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) and 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 selereids.
chromoplast=A plastid containing pigments other than chlorophyll, usually yellow and orange carotenoid pigments.
chloroplast=A plastid that contains chlorophylls; the site of photosynthesis. Chloroplasts occur in plants and algae.
leucoplast=A colorless plastid; leucoplasts are commonly centers of starch formation.
amyloplast=A leucoplast (colorless plastid) 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, or stroma: changes in the turgor of a pair of guard cells cause opening and closing of the pore.
stomata=A minute opening, bordered by guard cells, in the epidermis of leaves and stems through which gases pass; also used to refer to the entire stomatal apparatus: the guard cells plus their included pore.
collenchyma=A supporting tissue composed of collenchyma cells; common in regions of primary growth in stems and in 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 having many pits. Sclereids are variable in form but typically not very long; they may or may not be living at maturity.
cell lumen=(1) The space bounded by the plant cell wall; (2) the thylakoid space in chloroplasts; (3) the narrow, transparent space of endoplasmic reticulum.
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 of vascular plants; its walls may or may not be lignified; it may or may not have a living protoplast at maturity.
companion cell=A specialized parenchyma cell associated with a sieve-tube element in angiosperm phloem and arising from the same mother cell as the sieve-tube element.
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, with tapering ends and pitted walls without perforations, in contrast to a vessel element; 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 and with tapering end walls that lack sieve plates; found in the phloem of gymnosperms.
taproot=The primary root of a plant, formed in direct continuation with the root tip or radicle of the embryo; forms a stout, tapering main root from which arise smaller, lateral roots.
fibrous roots= Fibrous roots are 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. It typically consists of a central column of cells, the columella, and a lateral portion, the lateral rootcap, which surrounds the columella.
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; greatly increase the absorbing surface of the root.
primary root= The first root of the plant, developing as a continuation of the root tip or radicle of the embryo; the taproot.
Casparian strip= A bandlike region of primary wall containing suberin and lignin; found in anticlinal—radial and transverse—walls of endodermal and exodermal cells.
Endodermis= A single layer of cells forming a sheath around the vascular region in roots and some stems; endodermal cells are characterized by a Casparian strip within radial and transverse walls. In roots and stems of seed plants, the endodermis is the innermost layer of the cortex.
lateral root= A root that arises from another, older root. Also called a branch root or a secondary root, if the older root is the primary root.
mucigel=Mucigel is a slimy substance that covers the root tips of plants. It's a mixture of plant secretions, bacteria, and soil particles.
pericycle= A tissue characteristic of roots that is bounded externally by the endodermis and internally by the phloem.
prop root= Adventitious roots arising from the stem above soil level and helping to support the plant; common in many monocots, such as maize (Zea mays).
pneumatophores= Negatively gravitropic extensions of the root systems of some trees growing in swampy habitats; they grow upward and out of the water and probably function to ensure adequate aeration.
adventitious root= Adventitious roots are roots that grow from any part of a plant that isn't a root. They can form during normal development or in response to stress
aerial root= Aerial roots are roots that grow above the ground and are exposed to air. They are a natural part of a plant's growth and serve many purposes, including absorbing water, providing support, and helping plants climb.
storage root= A storage root is a modified underground organ that stores nutrients, such as water and carbohydrates, for a plant. Storage roots are important for food security and agriculture
pith= The ground tissue occupying the center of the stem or root within the vascular cylinder; usually consists of parenchyma.
root nodule= Root nodules are knob-like structures that form on the roots of leguminous plants. They are the result of a symbiotic relationship between the plant and nitrogen-fixing bacteria.
fascicular cambium= The vascular cambium originating within a vascular bundle, or fascicle.
interfascicular cambium= The vascular cambium arising between the fascicles, or vascular bundles, from interfascicular parenchyma.
interfascicular region= Tissue region between vascular bundles in a stem. Also called a pith ray.
leaf trace gap= In seed plants, region of parenchyma tissue in the primary vascular cylinder of a stem above the point of departure of the leaf trace or traces.
leaf trace= That 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 cells, or both.