BackgroundAcidity exerts a determining influence on the composition and diversity of freshwater faunas. While the physiological implications of freshwater acidification have been intensively studied in teleost fish and crayfish, much less is known about the acid-stress physiology of ecologically important groups such as cladoceran zooplankton. This study analyzed the extracellular acid-base state and CO2 partial pressure (PCO2), circulation and ventilation, as well as the respiration rate of Daphnia pulex acclimated to acidic (pH 5.5 and 6.0) and circumneutral (pH 7.8) conditions.ResultsD. pulex had a remarkably high extracellular pH of 8.33 and extracellular PCO2 of 0.56 kPa under normal ambient conditions (pH 7.8 and normocapnia). The hemolymph had a high bicarbonate concentration of 20.9 mM and a total buffer value of 51.5 meq L-1 pH-1. Bicarbonate covered 93% of the total buffer value. Acidic conditions induced a slight acidosis (ΔpH = 0.16–0.23), a 30–65% bicarbonate loss, and elevated systemic activities (tachycardia, hyperventilation, hypermetabolism). pH 6.0 animals partly compensated the bicarbonate loss by increasing the non-bicarbonate buffer value from 2.0 to 5.1 meq L-1 pH-1. The extracellular PCO2 of pH 5.5 animals was significantly reduced to 0.33 kPa, and these animals showed the highest tolerance to a short-term exposure to severe acid stress.ConclusionChronic exposure to acidic conditions had a pervasive impact on Daphnia's physiology including acid-base balance, extracellular PCO2, circulation and ventilation, and energy metabolism. Compensatory changes in extracellular non-bicarbonate buffering capacity and the improved tolerance to severe acid stress indicated the activation of defense mechanisms which may result from gene-expression mediated adjustments in hemolymph buffer proteins and in epithelial properties. Mechanistic analyses of the interdependence between extracellular acid-base balance and CO2 transport raised the question of whether a carbonic anhydrase (CA) is involved in the catalysis of the reaction, which led to the discovery of 31 CA-genes in the genome of D. pulex.

The reactivity of FeMoO 4 in CsCl fluxes has been investigated by thermal analysis and chemical reactions in evacuated silica ampules. The products have been characterized by ex situ X-ray diffraction methods. Metathesis reactions involving CsCl lead to the formation of Cs 2 Fe 2 (MoO 4 ) 3 and the salt adduct Cs 2 FeCl 4 •CsCl. A side reaction has been observed, which is associated with a decomposition of [MoO 4 ] 2− in CsCl fluxes yielding Cs 2 Mo 2 O 7 •CsCl, which contains the rare pyromolybdate anion, [Mo 2 O 7 ] 2− , located in the center of a ∞ 2 [CsCl] heterohoneycomb arrangement. This salt-inclusion type of compound has been studied further in terms of its formation starting from Cs 2 MoO 4 , MoO 3 , and CsCl. The intermediate adduct phase, Cs 2 MoO 4 •MoO 3 , contains uncharged ∞ 1 [MoO 2 O 2/2 ] chains that react with CsCl at elevated temperatures to Cs 2 Mo 2 O 7 •CsCl.Furthermore, the site preference for alkaline-metal cations (K + , Rb + , and Cs + ) has been evaluated for a mixed substitution series. In accordance with the Pearson concept, the polarizability of the respect cation outweighs any size differences for the occupancy of the salt-intergrowth motif, the honeycomb part of the structure.

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Celem doświadczenia była ocena reakcji nowych odmian kukurydzy cukrowej na stosowanie mieszaniny mezotrion + S-metolachlor. Badania przeprowadzono w latach 2007–2009 w ZDD Gorzyń, filia Swadzim. Przebadano dziesięć odmian kukurydzy cukrowej — Basin, Dixon, Garrison, Golda, GSS 5022, Rana, Shaker, Shimmer, Sweet Trophy oraz Sweet Tasty. Zabieg herbicydem wykonano w fazie 5–6 liści kukurydzy cukrowej. Określono plon kolb (t/ha), udział kolb I klasy (%), długość kolb (cm), liczbę kolb z hektara (szt.) oraz liczbę ziaren w kolbie (szt.). Stwierdzono przemijające fitotoksyczne działanie herbicydu u trzech badanych odmian. Mieszanina mezotrion + S-metolachlor wpłynęła na obniżenie plonu ośmiu odmian, zmniejszenie udziału kolb I klasy u siedmiu odmian, długość kolb u sześciu odmian oraz liczbę kolb zebranych z hektara u dziewięciu odmian, nie miała jednak istotnego wpływu na liczbę ziaren w kolbie.