The essential oils from leaves and inflorescences of Lippia origanoides Kunth present aromatic and medicinal potential and have been used to treat several diseases, including melanoma. In Brazil, L. origanoides is commonly found in campo cerrado and cerrado stricto sensu, physiognomies featured mainly by the differential light conditions to which short and medium-sized plants are subjected. Our aim was to investigate the glandular trichome density and the yield and chemical composition of the essential oils in leaves and inflorescences of L. origanoides from campo cerrado and cerrado stricto sensu. For glandular density analysis, leaves and inflorescences were processed according to conventional techniques for scanning electron microscopy. The essential oils of leaves and inflorescences were obtained by hydrodistillation and identified with gas chromatography. Bracts and sepals showed the highest glandular density, followed by petals and leaves. The glandular density in the abaxial leaf surface was higher in individuals from the campo cerrado. In both populations the essential oil yield was higher in inflorescences than in leaves. The chemical composition of the essential oils varied among individuals from different areas and inside a same population. Our results demonstrated the chemical plasticity of L. origanoides suggesting the importance of monitoring its popular use.
Despite the ecological and medicinal importance of glandular trichomes in Verbenaceae, information on their structure, mainly at the subcellular level, is sparse. We analyzed the morphology and histochemistry of glandular trichomes in Lippia origanoides Kunth and Lippia stachyoides Cham., using conventional methods in anatomy, histochemistry, scanning and transmission electron microscopy, and ultracytochemical techniques. Five morphotypes (I–V) of glandular trichomes were identified in L. origanoides, and four morphotypes (I, III–V) in L. stachyoides. Morphotype I is the most abundant in both species. Lipids were detected in all morphotypes except IV; terpenes in I, II, and V; phenolic compounds in all morphotypes except V; neutral polysaccharides and protein in all morphotypes; mucilage exclusively in IV; alkaloids only in III. Each glandular morphotype showed ultrastructural peculiarities compatible with the chemical compounds produced. An association between glandular morphotype, secretion composition, and ultrastructural features in Lippia species was revealed, suggesting functions specific to each glandular morphotype.
Leaf-cutter ants are the most important pest insect in agriculture. Their association with Ocimum species is common in Brazil. O. gratissimum presents three morphotypes of glandular trichomes producing compounds with anti-herbivore properties. Under an experimental approach, we found significant alterations in O. gratissimum volatile oil composition after leaf-cutter ant attacks. The total density of glandular trichomes increased in attacked plants; however, we bring novelties in the sense that we observed differential responses to each glandular morphotype. This could be related to the specific substances produced by each trichome morphotype, contributing to the idea of functional compartmentalization in plant defense.
Lamiaceae contains many species known for their aromatic properties that are produced by the production of essential oils in glandular trichomes. Hyptis is one of the most common genera of Lamiaceae in the Brazilian fl ora, and includes several species with medicinal value. However, studies on the morphology and functioning of their glandular trichomes are lacking. We analyzed the morphology, histochemistry and ultrastructure of the glandular trichomes in leaves of H. villosa, emphasizing the diff erential distribution of actin fi laments and microtubules in cells secreting hydrophilic and lipophilic compounds. Four morphotypes of glandular trichomes were identifi ed. Total lipid, terpenes, alkaloids, phenolic compounds, proteins and polysaccharides were histochemically detected in all morphotyes. Th is evidences the mixed nature of the secretions of this species, although there are diff erences in the prevalence of lipophilic and hydrophilic components among the glandular morphotypes and among the cells of the same trichome. Th e actin microfi laments are more abundant in cells that secrete mainly hydrophilic compounds, and microtubules predominate in cells that secrete lipophilic compounds. Our results corroborate the correlation between the glandular morphotype and the composition of the secretion produced, with a diff erential distribution of the cytoskeletal elements according to the prevalence of either hydrophilic or lipophilic substances.
Lantana camara L. is a species of Verbenaceae known for its aromatic and medicinal properties. Compounds extracted from its leaves are used to treat infections of the respiratory tract and have demonstrated antimicrobial potential and repellent action to Aedes mosquitoes. Our aim was to identify and characterize the main production sites of the biologically active substances in the leaf blades of L. camara. Leaf samples were collected from plants living in the Brazilian Cerrado and processed according to standard techniques in plant anatomy and histochemistry as well as scanning and transmission electron microscopy. Six morphotypes of glandular trichomes (I–VI) were identified; they differ in shape and size, number of constituent cells, subcellular aspects, and form of accumulation, as well as release and composition of the secretion. Idioblasts producing hydrophilic and lipophilic substances were observed in the mesophyll and may be associated with protection of the plant against herbivores and pathogens and maintenance of the water potential of leaf tissues, complementing the action of glandular trichomes. Our results contribute to the understanding and knowledge of the sites responsible for the production of substances with ecological and medicinal value in Verbenaceae species, and may provide a foundation for future studies in different areas of science focusing on the manipulation of this production.
