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B N Smith

Publications and source records attributed to B N Smith.

48 records · Page 3Linked to original sources
PubMed1971

Two categories of c/c ratios for higher plants.

(13)C/(12)C ratios have been determined for plant tissue from 104 species representing 60 families. Higher plants fall into two categories, those with low delta(PDBI) (13)C values (-24 to -34 per thousand) and those with high delta (13)C values (-6 to -19 per thousand). Algae have delta (13)C values of -12 to -23 per thousand. Photosynthetic fractionation leading to such values is discussed.

Journal Article↗
PubMed1970

The prevalence of carbon-13 in respiratory carbon dioxide as an indicator of the types of endogenous substrate. The change from lipid to carbohydrate during the respiratory rise in potato slices.

Isotope discrimination is a common feature of biosynthesis in nature, with the result that different classes of carbon compounds frequently display different (13)C/(12)C ratios. The (13)C/(12)C ratio of lipid in potato tuber tissue is considerably lower than that for starch or protein. We have collected respiratory CO(2) from potato discs in successive periods through 24 hr from the time of cutting-an interval in which the respiration rate rises 3-5-fold. The (13)C/(12)C ratio of the evolved CO(2) was determined for each period, and compared with the (13)C/(12)C ratios of the major tissue metabolites. In the first hours the carbon isotope ratio of the CO(2) matches that of lipid. With time, the ratio approaches that typical of starch or protein. An estimation has been made of the contribution of lipid and carbohydrate to the total respiration at each juncture. In connection with additional observations, it was deduced that the basal, or initial, respiration represents lipid metabolism-possibly the alpha-oxidation of long chain fatty acids-while the developed repiration represents conventional tricarboxylic acid cycle oxidation of the products of carbohydrate glycolysis. The true isotopic composition of the respiratory CO(2) may be obscured by fractionation attending the refixation of CO(2) during respiration, and by CO(2) arising from dissolved CO(2) and bicarbonate preexisting in the tuber. Means are described for coping with both pitfalls.

Aging↗
PubMed1970

Biogeochemistry of the stable isotopes of hydrogen and carbon in salt marsh biota.

Deuterium to hydrogen ratios of 14 plant species from a salt marsh and lagoon were 55 per thousand depleted in deuterium relative to the environmental water. Carbon tetrachloride-extractable material from these plants was another 92 per thousand depleted in deuterium. This gave a fractionation factor from water to CCl(4) extract of 1.147. This over-all fractionation was remarkably constant for all species analyzed. Plants also discriminate against (13)C, particularly in the lipid fraction. Data suggest that different mechanisms for carbon fixation result in different fractionations of the carbon isotopes. Herbivore tissues reflected the isotopic ratios of plants ingested. Apparently different metabolic processes are responsible for the different degrees of fractionation observed for hydrogen and carbon isotopes.

Journal Article↗
PubMed1966

Production of volatile amines and skatole at anthesis in some arum lily species.

The odoriferous compounds produced at the time of flowering by the inflorescences of 5 arum lily species were condensed in dry ice traps. The components of the condensates were separated by paper chromatography and identified on the basis of position and color reactions in comparison with known compounds. The concentration of free amino acids in the appendix of Sauromatum guttatum Schott increased 20-fold during flowering.

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