Glossary

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Glossary Entries

Word(s)	Definition	Image	Caption	Link	Source
Accessory pigments	Light-absorbing pigments, other than chlorophyll, that are found in chloroplasts.
Accessory tissues	Tissue of the fruit that is from non-carpel origin, usually in epigynous and perigynous flowers. E.g. the flesh of an apple is hypanthium tissue and the ovary is the papery core that encloses the seed.
Adhesion	A force where dissimilar molecules stick together; in plants this force of adhesion between water and the walls of the xylem helps hold the water in the xylem against the downward force of gravity.
Adventitious	Tissue arising from an organ other than expected.
Adventitious roots	Roots that emerge from the stem rather than roots.
Aggregate fruit	Fruit formed from the ripened ovaries present in one flower with numerous simple carpels.
Aggregates	"Clumps" in the soil; see soil structure definition.
Agriculture	The science or practice of farming, including cultivation of the soil for the growing of crops and the rearing of animals to provide food, fiber, and other products.
Agronomy	The science and technology of producing and using plants for food, fuel, fiber, and land restoration on an extensive scale. The value per acre is lower than for a typical horticultural crop.
Alternate leaves	Leaves are attached on alternate sides as they go up the stem.
Alternation of generations	Cycle of diploid, asexual, vegetative generation alternating with the haploid, sexual generation.
Anaphase	Third phase of mitosis; the sister chromatids separate (now chromosomes) and the centromeres divide, pulling the chromosomes to opposite poles.
Androecium	One of the whorls of a flower and is all of the male reproductive parts; stamens.
Angiosperms	Group of flowering plants whose seeds develop inside an ovary.
Annual plant	Plant that is produced from seed in the spring and dies at the end of the growing season.
Annual rings	The demarcation between small-celled later summer and large-celled spring secondary xylem.
Antenna complex	Structure of chlorophyll and accessory pigments that are embedded in the thylakoid membranes; it captures and routes energy from sunlight to a collector called a reaction center.
Anther	The pollen-bearing component of the stamen.
Anthocyanin pigments	Red pigments that are produced primarily in the autumn in response to bright light and excess plant sugars in leaf cells.
Anticlinal division	The type of cell division where the new cells have divided so that the wall of the cells is perpendicular to the outside of the stem.
Antipodal cells	Three cells sequestered at the opposite end of the mature female gametophyte from the egg and synergid cells.
Apex	Tip of the stem.
Apical bud	Bud located on the tip of the stem.
Apical meristem	Group of more or less continually dividing cells located at the tip of a shoot or root.
Apomixis	A form of clonal reproduction where vegetative cells in the flower develop into zygotes to form seeds.
Apoplast	Space outside the cell membrane where water and minerals can move freely. It is interrupted by the casparian strip in roots.
Approach graft	A type of grafting where two independent plants are grafted together and severed only once the graft has "taken."
Asexual propagation	A form of propagation that results in plants with identical genetics to the parent plant.
ATP	A principle molecule for storing and transferring energy in cells; it is created in the LR.
Axil	Upper angle between a lateral structure and the stem to which it is attached.
Axillary bud	Bud borne in the axil of a stem.
Axillary meristem	Group of more or less continually dividing cells located at the axils of a stem.
Bark	All of the tissues exterior of the vascular cambium, which includes the primary and secondary phloem, phelloderm (if present), cork cambium, and cork.
Basal root	Root that emerges from the region just above where the main stem stops and the root begins.
Bi-parental cross	Cross between two different plants.
Binomial nomenclature	System of naming in which two terms are used to denote a species of living organism, the first one indicating the Genus and the second the Specific Epithet.
Bisexual	The term used for a flower that has both the androecium and gynoecium; also called hermaphroditic or a perfect flower.
Bract	A modified leaf or scale, usually small, with a flower or flower cluster in its axil.
Branch	Vegetative growth coming from a node on the main stem.
Bridge graft	A type of repair graft used when a plant has been girdled; scion pieces are inserted above and below the girdled site and act to repair the disruption of the cambium.
Bud	Immature vegetative or floral shoot or both, often covered by scales; also called a meristem.
Budding	It is a form of grafting where a single scion is used rather than an entire stem.
Bulb	A specialized, underground organ with a short, fleshy basal stem enclosed by thick, fleshy scales modified for storage.
Callus	A growing mass of unorganized parenchyma cells produced in response to wounding.
Callus bridge	Parenchyma cells that lie between the cambium of the rootstock and the scion and differentiate into cambium cells.
Calyx	One of the whorls of a flower and is located at the base of the receptacle and contains all the sepals.
Cambium	Lateral meristem in vascular plants, including the vascular cambium and cork cambium, that forms parallel rows of cells resulting in secondary tissues.
Carbohydrates	One of the three major types of nutrients found in seeds; they provide energy in the form of starch and sugar.
Carotenoid pigments	Yellow and orange pigments that are present in the leaf all growing season, but during the warm part of the season these colors are hidden by the high concentration of green-colored chlorophyll. They take longer to break down than chlorophyll.
Carpel	Composed of three parts: stigma, style, and ovary.
Casparian strip	A band-like deposit of waterproof suberin that wraps around each cell in the endodermis and forces water to move through the cells rather than the intercellular spaces.
Cell cycle	Cycle in which cells go through in their lifetime; it consists of interphase and mitosis.
Cell division	The process in mitosis where one plant cell divides into two identical cells.
Cell membrane	Made up of layers of protein and lipid (fats and oils are examples of lipids) and is semi-permeable, meaning that it allows select compounds in and out, but blocks other types of compounds.
