• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 3
  • 1
  • 1
  • 1
  • Tagged with
  • 6
  • 3
  • 2
  • 2
  • 2
  • 2
  • 2
  • 2
  • 2
  • 1
  • 1
  • 1
  • 1
  • 1
  • 1
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Pharmacological properties of members of the Sterculiaceae.

Reid, Kirsty Ann. January 2002 (has links)
There is a resurgence of interest in many countries in medicinal plants and their curative properties (HARBORNE & BAXTER, 1993). Little work has previously been conducted on the Sterculiaceae species, especially those located within South Africa. This was a perfect opportunity to broaden the available information on the medicinal properties and chemical constituents of this family, within KwaZulu-Natal. Of the 50 genera of the Sterculiaceae family, six are located in South Africa: Cola, Oombeya, Hermannia, Melhania, Sterculia and Waltheria . Seven Sterculiaceae species were chosen for investigation. They varied in growth type and use in traditional medicine. These species included: Oombeya rotundifolia, D. burgessiae, D. cymosa, Cola natalensis, C. greenwayi, Hermannia depressa and Sterculia murex. Plant material used in the study was collected from a variety of areas, all within KwaZulu-Natal or the Northern Province. There were two collection sites for D. rotundifolia, from differing habitats, and results were compared. The material was screened pharmacologically for anti-bacterial activity using the disc-diffusion assay and Minimal Inhibitory Assay (MIC), and for antiinflammatory activity using the COX-1 assay. Only D. rotundifolia and C. natalensis were tested for anti-bacterial activity using the disc-diffusion assay as the disc-diffusion asay was found to show inconsistencies in the results obtained. Bacteria used included: Escherichia coli and Klebsiella pneumoniae being Gram-negative, and Micrococcus luteus, Staphylococcus aureus and Staphylococcus epidermidis being Gram-positive. D. rotundifolia exhibited activity, both anti-bacterial and bacteriostatic, in the leaf, twig and bark extracts from both collection sites. Only the water extract obtained from the leaf material of C.natalensis exhibited slight anti-bacterial activity against S. epidermidis. Minimal inhibitory concentration (MIC) values were determined using a microdilution assay (25 mg ml-1 serially diluted 50 % to 0.195 mg ml-1). Bacteria used in the screening were: B. subtilis, E. coli, K. pneumoniae and S. aureus. None of the water extracts showed any antibacterial activity. Good MIC values were exhibited by D. cymosa ethanolic leaf extracts, C. greenwayi leaf ethyl acetate extracts especially against K. pneumoniae (0.78 mg ml-1) and S. aureus (0.39 mg rnl-1) and H. depressa ethanol and ethyl acetate leaf, stem and root extracts. D. burgessiae and S. murex showed low activity, with insignificant MIC values. D. rotundifolia plant material yielded the highest anti-inflammatory activity of all the plant species, with the extracts from the Umgeni Valley Nature Reserve(UVNR) showing the best results. The lowest activity was recorded in the aqueous bark extracts (5% inhibition)and the highest from the ethanolic leaf extract (97% inhibition). D. cymosa extracts showed high activity in ethanolic leaf and twig extracts with low activity in all the other extracts. D. burgessiae, C. greenwayi and S. murex extracts showed high activity in both ethanolic and dichloromethane extracts from leaf and twig material. Activity occurred in the dichloromethane extracts of H. depressa obtained from the stem (78%) and root (81%) extracts. C. natalensis extracts showed insignificant activity. Plant material was phytochemically screened for alkaloids, saponins, tannins, cardiac glycosides and cyanogenic glycosides. No alkaloids were detected using pH-partitioning and no cyanogenic glycosides were observed (TLC sandwich method) in any of the extracts of the seven species screened. Using the gelatin salt-block test, tannins were found to be present in the leaf and twig material of D. rotundifolia, the leaf material of C. greenwayi and the leaf, stem and root material of H depressa. The froth test indicated that saponins were present in the leaf and twig material of D. rotundifolia and leaf, root and stem material of H. depressa. The haemolysis test indicated the presence of saponins in the D. rotundifolia bark material. Screening for cardiac glycosides detected cardienolides in the leaf, twig and bark material of D. rotundifolia, and bufadienolides were detected in D. rotundifolia , D. cymosa, D. burgessiae and S. murex. Five species screened were selected for isolation of active anti-bacterial compounds: D. rotundifolia, D. burgessiae, D. cymosa, C. greenwayi and H. depressa. Material was extracted by Soxhlet and isolation techniques employed were VLC, TLC separation, Sephadex LH-20 column chromatography and HPLC techniques. The isolated compounds were analysed by NMR and GCMS. All isolated compounds were fatty acids: Palmitic acid, Myristic acid, Lauric acid, Stearic acid, Acetic acid as welll as stearyl alcohol, eicosane and octadecane. The aqueous eaf extract of H. Depressa exuded a thick mucilage. The production of this mucilage from the H. depressa aqueous extract may have medicinal or commercial value. A technique to separate the mucilaginous extract from the leaf material was devised. After extraction, the extract was screened to determine its sugar content through gas chromatography. It was screened for its pharmacological properties: antibacterial and anti-inflammatory activity. The hydrolysing effect of -amylase and HCI on the extract was determined to find its potential use as a bulking agent for use as an appetite suppressant, laxative or against the effects of diarrhoea. It was concluded that the extract is not likely to break down easily in the human digestive system and may be effective against the three listed ailments . / Thesis (Ph.D.)-University of Natal, Pietermaritzburg, 2002.
2

