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Antagonistic
microorganisms
Bacteria, fungi or other microorganisms that compete
for food, by producing compounds inhibitory to other
microorganisms or by directly parasitizing them.
Apex
The root tip covered by a root cap and secreted
mucilage, i.e. soluble complex sugars (poly
saccharides), which adhere to roots.
Apical
root meristem
The zone of dividing cells at the apex which gives
rise to new cells and eventually new tissues in a
growing root cell.
Bacteria
Primitive, unicellular,
microscopic organisms that lack a cell nucleus and
other organelles, obtain soluble food by absorption,
and reproduce by simple cell division.
Beneficial
fungus
A fungus which has a beneficial effect on an important
process essential to plant growth, ie. mycorrhizal
fungi, litter decomposers, fungi antagonistic to
pathogens, etc.
Biological
control
A term used to describe the use of natural organisms
to reduce the effects of undesirable organisms (pests)
and to favor desirable organisms such as crops, trees,
animals, beneficial organisms or insects.
Casparian
strip
A subarin layer in endodermis that function as a
selective barrier allowing absorption of desirable
elements (N, P, K, Ca, etc.) but blocking absorption
of harmful elements (Na, Al, etc.)
Cellulose
A polysaccharide (i.e., Many sugars) made up of many
glucose molecules chemically bonded together. The most
abundant organic compound on earth. It comprises the
bulk of cell walls of plants where it occurs as
microfibrils (i.e., fiber strands).
Chlorophyll
The green pigment of plant cells necessary for
photosynthesis by capturing light energy and coverting
it to chemical energy.
Colonization
The establishment of a species in a given environment.
Competition
The struggle among organisms for a limited supply of
water, food, light, etc. in a given environment.
Competitors
Refers to two species of organism which compete with
each other for survival by attempting to use the same
substrate or by direct competition with each other.
Cortex
The cell layers occurring between the epidermis and
the stele or vascular cylinder.
Ecosystem
A term used to describe a system of interactions
between living organisms occupying the same
environment.
Ectomycorrhizal
fungi
Species of mycorrhizal fungi with hyphae that grow
only between the cells and over the surface (outside)
of the roots, but do not penetrate the plant cell.
Endodermis
The inner most layer of cortical cells ("inner
skin") found in all roots next to the vascular
cylinder. The endodermis contains a Casparian strip.
Endomycorrhizal
fungi
Species of mycorrhizal fungi with hyphae that
penetrate and live inside the cortical cells of the
plant root.
Epidermis
The outer most layer of cells ("outer skin")
of a growing root in direct contact with the soil.
Ericoid
mycorrhizal fungi
Species of mycorrhizal fungi which exhibit some of the
characteristics of both endo- and ectomycorrhizae, and
are unique to azaleas, rhododendrons, blueberry,
cranberry and eastern mountain laurel.
Fine
absorbing roots
Tiny roots usually located in the upper several inches
of soil that are actively engaged in the uptake of
water and minerals.
Fungus
A non-photosynthetic, chiefly multicellular organism
only able to use carbon, nitrogen, etc. as starting
materials for synthesis of its essential foods.
Fungus
mantle
A sheath made up of the hyphae of an ectomycorrhizal
fungus which surrounds and encompasses the fine
absorbing roots.
Host
An organism on or in a parasite lives.
Hypha
(hyphae, pl.)
A single tubular filament of a fungus.
Hyphal
strand
An aggregation of several individual hyphae into a
thread-like feeding structure.
Indigenous
Existing or growing naturally in a region or country.
Inoculate
To bring one organism into contact with a host plant
or plant organ.
Inoculum
That part of the organism which is brought into
contact with the host or the host environment in order
to establish it there. In the case of the mycorrhizal
fungi, this consists of spores or hyphae of the
beneficial fungus.
Lignin
Phenolic compounds impregnating and strengthening cell
walls. Xylem cells and fibers are typically lignified
but other cells in the stele or cortex can also be
lignified.
Lipids:
Diverse class compounds, including fats, oils, fatty
acids, triglycerides and steroids essential for
membrane formation, energy stores and fuel molecules.
Macronutrients
Mineral elements required by plants in large
amounts - nitrogen, phosphorus and potassium (N-P-K)
Micronutrients
Elements which are required in very small or trace
amounts - iron, chlorine, copper, manganese, zinc,
molybdenum, boron etc.
