ABSTRACT
Plant physiology is the study of how plants function, and an understanding of the basic plant physiological principles helps explain the success or the lack of success of the various techniques and practices used in plant propagation. A multitude of genetic or physiological factors inuence plant response, whether the propagation occurs in the eld, greenhouse, or in the laboratory. Metabolic and physiological processes in the plant are profoundly inuenced by the environment of the plant, including light
(intensity; day length; and quality, including light sources and wavelength differences), temperature, water relations, photoperiod, and season. A plant propagator must make decisions about the techniques to be employed, and these will be inuenced by the type of plant that is being propagated (annual, biennial, or perennial) and whether a clone is desired. A clone is an offspring that is genetically identical to the parent and produced with mitotic divisions of cells and not meiosis (Chapter 5). The use of
Concept Box 3.1
cloning goes back to primitive agriculture, where pieces of woody stems were inserted into the ground to root, thus producing new plants. Clonal propagation maintains the genetic integrity of propagules through generations; it is also utilized to bypass or reduce the juvenile period and the characteristics of the growth forms associated with it, such as thorniness, juvenile leaf morphology, and the vegetative or nonowering state. Much more can be learned about juvenility in Chapter 6. Clones of selected seed-propagated plants allow the widespread exploitation of unique traits or characters. Through the process of budding or grafting, the traits of a single desirable tree or even a branch (with a sport or desirable mutation) can be vegetatively perpetuated. A wonderful example of this is the ‘Delicious’ apple, which originated as a chance seedling in Iowa and is now commonly budded or grafted onto rootstocks to retain its unique features. Foresters also use cloning to perpetuate valuable traits in trees and describe the original seedling as an “ortet” and use the term “ramet” to designate its vegetative offspring or clone.
