BIO Unit 3: Plants

Angiosperms

Flowering plants characterized by flowers; all fruits develop from flowers.

Cotyledons

Seed leaves that perform initial photosynthesis during early plant growth.

Monocots

Angiosperms with one cotyledon; differ from dicots in leaf venation, vascular arrangement, flower parts, and roots.

Dicots

Angiosperms with two cotyledons; differ from monocots in leaf venation, vascular arrangement, flower parts, and roots.

Secondary cell wall

Rigid additional cell wall found in some plant cells.

Plasmodesmata

Channels connecting the cytoplasm of adjacent plant cells.

Central vacuole

Large compartment in plant cells that stores materials and helps maintain pressure.

Sepals

Flower structures that enclose and protect the flower bud.

Petals

Colorful and fragrant flower structures that attract pollinators.

Stamen

Male reproductive structure of a flower consisting of a filament and anther.

Filament

Stalk of the stamen that supports the anther.

Anther

Structure containing sacs where pollen is produced.

Carpel

Female reproductive structure containing the stigma, style, and ovary.

Stigma

Sticky tip of the carpel that receives pollen.

Style

Long, slender structure connecting the stigma to the ovary.

Ovary

Flower structure containing ovules; develops into the fruit after fertilization.

Ovule

Structure inside the ovary containing the developing egg and supporting cells; develops into a seed after fertilization.

Self-fertilization

Fertilization involving reproductive cells from the same plant.

Cross-fertilization

Fertilization involving reproductive cells from different plants.

Pollen tube

Tube produced by the pollen grain that grows down the style toward the ovule.

Double fertilization

Process in which one sperm fertilizes the egg to form a diploid zygote, while another fuses with the polar nuclei to form endosperm.

Zygote

Diploid cell formed when a sperm fertilizes the egg; develops into the embryo.

Endosperm

Food-storage tissue formed during double fertilization that nourishes the developing embryo.

Seed

Structure developed from a fertilized ovule that contains an embryo, stored food, and a protective seed coat.

Seed coat

Hard, protective outer covering of a mature seed.

Embryo

Developing young plant inside the seed.

Fruit

Mature ovary that houses and protects seeds and helps disperse them.

Germination

Process in which a seed begins growing under suitable temperature and moisture conditions.

Shoot system

Aboveground plant system containing stems and leaves; absorbs light and CO2 and transports water.

Root system

Plant system that anchors the plant and absorbs water and nutrients from the soil.

Meristems

Regions of undifferentiated plant stem cells that continuously divide to produce new cells and tissues.

Apical meristems

Meristematic tissues located at the tips of roots and stems that control primary growth.

Dermal tissue

Outer protective covering of the plant; also called epidermal tissue.

Ground tissue

Plant tissue responsible for photosynthesis, carbohydrate storage, and structural support.

Vascular tissue

Plant tissue responsible for transporting water, nutrients, and sugars and providing support.

Epidermis

Outermost layer of plant cells that protects shoots and absorbs water and nutrients in roots.

Cuticle

Waxy layer covering leaves and stems that reduces water loss and protects against pathogens.

Stomata

Pores that allow CO2 to enter and O2 to exit photosynthetically active tissues.

Root hairs

Extensions of root epidermal cells that increase surface area for water uptake.

Trichomes

Hair-like structures that can function in defense or secretion.

Parenchyma

Ground tissue cells containing chloroplasts or starch granules; function in photosynthesis and storage.

Collenchyma

Ground tissue cells that provide flexible structural support to actively growing plant parts.

Sclerenchyma

Ground tissue containing tough, rigid lignin and cellulose that provides structural support.

Xylem

Vascular tissue that transports water and dissolved minerals from roots to shoots; cells are dead at maturity and have thick walls.

Phloem

Vascular tissue that transports sugars, amino acids, hormones, and other substances throughout the plant; cells remain alive at maturity.

Tracheids

Water-conducting xylem cells with pits that allow water movement.

Vessel elements

Xylem cells found in angiosperms that have perforations for water transport and form tubes.

Sieve-tube elements

Long, thin phloem cells with perforated ends called sieve plates.

Sieve plates

Perforated end walls connecting sieve-tube elements.

Companion cells

Phloem cells that maintain the cytoplasm and plasma membrane of sieve-tube elements.

Taproot

A main central root with smaller branching roots.

Fibrous roots

Root system consisting of many smaller roots rather than one dominant central root.