Cell wall	A rigid membrane that contains cellulose (a carbohydrate that is indigestible for humans) and is the outer covering of the cell.
Cellulose	Main constituent of the cell wall and is key to a plant's structural integrity; it is a long chain of glucose. It sequesters atmospheric CO2 for long-term storage.
Centromere	Constricted spot where the sister chromatids attach.
Chasmogamy	When the anther matures after the flower opens and pollen is shed before the stigma becomes receptive; it's common in non self-pollinating crops.
Chiasma	Point where sister chromatids of homologs lay over each other forming an "X" shape.
Chimera	When two different genotypes are growing on a single plant.
Chlorophyll	Green photosynthetic pigment found in plants, algae, and cyanobacteria that captures light for photosynthesis.
Chlorophyll a	Type of chlorophyll; it mainly absorbs violet and red light while reflecting green light.
Chlorophyll b	Type of chlorophyll; it mainly absorbs blue and orange light while reflecting green light.
Chloroplast	An organelle that contains chlorophyll where light energy is captured and where the first steps are taken in the chemical pathway that converts the energy in light into forms of energy that the plant can transport and store, like sugar and starch.
Chromoplasts	Cellular organelles that contain types and colors of pigments other than the chlorophyll found in chloroplasts.
Chromosome	Structure within the nucleus of a cell that contains the genes; it is made-up of DNA that has looped around histone proteins then coils and folds.
Class	Taxonomic rank below Division and above Order.
Clay	Smallest particle in soil and has high nutrient holding capacity.
Cleft grafting	A form of grafting where the rootstock is much larger than the scion; both are dormant.
Cleistogamy	When the anther matures, pollen is shed, and the stigma is receptive before the flower opens; it's common in self-pollinating crops.
Cohesion	A force where similar molecules stick together; in plants this occurs with water molecules bonding together.
Coleoptile	Protective sheath that covers in the plumule and epicotyl in the Poaceae family.
Coleorhiza	Protective sheath that covers the radicle in the Poaceae family.
Collenchyma	An elongated cell type with thicker walls and usually arranged in strands; provide support.
Companion cells	Associated with sieve tube members (direct the metabolism) and contain a nucleus (alive).
Complete flower	Where all four whorls are present: calyx, corolla, androecium, & gynoecium.
Compost	A type of organic matter that builds soil structure and assists in retaining moisture and nutrients.
Compound inflorescence	Inflorescence with a group of flowers and includes a rachis.
Compound leaf	Leaf with a blade margin that is completely interrupted and segmented into separate leaflets.
Control	Used to verify or regulate a scientific experiment by conducting a parallel experiment or by comparing with another standard
Conventional crop	Crop that is not GMO and all of its genes originated from sexual reproduction.
Cork	The outer protective tissue of bark; also called phellem.
Cork cambium	A lateral meristem that is responsible for secondary growth that replaces the epidermis in roots and stems; also called phellogen.
Cork cells	The cells located in the cork that are lined with suberin and are dead at maturity.
Corm	A condensed stem, storage organ, typically grown underground and covered in scale leaves.
Corolla	One of the whorls of a flower consisting of all the petals.
Cortex	Also known as the ground meristem, is found just inside the epidermis and extends toward the interior of the stem and root, and is made up of three types of cells: parenchyma, collenchyma, and sclerenchyma.
Cotyledon	An embryonic leaf in seed-bearing plants, one or more of which are the first leaves to appear from a germinating seed.
Cotyledonary node	Food storage structure used in germination.
Cover cropping	Crop used to benefit the soil rather than the main crop species.
Crossing over	Exchange of arms of DNA between sister chromatids of homologous chromosomes that can take place at the point of chiasma formation.
Crown	Compact stem tissue at or near the soil surface.
Cultivar	A plant variety that has been produced in cultivation by selective breeding. The term comes from combining the words 'cultivated' and 'variety'.
Cuticle	Protective waxy coating of cutin on epidermis cells that restricts water loss.
Cutin	Water-resistant substance that coats the wall of the cell exposed to the environment and helps limit the loss of water that is inside of the plant to the atmosphere.
Cytokinesis	Occurs directly after telophase; the cell plate forms between the two daughter cells and the cell walls separate the newly formed cells.
Cytoplasm	The fluid inside the cell membrane in which the organelles and other plant cell parts are suspended.
Dehiscent	Used to categorize fruits with seeds that separate from a dried pericarp.
Demonstration experiments	A very valuable method for actively learning the body of scientific knowledge that has been previously discovered and communicated by others; and it is specifically orchestrated for teaching and learning, not for the discovery of new information about the world around us.
Derivative (cells)	Other sister cells that, after the initial meristematic initial cells are created, divide once or twice more and then differentiate.
derivative cells
Dermal tissue	It is on the outside of the plant and provides protection for the plant cells they surround.
Dermal tissues
Determinate	When the stem of a plant terminates in a flowering stalk and new stem growth continues from subterminal lateral buds.
Dicotyledon (dicot)	Seed plant that produces an embryo with paired cotyledons, floral organs arranged in cycles of four or five, and leaves with net-like veins.
Differentiation	Process by which cells or tissues undergo a change toward a more specialized form or function.
Dioecious	When an entire plant has only male or only female flowers; means two houses.
Diploid	Term used for zygote cells, where the cell has two sets of chromosomes; abbreviated 2n.
