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World Food Crops Glossary

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Note to Students

Please let me know if there are words used in the course that you think should be included in this glossary! kimberly@oregonstate.edu

Sources

Garden Web Glossary of Botanical Terms http://glossary.gardenweb.com/glossary/

Glossary of Crop Science Terms, Crop Science Society of America
http://www.crops.org/cropgloss/

International Rice Research Institute. A Glossary of Rice Terminology
http://www.knowledgebank.irri.org/glossary/whnjs.htm

Levetin and McMahon. 2003. Plants and Society. 3rd edition. McGraw-Hill, New York, NY.
http://highered.mcgraw-hill.com/sites/dl/free/0072909498/57896/glossary.pdf

Lumpkin, T.A. 1995. WORLD CROPS lab manual, Washington State University

Schlegel, R. Plant Breeding Updates http://www.desicca.de/plant_breeding/

Schlindwein, B. A Hypermedia Glossary of Genetic Terms. http://www.weihenstephan.de/~schlind/genglos.html

University of California, Berkeley, Museum of Paleontology. Glossary.
http://www.ucmp.berkeley.edu/glossary/glossary.html

World Resources Institute. Biodiversity Glossary of Terms.
http://www.wri.org/wri/biodiv/gbs-glos.html

Directory of Genetics Glossaries

Glossaries of Genome / Human Genetics Terms http://www.kumc.edu/gec/glossary.html

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A

Accession
A sample of a crop variety collected at a specific location and time; may be of any size.
Adaptation
A genetically determined characteristic that enhances an organism's ability to cope with its environment.
Agrobiodiversity
The diversity of plants, animals, and ecologies found in agricultural systems
Alien species
A species occurring in an area outside of its historically known natural range as a result of intentional or accidental dispersal by human activities. Also known as introduced species.
Allele
One of several forms of the same gene.
Alternation of Generations
Alternation between a haploid gametophyte phase and a diploid sporophyte phase in the life cycle of sexually reproducing organisms.
Aneuploid
Having one more or less than the normal, euploid number of chromosomes.
Anther
Male reproductive structure that produces pollen.
Anthesis
The time of flowering or pollination.
Asexual Reproduction
Any form of reproduction not involving the union of gametes.
Auricles
Finger-like projections that grow out from the opposite corners of the collar and are important in the identification of grasses.
Awn
A slender appendage found on the end or back of the lemma.
Axillary Tillers
The tillers that emerge from the leaf axils.
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B

Biodiversity
The totality of genes, species, and ecosystems in a region or the world.
Biogeography
The scientific study of the geographic distribution of organisms.
Biological Resources
Those components of biodiversity of direct, indirect, or potential use to humanity. (Used interchangeably with "Biotic Resources")
Biome
A major portion of the living environment of a particular region (such as a fir forest or grassland), characterized by its distinctive vegetation and maintained by local climatic conditions.
Bioregion
A territory defined by a combination of biological, social, and geographic criteria, rather than geopolitical considerations; generally, a system of related, interconnected ecosystems.
Biota
All of the organisms, including animals, plants, fungi, and microorganisms, found in a given area.
Biotechnology
Any technique (e.g., recombinant DNA methods, protein engineering, cell fusion, nucleotide synthesis, biocatalysis, fermentation, cell cultures, cell manipulations etc.) that uses living organisms or parts of them to make or modify products, to improve organisms or to make them available for specific uses.
Biotic
Pertaining to any aspect of life, especially to characteristics of entire populations or ecosystems.
Blade
The flat expanded portion of a leaf.
Bracts
Special modified leaves found in monocot inflorescences that replace the calyx and corolla.
Buffer zone
The region near the border of a protected area; a transition zone between areas managed for different objectives.