Evaluation of antidiarrhoeal and toxicological properties of Hermannia Incana cav.: a South African medicinal plant

Appidi, Jaipal Reddy January 2010 (has links)
Hermannia incana Cav. (Sterculiaceae), known as sweet yellow bells, is a medicinal plant used by the people of the Eastern Cape for the treatment of stomach-ache and diarrhoea. It has purgative and diaphoretic effects. It is a prostrate herb with yellow flowers and sparsely hairy and slightly glandular leaves, occurring in grassland and marshes in the Eastern Cape Province of South Africa. Based on the ethnomedical uses of this plant, the research project was designed to evaluate its antidiarrhoeal and toxicological properties. An ethnobotanical study of plants used for the treatment of diarrhoea in the Eastern Cape Province was carried out, using a questionnaire which was administered to herbalists, traditional healers and rural dwellers. This survey indicated a total of 17 plant species from 14 families. Elephantorrhiza elephantine (Burch.) Skeels, Hermannia incana Cav., Pelargonium reniforme Curt., Alepidea amatymbica Eckl. & Zeyh. and Bulbine latifolia (L.f.) Roem. et Schult. were the most frequently mentioned and highly recommended plants for the treatment of diarrhoea by both the traditional healers and rural dwellers. The root, bark and leaves are the common parts of plants used, while decoctions and infusions are the main methods of preparation. The agar dilution method was used to study the antimicrobial activity. The methanol extracts of the plant showed appreciable activity against Gram-positive and Gram-negative bacteria at concentrations ranging from 0.5 to 7.0 mg/ml. The acetone and water extracts of both the leaves and the roots showed moderate activity against Gram positive bacteria and less activity against Gram negative bacteria. All the extracts inhibited the growth of the fungi Aspergillus flavus, Aspergillus niger, and Mucor hiemalis with growth inhibition ranging from 54.31 percent to 96.67 percent at 0.1-10 mg/ml. None of the extracts suppressed the growth of Candida albicans at the maximum concentration (10 mg/ml) tested. iii In the in vivo antidiarrhoeal evaluation using Wistar rats, the aqueous extract at all the doses tested, significantly prolonged the time of induction of diarrhoea and also reduced the frequency of diarrhoeal episodes and fecal parameters (total number, number of wet, fresh and dry weight and water content of the faeces). The percentage inhibition of defecation and intestinal content (enteropooling) were increased in dose dependent manner. The doses also reduced the intestinal transit time of charcoal, masses and volumes of intestinal fluid (gastrointestinal motility). These results are indications of antidiarrhoeal property of H. incana leaf extract with the 600 mg/kg body weight of the extract being the most effective. In the toxicological evaluation using Wistar rats, the oral administration of the extract did not produce any significant effect on the liver and kidney body weight ratios, RBC, HB, PCV, MCV MCH, MCHC, RCDW, WBC, neutrophils, monocytes and basophils cholesterol, triacylglycerol, high-density lipoprotein cholesterol, low-density lipoprotein cholesterol and atherogenic index. The extract also did not affect the levels of sodium, potassium, chloride, inorganic phosphorus, urea, creatinine, total protein, globulin, albumin, total and conjugated bilirubin. The activities of alkaline phosphatase, gamma glutamyl transferase and alanine aminotransaminase in the serum were increased by the extract whereas aspartate aminotransaminase was decreased. The levels of LUC, platelets, lymphocytes and eosinophils were significantly affected at 600 mg/kg body weight. The available evidence in this study suggests that the extract of H. incana leaf is mild, parameter and dose specific. The structure and distribution of foliar appendages on the leaves of this plant were investigated with the JEOL (JSM-6390LV) scanning electron microscope (SEM). Both glandular and non-glandular trichomes were observed. Long stalked glandular trichomes were present on both the abaxial and adaxial surfaces while short stalked glandular trichomes were present only on the adaxial surface. Glandular trichomes were capitate while nonglandular trichomes were stellate with many arms. Energy dispersive X-ray spectroscopyiv SEM showed that Al, Ca, K, Na, Ti and Si were the major constituents of the crystals analyzed from the leaf surfaces. The phytochemical screening of H. incana revealed the presence of bioactive antidiarrhoeal agents such as alkaloids, tannins, saponins, phenolics, triterpenes, cardiac glycosides, flavonoids, cardenolides and dienolides. Two flavonoids, epicatechin and 3, 5, 7, 2’ tetra-hydroxy flavone-3- O--D-glucopyranoside were isolated from the leaves of the plant through bio-active guided fractionation. Both these compounds were screened against diarrhoea causative organisms (Echerichia coli, Shigella flexneri, Bacillus cereus and Staphylococcus aureus) and exhibiting minimum inhibitory concentrations ranging from 12.5 to 100 μg/ml. The findings from this research have generally justified the traditional use of this plant for the treatment of diarrhoea in this province.
3