Discovery experiments	Focus on uncovering new relationships and solving problems, follow scientific method, test hypotheses and their predicted outcomes, and utilize a careful design in order to maintain meaningfulness and credibility.
Division	Highest taxonomic category, consisting of one or more related classes, and corresponding approximately to a Phylum in zoological classification.
DNA	Basic biochemical compound that makes up the gene.
Dominant allele	When one allele is expressed over the other alleles present.
Dormant/Dormancy	Term used when seeds are alive and don't germinate when provided with favorable conditions for germination.
Double fertilization	Where one haploid male sperm cell fuses with the female haploid egg cell to form the diploid zygote, and the second haploid male sperm cell fuses with two egg cells to form a triploid endosperm.
Ecodormancy	When external factors, usually environmental, prevent a seed from germinating.
Emasculate	Act of removing the anthers before pollen has been shed from a flower that is used as the female in breeding; used to reduce self-pollination when wanting to cross.
Embryo	Nascent (new, young) plant resulting from the combination of genes from the male sperm transmitted by the pollen to the female egg held in an ovule in the ovary.
Embryo axis	Embryonic root and shoot.
Emergence	Germination, when the embryo becomes active and the radicle grows through the seed coat.
Endocarp	Inner layer of the pericarp.
Endodermis	The innermost cells of the cortex.
Endodormancy	Internal factors within the seed prevent germination.
Endosperm	Tissue that results from the second haploid male sperm cell fusing with two egg cells during fertilization.
Epicotyl	Portion of the stem of a seedling or embryo located between the cotyledons and the first true leaves.
Epidermis	The outermost layer of cells in the plant.
Epigeal	Type of seedling emergence where cell division in the hypocotyl is initially more active and rapid than cell division in the epicotyl. Cotyledons are brought above the soil surface as the hypocotyl expands.
Epigynous	When the perianth and androecium is positioned above the ovary; also called an inferior ovary.
Evaluation experiment	Typically used during the development of new technologies to identify the best products for the desired purpose (eg. which pesticides are effective against the target insect, but not harmful to non-target insects), but are not used to discover new knowledge about how the world works so they typically don't advance our understanding of the natural world. Used to pick a winner from among a number of options.
Evapotranspiration	Movement of water in the plant from the root through the stem to the leaf and out the stomata to the atmosphere; also called transpiration.
Exocarp	Outer layer of the pericarp.
Experimental design	Process of planning an experiment to test a hypothesis.
Experimental unit	The entity to which a specific treatment combination is applied.
Exploration experiments	Focus on detailed observation of organisms and habitats, increase our information about the natural world, identify potential relationships that need to be tested, and are essential to sound and testable hypothesis-building.
Exponential spread	Very rapid spread of an invasive plant as numbers and reproductive rates accelerate.
Family	Taxonomic rank below Order and above Genus.
Fascicular cambium	The cambium within the vascular bundle.
Fertilizer analysis	N-P-K content of a bag of fertilizer; it is shown in percentages by weight.
Fibrous root	Root system where the radicle grows and then rapidly slows or completely halts in growth. Once this happens roots will emerge above the radicle and from the stem tissue located below the soil.
Filament	The stalk that holds up the anther so that pollen grains can be effectively released.
Floret	Single flower in a compound inflorescence.
Floriculture	Discipline of horticulture concerned with the production and marketing of plants valued for their flowers.
Flower	Reproductive structure in a flowering plant.
Forestry	The science or practice of propagating, planting, managing, and caring for forests, which includes harvesting.
Fructose	Simple sugar; it can be produced via photosynthesis.
Fruit	Ripened ovary together with the seeds within the ovary.
Funiculus	Stalk that connects either an ovule or a seed to the placenta.
G1 stage of interphase	First stage of interphase; "G" stands for Gap/Growth.
G2 stage of interphase	Third and final stage of interphase; "G" stands for Gap/Growth.
Gas exchange	Movement of oxygen and carbon dioxide through stomata in the plant.
Generative nucleus	Nucleus in the immature male gametophyte that will later divide by mitosis to produce two sperm cells.
Genes	Hereditary units consisting of a sequence of DNA that occupies a specific location on a chromosome (locus) and determines a particular characteristic in an organism. Genes undergo mutation when their DNA sequence changes.
Genetic code	Order of the four different combinations of the bases in DNA; AT, TA, GC, or CG.
Genetic engineering	Manipulation and introduction of a transgene into a plant for a specific trait.
Genetic pollution	Where genes from GMO crops may escape to conventional crops or weedy relatives.
Genotype	Genetic composition of an organism.
Genus	Group of species possessing fundamental traits in common but differing in other lesser characteristics. The taxonomic rank below Family and above Specific Epithet.
Geophyte	New growth begins underground and the function of the underground growth is storage of food, nutrients, and water during adverse environmental conditions.
Glucose	A simple sugar; it can be produced via photosynthesis.
GMO	Genetically engineered organism or a plant containing a transgene.
Graft union	Location where the rootstock and scion meet.
Grafting	Art and science of connecting two pieces of living plant tissue together in such a manner that they will unite and subsequently grow and develop into one composite plant.
Grana	Stacks of thylakoids.
Granular aggregation	Interaction of small soil aggregates; it is important to have a mixture of large and small holes between the aggregates to allow for water and gas exchange.
Gravitropism	Growth in response to gravity.
Green manure	Crop grown to purposefully be tilled back into the soil to increase the organic matter (and thus change the soil structure). They can also smother weeds.
Ground meristem	The new, primarily parenchyma, cells lying between the protoderm and procambium that will mature to become the cortex tissue.
