Untitled Flashcard Set

Cotransporter

Protein that moves two substances together; one moving down its gradient can power movement of another against its gradient.

Plant

Multicellular eukaryote; mostly autotrophic; chlorophyll; cellulose cell walls; alternation of generations.

Photoautotroph

Organism that uses light for energy and makes organic carbon from inorganic carbon.

Phototroph

Organism that obtains energy from sunlight.

Chemotroph

Organism that obtains energy from chemical compounds.

Autotroph

Organism that produces its own organic compounds from inorganic carbon.

Heterotroph

Organism that obtains organic carbon from other organisms or compounds.

Nutrient

Substance required for biosynthesis and normal growth.

Macronutrients in plants

Elements required in large amounts; lecture emphasizes CHONPS plus potassium, calcium, and magnesium.

Micronutrients in plants

Elements required in trace amounts, including iron, manganese, boron, molybdenum, copper, zinc, chlorine, nickel, cobalt, sodium, and silicon.

CHONPS

Carbon, hydrogen, oxygen, nitrogen, phosphorus, and sulfur.

Carbon function in plants

Backbone of carbohydrates, proteins, fats, and nucleic acids.

Nitrogen function in plants

Needed for proteins, nucleic acids, and some vitamins.

Phosphorus function in plants

Important in nucleotides and ATP.

Sulfur function in plants

Found in some amino acids, coenzymes, and vitamins.

Gaseous nutrient sources

Elements found as gases in the atmosphere or oceans; examples include oxygen, carbon, hydrogen, and nitrogen.

Sedimentary nutrient sources

Mineral salts released by weathering of rocks; examples include phosphorus, calcium, and some sulfur.

Soil

Mixture of minerals, organic materials, living organisms, air, and water covering land.

Parent material

Inorganic mineral matter in soil; often about 40-45% in the lecture's overview.

Humus

Organic matter in soil; about 5% in the lecture's overview.

Soil horizons

Distinct vertical layers created during soil formation.

Soil profile

Vertical slice showing the different soil horizons.

Weathering

Physical or chemical breakdown of rock into smaller particles.

Sand particle size

0.063-2.0 mm in diameter.

Silt particle size

0.004-0.063 mm in diameter.

Clay particle size

Less than 0.004 mm in diameter.

Soil texture

Relative proportion of sand, silt, and clay in a soil sample.

Loam

Soil with a reasonable mix of sand, silt, and clay; retains nutrients and some water while draining adequately.

Leaching

Loss of dissolved nutrients as water moves through soil.

Soil aeration

Availability and movement of air, including oxygen, through soil spaces.

Why overwatering can harm roots

Water fills soil air spaces and limits oxygen supply to roots.

Soil compaction effects

Reduces aeration and infiltration and increases runoff.

Root hairs

Root extensions that increase surface area for water and mineral absorption.

Concentration gradient

Difference in concentration that drives diffusion from higher to lower concentration.

Surface area and absorption

Greater surface area generally increases absorption rate.

Proton pump

Membrane protein that uses ATP to move H+ across a membrane.

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Parasitic plant

Plant that obtains resources from a host plant.

Holoparasite

Parasitic plant that depends entirely on its host for nutrition.

Hemiparasite

Parasitic plant that obtains some resources from a host but can photosynthesize.

Mycoheterotroph

Plant that obtains nutrients entirely from fungi; typically lacks green coloration.

Insectivorous plant

Plant in nutrient-poor soil that obtains minerals, often nitrogen, from prey.

Mycorrhizal association

Mutualistic fungus-root association; fungus supplies nutrients and plant supplies carbohydrates.

Gas exchange in plants

Plants mainly take in CO2 and release O2 during photosynthesis; they also use O2 in respiration.

Why plants lack specialized gas-exchange organs

Each part can exchange gases; respiration is relatively slow; living cells are near the surface; air spaces aid diffusion.

Cuticle

Waxy layer that protects the plant and reduces water loss.

Palisade mesophyll

Tightly packed, column-shaped leaf cells rich in chloroplasts; major photosynthetic tissue.

Spongy mesophyll

Loosely arranged leaf cells with air spaces that facilitate gas exchange.

Stomata

Small openings, often on the lower leaf epidermis, that allow gas exchange and water-vapor loss.

Guard cells

Cells that control stomatal opening and closing.

Transpiration

Evaporation/loss of water vapor from plant surfaces, especially leaves.

CO2 in plants

Released by respiration but used in photosynthesis; usually diffuses from air into leaves.

O2 in plants

Released by photosynthesis and used in cellular respiration.

Guard-cell turgor

Water-filled guard cells become turgid and open stomata; loss of water makes them flaccid and closes stomata.

Stomatal opening sequence

Light activates ATP production and H+ pumps; H+ exits; K+ and Cl− enter; water potential decreases; water enters guard cells; stomata open.

Stomatal closing sequence

Abscisic acid signals ion release; solute conditions change; water leaves guard cells; cells lose turgor; stomata close.

Abscisic acid and stomata

ABA promotes stomatal closure during low light or low water availability and helps limit water loss.

Factors affecting stomata

Light, temperature, humidity, and CO2 concentration can affect stomatal number or activity.