Lupinus lanatus Benth, Lupinus guaraniticus (Hassl.) C. P. Sm., Lupinus paranensis C. P. Sm. (Fabaceae) e Waltheria douradinha Saint Hilaire (Sterculiaceae): Isolamento e Identificação de seus Metabólitos e Atividade Biológica / Lupinus lanatus Benth, Lupinus guaraniticus (Hassl.) C. P. Sm.,Lupinus paranensis C. P. Sm. (Fabaceae) e Waltheria douradinhaSaint Hilaire (Sterculiaceae): Isolation and Identification of Biological Activity and its Metabolites

Tiburski Neto, Alexandre 31 July 2015 (has links)
Conselho Nacional de Desenvolvimento Científico e Tecnológico / The part of our constant search for new bioactive secondary metabolites of plant origin, the aerial parts of three species of the genus Lupinus (Leguminoseae), and the bark of the roots of the species Waltheria douradinha Sain Hilaire (Sterculiaceae), were submitted to phytochemical investigation. In this research, they were isolated and identified 14 compounds, which was exposid several biological activities. Among the activities performed, the compounds were evaluated against antimicrobial, antioxidant enzyme (POP and DPPIV) and also bacteriolityc activity. Two of the isolated compounds, (+)Lanatina A (L. paranensis) and Antidesmona (W. douradinha) shawed bacteriolityc activity. The test showed that these compounds have bacteriolityc activity, especially against Gram-negative. The Antidesmona presented better lytic potential in the concentration of 12.5 μg/mL against the microorganism Salmonella typhimurium ATCC 14028. For this bacterium, Antidesmona alkaloid produced a cell wall lysis of approximately 30% between 4-6 hours (P <0.0001). The alkaloid extracts W. douradinha, collected in four different regions of Rio Grande do Sul - Brazil, was analyzing its chemical composition by HPLC. Analysis of the chemical composition of the basic extracts was compared with soil analyzes the place collection of plant. These results revealed significant differences in the chemical compositions of alkaloid extracts of Waltheria douradinha Sain Hilaire and were important guides of new collection sites these species. / Como parte da nossa busca permanente por novos metabólitos secundários bioativos, de origem vegetal, as partes aéreas de três espécies do gênero Lupinus, (Leguminoseae), e a casca das raízes da espécie Waltheria douradinha Sain Hilaire (Sterculiaceae), foram submetidas à investigação fitoquímica. Dessa investigação, foram isolados e identificados 14 compostos, os quais foram submetidos a diversas atividades biológicas. Dentre as atividades realizadas, os compostos foram avaliados frente a atividades antimicrobiana, antioxidante, enzimáticas (POP e DPPIV) e também atividade bacteriolítica. Dois dos compostos isolados, (+)Lanatina A (L. paranensis) e Antidesmona (W. douradinha), foram submetidos a atividade bacteriolítica. O teste demonstrou que esses compostos possuem atividade de lise, principalmente frente a Gram-negativos. A Antidesmona apresentou seu melhor potencial lítico na concentração de 12,5 μg/ml frente ao microrganismo Salmonella typhimurium ATCC 14028. Para esta bactéria, o alcaloide Antidesmona produziu uma lise de parede celular de aproximadamente 30% entre 4 e 6 horas (P<0,0001). Os extratos alcaloídicos de W. douradinha, coletada em quatro diferentes regiões do Rio Grande do Sul Brasil, passaram por análise de sua composição química por HPLC. A análise da composição química dos extratos básicos foi comparada com análises do solo do local de coleta da planta. Esses resultados revelaram diferenças significativas nas composições químicas dos extratos alcaloídicos de W. douradinha, e também foram importantes guias de novos locais de coleta dessa espécie.
4

