Share interesting photos to engage biology enthusiasts.

Botany Terms - Glossary of Botanical Terms

Botany Terms - Glossary of Botanical Terms

Following is the glossary of botanical terms and definitions with a complete compilation of botany terms for your reference.
Priya Johnson
The study of plants and their related structures is what makes up the field of botany. Most plants are self-sufficient, autotrophic organisms. However, there are so many variations that are present even in plants, be it in their structure, size, color, or mode of nutrition. These numerous variations, in their phenotypic (outwardly visible) traits as well as their genotype, has made people study this group since centuries, thus, making botany one of the oldest sciences, rivaling astronomy today. Botany has formed the basis on which, the study of plants and consequently, living organisms was done. It was the plants present in his backyard that inspired Gregor Johann Mendel to propose the first laws of genetic inheritance, that are studied even to this day.
The importance of this science cannot be stressed enough, as today, all living organisms owe their existence to plants, either directly or indirectly. If it weren't for these green beings, we wouldn't have had oxygen to breathe, nor fruits to eat!
Plants are of various types, ranging from edible with medicinal properties, to downright poisonous. It is this very study of plants that forms the crux of this intriguing and ever exploring science. So, here is the glossary of botanical terms and definitions with all the terms that normally 'crop' up during a detailed study of botany.
Abscisic Acid (ABA): A growth inhibiting hormone enabling perennial plants to tolerate stressful conditions by promoting dormancy, stomatal closure and inhibiting growth.
Abscission Zone: The zone at the base of the flower (pedicel), fruit (peduncle) or leaf (petioles), at which plant cells fray off, thereby facilitating the easy fall of these plant parts.
Absorption Spectrum: Graph indicating the relative abilities of pigments to absorb various wavelengths of light.
Acetyl CoA: Developed as an intermediate of carbohydrate/ fat/ protein oxidation in the citric acid cycle, Acetyle CoA is the aceylated form of coenzyme A.
Achene: A simple, single-seeded, dry, indehiscent fruit comprising one seed attached to only the base of the pericarp.
Active Transport: The forceful movement of molecules from one side of the plasma membrane to the other side against a diffusion gradient, by expenditure of energy.
Adaptive Radiation: Diversification of group of organisms into several new species in order to fit into new environment.
Adenosine Diphoshate (ADP): A nucleotide comprising adenine, two phosphate units and ribose, it is a cofactor contributing either phosphate group or energy or both to a reaction.
Adenosine Triphoshate (ATP): A nucleotide comprising adenine, ribose and three phosphate units, is the major energy currency of the cell. It is a cofactor contributing phosphate group or energy or both to the reaction.
Adhesive Force: It is the force of attraction between dissimilar molecules due to which they stay together. For e.g. water droplets on a leaf.
Adventitious Roots: The roots that do not originate from primary roots are called adventitious. They generally arise from stems or leaves.
Aerobic Cellular Respiration: Part of cellular respiration, and plays a significant role in producing energy required to carry out different functions of the plant. It requires oxygen for the process.
Aerobic Respiration: Type of respiration requiring free oxygen as the terminal electron acceptor.
Agamospermy: Asexual reproduction methods involving cells of only the ovule to yield seeds and fruit.
Agar:A culture medium used specifically for bacteria. It is produced by some algae (red or brown) and has a gelatinous consistency.
Aggregate Fruit:The conjunction of several small, individual fruits, formed by different ovaries, located within the same flower to form a single fruit like that of raspberry.
Albuminous Seed: Seed containing large amounts of endosperm.
Allele: Gene versions varying from each other in their nucleotide sequence and may or may not result in different phenotypic traits.
Allopatric Speciation: Speciation emerging as the result of physical separation of two or more populations of one species, such that interbreeding is not possible.
Alternation of Generations: Plant life cycle type in sexually reproducing organisms involving alternation of diploid sporophyte phase and haploid gametophyte phase.
Amino Acid: Small molecule comprising nitrogen containing units used to synthesize proteins.
Anabolism: Process of metabolism by which various small molecules are combined to form large ones.
Anaerobic Respiration: Also called fermentation, this type of respiration does not need oxygen as the terminal electron acceptor.
Aneuploid: Anomaly in the usual chromosome number, wherein one or more chromosomes are missing or present as extras.
Angiosperm: Plants with seeds enclosed in ovaries that mature into a fruit.
Annual Ring: The formation of wood in plants on an annual basis comprises two concentric layers of wood: springwood and summerwood.
Anther: Part of the stamen containing sporogenous tissue which produces pollen.
Anthocyanin: Water soluble pigment located in the cell sap, which varies from red to blue in color. Found in flowers of most plants.
Apical Dominance: Hormones produced at the tip of the shoot cause suppression of lateral bud development in growing plant shoots.
Apical Deristem: Meristem located at the tip of the root, shoot or other organs of the plant.
Archegonium: Female reproductive organ in non-vascular plants like ferns and mosses.
Autotropic: Organisms converting inorganic matter into organic material for the purpose of sustenance.
Auxin: Growth regulating substance involved in apical dominance, cell elongation, rooting, etc.
Axil: Angle formed at the point of attachment between the petiole of a leaf and the upper part of the plant.
Axillary Bud: Bud situated just above the point of attachment of the leaf, i.e. leaf axil. Can be a floral bud or leaf bud. 

Bacillus: Rod shaped, spore-producing bacteria belonging to the genus Bacillus.
Backcross: Cross between a hybrid and one of its parents.
Bacteria: Single celled, omnipresent organisms appearing in spiral, spherical or rod shape.
Bacteriophage: It is an obligate intracellular parasite that breed inside bacteria by using the host's cellular machinery.
Bark: Tissues of the vascular cambium forming tough layer on the outer region of the woody stems and roots.
Base: Substances that reduce the concentration of hydrogen ions.
Basidiocarp: Fruiting body in basidiomycete fungi, such as puffball or mushroom.
Basidiospores: Spores formed on the basidium.
Basidium: The cells in basidiomycete fungi in which fusion of nuclei and meiosis occur to produce basidiospores.
Berry: Simple, thin-skinned fruit comprising a compound ovary with more than one seed, as in the case of gooseberry, grape, tomato, etc.
Biennial: Plants requiring two seasons to complete their life cycle. The first season growth is purely vegetative and the second one bears fruit.
Binary Fission: Process of cell division in prokaryotes, such as yeasts where the cell devides into two daughter cells.
Binomial Classification: System of classification that provides scientific names to organisms. Each name consists of a genus name and a species name.
Biological Controls: Use of natural inhibitors or enemies to combat pests and other damage causing organisms.
Biomass: Total mass of living matter present in a given habitat, expressed as volume of organisms per unit of habitat's volume or weight per unit area.
Biotechnology: Use of living organisms, tissue or cells for the manufacture of drugs or products intended for human benefit.
Blade: The broad, flattened, conspicuous part of the lead called lamina that is distinguished from the petiole or stalk.
Bract: Leaf like structure situated at the base of the flower or inflorescence.
Bryophyte: Phylum comprising non-vascular plants: lacking xylem and phloem. Mosses, liverworts, etc are bryophytes.
Budding: Type of asexual reproduction involving formation of new cells from protrusions arising from mature cells. Yeast reproduces via budding.
Bundle Sheath: Layer of parenchyma or sclerenchyma cells encircling the vascular bundle in plant leaves and stems.

