which a forage crop is sown. Companion
crop is preferred to the term "nurse crop."

**Compatible** - Compounds or formulations that can be mixed and applied
together without undesirably altering their separate effects. This term
can be applied also to species mixtures.

**Composite** - The combining of genetic material from several sources.
This is one of the alternatives of the mass selection technique and
should not be confused with a polycross. See also "mass selection" and
"polycross".

**Concentration** - The amount of active ingredient or acid equivalent
in a given volume of liquid or in a given weight of dry material.

**Conservation Field Trial** - Is identified in the NRCS General Manual
450-403 as a tool for evaluating new technology, species, or plant
releases that address local soil and water resource problems; type of
study used by many disciplines; in the PM program may be used to develop
new technology, evaluate releases, and promote PM products; typically
coordinated by the PMS; qualitative or quantitative data may be
collected.

**Contact Herbicide** - A herbicide that kills a plant primarily by
contact with plant tissue rather than by translocation.

**Containerized Stock** - Plant materials grown in containers.

**Cool-season Plant** - A plant that makes its major growth during the
cool part of the year, mainly in spring but in some localities in the
fall or winter.

**Cooperative Agreement** - A written document evidencing the intent of
two or more parties to cooperate in an undertaking that will result in
mutual benefit to the parties concerned. The parties work jointly in the
undertaking \-- not each working within its own sphere of work and
authority as under a memorandum of understanding relationship. The
cooperative agreement is a fiscal document, and the period of time
covered must not exceed the period for which funds are available for
obligation.

**Cover Crop --** Close-growing crop grown primarily for the purpose of
protecting and improving soil between periods of regular crop
production.

**Cover Type** - The existing vegetation of an area.

**Cross Pollination** - The transfer of pollen from one flower
(artificially or naturally) to the stigma of another; may occur on the
same plants or on different plants, depending on the species and other
conditions.

**Crossing-Over** - The exchange of corresponding segments between
chromatids of homologous chromosomes during meiotic prophase. The
genetic consequence is the recombination of linked genes.

**Cultivar** - The international term cultivar denotes an assemblage of
cultivated plants that is clearly distinguished by any characters
(morphological, physiological, cytological, chemical, or others) and
when reproduced (sexually or asexually), retains its distinguishing
characters. The term is derived from "cultivated variety", or their
etymological equivalents in other languages. For cultivated plants**,**
the term cultivar is the equivalent of a botanical variety, in
accordance with the International Code of Nomenclature of Cultivated
Plants 1980. Usage: cultivar names are not italicized, and are indicated
by single quotes at first use, or the word cultivar (but not both). The
abbreviation cv. is properly used only with a binomial name: Genus
species cv. cultivar name. Omit the abbreviation if single quotes are
used: Genus species 'cultivar name'.

**Cultural Evaluation** - Studies designed to obtain information
regarding establishment, management and production of plant materials.
They may be conducted on or off the center at any stage of the
evaluation process.

**Defoliant** - A compound that causes the leaves or foliage to drop
from a plant.

**Demonstration Plantings** - A planting used primarily to promote use
and acceptance of new technology or releases; no evaluations are done
and no data is collected.

**Desiccant** - A compound that promotes dehydration or removal of
moisture from plant tissue.

**Desired Plant Community** - A plant community which produces the kind,
proportion, and amount of vegetation necessary for meeting or exceeding
the minimum quality criteria for the soil, water, air, plant and animal
resources, and the land use plan/activity plan objectives established
for an ecological site(s). The desired plant community must be
consistent with the site\'s capability to produce the desired vegetation
through management, land treatment, or a combination of the two.

**Diluent** - Any liquid or solid material serving to dilute an active
ingredient in the preparation of a formulation.

**Dioecious** - Having staminate and pistillate flowers occurring on
different plants, that is, having distinct male and female plants (e.g.
buffalograss).

**Diploid** - Having two chromosomes of each kind. Having the basic
chromosome number doubled.

**Direct Application** - Method of applying chemicals or fertilizers
directly to a restricted area, such as a row or a bed at base of plants.

**Diversity** - The distribution and abundance of different plants and
animal communities within an area. Also a measure of the number of
species and their relative abundance within a given association of
organisms. Areas of high diversity are characterized by a great variety
of species; usually relatively few individuals represent any one
species. Areas with low diversity are characterized by a few species;
often relatively large numbers of individuals represent each species.

**Dormancy** - An internal condition of the chemistry or stage of
development of a viable seed that prevents its germination, although
temperature and moisture are adequate for growth.

**Dormant Seeding** - Planting seed during late fall or early winter
after temperatures become too low so that seed germination occurs the
following spring.

**Ecesis** - Establishment and development of a plant in the plant
community.

**Ecocline** - Series of biotypes within a species that shows a genetic
gradient correlated with a gradual environmental gradient.

**Ecological Niche** - Role of an organism in an ecological system.
Includes the physical space in a habitat occupied by an organism; its
functional role in the community (e.g., its trophic position); and its
position in environmental gradients of temperature, moisture, pH, soil,
and other conditions of existence.