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C

Calyx
A collective term that refers to all the sepals together.
Carrying Capacity
The maximum number of people, or individuals of a particular species, that a given part of the environment can maintain indefinitely.
Caryopsis
The one-seeded dry fruit of grasses in which the testa and pericarp are completely fused and inseparable at maturity.
Center of Diversity
Geographic region with high levels of genetic or species diversity.
Center of Endemism
Geographic region with numerous locally endemic species.
Central dogma of biology
DNA from alleles at a genetic locus translates into proteins.
Characteristic Diversity
The pattern of distribution and abundance of populations, species, and habitats under conditions where humanity's influence on the ecosystem is no greater than that of any other biotic factor.
Chiasmata
The x-shaped configuration formed by two chromatids of homologous chromosomes as they remain attached to each other during prophase I of meiosis.
Chromatid
One of the two strands of a chromosome; they are united by a centromere.
Class
In taxonomy, a category just beneath the phylum and above the order; a group of related, similar orders.
Climax Community
The end of a successional sequence; a community that has reached stability under a particular set of environmental conditions.
Cline
Change in population characteristics over a geographical area, usually related to a corresponding environmental change.
Clone
A population of individuals all derived asexually from the same single parent.
Coleoptile
Protective structures found in monocot seeds that cover the embryonic shoot bud or plumule
Coleorhiza
Protective structures found in monocot seeds that cover the embryonic root
Coleoptilar Tiller
The tiller that emerges from the coleoptilar node.
Collar
The junction of the leaf blade with the sheath.
Co-management
The sharing of authority, responsibility, and benefits between government and local communities in the management of natural resources.
Common Property Resource Management
The management of a specific resource (such as a forest or pasture) by a well-defined group of resource users with the authority to regulate its use by members and outsiders.
Community
An integrated group of species inhabiting a given area; the organisms within a community influence one another's distribution, abundance, and evolution. (A Human Community is a social group of any size whose members reside in a specific locality.)
Comparative Advantage
Relative superiority with which a region or state may produce a good or service.
Complete Flower
A flower that has all essential and accessory components.
Compound Leaf
A leaf composed of leaflets; the arrangement of the leaflets on the petiole can be either palmate, all the leaflets attached at the same point at the end of the petiole, or pinnate, the leaflets attached along the longitudinal axis of the petiole.
Conservation
The management of human use of the biosphere so that it may yield the greatest sustainable benefit to current generations while maintaining its potential to meet the needs and aspirations of future generations: Thus conservation is positive, embracing preservation, maintenance, sustainable utilization, restoration, and enhancement of the natural environment.
Conservation of Biodiversity
The management of human interactions with genes, species, and ecosystems so as to provide the maximum benefit to the present generation while maintaining their potential to meet the needs and aspirations of future generations; encompasses elements of saving, studying, and using biodiversity.
Corm
The enlarged fleshy base of a stem, bulb-like but solid.
Corolla
A collective term that refers to all the petals together.
Cortex
the region of a stem or root surrounding the vascular cylinder but inside the epidermis. Undifferentiated loosely packed cells that can function as storage tissues.
Cosmopolitan
Widely distributed over the globe.
Cotyledon
An embryo leaf that usually serves as the major food reserve for dicot seedlings May absorb food for seedling growth
Crossing-over
The exchange of corresponding segments of chromatids between homologous chromosomes during prophase I of meiosis.
Crown
Several nodes whose internodes do not elongate at the junction of the stem and the root.
Cryogenics
The branch of physics relating to the effects and production of very low temperatures; as applied to living organisms, preservation in a dormant state by freezing, drying, or both.
Cultivar
A cultivated variety (genetic strain) of a domesticated crop plant.
Cultural diversity
Variety or multiformity of human social structures, belief systems, and strategies for adapting to situations in different parts of the world.
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D

Decomposition
The breakdown of organic materials by organisms in the environment, releasing energy and simple organic and inorganic compounds.
Demography
The rate of growth and the age structure of populations, and the processes that determine these properties.
Detritivores
Organisms consuming non-living material, such as many fungi, bacteria, and earthworms.
Dioecious
Having staminate and pistillate flowers on different plants of the same species.
Diploid
An individual having two chromosome sets in each of its cells.
Dominant
An allele that expresses its phenotypic effect even when heterozygous with a recessive allele.
Donor Control
A predator-prey interaction in which the predator does not control the prey population size.