Callose: A plant polysaccharide composed of glucose residues linked together through β-1, 3-linkages secreted by an enzyme complex (callose synthase), resulting in the hardening or thickening of plant cell walls.
Callus: Tissue formed over damaged areas of the plant in the form of a seal, thereby protecting it from further deterioration, and allowing the wound to heal.
Calvin cycle: Biochemical reactions cycle occurring during photosynthesis in the chloroplasts, wherein carbon dioxide is fixed and 6 carbon sugar is formed.
Calyptra: Small sheath of cells found in non-vascular plants, derived from the archegonium to cover the tip of the capsule partially or completely.
Calyx: Collective terminology for the sepals of a flower.
Cambium: Layer of meristematic tissue (also known as lateral meristems), responsible for secondary growth.
Capillary Water: Water held in the tiny pores between soil particles by the adhesive force: surface tension.
Capsule: Dry, dehiscent fruit consisting of two or more carpels that splits in several ways at maturity to release seeds.
Carpel: Single member of a compound pistil or single pistil unit, bearing the ovule in angiosperms.
Caryopsis: Small, dry, single seeded fruits which do not split at maturity. The pericarp cleaves to the seed coat; typically seen in grains.
Casparian Strip: Band of cell wall material in the radial and transverse walls of the endodermis. It stops the passive flow of materials into the stele.
Cation Exchange: Replacement of an essential element cation released from a soil particle by a proton.
Cavitation: The rupture of the water column in the xylem, when tension surmounts the cohesive nature of water.
Cell: Microscopic structure forming the basic structural and functional unit of living organisms. It encompasses nuclear and cytoplasmic material enclosed by a cell membrane.
Cell Biology: Branch of biology involving the study of cells, their structure, formation, components and functions.
Cell Cycle: Sequence of events occurring during cell division.
Cell Division: Process of division of cell with the purpose of growth or reproduction.
Cell Membrane: The semipermeable membrane sheathing cytoplasmic material of the cell.
Cell Plate: During cell division, the plate formed at the midpoint between two sets of chromosomes, which is involved in the wall formation between two daughter cells.
Cell Sap: Fluid present in the central vacuole of plant cells.
Cell Wall: The rigid boundary forming the outer structure of plant cells.
Cellulose: A complex carbohydrate composed of glucose units, which forms the major constituent of cell wall in plant cells.
Central Cell Nuclei: Mostly two in number nuclei uniting with sperm to form primary endosperm nucleus in embryo sac. It is a membrane enclosed organelle of eukaryotic cells that contains its genetic material in the form of chromosomes.
Centrioles: Small, cylindrical cell organelles found in animals and some algae and fungi. Located near the nucleus in the cytoplasm of most eukaryotic cells each centriole is usually composed of nine triplets of microtubules.
Centromere: Portion of the chromosome holding the two chromatids together before anaphase stage of mitosis or anaphase II stage of meiosis. The spindle fibers are attached to this region and move the chromosomes during cell division.
Chemiosmotic Phosphorylation: Occurring in mitochondria and chloroplasts, this prcoess involves the synthesis of ATP from ADP and phosphate unit.
Chemosynthetic Origin of Life: Theory according to which life began via a series of chemical reactions on primitive Earth.
Chiasma: X-shaped structure formed by the attachment of two chromatids of homologous chromosomes to each other during meiosis.
Chitin: Polymer composed of partly amino sugars, it is a semitransparent hard substance forming the outer covering or exoskeleton of crustaceans, arachnids and insects.
Chlorenchyma: Parenchyma tissues with chlorophyll content.
Chlorophyll: Green pigment found in plants, cyanobacteria and algae, which is involved in capturing light energy required for photosynthesis.
Chloroplast: Plastids opulent in chlorophyll content that carry out photosynthesis.
Chlorosis: Process of yellowing of leaves, occurring due to lack of chlorophyll.
Chromatid: One of the two identical chromosome strands united by a centromere into which the chromosome longitudinally splits while preparing for cell division.
Chromatin: Found in chromosomes, chromatin is a readily staining substance of a cell nucleus containing DNA, RNA and other proteins that form chromosomes during cell division.
Chromoplast: Plastids containing pigments other than chlorophyll, usually imparting red or yellow color.
Chromosome: Threadlike bodies made up of DNA coiled tightly several times around proteins called histones. Its structure consists of chromatids joined together at the centromere.
Chromosome Condensation: Also called pachytene, this process is a part of prophase I, wherein the chromosomes become shorter and thicker.
Cilium: Precisely arranged, short microtubules found mostly in bunches, similar to a flagellum. These may either be sensory or locomotory organelles.
Circadian Rhythm: A rhythmic daily activity cycle exhibited by many organisms in an intervals of 24 hours.
Citric Acid Cycle: In aerobic respiration, the complex series of reactions following glycolysis, which involve mitochondria, ATP and enzymes.
Cladophyll: Also called phylloclade, this is a flattened stem that looks like a leaf.
Class: In classification, the category coming between a division and order.
Cloning Vector: Molecule of DNA that replicates and transfers DNA from one cell to another.
Closed Carpel: Is another phrase used for Angiosperms that are plants with seeds inside the ovary.
Coccus: Sphere shaped bacteria.
Codon: Triplet of adjacent nucleotides in messenger RNA, which specify the amino acid to be incorporated into a protein.
Coenocytic: Large cells containing myriad nuclei. It is formed when the cell nucleus divides multiple times without the actual division of the cell.
Coenzymes: Molecules providing transfer site for biochemical reactions catalyzed by enzymes.
Cohesion-Tension Theory: This theory explains that the upward pull of water takes place by the combination of water molecules cohesion in the vessels and tracheids and tension on the water column caused by transpiration.
Coleoptile: The first leaf above ground level forming a sheath around the tip of the stem, so as to protect the emerging shoot (plumule) of monocotyledons like grasses and oats.
Coleorhiza: Sheath formed around the emerging radicle in plants of the monocotyledons like the grass family.
Collenchyma:Cells containing primary walls thickened at the cells corners, but thin elsewhere.
Companion Cells: Specialized parenchymal cells situated beside sieve tubes in the phloem of angiosperms that regulate flow of nutrients through the sieve tube.
Compost: Combination of several dead and decaying organic substances, such as manure, dead leaves, etc. used for soil fertilization.
Compound Leaf: Leaf blade divided into distinct leaflets attached via a common petiole.
Conidium: Fungal spore formed outside a sporangium and produced asexually.
Conifer: Woody trees or shrubs that are gymnosperms and bear cones.
Conjugation: Process of genetic exchange occurring in bacteria and some green algae, wherein the DNA is passed through a tube connecting adjacent cells.
Cork: Outer tissue layer of an old woody stem produced by cork cambium, whose cells are saturated with suberin at maturity.
Cork Cambium: Lateral meristematic tissue ring found in woody seed plants between the exterior of woody stems or roots and central vascular tissue. It produces cork to its exterior and phellogen to its interior.
Corm: A thick food storing, vertically oriented stem enveloped by some papery nonfunctional leaves.
Corolla: Collective phrase used for the petals of a flower.
Cortex: Generally parenchyma cells forming a tissue extending between the vascular tissue and epidermis.
Cotyledon: A seed leaf or embryo leaf that usually absorbs or stores food.
Crossing-over: The exchange during prophase I in meiosis, between corresponding segments of chromatids of the homologous chromosomes.
Crown Division: Asexual type of reproduction, involving the division of the base of the stem.
Cuticle: Thin hyaline film derived from the exterior surfaces of epidermal cells, covering the surface of plants.
Cutin: Fatty or waxy substance making up the cuticle.
Cutting: Vegetative plant parts used for asexual propagation.
Cyclosis: Flow of cytoplasm with the cell.
Cytochrome: Protein containing iron, acting as small electron carriers by transferring molecules in electron transport system.
Cytogenetics: Study of genetic effects of chromosome behavior and structure.
Cytokinesis: Cell division followed by mitosis.
Cytokinin: Growth hormone concerned with cell division and other metabolic activities of the cell.
Cytoskeleton: Network of microfilaments and microtubules that protects and maintains cell shape, enables cellular motion and plays important roles in both intracellular transport and cell division. It is present in both prokaryotes and eukaryotes.
Cytosol: Fluid part of the cell into which the organelles are scattered.

