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Glossary
Abaxial: Directed away from the axis.
Adaxial: Directed towards the axis.
Angiosperms: A plant taxon the seed of which is borne within
a matured ovary (fruit).
Anticlinal: Commonly refers to orientation of cell wall or plane
of cell division, perpendicular to the nearest surface.
Apical meristem: A group of meristematic cells at the apex of
root or shoot that by cell division produce the precursors
of the primary tissues of root or shoot.
Axial parenchyma: Parenchyma cells in the axial system of
Collenchyma: A cell type that is live at maturity, has unevenly
thickened, pectic-rich, primary cell walls, and functions
in structural support, often found at the periphery of
stems or leaves.
Cork (phellem): Tissue, dead at maturity generated from a cork
cambium. The cell walls of the tissue are impregnated
with suberin. This waterproofs the tissue. The cork
used to seal wine bottles is cork tissue harvested from
a species of oak.
Cork Cambium: A cambial layer that functions to produce cork,
and in some cases, phelloderm. In roots is derived
secondary vascular tissues.
Axial system: All secondary vascular cells derived from the
fusiform cambial initials and oriented with their longest
diameter parallel with the main axis of stem or root.
Bark: A non-technical term applied to all tissues outside the
vascular cambium or the xylem.
Cambium: A lateral meristem constituting a sheet of cells.
Growth of these cells increases the girdth of the plant
organ involved.
Casparian strip: A band or ring of mostly suberin that infiltrates
the cell wall of endodermal cells, functioning to force
water and mineral solutes to pass through the plasma
membrane of these cells.
Cellulose: A polymer of glucose sugar units in which the glucose
molecules are chemically bonded in the beta-1,4 position
a major component of the cell wall of green plants.
Chloroplast: A double membrane-bound organelle with internal
thylakoid membranes (lamellae and grana in the green
plants), functioning in the reactions of photosynthesis.
initially from pericyle while as in stems, it is derived
from the cortex. Unlike the vascular cambium these
cambial layers do not persist for the duration of the life
of the plant organ. Over time one cork cambium will
be supplanted by another generated from parenchyma
cells further inside.
Cortex: The primary ground tissue region between the vascular
system and the epidermis in stem and root.
Cuticle: A protective layer, containing cutin, that is secreted to
the outside of epidermal cells and functions to inhibit
water loss; found in all land plants.
Cytoplasm: Everything inside the plasma membrane but not
including the nucleus.
Endoplasmic reticulum: A cellular organelle consisting of
interconnected phospholipid membranes that may
function in material transport and as the site of protein
synthesis.
Epidermis: The outermost cell layer of all land plant organs,
functioning to provide mechanical protection of inner
tissue and to inhibit water loss.
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Lenticel: A pore in the bark, generally functioning in gas
exchange. (twig part).
Lignin: A complex polymer of phenolic compounds that
impregnates the secondary cell wall of some cells
(including tracheary elements and sclerenchyma),
functioning to impart strength and rigidity to the wall.
Parenchyma: Cells that, at maturity, are alive and potentially
capable of cell division, are isodiametric to elongate
in shape, and have a primary cell wall only (rarely
with secondary wall), forming a solid mass of tissue
and functioning in metabolic activities and in wound
healing and regeneration.
Periclinal: Commonly refers to orientation of cell wall or plane
of cell division; parallel with the circumference or the
nearest surface of an organ.
Pericycle: A cylindrical sheath of parenchyma cells just inside
the endodermis, functioning as the site of resumed
meristematic growth, forming a secondary root or (in
woody plants) contributing to the vascular cambium.
Periderm: A structure that consists of a cork cambium
(phellogen), with cork tissue (phellem) to the outside,
and in some cases a layer of cells derived from and to
the inside of the cork cambium called phelloderm.
Periderm: The cork cambium and its derivatives.
Phelloderm: In some periderms, a layer of living secondary
tissue is generated by the cork cambium to the inside.
Phloem: The principal food-conducting tissue of the vascular
plant composed mainly of sieve elements, various
kinds of parenchyma cells, fibers and sclereids.
Pit: A hole in a secondary cell wall that functions in cell-tocell communication during development and that
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may function in water conduction in some tracheary
elements.
Plasmodesmata: Minute pores in the primary cell wall through
which membranes traverse between cells, allowing
for interchange of compounds between cells; an
apomorphy for the Charophytes of the green plants.
Primary tissues: Tissues generated from the growth of an
apical meristem.
Primary tissues: Tissues generated from the growth of an
apical meristem.
Procambium: Primary meristem or meristematic tissue which
differentiates in to the primary vascular tissue. Also
called provascular tissue.
Sclereid: A sclerenchyma cell, varied in form, but typically not
much elongated, and having thick lignified secondary
walls with many pits.
Secondary growth: Growth in girth or width by means of
cells produced from lateral meristems.
Secondary phloem: Phloem tissue formed by the vascular
cambium during secondary growth in a vascular plant.
Differentiated in to axial and ray systems.
Secondary tissues: Tissues generated from the growth of a
cambium.
Secondary tissues: Tissues generated from the growth of a
cambium.
Secondary xylem: Xylem tissue formed by the vascular
cambium during secondary growth in a vascular plant.
Starch: A polysaccharide of glucose units (alpha-1,4glucopyranoside) in green plants, functioning as the
high-energy storage compound.
Suberin: A waxy, water-resistant substance, found in stomata,
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Casparian strips of the endodermis, and the cell walls
of cork cells.
Tissue: Group of cells organized in to a structural and functional
unit. Component cells may be alike (simple tissue) or
varied (complex tissue).
Vacuole: One of spaces in cell protoplasm containing air, sap,
or partially digested food.
Vascular bundle: A strand-like part of the vascular system
composed of xylem and phloem.
Vascular Cambium: A cambium that gives rise to secondary
xylem to the inside, and to secondary phloem to the
outside.
Vascular plants: Plants possessing vascular system, members
of Tracheophyta (Pteridophyta and Spermatophyta).
Vascular tissue: A tissue made up of xylem and phloem,
functioning mainly in conduction of water, minerals,
and sugars.
Wax: A type of triglyceride compound that may function as
high-energy storage compounds or secretion products;
a type of ergastic substance.
Wound - An opening that is created when the tree’s protective
bark covering is penetrated, cut, or removed, injuring
or destroying living tissue. Pruning a live branch creates
a wound, even when the cut is properly made.
Xylem: The principal water-conducting tissue in vascular plants
characterized by the presence of tracheary elements.
The xylem may also serve as a supporting tissue,
especially the secondary xylem (wood).
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