**Ecological Optimum** - The most favorable conditions in the
environment for the growth and reproduction of an organism.

**Ecological Race** - Group of local populations within a species in
which individuals have similar environmental tolerances. Wide-ranging
species may consist of many ecological races.

**Ecological Response Unit** - A unit of land that is homogeneous in
character such that similar units will respond in the same way to
disturbance or manipulation. Syn. ecological site, ecological type.

**Ecological Site** - A kind of land with a specific potential natural
community and specific physical site characteristics, differing from
other kinds of land in ability to produce vegetation and to respond to
management. Syn. Ecological type, ecological response unit.

**Ecological Status** - (1) The present state of vegetation and soil
protection of an ecological site in relation to the potential natural
community for the site. Vegetation status is the expression of the
relative degree of which the kinds, proportions, and amounts of plants
in a community resemble that of the potential natural community. If
classes or ratings are used, they should be described in ecological
rather than utilization terms. For example, some agencies are utilizing
four classes of ecological status ratings (early seral, midseral,
late-seral, potential natural community) of vegetation corresponding to
0‑25%, 26‑50%, 51‑75%, and 76-100% of the potential natural community
standard. Soil status is a measure of present vegetation and litter
cover relative to the amount of cover needed on the site to prevent
accelerated erosion. This term is not used by all agencies. (2) The
present state of vegetation and soil protection of an ecological site in
relation to the historic climax plant community for the site. Vegetation
status is the expression of the relative degree of which the kinds,
proportions, and amounts of plants in a community resemble that of the
historic climax plant community. If classes or ratings are used, they
should be described in ecological rather than utilization terms.

**Ecological System** - See "ecosystem".

**Ecological Type** - A land classification category which is more
specific than a phase of a habitat type. Ecological types are commonly
used to differentiate habitat phases into categories of land which
differ in their ability to produce vegetation or their response to
management. Syn. ecological response unit, ecological site.

**Ecophene** - Plants differing in appearance, especially in the size of
vegetative parts, numbers of stems, erectness, and reproductive vigor
but belonging to essentially homogeneous genetic stock. Their
distinctness is due entirely to environmental influences, for when
different ecophenes are transplanted into the same habitat these
differences disappear.

**Ecosystem** - Energy-driven complex of one or more organisms and their
environment. Organisms together with their abiotic environment, forming
an interacting system, inhabiting an identifiable space. The whole
system, in the sense of physics, including not only the organism
complex, but also the whole complex of physical factors forming what we
call the environment. The complex of living and nonliving components in
a specified location that comprise a stable system in which the exchange
of material follows a circular path such as a biome. A community of
organisms and the environment in which they live. A system of ecological
relationships in a local environment, including relationships between
organisms, and between the organisms and the environment itself. Syn.:
ecological system.

**Ecotone** - Transitional zone between two vegetational types or
vegetational regions. A transition area of vegetation between two
communities, having characteristics of both kinds of neighboring
vegetation as well as characteristics of its own. Varies width depending
on site and climatic factors. A transition line or strip of vegetation
between two communities, having characteristics of both kinds of
neighboring vegetation as well as characteristics of own.

**Ecotype** - (1) A population of plants that has become genetically
differentiated in response to the conditions of a particular habitat.
The plants may vary in growth habit, maturity, and other characteristics
such as pubescence and flower color. Sometimes referred to as a
geographical race. (2) A transition area of vegetation between two
communities, having characteristics of both kinds of neighboring
vegetation as well as characteristics of its own. Width varies depending
on site and climatic factors. Transition zone between two vegetation
types or vegetation-type regions. (3) A transition line or strip of
vegetation between two communities, having characteristics of both kinds
of neighboring vegetation as well as characteristics of own. (4) A
locally adapted population within a species which has certain
genetically determined characteristics; interbreeding between ecotypes
in not restricted. (5) A variety or strain within a given species that
maintains its distinct identity by adaptation to a specific environment.
(6) A locally adapted population of a species which has a distinctive
limit of tolerance to environmental factors. (7) A variant type within
an ecospecies.

**Ecovar** - The offspring of native species that have been developed
from original plant material collected form a specific ecological
region. Selection is done with minor emphasis on improving agronomic
characteristics, and major emphasis on maintaining genetic diversity.
See also "ecotype".

**Educational Plantings** -- Plantings designed to introduce the
establishment and uses of new or potential releases to the public.
Educational plantings show one or more conservation practice uses for
the plant material, possibly in comparison to a standard cultivar or
species; plantings may be established on or off-center. See also
"demonstration plantings".

**Emulsifying Agent** - A surface active material that facilitates the
suspension of one liquid in another.

**Emulsion** - The suspension of one liquid as minute globules in
another liquid; for example, oil dispersed in water.

**Environment** - The sum of all external conditions that affect an
organism or community to influence its development or existence.