Dark Reactions: Stage of photosynthesis which is light independent wherein carbohydrates are synthesized from carbon dioxide.
Day-neutral Plant: Plants independent of specific day lengths for commencement of flowering.
Deciduous: The plants that shed their leaves before a dry season to minimize the transpirational loss of water.
Decomposer: Organism breaking down organic matter into forms suitable for recycling.
Dedifferentiate: Pertaining to cells, dedifferentiate means becoming less specialized.
Deoxyribonucleic acid (DNA): Nucleic acid containing genetic instructions used for the proper functioning and development of all living organisms.
Development: Changes pertaining to the growth and differentiation of plant cells into various tissues and organs.
Diatom: Unicellular, microscopic, freshwater or marine algae belonging to phylum Chrysophyta, which contain two silica shells fitting together like parts of a petri dish.
Dichotomous Branching: Fork resulting into two somewhat equal branches, as in the case of leaf veins or secretory ducts.
Dicotyledon: Angiosperm class whose seeds feature two cotyledons.
Dictyosome: Organelle comprising disc-shaped, mostly branching hollow tubes, which accumulate and pack substances required for the synthesis of various materials in the cell.
Differentially Permeable Membrane: Membrane permitting the diffusion of various substances at different rates.
Differentiation: Conversion of relatively unspecialized cell to a better specialized cell.
Diffusion: Haphazard movement of molecules from regions of high concentration to regions of lower concentration, leading to uniform distribution and leveling of the different concentration areas.
Digestion: Conversion of insoluble, complex substances into soluble, simpler substances under the control of enzymes.
Dihybrid Cross: Cross involving heterozygous parents with two different gene pairs.
Dikaryotic: Presence of two nuclei in a cell.
Dioecious: Plants featuring unisexual cones or flowers, with the male cones and flowers belonging to certain plants and the female cones and flowers confining to certain other plants of the same species.
Diploid: Cells comprising two sets of chromosomes in the nucleus. This is denoted by the term '2n', and is a characteristic of the sporophyte generation.
Diuretic: Substances that increase the urine flow.
Divergent Speciation: Emergence of a new species from a part of existent species, with the remnant species continuing as the original species itself, or else transforming into a new species.
Dominance: Phenomenon in which one allele of a gene masks the phenotypic expression of another allele of a gene. The allele masking the other allele is called dominant allele.
Dormancy: The phase of temporary growth cessation in plants, under harsh environmental situations, wherein the regular conditions required for growth cannot be met.
Double Fusion: Phenomenon in which one sperm fertilizes an egg to form a zygote, while another sperm fertilizes the central cell nuclei (polar nuclei) forming a primary endosperm nucleus.
Drupe: Fleshy fruits with one or more seeds enclosed within a hard protective layer called endocarp.

Early Wood: Wood formed during the early part of the growing season, characterized by large, thin walled cells. It features large number of vessels in angiosperms and in gymnosperms, it features wide tracheids.
Ecology: Branch of biology involving study of interactions of organism with the environment and with each other.
Ecosystem: System involving the interactions of living organisms with each other as well as with the non-living environment.
Ectomycorrhiza: One type of mycorrhizal association, wherein the fungi do not invade the cell membrane, instead invade the root cortex cells.
Egg: Non motile female gamete.
Elater: Small, twisted, strap-like, elastic filament, usually occurring in pairs that push the spores out of the sporangium, thereby assisting in spore dispersal.
Embryo: The immature sporophyte formed after fertilization from the zygote in the archegonium or ovule.
Enation: Tiny green leaf like structures growing on the stems of whisk ferns and do not have vascular tissue.
Endocarp: The innermost layer of the fruit wall enclosing the seed in fleshy fruits.
Endocytosis: Absorption of solid or liquid material into a cell by means of invagination of the plasma membrane to surround the material and pinching shut to form a vacuole or vesicle around it.
Endodermis: Single layer of specialized parenchyma cells surrounding the vascular tissues in the roots and stems. It forms the inner boundary of the cortex.
Endoplasmic Reticulum: Complex system of narrow tubes and sheets forming a network in the cell's cytoplasm. It divides the cytoplasm into various compartments. The endoplasmic reticulum may or may not have ribosomes attached to them.
Endosperm: Nutritive material derived from the embryo sac in seed plant ovules. It furnishes the developing embryo and seedling with nutrition.
Endosymbiont Hypothesis: According to this hypothesis, mitochondria and plastids were free-living bacteria, which got incorporated into the cells.
Enzyme: A type of complex protein that enhances the rate of a chemical reaction in living cells, without itself being used in the reaction.
Epicotyl: Portion of the seedling above the cotyledon's attachment point.
Epidermis: Single layer of cells, forming the outer tissue of leaves, roots and young stems.
Epigynous: Term used to describe a condition in which the flower parts are attached above the ovary.
Epiphyte: Plants growing above the ground, that attach themselves to other plants without being a parasite. They derive their nutrients and water from air, dust, rain, etc.
Essential Element: Elements which are essential for normal development, growth and reproduction of plants. Nitrogen, calcium, magnesium, phosphorus, etc. are examples of some essential elements.
Etiolation: Term referring to a condition involving poor leaf development, long internodes, pale and weak appearance of the plant due to deprivation of sunlight.
Eukaryotic: Cells comprising nucleus, chromosomes and distinct membrane bound organelles.
Eutrophication: Process of nutrient accumulation in the water bodies resulting in its gradual nutrient enrichment. This entails to increase in the growth of algae and various other organisms.
Exine: Outer coat of a spore or pollen grain.
Exocarp: Outermost layer of the fruit wall.
Explant: Severed portions of the plant; example: leaf or stem tissue that are utilized for tissue culture.
Extranuclear DNA: DNA located outside the nucleus, as seen in mitochondria and plastids.
Eyespot: Tiny reddish sensory organ, which is sensitive to light. It is found within motile unicellular organisms.

Facultative Aerobe (Facultative Anaerobe): Organisms that use oxygen when available, however, can even live without it.
Family: Category of classification above the genus category and below the order category.
Fermentation: Type of respiration involving the process of glycolysis, wherein lactic acid or ethyl alcohol are formed as an end product.
Fertilization: Fusion of two gametes to form a zygote.
Fiber: Cells which are long and thick walled, often containing protoplasm which is dead at maturity.
Fibrous Root System: Cluster of similarly sized roots. It is found in some dicots and most monocots.
Filamentous Body: Usually green algae cells exhibit this kind of body, wherein the cells are held firmly by a middle lamella when they divide transversely.
First Filial Generation: Progeny of an experimental cross between two parent species.
Fission: Cell division of bacterial and other related organisms that results into two new cells.
Flagellum: Multicellular organisms produce threadlike structures, which protrude from the motile cells and assist mainly in locomotion.
Floret: Tiny flowers belonging to the inflorescence of members of the grass family or sunflower family.
Fluid Mosaic Model: A plasma membrane model according to which, the proteins are embedded in the lipids throughout the membrane which gives a mosaic appearance to it. The proteins change their position, hence, it is called a 'fluid' membrane.
Follicle: It is a dry, monocarpellary, unilocular, multi-seeded fruit.
Food Chain: Natural chain of organisms, in which each organism of the chain feeds on members below it in the chain, and is consumed by organisms above it in the chain.
Foot: Attached to the gametophyte, the foot is the basal portion of the embryo of bryophytes and absorbs food from the gametophyte.
Founder: Individuals who are the first to establish a population in a new environment or habitat.
Freely Permeable Membrane: Membranes permitting all kinds of substances to pass through it.
Frond: Usually used for a fern leaf, however, occasionally it is also used to denote palm leaves.
Fruit: In angiosperms, the ripened ovary wall produced from the flower, usually containing seeds.