Estudo fitoquímico de Helicteres velutina K. Schum (Sterculiaceae) e avaliação do seu potencial larvicida contra Aedes aegypti L. (Diptera: Culicidae)

Fernandes, Diégina Araújo 22 February 2017 (has links)
Submitted by Maike Costa (maiksebas@gmail.com) on 2017-09-11T14:23:26Z No. of bitstreams: 1 arquivototal.pdf: 4539317 bytes, checksum: 8b0c70f7cf6924075fe039736b510527 (MD5) / Made available in DSpace on 2017-09-11T14:23:26Z (GMT). No. of bitstreams: 1 arquivototal.pdf: 4539317 bytes, checksum: 8b0c70f7cf6924075fe039736b510527 (MD5) Previous issue date: 2017-02-22 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / Natural products have been used by humankind since immemorial times to relieve and cure severals diseases, and the ethnic-pharmacology knowledge of plant species has aroused interest in research aimed at the discovery of bioactive molecules. The emergence of new diseases transmitted by Aedes aegypti L., linked to resistance to larvicides and insecticides in the market, makes it necessary to search for alternatives to vector combat. In this context the Brazil stands out because it has a great potential of natural resources that lead to the development of native flora bioproducts.Within this diversity was sought through a pioneering study from view point chemical and biological of the ethanolic extract gross obtained from the aerial parts of the species Helicteres velutina K. Schum (Sterculiaceae), commonly know in Brazil as “pitó” is popularly used by the tribe indigenous Pankararé in Bahia, as insect repellent, isolate and identify their chemical constituents, as well evaluate their larvicidal potential.For the phytochemical study, the ethanolic extract gross was solubilized in EtOH:H2O (7:3) and partitioned with Hex.; CH2Cl2; AcOEt; n-BuOH, obtaining their respective phases, in addition to the hydroalcoholic phase. 8g of the dichloromethane phase was subjected to column chromatography using silica flash and/or Sephadex-LH 20 as stationary phases.This chromatographic process led to the apartness of five chemical constituents, whose chemical structures were defined by the interpretation of infrared, RMN 1H e 13C spectra and 2D, as well as comparisons with literature models. The isolated substances were three flavonoids: Hv-1 - 3,5,7,4'-tetrahydroxyflavone (Kaempferol); Hv-2 - Kaempferol-3-O-β-D-(6´´-E-p-coumaroyl) glucopyranoside (Tiliroside); Hv-3 - 7,4’-di-O-methyl-8-O-sulphateflavone (Isoscutellarein sulphate); one triterpene from the series oleanane - Hv-4 – Acid 3β-hydroxy-olean-12-en-28-oic (Oleanolic acid); and a steroid - Hv-5 - Sitosterol-3-O-D- glucopyranoside (β-sitosterol glycosylated). A preliminary study to evaluate the larvicidal activity of the ethanolic extract gross of the aerial parts of Helicteres velutina demonstrated excellent activity against larvae in the L4 stage of Aedes aegypti, with the 10.000 ppm dose dose of killing 100% of the larvae after 24 h of exposure and the CL50 was estimated to be 2.983 ppm according to Tukey's test, thus characterizing itself as a promising alternative to be used in an integrated control system of this vector, which demands the continuity of its studies. / Os produtos naturais são utilizados pela humanidade desde tempos imemoriais com intuito de alivio e cura de diversos males, tendo o conhecimento etnofarmacológico das espécies vegetais despertado interesse em pesquisas voltadas para descoberta de moléculas bioativas. O surgimento de novas doenças transmitidas pelo Aedes aegypti L., atrelado a resistência a larvicidas e inseticidas existentes no mercado, tornam necessário a busca por alternativas de combate ao vetor. Neste contexto o Brasil se destaca por possuir um grande potencial de recursos naturais que levam ao desenvolvimento de bioprodutos a partir da flora nativa. Dentro desta diversidade buscou-se através de um estudo pioneiro do ponto de vista químico e biológico do extrato etanólico bruto obtido das partes aéreas da espécie Helicteres velutina K. Schum (Sterculiaceae), conhecida popularmente no Brasil como “pitó” e usada tradicionalmente pela tribo indígena Pankararé na Bahia, como repelente de insetos, isolar e identificar seus constituintes químicos, bem como avaliar o seu potencial larvicida. Para o estudo fitoquímico, o extrato etanólico bruto foi solubilizado em EtOH:H2O (7:3) e particionado com Hex.; CH2Cl2; AcOEt; n-BuOH, obtendo-se suas respectivas fases, além da fase hidroalcoólica. 8,0 g da fase diclorometano foi submetida a cromatografia em coluna utilizando como fases estacionárias sílica flash e/ou Sephadex-LH 20. Este processo cromatográfico levou ao isolamento de cinco constituintes químicos, cujas estruturas químicas foram definidas por interpretação dos espectros de Infravermelho, RMN 1H e 13C e bidimensionais, além de comparações com modelos da literatura. As substâncias isoladas foram três flavonoides: Hv-1 - 3,5,7,4'-tetrahidroxiflavona (Canferol); Hv-2 - Canferol-3-O-β-D-(6”-E-p-cumaroil) glicopiranosídeo (Tilirosídeo); Hv-3 - 7,4’-di-O-metil-8-O-sulfatoflavona (Isoscutelareina sulfatada); um triterpeno da série oleanano - Hv-4 - Ácido 3β-hidroxi-olean-12-en-28-óico (Ácido oleanólico); e um esteroide - Hv-5 - Sitosterol-3-O-D-glicopiranosídeo (β-Sitosterol glicosilado). Um ensaio preliminar para avaliar a atividade larvicida do extrato etanólico bruto das partes aéreas de Helicteres velutina demonstrou excelente atividade frente a larvas no estágio L4 de Aedes aegypti, sendo a dose de 10.000 ppm capaz de matar 100% das larvas após 24 h de exposição e a CL50 estimada em 2.983 ppm segundo teste de Tukey, caracterizando-se, portanto, em uma alternativa promissora para ser utilizada em um sistema de controle integrado desse vetor, o que demanda a continuidade dos seus estudos.
5

