Definitions Plant genetics

Compounds formed in response to stress may occur in at least two ways. In one response, the plant may form compounds throughout the tissue at a considerable distance from the infection site (Hammerschmidt, 1999). In another response, the plant may form compounds specifically at the infection site. This may include only a few cells and in rare cases, as few as one or two cells. (Snyder and Nicholson, 1990 Nicholson and Wood, 2001). In general, such compounds are referred to as either stress metabolites or more often as phytoalexins. By definition phytoalexins are formed in response to infection (Aguero et al., 2002 Lo et al., 2002 Hammerschmidt and Nicholson, 2001 Lo and Nicholson, 1998). Phytoalexins often exhibit toxicity to specific pathogens. In this case there is a genetic relationship between the expression of phytoalexin synthesis and the organism that induces that synthesis (Essenberg et al., 1985). 

With the exception of THC and its analogs, no other cannabinoids have definite psychoactivity, and the content of THC varies considerably among plants. Special genetic plant lines may produce as much as 4-6% THC content. 

Definitive assessment of the contribution of PEs to the deterrence of invertebrate predators must await the comparison of the susceptiblity of genetic lines of the same plant species which differ in their ecdysteroid levels and/or profiles [26],... 

The definition of a species, whether of higher plants, animals, or microorganisms, has as its basis the principle of genetic isolation. Simply put, members of a species are considered interfertile, whereas genetically separate species are not.3 When measurements of DNA reassociation are used to define species, the extent of DNA relatedness expected between members of a species must first be determined. The discussion at the conclusion of this chapter addresses this issue and offers guidelines for predicting genetic relatedness from the extent of DNA complementarity. 

Transformation In plant cell culture, the introduction and stable genomic integration of foreign DNA into a plant cell by any means, resulting in a genetic modification. This definition is the traditional microbiological definition. For animal cell culture, see In vitro transformation , In vitro neoplastic transformation and Transfection . 

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