Electron diffraction and imaging of uncompressed monolayers of amphiphilic molecules on vitreous and hexagonal ice

A new approach is described for probing domains of ordered self-assemblies of amphiphilic monolayers at the aqueous solution interface. The method has potential importance for the study of membrane structure, Langmuir-Blodgett films, and nucleation processes of two-and three-dimensional crystals. Electron diffraction (ED) patterns indicative of two-dimensional crystalline self-assembly were obtained from samples, which were examined by cryo-electron microscopy, of monolayers of water-insoluble amphiphiles on vitrified aqueour substrates. The apparent hexagonal symmetry of an ED pattern from a C(16)H(33)OH monolayer was interpreted in terms of multiple twinning. Monolayers of the CL(31)H(63)OH and cadmium salt of C(19)H(39)CO(2)H that were studied by dark-field techniques displayed faceted two-dimensional crystallites with a maximal size of 1 to 2 micrometers. Epitaxial nucleation of hexagonal ice by the C(31)H(63)OH monolayer has also been demonstrated by ED.     

Stomatal uptake of mineral particles from a sprayed suspension containing an organosilicone surfactant

Suspensions of insoluble particles are available on the market for foliar fertilizers. The question whether uptake of particles into the leaf interior is possible is under debate. The present study examines stomatal uptake of mineral particles into leaves of Avena sativa after spraying an aqueous suspension of calcium carbonate particles. By choosing a plant species with large stomata, confirming wide open stomata at the time of spraying and using a “super spreading” organosilicone surfactant, conditions were optimized for stomatal uptake. Scanning electron microscopical (SEM) examination confirmed particles in the intercellular spaces mostly in the vicinity of stomata. The number and size of particles was larger if leaves were treated with wide open than with closed stomata. The chemical identity of the particles was examined with electron‐dispersive x‐ray spectrography (EDX), confirming the presence of calcium carbonate particles among other particles of unknown origin. In conclusion, this study provides evidence for surfactant‐assisted stomatal uptake of mineral particles from sprayed suspensions in species with large stomata under specific conditions favoring stomatal uptake.     

a new high-pressure squeezing technique for pore fluid extraction from terrestrial soils

A core consisting of minerogenic peat and organic-rich mineral sediments was collected at an altitude of 4275 m in the Ovejuyo valley, 100 km NE of La Paz in Bolivia. Age dating with 210Pb showed that the core represents approximately three centuries of sediment accumulation. None of the peats are ombrotrophic. Despite this, the Cd/Al, Cu/Al, Zn/Al, and Pb/Al ratios are all significantly higher in the surface layers, particularly in the top 6 cm: natural, abiological geochemical processes, therefore, cannot account for these elevated heavy metal/Al ratios. There are two possible explanations for the metal enrichments, relative to Al, in the surface layers: bioaccumulation by living plants, and anthropogenic atmospheric metal deposition. While the living plant layer may be responsible for the Cd, Cu, and Zn enrichments, this is an unlikely explanation for the Pb profile. In contrast to the other metals, the concentration of Pb in the first sample (dating from 1985-1994) is less than that of the second sample (dating from 1970-1985). The Pb/Al profile is consistent with the well documented, rapid increase in atmospheric Pb emissions during the present century (which accelerated following the introduction of leaded gasoline), and the decline in Pb pollution during the past 20 years (as a result of the introduction of unleaded gasoline). Thus, the Ovejuyo Valley mire has provided one of the first records of atmospheric Pb pollution in South America.     

In vitro determination of the allergenic potential of technologically altered hen's egg

Hen's egg allergy represents one of the most common and severe IgE-mediated reactions to food in infants and young children. It persists, however, in many cases also lifelong. Therefore, the aim of this study was the detailed analysis of a technological process used to reduce the allergenic potential of hen's egg. The investigation focused on the pasteurized egg as starting material, intermediate, and final products of a nine-step manufacturing process performed for use of eggs in convenience products appropriate for allergic individuals. The steps consisted of a combination of various heat treatments and enzymatic hydrolyses. The alterations were controlled by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), immunoblotting, enzyme allergosorbent test (EAST) inhibition, and mass spectrometry. Thereby it could be demonstrated that the allergenic potential of the raw material was reduced from step to step, and despite the known stability against heat and proteolysis of certain egg proteins, the total allergenic potential was finally below 1/100 that of the starting material without a significant change in texture and flavor as evaluated in various products.     

