Monoecy, the production of distinct male and female flowers on the same plant, is an important, though little studied, sexual strategy in the rainforest understory. This study of a monoecious plant discovered a cue to induce flowering, explored the interplay of gender constraint vs. plasticity in a natural population, and tested possible causes of gender in two laboratory experiments. An experiment in the lab found that reduced photoperiod for three weeks is an unambiguous cue for flowering. The remarkably long inductive period is followed by a long and variable period of floral initiation. This results in only partial synchronization of flowering among plants in a patch, which enhances mating opportunities in this protandrous plant. Inflorescence architecture is highly constrained, and ideally produces a phenotypic gender (proportion female) of about 0.5. However, in the forest at Las Cruces, Costa Rica, most plants were less female than predicted, mostly through abortion of female buds. Plants showed gender plasticity between and within years. Large plants produced more flowers and were more female in gender, and less variable in gender, than small plants. Reproduction was poorly correlated with environmental resource availability, measured as canopy openness, soil moisture, pH, and soil phosphorus, ammonium and nitrate. Phenotypic selection analysis on seed production suggests an optimal gender of 50-60% female, yet plasticity to be less female than this optimum, and in particular to express only male function, has been maintained. In a factorial experiment in the lab, high light or high nitrogen caused plants to produce more flowers and to be proportionally more female, and larger in weight, than low light or nitrogen. The effects of light and nitrogen on reproduction, plant size, and leaf greenness suggest an energy based determination of gender. Gender may be mostly influenced by plant size, but sometimes also opportunistically by environment. Inoculation with mycorrhizas caused plants to be less female in gender, and smaller in weight, than plants that were not inoculated. This suggests a net cost of mycorrhizas under experimental conditions, and supports the emerging view of the mycorrhizal symbiosis as not necessarily mutualistic under all circumstances.

Aciphylla species (wild spaniard/speargrass) are an iconic component of the Australasian high country flora, but their reproductive system is enigmatic. They are insect-pollinated dioecious mast seeders (synchronous highly variable seed production), which seems maladaptive. The resource supply to pollinators is highly variable, yet dioecious plants are dependent on pollinators, and dioecious masting requires male and female plants to flower synchronously. Floral display in Aciphylla is relatively large, with tall inflorescences bearing thousands of flowers, suggesting that plants would not have the resources to produce such large stalks every year. But why do they have such huge inflorescences in the first place? I tested whether pollinator attraction is providing an economy of scale which favours intermittent production of very large inflorescences, by manipulating floral display size during a high-flowering year and measuring insect visitation rates and seed set (female reproductive success). Using space-for-time substitution and selective removal of male inflorescences, I also tested whether female seed set was affected by distance to flowering male plants (i.e. changes in local pollen availability) to see if flowering asynchrony would reduce pollination success. Bags were used to exclude pollination by insects and test for wind pollination, and hand pollination was done to test for pollen limitation. Insect surveys suggest that Aciphylla has a generalist pollination system (to avoid satiating a specialist pollinator during 'mast' years'). Male inflorescences received significantly more visits than females, and some seeds were set inside bags (although only 20-30%), suggesting wind pollination may occur at low levels. Seed set rate was higher for taller inflorescences with greater flowering length in A. aurea but tall inflorescences with excess flowers led to a decrease in seed set rates in A. scott-thomsonii. Hand pollination significantly increased seed set rates although these effects were not as large as expected (e.g. 10% increases from natural to hand-pollinated inflorescences were typical). There was no evidence for resource limitation in any species. Female plants in dense flowering populations had higher seed set rates, and individual floral display size in females was particularly important when females were 'isolated' from males. Insect visitation rates were generally higher on inflorescences with a larger floral display, suggesting that display size is important for pollinator attraction. Overall, these results suggest that the pollinator-attraction benefits of such a large floral display (at both the plant and population level) are possibly providing an economy of scale, although the relative effects are small.

