Campbell Unit 6: Plant Form and Function

Cell

The fundamental unit of life.

Tissue

A group of cells consisting of one or more cell types that perform a specialized function together.

Organ

Several types of tissues that carry out a specialized function together.

Root

An organ that anchors a vascular plant in soil.

Taproot

The main vertical root which develops from the primary root in taproot systems.

Stem

A plant organ bearing leaves and buds to elongate and orient the shoot in a way to optimize photosynthesis.

Leaf

The main photosynthetic organ of a plant.

Dermal Tissue

The outer protective covering of the plant, like skin.

Vascular Tissue

Tissue that facilitates transport of materials through the plant and provides mechanical support.

Ground Tissue

Tissue that is not dermal or vascular.

Parenchyma Cells

Cells with thin and flexible primary walls that lack secondary walls.

Collenchyma Cells

Cells that support young parts of a plant shoot.

Sclerenchyma Cells

Cells that are more rigid than collenchyma cells and have a secondary cell wall containing lots of lignin.

Xylem

Tissue that conducts water and dissolved minerals upward from roots into shoots.

Phloem

Tissue that transports sugars from where they're made to where they're needed or stored.

Meristems

Undifferentiated tissues that let plants keep growing and lead to new cells that elongate and become differentiated.

Apical Meristems

Meristems located at root and shoot tips that provide cells for primary growth.

Secondary Growth

Growth in thickness, made possible by lateral meristems.

Root Cap

Protects the delicate apical meristem as the root pushes through the soil.

Zone of Cell Division

Stem cells of the root apical meristem and their immediate products.

Zone of Elongation

The region where most of the growth occurs as root cells elongate.

Zone of Differentiation/Maturation

The region where cells complete differentiation and become distinct cell types.

Apical Dominance

The closer an axillary bud is to an active bud, the more inhibited it is.

Stomata

Openings on the leaf surface that allow for gas exchange.

Mesophyll

The leaf's ground tissue, sandwiched between the upper and lower epidermal layers.

Vascular Cambium

A meristematic cylinder that produces secondary xylem and secondary phloem during secondary growth.

Bark

All tissues external to the vascular cambium.

Development

A specific series of changes by cells that form tissues, organs, and organisms.

Growth

An irreversible increase in size.

Cell Differentiation

The process by which cells with the same genes become different from each other.

Transpiration

The loss of water vapor from leaves and other aerial parts of the plant.

Xylem Sap

Water and dissolved minerals in the xylem.

Water Potential

A quantity that includes the effects of solute concentration and physical pressure, predicting the direction water will flow in.

Osmosis

The diffusion of free water.

Plasmolysis

The shrinking of a cell and pulling away from the cell wall.

Turgid

A walled cell with a greater solute concentration than its surroundings.

Wilting

The loss of turgor in cells, causing the plant to droop.

Bulk Flow

The movement of liquid in response to a pressure gradient.

Stomata

Openings on the leaf surface that regulate the rate of transpiration.

Translocation

The transport of products of photosynthesis, carried out by the phloem.

Plasmodesmata

Channels that can change in permeability and number, allowing for symplastic transport of macromolecules.

Symplastic transport

Movement of proteins, RNAs, and other macromolecules through plasmodesmata over long distances.

Phloem

Conducts electrical signals that help integrate whole plant function.

Humus

Remains of dead organisms and other organic matter in soil.

Topsoil

Upper layer of soil mostly composed of humus.

Soil Horizons

Layers of soil.

Loams

Fertile topsoils composed of equal amounts of sand, silt, and clay.

Cation Exchange

Process in which cations are displaced from soil particles by other cations, particularly H+.

Fertilization

Addition of mineral nutrients to the soil to make it a renewable resource.

Sustainable Agriculture

Farming practices that are conservation-minded, environmentally safe, and profitable.

No Till Agriculture

Plowing technique that creates narrow furrows for seeds and fertilizer.

Phytoremediation

Nondestructive biotechnology that uses plants to extract soil pollutants for safe disposal.

Essential Element

Chemical element required for a plant to complete its life cycle and reproduce.

Hydroponic Culture

Growing plants in mineral solutions instead of soil.

Macronutrients

Essential elements required by plants in large amounts.

Micronutrients

Essential elements needed by plants in tiny quantities.

Rhizobacteria

Bacteria that live in close association with plant roots or in the rhizosphere.

Rhizosphere

Soil closely surrounding plant roots.

Endophytes

Rhizobacteria that live between cells within plants.

Nitrogen Cycle

Series of natural processes that make nitrogen available to living things.

Nitrogen Fixation

Process of converting atmospheric nitrogen to ammonia for use by plants.

Nodules

Swellings along legume roots that contain Rhizobium bacteria.

Bacteroids

Form taken by Rhizobium bacteria within nodules.

Crop Rotation

Planting different crops in succession to restore nitrogen concentration in the soil.

Ectomycorrhizae

Fungal associations that form a dense sheath of mycelia over the surface of plant roots.

Arbuscular Mycorrhizae

Fungal associations that are embedded within plant roots.

Flower

Sporophytic structure for sexual reproduction in angiosperms.

Receptacle

Part of the stem attached to all floral organs.

Carpels

Female reproductive organs in flowers.

Stamens

Male reproductive organs in flowers.

Petals

Modified leaves that attract pollinators.

Sepals

Outermost whorl of floral organs that protect the flower bud.

Ovules

Structures within the ovary that become seeds if fertilized.

Pistil

One or more fused carpels in a flower.

Stamen

Male reproductive organ in a flower, consisting of a filament and anther.

Complete Flowers

Flowers that have all the basic floral organs.

Incomplete Flowers

Flowers that lack one or more floral organs.

Inflorescences

Clusters of flowers.

Pollination

Transfer of pollen to the ovule-bearing structure of a seed plant.

Abiotic Pollination

Pollination by wind.

Biotic Pollination

Pollination by insects, birds, or other animals.

Embryo Sac

Female gametophyte that develops in each ovule.

Pollen Grain

Male gametophyte that contains the generative cell, tube cell, and spore wall.

Pollen Tube

Long cellular protuberance that delivers sperm to the female gametophyte.

Fertilization

Fusion of gametes to form a zygote and endosperm.

Endosperm

Multicellular, food-storing tissue of the seed.

Double Fertilization

Union of two sperm cells with different nuclei of the female gametophyte.

Seed

Mature ovule containing an embryo surrounded by stored food and protective layers.

Hypocotyl

Embryonic axis that terminates in the radicle.

Epicotyl

Portion of the embryonic axis above the cotyledons.

Cotyledons

Seed leaves.

Imbibition

Uptake of water by a dry seed, initiating seed germination.

Fruit

Mature ovary of a flower.

Simple Fruit

Fruit derived from a single carpel or several fused carpels.

Aggregate Fruit

Fruit derived from a flower with more

Action Spectrum

Depicts relative effectiveness of different wavelengths of radiation in driving a particular process

Blue Light Photoreceptors

Initiate a variety of responses in plants, such as the light-induced opening of the stomata and the light-induced slowing of hypocotyl elongation

Phytochromes

Pigments that absorb mostly red and far-red light, regulating plant responses to light

Circadian Rhythms

Control many plant processes

Photoperiodism

Physiological response to specific night or day lengths