RESUMO
Plant galls are generated by the stimuli of gall-inducing organisms on their hosts, creating gall morphotypes that vary in color, shape, size, and tissue organization. Herein, we propose to compare the structural features of gall morphotypes on the superhost Croton floribundus (Euphorbiaceae) in order to recognize gall morphospecies, i.e., galls with similar shapes but different internal structures. Non-galled leaves and galls were analyzed macroscopically, histologically, and histochemically for the detection of primary metabolites, and the results obtained were used for statistical analyses of similarity. Among the eight gall morphospecies, four are globoid, two are lenticular, one is fusiform and one is marginal leaf rolling. Stomatal differentiation and the occurrence of different types of trichomes were impaired in some gall morphospecies. Three patterns of organization of the ground system are recognized, ranging from the maintenance of mesophyll cells that differentiate into palisade and spongy cells dorsiventrally to the formation of a complex cortex with three morphofunctional layers. The marginal leaf rolling galls have the simplest anatomical structures, quite similar to those of the non-galled host leaf, while lenticular, globoid (types I to IV), and fusiform galls are anatomically more complex. Herein, we report on eight gall morphospecies occurring on C. floribundus, which are distinguished by morpho-anatomical attributes and show the disruption of the morphogenetic patterns of the host leaf toward the morphogenesis of unique gall features.
Assuntos
Fabaceae , Tumores de Planta , Folhas de PlantaRESUMO
The development of plant organs depends on cell division, elongation, structural and chemical changes, and reorganization of cell wall components. As phenotype manipulators, galling insects can manipulate the structure and metabolism of host tissues to build the gall. The gall formation depends on the rearrangement of cell wall components to allow cell growth and elongation, key step for the knowledge regarding gall development, and shape acquisition. Herein, we used an immunocytochemical approach to investigate the chemical composition of the cell wall during the development of galls induced by Bystracoccus mataybae (Eriococcidae) on leaflets of Matayba guianensis (Sapindaceae). Different developmental stages of non-galled leaflets (n = 10) and of leaflet galls (n = 10) were collected from the Cerrado (Brazilian savanna) for anatomical and immunocytochemical analysis. We found that the epitopes of (1 â 4) ß-D-galactans and (1 â 5) α-L-arabinans were evident in the tissues of the young and senescent galls. These epitopes seem to be associated with the mechanical stability maintenance and increased gall porosity. As well, the degree of methyl-esterification of pectins changed from the young to the senescent galls and revealed the conservation of juvenile cell and tissue features even in the senescent galls. The extensins detected in senescent galls seem to support their rigidity and structural reinforcement of these bodies. Our results showed a disruption in the pattern of deposition of leaflet cell wall for the construction of M. guianensis galls, with pectin and protein modulation associated with the change of the developmental gall stages.