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The transition from resting to mitotically active potato tissue (excised disks) is accompanied by and virtually dependent on transcription, translation and increased metabolic activity. Thus enhanced RNA- and protein-syntheses are well known features of potato tuber slices, allowing the cells to raise the level of several metabolic pathways (i.e., starch breakdown, pentose phosphate shunt, glycolysis, respiration and others) and ultimately leading to mitotic activity. Mitosis can be totally, yet reversibly suppressed by incubation of the tissue fragments in Tris (hydroxymethyl)-aminomethane buffer. Neither total respiration nor its sensitivity to several inhibitors is affected during blockage of mitosis. Fluctuations in the levels of glucose-6-phosphate, fructose-6-phosphate, phosphoenolpyruvate and pyruvate are exactly the same in Tris-inhibited as in non-inhibited cells. Thus the Tris ion is not modifying blucose catabolism. The same is true for the time-course of activity of hexokinase, glucose-6-phosphate- and 6-phosphogluconate dehydrogenase, glucosephosphate isomerase, triosephosphate isomerase, enolase, hosphoglyceromutase and "malic enzyme". Although the rapid decrease in activity of phosphoglucomutase, aldolase, pyruvate kinase and glutamic-pyruvic transaminase after slicing (characteristic for non-inhibited cells) does not occur in Tris-treated tissue, these small differences are not thought to be causative in inhibition of mitosis. The results indicate, that nucleic acid metabolism is more likely the target of the Tris-ion. [ABSTRACT FROM AUTHOR]

During investigations of their metabolism fragments of plant tissue are most commonly incubated in watery solutions in order to replace the conditions within the intact organ approximately. -- This paper reports experiments performed to investigate the influence of a hypotonic medium on several parameters of importance in cell metabolism (protein synthesis, enzymatic activity, concentrations of metabolic intermediates, respiration, and cell division). -- It could be shown that protein synthesis is severely inhibited in hypotonically exposed potato tuber discs. As a consequence the activities of two dehydrogenases of the pentose phosphate shunt (glucose-6-phosphate- and 6-phosphogluconate-dehydrogenase) are very low as compared with tissue in air. Since the activated pentose shunt evidently contributes to the respiratory reaction after derepression of the tissue, lowered activities of these dehydrogenases must consequently result in lower respiratory activity. This is actually realized in washed tissue, Likewise the mitotic activity is inhibited to a considerable extent. -- The destruction of permeability barriers within the cell as a consequence of slicing causes leakage of a variety of metabolites such as glucose, glucose-6-phosphate, fructose-6-phosphate and pyruvate. Thus leaching of metabolic active substances is certainly one of the causal factors in the complex reaction of tissue slices exposed to a hypotonic medium, although such important parameters as changes gas conditions and the various effects of altered hydration of cell cytoplasm must be considered. [ABSTRACT FROM AUTHOR]