ABSTRACT(Leaf structure, microanalysis and characterization of the latex protein profile of Pachystroma longifolium (Nees) I.M. Jonhst. (Euphorbiaceae) in a seasonally dry Atlantic Forest). Pachystroma longifolium is an evergreen species of Euphorbiaceae that occurs in tabuleiro forest, a type of lowland Atlantic Forest. The site chosen for this study was a fragment of tabuleiro forest that has a history of being selectively logged for timber. P. longifolium is very successful at colonizing disturbed areas in this forest fragment in comparison with preserved fragments. In the present work, which was based on using different microscopy (electron and light microscopy, X-ray analysis) and biochemistry techniques, we describe the leaf and latex traits of P. longifolium and their role as defense mechanisms against desiccation and herbivory. Our results suggest the richness of P. longifolium populations, in the disturbed forest area studied, is primarily a consequence of unpalatable leaves because of an abundance of calcium oxalate crystals in the subjacent epidermis; the presence of phenolic compounds in the adaxial surface; and a laticifer system that contains a complex mixture of proteins, which provides resistance to herbivores. In addition, this species is resistant to desiccation during dry periods because of an extensive amount of wax that occurs on the outer cell walls of the epidermis, and its ability to retain water because of a biseriate epidermis.
The domatium presents a diversity of forms, and the understanding of the structural aspect of the domatia is very important because it can provide diagnostic characters for families and genera, and favors the establishment of mutualistic relations. The objectives of the present study were to characterize the developmental stages of the domatia of Schinus terebinthifolius Raddi. (Anacardiaceae) located at the base of the leaflet, and based on these data to determine if the structural aspects provide good shelter for mites and ants. Domatia were observed under a stereomicroscope and then processed following standard techniques for light and scanning electron microscopy. The domatia of S. terebinthifolius develop early during the development of the leaves and go through four stages of development. The domatia have a spiraling architecture with internal chambers that contain trichomes and stomata, suggesting good conditions of shelters for arthropods. Deposits of phenolic compounds and calcium crystals were identified in the domatia, suggesting an investment in alternative forms of protection from herbivory. Structural analysis showed the developmental stages of domatia and how the architecture of these structures can provide efficient shelter for arthropods, thereby contributing to the protection of these plants from herbivory and facilitating ecological studies.
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