General Botany - Plant Cells, Tissues, and Organ Systems

Vocabulary flashcards covering plant tissues, cell structure, organ systems, secondary growth, membrane transport, and plant responses from General Botany lectures.

Tissue

A group of cells having similar origin, structure, and function.

Meristematic Tissues

Plant tissues composed of undifferentiated cells capable of continuous cell division and growth.

Permanent Tissues

Plant tissues derived from meristematic tissues that no longer divide, having fixed shapes and sizes specialized for support, transport, or photosynthesis.

Totipotency

The ability of a single plant cell to regenerate into a whole plant under appropriate conditions, based on genetic potential retained in somatic cells.

Plant Tissue Culture

A biotechnological process based on totipotency where explants are cultured on nutrient- and hormone-supplemented agar media to regenerate whole plantlets.

Apical Meristems

Meristems located at root and shoot tips that drive primary growth (lengthening of the plant body).

Intercalary Meristems

Meristems located at nodes or internodes (common in monocots) that assist in lengthening between mature stem regions.

Lateral Meristems

Meristems located along the length of roots and shoots (such as vascular cambium and cork cambium) responsible for secondary growth (increasing thickness).

Protoderm

A primary meristem that forms the epidermis, serving as an outer protective barrier against physical damage, pathogens, and water loss.

Procambium

A primary meristem that differentiates into primary vascular tissues (primary xylem and primary phloem).

Ground Meristem

A primary meristem that produces ground tissue systems including parenchyma, collenchyma, and sclerenchyma.

Dermal Tissue System

The outermost layer of plant tissue that provides protection and gas exchange in shoots, and protection plus water and nutrient absorption in roots.

Cuticle

A waxy layer forming a continuous sheet on shoot epidermal surfaces to minimize water loss and protect against pathogen invasion.

Stomata

Epidermal pores flanked by specialized guard cells that regulate the entry of $CO_2$ and the release of $O_2$ during photosynthesis.

Trichomes

Hairlike epidermal appendages that reflect sunlight to cool leaves, reduce transpiration, release defense toxins or barbs, or trap insects.

Parenchyma

A versatile simple ground tissue with thin primary cell walls involved in photosynthesis, sugar synthesis, and storage; many cells retain totipotency.

Collenchyma

A simple ground tissue with unevenly thickened primary cell walls that provides flexible structural support to actively growing shoots and leaves.

Sclerenchyma

A rigid ground tissue characterized by thick, lignified secondary cell walls that are dead at maturity; comprises elongated fibers and short, protective sclereids.

Xylem

A complex vascular tissue that transports water and dissolved nutrients upward from roots to shoots while providing structural support.

Phloem

A complex vascular tissue that transports sugars, amino acids, hormones, and organic nutrients throughout the plant.

Tracheids

Long, tapered water-conducting cells in xylem containing pits through which water moves; dead at maturity and present in all vascular plants.

Vessel Elements

Short, wide water-conducting cells in angiosperm xylem containing perforations and pits for efficient sap conduction; dead at maturity.

Sieve-Tube Elements

Long, living phloem conducting cells that lack nuclei at maturity and possess perforated end walls termed sieve plates.

Companion Cells

Living phloem cells rich in organelles that maintain the cytoplasm and metabolic functions of adjacent sieve-tube elements via plasmodesmata.

Zone of Cellular Elongation

The root tip region behind the apical meristem where newly produced cells increase significantly in length.

Zone of Cellular Maturation

The root region where cells complete differentiation into dermal, vascular, or ground tissues and absorb nutrients and water through root hairs.

Vascular Cambium

A lateral meristem located between secondary xylem and secondary phloem that produces secondary xylem (wood) inward and secondary phloem outward.

Cork Cambium

A lateral meristem situated near the stem perimeter that produces protective cork cells outward to form the outer bark.

Bark

The collective outer protective covering of a woody stem or root, composed of secondary phloem, cork cambium, and cork cells.

Lenticels

Small raised pores or openings in the bark of woody stems that facilitate gas exchange between internal tissues and the atmosphere.

Heartwood

The older, dark-colored inner secondary xylem of a tree trunk that accumulates protective resins/gums and provides structural support without conducting water.

Sapwood

The younger, light-colored outer secondary xylem of a tree trunk that actively conducts water and dissolved nutrients.

Tonicity

The capability of an extracellular solution to alter cell volume by causing water to move into or out of the cell via osmosis.

Hypertonic Solution

A solution having a higher solute concentration (and lower water potential) than the cytosol inside a cell, causing net water efflux.

Hypotonic Solution

A solution having a lower solute concentration (and higher water potential) than the cytosol inside a cell, causing net water influx.

Simple Diffusion

The unassisted passive movement of solute particles down their concentration gradient across a lipid bilayer without energy consumption.