Gametangium: Cell in which gametes are produced.
Gamete: Haploid sex cells; ovum and sperm which unite to form a zygote.
Gametophore: Leafy stalk on which the gametangium(sex organs) is borne.
Gametophyte: Haploid plant that produces gametes.
Gemma: Cluster of cells that get detached from parent body and possess the ability to develop into a completely new organism or plant. Seen in liverworts and mosses.
Gene: Basic unit of heredity, involving sequence of nucleotide containing necessary information for the structure and metabolism of an organism.
Gene Bank: It is a way of preserving plants and seeds for their germ plasm.
Gene Pool: Total number of all alleles in all the sex cells present in the individuals of a population.
Gene Synthesizer: Machine producing specific DNA sequences.
Genetic Drift: Alteration in the genetic makeup of a particular population, which mostly takes place by chance alone.
Genetic Engineering: Introduction of genes from one DNA form into another, by artificial means is called genetic engineering.
Genetics: Branch of biology involving the study of heredity, which deals with the differences and resemblances of organisms entailing from the interaction of their genes and the habitat.
Genus: Classification category located between a family and species.
Germ-line Mutation: Mutation occurring in the cells from which gametes are derived.
Germ Plasm: Aggregate of all genes of a species or organism groups.
Germination: Commencement or resumption of growth of a spore or seed.
Gibberellin: Group of plant hormones possessing different effects on growth, which are mostly related to enhancement of stem elongation.
Gills: Flattened plates of compact mycelium radiating to the outer region of the stalk on the bottom portion of the mushroom cap.
Girdling: Phenomenon involving the discarding of a band of tissues which extend to the inner side of the vascular cambium on the woody plant stem.
Glycocalyx: Mucilaginous secretion surrounding many prokaryotic cell walls.
Glycolysis: Cycle in which glucose is broken down to form pyruvic acid.
Glycoprotein: Proteins featuring attachment of sugars, which are less than ten sugars long.
Golgi Body: Organelle comprising layers of flattened sacs, which absorbs and processes synthetic and secretory products from the endoplasmic reticulum and then secretes them to the cell's exterior or releases them into different parts of the cell.
Graft: Unification of the scion (shoot) of one plant and stock (root) of another plant.
Granum: The chloroplasts in vascular plants exhibit the presence of a series of stacked thylakoids, called granum.
Gravitational Water: After rain, the water draining into the pores of the soil is called gravitational water.
Ground Meristem: The mersitem producing all the primary tissues of the plant except the epidermis and the stele.
Guard Cell: Pair of specialized cells surrounding the stomata. These help in transpiration.
Guttation: Exudation of water from the leaves in the form of droplets due to root pressure.
Gymnosperm: Type of plants in which the seeds are not enclosed in the ovary during the development.

Habitat: The natural environment in which the plant completes its life cycle.
Haploid: Possessing one set of chromosomes in each cell. Denoted by 'n'.
Hardwood: The wood of both dicot trees and shrubs are termed as hardwood. A dicot wood generally contains fibers.
Haustorium: Organ bearing semblance to a root, which is used by a parasite to penetrate into the host plant to absorb nutrients.
Heartwood: Darker colored non-living wood, whose cells have stopped conducting water.
Herbarium: Collection of plant specimens, which are pressed, dried, mounted on paper, identified and then labeled.
Heterocyst: Thick walled, transparent, slightly enlarged cell located in the filaments of certain cyanobacteria.
Heterokaryosis: Condition pertaining to certain cells in fungi, which feature two or more nuclei of different mating types.
Heterospory: Formation of both megaspores and microspores.
Heterotrophic: Organisms that depend on other organisms for nutrition, as they are incapable of synthesizing their own food.
Heterozygous: Possessing two different alleles of a trait on homologous chromosomes, which are situated at the same locus.
Histones: Basic nuclear proteins forming complexes with DNA to form nucleosomes and then complexing further to form chromosomes.
Hold Fast: Filament like organ of attachment present in algae that holds the algae to the substrate.
Homokaryosis: Condition in fungi, wherein all nuclei in the mycelium are genetically identical.
Homologous Chromosomes: Diploid nucleus comprising a pair of chromosomes, one inherited maternally and the other paternally.
Homozygous: Possessing two identical alleles on a homologous chromosome pair at the same locus.
Hormone: Organic substances produced mostly in small amounts in one part of the organism and then transported to different parts of the organism, where it controls the growth and development of the organism.
Hybrid: Heterozygous progeny of two parents differing in one or more inheritable attributes.
Hybrid Sterility: Post-zygotic isolation process, wherein a hybrid zygote develops into an adult, however, is incapable of forming fertile gametes.
Hydathode: Specialized leaf structure located at the leaf's tip, from which the water is forced out when root pressure increases.
Hygroscopic Water: Water chemically adhering to soil particles due to which they are unavailable to plants.
Hymenium: Layer of fertile cells producing spores in a fungus fruiting body.
Hypha: Threadlike like tubular filaments found in fungi.
Hypocotyl: Portion between the cotyledon and the radicle in a seedling or embryo.
Hypodermis: Cell layer following the epidermal layer and distinct from the cortical parenchyma cells in some plants.
Hypogynous: Condition featuring attachment of flower parts below the ovary.

Immobile Essential Element: Element that cannot be removed from mature tissues. This means if young tissues become deficient in these elements they develop a deficiency, even though this element is present in the older tissues.
Imperfect Flower: Flowers lacking either carpels or stamens or both.
Imperfect Fungi: Those fungi that do not sexually reproduce or their sexual reproduction behavior has never been monitored.
Impermeable Membrane: Membranes that do not permit the passage of any substances across them.
In vitro: Carrying out growth of cells in artificially maintained media, such as test tubes, flasks, etc. instead of inside a living organism.
Inbreeding: Process of individuals with common ancestry mating together.
Inbreeding Depression: Condition in which individuals with common ancestry exhibit low fertility and poor performance.
Incipient Plasmolysis: The point at which the protoplasm just begins to stop exerting pressure on the cell wall, when the plant cell membrane shrinks after losing water.
Indusium: Umbrella shaped membranous tissue covering, located on the fern sorus.
Inferior Ovary: Ovary appearing to have its floral parts like calyx, corolla and stamens attached to the top of it. The appearance is due to the unison of the floral parts.
Inflorescence: Discrete group of flowers attached to a common axis in a specific order.
Integument: Outermost wall of the ovule, which develops into the seed coat. In angiosperms, the ovule has two integuments, while in gymnosperms, a single integument is seen.
Intercellular Space: Space present between two adjacent cells.
Intermediate-day Plant: Plants characterized by two critical photo periods. This means the plant will not flower during too short or too long days.
Internode: Region between two nodes.
Interphase: Phase of cell cycle which is not cell division but encompasses phases such as G1, S, G2. Here, the cell prepares for cell division.
Intrinsic Protein: Protein deeply integrated into the membrane, which cannot be discarded from the membrane easily.
Isogamy: Sexual reproduction taking place between gametes that are similar in size. Seen in certain fungi and algae.

Jungle: A dense growth of various plants where many organism can thrive. Forest is another term used for a jungle.
Junipers: This term refers to members of the Family Cupressaceae, and are characterized needle-like leaves in juviniles and scale-like leaves and cones in the adults.
Jointed Stems: Stems made up of one jointed, three dimensional and ribbed parts, more like a clump from where branches shoot.