Comparison of photosynthetic induction and transient limitations during the induction phase in young and mature leaves from three poplar clones

We tested the hypothesis that leaf age affects photosynthetic induction, because conductance to CO2 diffusion usually decreases with increasing leaf age. Photosynthetic inductions, primarily determined by the light modulation of Rubisco activity and stomatal opening, were investigated in both young and mature leaves, as defined by leaf plastochron index (LPI), from three poplar clones: Populus alba L., P. nigra L. and P. x euramericana (Dode) Guinier. In all clones, maximum assimilation rates (A max), maximum stomatal conductance (G Smax) and dark respiration rates (RD) were higher in young leaves (LPI = 3-5) than in mature leaves (LPI = 10-14), and A max decreased from P. alba via P. x euramericana to P. nigra. The clones with high photosynthetic capacity had low induction states 60 s after leaf illumination (IS60; indicating a slow initial induction phase), and required less time to reach 90% photosynthetic induction (T90). In contrast, the clone with the lowest photosynthetic capacity (P. nigra) exhibited high IS60 (high initial induction state) but a long induction time (high T90). A comparison of mature leaves with young leaves revealed significantly (P < 0.01) lower IS60 values in mature leaves of P. nigra only, and significantly higher T90 values in mature leaves of P. alba only. In all clones, young leaves exhibited a lower percentage of maximum transient stomatal limitation during photosynthetic induction (4-9%) compared with mature leaves (16-30%). Transient biochemical limitation, assessed on the basis of the time constants of Rubisco activation (tau), was significantly higher in mature leaves than in young leaves of P. alba; whereas there were no significant differences in tau between young and mature leaves of the other poplar clones. Thus, our hypothesis that leaf age affects photosynthetic induction was confirmed at the level of transient stomatal limitation, which was significantly higher in mature leaves than in young leaves in all clones. For the induction parameters IS60, T90 and tau, photosynthetic induction was more clone-specific and was dependent on leaf age only in some cases, an observation that may apply to other tree species.     

The early stress response of maize (Zea mays L.) to chloride salinity

Chloride is a micronutrient required for photosynthesis but when applied in the concentration of a macronutrient, it may also promote growth by regulating turgor. However, if chloride accumulates excessively, it can induce toxicity. The aim of this study was to identify physiological dysfunctions in maize (Zea mays L.) that arise in response to excessive chloride ion accumulation. For this, a novel water sensor was employed for the first time allowing the in vivo measurement of water content in the plant by using two near IR‐wavelengths with different absorption of water. This enabled to analyse whether water imbalances occurred. Chloride was given together with calcium as companying counter cation. Results show that most of the tested maize genotypes were able to maintain growth, photosynthesis and normal water content when stressed with concentrations as high as 757.1 mg chloride/kg soil dry matter. Leaf blades accumulated only 8.5 mg chloride/g dry matter, with the most genotypes not even showing salt stress necrosis at the leaves. A comparison between more tolerant and more sensitive genotypes revealed that restriction of chloride root‐to‐shoot translocation is a trait of chloride tolerance.     

Humus balancing in Central Europe—concepts,state of the art,and further challenges

Humus‐balancing methods are simple tools for the assessment of interactions between agricultural land use and soil organic matter (SOM). Aside from this commonality, approaches for humus balancing differ considerably with regard to their specific aim, scope, and methodical approach. The term “humus balance” covers both simple models to quantify SOM change in arable soils, or soil organic C (SOC) change in particular, and models that refer to the optimization of soil productivity in arable soils by calculating organic‐fertilizer demand, without quantifying SOM or SOC change. This situation naturally has caused much discussion and misunderstandings. Against this background, the aim of this review is to systematically explore the different methodical approaches to humus balancing in order to contribute to a more sophisticated discussion of this model family, its opportunities, and limitations. As humus balancing has long history as well as special actual relevance in Germany, and, lately Switzerland, we focus on these countries and discuss the different approaches that are presently available and applied there. We argue that humus balances can be roughly categorized into “ecological” and “agronomical” approaches based on their specific concepts and methodology. Ecological humus balances comprise a strong link to quantitative SOM change, while humus balances of the agronomical family refer to the maintenance of soil productivity without a quantitative link to SOM change. Lately, some models have been presented that link the two concepts. However, we identify that humus‐balancing methods often are insufficiently validated, partly because the validation of agronomical humus balances is not easily possible without a very comprehensive field‐experimental basis. Further, the comparability of different approaches even within the two concept families is low at present, indicating the need for a comparative model evaluation for a proper assessment of the methods.     

Mansouramycins E–G,Cytotoxic Isoquinolinequinones from Marine Streptomycetes

Chemical investigation of the ethyl acetate extract from the marine-derived Streptomyces sp. isolate B1848 resulted in three new isoquinolinequinone derivatives, the mansouramycins E–G (1a–3a), in addition to the previously reported mansouramycins A (5) and D (6). Their structures were elucidated by computer-assisted interpretation of 1D and 2D NMR spectra, high-resolution mass spectrometry, and by comparison with related compounds. Cytotoxicity profiling of the mansouramycins in a panel of up to 36 tumor cell lines indicated a significant cytotoxicity and good tumor selectivity for mansouramycin F (2a), while the activity profile of E (1a) was less attractive.