Plant Biology Concepts

This set of flashcards covers key concepts in plant biology, including cell types, structures, processes, and reproductive stages.

Bark

The outer protective covering of woody plants, consisting of all tissues outside the vascular cambium, including secondary phloem, cork cambium, and cork, which protect against physical damage and water loss.

Central zone

Region of the apical meristem containing slowly dividing stem cells that maintain the meristem and supply cells to surrounding regions.

Cork cambium

A lateral meristem that produces cork (phellem) outward and sometimes phelloderm inward, forming part of the periderm for protection.

Cortex

Ground tissue located between the epidermis and vascular tissue, primarily involved in storage (often starch) and sometimes photosynthesis.

Dermal tissue

The outermost tissue system of plants that provides protection and regulates gas exchange and water loss.

Epidermis

The outermost single-cell layer in primary plant bodies, often covered by a waxy cuticle and containing specialized cells like guard cells.

Ground tissue

Tissue system that makes up most of the plant body, functioning in photosynthesis, storage, and structural support.

Mitosis

A process of nuclear division that produces two genetically identical diploid daughter cells, maintaining chromosome number.

Phloem

Living vascular tissue responsible for transporting sugars, amino acids, and signaling molecules from source to sink via pressure-flow.

Pith

Central region of stems composed mainly of parenchyma cells used for storage and sometimes transport.

Root Cap

A protective structure at the root tip that shields the apical meristem and aids in gravity sensing.

Vascular Cylinder (Stele)

The central core of roots or stems containing vascular tissues (xylem and phloem) and associated supporting cells.

Sieve Tube

Specialized phloem cells aligned end-to-end that conduct sugars; lack nuclei at maturity.

Sieve Plate

Porous end walls between sieve tube elements that facilitate cytoplasmic flow.

Companion Cells

Metabolically active cells associated with sieve tubes that load/unload sugars and maintain sieve tube function.

Apical meristem

Region of actively dividing cells at root and shoot tips responsible for primary (length) growth.

Axillary meristem

Meristematic tissue located at leaf axils that can develop into lateral branches or flowers.

Collenchyma Cell

grouped in strands, and help support young parts of plant shoot, have thicker and uneven cell walls. You put in places where plant is growing still because these cells can stretch

Parenchyma Cell

Relatively unspecialized living cells with thin walls, involved in metabolism, storage, and regeneration.

Sclerenchyma Cell

Dead at maturity, thick-walled cells (lignified) that provide rigid structural support (fibers and sclereids).

Quiescent center

A region of infrequently dividing cells in the root apical meristem that helps maintain surrounding stem cells.

Vascular cambium

A lateral meristem that produces secondary xylem inward and secondary phloem outward, increasing girth.

Vascular tissue

Complex tissue system (xylem + phloem) responsible for long-distance transport of water, minerals, and nutrients.

Xylem

Dead, lignified vascular tissue that transports water and dissolved minerals upward via transpiration pull.

Vessel elements (Vessel tubes)

Wide, short xylem cells joined end-to-end, optimized for efficient water transport.

Tracheids

Long, narrow xylem cells with tapered ends that transport water and provide structural support.

Zone of cell division

Region near root tip where cells undergo mitosis.

Zone of elongation

Region where cells elongate, contributing to root growth in length.

Zone of differentiation

Region where cells mature into specialized types (e.g., root hairs, vascular cells).

Multicellular Haploid

A multicellular organism or life stage with one set of chromosomes, typically producing gametes by mitosis (gametophyte).

Multicellular Diploid

A multicellular organism or life stage with two sets of chromosomes, producing spores by meiosis (sporophyte).

Unicellular Haploid

A single-celled organism or stage with one chromosome set, often a spore or gamete.

Meiosis

A two-step division process reducing chromosome number by half, producing genetically diverse haploid cells.

Embryo

The young diploid organism formed from a zygote, which develops into the mature plant.

Gametes

Haploid reproductive cells (egg and sperm) that fuse during fertilization.

Egg

The non-motile female gamete, typically retained within the parent tissue in plants.

Sperm

The male gamete, delivered to the egg via pollen in seed plants.

Fertilization

The fusion of haploid gametes to form a diploid zygote.

Double fertilization

Unique to angiosperms: one sperm fertilizes the egg (zygote), another fuses with polar nuclei to form endosperm.

Sporophyte

The diploid generation that produces haploid spores via meiosis.

Gametophyte

The haploid generation that produces gametes via mitosis.

Sporangium

A structure in which spores are produced by meiosis.

