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Despite the uniqueness and reach of the flora from natural savannas in the Brazilian Amazon, and the existence of studies on its origin and diversity, there are no local studies associating floristic patterns with soil properties in savanna enclaves in the Amazon region of the state of Mato Grosso. Floristic composition and diversity were compared between a woody community from a rocky savanna inselberg in a transition region (RTS) between the two largest South American biomes (Cerrado-Amazon), and an enclave of rocky savanna in the Amazon (RAS), and the effects of soil properties were investigated. Floristic comparisons were also made between the two studied communities and two other rocky savanna communities near the Cerrado-Amazon transition. The flora and physical and chemical soil properties in twenty-five 20 × 20 m subplots (1 ha) in each community were sampled and georeferenced. An evident floristic distinction was found between the two studied communities, with low similarity values and a high number of indicator species. The observed and estimated richness and Rényi diversity profiles indicated lower species diversity in RAS than in RTS. Soils were found to be litholic, poorly drained, dystrophic, alic, extremely acidic, sandy and nutrient poor. Species composition and abundance was associated with soil properties in both communities. The clear difference in species composition and diversity between RTS and RAS seem to be shaped by soil properties, geographic isolation and floristic influence from the Cerrado and the Amazon. These results broaden the knowledge regarding the composition and diversity of woody plants of savannas in Amazonian enclaves and Cerrado inselbergs, and provide an important set of floristic and edaphic descriptors for the phytogeography of rocky savannas.

This study aimed to understand the functionality and structural adjustments of wood in a rocky-outcrop plant community in an Amazonian savannah by correlating anatomical traits of wood associated w...

Qualea genus is commonly found in different phytophysiognomies of the Brazilian Cerrado, growing in open ecosystems to closed forest areas, under high irradiances, fires, low availability of nutrients and seasonal water deficit. We compared the leaf structural traits of Qualea grandiflora Mart., Qualea multiflora Mart., and Qualea parviflora Mart., in a cerradão area in the Cerrado-Amazonian forest transition. Leaf samples were collected at Mário Viana Municipal Biological Reserve, in Nova Xavantina, Mato Grosso state, Brasil, and processed according to the usual techniques for optical microscopy. Thick cuticle, stomatal ridges, stomata distributed between the stomatal crypts, density and distribution of tector trichomes, hypodermis, isobilateral mesophyll with few intercellular spaces, abundance of sclerenchyma associated to vascular bundles and the presence of vascular bundle sheath extensions are typical anatomic traits of xerophytic environments. We found qualitative structural differences among the species, with Qualea grandiflora having stomata with ridges distributed among stomatal crypts, and the presence of a hypodermis in Qualea multiflora, and Qualea parviflora. The results suggest that the species are xeromorphic in the region of Cerrado-Amazonian transition having leaf adaptive traits to deal with the environmental variations of their habitat.

This study represents an important contribution to the structural, histochemical and biological understanding of ducts and cavities in leaves of four species of Calophyllaceae that occur in Amazonian savannas. Samples of adult leaves were processed using light, scanning and transmission electron microscopy, as per usual methods for plant anatomy. In paradermal sections, the lumina of ducts are elongated while those of cavities are short. Ducts occur exclusively in the central rib and are abundant in Kielmeyera rubriflora Cambess and Kielmeyera coriacea Mart. and Zucc and larger than in Calophyllum brasiliense Cambess and Caraipa densifolia Mart. In mesophyll, the type of secretory structure and distribution pattern of the ducts and cavities are distinct. In most species, the secreted metabolites are similar and consist of phenolic compounds, lipids, essential oils with oleoresins, mucilage, neutral polysaccharides, proteins and alkaloids, except in K. coriacea, which does not contain oleoresin. The secretion is probably synthesized by mitochondria, rough endoplasmic reticulum, ribosomes and dictyosomes and is externalized toward the lumen by granulocrine and eccrine processes. In addition to being of diagnostic value for species identification, the attributes of the lumen shape, type of secretory structure, distribution pattern, identified metabolites and secretion mechanism are important for understanding the biological roles of ducts and cavities. The identified metabolites reveal a capacity for adaptation, resistance and protection from the action of herbivores and pathogens, and in water retention.

The diversity of environments in the Neotropical region has different environmental filters on vegetation. The southern face of the Amazon is exposed to high rainfall seasonality and poor soils, which imposes a severe environmental filtering. Plants with structural and functional adaptations can occur in specific locations due to microenvironmental characteristics. We investigated how anatomical-leaf attributes of seven co-occurring species of savanna and forest formations respond to the environmental conditions of their phytophysiognomies using usual optical microscopy techniques and statistical models. The species have different strategies to support environmental conditions. Even under a more limiting rainfall regime, plants living in seasonal forests closely related with savannic areas (Cerradao area - CDA) are less endowed with xeromorphic characteristics, which we can attribute to the conditions of continuous canopy and soil, comparatively more clayey than savanna soils. The species associated with rocky outcrops more closely related to savannic habitats (Rupestrian Cerrado of Transition area - RCT) showed greater investment in thickness of epidermal cell walls and the total thickness of the central vein. These species, together with the species associated with rocky outcrops more closely related to forest habitats (Amazon Savanna on Rocky Outcrops area - ASR), demonstrated greater investment in cuticle, straight anticline walls, straight periclinal walls or straight and convex periclinal walls, epidermis thickness, parenchyma, secretory ducts, collenchyma and sclerenchymatous fibers. Our findings reveal species’ different responses to environmental conditions: ASR and RCT species present a likely longer (temporal) selective process with a high investment in hydraulic safety, but RCT species showed greater xeromorphism; CDA forms a less xeromorphic microenvironment. The leaf xeromorphism is not only determined by the rainfall levels or soil fertility characteristics, but also by the degree of exposure of these plants to solar radiation and local seasonality.

