So far for week 3

Epidermis

Outermost layer of cells of the leaf and young stems and roots; primary in origin.

Cortex

(1) Ground tissue region of stem/root, bounded externally by the epidermis and internally by the vascular system; primary-tissue region (2) Peripheral region of a cell protoplast.

Vascular Bundle

A strand of tissue containing primary xylem and primary phloem (procambium if present too) frequently enclosed by a bundle sheath of parenchyma/fibers.

Meristem

Embryonic tissue regions, primarily concerned with new cell formation.

Cotyledon

Seed leaf; generally absorbs food in monocotyledons and stores food in angiosperm.

Epicotyl

Upper portion of the axis of an embryo or seedling, above the point of insertion of the cotyledons and below the next leaves.

Hypocotyl

Portion of an embryo or seedling situated between the point of attachment of the cotyledons and the radicle.

Xylem

A complex vascular tissue through which most of the water and minerals of a plant are conducted; characterized by the presence of tracheary elements.

Phloem

The food-conducting tissue of vascular plants; composed of sieve elements, various kinds of parenchyma cells, fibers, and sclereids.

Chromoplast

A plastid containing pigments other than chlorophyll, usually yellow and orange carotenoid pigments.

Chloroplast

A plastid that contains chlorophylls; the site of photosynthesis.

Leucoplast

A colorless plastid; commonly centers of starch formation.

Amyloplast

A leucoplast that forms starch grains.

Druse

A compound, more or less spherical crystal with many component crystals projecting from its surface; composed of calcium oxalate.

Raphide

Fine, sharp, needlelike crystals of calcium oxalate found in the vacuoles of many plant cells.

Trichome

An outgrowth of the epidermis, such as hair, scale, or water vesicle.

Guard cells

Pairs of specialized epidermal cells surrounding a pore; changes in turgor cause opening and closing of the pore.

Stomata

A minute opening in the epidermis of leaves and stems through which gases pass; bordered by guard cells.

Collenchyma

A supporting tissue composed of collenchyma cells; common in regions of primary growth in stems and some leaves.

Parenchyma

A tissue composed of parenchyma cells.

Sclerenchyma

A supporting tissue composed of sclerenchyma cells, including fibers and sclereids.

Sclereid

A sclerenchyma cell with a thick, lignified secondary wall; variable in form but typically not very long.

Cell lumen

The space bounded by the plant cell wall; includes thylakoid space in chloroplasts.

Cell wall pit

A recessed cavity in a cell wall where a secondary wall does not form.

Fiber

An elongated, tapering, generally thick-walled sclerenchyma cell; may or may not be lignified.

Companion cell

A specialized parenchyma cell associated with a sieve-tube element in angiosperm phloem.

Perforation plate

Part of the wall of a vessel element that is perforated.

Sieve plate

The part of the wall of sieve-tube elements that bears one or more highly differentiated sieve areas.

Tracheid

An elongated, thick-walled conducting and supporting cell of xylem; found in nearly all vascular plants.

Sieve tube

A series of sieve-tube elements arranged end to end and interconnected by sieve plates.

Sieve cell

A long, slender sieve element with relatively unspecialized sieve areas.

Taproot

The primary root of a plant, formed in direct continuation with the root tip of the embryo.

Fibrous roots

Thin, branching roots that grow from a plant's stem; opposite of taproots.

Rootcap

A thimblelike mass of cells that covers and protects the growing tip of a root.

Apical meristem

The meristem at the tip of the root or shoot in a vascular plant.

Root hairs

Tubular outgrowths of epidermal cells of the root; increase the absorbing surface of the root.

Primary root

The first root of the plant, developing as a continuation of the root tip.

Casparian strip

A bandlike region of primary wall containing suberin and lignin; found in endodermal and exodermal cells.

Endodermis

A single layer of cells forming a sheath around the vascular region in roots.

Lateral root

A root that arises from another, older root; also called a branch root.

Mucigel

A slimy substance that covers the root tips of plants; a mix of plant secretions and soil particles.

Pericycle

A tissue characteristic of roots bounded externally by the endodermis and internally by the phloem.

Prop root

Adventitious roots arising from the stem above soil level, helping to support the plant.

Pneumatophores

Extensions of root systems of some trees growing in swampy habitats; they grow upward for aeration.

Adventitious root

Roots that grow from any part of a plant that isn't a root; can form during normal development or in response to stress.

Aerial root

Roots that grow above the ground and are exposed to air, serving various purposes.

Storage root

A modified underground organ that stores nutrients, such as water and carbohydrates.

Pith

The ground tissue occupying the center of the stem or root within the vascular cylinder.

Root nodule

Knob-like structures that form on the roots of leguminous plants due to a symbiotic relationship.

Fascicular cambium

The vascular cambium originating within a vascular bundle.

Interfascicular cambium

The vascular cambium arising between the fascicles from interfascicular parenchyma.

Interfascicular region

Tissue region between vascular bundles in a stem; also called a pith ray.

Leaf trace gap

Region of parenchyma tissue in the primary vascular cylinder of a stem above the point of departure of the leaf trace.

Leaf trace

Part of a vascular bundle extending from the base of the leaf to its connection with a vascular bundle in the stem.

Bundle sheath

Layer or layers of cells surrounding a vascular bundle; may consist of parenchyma or sclerenchyma.