A potting soil mixture depleted carbon monoxide in a test atmosphere from a concentration of 120 parts per million to near zero within 3 hours. Maximum activity occurred at 30 degrees C. Steam sterilization of the soil, the addition of antibiotics or 10 percent (by weight) saline solution, and anaerobic conditions all prevented carbon monoxide uptake. Sterilized soil inoculated with nonsterile soil acquired activity with time. Samples of various natural soils differed in their ability to remove carbon monoxide from the air. Acidic soils with a high content of organic matter were generally the most active. The soil's ability to remove carbon monoxide from the atmosphere is ascribed to the activity of soil micro-organisms.

Since the diamine putrescine can be metabolized into the pyrrolidine ring of tobacco alkaloids as well as into the higher polyamines, we have investigated the quantitative relationship between putrescine and these metabolites in tobacco callus cultured in vitro. We measured levels of free and conjupted putrescine and spermidine, and pyrrolidine alkaloids, as well as activities of the putrescine-biosynthetic enzymes arginine and ornithine decarboxylase. In callus grown on high (11.5 micromolar) anaphthalene acetic acid, suboptimal for alkaloid biosynthesis, putrescine and spermidine conjugates were the main putrescine derivatives, while in callus grown on low (1.5 micromolar) a-naphthalene acetic acid, optimal for alkaloid formation, nornicotine and nicotine were the main putrescine derivatives. During callus development, a significant negative correlation was found between levels of perchloric acid-soluble putrescine conjugates and pyrrolidine alkaloids. The results suggest that bound putrescine can act as a pool for pyrrolidine alkaloid formation in systems where alkaloid biosynthesis is active. In addition, changes in arginine decarboxylase activity corresponding to increased alkaloid levels suggest a role for this enzyme in the overall biosynthesis of pyrrolidine alkaloids.Polyamines and their biosynthetic enzymes ADC3 (EC 4.1.1.19) and ODC (EC 4.1.1.17) may play an important role in many aspects of plant development including growth, differentiation, senescence, and response to stress (7). However, relatively little is known about their role in secondary plant metabolism. Putrescine is a precursor not only of PAs (7), but also of parts of important alkaloids such as the pyrrolidine rings of tobacco alkaloids (nicotine and nomicotine), tropane alkaloids (hyoscyamine, hyoscine, and meteloidine), pyrrolizidine alkaloids (retronecine), and possibly phenanthroindolizidines (tylophorine) (10). The putrescine-derived PAs (spermidine, homospermidine, and spermine) may be conjugated to cinnamic acids or to fatty acids, giving rise to other more complex alkaloids (18).PAs are present in the plant cell in both free and conjugated forms (19,20 been correlated with the onset of reproduction (4) and virus resistance (12), but not with alkaloid biosynthesis.Several publications support the view that auxin levels are involved in the regulation of nicotine production by tobacco callus cultures (22) and root cultures (21) as well as in the intact tobacco plant (25). Recently, we found (23) that the alkaloid level increased dramatically when tobacco callus grown on 11.5 ,gM NAA (suboptimal for alkaloid biosynthesis) was transferred to a medium containing 1.5 ;tM NAA (optimal for alkaloid biosynthesis). In the present study, we have used this experimental approach to investigate the relation between PAs (free and conjugated) and pyrrolidine alkaloids in tissues where alkaloid biosynthesis is active. The activities of ODC and ADC in relation to pyrrolidine alkaloid formation were also investigated.MATERIALS AND METHODS P...

The CO uptake capacity of soils was studied in the field in order t o refine previous estimates of the potential of soil as a CO sink. Soils representative of most of the major vegetative regions of North America as well as roadside soils and soils under cultivation were exposed in situ t o atmospheres containing initial concentrations of ca. 100 ppm CO in the air. The CO uptake capacities of the soils ranged from 7.6 to 115 mg CO/h/m2, with the tropical soils showing the greatest activity and the desert soils the least. Soils under cuItivation were consistently less active than the same soils nearby under natural vegetation. Laboratory investigations indicate that the differences were probably not due to agricultural chemicals but rather t o a lack of organic matter in the tilled soils. Roadside soils were consistently higher in CO uptake capacity than similar soils in remote regions. Laboratory studies support the idea that this increased rate was due to the constant exposure of roadside soils t o high levels of CO. Data for the field studies was corrected for the influence of environmental variables based on laboratory studies and the potential capacity of the soils of the conterminous United States was estimated t o be an uptake of 505 million tons of CO per year. This capacity, more than twice the estimated anthropogenic CO in the U.S. annually, indicates that potentially soil is a major sink for atmospheric CO.

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