Die wirkung von Aphidenstichen auf pflanzliche Zellen

Zusammenfassung Die Aphiden rufen durch den Einstich bei ihren Wirtspflanzen Reaktionen mannigfaltiger Art hervor. So sind uns Auswirkungen auf den Wasserhaushalt und den Stoffwechsel pflanzlicher Gewebe bekannt, die auf die Einwirkung pflanzensaugender Insekten zurückzuführen sind. Diese Reaktionen werden durch das Zusammenwirken der mechanischen und chemischen Komponente des Stiches ausgelöst.

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Summary The result of puncturing plant-cells by aphids was demonstrated as follows: The aphids, Myzus ascalonicus Donc., were allowed to pierce detached bulb scales of Allium cepa, in green light, and were then anaesthetized with CO₂. The stylets were then severed using iridectomy scissors (Fig. 1). The epidermis was dissected off, mounted on a slide and observed under a phase-contrast microscope. The point of injection remained marked by the stylets which stuck in the epidermis. Intercellular and extracellular puncturing could be distinguished.It was possible to demonstrate a shortening of the time deplasmolysis in the cells lying close to the injection, and also an increase of streaming in the cell plasma. In cells which had been pierced directly, a saliva-sheath was formed (Fig. 2 and 3). The extent of the effect of the saliva was studied using radioactive aphids. After these radioactive aphids had pierced the epidermis the part containing the stylets was mounted on a slide. This preparation was kept in the dark for 14 days, with a special film (Kodak, Scientific Plates, Auto radiographic) covering it. The film was developed and fixed, and a preparation was thus obtained with the developed film covering the epidermis. Darkened spots on the film showed the parts of the cells which had been made radioactive by the saliva.Very fine needles made by galvanic etching were also stuck into the cells, to demonstrate the mechanical effects of aphid punctures. This mechanical stimulus by needles only a few in diameter caused streaming in the cell plasma and a shortening of deplasmolysis time. It is clear that the importance of these mechanical effects must not be underestimated. The increased plasma-streaming was apparently caused by amino-acids in aphid's saliva, and also by the amino-acids produced from proteins when the cells were injured. Kloft (1956) found 4 amino-acids in the saliva of M. ascalonicus. The effect of these amino-acids on deplasmolysis-time is being examined, but as yet no effect has been detected.Finally, when fine glass-capillaries are used to imitate piercing by plantsucking insects and when the glass-capillaries contain amino-acids, deplasmolysis-time is reduced.