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E

Ecosystem
The organisms of a particular habitat, such as a pond or forest, together with the physical environment inwhich they live; a dynamic complex of plant, animal, fungal, and microorganism communities and their associated non-living environment interacting as an ecological unit. Ecosystems have no fixed boundaries; instead, their parameters are set according to the scientific, management, or policy question being examined. Depending upon the purpose of analysis, a single lake, a watershed, or an entire region could be an ecosystem.
Ecotype
A genetically differentiated subpopulation that is restricted to a specific habitat.
Egg
A nonmotile female gamete.
Elongation Region
Existing root cells enlarge in size which moves the roots through the soil.
Embryo
The rudimentary plant in a seed. The embryo arises from the zygote.
Embryonic Stem
This structure is composed of two parts. The epicotyl is that portion of the stem above the cotyledons and below the plumule. The hypocotyl is stem tissue between the cotyledons and the radicle.
Endemic
Restricted to a specified region or locality.
Endodermis
Usually a single layer of root cells surrounding the stele.
Endosperm
Triploid tissue of monocots that arises from the triple fusion of a sperm nuclei with the polar nuclei of the embryo sac. In seeds of certain species, the endosperm persists as a storage tissue and is used by the seedling during germination for growth. It is composed mostly of starch cells
Environmental Heterogeneity
The physical or temporal patchiness of the environment. Heterogeneity exists at all scales within natural communities, ranging from habitat differences between the top and underside of a leaf, to habitat patches created by treefalls within a forest, to the pattern of forests and grasslands within a region.
Epidermis
Outermost layer of cells on roots, stems, and leaves which serves a protective function.
Epigeal Emergence
A type of emergence common in dicots characterized by the elongation of the hypogeal pulling the cotyledons to the ground surface
Evolution
Any gradual change. Organic evolution is any genetic change in organisms from generation to generation.
Ex situ Conservation
A conservation method that entails the removal of germplasm resources (seed, pollen, sperm, individual organisms, from their original habitat or natural environment. Keeping components of biodiversity alive outside of their original habitat or natural environment.
Extinction
The evolutionary termination of a species caused by the failure to reproduce and the death of all remaining members of the species; the natural failure to adapt to environmental change.
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F

Fauna
All of the animals found in a given area.
Fertilization (syngamy)
Formation of a zygote through the fusion of two gametes.
Fibrous Root System
The primary root (radicle) is not dominant in relation to those of its secondary and tertiary branches.
Filament
Structure that supports the anther so that it can disseminate pollen to flowers on the same plant or flowers on other plants.
Flora
All of the plants found in a given area.
Floret
Monocot flower that consists of a lemma and palea, lodicules, stamens, and the pistil.
Frugivore
An animal that eats fruit.
Fruit
A mature ovary usually containing seeds (one or many). The outside covering consists of the ovary wall (pericarp) and any other flower components such as the withered remains of the stamens, sepals, petals, etc. that may still be attached