Kinetochore: During late prophase, some specialized protein complexes are developed on the vertical faces of a centromere, and are called kinetochore.
Kingdom: Highest level of classification category.
Knot: Projection of plant tissue in the stem, root, etc. especially when swollen.
Karyogamy: Fusion of two gametes of the nuclei after plasmogamy (protoplasmic fusion).
Karyokinesis: Process of division involving series of active changes in the nucleus of a cell.
Key: Tools used to identify unfamiliar plants. Comprise mainly of pairs of choices.

Lamina: Expanded, flat, broadened portion of the leaf. Lamina is also referred to as leaf blade and does not include the petiole.
Late Wood: Also referred to as summer wood, this is the wood formed late in season, in the secondary xylem. It usually comprises narrow tracheids in gymnosperms and few or no vessels in angiosperms.
Lateral Roots: The scores of tiny roots stemming from the tap root.
Laticifer: Specialized ducts or cells that bear resemblance to vessels. These form a network of cells in the phloem and other plant parts that secrete latex.
Leaf: Expanded, flattened and usually green structures of the plant, arranged in various ways on the stem. If green, they act as sites for photosynthesis.
Leaf Gap: Area above leaf trace, wherein conducting tissues are absent; as seen in fern vascular tissue.
Leaf Scar: Portion of the stem, wherein the leaf was attached, before its abscission.
Leaf Trace: Vascular bundles extending from the stem into the cortex and then protruding their way into the leaf.
Leaflet: Subdivisions of the leaf lamina; as seen in compound leaves.
Legume: Dried fruits comprising seeds adhering to their edges which split along two seams.
Lenticel: Spongy cluster of cells located in the bark of woody plants, which allow gas exchange between the external atmosphere and interior of a plant.
Leucoplast: Colorless plastids that store starch.
Lichen: Fungi living in symbiotic union with algae. They appear either leaf-like, crust-like or in the form of branching trees, rocks, etc.
Light-dependent Reactions: Chain of chemical reactions involving the conversion of light energy into chemical energy with the assistance of chlorophyll pigment.
Light-independent Reactions: Cyclic sequence of chemical reactions utilizing carbon dioxide and energy released during the light-dependent reactions. These reactions are independent of light, and take place in the stroma of chloroplasts.
Lignin: Type of polymer impregnating some cell walls, like those of wood.
Ligule: Small tongue like structures located at the base of the spike moss.
Linked Genes: Genes situated close together on the same chromosome that crosses over only rarely.
Lipid: Hydrophobic and water insoluble compounds, such as waxes, fats, oils, etc.
Locule: Hollow situated within a sporangium or ovary.
Locus: Position of gene on a chromosome, which is determined by the linear order relative to the various other genes situated on the same chromosome.
Long-distance Transport: Transportation of substances from one cell to another cell, which is situated at a far away location.
Long Shoot: These shoots feature tiny papery leaves; as observed in conifers.
Lumen: Inner portion of cell structures such as vacuole, vesicle, resin duct or oil chamber.

Mass Selection: Plant breeding procedure involving formation of an amalgamated population via selective harvesting of individuals from a population which is heterozygous.
Maternal Inheritance: Condition in which offspring receives extranuclear material from the female gamete.
Mating Types: Biochemical attributes that differentiate one mating type from the other. Gametes associated with the same mating type cannot fuse, and require compatible mating types for syngamy.
Megagametophyte: Female gametophyte produced by the megaspores of heterozygous plants.
Megaphyll: Present in all seed plants and ferns. It is a leaf that has evolved from a branch system and is characterized by branching veins.
Megasporangium: Sporangium in which only megaspores are produced.
Megaspore: Spore that advance into female gametophyte.
Megasporocyte: Diploid cells undergoing meiosis to form megaspores.
Meiosis: Process of cell division, wherein chromosomes replication is followed by two successive nuclear divisions. The resulting spores inherit a haploid set of chromosomes.
Meristem: Region of undifferentiated, actively dividing, growing cells from which new cells emerge.
Mesocarp: Central portion of the fruit wall, which is sandwiched between the outer exocarp and inner endocarp.
Mesophyll: Tissues (parenchyma or chlorenchyma) situated between the epidermal layers of the leaf.
Messenger RNA: Single stranded RNA molecule carrying genetic information from the DNA template to the site of protein synthesis.
Metaphase: Phase two of mitosis, wherein the chromosomes drift towards the center of the spindle.
Microphyll: Type of leaf characterized by single unbranched vein, and present in lycophytas.
Micropropagation: Plant propagation from single cells under artificial conditions as created in the laboratory.
Micropyle: Opening located in the ovule's integuments, through which the pollen tube gains access to embryo sac or archegonium.
Microsporangium: Sporangium in which only microspores are formed.
Microspore: Spore developing into male gametophyte.
Microsporocyte: Diploid cells which on completion of meiosis produce microspores.
Microsporophyll: Small leaf like structure producing microspores.
Microtubule: Single proteinaceous tube like structure situated mostly in the plasma membrane. It regulates cellulose addition to the wall of the plant cells.
Middle Lamella: Layer of adhesive substance rich in pectin, which cements the cell walls of adjacent cells of multicellular plants together.
Midrib: Main middle vein of a leaf (pinnately veined) or leaflet.
Minor Veins: Small veins present on the leaf that branch off the lateral veins.
Mitochondrial DNA: Double stranded genetic material found in the mitochondria of cells.
Mitochondrion: Rod shaped organelles present in several eukaryotic cells, that work as powerhouse of the cell, by breaking down oxygen and nutrients and releasing energy in the form of ATP.
Mitosis: Nuclear division in which nuclear chromosomal material is initially duplicated and then split into two equal portions. Each daughter nuclei receives one portion of the nuclear chromosomes, thereby producing two genetically identical daughter nuclei.
Molecular Pump: Protein embedded in the membrane that forces molecules to pass from one side to another with the help of energy.
Monocotyledon: Angiospermic plants whose seeds possess one cotyledon.
Monoecious: Plants which possess both unisexual male and female flowers or cones on the same plant.

Naked DNA: Gene transfer processes such as transformation and transfection involves the passage of nucleosome and histone free DNA. This histone and nucleosome free DNA is called naked DNA.
Nastic Movement: Non-directional movement of flat plant organs such as leaf, petal, etc. irrespective of the stimulus position.
Natural Selection: The process of evolution involving the population rise of organisms which have inherited the traits that enable them to successfully survive in natural conditions and reproduce successfully in comparison to others.
Necrosis: Death of plant cells or tissues, leading to discoloration of leaves and stems. It can even conduce death of the plant.
Necrotroph: Fungus which attacks the host in a virulent manner, and then kills it. They then absorb all the nutrients from the dead organism.
Nitrogen Assimilation: Process of ammonium incorporation into organic compounds present within an organism.
Nitrogen Fixation: Process by which plants convert atmospheric nitrogen into compounds such as nitrate or ammonium, which they can readily use.
Node: Point of attachment of the leaves.
Nucellus: Central region of an ovule, wherein embryo sac development takes place.
Nuclear Envelope: The porous double lipid bilayer sheathing the nucleus.
Nucleic Acid: Macromolecule composed of chains of nucleotides, carrying genetic information.
Nucleolus: Spherical structure which is non-membranous and comprises proteins and nucleic acids. It is present within the nucleus, and each nucleus may contain more than one nucleolus.
Nucleotide: Chain of molecules which make up the structural units of DNA and RNA. Nucleotides comprise a sugar, nitrogenous base and phosphate group.
Nucleus: Largest cell organelle found in most eukaryotic cells. It contains most of the cell's genetic material, thus is involved with inheritance, ribosome synthesis and metabolism control.
Nut: A dry fruit consisting of only one seed and a thick pericarp. Nuts feature a cluster of bracts at their base.

