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http://www.paeon.de/h1/st/
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http://www.peonynursery.com/
http://www.dutchgardens.com/
http://www.bloomingbulb.com/
www.volny.cz/in-vitro/pivonky_cz
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Recalcitrance of Woody and Perennial Plants: Dealing with Genetic Predeterminism    BRENT H. MCCOWN

As a general group, long-lived perennial plants probably present the most challenging obstacles to the researcher, breeder, or propagator utilizing microculture as a tool. These challenges appear at all stages of the microculture process, but are probably most resplendent during the isolation phase. What may be particularly frustrating is that much of this recalcitrance is genetically driven, thus difficult to control by environmental manipulations in microculture. Although somewhat arbitrary non-exclusive groupings, three major sources of genetically-determined recalcitrance can be recognized. Probably the most studied is physiological phase state (ontogenetic change). Phase state is a multi-stage phenomenon (juvenile, adult vegetative, adult reproductive). Current theory envisions that each stage may be independently regulated by intergrading developmental programs under the influence of both endogenous and exogenous signals. In practice, juvenile tissues are the most responsive in microculture, particularly for woody plants. Manipulation of the source material and culture scenarios are the only generally successful means of control. A second phenomenon, determinant shoot growth, can be problematic in both herbaceous and woody perennial microculture. In some cases, determinant growth may be tied closely with phase state and can thus be controlled by manipulating phase, however, adequate controls have not been identified for many problematic plants. Finally, some genotypes of plants do not respond to microculture, even though other closely related selections are readily cultured and phase/determinant growth do not appear to be involved. Again, generally applicable physiological/genetic reasons largely remain unknown. Examples of all three sources of recalcitrance and the experimental approaches to overcoming them will be discussed.

A General Approach for Developing a Commercial Micropropagation System   B. MCOWN AND D. MCOWN

Five distinct steps can be recognized in the establishment of a plant in a commercial micropropagation system, especially if the most utilized approach (shoot culture) is the focus. Failure at any one step can make the total system commercially infeasible. When considering a plant without extensive previous history of microculture, the first step involves an analysis of the potential market (economic reality) as well as the plant's general growth habit (biological reality). The general growth habit of the plant can provide valuable predictive information as to the potential ease of microculture. For example, plants showing indeterminant herbaceous growth (e.g. Chrysanthemum, Solanum, Dieffenbachia) or continuous woody seasonal growth (e.g. Betula, Ulmus, Thuja) are generally much more amenable to microculture than those that are determinant herbaceous (e.g. Panix, Paeonia) or episodic woody organisms (e.g. Quercus, Pinus). At times, an episodic habit can be overcome in microculture (Syringa, Rhododendron). The next four steps involve the actual manipulation and microculture of the plant and include the initiation, stabilization, optimization, and production phases. The most intensive analytical step is usually the optimization phase where hommonal response curves, replication, repetition through multiple subcultures, and evaluation of productivity and product quality are involved.