Submitted by Luciana Ferreira (lucgeral@gmail.com) on 2017-04-19T13:00:57Z No. of bitstreams: 2 Dissertação - Indiara Nunes Mesquita Fereira - 2017.pdf: 3205784 bytes, checksum: df9235a92accda62ab612fa76225c654 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Approved for entry into archive by Luciana Ferreira (lucgeral@gmail.com) on 2017-04-19T13:01:19Z (GMT) No. of bitstreams: 2 Dissertação - Indiara Nunes Mesquita Fereira - 2017.pdf: 3205784 bytes, checksum: df9235a92accda62ab612fa76225c654 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Made available in DSpace on 2017-04-19T13:01:19Z (GMT). No. of bitstreams: 2 Dissertação - Indiara Nunes Mesquita Fereira - 2017.pdf: 3205784 bytes, checksum: df9235a92accda62ab612fa76225c654 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Previous issue date: 2017-03-23 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / Abstract: Simarouba amara Aubl. is a dioecious species belonging to the family Simaroubaceae. Its occurrence is recorded from the wetlands of Costa Rica in Central America to the Center-West region of Brazil. It can reach up to 35 m high in the Amazonia Forest, where its occurrence may be very common. The great majority of the studies on the species refer to the pharmacological aspects inherent to the metabolic compounds present in the species of the family Simaroubaceae. There are also other approaches on their application in reforestation of degraded areas, and the commercial use of wood. However, studies on their reproductive biology are scarce. It is known that its sexual system is dioecious, which makes it depends on vectors to promote the flow of pollen between the individuals of different sexes. However, its system of pollination is still unknown. Studies suggest that in its wide distribution, the species presents phenotypic variations according to its environment of occurrence. The Cerrado is composed of a mosaic of vegetation submitted to differences in climate, relief and soil, which may favor the expression of phenotypic plasticity in some species. In this sense, the aim of this dissertation was initially to investigatethe reproductive biology of S. amara, involving aspects of floral biology, phenology, sexual and pollination system. In addition, we sought to investigate whether the species presents phenotypic variations in its morphology and reproductive system in distinct environments of the Cerrado, such as forest and cerrado sensu stricto. Therefore, the dissertation was structured in two chapters: in the first, the reproductive biology of Simarouba amara Aubl. (Simaroubaceae) was investigated in Semideciduous Forest of Central Brazil. In the second chapter, the variations in the reproductive biology of Simarouba amara Aubl. (Simaroubaceae) was analysed in the environment of Semideciduous Forest and cerrado sensu stricto. / Resumo: RESUMO Simarouba amara Aubl. é uma espécie dióica pertencente a família Simaroubaceae. Sua ocorrência é registrada desde as Matas Úmidas da Costa Rica na América Central até a região Centro-Oeste e Sudeste do Brasil. É uma espécie arbórea que pode atingir até 35 m de altura nas Matas de Terra Firme da Amazônia, onde sua ocorrência pode ser muito comum. A maioria dos estudos sobre a espécie se reporta aos aspectos farmacológicos inerentes aos seus compostos metabólicos. Há também outras abordagens sobre a qualidade de suas mudas, replantio em áreas degradadas, fenologia e o uso comercial da madeira. No entanto, estudos sobre a sua biologia reprodutiva são escassos. Sabe-se que seu sistema sexual é dióico, o que faz com que sua reprodução sexuada dependa de vetores que promovam o fluxo de pólen entre os indivíduos de sexos distintos, porém seu sistema de polinização também ainda é desconhecido. Estudos sugerem que em sua ampla distribuição, a espécie apresenta variações fenotípicas de acordo com o seu ambiente de ocorrência. O Cerrado é composto por um mosaico de vegetações submetidas às diferenças de clima, relevo e solo, fatores esses que podem favorecer a expressão da plasticidade fenotípica em algumas espécies. Nesse sentido, objetivou-se nessa dissertação conhecer em um primeiro momento a biologia reprodutiva de S. amara, envolvendo aspectos da biologia floral, fenologia, sistema sexual e reprodutivo, bem como os polinizadores. Além disso, procurou-se investigar se as populações da espécie apresentam variações adaptativas e ecológicas no seu sistema morfológico e reprodutivo em ambientes distintos do Cerrado como a mata e o cerrado sensu stricto. Para tanto, a dissertação foi estruturada em dois capítulos: no primeiro, foi abordada a biologia reprodutiva de Simarouba amara Aubl. (Simaroubaceae) em Floresta Semidecídua do Brasil Central. No segundo capítulo: variações na biologia reprodutiva de Simarouba amara Aubl. (Simaroubaceae) em ambiente de Floresta Semidecídua e cerrado sensu stricto.

