Galhas lenhosas em Eremanthus erythropappus (DC.) McLeisch: alterações anatômicas e implicações ecofisiológicas

Abstract

Eremanthus erythropappus (DC.) McLeisch (Asteraceae), popularly known as candeia, is a common species in Minas Gerais state. In cecidology, candeia is very important, as a super host of galls with six associated morphotypes: two induced in the apical buds, one in the leaves and three in the stem. Among the morphotypes described, the focus of this thesis relies on the globoid stem galls induced by Neolasioptera sp. (Diptera: Cecidomyiidae). These galls are woody, rigid, lignified and induced close to the apex, but they do not compromise the apical meristem of the host branches. During gall life cycles, some developmental stages are recognized: the induction, the growth and development and maturation stages, which are characterized by the stages of manipulation of plant tissues by the gall inducer. The gall inducer can change the morphogenetic patterns of the host plant, which promotes, in E. erythropappus-Neolasioptera sp. system, the conspicuous lignification of the stem galls. Furthermore, the gall inducer activity can promote biochemical changes in primary and secondary metabolism, generating compounds with the potential to mediate the relationships of galls with other organisms. In this system, it may even cause changes in the allelopathic potential of the host plant. In the globoid stem galls, variations in the dynamics of the phytohormones orchestrate the establishment of peculiar tissue patterns that cease with the development of the galling insect, characterizing the senescent stage, which begins with the exit of the gall inducer from the gall. After exit of the Neolasioptera sp., the galls on E. erythropappus can be occupied by ants and fungi, which indicates that, in addition to providing protection and a favorable microenvironment, the galls can preserve, even if senescent, adequate chemical and nutritional profile that are used by ant colonies and fungus. Fungal hyphae in contact with remaining nutritious cells trigger the stimulus for the overproduction of secondary non-lignified xylem cells and an ectopic phellogen, configuring a post-senescent stage. Looking forward to generating dissemination and popularization scientific knowledge, the study of ant- occupied galls served as the theme to produce a para-didactic book. This book was presented in an elementary school in Belo Horizonte city as a motivator for the presenting and applying the scientific method in the school environment. The focus of this work, proved to be an interesting micro-laboratory for studies on anatomical, ecophysiological and educational perspectives. The main anatomical changes responsible for the development of the Neolasioptera sp. galls on E. erythropappus occur due to the potential of vascular cambium and phellogen responses that culminate in the peculiar anatomical traits.