Browsing by Subject "tannins"
Now showing items 1-4 of 4
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(2020)To understand the positional and temporal defense mechanisms of coniferous tree bark at the tissue and cellular levels, the phloem topochemistry and structural properties were examined after artificially induced bark defense reactions. Wounding and fungal inoculation withEndoconidiophora polonicaof spruce bark were carried out, and phloem tissues were frequently collected to follow the temporal and spatial progress of chemical and structural responses. The changes in (+)-catechin, (-)-epicatechin, stilbene glucoside, and resin acid distribution, and accumulation patterns within the phloem, were mapped using time-of-flight secondary ion mass spectrometry (cryo-ToF-SIMS), alongside detailed structural (LM, TEM, SEM) and quantitative chemical microanalyses of the tissues. Our results show that axial phloem parenchyma cells of Norway spruce contain (+)-catechins, the amount of which locally increases in response to fungal inoculation. The preformed, constitutive distribution and accumulation patterns of (+)-catechins closely follow those of stilbene glucosides. Phloem phenolics are not translocated but form a layered defense barrier with oleoresin compounds in response to pathogen attack. Our results suggest that axial phloem parenchyma cells are the primary location for (+)-catechin storage and synthesis in Norway spruce phloem. Chemical mapping of bark defensive metabolites by cryo-ToF-SIMS, in addition to structural and chemical microanalyses of the defense reactions, can provide novel information on the local amplitudes and localizations of chemical and structural defense mechanisms and pathogen-host interactions of trees.
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(2020)Abstract Organic matter decomposition plays a major role in the cycling of carbon (C) and nutrients in terrestrial ecosystems across the globe. Climate change accelerates the decomposition rate to potentially increase the release of greenhouse gases and further enhance global warming in the future. However, fractions of organic matter vary in turnover times and parts are stabilized in soils for longer time periods (C sequestration). Overall, a better understanding of the mechanisms underlying C sequestration is needed for the development of effective mitigation policies to reduce land-based production of greenhouse gases. Known mechanisms of C sequestration include the recalcitrance of C input, interactions with soil minerals, aggregate formation, as well as its regulation via abiotic factors. In this Minireview, we discuss the mechanisms behind C sequestration including the recently emerging significance of biochemical interactions between organic matter inputs that lead to C stabilization.
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(2018)Processes underlying soil organic matter (SOM) transformations are meeting growing interest as SOM contains more carbon (C) than global vegetation and the atmosphere combined. Therefore, SOM is a crucial element of the C cycle, especially in ecosystems rich in organic matter, such as boreal forests. However, climate change may shift the fate of this SOM from C sink into C source, accelerating global warming. These processes require a better understanding of the involved mechanisms driving both the C cycle and the interlinked nitrogen (N) cycle. SOM transformations are balanced by a network of interactions between biological, chemical and physical factors. In this review, we discuss the findings of the most recent studies to the current state of knowledge about the main drivers in SOM transformations. We focus on plant-derived secondary metabolites, as their biochemical traits, especially interactions with soil microbial communities, organic N compounds and enzymes make them potential regulators of SOM decomposition. However, these regulatory abilities of plant-derived compounds are not fully explored.
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(Helsingfors universitet, 2017)The aim of this thesis was to study how the origin and treatment histories of spruce (Picea abies) and pine (Pinus radiata, Pinus sylvestris) bark influence on the extraction yield of tannin. The bark is produced in large quantities during the debarking process and is considered as waste in traditional forest industry. Bark is mainly used for energy production. In comparison to wood tissue, bark contains more extractives that could have potential for various applications in pharmaceutical industry or bio-based adhesives. Stilbenes, lignans, flavonoids and tannins are typical extractives in wood bark. In this Master’s thesis, the focus is on the extraction of tannins. Bark raw materials were obtained from pulp mills and sawmills. Bark samples were processed as air-dried (drying < 50 °C) or fresh as it is after debarking. Samples were extracted in rotating air bath reactors at 90 °C and 10 % consistency. Eight batches were hot water extracted and five different time points were studied: 40, 60, 80, 100 and 120 minutes. The extracts were analyzed with three UV-spectrophotometric methods: Folin-Ciocalteu assay, UV-280 nm method and Acid-Butanol assay. UV-280 nm method was used in tannin yield calculations. Tannin yield was the highest from air-dried spruce bark from sawmill (5.63 % from original dry bark). The second highest tannin yield (3.33 %) was from air-dried sawmill pine (Pinus radiata) bark extract. Fresh sawmill spruce and pine bark extraction gave 2.59 % and 2.65 % for tannin yield, respectively. The poorest yields came from the pulp mill bark samples. Yields from fresh and air-dried pulp mill spruce barks were 0.41 % and 0.97 %, respectively. In comparison, the tannin yields from fresh and air-dried pulp mill pine (Scots pine) bark were 1.13 % and 1.20 %. Results showed that the tannin yield increased when the extraction time increased. Statistical analysis confirmed that the origin and the treatment have a significant influence on the extraction yield of tannin. The reason for the differences in the extraction yields between barks with different origins are probably related to the different debarking methods. Sawmill bark samples gave a significantly higher tannin yield than samples from pulp mill. In sawmills, logs are debarked as dry in rotary debarker. Drum debarkers are typically being used in pulp and paper mills where water is used in debarking process. Contact with water may leach water-soluble tannins from bark. This is in accordance with the results that bark from sawmill was found to be an optimal raw material for hot water extraction. Further research should focus on optimizing hot water extraction conditions eg. by applications of chemicals.