Zygote

The diploid cell formed by fertilization, initiating a new sporophyte.

Spore

A haploid reproductive cell that can develop into a gametophyte without fertilization.

Gymnosperm

Seed-producing plants with exposed (“naked”) seeds, not enclosed in fruits.

Generative Cell

A cell within pollen that divides mitotically to produce two sperm cells.

Fibrous root

A root system of many similarly sized roots that increases surface area for absorption.

Taproot

A dominant central root that grows deep and provides anchorage and storage.

Pericycle

A layer of cells just inside the endodermis that gives rise to lateral roots.

Lateral root

Roots that branch off from the primary root, increasing absorption capacity.

Apoplastic route

Movement of water through cell walls and extracellular spaces without crossing membranes.

Casparian strip

A band of suberin in endodermal cells that blocks apoplastic flow, forcing selective uptake.

Symplastic route

Movement of water through cytoplasm via plasmodesmata.

Plasma membrane

A selectively permeable lipid bilayer controlling movement into and out of cells.

Endodermis

Innermost cortical layer regulating entry of water and solutes into the vascular cylinder.

Source Cell (leaf)

A photosynthetic cell that exports sugars into the phloem.

Sink cell

A cell or tissue that imports and stores or uses sugars (e.g., roots, fruits).

Transpiration

Evaporation of water from plant surfaces, driving upward water movement.

Translocation

Movement of sugars through phloem via pressure-flow mechanism.

Dicot (Eudicot)

Angiosperm with two cotyledons, net-veined leaves, and vascular bundles in a ring.

Cotyledon

Secrets enzymes that breaks down all food in endosperm and feeds embryo

Coleoptile

A protective sheath covering the emerging shoot in monocots.

Radicle

The embryonic root that develops first during germination.

Pressure Potential (Ψp)

The physical pressure exerted on water within a cell, contributing to turgor.

Solute Potential (Ψs)

The effect of dissolved solutes lowering water potential, driving osmosis.

Guard Cells

Paired epidermal cells that regulate stomatal opening and closing.

Receptacle

The base of a flower where floral organs attach.

Sporopollenin

A highly resistant biopolymer forming the outer wall of spores and pollen.

Polar nuclei

Two nuclei in the embryo sac that fuse with a sperm cell to form endosperm.

Monocot

Angiosperm with one cotyledon, parallel veins, and scattered vascular bundles. (grasses, palm trees)

Palisade mesophyll

Tightly packed photosynthetic cells rich in chloroplasts beneath the upper epidermis.

Spongy mesophyll

Loosely arranged cells with air spaces for gas exchange.

Stamen

Male reproductive structure consisting of filament and anther (produces pollen).

Ovule

Structure containing the female gametophyte that develops into a seed after fertilization.

Sepal

Protective outer floral structure enclosing the bud.

Petal

Often colorful structure that attracts pollinators.

Microspore

Haploid cell that develops into a male gametophyte (pollen grain).

Carpel

Female reproductive structure consisting of ovary, style, and stigma.

Megaspore

Haploid cell that develops into the female gametophyte.

Bryophytes

Nonvascular plants with dominant gametophyte stage (e.g., mosses).

Coevolution

Reciprocal evolutionary changes between interacting species.

Seedless vascular plants

Plants with vascular tissue but no seeds, reproducing via spores (e.g., ferns).

Angiosperm

Flowering plants with seeds enclosed within fruits.

Rhizosphere

The soil region influenced by root secretions and microbial activity.

Sugar source/sink

Dynamic relationship where sugars move from producing tissues (sources) to using/storage tissues (sinks).

Waxy cuticle

Hydrophobic layer covering epidermis to reduce water loss.

Macronutrients

Essential elements required in large quantities (e.g., N, P, K).

Micronutrients

Essential elements required in trace amounts (e.g., Fe, Zn).

Mycorrhizal fungi

Symbiotic fungi that enhance plant nutrient and water uptake.

Plasmodesmata

Cytoplasmic channels connecting adjacent plant cells for communication.

Charophytes

Green algae closely related to land plants, sharing key traits.

Embryo sac

Female gametophyte within the ovule containing egg and polar nuclei.

Endosperm

Triploid nutritive tissue formed by double fertilization in angiosperms.

Cohesion/Adhesion

Properties of water where molecules stick to each other (cohesion) and to surfaces (adhesion), enabling transport in xylem.

Schlernechyma cells

Usually dead because they thicken themselves with lignin, providing structural support in plants.