Eremanthus sp.: caracterização funcional e estrutural de plantas jovens sob variações na disponibilidade hídrica e de radiação

Abstract

Eremanthus Less. (Asteraceae) comprises shrub and tree species popularly known as “candeia”, three of which, Eremanthus erythroppapus, E. incanus and E. glomerulatus, are highly representative in the State of Minas Gerais. However, these “candeia” species have very similar structural characteristics, making it difficult to differentiate in the field. In addition, E. incanus occurs in several formations of the Cerrado biome, such as hillside forests, Cerrado sensu stricto, Campo Rupestre, among others. In this phytophysiognomic variation there are different environmental gradients, such as soil water resources and radiation, for example, which may interfere with the development of the species. In this context, the thesis is divided into three chapters. In the first, there is a bibliographic review on the subject. In the second, there is a work with the objective of characterizing the internal and external morphology of these species of “candeia” to facilitate their identification. Anatomical, histochemical and ultrastructural analyzes of the leaf surface were carried out, in addition to analyzes of the external morphology of the leaves, with the observed characteristics evaluated in a qualitative and comparative way. As a result, it was observed that the greatest differentiation between the three species was possible through the external morphological characteristics. The most representative characters were used to create a dichotomous key. Thus, morphological characters such as shape, consistency, color of the indument and leaf petiole are the most suitable for differentiating the three species of “candeia” studied. In the third, there is a work with the objective of analyzing the variations of the structural and functional characteristics of the leaves and roots of young plants of Eremanthus incanus under different conditions of water availability and radiation intensity. For this, an experiment was carried out in a greenhouse with E. incanus planted in plastic pots, with a substrate of sieved subsoil soil and carbonized rice husks (3:1), plus the addition of simple superphosphate and potassium chloride. The experiment had 4 treatments, with 10 repetitions each: T1 - 100% H2O and 100% Light; T2 - 100% H2O and 50% Light; T3 - 50% H2O and 100% Light and T4 - 50% H2O and 50% Light. The following analyzes were performed: leaf and root anatomy (primary and secondary structure), gas exchange and growth analysis. In the leaf, the thickness of the cuticle, the palisade and spongy parenchyma, the blade and the trichome layer, the stomatal density on the adaxial face and the areas of vascular tissues in the midrib were affected by the treatments. In the root, only the primary structure showed modifications, namely in the thickness of the epidermis, cortex, and endodermis, and in the Carlquist Vulnerability Index. All gas exchange and growth variables were influenced by experimental conditions. Thus, it was possible to establish some correlations between structural and functional variables that may favor better plant growth, with photosynthesis and stomatal density being the variables with greater plasticity. At the end of this work, we obtain a dichotomous key for better identification of “candeia” species and better understand how E. incanus adjusts to variations in radiation and water availability.