Mycelium
The mass of hyphae forming the body of a fungus.
Mycorrhiza
(mycorrhizae, pl.)
"Fungus roots" or hyphae of certain
fungi (mycorrhizal fungi) which are symbiotic with the
plant roots on which they occur. The symbiotic
combination of the hyphae and the plant roots.
Nitrogen
fixation
The incorporation of atmospheric nitrogen into
nitrogen compounds that are available for uptake by
green plants, a process that can be carried out only
by certain microorganisms or by higher plants in
symbiotic association with microorganisms.
Nutrients
Refers to the mineral elements usually found in the
soil which are essential for plant growth.
Organs
Tissues that act together to perform functions. The
roots, stems and leaves are the major organs of
plants. All organs are composed of three
tissues…epidermis, vascular tissues and ground
tissues. Ground tissues are those involved in
metabolism (such as photosynthesis), food storage and
physical support.
Parasite
An organism that lives on or in an organism of a
different species and derives nutrients from it.
Pathogen
An organism that causes a disease.
Pericycle
Special cells in endodermis that produce lateral
roots.
Perderm:
The bark layer formed on the surface of roots (or
branches) by secondary growth. It is strenthened by
subarin and lignin.
Phenolics
Acid ring (aromatic) structure, organic compound
derived from other hydrocarbons (i.e. contain C, Hand
O).
Photosynthesis
The process by which carbon dioxide and water are
combined in the presence of light energy and
chlorophyll to form carbohydrates.
Plant
Health Care (PHC) Management
An integrated management approach to plant health
coordinated by the International Society of
Arboriculture, National Arborist Association and USDA
Forest Service; PHC uses multiple tactics and relies
primarily on preventive measures, those that
encourage plant vigor and maintain healthy, balanced
growth, rather than emphasizing chemical treatments
for diseases and insects.
Pt
Letters used to designate Pisolithus tinctorius,
a major ectomycorrhizal fungus.
Radical
(primary root)
The initial root formed after seed germination. This
primary (or first) root produces first-order lateral
roots. The primary root eventually becomes the tap
root of the plant.
Rhizosphere
The soil near a living root, usually applied to the
zone around tiny fine absorbing roots.
Rhizosphere
competent
Term used to designate the ability of a mycorrhizal
fungus or rhizobacteria to successfully occupy the
rhizosphere by growing and spreading onto new roots of
the host plant as roots develop.
Root
hairs
Thin hair-like extensions of epidermal cells formed
behind the root meristem. They increase root contact
with the soil and are important for water and mineral
element uptake but are very short lived.
Root
systems
Composed of primary and secondary roots and different
orders of lateral roots. Different orders of lateral
roots vary in there growth rates, life spans,
structural features, etc. as well as there capacity to
obtain water and mineral elements or to support
mycorrhizae. Higher order lateral roots are generally
thinner, shorter, have shorter life spans and grow
less rapidly than those of lower orders.
Root
tissues
These are produced by cell division in the root tip
(apex) and cell expansion behind the apex (subapex)
regions. The tissues are mainly cellulose and lignin
built with photosynthates. These tissues progressively
mature at greater distances from the root tip.
Saprophyte
An organism that uses dead organic material for food.
Spores
The reproductive unit of fungi, bacteria and other
microbes consisting of one or more cells; it is
analogous to the seed of green plants.
Sporulation
The production of spores.
Stele
or vascular cylinder
This zone inside the endodermis contains specialized
tissues responsible for transport of water and mineral
elements to the shoot (xylem) and organic nutrients,
such as photosynthetically-fixed carbon, to the roots
(phloem). Xylem cells develop lignified walls and are
dead when mature.
Suberin:
A hydrophobic (lacks affinity for water) material,
containing lipids and phenolics, which impregnates the
walls of specialized cells and prevents the passage of
water and other materials in the apoplast.
Substrate
The material on which a microorganism feeds and
develops.
Symbiosis
A mutually beneficial association of two different
kinds of organisms.
Virulence
The degree of pathogenicity of a given pathogen.
VAM
Abbreviation for vesicular-arbuscular mycorrhizal
fungi, the most common type of endomycorrhizae.
Glossary
of Terms
Product
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Product
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Technical
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Technical
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©
2000 PHC Royalty Corp.
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