CH28

Petiole

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

Leaf Primordia

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

Tissue

An integrated group of cells with a common structure, function, or both.

Lenticel

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

Lignin

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

Dermal Tissue

The outer protective covering of plants

Blade

A leaflike structure of a seaweed that provides most of the surface area for photosynthesis; the flattened portion of a typical leaf

Apical Dominance

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

Mesophyll

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

Secondary Growth

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

Vessel elements

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

Phloem

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

Endodermis

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

Node

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

Taproot

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

Root

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

Cork Cambium

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

Root System

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

Pericycle

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

Vascular Cambium

A cylinder of meristematic tissue in woody plants that adds layers of secondary xylem and phloem.

Xylem

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

Pith

Ground tissue that’s mostly internal to vascular tissue; in many monocot roots, parenchyma cells that form the central core of the vascular cylinder.

Meristem

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

Primary Growth

Growth produced by apical meristems, lengthening stems and roots.

Determinate Growth

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

Cuticle

Waxy covering on the surface of stems and leaves that prevents desiccation in terrestrial plants

Lateral Meristem

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

Apical Bud

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

Tracheids

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

Primary Meristems

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

Stem

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

Apical Meristem

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

Organ

A specialized center of body function composed of several different types of tissues

Bark

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

Sieve Plates

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

Cortex

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

Sieve-Tube elements

A living cell that conducts sugars and other organic nutrients in the phloem of angiosperms; connected end to end they form sieve tubes

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.

Vascular Tissue

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

Internode

A segment of a plant stem between the points where leaves are attached (in between nodes)

Periderm

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

Indeterminate Growth

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

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.

Leaf

The main photosynthetic organ of vascular plants

Root Cap

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

Ground Tissue

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

Lateral Root

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

Companion Cell

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

Guard Cells

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

Root Hair

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

Vein

A vascular bundle in a leaf

Shoot System

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

Epidermis

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