Obligate Aerobe: An organism that requires air for aerobic cellular respiration. They use oxygen in order to oxidize substrates and obtain energy.
Oogamy: It is a kind of sexual reproduction where the female gamete is non motile and larger than the motile male gamete.
Oogonium: It is the term given to the female sex organ of various algae and certain fungi.
Operculum: The covering that protects the peristome of the moss sporangium.
Organelle: The membrane bound cell bodies found in the cytoplasm. E.g. mitochondria.
Osmosis: The differential behavior of membrane for the purpose of diffusion of water and other solvents. Osmosis always takes place from the region of higher concentration to lower concentration.
Osmotic Potential: This is the minimum pressure required to prevent osmosis from taking place. It is the pressure developed by a solution that is separated from water by a selectively permeable membrane.
Outcrossing: The pollination which takes place between two different flowers which may or may not belong to the same genetic line.
Ovary: That part of the flower which is situated at the base of the pistil and contains an ovule (or ovules) and eventually develops into a fruit.
Overtopping: The ability of a shoot to grow for longer period of time than the other shoot in the same plant, which was a result of branching.
Oxidation Phosphorylation: The energy released during metabolic pathways, which is responsible for the formation of ATP and ADP.

P-protein: This is a fibril protein which is responsible for plugging sieve pores and precludes outflow if sieve elements are damaged.
P-protein Plug: It relates to the obstruction of a sieve region or sieve plate by bast protein.
Palindrome: This term refers to a DNA sequence which can be read forward or backward.
Palisade Mesophyll: It is also known as palisade or palisade parenchyma, and is the upper layer of ground tissue in a plant leaf. It comprises prolonged cells underneath and vertical to the upper cuticle, and constituting the principal area of the photosynthesis process.
Parenchyma: These are cells comprising only thin primary walls. All other features and functions vary from one kind to another.
Parthenocarpy: It is the activity wherein a fruit is produced without egg fertilization in the ovary.
Pedicel: A pedicel is one of the subordinate stems in a ramous inflorescence, bearing a single flower.
Peduncle: It is the stem which holds either a bunch of flowers or a solitary flower.
Perennial: This term refers to the plants which have a life cycle that lasts for over two years.
Pericarp: It relates to the matured and diversely altered walls of a plant ovary.
Pericycle: It is the outermost cell layer of the stele in a plant, which often turns into a zone that is multi-layered.
Periderm: This term pertains to the bark, and comprises cork, cork cambium, and any enclosed tissues like secondary phloem.
Perigynous: This simply means located around the pistil on the edge of a concave receptacle, as stamens or flower petals.
Peristome: The circles of tiny, pointed, odontoid outgrowths around the opening of a capsule or urn of mosses which appear when the lid is removed.
Petals: The colored segments of the corolla of the flower, which most often are involved in drawing in pollinating agents.
Petiole: The lithesome stem which attaches a leaf to the stem.
Phloem: It is a portion of vascular tissues that comprises sieve tubes, companion cells, parenchyma, and fibers. It forms the food-conducting tissue of a plant.
Photosynthesis: Photosynthesis is a plant activity which includes the synthesis of complex organic substances, peculiarly saccharides, from carbon dioxide, water, and inorganic salts, utilizing sunlight as a source of energy and with the help of chlorophyll and associated pigments.
Photosystem I and II: Photosystem I absorbs light for the transfer of negatron from plastocyanin to ferridoxin. Its reaction center is P700. Photosystem II absorbs light for oxidation of water and reduction of plastoquinone. Its reaction center is P680.
Phytochrome: This term pertains to a plant pigment which is involved in the soaking up of light in the photoperiodic response which modulates various types of growth and development.
Pinna: It is one of the basic divisions of a pinnated leaf.
Pistil: The female organ of a flower which bears ovules or seeds, consisting of a complete ovary, style, and stigma.
Pit: It is concerned with the portion of a sclerenchyma cell, where there is no secondary wall over the primary one, and substances are able to pass into or out of the cell.
Pith: This is a soft and squishy central cylinder of parenchymatous tissues in the stalks of plants having two cotyledons in the seed.
Plant Anatomy: Study of the internal structure of the plant.
Plant Geography: It is also known as phytogeography, phytochorology, geobotany, geographical botany, or vegetation science; and refers to spatial distribution of plants and vegetation in different environment and regions.
Plant Physiology: The study of plants, which involves processes such as nutrition, reproduction, and other functions.
Plant Taxonomy: The science that refers to the identifications, description, naming, and classification of plants according to their unique characteristics.
Plasmodesmata: It pertains to a narrow hole in the elementary wall, that comprises some cytol, cell membrane, and a desmotubule. It is a means of communication between cells.
Plasmodium: Body of slime mold, which is a large mass of living substance with hundreds or thousands of karyons. Plasmodium ingest fungal spores, bacteria and other tiny protozoans.
Plasmolysis: It is an activity which relates to the shrinking of the living substances when water is removed by exosmosis.
Plastid: These are major organelles found in plant cells, as well as algal cells. These organelles are sites of manufacture of various essential chemical compounds used by the cell. They often contain chlorophyll, which is used for photosynthesis.
Plumule: It is the bud of the plant axis which moves up while it is still in the embryo.
Pneumatophore: It refers to a differentiated structure that originates from the root in particular plants which spring up in swamplands and fenlands, and act as a respiratory organ. E.g. Mangroove.
Pollen Grains: They relate to microspores in seed plants, that comprise a male gametophyte.
Pollen Tube: The protoplasmic tube which is squeezed out from a spudding pollen grain and develops toward the ovule.
Pollination: This natural process includes the conveyance of pollen from the anther to the stigma.
Pollinium: A cohered mass or body of pollen grains, characteristic of plants which belong to the orchid and milkweed families.
Polymer: It is a big chemical compound that consist of several subunits called monomers.
Pome: It pertains to the characteristic fruit of the apple family such as apple, pear or quince, in which the edible flesh grows from the greatly tumefied receptacle and not from the carpels.
Prickles: These are sharp protuberances of the cortex and cuticle.
Primary Pit Field: It is the region of the primary cell wall which is particularly thin and consists of many plasmodesmata.
Primary Producer: Any green plant which has the ability to convert light energy or chemical energy into organic substance.
Primary Tissue: Any tissue which is directly derived from distinction of an apical meristem or leaf primordium.
Procambium: It is the meristem from which vascular tissues originate.
Prochlorophytes: A class of procaryotes that possess both chlorophyll A and B, and is considered to be nearly associated to the antecedents of plastids in algae and plants.
Producer: A photosynthetic green plant or chemosynthetic bacterium, that comprises the first trophic level in a food chain.
Proembryo: This term relates to the cells which are forced into the endosperm and afterwards become the embryo, in seed bearing plant's embryos.
Prokaryotes: Organisms which do not possess true nucleus or membrane-bounded cell organelles such as eubacteria, cyanobacteria, and archaebacteria.
Promoter Region: The area of a cistron in which control molecules and RNA polymerases bind during the process of cistron activation and transcription.
Prop Root: An adventitious root which holds the plant, as the aerial roots of the Rhizophora mangle tree or of the maize plant.
Prophase: The initial phrase of mitosis or meiosis in eukaryotic cellular division, during which the nuclear envelope breaks down and filaments of chromatin form into chromosomes.
Proplastid: A cytoplasmic cell organelle from which a plastid originates and develops.
Protein: The plant tissue that is rich in organic molecules which are believed as a food source providing necessary amino acids.
Protein Sequencing: This is a process that includes determining the amino acid sequences of its constituent peptides; and also finding out what compliance it follows and if it comprises any non-peptide molecules.
Prothallus: A tiny, flat, and gentle structure developed by a spudding spore, that has sex organs, and is the gametophyte of ferns and some other plants. Its structure resembles a leaf.
Protoderm: A thin outer layer of the meristem in embryos and growing points of roots and stems, which gives rise to the epidermis.
Protonema: A threadlike structure created by sprouting of the spores in small leafy-stemmed flowerless plants and other related plants, and from which the leafy plant, that has the sexual organs, develops as a sidelong or terminal branch.
Protoplast: The living substance of a plant, including the protoplasm and cytomembrane after the cell wall has been removed.
Protoplast Fusion: A method by which two energids are coalesced to create hybrid cells that can develop into mature hybrid organisms; normally performed on plants.
Protostele: The firm stele of most roots, that possesses a central core of xylem enclosed by bast.
Pure-bred Line: The homozygous dominant and homozygous recessive genetic constitution of a line which are selfed and utilized in spawning experiments.
Pyrenoid: A proteinaceous structure that is found within the chloroplast of specific algae and nonvascular plants, which is believed to be related to starch deposition.

