Sándor T. Forczek

Trichloroacetic acid in Norway spruce/soil-system I. Biodegradation in soil

Trichloroacetic acid (TCA) as a phytotoxic substance affects health status of coniferous trees. It is known as a secondary air pollutant (formed by photooxidation of tetrachloroethene and 1,1,1-trichloroethane) and as a product of chlorination of humic substances in soil. Its break-down in soil, however, influences considerably the TCA level, i.e. the extent of TCA uptake by spruce roots. In connection with our investigations of TCA effects on Norway spruce, microbial processes in soil were studied using 14C-labeling. It was shown that TCA degradation in soil is a fast process depending on TCA concentration, soil properties, humidity and temperature. As a result, the TCA level in soil is determined by a steady state between uptake from the atmosphere, formation in soil, leaching and degradation. The process of TCA degradation in soil thus participates significantly in the chlorine cycle in forest ecosystems.

Biodegradation of Trichloroacetic Acid in Norway Spruce/Soil System

Trichloroacetic acid (TCA) belongs to secondary atmospheric pollutants affecting the forest health. Distribution of [1,2-14C]TCA-residues and TCA biodegradation were investigated in 4-year-old nursery-grown trees of Norway spruce [Picea abies (L.) Karst.] in the whole plant/soil system. Radioactivity was monitored in needles, wood, roots and soil as well as in the air. During two weeks of exposure TCA was continuously degraded, especially in the soil. Estimates of radioactivity balance showed loss of radioactivity into the atmosphere in the form of 14CO2; unincorporated [1,2-14C]TCA, chloroform, carbon monoxide and methane were not detected at all. TCA degradation to CO2 was indicated also in the spruce needles. Moreover, it was found that soil litter contained [1,2-14C]TCA unavailable to microorganisms.

N‐acyl‐homoserine lactone uptake and systemic transport in barley rest upon active parts of the plant

Bacteria communicate with each other in a population density-dependent process known as quorum sensing. N-acyl-homoserine lactones (HSLs) are the autoinducers of Gram-negative bacteria and the best-studied quorum sensing signals so far. HSLs induce various responses in plants, including systemic resistance and root development. Here, we used different methods, including tritium labelling, sensor strain assays and monoclonal antibodies (mAbs), to analyse the uptake and translocation of C8- and C10- homoserine lactones into barley (Hordeum vulgare cv Barke). Both HSLs were already systemically transported into the shoot at 2 h after application. HSL uptake could be inhibited by orthovanadate, demonstrating that ABC transporters are involved in the uptake. Root transport occurs predominantly via the central cylinder, which was shown by transport inhibition via KCl application and autoradiography of root cross-sections. Furthermore, a newly established detection method with mAbs allowed the first detection of a systemic transport of long-chain HSLs in plants. The coupled use of different HSL detection methods demonstrated that the uptake and transport of HSLs into barley does not occur passively, but relies, at least partially, on active processes in the plant.

Uptake, translocation and fate of trichloroacetic acid in a Norway spruce/soil system

Trichloroacetic acid (TCA) is a secondary atmospheric pollutant formed by photooxidation of chlorinated solvents in the troposphere--it has, however, recently been ranked among natural organohalogens. Its herbicidal properties might be one of the factors adversely affecting forest health. TCA accumulates rapidly in conifer needles and influences the detoxification capacity in the trees. The aim of the investigations--a survey of which is briefly given here--was to elucidate the uptake, distribution and fate of TCA in Norway spruce. For this purpose young nursery-grown plants of Norway spruce (Picea abies (L.) Karst.) were exposed to [1,2-14C]TCA and the fate of the compound was followed in needles, wood, roots, soil and air with appropriate radio-indicator methods. As shown by radioactivity monitoring, the uptake of TCA from soil by roots proceeded most rapidly into current needles at the beginning of the TCA treatment and was redistributed at later dates so that TCA content in older needles increased. The only product of TCA metabolism/biodegradation found in the plant/soil-system was CO(2) (and corresponding assimilates). TCA biodegradation in soil depends on TCA concentration, soil humidity and other factors.

Microbiological aspects of determination of trichloroacetic acid in soil.

Soils have been shown to possess a strong microbial trichloroacetic acid (TCA)-degrading activity. High TCA-degradation rate was also observed during soil extraction with water. For correct measurements of TCA levels in soil all TCA-degrading activities have to be inhibited immediately after sampling before analysis. We used rapid freezing of soil samples (optimally in liquid nitrogen) with subsequent storage and slow thawing before analysis as an efficient technique for suppressing the degradation. Frozen soil samples stored overnight at −20 °C and then thawed slowly exhibited very low residual TCA-degrading activity for several hours. Omitting the above procedure could lead to the confusing differences between the TCA levels previously reported in the literature.

