OXIDATIVE BALANCE AND PHOTOCHEMICAL PERFORMANCE THROUGHOUT THE DEVELOPMENT OF Sapium glandulosum (EUPHORBIACEAE) LEAF GALLS INDUCED BY Neolithus fasciatus (HEMIPTERA: TRIOZIDAE)

Abstract

The induction of galls in the host plants is usually associated with an increase in oxidative stress mediated by reactive oxygen species. The stress is regulated by dissipation pathways, which minimize lipid peroxidation in the galled tissues. Thus, the aim the current study was to evaluate the levels of oxidative stress, its dissipation pathways, and the impact on photosynthetic metabolism during the development of leaf galls of Sapium glandulosum (Euphorbiaceae) induced by Neolithus fasciatus (Hemiptera: Triozidae). So, non-galled leaves and galls in the young, mature, and senescent stages were submitted to histochemical analysis, photosynthetic activity, pigment dosage, quantification of oxidative stress, phenolic substances and antioxidant enzymes. Hydrogen peroxide was labeled in the photosynthetic tissue of the leaf and in the vascular bundles of the galls during the different stages of development. The malondialdehyde content was higher in the leaves and senescent galls, while the quantification of phenolics showed no difference between the leaf and galls. The activity of catalase, peroxidase and ascorbate peroxidase were higher in the leaf than galls. In contrast for superoxide dismutase, the higher values for galls were found. The chlorophyll contents were fourteen times higher in the leaf than in the three developmental stages of galls, yet there was no difference in the maximum quantum yield between the treatments except for senescent galls. The gall of S. glandulosum seems to efficiently regulate oxidative stress mainly by the activity of superoxide dismutase, maintaining its photochemical yield similar to that of the leaf.