Quantitative Trait: These traits are controlled by various genes and environmental factors. They are measured on a continuous scale.
Quiescence: Every plant requires some specific environmental conditions for its proper functioning and rapid growth. The growth or germination of the seeds or plants are hampered if these environmental conditions are not satisfied. This is termed as 'quiescence'.
Quiescent Center: Quiescent center is the portion of the root situated at the apex of the plant tissue i.e. meristem in which cell division does not occur.

Rachis: Rachis is the extension of the axis of petiole or leafstalk in the compound leaf. All leaflets are attached to the rachis.
Radicle: Extension of the axis of petiole or leafstalk in the compound leaf. All leaflets are attached to the rachis.
Ray: Series of parenchyma cells that are radially arranged along the vascular region of the xylem and the phloem. These parenchyma cells transport food, water and other materials laterally in the roots and stems of woody plants.
Reaction Wood: Is formed when a woody plant encounters mechanical stress, as caused by wind exposure, soil movement and excess snow fall.
Receptacle: Expanded portion of the peduncle, wherein various parts of the flower are attached.
Recessive Trait: It is the trait that reflects in the phenotype only when the dominant gene is absent. E.g. color blindness.
Recombinant DNA: DNA molecule created either by crossing over in meiosis or under laboratory environement (in vitro). It is formed when DNA from at least two organisms is taken.
Red Tide: Marine phenomenon in which a reddish tint is formed on the water due to the sudden growth of cells in certain protozoa or red algae.
Reduction Division: Same as meiosis.
Reproduction: It is the birth of a new organism born either by sexual or asexual means.
Resin Canal: Tubular duct present in coniferous trees and seeds, which is lined with resin secreting cells.
Respiration: Cellular breakdown of sugar and other food molecules, in which a part of energy is utilized. If oxygen is utilized during the breakdown, it is known as aerobic respiration or else it is termed as anaerobic respiration.
Restriction Enzyme: Also called restriction endonuclease, this enzyme is capable of recognizing specific sequences in DNA at a specific site (restriction site), and then severing it.
Reticulate Venation: Reticulate venation is a thin, flat, laminar like structure of a leaf, featuring a net-like pattern of the veins, structured for the purpose of photosynthesis.
Retrovirus: Common type of plant virus whose genetic material is single-stranded RNA.
Rhizoid: Delicate root like filament that functions as a root in mosses and ferns. It provides support or performs the absorption function in them.
Rhizome: Horizontally oriented, underground root-like stem that has nodes and internodes.
Ribonucleic Acid (RNA): Type of molecule containing large amount of nucleotide units, wherein each nucleotide contains three elements- nitrogenous base, a ribose sugar, and a phosphate. It is involved in protein synthesis.
Ribosome: Cell organelle composed of proteins and ribonucleic acid (RNA), which is responsible for protein synthesis.
Root: Organ of the plant situated below the ground and absorbs water and mineral salts. Buds, leaves or nodes are absent in root.
Root Cap: Thimble-shaped mass of cells that cover and protect the growing tip of the root.
Root Hair: Hairlike outgrowth arising through the epidermal cell of the root. Located just behind the tip of the root, this root hair helps absorb water and nutrients from the soil.
Root Nodule: Plants forming symbiotic associations with nitrogen-fixing bacteria, exhibit swelling in their roots, at the region where the bacteria comes in contact with the root.
Runner: Slender creeping stem that contains long internodes, growing horizontally along the surface of the ground. E.g. strawberry plant.

Saprobe: Saprobes are heterotrophs which contribute to the various nutrient cycles by feeding on decomposing organic matter.
Sapwood: Sapwood is the outer wood which carries water from roots to the leaves in order to facilitate water storage for future use.
Sclereid: Sclereid is a cell, characterized by the presence of a thick secondary wall and absence of a protoplast.
Sclerenchyma: Sclerenchyma is a supportive tissue, found in plants, which is typically composed of hard, thick and dry cells.
Secondary Phloem: Secondary phloem is the phloem which is derived from vascular cambium.
Secondary Tissues: Secondary tissues are the tissues of the secondary plant body which are produced by vascular cambium.
Secondary Xylem: Secondary xylem is the xylem that is derived from vascular cambium.
Seed Coat: Seed coat, also referred to as testa, is the protective outer covering of seeds of various flowering plants.
Selectively Impermeable Membrane: It is a barrier which regulates the movement of substances, allowing some substances to pass rapidly, and others to slow down.
Selectively Permeable Membrane: It is a membrane that facilitates the transmission of certain molecules through it by the process of diffusion.
Selfing: Selfing is a process wherein a plant's stigma is pollinated with pollen either from the same plant, or from a plant of identical genetic constitution.
Sepal: The sepal is the outermost part of a flower, resembling a leaf, which forms the calyx of the flower and surrounds its reproductive organs.
Septum: In botany, septum is a partition wall between two tissues.
Sessile: The term sessile, meaning without a stalk, is most often used in context of plants whose flowers or leaves grow directly from the stem.
Seta: Seta is a botanical term used to refer to the stalk of the capsule, which is located in between the foot and the sporangium.
Sieve Cell: Sieve cells are conducting cells of the secondary phloem, which have a narrow diameter and are more elongated in shape as compared to the sieve tube members.
Sieve Plate: Sieve plates are the pores, in the cell walls of the plant, which facilitate the movement of liquid matter.
Sieve Tube: Sieve tube is a tube formed by cells joined end-to-end in order to facilitate the flow of nutrients in flowering plants.
Simple Cone: A simple cone is a cone featuring only one axis or bearing only sporophylls.
Simple Leaf: A simple leaf is a single leaf blade sporting a bud at the base of the leaf-stem.
Sink: Sink is a botanical term used to refer to any tissue which receives the material that is transported by the phloem.
Siphonostele: Siphonostele is a type of stele, usually characterized by the formation of cylinder surrounding the central pith and possessing leaf gaps.
Softwood: Softwood refers to any of the various varieties of trees, usually coniferous, sporting narrow, needle like leaves.
Species: The term species is used to refer to a taxonomic group of plants or animals whose members can interbreed.
Spermatophytes: Spermatophytes are the plants that reproduce by means of seeds, instead of spores.
Spindle: Spindle is the underlying structure of microtubules which pulls away the chromosomes from the center of the cell, towards the poles during the process of nuclear division.
Spirillum: The term spirillum is used to refer to the spirally twisted bacteria, resembling an elongated rod, which is usually found in stagnant water.
Spongy Mesophyll: Spongy mesophyll are irregularly shaped and distinctly spaced parenchyma cells present in plant leaves.
Sporangium: The term sporangium is used to refer to a plant structure which produces and contains spores.
Spore: A spore is a unicellular asexual reproductive body in several nonflowering plants that facilitates the development of a new individual without sexual fusion.
Sporophyll: A sporophyll is a modified leaf bearing sporangia.
Sporophyte: Sporophytes are those plants which produce spores by the process of meiosis in order to produce gametophytes.
Stamen: The male organ of the flower consisting of the anther and the slender filament meant to hold it in position is known as the stamen.
Start Codon: The term start condon is used to refer to a set of three nucleotides which indicate the initiation of information for the process of protein synthesis.
Stigma: The place at the apex end of the style, where the pollen that's deposited enters the pistil is known as stigma.
Stipules: Stipules are small leafy outgrowths, usually occurring in pairs, observed at the base of a leaf or the stalk.
Stoma: Stoma is a minuscule epidermal pore in the leaf or stem of the plant which allows gases and water vapor to pass through.
Stop Codon: The term stop codon is used to refer to the set of three nucleotides which indicate the termination of information for the process of protein synthesis.
Stroma Reactions: These are the set of reactions which occur in the stroma during the process of photosynthesis, without being directly powered by light.
Stromatolite: The stromatolite is a biological fossil representing colonies of bacteria, usually cyanobacteria, alternating with sediment layers.
Structural Region: It is the part of the gene, comprising nucleotide triplets, that specifies which amino acids are to be incorporated into protein.
Style: In plants, style is a narrow elongated part of the pistil, located between the ovary and the stigma.
Substrate Level Phosphorylation: It is the formation of adenosine triphosphate (ATP) from adenosine diphosphate (ADP) by transferring a phosphate group from a substrate molecule.
Substrate Specificity: In botany, the term substrate specificity is used to refer to the ability of a given enzyme to distinguish one substrate from other similar substrates.
Suspensor: The suspensor is the cell or filament supporting a gamete, most often observed in a zygospore.
Sympatric Speciation: The speciation, i.e. the evolution of a biological species, which occurs within a limited geographical area is known as sympatric speciation.
Symplast: The inner side of the plasma membrane, wherein water and low molecular solutes diffuse freely is known as the symplast of the plant.
Synapsis: The pairing of two homologous chromosomes which occurs during the process of meiosis is known as synapsis.
Syngamy: Syngamy is the process fusion of a sperm and an egg.