Guard cells	Located on the epidermis and regulate the size of the stomata.
Guttation	Dew-like drops of water that are forced out of the leaves of some plants due to root pressure.
Gymnosperms	Group of plants whose seeds are produced without the protection of an ovary.
Gynoecium	One of the whorls of the flower and is all of the female reproductive parts; carpels.
Haploid	Term used for gamete cells that typically contain one set of each of the chromosomes; abbreviated n.
Heartwood	The older, darker xylem in the stem that is clogged with resins that limit the transport of water.
Herbaceous	Plants whose above-ground parts die back to the soil surface at the end of the growing season.
Herbaceous annual	Plants that completely die over winter. These plants complete their life cycle from seed to flower to seed in one year.
Herbaceous perennial	Plants where only the above-ground growth dies over winter. The underground portion lives for more than two growing seasons (two years).
Heritability	Measurement of a quantitative trait that passes from parent to offspring and is measured in high and low; high being very similar between parent and offspring and low being dissimilar between parent and offspring.
Hermaphroditic	The term used for a flower that has both the andreocium and gynoecium; also called a perfect flower or bisexual.
Heterozygote	Plant with two different alleles of a particular gene and gives rise to varying offspring; offspring are generally more vigorous than offspring from homozygote.
Hierarchy	System of grouping where each classification is a subset of a superior grouping, and may contain subordinate categories.
Histone protein	Protein around which the DNA surrounds.
Homologous chromosomes (homologs)	Matching chromosomes from the two different sets; they carry the genetic information that affects the same characteristic or function at the same location on the chromosome; from the sperm and egg cells.
Homozygote	Plant with identical alleles of a particular gene and give rise to identical, or nearly identical, offspring.
Horticulture	The art and science of the development, sustainable production, marketing, and use of high-value, intensively cultivated food and ornamental plants.
Humus	Sticky material made from organic matter that helps bind soil particles together into aggregates; it can absorb and hold up to 6x its weight in water, it releases nitrogen, and holds positively charged cations for plant growth.
Hydrogen bond	When water molecules are near each other and the negative region of one molecule is attracted to the positive region of another; it is a weaker bond than covalent bonds.
Hypocotyl	Embryonic shoot below the cotyledons.
Hypocotyl roots	Roots that emerge above the basal roots.
Hypogeal	Type of seedling emergence where the cotyledons remain below the surface of the ground.
Hypogynous	When the perianth and androecium are attached below the ovary; also called a superior ovary.
Hypothesis	Scientific means of forming a question or proposed explanation made on the basis of limited evidence as a starting point for experimentation. In science, it is a testable statement.
Imbricate bulb	Underground storage organ formed primarily of modified leaves (scales) without a papery covering. Individual scales do not encircle the entire bulb.
Imperfect flower	The term used for flowers that have only the androecium OR only the gynoecium present.
imperfect flowers
Inbreeding	Producing seed by selfing over 5-7 generations to develop pure lines.
Incomplete flower	The term used for flowers missing one or more of the four whorls.
Indehiscent	Used to categorize fruits with seeds that are retained within the dried pericarp.
Indeterminate	When the apical meristem remains a vegetative meristem that is capable of forming new nodes and internodes throughout the season. Once the hormonal signals are right, reproductive axillary meristems at the nodes below the apical meristem produce inflorescences.
Inferior ovary	When the perianth and androecium is positioned above the ovary; also called an epigynous flower.
Inflorescence	Complete flower structure of a plant and includes the flower, pedicle, rachis, and peduncle.
Initials (cells)	Meristem cells that remain meristematic because they continue to initiate new cells.
Integument	Cells that form the ovary wall. Nucellus cells on the interior of the ovule wall develop into megaspore mother cells.
Interfascicular cambium	The cambium between the vascular bundles.
Internode	Stem region between nodes in plants.
Interphase	One of the two major parts of the cell cycle and consists of G1, S, & G2 stages.
Invasive plant	Plant that is non-native to an ecosystem, and whose introduction causes or is likely to cause economic or environmental harm or harm to human health.
Kinetochore	Point of attachment of the spindle and the centromere.
Lag phase	Phase during invasive plant spread that is slow due to a low number of plants being introduced.
Lamina	Another name for a leaf blade.
Lateral meristem	Specialized meristems that are made-up of cells that undergo mitotic cell division.
Lateral or secondary roots	Roots that extend horizontally from the primary root and serve to anchor the plant securely into the soil. This branching of roots also contributes to water uptake, and facilitates the extraction of nutrients required for the growth and development of the plant.
Leaf	A usually green, flattened, lateral structure attached to a stem and functioning as a principal organ of photosynthesis and transpiration in most plants.
Leaf axil	Upper angle between a leaf petiole and the stem to which it is attached.
Leaf blades	Broad portion of a leaf and does not include the petiole.
Leaf margin	Edge of the leaf blade.
Leaf primordia	Young leaves, recently formed by the shoot apical meristem, located at the tip of a shoot.
Leaf scar	Mark indicating the former place of attachment of petiole or leaf base.
Leaf sheath	Structure where the blade attaches to an envelope of leaf tissue that wraps around the shoot of the plant and attaches to a lower node on the stem.
Leaflet	Small leaf-like structure that is found on compound leaves. Multiple leaflets make-up a single compound leaf.
Lenticel	Small opening in the cork of woody stems that allows for gas exchange.
Light absorption	Process in which light is absorbed and converted to energy.