Adventitious roots

Roots that develop from the shoot system rather than from existing roots.

Prop roots

Adventitious roots that brace and support plants such as corn.

Pneumatophores

Specialized lateral roots that allow oxygen from the atmosphere to diffuse into the root system.

Storage roots

Thickened roots that store carbohydrates; examples include carrots and beets.

Stem

Aboveground shoot structure that supports leaves and contains nodes and internodes.

Node

Location on a stem where leaves attach.

Internode

Segment of a stem between two nodes.

Herbaceous stems

Stems that undergo primary vertical growth without forming bark.

Woody stems

Stems that undergo both primary and secondary growth, forming bark.

Primary growth

Vertical growth of roots and shoots controlled by apical meristems.

Secondary growth

Increase in the thickness or diameter of stems and roots controlled by lateral meristems.

Lateral meristems

Meristematic tissues responsible for secondary growth and increasing plant diameter.

Cambium

Cylinder of dividing cells that increases the width of roots, trunks, and branches.

Vascular cambium

Lateral meristem located between secondary xylem and secondary phloem.

Cork cambium

Lateral meristem near the outer perimeter of roots and stems that produces cork cells.

Secondary xylem

Wood produced by vascular cambium toward the interior of the stem.

Secondary phloem

Inner bark produced by vascular cambium toward the exterior of the stem.

Cork cells

Cells produced by cork cambium that form the protective outer bark.

Pericycle

Ring of actively dividing cells surrounding the root's vascular tissue; initiates lateral roots and helps with secondary growth.

Lateral roots

Branch roots initiated by the pericycle that grow through the cortex.

Stolons (runners)

Slender horizontal stems growing along the soil surface that produce new plantlets; example: strawberries.

Rhizomes

Horizontal underground stems that grow below the soil surface and produce roots and shoots; example: ginger.

Tubers

Swollen underground stem structures specialized for starch storage with nodes called eyes; example: potatoes.

Corms

Short, swollen, vertical underground stems that store food as solid tissue; examples: crocus and gladiolus.

Bulbs

Short underground vertical stems surrounded by thick, fleshy nutrient-storing leaves; examples: onions and garlic.

Thorns

Hard, sharp modified stems or branches that deter herbivores.

Leaf blade

Expanded, broad portion of a simple leaf that absorbs light.

Petiole

Stalk connecting the leaf blade to the shoot system.

Modified leaves

Leaves adapted for specialized functions such as storage, climbing, attraction, trapping insects, or protection.

Essential elements

Chemical elements required by plants for survival and metabolism; often function as enzyme cofactors.

Macronutrients

Nutrients required in amounts of at least 1 gram per kilogram of plant dry mass.

Micronutrients

Trace elements required in amounts of 0.1 gram or less per kilogram of plant dry mass.

Major macronutrients

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

Potassium (K+)

Macronutrient that works with enzymes and serves as the main solute for osmotic regulation, including stomatal opening and closing.

Calcium (Ca2+)

Macronutrient that maintains cell membrane structure, functions in cell walls, and helps regulate selective permeability.

Magnesium (Mg2+)

Macronutrient that is an essential component of chlorophyll.

Micronutrients

Chlorine, iron, manganese, boron, zinc, copper, nickel, and molybdenum; mainly function as enzyme cofactors.

Carbon source for plants

Most plant dry mass originates from atmospheric CO2 absorbed during photosynthesis.

Rubisco

Calvin cycle enzyme that becomes saturated with CO2, limiting further increases in photosynthetic rate.

Importance of water

Water provides hydrogen and some oxygen for organic compounds, dissolves mineral nutrients, transports substances, and maintains cell pressure.

Plant water content

Water typically makes up about 90% of the weight of living plants.

Soil

Provides plants with water and essential nutrients; fertility describes its ability to support plant growth.

Nitrogen fixation

Process that combines atmospheric nitrogen (N2) with hydrogen to produce ammonia (NH3).

Nitrogenase

Enzyme used by specialized bacteria to convert atmospheric nitrogen into biologically available compounds.

Rhizobium

Nitrogen-fixing bacteria that live in association with legume roots.

Legumes

Plants such as soybeans, peas, beans, peanuts, clover, and alfalfa that form symbiotic relationships with nitrogen-fixing rhizobia.

Root nodules

Lumpy structures on legume roots where rhizobia live and fix nitrogen.

Nod factors

Chemical signals produced by rhizobia that are recognized by their preferred host plants and help initiate nodule formation.