Insektenlarven in Bächen als Indikatoren für die Beschaffenheit des Wassers und als „Schädlinge”

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Pflanzliche Insektizide IV*. Die insektizide Wirkung des ätherischen Öls aus dem Balsamkraut,Chrysanthemum balsamita L

The essential oil ofChrysanthemum balsamita L. revealed insecticidal properties when tested againstM. dirhodum aphids. The insecticidal activity was attributed to the presence of pyrethrine I in the oil. By an appropriate testing procedure, the dependence of the activity upon the time of harvesting of the plants was determined. Furthermore, the insecticidal effect of the oil was compared with that of a commercially available pyrethrum preparation.     

Einige Eigenschaften des weiblichen Sexualpheromons des KartoffelkäfersLeptinotarsa decemlineata Say. (Col. Chrysomelidae)

The female sex pheromone ofL. decemlineata is an aphrodisiacum, switching on mating behaviour in contacting males. A biotest is described to estimate quantitatively the exciting power of a subject (female, isolated elytrae, glass dummy coated with extract) to males. The pheromone is present only in fertile females, also in freshly killed ones. It can be extracted by organic solvents. A dummy imitating a beetle's abdomen and contaminated with the residue of a female s wash solution is exciting to males too. Suitable solvents are ethylalcohol, acetonet, hexane. By this, the pheromone of 0,1 female is detectable. The residue can be taken up again with the same or an other solvent. The solution can be stored at ?18°C without significant losses, but at temperatures>+5°C their efficacy diminishes during 2 weeks. The exciting efficacy of the dry residue desreases to about 50% during nearly 4 weeks (at+22°C) or 9 weeks (at+5°C). The pheromone resists heating to about+160°C and is destroyed at higher temperatures.     

细胞分裂素:杨树气孔运动的调节剂

通过在三种杨树无性系，Ｉ－２１４（Ｐｏｐｕｌｕｓ×ｅｕｒａｎｅｒｉｃａｎａｃｖ．Ｉ－２１４）（ｌｔａｌｉｃａ）、中东杨（Ｐ．ｂｅｒｏｌｉｎｅｎｓｉｓ）（Ｂｅｒｏｌｉｎｅｎｓｉｓ）和群众杨（Ｐ．ｐｏｐｕｌａｒｉｓ３５－４４）（Ｐｏｐｕｌａｒｉｓ）一年生盆栽插条苗的木质部导入ＡＢＡ和细胞分裂素，研究了这两类激素在气孔调控中的作用。尽管不同无性系的气孔在对ＡＢＡ的敏感性上存在显著差异，但ＡＢＡ仍可导致气孔的关闭，然而在蒸腾流中的细胞分裂素（与ＡＢＡ共导入或分别导入）可以明显地抑制ＡＢＡ的作用。并且玉米素还能推迟土壤干旱所诱导的气孔关闭，在水分胁迫条件下，内源细胞分裂素浓度下降而同时ＡＢＡ上升．据此提出了复合胁迫信号的概念，即在根冠通讯中，是ＡＢＡ和细胞分裂素共同调控气孔的运动。另外还研究了玉米素、激动素、６－ＢＡ等不同细胞分裂素与ＡＢＡ的相互作用，结果发现６－ＢＡ与玉米素和激动素的作用相反，它不能抑制ＡＢＡ的作用，反而促进其对气孔的关闭     

Neue Untersuchungen zur biologischen Bekämpfung verschleppter Forstinsekten

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Anobien-Larven als Zapfenschädlinge an Weißtanne

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Critical discussion of perpendicular to grain tension testing of structural timber – case study on the European hardwoods ash,beech and maple

ABSTRACT

Knowledge about perpendicular to grain tension behavior of wood is essential, since in construction tension stresses perpendicular to grain cannot be avoided completely. Especially for hardwoods, the data basis is scarce. EN 338 design values are with 0.6 N/mm² characteristic strength set very low. The US-American National Design Specifications even set this value to zero and make local reinforcements mandatory. This paper compares strength and stiffness values attained with newly-designed, little, prismatic specimens and EN 408 structural timber specimens to evaluate the current European design values. Little specimen’s characteristic strength values range from 7.2 to 10.6?N/mm² and are assumed to be real material properties. EN 408 specimen values are with approximately 4.0?N/mm² lower. These lower values are mainly due to stress peaks introduced by the force introduction. Strength values attained for the medium-dense European hardwoods beech, ash and maple exceed EN 338 design values by a factor of six to seven. Adaptation of the EN 338 design value is not recommended, though. The abundance of influencing factors makes clear that the design value and the ensuing design code have to be synchronized carefully by tedious testing in order to make use of the perpendicular to grain tension strength potential of the selected hardwoods.     

Nitrogen supply to cereals and sugar beet by mass flow and diffusion on a silty loam soil

In a four-year field study the nitrogen supply by mass flow and diffusion to cereals (spring wheat, winter barley, winter wheat) and sugar beet was investigated on a silty loam soil. The rates of water withdrawal, N mass flow and N diffusion were determined as a function of soil depth and time. The contribution to the N supply to roots by mass flow was 15–33% and mainly confined to the topsoil layer. The N supply by diffusion plays with 67–85% the dominant role, particularly in deeper rootzone layers. During periods of high N uptake, the N inflow (per unit root length and time) ranges between 0.26–2.07 μmol/(m · d) at various rootzone layers for cereal, and between 3.80–8.98 μmol/(m · d) for sugar beet, respectively. As a consequence of the high proportion of diffusion supply, at harvest the whole rootzone was largely depleted of nitrate. Thus, nitrate leaching losses during winter were small, the average nitrate concentration of the yearly groundwater recharge being only 7.9 mg N/l. Additionally, some results on supply of K, Ca, Mg and Cl for spring wheat and sugar beet are given. Diffusion supply prevails for K, and in the case of sugar beet for Mg and Cl also. Mass flow of Ca exceeded uptake considerably.     

Predictions of soil water and crop growth dynamics using the agroecosystem models THESEUS and OPUS

The agroecosystem models THESEUS and OPUS were tested with data obtained from three agricultural experimental field plots on sandy soils without groundwater located at the moraine landscape in East Brandenburg, Germany. At each of these plots, a separate agricultural management practice was applied. Measurements of soil water contents, pressure heads, above‐ground crop biomass, and crop yield from these three plots were compared with the corresponding simulation results of both models. The comparisons of simulated with measured outputs were analyzed using the modeling‐efficiency index IA. According to these analyses, both models simulated adequately the time courses of volumetric soil water contents and above‐ground crop biomass, but the time courses of pressure heads were predicted with a lower quality by both models. As for the pressure heads, the yields simulated with both models showed greater discrepancies in comparison with the observed ones. This indicates the need of a site‐specific parameter calibration of the crop‐growth modules, especially for that included in OPUS .