Evidence against mediation of adenosine-3',5'-cyclic monophosphate in the bud-inducing effect of cytokinins in moss protonemata

Effects Oif adenosdne-3',5'-cyclic monophosphate (cAMP), N⁶,O²-dibuityryl adenosine-3',5'-cyclic monophosphate (DBcAMP), caffeine and theophylline on the bud-inducing activity of cytokinin in the protonema of two moss species, <i>Ceratodon purpureus</i> and <i>Funaria hygrometrica</i> were examined. The sub-stances have been found ineffective as gametophore bud inducers. Some synergism between cytokinin and cAMP or DBcAMP was observed with relation to the buds' growth, but this effect is nonspecific since it can be obtained with 5'-AMP or 5'-GMiP as well, The results seem to exclude the possibility of an involvement of cAMP as a second messenger in the mechanism of cytokinin action on morphogenetic processes in moss protonemata.

The role of cytokinins in the development and metabolism of barley leaves. I. The effect of cytokinins on leaf senescence

The loss of chlorophyll during dark-induced ageing of barley leaves was prevented to a similar extent by kinetin and the natural cytokinin, 6-Δ²-iso-pentenylarninopurine (2iP). A concentration of 400 μM appeared to be optimal in both cases. In the presence of 2iP the structure of mesophyll cells in dark-incubated leaves was maintained unchanged. A distinct correlation has been found between the retardation by 2iP of the chlorophyll loss, the rate of S2P-incorporation into nucleic acids and the maintaining of the RNase activity at a low level. The importance of the RNA synthesis and the rate of its de-gradation in the cytokinin action in barley leaf senescence will be subjected to future experiments.