Lenticels

Pores in stems or other tissues that allow gas exchange where cork layers block diffusion.

Homeostasis

Maintenance of relatively stable internal conditions despite external changes.

Regulator

Organism that maintains a relatively stable internal condition despite environmental variation.

Conformer

Organism whose internal condition changes with the external environment.

Trade-off in environmental tolerance

Coping with stressful conditions uses energy that could otherwise support other functions.

Plant hormone

Chemical signal that triggers a specific response in cells with the appropriate receptor.

Auxin

Hormone involved in phototropism, gravitropism, apical dominance, cell elongation, root growth, fruit development, and adventitious roots.

Phototropism

Plant growth response to light; auxin accumulates on the shaded side of a shoot and stimulates elongation there.

Apical dominance

Auxin from the shoot tip inhibits lateral bud growth; removing/pinching the tip can stimulate branching.

Cytokinin

Hormone that promotes cell division and growth, often in interaction with auxin; delays senescence.

Gibberellin

Hormone that promotes shoot elongation, leaf growth, seed and bud germination, and release from dormancy.

Abscisic acid (ABA)

Stress/dormancy hormone; inhibits growth, promotes seed/bud dormancy, and closes stomata during drought.

Ethylene

Volatile gaseous hormone that promotes fruit ripening, flower wilting, and leaf abscission.

Abscission

Shedding of a leaf, flower, or fruit from a plant.

Senescence

Aging process in plant tissues.

Apical meristem

Growth region at root and shoot tips that increases length.

Lateral meristem

Growth tissue that increases thickness or girth.

Intercalary meristem

Meristem at monocot leaf bases or nodes that enables continued growth after cutting.

Dermal tissue

Outer protective tissue covering the plant.

Vascular tissue

Tissue that transports water, minerals, and sugars; includes xylem and phloem.

Ground tissue

Tissue involved in photosynthesis, storage, and support.

Parenchyma

Common living ground tissue with thin walls; photosynthesis, storage, and wound repair.

Collenchyma

Living support cells with unevenly thickened walls, often beneath epidermis.

Sclerenchyma

Support tissue usually dead at maturity, with thick lignin-strengthened secondary walls.

Node

Point on a stem where leaves, aerial roots, or flowers attach.

Internode

Stem region between two nodes.

Primary growth

Increase in length due to apical meristem activity.

Secondary growth

Increase in thickness/girth due to lateral meristem activity.

Taproot system

One main deep root with smaller lateral roots; common in dicots.

Fibrous root system

Dense, shallow network of roots; common in monocots and helps reduce soil erosion.

Root cap

Protective covering at the root tip.

Root zone of cell division

Region near root tip where meristem cells actively divide.

Root zone of elongation

Region where newly formed cells increase in length.

Root zone of maturation

Region where cells differentiate into specialized types.

Endodermis

Layer separating root ground tissue from the stele.

Casparian strip

Waxy region in endodermal cell walls that helps prevent unwanted materials from entering root vascular tissue.

Lamina

Leaf blade; broad, flat part of a leaf.

Petiole

Stalk connecting a leaf blade to the stem.

Midrib

Main central vein of a leaf.

Leaf margin

Edge of the leaf blade.

Monocot leaf venation

Usually parallel veins.

Dicot leaf venation

Usually branched or net-like veins.

Trichomes

Small plant hairs that can help deter herbivores.

Xylem

Mostly dead conducting tissue that transports water and dissolved minerals; also provides support.

Tracheids

Long, water-conducting xylem cells.

Vessel elements

Xylem conducting cells that join to form vessels.

Phloem

Living vascular tissue that transports sugars and other organic compounds.

Sieve-tube elements

Phloem cells that form tubes for sugar transport.

Companion cells

Living cells that support sieve-tube elements and help load sugars.

Passive transport

Movement across membranes without direct ATP use; includes diffusion and osmosis.

Osmosis

Net movement of water across a selectively permeable membrane toward higher solute concentration/lower water potential.

Active transport

Movement requiring energy and transport proteins, often against a concentration gradient.

Water potential

Potential energy of water that predicts the direction water will move; measured in MPa.

Solute potential (ΨS)

Osmotic component of water potential; negative when solutes are present and zero in distilled water.

Pressure potential (ΨP)

Pressure component of water potential; can be positive or negative.

Turgid cell

Water-filled plant cell whose membrane presses against the cell wall; firm and supportive.

Flaccid cell

Plant cell with reduced turgor; can contribute to wilting.

Plasmolyzed cell

Cell that has lost so much water that its membrane pulls away from the cell wall.

Transmembrane pathway

Movement that crosses cell membranes and walls using transport proteins.

Symplastic pathway

Movement through connected cytoplasm via plasmodesmata.

Apoplastic pathway

Movement through cell walls and intercellular spaces.

Bulk flow

Mass movement of fluid driven by pressure differences and/or gravity.

Cohesion

Attraction of water molecules to one another.

Adhesion

Attraction of water to other surfaces, including xylem walls.

Cohesion-tension theory

Water loss from leaves creates tension that pulls a cohesive column of water upward through xylem.

Transpiration functions

Moves water to leaves, helps cool leaves, supports transport, and affects the global water cycle and climate