Browsing by Subject "Gurke"

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Mechanismen der Resistenzinduktion nach Blattbehandlungen mit Phosphaten
(2002) Orober, Miroslav; Buchenauer, Heinrich
In this study the induction of resistance against plant diseases following foliar application of phosphates was investigated. The early biochemical responses of the resistance activation by phosphates have been compared with other forms of induction of SAR such as the biotic induction with pathogens and treatment with synthetic plant defense activators. In cucumber plants foliar applications of phosphates lead to increased local and systemic acquired resistance against fungal pathogens such as Colletotrichum lagenarium, Sphaerotheca fuliginea and Pseudoperonospora cubensis. In tobacco foliar phosphate application enhanced resistance against TMV. For successful induction of SAR the occurrence of chlorotic/necrotic lesions on the phosphate treated inducer leaves was necessary. These reactions were accompanied by the occurrence of localized cell death, which was preceded by the generation of reactive oxygen species such as superoxide anions and hydrogen peroxide. Enhanced lipid peroxidation was observed in the treated leaves. Local phosphate treatments induced an increase of the concentrations of free and bound salicylic acid in the treated and distal leaves. Experiments with transgenic nahG-tobacco plants showed that the expression of SAR by phosphate treatments and TNV-inoculation was strictly dependent on the accumulation of salicylic acid. The activities of characteristic defense-related enzymes like peroxidases and polyphenoloxidases were highly increased in treated and in the distal leaves, respectively. In this study it could be shown that treatments with necrotizing chemicals such as phosphates cause similar cellular reactions as observed after biotic induction with pathogens which resulted in expression of SAR. Therefore it can be assumed that foliar phosphate treatments imitate the biotic induction of systemic acquired resistance.
Vermehrungs- und Schadpotential der Grünen Gurkenlaus (Aphis gossypii Glover) an Gewächshausgurke (Cucumis sativus L.)
(2003) Bünger, Isa Brigitte Annemarie; Zebitz, Claus P. W.
The aim of this work was to collect basic data for the development of a model which could simulate the injury of greenhouse cucumbers caused by Aphis gossypii G.. This work mainly deals with two aspects: first it is the population dynamics of A. gossypii influenced by infestation density (initial infestation 2-10 individuals per plant) and host plant quality (age) and second it is the quantitative and qualitative assessment of damage by investigation of growth, yield, and chemical composition of the cucumber plants. The investigation took place under controlled, semicontrolld and practical conditions.