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G

Gametes
A sex cell; one of two cells that unite, forming a zygote.
Gametophyte
The haploid (n) gamete-producing phase of the life cycle of an organism that exhibits Alternation of Generations.
Gene
The functional unit of heredity; the part of the DNA molecule that encodes a single enzyme or structural protein unit.
Gene Bank
A facility established for the ex situ conservation of individuals (seeds), tissues, or reproductive cells of plants or animals.
Gene Pool
All of the alleles available among the reproductive members of a population from which gametes can be drawn.
Genetic Diversity
Variation in the genetic composition of individuals within or among species; the heritable genetic variation within and among populations.
Genetic Erosion
An irreversible loss in genetic diversity, usually of crop plants or domestic animals.
Genetic Vulnerability
Potential for rapid, large-scale disease or insect epidemics, usually due to genetic uniformity of domesticated crops or animals.
Genome
The entire complement of genetic material in a chromosome set.
Genotype
The set of genes possessed by an individual organism.
Germination
A time beginning with water uptake by the seed (imbibition) continuing as the radicle breaks through the seed coat before the shoot does, ending with the start of elongation by the embryonic axis, usually the radicle. The first step in germination is the absorption of water and oxygen by the seed. During and following this water absorption stage, enzymes are formed which convert starch, fats, and protein into smaller more soluble forms which can be transported to sites of growth. A seed is germinated when the radicle and shoot have elongated and broken through the seed coat.
Germplasm
The genetic material, especially its specific molecular and chemical constitution, that comprises the physical basis of the inherited qualities of an organism. In plant breeding, the terms often refers to the genetic base of a particular crop, including individuals, populations, or relatives that may contribute genetically to its improvement.
Glumes
Two hardened or thin and chaffy bracts at the base of a spikelet.
Growing Point
The plant part where differentiation of leaves, tillers, and the inflorescence occurs.
Guard Cells
Control the opening and closing of the stomata.
Guild
A group of organisms that share a common food resource.
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H

Habitat
The environment in which an organism lives. Habitat can also refer to the organisms and physical environment in a particular place.
Heritability
The proportion of total phenotypic variance at the population level that is contributed by genetic variance (also called heritability in the broad sense). Heritability in the narrow sense: The proportion of phenotypic variance that can be attributed to additive genetic variance.
Heterozygote
An individual having unlike alleles at one or more corresponding loci.
Hilum
A detachment scar found on the dicot seed surface
Homeologous Chromosomes
Partially homologous chromosomes, usually indicating that they were derived from a common ancestry.
Homologous Chromosomes
Pairs of chromosomes that associate together in prophase I of meiosis; each member of a pair is derived from a different parent.
Homozygote
An individual aving like alleles at corresponding loci on homologous chromosomes.
Hybridization
Crossing of individuals from genetically different strains, populations, or species.
Hypogeal Emergence
A type of emergence common in monocots characterized by the elongation of the epicotyl and the cotyledons remaining below ground

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I

Imperfect Flower
A flower that is missing either the pistil or stamens, the essential components.
Inbreeding
A mating system involving the mating or breeding of closely related individuals, the most extreme form of which is self-fertilization. It is used to "fix" economically useful genetic traits in genetically improved populations; however, it also can result in fixation of deleterious recessive alleles.
Inbreeding Depression
A reduction in fitness or vigor as a result of fixation of deleterious, recessive alleles from consistent inbreeding in a normally outbreeding population.
Indicator Species
A species whose status provides information on the overall condition of the ecosystem and of other species in that ecosystem.
Indigenous Peoples
People whose ancestors inhabited a place or country when persons from another culture or ethnic background arrived on the scene and dominated them through conquest, settlement, or other means and who today live more in conformity with their own social, economic, and cultural customs and traditions than with those of the country of which they now form a part (also: "native peoples" or "tribal peoples").
Inflorescence
A cluster of flowers.
In situ Conservation
A conservation method that attempts to preserve the genetic integrity of gene resources by conserving them within the evolutionary dynamic ecosystems of the original habitat or natural environment.
Intellectual Property Right
A right enabling an inventor to exclude imitators from the market for a limited time.
Internode
Areas between stem nodes which contain elongated cells.
Introduced Species
A species occurring in an area outside of its historically known natural range as a result of intentional or accidental dispersal by human activities. Also known as alien species.
In vitro
Storage of plant or animal germplasm in tissue-culture form in glass containers.
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J

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K

Keystone Species
A species whose loss from an ecosystem would cause a greater than average change in other species populations or ecosystem processes.
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L

Landraces
A crop cultivar or animal breed that evolved with and has been genetically improved by traditional agriculturalists, but has not been influenced by modern breeding practices. Often referred to as "local varieties". May be heterogeneous mixtures.
Leaf Axil
The junction of the leaf with the main stem.
Leaf Blades
One of the two components of a monocot leaf that is responsible for most of the photosynthesis that occurs in plants.
Lemma and Palea
Two protective bracts at the base of each floret.
Life Form
Characteristic structure of a plant or animal.
Ligule
A thin membrane arising from the upper side of the leaf blade at the junction of the blade with the sheath which is important in the identification of grasses.
Locus
A specific place on a chromosome where a gene is located.
Lodicules
Structure found at the base of the pistil in the floret that will enlarge in size, forcing open the lemma and palea so that cross pollination can occur, after absorbing water.