Light Independent Reaction	Second half-reaction in photosynthesis and occurs without the presence of light and uses the energy produced in the Light Reaction to grab the carbon from carbon dioxide and use the carbon to build simple sugars; abbreviated LIR.
Light reaction	First half-reaction in photosynthesis and occurs with the presence of light and uses light energy to split water, which transforms the energy from the sun into hydrogen ions and electrons; abbreviated LR.
Light reflectance	Light wavelengths that are not absorbed, but are reflected back.
Light wavelength	Length of the wave from one peak to the next; it is measured in nanometers.
Linkage	When two genes are on the same chromosome.
Lipids	Compact plant oils that store energy; also called triglycerides.
Locule	A chamber in the ovary.
Locus	Location on a chromosome where a particular gene is found.
Megaspornatium	Place in the ovary where the female gametophyte will be formed.
Mendel’s First Law - the law of segregation	Principle that during gamete formation each member of the allelic pair separates from the other member to form the genetic constitution of the gamete e.g. Ss diploid produces S and s gametes.
Mendel’s Second Law - the law of independent assortment	Principle that during gamete formation the segregation of the alleles of one allelic pair is independent of the segregation of the alleles of another allelic pair.
Meristem	Group of continuously dividing cells; also called a bud.
Mesocarp	Middle layer of the pericarp.
Mesophyll	The site of most photosynthesis reactions in the leaf and is located in the middle layer of the leaf.
Metaphase	Second stage of mitosis; the spindle fibers grow and form attachments to the pairs of sister chromatids at the centromeres.
Metaphase plate	Equatorial plate which is formed along the midline of the cell between the poles.
Microsporangium	Place in the anther where the male gametophyte will be formed.
Middle lamella	A material containing pectin that forms between cells and that cements the cell wall of one cell to the cell wall of an adjacent cell.
Midrib	Main vein, generally in the center of the leaf from which secondary veins emerge.
Mitochondria	An organelle where the stored sugars are metabolized to produce forms of energy that the plant can use for growth. It is the cell's power plant.
Mitosis	Cell division where a cell divides into two identical daughter cells.
Monocotyledon (monocot)	Seed plant that produces an embryo with a single cotyledon and parallel-veined leaves; includes grasses, lilies, palms, and orchids.
Monoecious	When an entire plant has both male and female parts (can be perfect or imperfect); means one house
Multiple fruit	Fruit formed from the ripened ovaries from a cluster of flowers that are in close proximity in an inflorescence that coalesce into one unit.
NADPH	Energy created in the LR and is used to drive the LIR.
Nitrogen	One of the most important elements for plant growth (by quantity); it is a key element found in protein; abbreviated N.
Node	Stem region of a plant where one or more leaves attach and is the location of lateral buds.
Nomenclature	Formal system of names attached to the taxonomic groupings.
Nucleosome	Made up of eight histone proteins and is wrapped by a segment of DNA.
Nucleus	An organelle that contains the chromosomes. Chromosomes contain the genetic code that is carried within each cell and that directs which chemical reactions are turned on and off in the cell.
Olericulture	Discipline of horticulture concerned with the production and marketing of plants or plant parts valued for culinary use as vegetables.
Opposite leaves	Where the leaves grow directly opposite each other on the stem.
Order	Taxonomic rank below Class and above Family.
Organelle	The generic term for a plant organ.
Organic material/matter	Material that has come from a recently living organism (such as plants) that may be partially or fully decomposed.
Organic molecule	Chemical compound associated with living organisms that contain carbon atoms.
Ovary	Part of the carpel and contains ovules which develop into seeds.
Ovary wall	Provides protection to the ovules; also called the pericarp.
Ovule	The part of the ovary that contains an embryo sac and is surrounded by the nucellus, which develops into a seed after fertilization.
Palisade mesophyll	The densely packed, columnar-shaped, elongated cells full of chloroplasts. It is analogous to cortex parenchyma cells in the stem, but in the leaf are specialized for light energy capture.
Palmate venation	Where several veins radiate from the point where the petiole attaches to the blade. The veins fork, then travel a bit, then fork again, travel, fork and so on until the veins reach the margin of the leaf.
Palmately compound leaf	Compound leaf where the petiolules of the leaflets connect directly to the petiole (no rachis).
Parallel venation	Distribution or arrangement of a system of veins in a leaf blade in a non-intersecting network. The veins are parallel to each other and the long edge of the leaf.
Parenchyma	A cell type with thin cell walls, is unspecialized but carries on photosynthesis and cellular respiration and can store food, and form the bulk of the plant body.
Pedicel	Short stalk that holds up the flower.
Peduncle	Large, central stalk that attaches the rachi to the stem of the plant.
Perennial	Plant that lives for more than two growing seasons (more than two years); perennials may be woody or herbaceous (the latter with underground perenniating structures).
Perfect flower	Term used for a flower that has both the andreocium and gynoecium; also called hermaphroditic or bisexual.
Perianth	Both the calyx and corolla.
Pericarp	Ripened ovary wall and it is made-up of three parts: exocarp, mesocarp, and endocarp.
Periclinal division	Type of cell division where the new cells are formed either to the outside or inside and the cell wall that separates the two new cells is parallel to the outside of the stem.
Pericycle	A single layer of tightly packed cells located in the vascular cylinder that retain the ability to divide and produce new cells. This layer of cells is the source of lateral roots.
Periderm	Consists of the cork cambium, phelloderm, and cork.
Perigynous	When the ovary is surrounded by the fused bases of the perianth and androecium.
Petals	Modified leaves that make-up the corolla; they are showy and attract pollinators.
