ISA Arborist Chapter 1

Abscission Zone

Area at the base of the petiole where cellular break down leads to leaf and fruit drop.

Absorbing root

Fine,fibrous roots that take up water and minerals. Most absorbing roots are within the top 12 inches (30cm) of soil.

Adventitious bud

Bud arising from a place other than a leaf axil or shoot tip,usually as a result of hormonal triggers.

Aerial root

Aboveground roots. Usually adventitious in nature and sometimes having unique adaptive functions.

Angiosperm

Plant with seeds borne in an ovary. Consist of two large groups: Monocotyledons(grasses, palms,and related plants) and dicotyledons(most woody trees,shrubs,herbaceous plants,and related plants). Contrast with gymnosperms.

Anthocyanin

Red or purple pigment responsible for those colors in some parts of trees and other plants. Compare to carotenoid.

Antitranspirant

Substance applied to the foliage of plants to reduce water loss(transpiration)

Apical bud

Bud at the tip of a twig or shoot.

Apical dominance

Condition in which the terminal bud inhibits the growth and development of the lateral buds on the same stem formed during the same season.

Apical meristem

Growing point at the tips of shoots and roots.

Apoplasm

Free spaces in plant tissue. Includes cell walls and intracellular spaces. Contrast with Symplasm.

Auxin

Plant hormone or substance that promotes or regulates the growth and development of plants. Produced at sites were cells are dividing,primarily in the shoot tips. Auxin-like compounds may be synthetically produced.

Axial transport

Movement of water,minerals or Photosynthates longitudinally with in a tree.

Axillary bud

Bud in the axil of a leaf. Lateral bud.

Branch bark ridge

Raised strip of bark at the top of a branch union, where the growth and expansion of the trunk or parent stem and adjoining branch push the bark into a ridge.

Branch collar

Area were a branch joins another branch or trunk that is created by the over lapping vascular tissues from both the branch and the trunk. Typically enlarged at the base of the branch.

Bud

(1) small lateral or terminal protuberance on the stem of a plant that may develop into a flower shoot. (2) Underdeveloped flower or shoot containing a meristematic growing point.

Buttress root

Roots at the trunk base that help support the tree and equalize mechanical stress.

Cambium

Thin layer(s) of meristematic cells that give rise (outward)to the phloem and (inward) to the xylem,increasing stem and root diameter.

Carbohydrate

Compound,combining carbon,hydrogen,and oxygen,that is produced by plants as a result of photosynthesis. Sugars and starches.

Carotenoid

Yellow,orange,or red pigment responsible for those colors in some parts of the trees and other plants. Compare to Anthocyanin

Cellulose

Complex carbohydrate found in the cellular walls of the majority of plants and algae and certain fungi.

Chlorophyll

Green pigment of plants found in the chloroplast. Captures the energy of the sun and is essential in photosynthesis .

Chloroplast

Specialized organelle found in some cells. Site of photosynthesis .

CODIT

Acronym for Compartmentalization Of decay in trees.

Companion cell

Specialized cell in the angiosperm phloem derived from the same parent cell as the closely associated,immediately adjacent sieve tube member.

Compartmentalization

Natural defense process in trees by which chemical and physical boundaries are created that act to limit the spread of disease and decay organisms.

Cork cambium

Meristematic tissue from which the Corky, protective outer layer of bark is formed.

Cuticle

Waxy layer outside the epidermis of a leaf that reduces water loss and resist insect damage.

Cytokinin

Plant hormone involved in cell division,leaf expansion,and other physiological processes. Compounds with Cytokinin -like activity may be synthetically produced.

Deciduous

Tree or other plant that sheds all of its leaves according to a genetically scheduled cycle as impacted by climate factors (usually during the cold season in temperate zones).Contrast with evergreens.

Decurrent

Rounded or spreading growth habit of the tree crown. Contrast with excurrent.

Differentiation

Process in the development of cells in which they become specialized for various functions.

Diffuse porous

Pattern of wood development in which the vessels and vessel sizes are distributed evenly throughout the annual ring. Contrast with ring porous.

Dormant

In a period of dormancy.

Ecology

Study of the relationships among organisms and other living and nonliving elements of there environment .

Epicormic

Arising from a latent adventitious bud (growth point).usually in reference to a shoot.

Evergreen

Tree or other plant that does not shed all of its foliage annually. Contrast with deciduous.

Excurrent

Tree growth habit characterized by a central leader and a pyramidal crown. Contrast with decurrent.

Fiber

(1) elongated,tapering,thick -walled cell that provides strength to wood. (2) smallest component of rope.

Frond

Large,divided leaf structures found I palms and ferns.

Geotropism

Plant growth as a response to the force of gravity,either positive,as in the direction of gravity (roots),or negative,as in opposite the direction of gravity (shoots).

Growth ring

Rings of xylem that are visible in a cross section of stem,branches,and roots of some trees. In temperate zones,the rings typically represent one year of growth and are sometimes referred to as annual rings.

Guard cell

Pair of specialized cells that regulate the opening and closing of a stomate due to a change in water pressure within cells.

Gymnosperm

Plants with exposed seeds,usually with cones. Contrast with Angiosperm.