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M

Maturation Region
Root cells differentiate into specialized tissues such as the xylem, phloem, cortex, root hairs, etc..
Meiosis
The process of two successive nuclear divisions through which segregation of genes occurs and a single diploid (2n) cell becomes four haploid (n) cells.
Meristem Region
A part of the root where cells are actively dividing by a process called mitosis.
Micropyle
A small seed surface opening usually found in dicot seeds where the pollen tube entered the ovule
Minimum Viable Population
The smallest isolated population having a good chance of surviving for a given number of years despite the foreseeable effects of demographic, environmental, and genetic events and natural catastrophes. (The probability of persistence and the time of persistence are often taken to be 99 percent and 1000 years, respectively.)
Mitosis
The process of nuclear division (karyokinesis) in cells that produces daughter cells that are genetically identical to each other and to the parent cell.
Monocropping
Production of a single crop species in a field.
Monoculture
Same as Monocropping.
Monoecious
A plant that has separate pistillate and staminate flowers such as maize.
Mutualism
Relationship between two or more species that benefits all parties.
Mycorrhizal Fungi
A fungus living in a mutualistic association with plants and facilitating nutrient and water uptake.
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N

National Income Accounts
System of record by which the vigor of a nation's economy is measured. (Results are often listed as Gross National Product, or Gross Domestic Product.)
Native Species
Plants, animals, fungi, and microorganisms that occur naturally in a given area or region.
Nitrogen Fixation
A process whereby nitrogen fixing bacteria living in mutualistic associations with plants convert atmospheric nitrogen to nitrogen compounds that plants can utilize directly.
Nectarivore
An animal that eats nectar.
Node
Areas of compressed stem tissue which give rise to other specialized plant parts such as leaves, branches, and flowers.
Non-governmental Organization (NGO)
A non-profit group or association organized outside of institutionalized political structures to realize particular social objectives (such as environmental protection) or serve particular constituencies (such as indigenous peoples). NGO activities range from research, information distribution, training, local organization, and community service to legal advocacy, lobbying for legislative change, and civil disobedience. NGOs range in size from small groups within a particular community to huge membership groups with a national or international scope.

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O

Orthodox Seed
Seed that can be dried to moisture levels between 4 and 6 percent and kept at low temperatures.
Ovary
Female reproductive structure that contains eggs within one or more ovules.
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P