**Environmental Range** - Range of environmental conditions in which, at
a given time, the members of a species live.

**Epinasty** - Increased growth on the upper surface of a plant organ or
part (especially leaves) that causes it to head downward.

**Epithet** - The final word or combination of words in a name that
denotes an individual taxon.

**Exotic** - A term describing an organism introduced from another
country or continent.

**Facultative Weed** - Weed found growing both wild and in association
with human activity.

**Field Evaluation Planting (FEP)** - Old name for off-center
evaluations; term not currently used by the PM program. See "off-center
evaluations".

**Field Plantings** - Final stage of technology development or plant
selection; plantings used primarily by PMSs to develop new methods or
technology or evaluate the adaptability of new releases; data is
collected and analyzed statistically.

**Field-Scale Increase** - The reproduction of plant materials for use
in field plantings and by cooperating agencies to obtain the final data
needed to determine the feasibility of a variety release.

**Firm Seed** - Seed, other than hard seed, that neither germinates nor
decays during a prescribed test period under prescribed test conditions.
Firm ungerminated seed may be alive or dead.

**Forb** - Any non-woody plant that is not a grass, sedge, or rush.

**Foundation Seed** -- The progeny of breeder or foundation seed that is
so handled as to most nearly maintain specific genetic identity and
purity. Production may be carefully supervised by the originating agency
and approved by the certifying agency, the agricultural experiment
station, or both. See also "seed certification classes".

**Frost-Free Period** - The period, number of days or both between the
last frost in spring and the first frost in fall.

**Gene Bank** - A storage facility where germplasm is stored in the form
of seeds, pollen, or in vitro culture, or in the case of a field gene
bank, as plants growing in the field.

**Gene Flow** - The transfer of genes from one population to another.
See also "genetic flow".

**Gene Frequency** - The relative frequency with which a particular gene
is present in a particular population of a species or other group.

**Gene Pool** - The total stock of genes in a breeding population, with
each gene representing a number of alleles. See also "genetic pool".

**Genetic Diversity** - The total amount of genetic variation present in
a population or species. Having a heterogeneous constitution, reacting
differently to diverse external condition. (Applied to a breeding
population, variety, or species.). The genetic constitution of an
individual or group.

**Genetic Drift** - Chance occurrences in small populations which lead
to changes in gene frequencies from generation to generation. The
tendency, within small interbreeding populations, for heterozygous gene
pairs to become homozygous for one allele or the other by chance rather
than by selection. A change in gene frequency that occurs in small
populations as a result of random sampling error during reproduction.
The fluctuation in gene frequency occurring in an isolated population,
presumably due to random variations from generation to generation.

**Genetic Engineering** - The use of in vitro techniques to produce DNA
molecules containing novel combinations of genes or other sequences in
living cells that make them capable of producing new substances or
performing new functions. Usage: A popular term for such technologies as
a whole.

**Genetic Erosion** - The loss of genetic diversity between and within
populations of the same species over time; or a reduction of the genetic
base of a species due to human intervention, environmental changes, etc.

**Genetic Flow** - The exchange of genes between different populations.
Also termed migration, it is considered to be a source of genetic
variation. A single introduction of genes into a new population is known
as gene exchange. If gene migration is constant and recurrent it is
known as gene flow. The closer populations are related spatially and
genetically, the more likely the chances of gene flow.

**Genetic Pool** - The totality of genes and gene complexes of a given
population at a given time. The sum of all genetic information carried
by all individuals of an interbreeding population. All of the alleles of
all the genes in a population.

**Genetic Shift** - A change in the germplasm balance of a
cross‑pollinated variety, usually caused by environmental selection
pressures.

**Genetic Vulnerability** - Having a narrow range of genetic diversity
and reacting uniformly to diverse external conditions. (Applied to
breeding populations of varieties or species).

**Genotype** - The genetic constitution of an individual or group of
plants. Individual plants may vary in appearance (phenotypically), but
they must have the genetic characteristics of the genotype.. The genetic
constitution, latent or expressed, of an organism, as contrasted with
the phenotype. The sum total of all genes present in an individual..

**Geographic Range** - Geographic limits of the ecological range;
geographic extent of actual occurrences of a species.

**Germination** - The initiation of growth by the embryo and development
of a young plant from seed.

**Germplasm** -- Genetic material that determines the morphological and
physiological characteristics of a species.

**Grex** - A collective term applies to the progeny of an artificial
cross from known parents; each and every crossing of any two parents
belonging to different taxa that bear the same pair of specific,
intraspecific, interspecific, grex, or cultivar epithets.

**Green Manure Crop** -- A crop that is plowed under while still living
to increase organic matter in soil.

**Growing Season** - (1) The period, number of days, or both between the
last frost in spring and the first freeze threshold temperature of the
crop or other designated temperature threshold. (2) The amount of time a
plant is able to actively grow.

**Habitat Type** - The collective area which one plant association
occupies or will come to occupy as succession advances. The habitat type
is defined and described on the basis of the vegetation and its
associated environment.

