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.

     

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.

     

An analysis of the water management performance of small holder irrigation schemes in Zimbabwe

This paper analyses the water management performance of small holder irrigation systems in Zimbabwe. The government and farmer managed systems are compared in terms of their ability to match desired with actual water supply. Desired supply is defined as crop water requirements adjusted downwards by rainfall where relevant. The Theil measure of accuracy of forecasts is used to calculate the error committed by each system in trying to match water supply and demand. The analysis shows that, everything else being equal, the farmer managed system performs better than the government system in matching supply and demand. This means that the farmer managed systems should be encouraged for future small holder irrigation development in Zimbabwe.     

Combining agent-based and stock-flow modelling approaches in a participative analysis of the integrated land system in Reichraming, Austria

The integrated modelling of coupled socio-ecological systems in land-change science requires innovative model concepts capable of grasping the interrelations between socioeconomic and natural components. Here, we discuss the integrated socio-ecological model SERD (Simulation of Ecological Compatibility of Regional Development) that was developed for the municipality of Reichraming in Upper Austria in a participative 2-year process involving local stakeholders. SERD includes three main components: (1) an agent-based actors module that simulates decisions of farmsteads, the municipal administration and other important actors; (2) a spatially explicit (GIS based) land-use module that simulates land-use change at the level of individual parcels of land and (3) an integrated socio-ecological stock-flow module that simulates carbon and nitrogen flows through both socioeconomic and ecological system compartments. We report on outcomes of a scenario analysis that outlines possible future trajectories depending on both external (e.g. agricultural subsidies and prices) and internal (e.g. innovation, willingness to co-operate) factors. We find that both external and internal factors can affect the behaviour of the integrated system considerably. Local and regional policies are found to be able to counteract adverse global socioeconomic conditions to some extent, but not to reverse the trend altogether. We also find strong interdependencies between socioeconomic and ecological components of the system. Fully evaluating these interdependencies is, however, not possible at the local scale alone and will require explicit consideration of higher-level effects in future research.     

RADIX: rhizoslide platform allowing high throughput digital image analysis of root system expansion

Background

Phenotyping of genotype-by-environment interactions in the root-zone is of major importance for crop improvement as the spatial distribution of a plant’s root system is crucial for a plant to access water and nutrient resources of the soil. However, so far it is unclear to what extent genetic variations in root system responses to spatially varying soil resources can be utilized for breeding applications. Among others, one limiting factor is the absence of phenotyping platforms allowing the analysis of such interactions.

Results

We developed a system that is able to (a) monitor root and shoot growth synchronously, (b) investigate their dynamic responses and (c) analyse the effect of heterogeneous N distribution to parts of the root system in a split-nutrient setup with a throughput (200 individual maize plants at once) sufficient for mapping of quantitative trait loci or for screens of multiple environmental factors. In a test trial, 24 maize genotypes were grown under split nitrogen conditions and the response of shoot and root growth was investigated. An almost double elongation rate of crown and lateral roots was observed under high N for all genotypes. The intensity of genotype-specific responses varied strongly. For example, elongation of crown roots differed almost two times between the fastest and slowest growing genotype. A stronger selective root placement in the high-N compartment was related to an increased shoot development indicating that early vigour might be related to a more intense foraging behaviour.

Conclusion

To our knowledge, RADIX is the only system currently existing which allows studying the differential response of crown roots to split-nutrient application to quantify foraging behaviour in genome mapping or selection experiments. In doing so, changes in root and shoot development and the connection to plant performance can be investigated.