Palisade Parenchyma
Internal leaf cells that contain the majority of the chloroplasts.
Parataxonomists
Field-trained biodiversity collection and inventory specialists recruited from local areas.
Patent
A government grant of temporary monopoly rights on innovative processes or products.
Pathogen
A disease-causing microorganism; a bacterium, fungus or virus.
Pedicel
Stem tissue that supports the flowers.
Peduncle
Specialized stem tissue for the support of a flower or an inflorescence. The last elongated internode which supports the inflorescence.
Perfect Flower
A flower that contains both the pistil and the stamens, the essential components.
Pericycle
Root tissue immediately inside the endodermis and outside the vascular tissue that consists of parenchyma cells and is the site of lateral root formation.
Petal
A flower structure that can protect the surrounding reproductive components or can attract insect pollinators.
Petiole
Modified stem tissue that supports a simple or compound leaf and contains the vascular bundles.
Phenotype
The morphological, physiological, biochemical, behavioral, and other properties of an organism that develop through the interaction of genes and environment. (See genotype.)
Phylogenetic
Pertaining to the evolutionary history of a particular group of organisms.
Phylum
In taxonomy, a high-level category just beneath the kingdom and above the class; a group of related, similar classes.
Pistil
Female reproductive structure that consists of the stigma, style, and ovary. It is sometimes called the gynoecium.
Pith
Central tissue of stems and roots.
Plant Variety Protection
In the US, the Plant Variety Protection Act provides patent-like protection for sexually (i.e., seed) reproduced plants, other than fungi or bacteria, and to crops reproduced by tubers. The variety must be distinct from all other varieties, uniform, and stable.
Pleiotropy
The effect of a single gene on more than one trait.
Plumule
The embryonic shoot
Pollination
Fertilization of the embryo by pollen.
Polyploid
An individual that carries more than two complete sets of homologous chromosomes.
Population
A group of individuals with common ancestry that are much more likely to mate with one another than with individuals from another such group.
Predator Control
A predator-prey interaction in which the predator controls the prey population size; that is, in which the predator population is the limiting factor for the prey population size.
Primary [or natural] forest
A forest largely undisturbed by human activities.
Primary Productivity
The transformation of chemical or solar energy to biomass. Most primary production occurs through photosynthesis, whereby green plants convert solar energy, carbon dioxide, and water to glucose and eventually to plant tissue. In addition, some bacteria in the deep sea can convert chemical energy to biomass through chemosynthesis. Primary production refers to the amount of material produced. Net primary production is the measure of the actual accumulation of biomass after some of the products of photosynthesis (or chemosynthesis) are expended for the plant's own maintenance. Productivity, or the rate of production, is affected by various environmental factors, including the amount of solar radiation, the availability of water and mineral nutrients, and temperature.
Primary Tiller
A tiller produced by a node on the main stem.
Protected Area
A legally established land or water area under either public or private ownership that is regulated and managed to achieve specific conservation objectives.

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Q

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R

Rachilla
The supporting stem-like structure of the spikelet.
Rachis
The central axis of a raceme or spike.
Radicle
The embryonic root; the first structure to emerge during seed germination
Raphe
A seed surface ridge found in some dicots
Recalcitrant Seed
Seed that does not survive drying and freezing.
Recepticle
Enlarged portion of the pedicel at the base of the flower.
Recessive
The member of an allelic pair that is not expressed when the other, dominant allele is present on the homologous chromosome.
Rehabilitation
The recovery of specific ecosystem services in a degraded ecosystem or habitat.
Restoration
The return of an ecosystem or habitat to its original community structure, natural complement of species, and natural functions.
Rhizome
A horizontal, underground stem.
Root Cap
Dead plant cells at the end of the root which serve protective and lubricative functions.
Root Hairs
Short-lived extensions of root epidermal cells that increase the absorptive capacity of the root system by 20 to 30%.

