Caracterização morfoanatômica foliar de Commiphora leptophloeos (Mart.) J. B. Gillet (Burseraceae) em diferentes ambientes do norte de Minas Gerais, Brasil

Abstract

Seasonally dry tropical forests (FTSS) have a large representation in the Domain of caatingas and have a marked environmental heterogeneity. The plant species in these environments have developed several survival strategies in the face of edaphic heterogeneity and water restrictions. Among the existing species, Commiphora leptophloeos is an arboreal species occurring in different environments, which can contribute to the understanding of the likely plasticity to adjust to edaphic variations in different environments. The objective of this work was to test whether there is a morphoanatomical variation of the leaves of Commiphora leptophloeos, a species with overlapping occurrences in two environments with different edaphic conditions, mainly related to the depth and water retention capacity of the soil. The collections were carried out in Caatinga arbórea (CA) and Furados (FU) areas, in the north of Minas Gerais. They have different environmental characteristics: CA – dense vegetation area, fertile and deep soils, while FU – low density vegetation area, fertile and shallow soils under limestone slabs. The soil samples were collected following standard methodology, for analysis and characterization. Completely expanded leaves were collected and these were selected from the leaflets and rake fragments, fixed in 70% ethanol, made, and photographed histological slides from the transversal and parapermic sections. The anatomy of the rachis showed the presence of pluricellular trichome tracts, druses, and secretory structures in the phloem region. The anatomy of the leaflets showed an uniseriate adaxial epidermis formed by juxtaposed cells, with an irregular cuticle and with the presence of a subepidermal parenchymatic layer, and an uniseriate abaxial epidermis, formed by juxtaposed cells, with a less thick cuticle; the mesophyll is an isobilateral type with a palisade parenchyma with elongated cells on the adaxial face and short cells on the abaxial face, while the spongy parenchyma has irregular cells, with the presence of intercellular spaces. In the mesophyll, druses and the secretory structures inserted in the vascular bundles were observed, in addition to trichomes on both sides. The main vascular bundle has a closed arch shape, secretory structures in the phloem and an accessory vascular bundle with inverted xylem. The fundamental parenchyma is made up of thin-walled cells. The leaves are hypoestomatic and the stomata are anomocytic type. The quantitative analysis of the soil showed differences between values of pH, Mg, clay and sand. In the rachis, the quantitative analysis showed differences between the xylem area and the secretory structures of the phloem. In the leaflet, differences in adaxial cuticle thickness and epidermis, equatorial and polar diameter, density of trichomes on the adaxial and abaxial surface, abaxial palisade parenchyma, Carlquist vulnerability index and total sclerenchyma area were evidenced. It was possible to observe that the conditions given by the edaphic variables provide investments in the morphoanatomical characteristics, which are shown to be plastic due to environmental factors. Therefore, the results demonstrate that the morphoanatomical characteristics undergo changes due to the influence of the edaphic variables, guaranteeing their ability to adapt and survive in xerophytic environments.