Taxis: The movement of a cell that is triggered by external stimulus, towards or away from the stimulus source, is known as taxis.
Tendril: Tendril is a narrow stem-like structure which helps the twining plants in attaching themselves to an object in order to gain support from it.
Test Cross: The test cross is a process wherein a suspected heterozygote is tested by crossing it with a known homozygous recessive.
Thallus: Thallus is a plant which doesn't feature true stems, roots, leaves or vascular system.
Thorn: Thorns, also referred to as spines, are the leaves of plants which are modified into cylindrical, hard structures featuring sharp ends.
Thylakoid: The thylakoid is a membrane-bound compartment within the chloroplasts and cyanobacteria which is a site for the light-dependent reactions of photosynthesis.
Tinsel Flagellum: A flagellum which is covered with several minuscule hairlike projections is referred to as tinsel flagellum.
Tip Layering: Tip layering is a plant propagation method wherein only the stem tip is buried in order to facilitate the growth of a new plant.
Tissue: A tissue is an ensemble of cells featuring similar structure and performing a specific function.
Tissue Culture: Tissue culture is a process wherein various cells are separated from each other and grown outside the body, on a culture medium.
Tracheid: The elongated cells in the xylem which facilitate the transportation of water and mineral salts within the plants are known as tracheids.
Transcription: A process facilitated by the enzymes to transcribe the information of a DNA strand into a complementary RNA(tRNA) strand is known as transcription.
Transformation: The modification of a cell by the intake and incorporation of an exogenous DNA is known as transformation.
Transgenic Plant: A plant which contains DNA inserted by some form of genetic engineering is known as transgenic plant.
Translation: The term translation is used to refer to a process wherein the sequence of amino acids is facilitated during protein synthesis by the information in an mRNA strand.
Translocation: The process of transportation of dissolved material within a plant is referred to as translocation.
Transpiration: In botanical studies, the process of emission of water vapor from the plant leaves is known as transpiration.
Transposons: The sequences of DNA which can move to different positions within the genome of a single cell through the process of transposition.
Transposition: A form of chromosomal mutation wherein a chromosomal segment is transferred to a new position on the same or some other chromosome.
Trichome: Trichomes are the various extensions developing from the epidermis of the plant which are meant to provide protection to the plant.
Tropism: A biological process, which indicates the growth of a plant, in response to the environmental stimulus is known as tropism.
Tuber: The various types of modified plant structures which are enlarged to store nutrients are known as tubers.
Tubulin: Tubulin is a protein which leads to formation of microtubules on polymerization.
Turgid: In botany, the word turgid is used to refer to a plant with swollen tissues which are filled with moisture.
Turgor Pressure: The outward pressure exerted by the water in the plant cells, which adds to the rigidity of these cells, is known as the turgor pressure.
Tylosis: The tylosis is the process wherein an outgrowth from a parenchyma cell, through the pit cavity into a vessel, leads to the blockage of the vessel.

Unisexual: Flowers that have either the pistil or the stamen are referred to as unisexual flowers.
Uniparental Inheritance: Genetic inheritance obtained from just one parent, and is generally the case for mitochondrial and plastid genes.

Vacuolar Membrane: The membrane sheathing the cell vacuole.
Vacuole: Fluid pocket separated from the cell cytoplasm by a membrane, which mostly occupies about 99% of the cell's volume, and stores dissolved matter.
Vascular Bundle: Column of tissue comprising mostly phloem and xylem, which are usually enveloped by a bundle sheath.
Vascular Cambium: Meristem present in the form of narrow cylindrical sheath, that produces secondary xylem and phloem in the roots and stems.
Vascular Plant: Plants possessing the vascular tissues i.e. xylem and phloem are termed as vascular plants.
Vein: Branching network formed within the leaves by any of the vascular bundles is termed as vein.
Velamen Root: Aerial root capable of preventing water loss due to its multilayered epidermis.
Venter: Egg's site in the large basal region of the archegonium.
Vernalization: Cold treatment required to initiate flowering in biennials.
Vessel: Occur in xylem of some vascular plants and most of the angiosperms. They appear as cylindrical tubes, whose cell cytoplasm has been lost. Vessels consist of vessel members that are laid from one end to another.
Vessel Element: Single conducting cells of the xylem featuring a few perforations, which permit flow of water from one vessel to another.
Viability: Seed's or spore's ability to germinate.

Water Potential: Amount of water that can be absorbed or released by a substance with respective to another substance is termed as water potential.
Water-splitting (Photolysis): Phenomenon occurring in photosystem II of the process of photosynthesis, wherein water molecules split to release oxygen.
Webbing: According to telome theory of megaphyll origin, the lamina originated from parenchymatic cell production between the telomes.
Whiplash Flagellum: Flagella featuring smooth surfaces are termed as whiplash flagellum.
Whorled: Arrangement of three or more leaves, flowers or other plant structures positioned at a node.
Wood: Secondary xylem produced in the stems of trees and other woody plants is called wood. Wood present in living trees perform the function of transferring water and nutrients to growing tissues.

Xylem: The portion of conducting vascular tissue that conducts water and dissolved minerals. It contains several types of cells such as tracheids, vessel elements, parenchyma, sclereids, fibers, etc.

Yeasts: Unicellular ascomycetes which lack mycelium. In yeasts individual cells itself perform the functions of a large mycelium.

Zone of Elongation: Root tip region which lies toward the root apical mersitem, where pronounced elongation of cells takes place.
Zoospore: Motile spore capable of swimming. Occurs in fungi and algae.
Zosterophyllophytes: Bunch of early vascular plants possessing xylem and exarch prostele. They also feature lateral sporangia which open transversely on the top edge.
Zygosporangium: Large multinucleate sporangium produced by the fusion of two compatible hyphae in Zygomycete fungi.
Zygote: Diploid cell conduced by the fusion of two gametes.