Zur Geschichte der Entdeckung des Reifungs-Anstieges im Gaswechsel von Obstfrüchten

Zusammenf assung Die Suche in der älteren Literatur nach bisher unbeachtet gebliebenen Beobachtungen über einen Reifungsanstieg im Gaswechsel von Kernobstfrüchten ergab:Der Reifungsanstieg im Gaswechsel von Obstfrüchten wurde bereits 1896 von Gerber für den Apfel dokumentiert aber übersehen, für die Banane jedoch auch beschrieben. Einige Jahre später beobachteten auch Müller-Thurgau & Schneider-Orelli (1908), daß das Ausmaß der CO₂-Ausscheidung von Äpfeln und Birnen im Verlauf ihres Wachstums bis zu einem Minimalwert absank. In diesem Zeitpunkt der minimalen CO₂-Ausscheidung gepflückte Äpfel und Birnen verstärkten im Verlauf eines ein- bis zweiwöchigen Lagerns bei Zimmertemperatur ihre CO₂-Ausscheidung auf etwa den doppelten Wert. Wurden die Äpfel erst einige Wochen nach dem Erreichen der Phase der minimalen CO₂-Ausscheidung gepflückt, so erfolgte der Anstieg der CO₂-Ausscheidung bereits auf dem Baum. Es wird geprüft, inwieweit die Autoren in diesen beobachteten Anstiegen der CO₂-Ausscheidung ein wesentliches, mit dem climacteric rise der englischen Forscher zu identifizierendes Reifungsphänomen erkannten.

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On the history of the discovery of the climacteric rise in gas exchange of pome fruits

In the older literature some observations concerning the gas exchange of ripening pome fruits have been found and discussed in this paper. These observations have been lost later on.The climacteric rise in gas exchange of apple fruits can be concluded from tables published by Gerber as early as 1896. Gerber himself did not recognize this phenomenon. In the case of the banana, however, he recorded and reported this rise in gas exchange during ripening.Some years later, Müller-Thurgau & Schneider-Orelli (1908), too, observed that the rate of the CO₂ output of apple and pear fruits diminishes to a minimal value during their growth period. Apple and pear fruits picked in this phase of minimal CO₂ output double the rate of their CO₂ output during the storage at room temperature for one to two weeks. If the apples are picked not before some weeks after having reached the phase of minimal CO₂ output, the rise in CO₂ output occurs already on the tree. Finally, it is discussed how far the authors have recognized that the observed rise in CO₂ output is an integer phenomenon of ripening for most of fleshy fruits. It is well known that this phenomenon is identical with the climacteric rise of the English investigators.

     

Genetic approach for the fast discovery of phenazine producing bacteria

A fast and efficient approach was established to identify bacteria possessing the potential to biosynthesize phenazines, which are of special interest regarding their antimicrobial activities. Sequences of phzE genes, which are part of the phenazine biosynthetic pathway, were used to design one universal primer system and to analyze the ability of bacteria to produce phenazine. Diverse bacteria from different marine habitats and belonging to six major phylogenetic lines were investigated. Bacteria exhibiting phzE gene fragments affiliated to Firmicutes, Alpha- and Gammaproteobacteria, and Actinobacteria. Thus, these are the first primers for amplifying gene fragments from Firmicutes and Alphaproteobacteria. The genetic potential for phenazine production was shown for four type strains belonging to the genera Streptomyces and Pseudomonas as well as for 13 environmental isolates from marine habitats. For the first time, the genetic ability of phenazine biosynthesis was verified by analyzing the metabolite pattern of all PCR-positive strains via HPLC-UV/MS. Phenazine production was demonstrated for the type strains known to produce endophenazines, 2-hydroxy-phenazine, phenazine-1-carboxylic acid, phenazine-1,6-dicarboxylic acid, and chlororaphin as well as for members of marine Actinobacteria. Interestingly, a number of unidentified phenazines possibly represent new phenazine structures.     

Impact of Pea necrotic yellow dwarf virus (PNYDV) on nodulation,N2 fixation and yield in faba bean (Vicia faba,L.)

Journal of Plant Diseases and Protection - Pea necrotic yellow dwarf virus (PNYDV) is a novel nanovirus in Europe, affecting various grain legumes. The impact of PNYDV on nodulation, symbiotic N2...     

Comparison of methods to quantify loss of hydraulic conductivity in Norway spruce

? Percent loss of hydraulic conductivity (PLC) is an important measure in plant water relations, but the available methods differ and results have rarely been compared.

? We compared PLC measured in Norway spruce (Picea abies) by quantifying conductivity before and after removing emboli, either by flushing with high water pressure or by infiltration under a partial vacuum, with relative water loss and staining conductive xylem to test advantages and possible problems of commonly applied methods.

? Infiltration removed nearly all gas from sections of drought-stressed and unstressed twigs, and flushing and infiltration efficiently removed emboli. Infiltration appears less prone to producing clogged xylem elements than high pressure flushing. Relative water loss (RWL) and the proportion of xylem stained with phloxine B (PSX) was also highly correlated with PLC, the latter can be quantified by image analysis, and also shows the pattern of xylem dysfunction. Loss of conductivity was more common in the inner annual rings, in early wood within an annual ring, and in compression wood, though pattern differed substantially between branches.

? Advantages and potential problems of these methods are discussed and it is suggested that RWL or PSX may be used as proxy measures for PLC in species when the correlations have been established.

     

Resistance risk assessment of two insect development inhibitors,diflubenzuron and cyromazine,for control of the housefly Musca domestica. part i: Larvicidal tests with insecticide-resistant laboratory and danish field populations

Larvicide tests with diflubenzuron (DFB) and cyromazine (CYR) were carried out against 15 laboratory housefly strains and 89 field strains collected from 87 Danish and 2 Swedish farms, 1975–89. The strains represented a wide range of adult insecticide resistance and R-mechanisms. The larvicide tests were done by treating larval medium with serial or discriminating dosages of the larvicide, seeding it with eggs and calculating the mortality during development to adults. The WHO susceptible strain (S) was used as a reference. Dose-response tests with DFB gave resistance ratios (R/S) from 1·1 to 4·1 at LC₅₀ and 0·3 to 3·4 at LC₉₅ and, with CYR, R/S from 0·6 to 1·8 at LC₅₀ and 0·6 to 2·9 at LC₉₅. It was concluded that the relatively small variation in susceptibility between strains was not generally correlated with resistance in adult flies to organophosphorus, pyrethroid or other conventional insecticides (neurotoxins). Tests with discriminating dosages of DFB (59 farms) and CYR (63 farms) showed no indication of resistance to either product. The results of investigations by other workers on the relation between resistance to DFB or CYR and resistance to conventional insecticides are discussed.