Cytological and histochemical gradients induced by a sucking insect in galls of Aspidosperma australe Arg. Muell (Apocynaceae)

The storage of carbohydrates and lipids was previously investigated in nutritive tissues of galls of Cecidomyiidae and Cynipidae. Unexpectedly, starch accumulation has been detected in non-nutritive galls induced by Hemiptera, which feed directly from phloem bundles. Samples of non-galled leaves and galls induced by Pseudophacopteron sp. in Aspidosperma australe were processed for light and electron microscopy. Histochemical tests detected sites of ROS (reactive oxygen species), carbohydrates, and enzymes. PCD (programmed cell death) evidenced by plastoglobules and ROS formation also occurred. Phosphorylase and sucrose synthase activity indicated the steps of starch storage. The sites of glucose-6-phosphatase activity were related to the provision of sucrose for gall growth and nutrition of Pseudophacopteron. Acid phosphatase took part in the metabolism of starch and degradation of some organelles during the main trophic phase of the insect. The invertases were related to the sites of hyperplasia, and regulation of cell growth and intense respiration. The cytological and histochemical gradients validate the storage of starch as a pattern in galls induced by sucking insects. The detection of enzymes related to carbohydrate metabolism and sites of ROS production is described for the first time for galls induced by sucking insects in the Neotropical region.