PALINOTAXONOMIA DAS TRIBOS BYTTNERIEAE, HERMANNIEAE E HELICTEREAE (MALVACEAE s. l.) DA FLORA DA BAHIA, BRASIL

Saba, Marileide Dias 16 December 2002 (has links)
Made available in DSpace on 2015-07-15T13:31:42Z (GMT). No. of bitstreams: 1 1dissertacao-capa.pdf: 85499 bytes, checksum: 93abb32e87de260a937eca45af655983 (MD5) Previous issue date: 2002-12-16 / Palinotaxonomicaly, 27 species of the tribe Byttnerieae, Hermannieae and Helictereae (Malvaceae s. l.) from Bahia State were studied with aim of to increase alow knowledge pollen morphology and to contribute with a taxonomic delimitation of the taxa. The pollen material were acetolysed, analyzed and photographed under light and scanning electron microscopic. Four pollen types are recognized based in exine ornamentation and apertural type: (I) pollen grains (2)3(4)-porate, aspidate, planaperturate, (micro)reticulate exine, whose are representated by the tribe Byttnerieae (Ayenia L., Byttneria L. and Rayleya Crist?bal); (II) pollen grains (2)3-colporate, microreticulate exine, constitute only by Guazuma ulmifolia Lam. (tribe Byttnerieae); (III) pollen grains 3 to 8-colporate, suprareticulate or spinulose exine, represented by Melochia L. and Waltheria L. of the tribe Hermannieae; (IV) pollen grains (2)3(4)-porate, no aspidate, angulaperturate, verrucate or spinulose exine in the species of the tribe Helictereae (Helicteres L.). In the tribe Byttnerieae was observed that Ayenia, Byttneria and Rayleya form a palinotaxonomic complex very homogeneous and in Byttneria and Rayleya were closed related because the reticulate ornamentation of exine. In the tribe Hermannieae, the pollen dimorphism associated the heterostyly of the Melochia and Waltheria species corroborated their proximity. In the tribe Helicterieae, the differentiated morphologic caracterization of Helicteres pollen grains support its taxonomic position in the tribe. The results demonstrated the taxonomic importance of pollen morphology studies corroboring with the subdivision of the taxa subordinates in this tribes. / Neste trabalho ? apresentado o estudo palinotaxon?mico de 27 esp?cies das tribos Byttnerieae, Hermannieae e Helictereae (Malvaceae s. l.) que ocorrem no Estado da Bahia, com o objetivo de ampliar o conhecimento da morfologia pol?nica e contribuir para a melhor delimita??o dos t?xons a? inclu?dos. Os gr?os de p?len foram acetolisados, analisados sob microscopias ?ptica e de varredura, descritos e ilustrados por meio de fotomicrografias e eletromicrografias. Considerando a ornamenta??o da exina e o tipo apertural, foram reconhecidos quatro tipos pol?nicos: (I) gr?os de p?len (2)3(4)-porados, aspidados, planaperturados, exina (micro)reticulada, cujos representantes pertencem ? tribo Byttnerieae (Ayenia L., Byttneria L. e Rayleya Crist?bal); (II) gr?os de p?len (2)3-colporados, exina microrreticulada, constitu?do apenas por Guazuma ulmifolia Lam. (tribo Byttnerieae); (III) gr?os de p?len 3 a 8 