Yield formation of five crop species under water shortage and differential potassium supply

A long‐term field experiment on a Haplic Phaeozem, established 1949 with four levels of potassium (K) supply (5, 69, 133, and 261 kg K ha^?1), was analyzed for the interaction between K supply and yield loss of five crop species by water shortage. The crop species were cultivated simultaneously side‐by‐side in the following rotation: potato (Solanum tuberosum L.), silage maize (Zea mays L.), spring wheat (Triticum aestivum L.), beet (Beta vulgaris L.), and spring barley (Hordeum vulgare L.). The treatment with 133 kg K ha^?1 supply had a nearly balanced K budget. In the treatments with lower supply, the soil delivered K from its mineral constituents. On the low‐K plots (especially on those with only 5 kg K ha^?1), crops suffered yield depressions of nearly all main harvest products (cereal grains, potato tubers, beet storage roots, silage maize) and by‐products (straw, beet leaves) by up to 40.7% of dry matter. Only wheat grains were an exception. Potassium concentrations in the harvested plant parts decreased nearly in parallel to the reduction of their dry matter yields, with the exception of cereal grains, which kept stable concentrations even in the treatment with only 5 kg K ha^?1. A comparison of four year‐pairs with differing levels of precipitation in yield‐relevant periods showed an average water shortage‐induced depression of dry matter yields by 19.7% in the main harvest products. The severity of this yield depression was not mitigated by elevated K supply, with the exception of beet leaves, where the dry matter production was stabilized by high K supply. In this crop, the reduction of storage‐root yield was associated with a decrease in harvest index and was therefore obviously caused by an inhibition of assimilate translocation from the leaves into these organs, in contrast to cereals, where water shortage primarily affected dry matter production in vegetative organs. It is concluded that the physiological causes of yield reduction by drought stress and the possibility of its amelioration by K supply differ between plant species and organs.     

Determination of Potassium Delivery to the Roots of Cereal Plants

Potassium (K) delivery to the roots of cereal plants in soils is determined by both soil and plant factors, root growth and root length density in particular, being of major importance. In Part A of this paper an evaluative framework is shown for sandy and loamy-silty soils for determination of root length density based on available field capacity, soil depth in 10 cm steps and the climatic water balance. A good correlation (r² = 0.86) was found when the root length densities were determined at ear emergence. With the help of correction functions root length densities can be subsequently estimated for the other phenological stages (stem elongation, flowering and yellow ripeness). The method described is suited for determining root length densities in water and nutrient transport simulation models. In Part B exchange resins were used to simulate the K delivery from the soil to the root. Measurements were made for different soils and water contents. The depletion zone near the exchange resin was 6 mm thick after 4 days. This corresponds to results obtained from root measurements. Comparisons between a sandy and a loamy-silty soil show, that K delivery by diffusion for equal concentrations depends primarily on soil moisture and pore tortuosity. This leads to the conclusion, that soil physical properties must be taken into consideration when evaluating chemical soil analysis and recommendating fertilizer applications.     

Seasonal variations in location and population structure of endophytes in buds of Scots pine

We studied the location and distribution of a bacterial isolate, a Mycobacterium sp., in buds of Scots pine (Pinus sylvestris L.). Using a probe specific for the 16S rRNA of the Mycobacterium sp., the bacterium was found by in situ hybridization in the meristematic tissues of 40% of all bud samples examined. Because we had previously found other bacterial and fungal endophytes in the meristematic tissues of Scots pine buds, we studied their occurrence in buds during shoot development and dormancy. Using probes targeted to the 16S or 18S rRNA of the endophytes Mycobacterium sp., Methylobacterium spp., Pseudomonas spp. and Rhodotorula minuta, endophytes were found in association with growing tissues, with Methylobacterium spp. being the dominant species. Endophytes were detected in abundance before elongation or differentiation of a bud, but once a tissue was fully developed, endophytes were no longer detected. Metabolic activity of the endophytes was suppressed at the onset of, and during, dormancy of Scots pine, but recovered before the following growing season.     

