Search

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]

A previous paper reported a close correlation between cell division as influenced by kinetin and respiration, i.e. a high kinetin induced cell division rate corresponds with low oxygen consumption of the explants. This earlier observation was now confirmed. No significant differences between the ultrastructure of mitochondria of explants cultured with kinetin and those of explants cultured without kinetin could be observed, although the number of mitochondria per cell seems to be increased in explants cultured without kinetin. However, also the number of ribosomes in cells of explants cultured without kinetin seems to be increased as compared with those treated with kinetin. Kinetin apparently has no significant influence on the ultrastructure of cell organells under the conditions employed. [ABSTRACT FROM AUTHOR]