Adenosine 3':5'-cyclic monophosphate: Occurence and putative function in Nicotiana tabacum

The experiments, presented in this thesis are a contribution to the elucidation of 3':5'-cAMP metabolism in higher plants. Using the chloroplast as a physiological entity the presence of 3 ':5'-cAMP together with adenylyl cyclase activity and phosphodiesterase activity was demonstrated. Trying to achieve this objective three different complementary methods were applied; analytical biochemistry, immunocytochemistry and histochlemistry. In order to present convincing results great effort was put in the development of an analytical method for 3':5'-cAMP quantification and this technique was ultimately applied to analyse adenylyl cyclase activity in the femtomole region. These measurements directed to evidence for significant similarities of plant adenylyl cyclase and other eukaryotic adenylyl cyclase. Using the same techniques the chloroplast was analysed for its (isoprenoid) cytokinin content.;In a parallel research immunocytochemical localisation provided additional evidence for the occurrence of 3':5'-cAMP and cytokinins in chloroplasts. The emphasis of this part of research was put on the exploration of 'unconventional' methods like high pressure freezing and molecular distillation drying, in order to ascertain that the least possible diffusion could take place during sample processing. The histochemical technique was used to demonstrate adenylylcyclase activity at the electronmicroscope scope level and can be used as a complement to the biochemical experiments.