colporados, exina suprarreticulada ou espiculada, representado pelos g?neros da tribo Hermannieae (Melochia L. e Waltheria L.); (IV) gr?os de p?len (2)3(4)-porados, n?o aspidados, angulaperturados, exina verrucada ou espiculada, presentes nas esp?cies da tribo Helictereae (Helicteres L.). Na tribo Byttnerieae, observou-se que Ayenia, Byttneria e Rayleya formam um complexo palinotaxon?mico muito homog?neo, no qual as esp?cies de Byttneria e Rayleya se aproximam pela ornamenta??o da exina reticulada. Na tribo Hermannieae, o dimorfismo pol?nico associado ? heterostilia apresentado pelas esp?cies de Melochia e Waltheria corrobora a proximidade desses g?neros. Enquanto que na tribo Helictereae, a caracteriza??o morfol?gica diferenciada dos gr?os de p?len de esp?cies estudadas de Helicteres sustentam o posicionamento taxon?mico a parte desse g?nero.Pelos resultados obtidos, pode-se afirmar que a morfologia pol?nica tem import?ncia taxon?mica e corrobora a subdivis?o dos t?xons subordinados a estas tribos.
6

Ecologie et évolution de la dioécie et du dimorphisme sexuel de la taille des fleurs chez les "dombeya"(sterculiacées) endémiques de La Réunion

Humeau, Laurence 09 February 1999 (has links) (PDF)
Les forts taux d'espèces dioïques sur les îles ont longtemps fasciné les biologistes. Or le fonctionnement de la dioécie en milieu insulaire a été peu abordé. Les variations dans l'expression de la dioécie et du dimorphisme sexuel de la taille des fleurs sont aujourd'hui examinés dans l'archipel des Mascareignes. A la réunion, les espèces unisexuées du genre "Dombeya" (sterculiacées) sont dioïques cryptiques mais présentent une variabilité dans l'expression de la dioécie. Certaines espèces strictement dioïques constituent de grandes populations en altitude alors que les espèces partiellement dioïques forment de petites populations à basse altitude. Par ailleurs, l'hybridation entre espèces strictement dioïques et partiellement dioïques semble engendrer des taxons hermaphrodites autocompatibles. Ces résultats demandent confirmation par une étude moléculaire plus poussée, mais l'hybridation en milieu insulaire semble être un processus évolutif important dans ce genre. Nos résultats montrent que le dimorphisme sexuel de la taille des fleurs de la flore unisexuée indigène de la Réunion est un phénomène largement répandu. Le biais observé est souvent en faveur des individus mâles, ce qui peut être corrélé à la zoogamie, fréquente sur cette île. Le dimorphisme est plus abondant chez les espèces endémiques que chez les taxons indigènes et est variable entre les espèces apparentées. Un modèle allométrique est proposé pour illustrer ces variations au sein du genre "Dombeya". Cette thèse apporte les connaissances de base sur la biologie du genre "Dombeya" à la Réunion dont certaines espèces constituent les éléments clés des forêts primaires et d'autres sont des espèces rares des milieux fragmentés.

Page generated in 0.0591 seconds