Facilitated Diffusion

The passive movement of solutes down their concentration gradient across a membrane mediated by specific transmembrane transport proteins.

Active Transport

The transmembrane movement of a solute against its concentration gradient driven by carrier proteins and requiring energy consumption ($ATP$).

Flippase

An enzyme that utilizes energy from $ATP$ hydrolysis to transfer specific membrane lipids from one leaflet of the phospholipid bilayer to the opposite leaflet.

Tonoplast

The selectively permeable vacuolar membrane that encloses the central vacuole of a plant cell.

Cell Sap

The liquid stored within the central vacuole containing water, inorganic salts, sugars, organic acids, proteins, and water-soluble anthocyanin pigments.

Calcium Oxalate Crystals

Insoluble crystalline deposits stored in plant vacuoles (e.g., in Dieffenbachia) that deter herbivores by causing severe oral tissue irritation and inflammation.

Middle Lamella

An intercellular layer composed primarily of pectin that glues adjacent primary cell walls together.

Primary Cell Wall

A thin, extensible cell wall layer synthesized during cell division and growth, composed of cellulose, hemicellulose, pectin, and glycoproteins.

Secondary Cell Wall

A rigid, multi-layered cell wall containing cellulose and lignin deposited inside the primary wall after cell expansion ceases.

Lignin

A complex phenolic polymer deposited in secondary cell walls that imparts structural rigidity, mechanical strength, and decay resistance.

Expansins

Cell wall proteins activated by lowered extracellular pH (auxin-induced proton pumping) that break hydrogen bonds between cellulose microfibrils to permit cell wall loosening.

Chloroplasts

Double-membrane bound plastids containing chlorophyll, thylakoids, grana, and stroma that carry out photosynthesis, starch storage, and fatty acid biosynthesis.

Chromoplasts

Plastids that synthesize and store carotenoid pigments (red, orange, yellow), responsible for the bright colors of fruits, flowers, and autumn leaves.

Leucoplasts

Non-pigmented plastids specialized for metabolic storage and synthesis in non-photosynthetic tissues; includes amyloplasts (starch), elaioplasts (oils), and proteinoplasts (proteins).

Plasmodesmata

Microscopic cytoplasmic channels passing through plant cell walls that allow direct intercellular transport of ions, sugars, hormones, and RNA.

Desmotubule

A tubular structure derived from the smooth endoplasmic reticulum that extends through the center of a plasmodesma to connect adjacent ER networks.

Hyperaccumulator

A plant species capable of growing in soils with elevated heavy metal content and absorbing high concentrations of metals into its tissues without toxic effects.

Secondary Plant Products

Organic compounds produced by plants that are non-essential for primary growth but function in defense, attraction, or ecological interaction (e.g., terpenes, phenolics, alkaloids).

Alkaloids

A major group of nitrogenous secondary metabolites including caffeine, ephedrine, morphine, cocaine, and quinine that exhibit pronounced physiological effects.

Tropism

The directional growth movement of a plant in response to an external environmental stimulus.

Phototropism

Directional growth in response to light, caused by the lateral redistribution of auxin to the shaded side of a stem, stimulating cell elongation toward the light source.

Thigmotropism

Directional plant growth in response to touch or physical contact, allowing tendrils and climbing vines to coil around supporting structures.

Gravitropism

Directional growth in response to gravity, causing roots to grow downward (positive gravitropism) and shoots to grow upward (negative gravitropism).

Hydrotropism

Directional growth of plant roots toward moisture gradients in the soil to maximize water absorption.

Self-Incompatibility

A biochemical recognition system in flowering plants that prevents self-fertilization by blocking the germination or growth of the plant's own pollen.

Nitrogen Fixation

The biochemical or physical process converting inert atmospheric nitrogen gas ($N_2$) into bioavailable ammonium, mediated by specialized bacteria, lightning, or industrial synthesis.

Nitrification

The biological conversion of soil ammonium into nitrates by nitrifying soil bacteria.

Assimilation

The uptake of soil nitrates by plant roots to synthesize essential organic nitrogen compounds such as amino acids and proteins.

Bryology

The subdiscipline of botanical science concerned with the study of mosses, liverworts, and hornworts.

Ethnobotany

The study of the traditional knowledge, cultural uses, and management of plants by indigenous human societies.

Phycology

The branch of botany devoted to the scientific study of algae.

Palynology

The study of plant pollen grains and spores, including their structural variations, distribution, and fossil records.

Monocots

Angiosperms characterized by a single cotyledon in the seed, parallel leaf venation, scattered vascular stem bundles, and floral organs in multiples of three.

Dicots

Angiosperms characterized by two cotyledons in the seed, netlike leaf venation, vascular stem bundles arranged in a ring, and floral organs in multiples of four or five.