Variation of soil organic matter depends on light-fraction organic matter under long-term monocropping of different crops

Cultivating crops influences soil organic matter (SOM), but the effect of different crops remains unclear, particularly under long-term monocropping. The objective of this study was to identify how different crops influence the content and chemical structures of SOM under long-term monocropping. Here, soils were sampled (0–20 cm) under 27-year soybean and maize monocropping and separated into different physical fractions. The content and chemical structures of SOM in all fractions were determined. SOM contents were higher under soybean than maize in bulk soil and macroaggregates and their light-fractions instead of microaggregates and silt and clay. The difference in SOM chemical structure was observed in aggregates and density fractions rather than bulk soils and supported by the result of principal component analysis. The proportion of O-alkyl C in macro- and microaggregates and all free light fractions and that of aromatic C in mineral-associated fractions were higher, while that of carbonyl C was lower under maize than soybean. These results demonstrated that different crops monocropping influences the content and chemical structures of SOM, and the variations were mainly in the light-fraction SOM and highlight a higher sensitivity of physical fractions than bulk soil to different crops.

Recycling Potential for Non-Valorized Plastic Fractions from Electrical and Electronic Waste

This paper describes a study for waste of electrical and electronic equipment (WEEE) to characterise the plastic composition of different mixed plastic fractions. Most of the samples studied are currently excluded from material recycling and arise as side streams in state-of-the-art plastics recycling plants. These samples contain brominated flame retardants (BFR) or other substances of concern listed as persistent organic pollutants or in the RoHS directive. Seventeen samples, including cathode ray tube (CRT) monitors, CRT televisions, flat screens such as liquid crystal displays, small domestic appliances, and information and communication technology, were investigated using density- and dissolution-based separation processes. The total bromine and chlorine contents of the samples were determined by X-ray fluorescence spectroscopy, indicating a substantial concentration of both elements in density fractions above 1.1 g/cm3, most significantly in specific solubility classes referring to ABS and PS. This was further supported by specific flame retardant analysis. It was shown that BFR levels of both polymers can be reduced to levels below 1000 ppm by dissolution and precipitation processes enabling material recycling in compliance with current legislation. As additional target polymers PC and PC-ABS were also recycled by dissolution but did not require an elimination of BFR. Finally, physicochemical investigations of recycled materials as gel permeation chromatography, melt flow rate, and differential scanning calorimetry suggest a high purity and indicate no degradation of the technical properties of the recycled polymers.

Ciliary Ca2+ pumps regulate intraciliary Ca2+ from the action potential and may co-localize with ciliary voltage-gated Ca2+ channels

ABSTRACT Calcium ions (Ca2+) entering cilia through the ciliary voltage-gated calcium channels (CaV) during the action potential causes reversal of the ciliary power stroke and backward swimming in Paramecium tetraurelia. How calcium is returned to the resting level is not yet clear. Our focus is on calcium pumps as a possible mechanism. There are 23 P. tetraurelia genes for calcium pumps that are members of the family of plasma membrane Ca2+ ATPases (PMCAs). They have domains homologous to those found in mammalian PMCAs. Of the 13 pump proteins previously identified in cilia, ptPMCA2a and ptPMCA2b are most abundant in the cilia. We used RNAi to examine which PMCA might be involved in regulating intraciliary Ca2+ after the action potential. RNAi for only ptPMCA2a and ptPMCA2b causes cells to significantly prolong their backward swimming, which indicates that Ca2+ extrusion in the cilia is impaired when these PMCAs are depleted. We used immunoprecipitations (IP) to find that ptPMCA2a and ptPMCA2b are co-immunoprecipitated with the CaV channel α1 subunits that are found only in the cilia. We used iodixanol (OptiPrep) density gradients to show that ptPMCA2a and ptPMCA2b and CaV1c are found in the same density fractions. These results suggest that ptPMCA2a and ptPMCA2b are located in the proximity of ciliary CaV channels.

Changes in the hydrophobic-hydrophilic properties of the organic matter of the chernozems of the Kamennaya Steppe

Soil samples and physical size-density fractions isolated from them (silt particle size less than 1 µm, light fraction (LF) with a density of less than 2 g/cm3 and a fraction of the residue) of ordinary chernozem were studied in three contrasting variants of the experimental fields of the Kamennaya Steppe agrolandscape of the Voronezh region: mowed steppe, long-term permanent bare fallow and permanent corn – the main differences of which are in tillage (cultivated and not cultivated lands) and in the supply/absence of plant residues and root secretions. The LF content changes in the series: “mowed steppe” > “permanent corn” > “permanent bare fallow”, which corresponds to the direction of changes in the total carbon content of the soil and a decrease in the value of the contact angle of wetting (CA) of the surface of the solid phase of the studied chernozems. The determination of the total C and N content revealed the change in the qualitative and quantitative composition of the size-density fractions for different land use cases. Chromatographic fractionation of alkaline extractions of humus substances (HS) of chernozem samples and size-density fractions revealed an increase in the degree of hydrophilicity of HS while simultaneously increasing the hydrophobicity of the solid phase surface and the carbon content in the soil. HS of LF of the “mowed steppe” turned out to be by 63% more hydrophilic than HS of LF of “permanent bare fallow” and by 47% more hydrophilic than HS of LF of “permanent corn”. While the hydrophilicity of the HS silt differed by 16 and 27%, respectively. The hydrophilicity of the HS of the original soil in the plot of the “mowed steppe” was by 41% higher than the hydrophilicity of the HS in the soil in the plot of “permanent bare fallow” and by 24% higher than in the soil of the plot of “permanent corn”. In addition, changes in the hydrophilicity of HS of size-density fractions are more intense than the HS of the soil, so the change in the degree of hydrophilicity of HS of size-density fractions is an indicator of soil degradation under different agrogenic pressue.

Deciphering the Proteotoxic Stress Responses Triggered by the Perturbed Thylakoid Proteostasis in Arabidopsis

Here, we explored heat dependent thylakoid FtsH protease substrates and investigated proteotoxicity induced by thermal damage and processive protease dysfunction on the thylakoid membrane. Through our thylakoid enriched proteome analysis and biochemical experiments, carbonylated stromal proteins were suggested as possible FtsH targets. Furthermore, we observed in the thylakoid fractions in the absence of FtsH stromal reactive oxygen species-detoxifying enzymes, as well as heat shock proteins and chaperones, which are known to be upregulated at the transcriptional level when this protease is absent, which is called the damaged protein response, resembling unfolded protein response in eukaryotic cells. Interestingly, the thylakoid-enriched high-density fractions included stromal translation factors and RNA-binding proteins, along with aminoacyl-tRNA synthetase, reminiscent of the formation of stress granules. Unexpectedly, extraplastid proteins such as mitochondrial chaperones, peroxidase, tricarboxylic acid cycle and respiratory chain enzymes, as well as cytosolic ribosomes, translation factors, heat shock proteins, antioxidants and metabolic enzymes, were also found deposited in the high-density fractions depending on the loss of thylakoid FtsH, with more prominent effects of thermal stress on the cytosolic proteins. This may reflect intracellular adaptation to the proteotoxic influences from the organelle.