Chapter 35: Vascular Plant Structure, Growth, and Development

Vocabulary from Campbell's Biology

Root

An organ in vascular plants that anchors the plant and enables it to absorb water and minerals from the soil.

Root System

All of a plant's roots, which anchor it in the soil, absorb and transport minerals and water, and store food.

Shoot System

The aerial portion of a plant body, consisting of stems, leaves, and (in angiosperms) flowers.

Lateral Roots

A root that arises from the pericycle of an established root.

Taproot

A main vertical root that develops from an embryonic root and gives rise to lateral (branch) roots.

Root Hairs

A tiny extension of a root epidermal cell, growing just behind the root tip and increasing surface area for absorption of water and minerals.

Stem

A vascular plant organ consisting of an alternating system of nodes and internodes that support the leaves and reproductive structures.

Nodes

A point along the stem of a plant at which leaves are attached.

Internodes

A segment of a plant stem between the points where leaves are attached.

Apical Bud

A bud at the tip of a plant stem; also called a terminal bud.

Axillary Bud

A structure that has the potential to form a lateral shoot, or branch. The bud appears in the angle formed between a leaf and a stem.

Leaf

The main photosynthetic organ of vascular plants.

Blade

(1) A leaflike structure of a seaweed that provides most of the surface area for photosynthesis. (2) The flattened portion of a typical leaf.

Petiole

The stalk of a leaf, which joins the leaf to a node of the stem.

Veins

A vascular bundle in a leaf.

Dermal Tissue

The outer protective covering of plants.

Epidermis

The dermal tissue of nonwoody plants, usually consisting of a single layer of tightly packed cells.

Cuticle

A waxy epidermal coating on leaves and most stems that helps prevent water loss.

Periderm

The protective coat that replaces the epidermis in woody plants during secondary growth, formed of the cork and cork cambium.

Guard Cells

The two cells that flank the stomatal pore and regulate the opening and closing of the pore.

Trichomes

An epidermal cell that is a highly specialized, often hairlike outgrowth on a plant shoot.

Vascular Tissue

Plant tissue consisting of cells joined into tubes that transport water and nutrients throughout the plant body.

Xylem

Vascular plant tissue consisting mainly of tubular dead cells that conduct most of the water and minerals upward from the roots to the rest of the plant.

Phloem

Vascular plant tissue consisting of living cells arranged into elongated tubes that transport sugar and other organic nutrients throughout the plant.

Stele

The vascular tissue of a stem or root.

Ground Tissue

Plant tissue that is neither vascular nor dermal, fulfilling a variety of functions, such as storage, photosynthesis, and support.

Pith

Ground tissue that is internal to the vascular tissue in a stem; in many monocot roots, parenchyma cells that form the central core of the vascular cylinder.

Cortex

Ground tissue that is between the vascular tissue and the dermal tissue in a root or eudicot stem.

Parenchyma Cells

A relatively unspecialized plant cell type that carries out most of the metabolism, synthesizes and stores organic products, and develops into a more differentiated cell type.

Collenchyma Cells

A flexible plant cell type that occurs in strands or cylinders that support young parts of the plant without restraining growth.

Sclerenchyma Cells

A rigid, supportive plant cell type usually lacking a protoplast and possessing thick secondary walls strengthened by lignin at maturity.

Lignin

A strong polymer embedded in the cellulose matrix of the secondary cell walls of vascular plants that provides structural support in terrestrial species.

Tracheids

A long, tapered water-conducting cell found in the xylem of nearly all vascular plants. Functioning types of these cells are no longer living.

Vessel Elements

A short, wide, water-conducting cell found in the xylem of most angiosperms and a few nonflowering vascular plants. Dead at maturity, these cells are aligned end to end to form micropipes called vessels.

Vessels

A continuous water-conducting micropipe found in most angiosperms and a few nonflowering vascular plants.

Sieve-Tube Elements

A living cell that conducts sugars and other organic nutrients in the phloem of angiosperms; also called a sieve-tube member. Connected end to end, they form sieve tubes.

Sieve Plates

An end wall in a sieve-tube element, which facilitates the flow of phloem sap in angiosperm sieve tubes.

Companion Cell

A type of plant cell that is connected to a sieve-tube element by many plasmodesmata and whose nucleus and ribosomes may serve one or more adjacent sieve-tube elements.

Indeterminate Growth

A type of growth characteristic of plants, in which the organism continues to grow as long as it lives.

Meristems

Plant tissue that remains embryonic as long as the plant lives, allowing for indeterminate growth.

Determinate Growth

A type of growth characteristic of most animals and some plant organs, in which growth stops after a certain size is reached.

Apical Meristems

A localized region at a growing tip of a plant body where one or more cells divide repeatedly. The dividing cells of this region enable the plant to grow in length.

Primary Growth

Growth produced by apical meristems, lengthening stems and roots.

Secondary Growth

Growth produced by lateral meristems, thickening the roots and shoots of woody plants.

Lateral Meristems

A meristem that thickens the roots and shoots of woody plants. The vascular cambium and cork cambium are examples of these.

Vascular Cambium

A cylinder of meristematic tissue in woody plants that adds layers of secondary vascular tissue called secondary xylem (wood) and secondary phloem.

Cork Cambium

A cylinder of meristematic tissue in woody plants that replaces the epidermis with thicker, tougher cork cells.

Primary Meristems

The three meristematic derivatives (protoderm, procambium, and ground meristem) of an apical meristem.

Root Cap

A cone of cells at the tip of a plant root that protects the apical meristem.

Endodermis

In plant roots, the innermost layer of the cortex that surrounds the vascular cylinder.

Pericycle

The outermost layer in the vascular cylinder, from which lateral roots arise.

Apical Dominance

Tendency for growth to be concentrated at the tip of a plant shoot because the apical bud partially inhibits axillary bud growth.

Leaf Primordia

A finger-like projection along the flank of a shoot apical meristem, from which a leaf arises.

Stomata

A microscopic pore surrounded by guard cells in the epidermis of leaves and stems that allows gas exchange between the environment and the interior of the plant.

Mesophyll

Leaf cells specialized for photosynthesis. In C3 and CAM plants, these cells are located between the upper and lower epidermis; in C4 plants, they are located between the bundle-sheath cells and the epidermis.

Bark

All tissues external to the vascular cambium, consisting mainly of the secondary phloem and layers of periderm.

Lenticels

A small raised area in the bark of stems and roots that enables gas exchange between living cells and the outside air.

ABC Hypothesis

A model of flower formation identifying three classes of organ identity genes that direct formation of the four types of floral organs.