Oxidative stress and physiological, epigenetic and genetic variability in plant tissue culture: implications for micropropagators and genetic engineers

A number of well defined problems in physiological, epigenetic and genetic quality are associated with the culture of plant cell, tissue and organs in vitro, namely, absence or loss of organogenic potential (recalcitrance), h yperhydricity ('vitrification') and somaclonal variation. These broad terms are used to describe complex phenomena that are known to be genotype and e nvironment dependent. These phenomena affect the practical application of p lant tissue culture in plant propagation and in plant genetic manipulation. Here it is hypothesised much of the variability expressed in microplants m ay be the consequence of, or related to, oxidative stress damage caused to the plant tissues during explant preparation, and in culture, due to media and environmental factors. The characteristics of these phenomena are descr ibed and causes discussed in terms of the known effects of oxidative stress on eukaryote genomes. Parameters to characterise the phenomena are describ ed and methods to remediate the causes proposed.