Die Reaktion von Getreideblattläusen (Hom., Aphididae) bei holozyklischer Überwinterung auf die Aussaatzeit von Weizen. Mit Beobachtungen zum Einfluß heftiger Niederschläge

On plots (25 m²) sown at different dates it was tested from 1982 to 1984 near Kiel (FRG) whether the sowing date would result in different levels of infestation of wheat by holocyclic cereal aphid populations. Aphids were too scarce to obtain results in 1982, and in the subsequent yearsSitobion avenae F. was the only species being abundant. In winter wheat (var. “Diplomat”), holocyclicS. avenae did not respont numerically to the sowing date. The maximum of attack, being equal in all sowing dates, occurred in growth stage 75. Small differences between sowing dates could be explained by the different abundance of natural enemies. In spring wheat (var. “Kolibri”) significant differences between sowing dates were observed, the earliest sown plots being attacked most heavily byS. avenae. The maximum of attack occurred in growth stage 71, mostly. Heavy precipitations proved to diminish significantly the numbers ofS. avenae per head at milky ripeness (GS 75), but not at GS 71. Numbers ofRhopalosiphum padi (L.) were not influenced significantly by the amount of precipitations falling during the observations. But precipitations and 8 other factors considered failed to explain the differences between sowing dates of spring wheat concerning the attack byS. avenae. It is assumed, therefore, that the physiological conditions of the wheat plant were gouverning the aphids' reproduction. The differences concerning the attack of winter wheat, apparently existing between holocyclic and prevailingly anholocyclic populations ofS. avenae, are stressed.     

Bioindication and modelling of atmospheric deposition in forests enable exposure and effect monitoring at high spatial density across scales

Key message

Moss surveys provide spatially dense data on environmental concentrations of heavy metals and nitrogen which, together with other biomonitoring and modelling data, can be used for indicating deposition to terrestrial ecosystems and related effects across time and areas of different spatial extension.

Context

For enhancing the spatial resolution of measuring and mapping atmospheric deposition by technical devices and by modelling, moss is used complementarily as bio-monitor.

Aims

This paper investigated whether nitrogen and heavy metal concentrations derived by biomonitoring of atmospheric deposition are statistically meaningful in terms of compliance with minimum sample size across several spatial levels (objective 1), whether this is also true in terms of geostatistical criteria such as spatial auto-correlation and, by this, estimated values for unsampled locations (objective 2) and whether moss indicates atmospheric deposition in a similar way as modelled deposition, tree foliage and natural surface soil at the European and country level, and whether they indicate site-specific variance due to canopy drip (objective 3).

Methods

Data from modelling and biomonitoring atmospheric deposition were statistically analysed by means of minimum sample size calculation, by geostatistics as well as by bivariate correlation analyses and by multivariate correlation analyses using the Classification and Regression Tree approach and the Random Forests method.

Results

It was found that the compliance of measurements with the minimum sample size varies by spatial scale and element measured. For unsampled locations, estimation could be derived. Statistically significant correlations between concentrations of heavy metals and nitrogen in moss and modelled atmospheric deposition, and concentrations in leaves, needles and soil were found. Significant influence of canopy drip on nitrogen concentration in moss was proven.

Conclusion

Moss surveys should complement modelled atmospheric deposition data as well as other biomonitoring approaches and offer a great potential for various terrestrial monitoring programmes dealing with exposure and effects.

     

Characterization of black locust (Robinia pseudoacacia L.) heartwood extractives: identification of resveratrol and piceatannol

Robinia pseudoacacia L. heartwood is characterized by a very high natural durability. However, a significant difference was observed between the mature and juvenile heartwood, the latter presenting less durability against fungi decay, which could be attributed to lower extractive content. In order to elucidate this idea, extractives from mature and juvenile heartwoods of black locust trees were investigated. Results showed that extractive and phenolic contents were higher in mature than in juvenile heartwoods. The identification of phenolic compounds by UPLC–DAD–MS/MS revealed, for the first time, the presence of resveratrol and piceatannol. These two stilbenes as well as the flavonoid dihydrorobinetin were present at the highest level in mature heartwood, and as they are known antifungals, they could account for the great durability of mature heartwood. The stilbenes were detected in significant amounts particularly in mature heartwood where piceatannol reached a level tenfold higher than that reported for Japanese knotweed roots, the primary natural source of these stilbenes, whereas resveratrol level was comparable with reported values. As resveratrol and piceatannol receive increasing demand for nutraceutical, cosmetic and, possibly, pharmaceutical purposes, due to their beneficial health effects, this study underlines the use of R. pseudoacacia as a promising sustainable and economical source of resveratrol and piceatannol.     

Natural variation within the genus Beta and its possible use for breeding sugar beet: A review

Summary Sugar beet is a relatively young crop, which supposedly has a narrow genetic base. Natural variation occurring in primitive beet varieties and in wild Beta species has been used for breeding sugar beet. This paper reviews information on desirable characteristics in Beta germplasm and the attempts made for the introgression of such characters into commercial breeding material. After an introduction on the availability of germplasm and the possibilities of hybridisation, attention is focussed on the mating system (especially male sterility), on morphological and physiological characteristics, including yield and sugar content, and on resistances to diseases and pests.     

Evaluation of mulched drip irrigation for cotton in arid Northwest China

Field experiments were conducted in arid Southern Xinjiang, Northwest China, for 3 years to evaluate sustainable irrigation regimes for cotton. The experiments involved mulched drip irrigation during the growing season and flood irrigation afterward. The drip irrigation experiments included control experiments, experiments with deficit irrigation during one crop growth stage, and alternative irrigation schemes in which freshwater was used during one growth stage and relatively saline water in the others. The average cotton yield over 3 years varied between 3,575 and 5,095 kg/ha, and the irrigation water productivity between 0.91 and 1.16 kg/m³. Crop sensitivities to water stress during the different growth stages ranged from early flowering-belling (most sensitive) > seedling > budding > late flowering-belling (least sensitive), while sensitivities to salt stress ranged from late flowering-belling > budding > seedling > early flowering-belling. Although mulched drip irrigation during the growing season caused an increase in salinity in the root zone, flood irrigation after harvesting leached the accumulated salts to below background levels. Numerical simulations, based on the 3-year experiments and extended by another 20 years, suggest that mulched drip irrigation using alternatively fresh and brackish water during the growing season and flood irrigation with freshwater after harvesting is a sustainable irrigation practice that should not lead to soil salinization.