Sylwia Adamczyk

Influence of diterpenes (colophony and abietic acid) and a triterpene (beta-sitosterol) on net N mineralization, net nitrification, soil respiration, and microbial biomass in birch soil

The aim of this study was to examine the effect of common diterpenes (colophony, abietic acid) and triterpene (beta-sitosterol) on carbon (C) and nitrogen (N) transformations in soil under birch (Betula pendula L.). Samples were taken from the organic layer at two study sites, Kivalo (N-poor soil) and Kerimäki (N-rich soil), and incubated with the above-mentioned terpenes in laboratory conditions. Carbon dioxide evolution (C mineralization), net N mineralization, nitrification, and N and C in microbial biomass were measured. All these terpenes increased C mineralization, but decreased net N mineralization. The potential to decrease net N mineralization depended on amount of terpenes, with a stronger effect at a higher amount. Net nitrification in Kerimäki soil (N-rich soil) decreased but was not completely inhibited by terpenes. Effect of terpenes on soil microbial biomass C and N was not so clear, but they tended to increase both. Our study suggests that higher terpenes can act as a carbon source for soil microbial communities.

Tannins and Their Complex Interaction with Different Organic Nitrogen Compounds and Enzymes: Old Paradigms versus Recent Advances

Abstract Tannins, an abundant group of plant secondary compounds, raise interest in different fields of science, owing to their unique chemical characteristics. In chemical ecology, tannins play a crucial role in plant defense against pathogens, herbivores, and changing environmental conditions. In the food industry and in medicine, tannins are important because of their proven positive effect on human health and disease treatment. Such wide interests fueled studies on tannin chemistry, especially on their flagship ability to precipitate proteins. In this Review, we expand the basic knowledge on tannin chemistry to the newest insights from the field. We focus especially on tannin reactions with different non‐protein organic N compounds, as well as the complex interactions of tannins with enzymes, resulting in either an increase or decrease in enzyme activity.