Structural and histochemical attributes of secretory ducts and cavities in leaves of four species of Calophyllaceae J. Agardh in Amazonian savannas

Morphology, anatomy, and histochemistry of three species of Jatropha: a contribution to plant recognition and selection

Jatropha, a traditional medicinal plant known for its anti-inflammatory, antimicrobial, anticancer, antiviral, antidiabetic, and anticoagulant properties, was the subject of our study. We examined the morphology and chemical composition of three Jatropha species using cross- and longitudinal sections of fresh samples, observed with light microscopy. Histochemical analysis was conducted using various reagents to reveal the metabolites present. Anatomically, the distinguishing feature among the three Jatropha species was the presence of secretory cavities. These structures were identified in the petiole and stem bark of J. multifida, while in J. gossypiifolia and J. curcas they were present in roots. The stem bark cells of J. gossypiifolia were roundish in shape, whereas the others were rectangular. Laticifers were detected in the leaves, petioles, and stem bark of all three Jatropha species, while idioblasts were present in almost all organs. Histochemical tests revealed that excretory idioblasts and laticifers in Jatropha species contained alkaloids, phenolics, lipophilic compounds, and terpenoids. The cuticle of non-glandular trichomes contained terpenoids, while phenolic compounds were found within the secretory cavities. These findings contribute to the identification of Jatropha species and provide valuable insights for the selection and collection of specific plant organs containing bioactive compounds.

Anatomical traits related to leaf and branch hydraulic functioning on Amazonian savanna plants

Amazonian savannas are isolated patches of open habitats found within the extensive matrix of Amazonian tropical forests. There remains limited evidence on how Amazonian plants from savannas differ in the traits related to drought resistance and water loss control. Previous studies have reported several xeromorphic characteristics of Amazonian savanna plants at the leaf and branch levels that are linked to soil, solar radiation, rainfall and seasonality. How anatomical features relate to plant hydraulic functioning in this ecosystem is less known and instrumental if we want to accurately model transitions in trait states between alternative vegetation in Amazonia. In this context, we combined studies of anatomical and hydraulic traits to understand the structure-function relationships of leaf and wood xylem in plants of Amazonian savannas. We measured 22 leaf, wood and hydraulic traits, including embolism resistance (as P₅₀), Hydraulic Safety Margin (HSM) and isotope-based water use efficiency (WUE), for the seven woody species that account for 75% of the biomass of a typical Amazonian savanna on rocky outcrops in the state of Mato Grosso, Brazil. Few anatomical traits are related to hydraulic traits. Our findings showed wide variation exists among the seven species studied here in resistance to embolism, water use efficiency and structural anatomy, suggesting no unique dominant functional plant strategy to occupy an Amazonian savanna. We found wide variation in resistance to embolism (-1.6 ± 0.1 MPa and -5.0 ± 0.5 MPa) with species that are less efficient in water use (e.g. Kielmeyera rubriflora, Macairea radula, Simarouba versicolor, Parkia cachimboensis and Maprounea guianensis) showing higher stomatal conductance potential, supporting xylem functioning with leaf succulence and/or safer wood anatomical structures and that species that are more efficient in water use (e.g. Norantea guianensis and Alchornea discolor) can exhibit riskier hydraulic strategies. Our results provide a deeper understanding of how branch and leaf structural traits combine to allow for different hydraulic strategies among coexisting plants. In Amazonian savannas, this may mean investing in buffering water loss (e.g. succulence) at leaf level or safer structures (e.g. thicker pit membranes) and architectures (e.g. vessel grouping) in their branch xylem.

New Aspects of Secretory Structures in Five Alismataceae Species: Laticifers or Ducts?

The secretory structures of Alismataceae have been described as secretory ducts, laticifer ducts, laticifer canals or schizogenous ducts. However, these terms are not found in the specialized literature, and ontogenetic analyses for the exact classification of these structures are missing. Accordingly, more studies regarding the secretory structures of Alismataceae are necessary to establish homology in the family or in the order. Thus, the aim of this study was to describe the anatomy, ontogeny, distribution in the organs and exudate composition of the secretory structures present in five Alismataceae species in order to determine whether the family has laticifers or secretory ducts. Samples of leaves, flowers and floral apices were processed for anatomical and histochemical analyses by light microscopy. The analysis indicated the presence of anastomosing secretory ducts in all species, occurring in both leaves and flowers. The exudate contains lipids, alkaloids, proteins and polysaccharides, including mucilage. The secretory duct structure, distribution and exudate composition suggest a defense role against herbivory and in wound sealing. The presence of secretory ducts in all species analyzed indicates a probable synapomorphy for the family.