| The purpose of this study was to use anthocyanin-producing cell cultures of Eucalyptus tereticornis to study the relationship between osmotic stress and anthocyanin synthesis. The initial hypothesis was that the synthesis of anthocyanins in response to osmotic stress is due to a decline in chlorophyll levels which in turn causes an increase in anthocyanin levels to provide protection of cell components from harmful radiation.;This study not only showed the utility of cell cultures for studying stress-related metabolism but it also showed various metabolic changes that occur in plant cell cultures of E. tereticornis in response to osmotic stress. Initial studies using callus cultures were conducted to evaluate the effect of light intensity, the type and concentration of auxin, and mannitol-induced osmotic stress on growth and anthocyanin synthesis. Additional osmotic stress experiments were conducted using suspension cultures to study the effect of mannitol-induced osmotic stress not only on anthocyanin synthesis but also on chlorophyll, soluble sugar and free amino acid levels.;Based on the results of this work several important conclusions are made about cellular responses to osmotic stress in E. tereticornis cultures. First, evidence is presented that cell cultures of E. tereticornis respond to increasing osmotic stress with an increase in anthocyanins levels. However, indirect evidence is also presented which indicates that this response may indeed be dependent on chlorophyll levels in the cells. Second, levels of sucrose were shown to decrease in response to increasing osmotic stress, possibly indicating that sucrose, which accumulates in the cells, may be used as a carbon source for stress-related metabolism. Third, results showed that E. tereticornis cultures respond similarly to other plants by increasing levels of free amino acids in response to osmotic stress. Results also showed that the most dramatic increase occurred in the level of proline while the level of phenylalanine, a precursor to anthocyanins, did not show any significant response to osmotic stress. |
