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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Biology and fertility of soils 22 (1996), S. 318-325 
    ISSN: 1432-0789
    Keywords: Autotrophs ; Liming ; Nitrapyrin ; N-serve ; Nitrification ; N2O ; Sodium chlorate ; Acid beech forest soil
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract An acid forest soil from beech forest gaps, which were either limed or unlimed, and the undisturbed forest was investigated for the type of nitrifying populations and the process of N2O evolution. To see whether nitrifiers were of heterotrophic or autotrophic origin, the nitrification inhibitors nitrapyrin and sodium chlorate were applied to disturbed soil samples which underwent laboratory incubations. Nitrapyrin inhibits autotrophic nitrification. In different studies, sodium chlorate has been identified as an inhibitor either of autotrophic or of heterotrophic nitrification. In the samples investigated only nitrapyrin inhibited the autotrophic nitrification occurring in the limed soil. Sodium chlorate effectively inhibited heterotrophic nitrification. In the limed forest floor samples, where most autotrophic nitrification occured, sodium chlorate showed no inhibitory effect. In another laboratory incubation experiment, N2O evolution from undisturbed soil columns, to which the above inhibitors were applied, was investigated. In those samples, in which nitrification had been reduced, neither inhibitor significantly reduced N2O evolution. Thus it was concluded that the contribution of nitrification to N2O losses is negligible, and that N2O evolution arises from the activity of denitrifying organisms. Microbial biomass and respiration measurements showed that the inhibitors did not affect microflora negatively.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-0878
    Keywords: Baboon pineal gland ; Microtubules ; Synaptic ribbons ; Circadian rhythm
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary In baboons kept under controlled lighting conditions, microtubules (MT) are readily seen in the perikaryal cytoplasm and in the perivascular processes of pinealocytes. A significant increase in the number of MT, single synaptic ribbons (SR) and the formation of synaptic ribbon fields (RF, i.e. organelles which consist of multiple dense rodlets or plates, and vesicles), occur during the dark phase of a circadian light-dark cycle. MT may act as “tracks” for the oriented flow of vesicles derived from the smooth endoplasmic reticulum, to cytoplasmic sites where RF are being formed. The origin of the dense rodlets of RF remains unknown. Structural differences between SR and RF indicate that the latter organelles are not directly involved in impulse propagation between adjacent baboon pinealocytes. RF may function as storage organelles for some of the pineal secretory products which are formed in large amounts during the dark phase.
    Type of Medium: Electronic Resource
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