**Hard Seed** - Seeds that remain hard at the end of a prescribed
germination test because they have not absorbed water due to an
impermeable seed coat.

**Herbaceous** - A vascular plant that does not develop woody tissue.

**Heritability** - The proportion of observed variability due to
heredity; the remainder is due to environmental causes.

**Heterosis** - Hybrid vigor such that the F~1~ hybrid falls outside the
range of the parents with respect to some character or characters.

**Heterozygous** - Having unlike alleles at one or more corresponding
loci (such as Yy).

**Historic Climax Plant Community** - The original natural plant
community that represents the final or highest stable level in a
successional series that is in dynamic equilibrium with ecosystem
components - soils, vegetation, climate, etc. The assumed end point in
primary as well as secondary succession. Synonym-Climax Plant Community.
See Climax.

**Homozygous** - Having alike alleles (such as YY). An organism may be
described as homozygous at one, several or all loci.

**Horticultural Annual** - A biennial or perennial which may treated as
an annual in parts of the country where the usually persistent plant
parts do not survive more than one growing season.

**Hybrid** - offspring of a cross between genetically dissimilar
individuals. First-generation progeny resulting from the controlled
cross-fertilization between individuals that differ in one or more
genes.

**Increase Plantings** -- P production of seed or other reproductive
parts of plant material to be made available for use in evaluations,
field plantings, demonstration plantings, educational plantings or for
distribution. See also "initial increase".

**Indicator Species** - (1) Species that indicate the presence of
certain environmental conditions, range condition, previous treatment,
or soil type. (2) One or more plant species selected to indicate a
certain level of grazing use.

**Indigenous** - Born, growing, or produced naturally (native) in a
specified area, region, or country.

**Initial Evaluation** - The evaluation of the characteristics and
comparative performance of an assembly of plants under controlled
conditions so that promising plants can be selected for further
evaluation.

**Initial Increase** - The production of small quantities of seed or
other reproductive parts of materials selected from initial or advanced
evaluations to be used for further evaluation and exchange.

**Inter-Center Strain Trial (ICST)** - Controlled, repeatable
evaluations where scientific methods and experimental designs are used
to study plants and techniques. Used to determine state and regional
plant performance and adaptation.

**Interseeding** - Seeding into an established vegetation cover. Often
involves planting seeds into the center of narrow seedbed strips,
commonly of variable spacing prepared by mechanical or chemical
methods..

**Introduced** - A species not part of the original fauna or flora of
the area in question, but introduced from another geographical region
through human activity. Syn.: exotic. Introduced is [not]{.underline}
synonymous and should [not]{.underline} be confused with the term
"invasive species".

**Invader** - (1) Plants not a part of the original plant community that
invade an area due to disturbance and/or plant community deterioration.
(2) Plant species that were absent in undisturbed portions of the
original vegetation of a specific range site and will invade or increase
following disturbance or continued heavy grazing.

**Invasion** - The migration of organisms from one area to another area
and their establishment in the latter.

**Invasive Plants** -- plants that reproduce rapidly and spread
aggressively from the area in which they originally occurred or were
planted, posing a threat to natural area diversity or managed /
agricultural area productivity. See also "Invasive Species".

**Invasive Species** - A species that demonstrates rapid growth and
spread, invades habitats, and displaces other species. Species that are
prolific seed producers, have high seed germination rates, easily
propagated asexually by root or stem fragments, and/or rapidly mature
predispose a plant to being an invasive. Example: The hybrid cattail
(*Typha* x*glauca*), a cross between native cattails, is extremely
aggressive and out-competes its parents and other native species when
established. Introduced species that are predisposed to invasiveness
have the added advantage of being relatively free from predators
(herbivores, parasites, and disease) and can therefore, expand more
energy for growth and reproduction. Example: Nepal (*Microstegium
vimineum*), introduced from Asia, displaces native vegetation in
floodplains and other moist environments creating a monoculture in the
herbaceous layer. *Microstegium* now occurs in 21 states and Puerto
Rico, ranging from Texas to Florida in the south and north into New York
State and Illinois. Invasive species should [not]{.underline} be
confused with "Introduced Species".

**Kind** - One or more related species or subspecies that singly or
collectively is known by one common name; for example, wheat, vetch and
sweetclover.

**Limited Generations** - A restriction placed by the developer on the
number of generations through which a variety may be sold by variety
name.

**Line** - A group of individuals of common ancestry. Genetically, a
more narrowly defined group than a strain or a variety.

**Liner -** Plant material which is grown in one location and then
"lined-out" in another location for finishing off. Plants may be started
in seedbeds and lifted bare-root or grown in containers. Either type of
these liners may be finish their production cycle in the ground or in
containers.

**Linkage** - Association of genetic factors; the genes are in the same
chromosome.

**Local Native** - A genetically local source that originated at or
within the same seed zone and elevation band as the project site
(planned planting). See also "range site" and "woodland site".