Petiole	Stalk by which most leaves are attached to a stem; it is part of the leaf structure, not the stem.
Petiolule	Stalk that connects the leaflet to the top of the petiole.
Phellem	Another name for cork.
Phelloderm	New cells that are laid down toward the inside of the stem or root by the cork cambium.
Phellogen	Another name for cork cambium.
Phenotype	Physical appearance of an organism.
Phloem	Tissue consisting of sieve tube and companion cells in the vascular system of plants that moves dissolved sugars and other products of photosynthesis from the leaves to other regions of the plant.
Phosphorus	One of the most important elements for plant growth (by quantity); it is a key component in energy transfer molecules like ATP and as part of the DNA backbone; abbreviated P.
Photoautotrophs	Name given to living things, namely plants, that use energy from light to produce organic molecules with which they build their cells and store energy; they are self-nourishing.
Photon	Particle representing a quantum of light; they provide the energy that drives photosynthesis.
Photosynthesis	Process of capturing light energy and producing carbon-based organic molecules.
Phylum	Taxonomic rank below Kingdom and above Class, used in zoological classification.
Pinnate venation	Type of webbed venation where there is a strong midrib and the secondary veins fan out opposite of each other.
Pinnately compound leaf	Compound leaf where the leaflets are arranged opposite of one another on the rachis.
Pistil	Term used when several carpels are fused together.
Pistillate flower	When an imperfect flower only contains the gynoecium.
Pith	Occupies the central part of the stem and is composed of thin-walled parenchyma cells often with larger intercellular spaces than you would find in the cortex.
Placenta	Part of an ovary where the funiculus attach.
Plant tissue culture	Method that uses synthetic growth media to provide the environment for mitotic cell divisions of plants and is used to regenerate a single cell into a whole plant.
Ploidy	Number of sets of homologous chromosomes in a cell.
Plumule	First true leaves of the plant and emerge from the seed, rise above the soil surface, and start to collect energy from the sun.
Polar nuclei	Two haploid nuclei contained within one cell membrane in the mature female gametophyte. One sperm cell will unite with these two polar nuclei to establish the triploid endosperm tissue.
Pomology	Production and marketing of plants or plant parts valued for their culinary use as fruits including nuts); propagated by cuttings, grafting (asexual propagation).
Potassium	One of the most important elements for plant growth (by quantity); it is a key part of the mechanism for moving nutrients into and out of cells; abbreviated K.
Primary (cells)	Term used for the cells that originate from cell divisions of the apical meristem
Primary growth	Growth that results from activity by an apical meristem; causes the elongation of the cells in the apical meristem region, which leads to increasing plant length.
Primary meristem	Apical meristems on the shoot and root apices in plants that produce plant primary tissues.
Primary phloem	Phloem tissue that results from differentiation of derivative cells (procambium).
Primary root	Root that forms from the embryonic radicle.
Primary xylem	Xylem tissue that results from differentiation of derivative cells (procambium).
Procambium	New cells in the central part of the root that will mature to become the vascular tissue (xylem, phloem, and vascular cambium).
Prop root	Adventitious root that arises from the stem, penetrates the soil, and helps support the stem, as in corn.
Prophase	First stage of mitosis; chromatin begins to coil and condense to form chromosomes.
Protandry	When the pollen is shed before the stigma is receptive.
Proteins	Sources of amino acids for production of enzymes and other nitrogen-rich compounds in the seed.
Protoderm	New, primarily epidermis, cells laid down toward the exterior of the root which will mature to become the root dermal tissue.
Protogyny	When the stigma is receptive prior to the pollen shedding.
Pruning	Cutting away dead, overgrown, or unwanted branches or stems to improve safety, aesthetics, or productivity.
Punnett square	Simple database used to visualize the types of zygotes and their expected frequency that form from male and female gametes.
Pure line	True breeding plant produced by inbreeding so it is homozygous at most loci and produces identical plants by seed.
Purine	Consists of the base pairs Adenine and Guanine and contains two rings of carbon atoms.
Pyrimidine	Consists of the base pairs Cytosine and Thymine and contains one ring of carbon atoms.
Qualitative differences	Large differences that can easily be seen or measured in qualitative terms; e.g. fruit color.
Quantitative differences	Small differences that are measured numerically; e.g. yield in kg/ha. They can be influenced by the environment.
Quiescent	When a seed does not germinate until given proper conditions for germination (oxygen, water, temperature, and sometimes light).
Rachis	Stalk of a flower that is situated between the peduncle and the pedicel.
Radicle	Embryonic root that breaks through the seed coat during germination and develops into the seedling's root system.
Randomization	Act of randomly assigning treatments to experimental units using a random number table or computer-generated randomization to help minimize any bias that has not been recognized in advance and controlled for in other ways.
Reaction center	Complex of pigments, proteins, and other factors that execute the primary energy conversion reactions of photosynthesis, primarily where water is split in the LR to form the energy carriers ATP & NADPH.
Receptacle	Base of the flower where the floral parts are attached.
Recessive allele	Allele(s) that are not expressed if a dominant allele is present; they will be expressed if there is no dominant allele.
Reciprocal cross	Matching cross where the pollinator becomes the female and female of the former cross becomes the pollen donor.
Replication	When the same treatment is applied to more than one experimental unit.
Reproductive meristem	Apical meristem that transforms into the reproductive tissues (the inflorescence) of the plant.
Resonance	Energy that is passed from one molecule to the next.
Rhizome	Horizontal stem growing just below the soil surface.
