Mitochondrial activity during shoot formation and growth in tobacco callus

Mitochondria isolated from tobacco ( Nicotiana tabacum L. cv. Wisconsin 38) callus growing on either shoot-forming or non-shoot forming medium show an increase in state 3 and state 4 respiration and a drop in respiratory control and ADP/O ratios after subculture. the protein content of the mitochondria fraction and the activity of succinate dehydrogenase, malate dehydrogenase, cytochrome c oxidase and catalase also increase after subculture but there is no apparent difference between shoot-forming and non-shoot-forming tissue. For mitochondria assayed at their native osmolarities, a trend of higher respiration rates and respiratory control as well as lower levels of cyanide-resistant respiration was observed for shoot-forming tissue. Generally, differences were greatest after day 9 in culture, the time during which primordia formation occurred in the shoot-forming callus. These patterns are in concert with the view that the shoot-forming process has a high energy requirement which must be realized during the time of primordia formation.