**Local Population** - Group of individuals of the same species growing
near enough to each other to interbreed and exchange genes.

**Long Range Plan** - A plan which directs plant materials activities of
the PMC or within a state or the PMC service area.

**Major Land Resource Areas (MLRA)** -- A system of land classification
composed of geographically associated land resource units; MLRAs are
important in agricultural and other types of regional planning. Land
resource units are geographic areas, usually several thousand acres in
extent, that are characterized by a particular pattern of soils,
climate, water resources, and land uses.

**Management Site Potential** - The kinds of levels of productivity or
values of a range site that can be achieved under various management
prescriptions.

**Mass Selection** - Selection of individual plants and propagation of
the next generation from the aggregates of that seed.

**Memorandum of Understanding** - A written instrument evidencing the
intent of two or more parties to cooperate in carrying out an
undertaking that will result in mutual benefit to the parties concerned.
Each party works within its own sphere of work and authority. It is not
a fiscal document used as a basis for obligating funds. It may run for
an indefinite time or be limited.

**Miscible Liquids** - Two or more liquids capable of being mixed; they
will remain mixed under normal conditions.

**Mixture** - More than one kind of seed or variety; each is present in
excess of 3 percent of the whole.

**Monoecious** - Staminate and pistillate flowers borne separately on
the same plant.

**Morphology** - A branch of biology dealing with the form and structure
of organisms.

**Native Grazing Land -** Land used primarily for production of native
forage plants maintained or manipulated primarily through grazing
management. Native grazing land includes grazed rangeland, grazed
forestland, and native and naturalized pasture, individually or
collectively.

**Native Plant** - See "native species".

**Native Species** - A native plant species is one that occurs naturally
in a particular region, state, ecosystem, and habitat without direct or
indirect human actions. Its presence and evolution in an area are
determined by climate, soil, and biotic factors. Synonyms of native
include indigenous, endemic, aboriginal.

**Natural Potential** - Occasionally used as synonym for climax with
reference to range vegetation.

**Naturalized Plant** - A plant introduced from other areas that has
become established in and more or less adapted to a region by long,
continued growth. See also "naturalized species".

**Naturalized Species** - A species introduced from other areas that has
become established in and more or less adapted to a region by long,
continued growth there. Does not require artificial inputs for survival
and reproduction, and has established a stable or expanding population.
Examples: cheatgrass, Kentucky bluegrass, starling, etc.

**Nonselective Herbicide** - A chemical that is toxic to plants,
generally without regard to species.

**Noxious Weed** - A weed arbitrarily defined by law as being especially
undesirable, troublesome, and difficult to control. Definition varies
according to legal interpretations.

**Nurse Crop** - See "companion crop".

**Off-center Evaluations** - Plantings used by PMCs to evaluate releases
or technology off the center; data is collected and analyzed
statistically; was previously named "field evaluation planting."

**On-center Evaluations** - Plantings done on the PMC to evaluate new
technology or new plant selections; data is collected and analyzed
statistically.

**Open Pollination** - Natural, as opposed to controlled, pollination.
Open pollinated seed contrasts with hybrid seed.

**Perennial** - A plant that lives more than 2 years.

**Performance Trial** -- A planting designed to test a potential plant
release for reliability in a particular conservation application. May
require multiple plantings and/or off-center sites. Standards for
comparison are to be included if available.

**Phenology** - A branch of science dealing with the relationship
between climate and periodic biological phenomena. Also dates or
sequence of occurrence of different growth stages of plants.

**Phenotype** - (1) The external appearance or discernible
characteristics of an organism, resulting from interaction between an
organism\'s genetic makeup (genotype) and the environment. A group of
individual plants may appear alike (phenotypically) but not have the
same genotype, or they may vary in appearance and have the same
genotype. (2) Observable characteristics.

**Photosynthesis** - The metabolic pathway by which plants produce food.
See also "C-3 plants", "C-4 plants", and "CAM plants".

**Pioneer Species** - The first species or community to colonize or
recolonize a barren or disturbed area in primary or secondary
succession.

**Plan of Operations (PO)** - see \'Business Plan\'

**Plant Association** - A kind of climax plant community consisting of
stands with essentially the same dominant species in corresponding
layers.

**Plant Community Type** - Each of the existing plant communities that
can occupy an ecological site. Several plant community types will
typically be found on an ecological site, including the historic climax
plant community for that site.

**Plant Variety Protection Act (PVPA)** - Approved December 23, 1970,
the PVPA offers legal protection to developers of new releases or
varieties of plants that reproduce sexually, that is, through seed.
Developers of plants that reproduce asexually have received protection
from the U.S. Patent Office since 1930. The law states that protection
will be extended to a "novel variety\" if it has these three
qualifications: [Distinctness]{.underline} - The variety must differ
from all known prior varieties by one or more identifiable
morphological, physiological, or other characteristic;
[Uniformity]{.underline} - If any variations exist in the variety, they
must be describable, predictable, and commercially acceptable; and
[Stability]{.underline} - When sexually reproduced, the variety must
remain unchanged in its essential and distinctive characteristics to a
degree expected of similarly developed varieties.