Emission of climate relevant volatile organochlorines by plants occurring in temperate forests.

Chlorine, one of the most abundant elements in nature, undergoes a complex biogeochemical cycle in the environment, involved in the formation of volatile organochlorines (VOCls), which in turn can contribute to environmental problems, contaminate natural ecosystems, and are of public health concern. Several industrial and natural sources of VOCls have already been identified; however, data - particularly on the natural sources - are still scarce. The aim of this study was to investigate the diversity of emission of VOCls from soil and several undergrowth plants collected in temperate spruce forest ecosystem and the effect of salting on the VOCl emission of plants. Undergrowth plants were found to emit chloroform (CHCl 3 ) in the range of 2.2-201 pmol/day/g dry weight (DW), tetra-chloromethane (CCl 4 ) 0-23.5 pmol/day/g DW, and tetrachloroethene (C 2 Cl 4 ) 0-13.5 pmol/day/g DW; the average emission rates were about 10 times higher than that of soil (2.9-47.2; 0-5.8; 0-3.6 pmol/day/g DW of CHCl 3 ; CCl 4 ; C 2 Cl 4 emission, respectively). Addition of sodium chloride solution in most cases caused an increase in the emission of CHCl 3 and caused a species specific - effect on the emissions of CCl 4 and C 2 Cl 4 . The results suggest that the emission of VOCls from spruce forest contribute to the atmospheric input of reactive chlorine; however, on a global scale it is only a minor net source.

Trichloroacetic acid of different origin in Norway spruce needles and chloroplasts

Trichloroacetic acid (TCA), a secondary atmospheric pollutant, is also formed in forest soil and thus ranked among natural organohalogens. The observed biooxidation of atmospheric tetrachloroethene (PER) to TCA in chloroplasts has led to the investigation of the mode of action of TCA in spruce needles, since TCA is also accumulated in the needles after its rapid uptake from soil by roots. Being phytotoxic, TCA considerably influences conifers by affecting their photosynthetic apparatus. We examined the transport of TCA from soil into chloroplasts in order to compare the effects of TCA on conifers from both sources, i.e. endogenously produced within chloroplasts or taken up by roots. The influence of TCA formed in chloroplasts was found to be much more adverse than that of “soil” TCA.

Autoradiography of 3H-pirenzepine and 3H-AFDX-384 in Mouse Brain Regions: Possible Insights into M1, M2, and M4 Muscarinic Receptors Distribution

Autoradiography helps to determine the distribution and density of muscarinic receptor (MR) binding sites in the brain. However, it relies on the selectivity of radioligands toward their target. 3H-Pirenzepine is commonly believed to label predominantly M1MR, 3H-AFDX-384 is considered as M2MR selective ligand. Here we performed series of autoradiographies with 3H-AFDX-384 (2 nM), and 3H-pirenzepine (5 nM) in WT, M1KO, M2KO, and M4KO mice to address the ligand selectivity. Labeling with 3H-pirenzepine using M1KO, M2KO, and M4KO brain sections showed the high selectivity toward M1MR. Selectivity of 3H-AFDX-384 toward M2MR varies among brain regions and depends on individual MR subtype proportion. All binding sites in the medulla oblongata and pons, correspond to M2MR. In caudate putamen, nucleus accumbens and olfactory tubercle, 77.7, 74.2, and 74.6% of 3H-AFDX-384 binding sites, respectively, are represented by M4MR and M2MR constitute only a minor portion. In cortex and hippocampus, 3H-AFDX-384 labels almost similar amounts of M2MR and M4MR alongside significant amounts of non-M2/non-M4MR. In cortex, the proportion of 3H-AFDX-384 binding sites attributable to M2MR can be increased by blocking M4MR with MT3 toxin without affecting non-M4MR. PD102807, which is considered as a highly selective M4MR antagonist failed to improve the discrimination of M2MR. Autoradiography with 3H-QNB showed genotype specific loss of binding sites. In conclusion: while 3H-pirenzepine showed the high selectivity toward M1MR, 3H-AFDX-384 binding sites represent different populations of MR subtypes in a brain-region-specific manner. This finding has to be taken into account when interpreting the binding data.

The deletion of M4 muscarinic receptors increases motor activity in females in the dark phase

M4 muscarinic receptors (MR) presumably play a role in motor coordination. Previous studies have shown different results depending on genetic background and number of backcrosses. However, no attention has been given to biorhythms.