Investigation on the occurrence and significance of cyclic adenosine 3':5'-monophosphate in phytoplankton and natural aquatic communities

Synthesis and release of cyclic adenosine 3′:5′‐monophospliate by aquatic macrophytes

“…The release rates of cAMP noted in these platits and the preponderance of macrophytic biomass present in many small lakes suggest that macrophytes may be an itnportant source of dissolved cAMP io lakewater. In Lawrence Lake and Wintergreen Lake,, we noted that dissolved cAMP levels range from undetectable quantities to over 6000 pmol 1~' during the year (Francko 1980, Francko andWetzel 1981b), Our data suggest that much of this cAMP, particularly in waters of the extensive littoral zones of these lakes, may have originated from macrophytic release, although speculation as to actual proportions between algal and macrophyte release are pretuature. Further investigations into the production and release of cAMP by aquatic macrophytes and its potential physiological significance are clepriy warranted.…”

“…Similar investigations have not been conducted on any species of aquatic vaseular plant. We have documented the existence of both plankton-associated and dissolved cAMP in lakewater from two trophically dissimilar aquatic systems (Francko 1980, Francko andWetzel 1981b), Our evidence indicated that dissolved cAMP, which cotnprised the bulk of the total cAMP fraction in both lakes, could have resulted from combined release by algae, bacteria, and other organisms. Aquatic macrophytes dominate the overall biomass and primary productivity of both systetns we examined (Wetzel 1975(Wetzel , 1979, a patterti common to most stnall lakes.…”

“…We collected young, whole plants from each lake which were essentially free of visible epiphyte encrustations. These specitnens were immediately returned to the laboratory and mechanically surfaoe-disinfested, Plate counts of macerated plant samples, direct microscopic examination of plant leaf stirfaces, and scrapings from leaf surfaces demonstrated that epiphytes and endophytes remaining following these procedures accounted for < 0,2% of the total fresh weight biomass of each plant sample, reducittg potential contributions of tissue and dissolved cAMP frain contaminant sources to unmeasurably small qtiantit'fes (Francko 1980, Francko andWetzel 1981b).…”

“…Tissue and filtrate cAMP levels were evaluated by the methods of Bressan etal. (1980a, b), Francko (1980), and Francko andWetzel (1980, 1981a, b). Tissue cAMP levels were evaluated by macerating plant samples (1 to 8 g fresh wt) in 0,5 M HCIO4 (2.0 ml g"') at O-C, at which point 20,000 cpm (0,5 pmol) of ^H-cAMP was added as an internal standard.…”

“…Cyclic AMP binding protein, isolated from bovine heart (Kuo and Greengard 1972) was used to assay cAMP by the Gilman protein binding assay (Gilman 1972), Contamination by cAMP potentially present in glassware or reagents never exceeded the detectability limits of the assay (0,01 pmol assay tube"'). Cyclic AMP-dependent protein kinase from bovine heart was used to assay cAMP by the luciferin-luciferase method (Handa and Bressan 1980, Francko 1980, Francko and Wetzel 1980, 1981b.…”