Abstract
It was found that the inhibition of callus tissue growth in Nicotiana tabacum L. cultured in vitro by the application of morphactin IT 3233 is associated with a rise of the protein level in spite of a 50 per cent depression of its synthesis. Respiratory activity of these tissues is also lowered. Tumour tissues, on the other hand, show only light changes in the parameters studied. It would seem that morphactin depresses a metabolic activity in the callus tissues, and probably causes deposition of a, large quantity of metabolically inactive proteins.