In South America, the largest area of tropical savanna is the Brazilian Cerrado biome, which encompasses a considerable range of environmental variation, with different types of soil, geology, geomorphology and climate, as well as distinct types of vegetation. These savannas include two types of vegetation: one on hilly slopes, with relatively shallow interspersed with rocky soils (RS), known as Rocky Cerrado, and the other located on flat terrain with deep soils (DS), known as Typical Cerrado. Our objective was to evaluate the effects of the heterogeneity of the chemical and granulometric properties of the soils on the composition and diversity of the shrubby–arboreal strata of the RS and DS. We found that, despite the reduced abundance of woody plants in the RS, and the physical limitations on plant development imposed by the rocky outcrops found in this environment, the RS is characterized by similar species diversity to that found in the DS. We present evidence of greater heterogeneity in the species composition and edaphic proprieties of the RS in comparison with the DS. We conclude that the greater variation and heterogeneity in the substrates of the RS accounts for the similarity in the species diversity between the RS and DS, although we suspect that other drivers, not investigated here, may also be involved. The intense conversion of native vegetation within the study region interferes with the establishment of exclusive species in RS (e.g., Norantea guianensis Aubl.) and DS (e.g., Couepia grandiflora (Mart. & Zucc.) Benth.) and consequently threatens the community structure of both environments with fundamental implications for the conservation.

O conhecimento anatômico de espécies do gênero Theobroma é importante para o estabelecimento e manutenção de coleções de germoplasma, tendo em vista estudos agronômicos e fitopatológicos e programas de melhoramento genético. Este estudo objetivou caracterizar a anatomia das folhas de Theobroma speciosum, registrando as diferenças estruturais observadas entre folhas de sol e folhas de sombra. Folhas de indivíduos de Theobroma speciosum foram coletadas no Parque Nacional do Juruena e em pastagens na zona rural do município de Alta Floresta – MT. Foram analisados a espessura do mesofilo foliar, dos parênquimas paliçádico e lacunoso, da nervura mediana e do feixe vascular. A análise de agrupamento foi realizada utilizando o método Hierárquico UPGMA, com base na distância euclidiana média padronizada. Foram observados tricomas glandulares do tipo claviforme e estrelados sésseis. A epiderme é unisseriada, o mesofilo é dorsiventral, entretanto os parênquimas são pouco distintos. Feixes vasculares colaterais estão dispersos no mesofilo, formando bainhas que se estendem até as epidermes. A nervura central, em secção transversal, possui formato biconvexo, com sistema vascular fechado envolto por bainha esclerenquimática. A constituição do mesofilo das folhas variou com o ambiente. Plantas expostas a pleno sol apresentam células mais alongadas no parênquima paliçádico, parênquima lacunoso com mais camadas e maior quantidade de tricomas, enquanto que as folhas de sombra apresentaram células com muitos espaços intercelulares no mesofilo. O dendrograma mostrou a formação de dois grupos distintos: o grupo I composto pelas plantas do Parque e o grupo II pelas plantas das pastagens. Tal agrupamento demonstrou alterações anatômicas significativas ocasionadas pelas variações da intensidade luminosa sobre as folhas, o que evidenciou grande capacidade adaptativa de Theobroma speciosum.

This is among the first studies that associate anatomical characteristics to the environment in the transition region between the two largest phytogeographic domains of South America. We aimed to analyze the leaf anatomy of 22 plant species occurring in the Amazonian savanna in the state of Mato Grosso, Brazil, with the purpose of identifying key characters that show adaptive species strategies in their natural environments. Our hypothesis was that species typical of forest habitats would not present xeromorphic characteristics, while species typical of savanna habitats would present such characteristics. We fixed the samples in FAA 50 , 1 that were stored in alcohol 70%, later they were free-hand cut with a razor blade and stained with astra blue and basic fuchsin. For the analysis of the leaf epidermis, we used the Jeffrey modified method of separation. Characteristics such as thick cuticle, epidermis with thickened wall and straight, presence of silica in the epidermis, tector trichomes, hypostomatic leaves, stomatic crests, dorsiventral mesophyll, presence of collenchyma and vascular bundles were associated with adaptive strategies of the plants to the environment of Amazonian savanna. The anatomic characters presented here are of great importance for the species that live in savanna environments, demonstrating plasticity and contributing to the protection of the leaves to the diverse biotic and abiotic factors to which they are subject, ensuring thus the survival of the species. We demonstrate that plant species structure of Amazonian savanna is most likely shaped by environment determinism, and this fact has implications on how we expect such plants evolve in a climate changing world.