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Saturday, January 23, 2010

Definitions and Terminology for Propagation

Buds on a named-variety of Ceanothus - all Ceanothus hybrids are propagated by cuttings; the hybrid can't be maintained any other way because the crosses aren't stable.

Apical dominance Apical dominance is phenomenon where the tip of the main trunk or branch bears the dominant meristem. The tip is apical meristem. This allows the convenience of the tip to grow fast and avoid being shadowed by branches. If the dominant meristem is removed, one of the nodes left on the branch or trunk will assume dominance, usually the topmost bud/node. 

Apical meristem The growing tip composed of completely undifferentiated meristematic tissue, these are the buds (nodes) and growing tips of roots in plants.

Asexual reproduction (also known as vegetative reproduction) Any reproduction in plants that does not involve meiosis or fertilization; there is only one parent contributing genetic material to the resulting offspring – they are, in effect, “cloned.”

Bud See node.

The mass of parenchyma cells that develops from and around wounded plant tissues in order to diminish evaporation from the wound and initiate healing. In grafting it occurs at the junction of a graft union, arriving from living cells of both scion and stock. The production and interlocking of these parenchyma (or callus) cells constitute one of the important steps in the healing process of a successful graft.

Cambium A thin meristematic tissue of the plant located between the bark and the wood. Its cells are are capable of dividing and forming new cells. For a successful graft union, it is essential that the cambium of the scion be placed in close contact with the cambium of the stock.

Clone A population of genetically identical cells or individuals. Such a population is obtained by mitotic division or by asexual reproduction.

Distal The distal end of either the root or the shoot is that furthest from the stem-root junction of the plant and nearest to the tip of the shoot or root. Alt. proximal. See polarity.

Dormant/dormancy (buds) A bud which have stopped its development for a period due to unfavorable environmental conditions (e.g. a dry or cold season). A dormant bud will sprout as a response to improved growth conditions or a “biological clock” e.g. longer days.

Grafting The connection of two pieces of living plant tissue in such a manner that they will unite and subsequently grow and develop as one plant.

Grafting wax Substance applied on the graft union in order to minimize desiccation and exclude water access.

Graft union The site of the grafted plant where the scion and the root stock are united.

Hedging Trimming trees and keeping them low in order to overcome or bypass the poor rooting and often poor form of cuttings from old trees. Cuttings from hedged plants tend to maintain their young physiological age.

Hormone A substance that has a marked effect on a specific plant part and produces this effect when present in very low concentrations, e.g. promotion of root, shoot or flower development. Hormones are produced within the plant but artificial synthesized plant hormones applied to the plant part have the same effect.

Incompatibility (graft incompatibility) Inability of the stock and the scion to form or maintain a union that will result in the desired plant growth.

Meristem (meristematic tissue) This is tissue in all plants consisting of undifferentiated cells (meristematic cells) and found in zones of the plant where growth can take place. Grafting and cuttings rely on this phenomenon of plant physiology to achieve results.

Node The horticultural term for a point of the stem from which one or more leaves arise or can arise. In the mature stem the nodes are usually well separated by internodes which elongate during growth. Apical meristem is the botanical term. Nodes may be dormant and only visible as a slight swelling along a stem.

Scion An aerial plant part, often a branchlet, that is grafted onto the root bearing part (stock/root-stock) of another plant.

Sexual reproduction  Plants reproduce sexually in a number of ways, but for the purpose of this course where we are dealing with primarily higher (flowering) plants, sexual reproduction takes place through pollen from a male flower being transferred to the female flower and the resulting fertilization resulting in the growth of seeds with the following generation having genetic traits of both parents.

Strike Slang for a cutting that has rooted. Occasionally used as a verb for the act of making a cutting.

Stock/root stock The lower portion of the graft, which develops into the root system of the grafted plant. It may be a seedling, a rooted cutting or a layered plant.

Take A slang term for the phenomenon of the successful union of stock and scion and growth of the grafted plant.


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