Ribose-Phosphate backbone	Chain of alternating ribose and phosphate that make-up the sides of the DNA structure.
Root	Organ that anchors the plant into the soil, takes up water and nutrients, and stores food.
Root cap	Thimble-shaped mass of cells that covers and protects the root apical meristem from rocks, dirt, and pathogens.
Root hair	Thin, hairlike outgrowth of an epidermal cell of a plant root that absorbs water and minerals from the soil. Root hairs live for only a few weeks, deteriorate, and are then replaced by fresh root hairs.
Rootstock	Portion of a graft that contains the root system.
Rubisco	One of the most abundant proteins on earth; it catalyzes the step in the process where carbon from atmospheric CO2 is incorporated into an organic molecule; full name: Ribulose-1,5-bisphosphate carboxylase/oxygenase.
S stage of interphase	Second stage of interphase where the chromosomes replicate (DNA replicated).
Sand	Largest particle in soil and helps increase aeration.
Sapwood	Younger, lighter xylem in the stem that is resin-free and transports water up the trunk.
Saturated fatty ­­acids	Fatty acids that have no double bonds in the chain with all carbon atoms in the interior of the chain having 2 attached hydrogen atoms.
Scarification	Process used to break a physical seed dormancy (hard seed coat).
Science	Systematic study of the structure and behavior of the physical and natural world through observation and experiment.
Scientific discovery	Process of scientific inquiry; it builds on what is known by testing hypotheses.
Scion	Portion of a graft that contains the shoot system and all above-ground parts.
Sclerenchyma	A cell type with thickened, rigid, secondary walls that are hardened with lignin and provides support for the plant.
Secondary growth	Production of xylem and phloem from cambium cells.
Secondary phloem	New phloem that is formed on the outside and is produced by the fascicular cambium.
Secondary root	Root that forms off of the primary root.
Secondary xylem	New xylem that is formed on the inside and is produced by the fascicular cambium.
Seed	Ripened ovule containing a seed covering, food storage, and an embryo.
Seed coat	Outer layer of the seed.
Seed germination	Activation of metabolic pathways of the embryo leading to the emergence of a new seedling.
seeds
Self-incompatibility	When there are genetic mechanisms that inhibit self-pollination of a flower.
Self-pollination	When the pollen from the plant pollinates the stigma of the same plant.
Sepals	Outermost whorl of the flower that protects the flower and photosynthesizes.
Sessile	When a leaf lacks a petiole; called a sessile leaf.
Sexual propagation	Form of propagation that results in plants with genetics that differ from the parent plants, also called seed propagation.
Shoot	Made up of a central axis (stem) with a repeating pattern of nodes and internodes.
Sieve tube members	Elongated cells that join end to end to form tubes for passage of liquids. The end walls have pores. Unlike xylem cells, these cells are still alive. They have a thin cell membrane containing a layer of living protoplasm that hugs the wall of the cell.
Silt	Intermediate particle size in soil.
Simple fruit	Fruit formed from a flower with one carpel or multiple carpels fused together so that it looks like just one carpel.
Simple inflorescence	Type of inflorescence with a peduncle, rachis, pedicel, and single flower structure.
Simple leaf	Leaf with an uninterrupted blade margin.
Simple sugars	Monosaccharides; examples include glucose and fructose.
Sister chromatids	The two chromosomes that are exact copies that are created during S stage of interphase.
Soil compaction	When the pore spaces between soil aggregates are compressed.
Soil organic matter	Carbon-based plant, animal, and/or microbe tissues that are in the process of breaking down; increasing soil organic matter improves and stabilizes soil aggregation.
Soil structure	The way in which the soil particles and other materials, like the organic matter in the soil, bind together into clumps.
Soil texture	Relative proportion of sand, silt, and clay particles in the soil.
Somatic cells	Cells of flowering plants, other than the reproductive cells; always 2n.
Specific epithet	Uncapitalized Latin adjective or noun that follows a capitalized Genus name in binomial nomenclature and serves to distinguish a species from others in the same genus, as saccharum in Acer saccharum (sugar maple).
Spindle apparatus	Microtubules associated with movement of the chromosomes during division.
Spongy mesophyll	Loosely packed cells with large air spaces in between the cells, which allows movement and exchange of gases, specifically oxygen, carbon dioxide and water vapor. Spongy mesophyll cells also contain chloroplasts.
Sporangia	Structures in the androecium and gynoecium where meiosis takes place and the gametophyte generation develops.
Spore	Haploid single cell produced by meiosis in the sporangium of a diploid sporophyte.
Stamen	Modified leaf and collectively they make up the androecium. A stamen is made-up of the anther and filament.
Staminate flower	When an imperfect flower only contains the androecium.
Starch	Key energy storage compound in plant cells; it is a long glucose chain; it sequesters atmospheric carbon for short-term use.
Statocytes	Specialized cells that help the plant to sense gravity and grow accordingly.
Stem	Supporting and conducting organ usually developed initially from the epicotyl and growing upward and consists of nodes and internodes.
Stigma	Receptive apex of the carpel of a flower, on which pollen is deposited at pollination.
Stipule	Usually a pair of appendages located at the base of a leaf but may be fused into a ring around the stem; variable in size, shape, and texture; serves for protection or to attract pollinators.
Stolon	Stem with long internodes that grows along the surface of the ground.
Stomate/Stoma/Stomata	Gap in the epidermis that allows gas exchange between the atmosphere and internal parts of the leaf.
Storage root	Root that is modified for storage of nutrients, such as carrots and beets.
