BIO 152: Exam #2 Vocabulary Guide - Plant Physiology, Life Cycles, Anatomy & Transport

Comprehensive vocabulary flashcards covering plant life cycles, ploidy, floral anatomy, evolutionary lineages, tissue systems, water relations, photosynthesis pathways, vascular transport mechanisms, and hormonal growth responses for BIO 152 Exam #2.

Alternation of Generations

The land plant life cycle that alternates between a multicellular haploid ($n$) gametophyte phase and a multicellular diploid ($2n$) sporophyte phase.

Sporophyte

The multicellular diploid ($2n$) generation that produces haploid spores via meiosis; dominant in vascular plants, gymnosperms, and angiosperms.

Gametophyte

The multicellular haploid ($n$) generation that produces haploid gametes (egg and sperm) via mitosis; dominant in bryophytes.

Gametes

Haploid ($n$) reproductive cells (egg and sperm) that fuse during fertilization to form a diploid ($2n$) zygote.

Spores

Single haploid ($n$) cells formed by the sporophyte via meiosis; divide by mitosis to form a multicellular haploid gametophyte.

Zygote

The single diploid ($2n$) cell formed by the fusion of an egg cell and a sperm cell during fertilization.

Endosperm

Triploid ($3n$) nutritive tissue formed in angiosperm seeds during double fertilization when a sperm fuses with two polar nuclei.

Polar Nuclei

Two haploid ($n$) nuclei in the central cell of the female gametophyte (embryo sac) that fuse with a sperm cell to form $3n$ endosperm.

Double Fertilization

A unique angiosperm mechanism where one sperm fertilizes the egg to form a $2n$ zygote, while a second sperm fertilizes two polar nuclei to form $3n$ endosperm.

Embryo

The developing young diploid ($2n$) sporophyte contained within a seed, nourished by endosperm or female gametophyte tissue.

Mitosis / Meiosis

Mitosis preserves chromosome count ($n \rightarrow n$ or $2n \rightarrow 2n$; produces gametes in gametophytes). Meiosis halves chromosome count ($2n \rightarrow n$; produces spores in sporophytes).

Ploidy ($n$, $2n$, $3n$)

Chromosome content level: haploid ($n$; spores, gametes, gametophyte), diploid ($2n$; zygote, embryo, sporophyte), or triploid ($3n$; angiosperm endosperm).

Stamen (Anther & Filament)

The male reproductive floral organ. The Anther contains pollen sacs where pollen develops; the Filament is the supporting stalk.

Carpel / Pistil

The female floral structure consisting of the Stigma (pollen landing surface), Style (pollen tube pathway), Ovary (swollen base), and Ovule (contains female gametophyte).

Ovule

Structure inside the flower ovary containing the female gametophyte (embryo sac); develops into a seed after fertilization.

Pollen / Pollination / Pollen tube

Pollen is the male gametophyte ($n$). Pollination is pollen transfer to the stigma. The Pollen tube grows down the style to deliver sperm to the ovule.

Sepal

Outer leaf-like whorl of floral organs protecting the developing flower bud before opening.

Charophytes / Green Algae

Freshwater green algae representing the closest living algal relatives of land plants.

Bryophytes (Mosses)

Non-vascular land plants (mosses, liverworts, hornworts) with a dominant gametophyte generation and a dependent, unbranched sporophyte.

Ferns

Seedless vascular plants with independent, photosynthetic sporophyte and gametophyte generations; reproduce via wind-dispersed spores.

Gymnosperms

Vascular seed plants with 'naked seeds' not enclosed in an ovary/fruit (e.g., conifers, cycads, Ginkgo).

Angiosperms

Flowering plants producing seeds enclosed within fruits and undergoing double fertilization; dominant terrestrial plant group.

Monocot / Eudicot

Major angiosperm clades: Monocots have 1 cotyledon, parallel venation, and scattered stem vascular bundles. Eudicots have 2 cotyledons, net venation, and ringed stem bundles.

Vascular System

Internal conducting tissue network consisting of xylem (water/minerals) and phloem (sugars/nutrients).

Dermal, Vascular & Ground Tissue

Three primary tissue systems: Dermal (outer epidermis/cuticle), Vascular (xylem/phloem transport), Ground (photosynthesis, storage, support).

Primary Growth

Lengthwise growth originating from apical meristems at root and shoot tips.

Secondary Growth

Increase in stem and root girth driven by lateral meristems (vascular cambium and cork cambium) producing wood and bark.

Meristem

Regions of undifferentiated, perpetually dividing cells that drive continuous plant growth.

Zones of Primary Growth

Zone of Cell Division (mitosis in apical meristem), Zone of Elongation (cells expand via water uptake), Zone of Differentiation (cells mature into functional tissues).

Endodermis

Innermost layer of root cortex surrounding the vascular cylinder that selectively regulates solute entry into xylem.

Cork

Waxy, protective outer bark layer produced by cork cambium during secondary growth.

Root Hair Cell & Fine Roots

Root hair cells are epidermal outgrowths in the zone of differentiation that expand absorption surface area. Fine roots are primary water/nutrient absorbers.

Water Potential ($\Psi$)

The chemical potential of water relative to pure water ($0\,\text{MPa}$); dictates direction of water flow ($\Psi = \Psi_P + \Psi_S$). Water moves from higher to lower $\Psi$.