**Polycross** - Open-pollination of a group of genotypes (generally
selected) in isolation from other compatible genotypes in such a way
that each of the original selections has an equal opportunity at
pollinating, or being pollinated by, any of the others.

**Population** - (1) The aggregate of organisms which inhabit a
particular area or region; (2) a (specified) portion of such an
aggregate, usually a group of organisms of the same kind occupying an
area small enough to allow interbreeding.

**Population Genetics** - A branch of genetics dealing with the
frequency and distribution of genes, mutants, genotypes, etc. among
populations of organisms. Population genetics is now based upon an
increasing input of laboratory and field observations under an array of
environments; much of this work involves the documentation and
interpretation of genetic variability in natural populations.

**Post-Emergence** - After the emergence of a specified weed or crop.

**Potential Natural Community** - The biotic community that would become
established on an ecological site if all successional sequences were
completed without interferences by man under the present environmental
conditions. Natural disturbances are inherent in its development.

**Pre-Emergence** - Before the emergence of a specified weed or crop.

**Pre-Planting** - Any time before the crop is planted.

**Pristine** - A state of ecological stability or condition existing in
the absence of direct disturbances by modern man. See also "relict".

**Project** - A national PM activity that is broad in nature and serves
as an umbrella for PMC studies. Refer to Part 540.51 of the NPMM for
more information on PM projects.

**Project Statement** - A document that outlines the details of a
National PM Project. Refer to Part 540.51 of the NPMM for more
information on PM project statements.

**Pure Line** - Succession of generations of organisms homozygous for
all genes.

**Pure Live Seed (PLS)** - The product of the percentage of germination
plus the hard seed and the percentage of pure seed divided by 100.

**Purity** - (1) The name or names of the kind, type, or varieties and
the percentage or percentages thereof. (2) The percentage of other
agricultural seed or crop seed; the percentage of inert matters. (3) The
percentage of weed seed, including noxious weed seed, and the names of
the noxious weed seed and the rate of occurrence of each.

**Race** - A term sometimes used to denote ecotypes.

**Range Condition** - A generic term relating to present status of a
unit of range in terms of specific values or potentials. Specific values
or potentials must be stated. Some agencies define range condition as
follows: the present state of vegetation of a range site in relation to
the climax (natural potential) plant community for that site. It is an
expression of the relative degree to which the kinds, proportions, and
amounts of plants in a plant community resemble that of the climax plant
community for the site.

**Range Condition Class** - Confusion has existed regarding both
definition and use of this term. The following definition fits the
thinking expressed in the definition Range Condition: one of a series of
arbitrary categories used to either classify ecological status of a
specific range site in relation to its potential (early, mid, late, or
potential natural community) or classify management-oriented value
categories for specific potentials, e.g., good condition spring cattle
range.

**Range Degradation** - The degeneration of a site caused by biotic or
abiotic factors which results in a lowered successional status to the
point that ecological potential is changed. See also "Range Site
Degeneration".

**Range Retrogression** - The degradation of a site caused by biotic or
abiotic factors which results in movement of the site to a lower
successional status within the same ecological potential.

**Range Seeding** - The process of establishing vegetation by the
artificial dissemination of seed. Establishing adapted plant species on
ranges by means other than natural revegetation. See also "Reseeding".

**Range Site** - An area of rangeland having the potential to produce
distinctive kinds and amounts of vegetation, resulting in a
characteristic plant community under its particular combination of
environmental factors, especially soils and climate. Each range site is
typified by an association of species that differ from that of other
range sites in the kind or proportions of species, or in total
production. Synonymous with ecological site when referring to rangeland.
Some agencies use range site based on the climax concept, not potential
natural community. Syn.: Ecological Site.

**Range Site Degeneration** - The degradation of a site caused by biotic
or abiotic factors which results in an ecological shift to a lower
successional status and possibly a lower ecological potential for
production. Syn.: retrogression. See also "range degradation".

**Reciprocal Cross** - A second cross involving the same characters as
the first but with the sex of the parents interchanged.

**Reclamation** - Restoration of a site or resource to a desired
condition to achieve management objectives or stated goals. The
construction of plant, soil, and topographic conditions, after
disturbance, which permits the disturbed site to function adequately
within its ecosystem. However, the constructed conditions may not be
identical to predisturbance conditions. The process of reconverting
disturbed lands to their former uses or other productive uses.

**Recovery** - The rate or amount of regrowth following harvesting of a
forage species or following a dormant season.

**Recurrent Selection** - A method of breeding designed to concentrate
favorable genes scattered among a number of individuals by selecting in
each generation among the progeny produced by intermating of the
selected individuals of the previous generation.

**Registered Seed** - The progeny of foundation seed that is so handled
as to maintain satisfactory genetic identity and purity and that has
been approved and certified by the certifying agency. This class of seed
should be of a quality suitable for production of certified seed. See
also "seed certification classes".