Stratification	Process used to break a physiological dormancy, such as embryonic or endo/eco-dormancies.
Stroma	Interior of the chloroplast; it is the site of the LIR
Style	Part of the carpel that elevates the stigma to a position for reception of pollen and is a conduit for pollen tube growth.
Suberin	Impermeable (to water and gases), waxy substance present in the cell walls of corky tissues.
Sucrose	Sugar that is transported by the phloem throughout the plant to provide energy and building blocks for other organic molecules like starch and cellulose.
Super weed	Weed produced by crossing with a GMO crop and inherits the GMO trait, like herbicide tolerance.
Superior ovary	When the perianth and androecium are attached below the ovary; also called a hypogynous flower.
Suspensor	Produced by multiple mitotic cell divisions of the embryo’s basal cell; the suspensor anchors the apical cell of the embryo to the ovule wall.
Symplast	Interior to the cell membrane, where water and minerals are transported through cells.
Synergid cells	Cells flanking the egg cell in the mature female gametophyte.
T-budding	A type of budding performed using dormant scion buds on actively growing rootstocks; typically done in late summer outdoors.
Tap root	Main root of a plant, usually stouter than the lateral roots and growing straight downward from the stem.
Taxonomy	Science of classifying organisms.
Telophase	Fourth and final stage of mitosis; the nuclear membrane forms around the chromosomes in each of the daughter cells.
Tension	Differential pressure; in plants this occurs as water molecules are pulled through the plant via transpiration.
Tepal	When the sepals and petals are showy and indistinguishable.
Terminal bud	Bud located at the apex of a stem.
Tetrads	Groupings of four sister chromatids.
Thylakoid membrane	Membrane that surrounds the thylakoid.
Thylakoids	Membrane-bound compartments inside chloroplasts and cyanobacteria, and are the site of the light-dependent reactions of photosynthesis.
Tillage	Process of incorporating the residue from the top of the soil into the soil; there are many types of tillage.
Tissue	A group of cells that share a function.
Topworking	A type of grafting performed on established orchard trees.
Totipotent	Ability of a single plant cell to grow into a whole plant.
Tracheids	Elongated and narrower than vessels, connected by overlapping at their ends, are dead at maturity, and contain pits through which water can move.
Transformation	Process of using the gene gun or Agrobacterium tumefaciens to introduce a transgene into a plant.
Transformed	Synonym for GMO, or plant carrying a transgene.
Transgene	Gene introduced into a plant from another organism, not through sexual reproduction.
Transgenic	Synonym for GMO, or plant carrying a transgene.
Translocation	Movement of a substance from one place to another.
Transpiration	Movement of water in the plant from the root to stem to leaf and out through the stomata to the atmosphere; also called evapotranspiration.
Treatments	Administration or application of agents to a plant to prevent disease or facilitate growth.
Trichome	Either unicellular or multicellular hair-like outgrowths arising from the epidermis; found on stems.
Trifoliate leaf	Compound leaf with three leaflets that attach to a rachis.
Triglycerides	Another name for lipids.
Triose phosphate	A 3-carbon sugar (triose) with phosphorus and oxygen atoms (phosphate); G3P is an example.
Triploid	Term used for endosperm that has three sets of chromosomes; abbreviated 3n.
Tube nucleus (or vegetative nucleus)	Nucleus in the male gametophyte that is associated with pollen tube growth.
Tuber	Swollen, underground, modified stems that store food.
Tunicate bulb	An underground storage organ formed primarily of modified leaves formed in concentric circles around the active meristem. The bulb is covered with a papery covering.
Turgor pressure	Water pressure inside of cells.
Umbel	Inflorescence with multiple flowers originating from a common point.
Unsaturated fatty acids	Fatty acids that have one or more double bonds between one or more carbon atoms in the chain, lack some hydrogen atoms, and therefore the carbon atoms are not saturated with hydrogen.
Vacuole	An organelle containing various fluids including stored chemical energy like starch and waste products from the cell. The vacuole takes up much of the cell volume and gives shape to the cell.
Vascular bundle	System containing vessels that carry or circulate fluids and dissolved minerals in the plant; composed of xylem, phloem, and bundle sheath cells.
Vascular cambium	Lateral meristem producing vascular tissues.
Vascular tissue	System containing vessels that carry or circulate fluids and dissolved minerals in the plant; composed of xylem, phloem, and bundle sheath cells.
Venation	Pattern of veins on a leaf.
Vessels	Elongated xylem cells that connect end to end to form tubes, are dead at maturity, and have perforated end walls so water can move freely through the holes and flow from cell to cell. Vessels have a relatively large diameter compared to other xylem cells and allow greater movement of water.
Viral coat protein	Protein that surrounds the viral genome, protecting it, and is essential to virus replication.
Whip and tongue graft	A type of graft where both scion and rootstock are dormant and the same diameter; it is much more secure than other types of bench grafts.
Whorl	Node on the receptacle where the four types of modified leaves are attached (four whorls of a flower).
Whorled leaves	Where the leaves are oriented in a whorled formation in which their point of attachment appears to spiral up the stem.
Woody perennial	Plant that lives for more than a year, has hard rather than fleshy stems, and bears buds that survive above ground in winter. Trees, shrubs, many vines, and bamboo are examples of woody perennials.
Xylem	Supporting and water-conducting tissue of vascular plants.
Zone of Differentiation	Area in roots where tissues are formed (expand in width).
Zone of Elongation	Area in roots where recently produced cells grow and elongate prior to differentiation.