Apple polyphenols and products formed in the gut differently inhibit survival of human cell lines derived from colon adenoma (LT97) and carcinoma (HT29)

Colorectal tumor risks could be reduced by polyphenol-rich diets that inhibit cell growth. Here, apple polyphenols were studied for effects on the survival of colon adenoma (LT97) and carcinoma-derived (HT29) cell lines. Three apple extracts (AEs) from harvest years 2002-2004 were isolated (AE02, AE03, and AE04) and fermented in vitro with human fecal flora. Extracts and fermentation products were analyzed for polyphenols with HPLC. The cells were treated with AEs (0-850 microg/mL) or fermented AEs (F-AEs, 0-9%), and survival was measured by DNA staining. All AEs contained high amounts of polyphenols (311-534 mg/g) and reduced cell survival (in LT97 > HT29). AE03 was most potent, possibly because it contained more quercetin compounds. Fermentation of AEs resulted in an increase of short chain fatty acids, and polyphenols were degraded. The F-AEs were approximately 3-fold less bioactive than the corresponding AEs, pointing to a loss of chemoprotective properties through fermentation.     

Bacterial taxa that limit sulfur flux from the ocean

Flux of dimethylsulfide (DMS) from ocean surface waters is the predominant natural source of sulfur to the atmosphere and influences climate by aerosol formation. Marine bacterioplankton regulate sulfur flux by converting the precursor dimethylsulfoniopropionate (DMSP) either to DMS or to sulfur compounds that are not climatically active. Through the discovery of a glycine cleavage T-family protein with DMSP methyltransferase activity, marine bacterioplankton in the Roseobacter and SAR11 taxa were identified as primary mediators of DMSP demethylation to methylmercaptopropionate. One-third of surface ocean bacteria harbor a DMSP demethylase homolog and thereby route a substantial fraction of global marine primary production away from DMS formation and into the marine microbial food web.     

Perfluorooctanoate (PFO) in Forest Soils near a Fluoropolymer Manufacturing Facility

After elevated concentrations of perfluorooctanoate (PFO) were found in river and groundwater in the vicinity of a fluoropolymer manufacturing facility, numerous soils at adjacent sites were sampled in 2007. Within a 5-km northeast-oriented sector around a probable point source, 20 forest sites were investigated and compared to deposition and groundwater data. PFO concentrations up to 600 µg/kg were detected in the soils, and PFO concentrations typically decreased toward deeper soil depths. In mixed or deciduous forests, maximum concentrations of PFO occurred in the topsoil, pointing to the favorable decomposition and incorporation of deciduous litter. PFO concentrations of the organic layer over the 20 sampling sites were interpolated using ordinary kriging. Highest PFO content in the organic layer was located about 500 m away from the point source in the regional wind direction, decreasing asymptotically outwards. Long-term monitoring data pointed to an accumulation of PFO over time in the organic layer. The data suggest that PFO might be released in the course of litter decomposition and transported toward deeper soil regions only gradually. The soils’ PFO concentrations reflect the deposition data. The transport link toward groundwater is currently established in lysimeter studies.     

Urine excretion of pentachlorophenol (PCP) in occupational exposure

The pharmacokinetics of pentachlorophenol (PCP) excretion in urine was examined in four workers exposed to the biocide in the tannery and wood industries. PCP concentration in urine was significantly higher in morning samples than in afternoon or evening samples. This excretion pattern was observed during an exposure of several shifts and following a four-week holiday period. The estimated half-life for PCP urine excretion was 10 days. Biological monitoring of occupational exposure to PCP should be carried out by measuring the concentration of the compound in urine collected in the morning or before the workshift.     

The dual role of wild phages for horizontal gene transfer among Salmonella strains

Salmonella bacteriophages seem to mediate horizontal transfer of virulence functions among Salmonella strains in two different ways: by general transduction and also by lysogenic conversion. The majority of wild phages isolated from Salmonella strains belong to the P22 like phages and were able to transduce. Our data show that the lysogenic conversion is generally accompanied by changes in the susceptibility to the typing phages used for epidemiological purposes. Similar phage type conversions to S. Typhimurium DT104 could be detected upon lysogenization with two other S. Typhimurium strains. For some S. Typhimurium strains the typical phage pattern is actually associated with alterations of virulence characteristics. For example, all tested wild type isolates of phage types DT49 and DT204 were found to be SopE phi-lysogens. The Anderson typing phages interfere with the prophages and/or cryptic phages and so the complex genetic short-term evolution can be demonstrated in the lab. This is one reason for the successful application of phage typing in Salmonella epidemiology since the 50s.