The present study investigated whether osmotic stress induced by the exposure of peppermint (Mentha x piperita L.) to moderate and severe stress for short periods of time changes the plant's physiological parameters, leaf anatomy and ultrastructure and essential oil. Plants were exposed to two levels of polyethyleneglycol (50 g L(-1) and 100 g L(-1) of PEG) in a hydroponic experiment. The plants exposed to 50 g L(-1) maintained metabolic functions similar to those of the control group (0 g L(-1)) without changes in gas exchange or structural characteristics. The increase in antioxidant enzyme activity reduced the presence of free radicals and protected membranes, including chloroplasts and mitochondria. In contrast, the osmotic stress caused by 100 g L(-1) of PEG inhibited leaf gas exchange, reduced the essential oil content and changed the oil composition, including a decrease in menthone and an increase in menthofuran. These plants also showed an increase in peroxidase activity, but this increase was not sufficient to decrease the lipid peroxidation level responsible for damaging the membranes of organelles. Morphological changes were correlated with the evaluated physiological features: plants exposed to 100 g L(-1) of PEG showed areas with collapsed cells, increases in mesophyll thickness and the area of the intercellular space, cuticle shrinkage, morphological changes in plastids, and lysis of mitochondria. In summary, our results revealed that PEG-induced osmotic stress in M. x piperita depends on the intensity level of the osmotic stress applied; severe osmotic stress changed the structural characteristics, caused damage at the cellular level, and reduced the essential oil content and quality.
ABSTRACT. Numerous plant species are easily established in the wide flood plains of the Pantanal wetlands due to the environmental heterogeneity. The aquatic macrophytes excel in permanently flooded areas, particularly Nymphaeaceae species. Victoria amazonica, popularly known as the vitória-régia, is hallmarked for its beauty. However, the biology and conditions necessary for the seed germination of this flowering plant remain unknown. In the present study, the fruit and seed morphology and biometry were described and the seed germination was evaluated under different abiotic conditions. To this end, mature fruits of V. amazonica were collected from the bays near Paraguay River in the south Pantanal floodplain. The fruits and seeds were described and measured using digital caliper. Intact and mechanically scarified seeds were germinated under different temperature, light and substratum conditions, and the initial development was described. The fruits measured 67.5 x 119.7 mm in size and contained 100-700 seeds. The average seed measured 10.6 mm in length and 9.8 mm in width. The highest germination occurred at 25 o C, independent of the light condition. The seeds were considered neutral photoblastic. The seedlings showed heterophylly, and the main root was degenerated, forming adventitious roots. Morphological differences were observed in seedlings developed under different light conditions. Keywords: aquatic macrophyte, hydrophytes, water lilies, vitória-régia.Biometria do fruto e da semente e germinação de Victoria amazonica (Poepp.) J.C. Sowerby (Nymphaeaceae) do Pantanal RESUMO. O Pantanal, ampla planície inundável, facilita o estabelecimento de inúmeras espécies vegetais por sua heterogeneidade ambiental. As macrófitas aquáticas se destacam em áreas permanentemente alagadas, com destaque para a família Nymphaeaceae. A espécie Victoria amazonica, conhecida popularmente como vitória-régia, é marcada por sua beleza. Entretanto, sua biologia e as condições necessárias à germinação de suas sementes permanecem desconhecidas. Nesse estudo foram descritas a biometria e a morfologia do fruto e da semente, e avaliada a germinação em diferentes condições abióticas. Para isso, frutos de V. amazonica foram coletados em baias próximas ao rio Paraguai no Pantanal sul. Os frutos e as sementes foram descritos e mensurados usando paquímetro digital. Sementes íntegras e escarificadas mecanicamente foram submetidas a testes de germinação em diferentes condições de temperatura, luz e substrato, e o desenvolvimento inicial das plântulas foi descrito. Os frutos mediram 67,5 x 119,7 mm, e portavam 100-700 sementes. As sementes mediram 10,6 mm de comprimento e 9,8 mm de largura em média. A maior porcentagem de germinação ocorreu a 25 o C independente da condição de luz. As sementes foram consideradas fotoblásticas neutras, e as plântulas possuem heterofilia, degeneração da raiz principal e formação de raízes adventícias. Foram observadas diferenças morfológicas nas plântulas desenvolvidas na presença e na ausência de luz.Palavras-c...
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