Effects of Temperature on the Metabolic Pattern of Incorporation of 14C by the Moss Dicranum Scoparium Incubated with Acetate- 2-14C

Mosses (Dicranum scoparium) preconditioned at both high (12°-22°C) and low (0°10°C) ambient temperature ranges, and studied at incubation temperatures of 5°C or 22°C respectively, actively metabolized acetate-2-C. These plants malic, citric, aspartic, and glutamic acids became highly radioactive. The radioactivity was followed by solubility, columnand thin-layer chromatography, radioautography, and liquid scintillation spectrometric determinations. A change in incubation temperature brought about a qualitative change of the C-incorporation within each metabolic pool. This qualitative change was expressed by a shift in relative radio-activity within each pool. The shifts of labeling were particularly noticeable among such individual compounds as aspartic, glutamic, malic, citric acids, glutamine, dextrose, and two lipid-fatty acid components. The data suggest that temperature affects those biochemical processes that involve the compounds which showed a shift in radioactivity. Hence, it implies that biochemical processes are closely associated with temperature changes. This study indicates that not only are Kreb cycle acids actively metabolized in mosses, but the amount found is associated with temperature changes. INTRODUCTION Except for the lipid-fatty acid group of compounds (James and Nichols, 1966; Canvin, 1965; and Harris and James, 1969), little is known about the metabolic pattern of non-vascular plants such as mosses under cold acclimation or stress temperatures. Many species of this group of plants are known for their hardiness and their wide distribution in the temperate as well as in the tundra habitat. Aside from being non-vascular plants, mosses have metabolic features similar to those of higher plants. They possess photosynthetic ability, and have been found to contain tricarboxylic cycle acids (TCA), amino acids, and other aromatic acids (Maass and Craigie, 1964; Walland and Kinzel, 1966; and Harris and James, 1969). An increase in unsaturation of lipids and fatty acids was observed in mosses when Contribution 268, Institute of Polar Studies, The Ohio State University, 125 South Oval Drive, Columbus, Ohio 43210. Manuscript received April 2, 1973 (73-30). THE OHIO JOURNAL OF SCIENCE 74(3): 200, May, 1974 No. 3 TEMPERATURE EFFECTS ON MOSS METABOLISM 201 the temperature was lowered (James and Nichols, 1966; Harris and James, 1969; Wolf et al., 1967; and Canvin, 1965). Moss plants with a wide range of tolerance also have greater ranges of gas exchange in photosynthesis and respiration (Rastorfer and Higginbotham, 1968). The present study examines the metabolic pattern in mosses under two different ambient temperatures: 22°C, and 5°C. The metabolic patterns were studied by the pattern of C-incorportation into selected metabolic pools which were isolated from mosses incubated with 14Clabeled substrate. Sodium acetate-2-C was incubated with moss plants which had been preconditioned and maintained in growth chambers. Following incubation, various metabolic pools in the form of amino acids, organic acids, lipids-fatty acids, and sugars were isolated from the plant and their radioactivities determined. The evolved carbon dioxide from the incubation was trapped and each metabolic pool, which had incorporated radioactive carbon-14 was further analyzed by thinlayer chromatography (TLC) and radioautography in order to examine the r e distribution within each metabolic pool. MATERIALS AND METHODS Dicranum scoparium (Hedw.), maintained in growth chambers for about 6 months at either 12° to 22° (designated "HT") or 0° to 10° (designated "LT"), were used in this study. Ten gametophytes of D. scoparium were placed in reaction vessels containing 7 ml of phosphate buffer solution (0.25 M Na2HPO4, pH 6.4) and kept in the growth chambers for 12 hours prior