Solute Potential ($\Psi_S$)

Osmotic potential component; $0\,\text{MPa}$ for pure water and becomes increasingly negative as solute concentration increases.

Pressure Potential ($\Psi_P$)

Physical hydrostatic pressure on water; positive in turgid living cells (turgor pressure) and negative (tension) in xylem conduits.

Diffusion

Passive movement of solute molecules down a concentration gradient.

Osmosis

Net diffusion of water molecules across a selectively permeable membrane toward lower water potential.

Mass Flow (Bulk Flow)

Long-distance liquid transport driven by a physical pressure gradient ($\Delta \Psi_P$) independent of concentration gradients.

Apoplast / Symplast

Apoplast is the non-living pathway (cell walls, xylem lumens, air spaces). Symplast is the continuous living cytoplasm connected by plasmodesmata.

Plasmodesmata

Microscopic channels traversing cell walls, linking cytoplasm of adjacent plant cells.

Cohesion / Adhesion

Cohesion is hydrogen bonding between water molecules. Adhesion is hydrogen bonding between water molecules and polar cell wall cellulose.

Surface Tension & Heat of Vaporization

Surface tension creates menisci in leaf microfibrils generating negative tension. High heat of vaporization provides evaporative leaf cooling.

Transpiration

Evaporative loss of water vapor from leaf interior to atmosphere through open stomata.

Cohesion-Tension Theory

Model explaining xylem transport: evaporation at leaf cell wall menisci generates negative pressure (tension), pulling cohesive water columns upward from roots.

Turgor & Turgor Pressure

Cell firmness resulting from positive pressure potential ($\Psi_P$) pressing cytoplasm against the rigid plant cell wall.

Epidermis & Guard Cells

Epidermis is the outer protective cell layer. Guard cells are specialized paired cells that regulate opening/closing of stomatal pores.

Stomata & Stomatal Conductance

Stomata are leaf pores for gas exchange ($CO_2$ uptake, $H_2O$ loss). Stomatal conductance measures rate of gas flux through stomata.

Palisade & Spongy Mesophyll

Palisade mesophyll consists of columnar cells packed with chloroplasts for main photosynthesis. Spongy mesophyll has air spaces for gas diffusion and light backscatter.

Bundle Sheath Cells

Ring of cells enclosing vascular veins; in $C_4$ plants, they contain RuBisCO and Calvin cycle enzymes for spatial $CO_2$ concentration.

Apoplastic vs. Symplastic Opening

Stomatal opening relies on $H^+\text{-ATPase}$ proton pumps driving $K^+$ and anion influx into guard cells, lowering $\Psi_S$ so water enters by osmosis to increase turgor.

Chlorophyll & Light Reactions

Chlorophyll absorbs light energy. Light reactions in thylakoids split $H_2O$, release $O_2$, and generate ATP and NADPH for the Calvin cycle.

Calvin Cycle & RuBisCO

Stroma reactions fixing $CO_2$ into sugars. RuBisCO is the primary $CO_2$-fixing enzyme, but can also bind $O_2$ causing photorespiration.

Photorespiration

Wasteful metabolic process where RuBisCO fixes $O_2$ instead of $CO_2$ under hot/dry conditions, consuming ATP and releasing fixed carbon.

PEP Carboxylase (PEP-C)

Enzyme in $C_4$ and CAM plants that fixes $CO_2$ into a 4-carbon organic acid with high affinity for $CO_2$ and zero affinity for $O_2$.

C3, C4, and CAM Photosynthesis

C3: direct $CO_2$ fixation by RuBisCO in mesophyll. C4: spatial separation (PEP-C in mesophyll, RuBisCO in bundle sheath). CAM: temporal separation (night $CO_2$ fixation, day Calvin cycle).

Xylem

Vascular tissue composed of dead, lignified cells (tracheids & vessel elements) conducting water/minerals upward under negative pressure (tension).

Phloem

Living vascular tissue that conducts sugar-rich phloem sap throughout the plant body.

Sieve Tube Elements & Companion Cells

Sieve tube elements are elongated living cells lacking nuclei forming phloem conduits. Companion cells regulate metabolic loading into sieve tubes.

Source / Sink

Source is a net sugar exporter (mature leaf). Sink is a net sugar importer/consumer (growing root, shoot tip, fruit, storage tuber).

Phloem Loading & Sucrose

Active transport of sucrose (the main transport sugar) into sieve tubes at sources, lowering $\Psi_S$ and drawing in water by osmosis.

Pressure-Flow Hypothesis

Mechanism of phloem translocation: active sugar loading at source builds high positive pressure ($\Psi_P$), driving mass flow of sap toward sink where sugar is unloaded.

Auxin

Key plant hormone synthesized in shoot tips that promotes cell elongation on the shaded side of stems.

Acid Growth Hypothesis

Auxin activates $H^+\text{-ATPase}$ proton pumps, acidifying the cell wall. Low pH activates expansins to cleave microfibril cross-links, enabling turgor-driven cell expansion.

Cellulose Microfibrils

Strong cellulose bundles in cell walls whose structural alignment constrains direction of cell expansion.

Proton Pump (H+-ATPase)

Membrane enzyme that uses ATP to pump protons across membranes, creating electrochemical and pH gradients.

Tropism

Directional growth movement toward or away from an environmental stimulus (Phototropism = light; Gravitropism = gravity; Chemotropism = chemical signal).