Heartwood

Wood that is altered (inward) from sapwood and provides chemical defense against decay-causing organisms and continues to provide structural strength to the trunk . Trees may or may not have heartwood. Contrast with sapwood.

Included bark

Bark that becomes embedded in a crotch (union) between branch and trunk or between codominant stems. Causes a weak structure.

Inflorescence

Cluster of flowers.

Internode

Region of the stem between two successive nodes. Contrast with node.

Lateral bud

Vegetative bud on the side of a stem. Contrast with terminal bud.

Lateral root

Root that arises by cell division in the pericycle of the parent root and then penetrates the cortex and epidermis.

Leaf axil

Point of attachment of a leaf petiole to a stem.

Lenticel

Small openings in the the bark that permits the exchange of gases.

Lignin

Organic substance that impregnates certain cell walls to thicken and strengthen the cell to reduce susceptibility to decay and pest damage.

Meristem

Undifferentiated tissue in which active cell division takes place. Found in the root tips,buds,cambium,cork cambium,and latent buds.

Monocot

Plant with an embryo that has one seed leaf(cotyledon). Examples are grasses and palms. Contrast with dicotyledon .

Mycorrhizae

Symbiotic association between certain fungi and the roots of a plant.

Node

Slightly enlarged portion of a stem where leaves and buds arise. Contrast with internode.

Osmosis

Diffusion of water through a semi-permeable membrane from a region of higher water potential(lower salt concentration) to a region of lower water potential(higher salt concentration).

Parenchyma cell

Thin walled,living cells essential in photosynthesis, radial transport,energy storage,and production of protective compounds.

Periderm

The outer layers of tissue of woody roots and stems, consisting of the cork cambium and the tissues produced by it,such as bark.

Petiole

Stalk or support axis of a leaf.

Phloem

Plant vascular tissue That transports Photosynthates and growth regulators. Situated on the inside of the bark,just outside the cambium. Is bidirectional (transports up and down). Contrast with xylem.

Photosynthate

General term for the sugars and other carbohydrates produced during photosynthesis.

Photosynthesis

Process in green plants (and in algae and some bacteria) by which light energy is used to form glucose (chemical energy) from water and carbon dioxide.

Phototropism

Influence of light on the direction of plant growth. Tendency of plants to grow toward light.

Plant growth regulator

Compound effective in small quantities that affects the growth and/or development of plants. May be naturally produced (hormone) or synthetic. See plant hormone.

Plant hormone

Substance produced by a plant that,in low concentrations,affects physiological process such as growth development ,often at a distance from the substance point of Origin. See plant growth regulator.

Primary growth

Root and stem growth in length. Occurs at the apical meristems and lateral meristems of all vascular plants.

Propagation

Process of increasing plant numbers, both sexually and asexually.

Radial transport

Lateral movement of substances,perpendicular to the longitudinal axis of the tree or stem.

Ray

Parenchyma tissues that extend radially across the xylem and phloem of a tree and function in transport, storage, structural strength and defense.

Reaction zone

Natural boundary formed chemically within a tree to separate damaged wood from existing healthy wood. Important in the process of Compartmentalization.

Respiration

In plants,process by which carbohydrates are converted into energy by using oxygen.

Ring porous

Pattern of wood development in which the large diameter vessels are concentrated in the early wood. Contrast with diffuse porous.

Root crown

Area where the main roots join the plant stem,usually at or near ground level. Root collar.

Root initiation zone

Region at the base of a palm stem where lateral roots emerge.

Root mat

Dense network of roots near the base of a palm.

Sapwood

Outer wood (xylem) that is active in longitudinal transport of water and minerals.contrast with heartwood.

Secondary growth

Increase in root and stem girth or diameter. Occurs at lateral meristems in some vascular plants such as dicots.

Sieve cell

Long,slender phloem cell in gymnosperms.

Sieve tube element

Specialized phloem cells involved in Photosynthate transport. Exist only in angiosperms.

Sink

Plant part that uses or stores more energy than it produces.

Sinker root

Downward growing roots that provide anchorage and take up water and minerals. Especially useful during periods of drought.

Source

In physiology ,plant part that produce carbohydrates. Mature leaves are sources.

Stomata

Small pores, between two guard cells on the undersides of leaves and other green plant parts,through which gases are exchanged and water loss is regulated.

Symbiosis

Association of two different types of living organisms that is often,but not always,beneficial to each.

Symplasm

Entire mass of protoplasm of all the cells in a plant,interconnected by plasmodesmata.symplast. Contrast with Apoplasm.

Tap root

Central,vertical root growing directly below the main stem or trunk that may or may not persist into plant maturity.

Temperate

Region lying between the tropics and the poles that has relatively moderate temperatures.

Terminal bud

Bud at the tip of Steiger or shoot. Apical bud. Contrast with lateral.

Tracheid

Elongated,tapering xylem cell adapted for the support and transport of water and elements.

Transpiration

Water vapor loss through the stomata of leaves.

Tropism

Tendency of growth or variation of a plant in response to an external stimulus such as gravity (geotropism)or light (phototropism ).

Vessel

End to end,tubelike,water-conducting cells in the xylem of angiosperms .

Xylem

Main water and mineral conducting (unidirectional,up only) tissue in trees and other plants. Provides structural support. Arises (inward) from the cambium and becomes wood after lignifying. Contrast with phloem.