Genome Organization and Variation in Higher Plants

The plant genome can be considered to be in a state of flux with many changes occuring during development and reproduction. In particular, variation can occur in response to various internal and external influences. Examples of these alterations are the generation of somaclonal variation during the passage of plant cells through cycles of tissue culture and regeneration, and the environmental induction of heritable changes in flax. The characterization of the genomic changes have indicated that they mainly occur in the highly repetitive fraction of the genome and are limited to a specific subset of these sequences. These subsets may be localized at particular chromosomal sites. One possible function of these genomic variations is the generation of a radical, but limited, reorganization of the genome in response to stress in order to increase the pool of variability from which new types can be selected. However, there has not been a direct demonstration of the adaptive value of any of these reorganizations.