Wechselwirkungen zwischen pflanzensaugenden Insekten und den von ihnen besogenen Pflanzengeweben

Summary This work was undertaken to find out, using plant physiological methods, the reaction of plant tissue to the penetration by and feeding of plant lice; it showed that spontaneous primary reactions and long term secondary reactions must be distinguished. Shock like disturbances in the transpiration and water intake of the host plant and interference with photosynthesis (by lowering of the assimilation rate) and respiration were established as primary reactions. In the vicinity of the puncture, a raising of the permeability, alteration in viscosity and the raising of the rate of flow of protoplasm could be proved cytophysiologically. The importance of these cytophysiological effects on the feeding of the plant lice is discussed. Besides the already known secondary reactions such as inhibition of growth, gall formation, shoot deformation etc., restriction of flowering and shooting and alterations in osmotic value (alterations in enzyme activity) are described, as well as long term respiration increases, e. g. attack by Quadraspidiotus perniciosus Comst. raises the oxygen consumption to three times its normal value. As it was thought that, besides the mechanical effects, the saliva of plant lice was mainly responsible for phytopathological symptoms, analyses of pure saliva were carried out to determine the enzymes and free amino acids. The free amino acids found had an effect on the respiration, photosynthesis and water balance of the plant tissues and must therefore be largely concerned in the phytopathological effects. The mechanism of saliva secretion was found by the use of a tracer (P 32 ). In phloem feeding aphids (Myzus ascalonicus Donc.), saliva is secreted only with insertion (6–8 min. long) and retraction of the stylets and not in the intervening time no matter how long the insect may feed. In contrast to this, parenchyma feeders secrete more or less continuously and the fundamental differences between the two types of feeding are fully discussed. The mutual effects on plant and aphid, with a parenchyma feeding species, are well illustrated by histochemical and physiological methods, using as an example the bark of Abies pectinata attacked by Adelges piceae. The spread of saliva in the plant is described in detail, using autoradiographic and X‐ray techniques. The mechanism of feeding in Myzus ascalonicus is calculated in relation to the relevant pressure conditions and rates of flow.