**Registered Variety** - (1) For grasses and agricultural species: A
variety accepted, numbered, and registered as a recognized improved
variety by the Committee on Varietal Standardization and Registration of
the Crop Science Society of America. (2) For other species: A variety
which has been registered with the appropriate International Species
Registrar.

**Rehabilitation** - Return of land to a form and productivity that
conforms with a prior land use plan, including a stable ecological state
that does not contribute substantially to environmental deterioration
and is consistent with surrounding aesthetic values. Improving a project
site to a more desired condition than previously existed, usually as
result of a major disturbance. Synonymous with reclamation.

**Released Variety** - A new variety of proved value that is made
available to the public, according to ESCOP standards, for a
conservation purpose. See also "variety".

**Relict** - A remnant or fragment of the climax plant community that
remains from a former period when it was more widely distributed. See
also "pristine".

**Reseeding** - A crop variety or inbred line that has been evaluated
and made available to the public. To make available to the public. To
seed again, usually soon after an initial seeding has failed to achieve
satisfactory turf establishment.

**Restoration** - The process of restoring site conditions as they were
before land disturbance.

**Revegetation** - Establishing or re-establishing desirable plants in
areas where desirable plants are absent or of inadequate density, by
management alone (natural revegetation) or by seeding or transplanting
(artificial revegetation). A general term for renewing the vegetation on
a project site, which include restoration and rehabilitation. Refers to
the vegetation construction phase of reclamation.

**Riparian Community Type** - A recurring, classified, defined and
recognizable assemblage of riparian plant species. A repeating,
classified, defined and recognizable assemblage of riparian plant
species.

**Riparian Ecosystems** - (1) Those assemblages of plants, animals, and
aquatic communities whose presence can be either directly or indirectly
attributed to factors that are water‑influenced or related. (2)
Interacting system between aquatic and terrestrial situations,
identified by soil characteristics, and distinctive vegetation that
requires or tolerates free or unbound water.

**Riparian Species** - Plant species occurring within the riparian zone.
Obligate species require the environmental conditions within the
riparian zone; facultative species tolerate the environmental
conditions, therefore may also occur away from the riparian zone.

**Seed Certification** - A system whereby seed of plant cultivars (and
pre-varietal releases) is produced, harvested and marketed under
authorized regulation to insure seed of high quality and genetic purity.

**Seed Certification Classes -** Classes of seed produced by a grower to
ensure the purity of the genetic material. Seed which undergoes the
certification process is typically inspected during the growing season
or at harvest and the seed is tested. Certification classes include:
Breeder, Foundation, Registered, Certified, and Common. See also
"breeder seed", foundation seed", "registered seed", "certified seed",
and "common seed".

**Seed Certifying Agency** - General term for the state or other agency
responsible for the release and certification of crop varieties and for
inspecting and approving seed produced under one of the seed
certification classes. Most seed certification agencies are members of
the Association of Official Seed Certifying Agencies (AOSCA).

**Seed Lot** - A definite quantity of seed identified by a lot number,
every portion or bag of which is uniform, within permitted tolerances,
for the factors that appear on the labeling.

**Selected Class Release** - (1) Seed that is the progeny of rigidly
selected seed or stands of untested parentage that have promise but not
proof of genetic superiority, and for which geographic source and
elevation shall be stated on the certification label. (2) One of the
classes of pre-varietal releases recognized by AOSCA.

**Selection** - Selecting an accession or accessions from an assembly,
or individuals from within an accession, to obtain the plants having the
best characteristics for a particular conservation use.

**Selective Herbicide** - A chemical that is more toxic to some plant
species than to others.

**Self Pollination -** The transfer of pollen from the anther of a
flower to the stigma of the same flower, or different flowers on the
same plant.

**Seral** - Refers to species or communities that are eventually
replaced by other species or communities within a sere.

**Seral Community** - One of a series of biotic communities that follow
one another in time on any given area. Syn. successional community.

**Seral Stages** - The developmental stages of an ecological succession.

**Sere** - All temporary communities in a successional sequence. The
complete series of ecological communities occupying a given area over
hundreds or thousands of years from the initial to the final or climax
stage.

**Sod Seeding** - Direct drilling of seed into sod of existing
vegetation with no mechanical seedbed preparation.

**Soil Application** - Chemical applied mainly to the soil surface
rather than to vegetation.

**Soil Incorporation** - Mechanical mixing of a chemical with the soil.

**Soil Injection** - Mechanical placement of a chemical beneath the soil
surface with a minimum of mixing or stirring.

**Soil Sterilant** - A biocide that prevents the growth of plants and
kills all living organisms when present in the soil. Soil sterilization
effects may be temporary or permanent.

**Source-Identified Seed -** (1) Source identified propagating materials
are seed, seedlings, or other propagating materials collected from
natural stands, seed production areas, seed fields, or orchards where no
selection or testing of the parent population has been made. (2) One of
the classes of pre-varietal releases recognized by AOSCA.

