Tamil Nadu HSE First Year Botany key terms

The branch of biology that identifies, names, and classifies organisms into ordered groups based on shared features, so that every species has one accepted scientific identity worldwide.

The two-part naming system introduced by Linnaeus in which each species receives a Latin genus name followed by a specific epithet, both italicised, with the genus capitalised.

Any named rank or group in a classification hierarchy, such as kingdom, division, class, order, family, genus or species, at whatever level it is being discussed.

Arrangement of organisms in nested ranks from broad to narrow, where each lower group sits inside a higher one and shares the characters of all groups above it.

A preserved reference specimen permanently linked to the original description of a new species; it fixes the meaning of the scientific name if later confusion arises.

A collection of pressed, dried, labelled plant specimens arranged systematically, used for identification, comparison and reference by botanists and students.

Chlorophyll-bearing, mainly aquatic thallophytes lacking true roots, stems and leaves; they range from unicellular forms to large seaweeds and include green, brown and red groups.

The amphibians of the plant kingdom: small terrestrial plants with a dominant gametophyte, no vascular tissue, and a sporophyte that depends on the gametophyte for nutrition.

Vascular cryptogams such as ferns and horsetails that reproduce by spores, possess xylem and phloem, and show a dominant sporophyte with an independent, leafy habit.

Seed plants whose ovules lie exposed on megasporophylls rather than enclosed in an ovary, producing naked seeds typically borne in cones; examples include Cycas and Pinus.

Flowering plants in which ovules are enclosed within an ovary that matures into fruit; they show double fertilisation and triploid endosperm, and dominate present-day vegetation.

A plant body not differentiated into true root, stem and leaf, as seen in algae and liverworts; it may be filamentous, sheet-like or branched but lacks vascular organs.

The pattern in which leaves are arranged on a stem, such as alternate, opposite or whorled, influencing how efficiently each leaf intercepts light.

The arrangement of sepals or petals in a flower bud before it opens, described as valvate, twisted, imbricate or vexillary according to how the parts overlap.

The way ovules are attached to the ovary wall or central axis, classified as marginal, axile, parietal, basal or free-central depending on the arrangement seen in a cross-section.

Conducting tissue of xylem and phloem together with associated fibres and parenchyma, which transports water, minerals and sugars and gives mechanical support to the plant.

Complex tissue of tracheary elements, fibres and parenchyma that conducts water and dissolved minerals upward from the root and provides most of the plant's mechanical strength.

An elongated, dead water-conducting cell of xylem with tapered ends, pitted walls and no perforation plates; it is the main conducting element in gymnosperms.

A short, wide, dead xylem cell whose end walls are dissolved to form perforation plates, allowing rapid water flow; vessels are typical of angiosperms.

Complex tissue containing sieve elements, companion cells, phloem fibres and parenchyma that translocates sugars and other solutes from sources to sinks.

A living phloem cell lacking a nucleus at maturity, with perforated sieve plates at its ends, through which assimilates flow; each is assisted by a companion cell.

A nucleated parenchyma cell closely associated with a sieve tube element by numerous plasmodesmata, controlling its metabolism and loading of sugars into the tube.

The selectively permeable phospholipid bilayer with embedded proteins that surrounds every cell, controlling the entry and exit of ions and molecules.

The living content of a cell, comprising cytoplasm and nucleus, together with the organelles suspended in the cytoplasmic matrix.

A membrane-bound or structurally distinct subcellular body such as a mitochondrion, chloroplast or ribosome that performs a specialised function within the cell.

A green plastid containing chlorophyll, thylakoid membranes and stroma, in which light reactions and the Calvin cycle convert carbon dioxide and water into carbohydrate.

A double-membraned organelle whose inner membrane folds into cristae; it houses the Krebs cycle and electron transport chain that generate most cellular ATP.

Nuclear division producing two genetically identical daughter nuclei with the same chromosome number as the parent, underlying growth, repair and vegetative propagation.

Reduction division of a diploid cell into four haploid cells through two successive divisions, with crossing over and independent assortment creating genetic variation in gametes and spores.

Exchange of corresponding chromosome segments between non-sister chromatids of a homologous pair during prophase I of meiosis, producing new combinations of alleles.

The haploid, gamete-producing generation in the plant life cycle; it is dominant in bryophytes but reduced to a few cells in flowering plants.

The diploid, spore-producing generation of a plant that arises from a zygote; it is the conspicuous plant body in pteridophytes, gymnosperms and angiosperms.

The unique angiosperm event in which one male gamete fuses with the egg and a second fuses with two polar nuclei, forming a zygote and triploid endosperm.

Nutritive tissue formed inside the embryo sac after fertilisation, usually triploid in angiosperms, which supplies food to the developing embryo and sometimes to the seedling.

The structure containing the embryo sac, integuments and nucellus that becomes the seed after fertilisation; it is enclosed in an ovary in flowering plants.

Pores in the epidermis bounded by two guard cells, whose turgor changes open and close the pore to regulate gas exchange and water loss.

The tension created in leaf xylem when water evaporates from mesophyll surfaces; it draws a continuous water column up the plant, supported by cohesion and adhesion.

Net movement of water across a selectively permeable membrane from a region of higher water potential to one of lower water potential, driven by a solute concentration difference.

The free energy of water per unit volume, expressed in pressure units; pure water at atmospheric pressure has zero potential and solutes lower it, so water moves from high to low potential.

The light-driven process in chloroplasts that uses water and carbon dioxide to form carbohydrate and release oxygen, converting light energy into chemical bond energy.

The light-independent sequence of reactions in the chloroplast stroma in which RuBisCO fixes carbon dioxide onto ribulose bisphosphate and the product is reduced to sugar.

The stepwise oxidation of respiratory substrates such as glucose to release energy, captured as ATP, with carbon dioxide and water as end products in aerobic conditions.

Adenosine triphosphate, the universal energy currency of cells; hydrolysis of its terminal phosphate bond releases energy that drives endergonic reactions.

The study of how plants absorb, transport and use inorganic elements, and of the deficiency symptoms that appear when an essential element is lacking.

An element required by plants in relatively large amounts, such as nitrogen, phosphorus, potassium, calcium, magnesium or sulphur, used in building major cell components.

Growing plants in nutrient solution without soil, allowing precise control of mineral supply and used to identify essential elements and their deficiency symptoms.

Transmission of traits controlled by nuclear genes following Mendel's laws of dominance, segregation and independent assortment, observed in monohybrid and dihybrid crosses.

The genetic constitution of an organism at one or more loci, described by the alleles present, which interacts with the environment to produce the observable phenotype.

Tendency of genes located close together on the same chromosome to be inherited together, so that parental combinations appear more often than recombinants in offspring.

Growing plant cells, tissues or organs aseptically on a nutrient medium containing hormones, exploiting totipotency to produce clones or whole plantlets from small explants.

Rapid clonal multiplication of plants in vitro from meristems or other explants, producing many genetically uniform plantlets free of many pathogens.

The capacity of a living plant cell to divide and regenerate into a complete organism under suitable conditions, the principle underlying tissue culture and micropropagation.