Bio 106 Fall 2026 Exam 2 Vocabulary Flashcards

Vocabulary key terms and definitions based on the Bio 106 Fall 2026 Exam 2 study guide covering plant nutrition, transport, tissue growth, hormones, responses to stimuli, and reproductive anatomy.

Humus

The dark organic matter layer in soil formed by decomposing plant and animal material, critical for plant growth and soil fertility.

Cation Exchange

A soil nutrient dynamic where plant roots release hydrogen ions ($H^+$) to displace positively charged nutrient ions bound to soil particles, making them available for plant absorption.

Leaching

The loss of water-soluble soil nutrients (especially negatively charged anions) as water drains through soil, reducing nutrient availability for plants.

Ectomycorrhiza

A type of mycorrhizal fungus that forms a dense sheath over the root surface and grows in extracellular spaces between root cells without penetrating cell walls.

Endomycorrhiza

A type of mycorrhizal fungus that extends hyphae through root cell walls to form specialized structures within root cortex cells.

Casparian Strip

A waxy belt in the root endodermis that blocks apoplastic transport, forcing water and solutes to cross a plasma membrane into the symplast before reaching the xylem.

Transpiration

The evaporation of water from stomata on leaf surfaces, creating negative pressure that pulls water upward through the xylem.

Root Pressure

Positive pressure generated in root xylem by the active accumulation of minerals and osmotic water movement, driving sap upward.

Guard Cells

Specialized epidermal cells surrounding each stoma that swell or shrink to regulate stomatal opening, gas exchange, and transpiration.

Sugar Source

A plant organ, such as a mature leaf, that produces sugar via photosynthesis or starch breakdown in excess of its own consumption.

Sugar Sink

A plant organ, such as a growing root, bud, fruit, or storage tuber, that consumes or stores sugars.

Vascular Tissue

Plant tissue responsible for internal transport, consisting of xylem for water/minerals and phloem for sugars.

Ground Tissue

Plant tissue situated between dermal and vascular tissues that functions in storage, photosynthesis, and structural support.

Primary Growth

Growth produced by apical meristems that extends the length of plant stems and roots.

Secondary Growth

Growth produced by lateral meristems (vascular and cork cambium) that increases the diameter and girth of woody stems and roots.

Meristem

Regions of undifferentiated plant tissue containing stem cells (initials) capable of perpetual cell division and giving rise to specialized tissues.

Cambium

A cylinder of lateral meristematic tissue (vascular or cork cambium) responsible for secondary growth in stems and roots.

Auxin

A plant hormone that promotes cell elongation, apical dominance, phototropism, and root development.

Phototropism

The directional growth of a plant organ in response to light, mediated by asymmetric distribution of auxin.

Blue-Light Receptors

Photoreceptors in plants that absorb blue wavelengths to mediate phototropism, stomatal opening, and hypocotyl elongation inhibition.

Phytochromes

Photoreceptors that toggle between red and far-red light-absorbing forms, regulating seed germination, shade avoidance, and stem elongation.

Triple Response

A growth maneuver in germinating seedlings triggered by mechanical stress, characterized by slowed stem elongation, stem thickening, and horizontal growth.

Gravitropism

A directional plant growth response to gravity, exhibiting positive gravitropism in roots (downward) and negative gravitropism in stems (upward).

Heat-Shock Protein

A protective protein synthesized by plants under extreme heat stress to prevent other cellular proteins from denaturing.

Microspore

A spore produced in anther sporangia that develops into a male gametophyte (pollen grain).

Megaspore

A spore produced in the ovule that develops into a female gametophyte (embryo sac).

Double Fertilization

An angiosperm reproduction process where one sperm fertilizes the egg cell to form a diploid zygote, while a second sperm fuses with two central nuclei to form a triploid endosperm.

Endosperm

A triploid, nutrient-rich tissue formed during double fertilization that feeds the developing plant embryo inside the seed.

Cotyledons

Embryonic seed leaves (one in monocots, two in eudicots) that store or absorb nutrients during germination.

Simple Fruit

A fruit that develops from a single carpel or single ovary of a single flower.

Aggregate Fruit

A fruit that develops from a single flower with multiple separate carpels.

Multiple Fruit

A fruit that develops from an inflorescence, where many flowers grow closely packed together.

Pome

A specific type of fruit (such as an apple) where the core is derived from an inferior ovary and surrounded by enlarged floral accessory tissue.