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S

Scutellum
The modified cotyledon structure found in monocot seeds that absorbs food reserves from the endosperm and transports it to the embryo.
Secondary Tiller
A tiller produced by a primary tiller.
Seed
A mature ovule with its normal coverings. A seed consists of the seed coat, embryo, and in certain plants, an endosperm.
Seedbank
A facility designed for the ex situ conservation of individual plant varieties through seed preservation and storage.
Selection
Natural selection is the differential contribution of offspring to the next generation by various genetic types belonging to the same populations. Artificial selection is the intentional manipulation by man of the fitness of individuals in a population to produce a desired evolutionary response.
Seminal Roots
The roots originating from the seed.
Sepal
Small flower structure below the outermost whorl of petals.
Sexual Reproduction
Reproduction involving the union of gametes.
Sheath
One of the two parts of a monocot leaf consisting of tissue arising from each node that is folded around the stem.
Species
A group of organisms capable of interbreeding freely with each other but not with members of other species.
Species Diversity
A function of the distribution and abundance of species. Approximately synonymous with Species Richness. In more technical literature, includes considerations of the evenness of species abundances. An ecosystem is said to be more diverse, according to the more technical definition, if species present have equal population sizes and less diverse if many species are rare and some are very common.
Species Richness
The number of species within a region. A term commonly used as a measure of Species Diversity, but technically only one aspect of diversity.
Sperm
A male gamete; it is usually motile and smaller than the corresponding female gamete.
Spikelet
A monocot inflorescence component that consists of two glumes, one or more florets, and the rachilla.
Spongy Mesophyll Parenchyma
Internal leaf cells that are frequently lobed and are separated by intercellular spaces stages of development.
Spores
A reproductive cell or aggregation of cells capable of developing directly into a gametophyte or other body without uniting with another cell;sexual spores formed as a result of meiosis occurring are often called meiospores; spores produced by mitosis may be referred to as vegetative spores.
Spore Mother Cells
A diploid cell that becomes four haploid spores or nuclei as a result of undergoing meiosis.
Sporophyte
The diploid (2n) spore-producing phase of the life cycle of an organism exhibiting Alternation of Generations.
Stability
A function of several characteristics of community or ecosystem dynamics, including the degree of population fluctuations, the community's resistance to disturbances, the speed of recovery from disturbances, and the persistence of the community's composition through time. Also refers to a cultivar's capacity to maintain high yield potential across a range of environments.
Stamens
Male reproductive structures of a flower composed of filaments and anthers. It is also referred to in the literature as the androecium.
Standard Wings & Keel
The specialized petals of the five-part corolla found in the Fabaceae (Leguminosae) family.
Stele
Root tissue composed of the xylem, phloem, and pericycle.
Stigma
Female reproductive structure that receives/collects pollen.
Stipules
A pair of bracts at the base of the petiole that protects the axillary bud.
Stolon
A horizontal stem (runner) that grows along the ground surface; it may form adventitious roots and plantlets.
Stomata
Pores in the leaf epidermis that allow carbon dioxide to enter and water vapor to leave.
Style
Female reproductive structure that connects the stigma to the ovary; the pollen tube must pass through this tissue to reach the eggs in the ovary.
Subspecies
A subdivision of a species; a population or series of populations occupying a discrete range and differing genetically from other subspecies of the same species.
Succession
The more or less predictable changes in the composition of communities following a natural or human disturbance. For example, after a gap is made in a forest by logging, clearing, fire, or treefall, the initial (or "pioneer") species are often fast-growing and shade-intolerant. These species are eventually replaced by shade-tolerant species that can grown beneath the pioneers. If a community is not further disturbed, the outcome of the successional sequence may be a so-called climax community whose composition is unchanging. In practice, many communities are frequently disturbed and may never reach a climax composition.
Sustainable development
Development that meets the needs and aspirations of the current generation without compromising the ability to meet those of future generations.
Systematics
The study of the historical evolutionary and genetic relationships among organisms and of their phenotypic similarities and differences.
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T

Tap Root System
The primary root (radicle) is dominant in relation to those of its secondary and tertiary branches.
Taxon (pl. taxa)
The named classification unit (e.g. Homo sapiens, Hominidae, or Mammalia) to which individuals, or sets of species, are assigned. Higher taxa are those above the species level.
Taxonomy
The naming and assignment of organisms to taxa.
Tertiary Tiller
A tiller produced by a secondary tiller.
Tiller
A shoot that arises from buds at the base of a plant.
Transformation
The directed modification of a genome by the external application of DNA from a cell of a different genotype.
Trophic Level
Position in the food chain, determined by the number of energy-transfer steps to that level.
Tuber
An enlarged underground stem tip having numerous buds or eyes and used for food storage.

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Utility Patent
Provides patent protection for plant varieties, traits, parts, and processes.
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Variety
Often used as a synonym for Cultivar. A variety in the botanical sense is a subtaxon to a species.
Vascular Plants
Plants with a well-developed vascular system that transports water, minerals, sugars, and other nutrients throughout the plant body. Excludes the bryophytes: mosses, hornworts, and liverworts.
Venation
The arrangement of leaf veins which may be parallel, the main veins run side by side from the base to the apex without branching or intersection, or net, with veins arranged in all directions with branching and intersecting.

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Zygote
The product of the union of two gametes.
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