**Stand** - (1) A population of plants. (2) Density of population or
number of individuals per unit area.

**Standard Plant** - (1) A commonly used species or, if available,
variety for the use of which an evaluation is being made. (2) A plant
which serves as the standard for comparison.

**Strain** - (1) A group of organisms of common origin having one or
more definite morphological or physiological characteristics that are
heritable. (2) A term to include breed differences within a species, or
as a group of plants differing little, if any, in morphology yet
physiologically distinct in some additional quality such as yield or
vigor: i.e., the northern and southern strains of smooth brome. Strain
also means variety, ecotype, biotype, type, or a group of these.

**Study** - An activity at a PMC that develops a product to address a
conservation need identified in the PMC LRP. A PMC study must be
outlined in a study plan and be identified in the PMC Business Plan and
Workload Analysis. Refer to Part 540.52 of the NPMM for more information
on PMC studies.

**Study Plan** - A comprehensive document that outlines the details of a
PMC study. Refer to Part 540.52 of the NPMM for more information on PMC
study plans.

**Subspecies -** A grouping within a species used to describe
geographically isolated variants, a category above "variety", and is
indicated by the abbreviation "ssp." in the scientific name.

**Succession** - (1) The progressive replacement of plant communities on
a site which leads to the potential natural plant community, i.e.,
attaining stability. Primary succession entails simultaneous successions
of soil from parent material and vegetation. Secondary succession occurs
following disturbances on sites that previously supported vegetation,
and entails plant succession on a more mature soil. (2) The progressive
development of vegetation toward its highest ecological expression, the
climax replacement of one plant community by another.

**Surfactant** - A material that facilitates and accentuates the
emulsifying, dispersing, spreading, wetting, and other surface-modifying
properties of herbicide formulation.

**Suspension** - A system consisting of very finely divided solid
particles dispersed in a solid, liquid, or gas.

**Synergism** - Cooperative action of different chemicals or organisms
such that the total effect is greater than the sum of the independent
effects.

**Synthetic Variety** - Advanced generation progenies of a number of
clones or lines (or of hybrids among them) obtained by open-pollination.

**Testcross** - A cross of a double or multiple heterozygote to the
corresponding multiple recessive to test for homozygosity or linkage.

**Tested Seed -** (1) Seeds or plants which have been through additional
testing on more than one generation which will include testing on
multiple sites with replicated plots to verify performance and
heritability of desirable traits. The material has proven genetic
superiority or possesses distinctive traits for which heritability is
stable as defined by the certifying agency. (2) One of the classes of
pre-varietal releases recognized by AOSCA.

**Tetraploid** - An organism having four basic sets of chromosomes.

**Topcross Progeny** - Progeny from outcrossed seed of selections,
clones or lines crossed with a single variety or line that serves as a
common pollen parent.

**Translocated Herbicide** - An herbicide that is distributed throughout
the plant from the point of entry. Syn. Systemic herbicide.

**Trend** - The direction of change in ecological status or resource
value rating observed over time. Trend in ecological status should be
described as toward, or away from the potential natural community, or as
not apparent. Trend in a resource value rating for a specific use should
be described as up, down or not apparent. Trends in resource value
ratings for several uses on the same site at a given time may be in
different directions, and there is no necessary correlation between
trends in resource value ratings and trend in ecological status. Some
agencies use trend only in the context of ecological status. Syn. range
condition trend. See and "apparent trend".

**Type** - A group of varieties so nearly similar that the individual
varieties cannot be clearly differentiated except under special
conditions. For further information, refer to the Federal Seed Act Rules
and Regulations.

**Use Groups** - The artificial grouping for the comparative testing of
plant materials having similar uses.

**Variety** - (1a) The botanical nomenclature division consisting of
more or less recognizable entities within species that are not
genetically isolated from each other, below the level of subspecies, and
is indicated by the abbreviation "var." in the scientific name (see
"botanical variety"); (1b) The rank of taxa below subspecies but above
forma; a plant which retains most of the characteristics of the species,
but differs in some way such as flower or leaf color, size of mature
plant, etc. A variety is added to the specific binomial and preceded by
\"var.\", such as *saxatilis* in the epithet *Juniperus communis* var.
*saxatilis*. (2) Term used in some national and international
legislation to denominate one clearly distinguishable taxon from
another; equivalent to "cultivar". (Note: the Plant Materials Program
does not recognize the terms "variety" and "cultivar" as equivalent.)

**Vegetation Type** - A kind of existing plant community with
distinguishable characteristics described in terms of the present
vegetation that dominates the aspect or physiognomy of the area. Syn.
Type.

**Warm-Season Plant** - A plant that completes most of its growth during
the warm part of the year, generally late in spring and in summer.
Commonly a C-4 plant photosynthetic pathway.

**Wetland Communities** - Plant communities that occur on sites with
soils typically saturated with or covered with water most of the growing
season.