Abstract Most plants grow in association with arbuscular mycorrhizal (AM) fungi in their roots forming the so-called AM symbiosis. AM symbiosis is usually beneficial to the host as it improves plant survival and performance. However, AM symbiosis also entails a cost to the plant in terms of the carbon allocated to the fungus. In sexually dimorphic plants, more than one type of individual can be recognised with regard to their sexual expression or gender. The cost of reproduction in these plants will differ in relation to the relative investment in male versus female function, as the female and the male sexual functions incur different costs. This different cost of reproduction may be translated into differences in other plant functions between the sexes as all functions are connected through trade-offs. Therefore, since sexes differ in resource needs and allocation patterns, and AM mediate resource acquisition and allocation patterns through imposing both costs and benefits to the plant, the sexes of dimorphic plant species may possess, at least theoretically, a different relationship with their AM roots symbionts. In this thesis, I have investigated whether the sexes in sexually dimorphic plant species differ in their mycorrhizal relationship, and if so, in which ways. Several plant life history traits were studied in the dioecious species Antennaria dioica and also in the gynodioecious Geranium sylvaticum using greenhouse, common-garden and field experiments. Resource acquisition, resource allocation, and both plant and fungal benefits from AM symbiosis were considered. Mainly beneficial effects of AM symbiosis were observed in both sexes of the two dimorphic plant species for most of the studied plant life history traits. Overall, both partners benefited from the AM association. However, several sex-specific benefits were detected which were not uniformly present in all experiments for any given trait. Moreover, the responses observed in certain life history traits were dependent on both the AM fungal and plant species involved in the symbiosis. Remarkably, plants gained sex-specific benefits from the same species of AM fungi and the fungal benefit differed depending on the sex of the host plant. In addition, mycorrhizal benefits were lost under certain environmental conditions. To summarise, the results obtained in this study highlight the complexity of AM interactions. My results suggest that the plant-mycorrhizal fungus relationship may differ depending on the sex of the host plant. Through sex-specific effects on survival, growth and reproduction of the hosts, AM fungi may play a role in the evolution of the life histories in the studied species. In addition, sex-specific relationships between plants and their mycorrhizal symbionts may have potential important consequences for the population dynamics of the sexual morphs and the coevolution of the mycorrhizal relationship.

No description available.

Thesis (Ph. D.)--Miami University, Dept. of Botany, 2006. / Title from second page of PDF document. Includes bibliographical references.

Orientadores: Angela Borges Martins, Peter Warren Fritsch, Frank Almeda / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Biologia / Made available in DSpace on 2018-08-18T20:09:23Z (GMT). No. of bitstreams: 1 AranhaFilho_JoaoLuizMazza_D.pdf: 23081315 bytes, checksum: a40a92f4f2f08a68c7f851a3edd989ff (MD5) Previous issue date: 2011 / Resumo: O presente estudo consiste de uma revisão taxonômica das espécies sul-americanas de Symplocos seção Hopea, um grupo reconhecido principalmente por apresentar flores unissexuadas (espécies dioicas) e estames e estaminódios arranjados em grupos mais ou menos alternos aos lobos da corola. No total foram reconhecidas 27 espécies da seção para o continente, sendo que destas espécies quatro já foram publicadas como novas para a ciência e outras seis foram propostas como novas. O nome Symplocos pentandra, amplamente utilizado em trabalhos florísticos, foi validado; uma espécie anteriormente considerada sinônimo de S. itatiaiae foi restabelecida (S. dasyphylla); quatro nomes com prioridade (S. arbutifolia, S. revoluta, S. estrellensis e S. oblongifolia) foram restabelecidos; novas sinonimizações foram realizadas; vários nomes foram lectotipificados; S. rizzinii, anteriormente excluída de Symplocaceae, foi considerada como pertencente à família; e o nome Symplocos sect. Hopea foi restabelecido (não Symplocos sect. Barberina). Além disso, descrições, fotos, ilustrações, comentários, chave de identificação, lista de materiais examinados, dados de distribuição, fenológicos e ecológicos foram fornecidos / Abstract: This study concerns a taxonomic revision of the South American species of Symplocos section Hopea, which can be recognized mainly by its unisexual flowers and stamens and staminodes somewhat arranged in clusters alternate with the corolla lobes. A total of 27 species of the section were recognized for the continent, four of them were already published as new to sciences and other six were proposed as new. The name Symplocos pentandra, largely used in floristic surveys, was validated; one species previously considered synonym of S. itatiaiae was re-established; four names with priority (S. arbutifolia, S. revoluta, S. estrellensis and S. oblongifolia) were re-established; new synonyms were proposed; several names were lectotypified; S. rizzinii, excluded from Symplocaceae in previous treatment, was considered as a Symplocaceae member; and the name Symplocos sect. Hopea was re-established (not Symplocos sect. Barberina). In addition, descriptions, photos, illustrations, comments, identification key, specimens studied, distribution, phenological, and ecological data were provided / Doutorado / Biologia Vegetal / Doutor em Biologia Vegetal

No description available.

The allocation of resources to male or female progeny, or to male or female reproductive function more generally, is one of the most important life history decisions a sexually reproducing individual must ever make. Sex determination is thus a fundamental process, yet the mechanisms which control it are surprisingly diverse. In this thesis, I examine sex determination in the plant species Mercurialis annua L. (Euphorbiaceae). I assess the mechanism of sex determination operating in dioecious and androdioecious populations of M. annua and also investigate the conservation and evolution of sex-determining mechanisms across the annual mercury clade, the lineages of which display exceptional variation in sexual system. First, using crosses, I establish that sex in dioecious M. annua is controlled by a single-locus genetic mechanism, consistent with recent work that identified a single male-linked DNA marker in the species. My search for new sex-linked genes revealed none, however, suggesting that M. annua possesses at most a small non-recombining region around sex-determining loci. Why many dioecious plants lack heteromorphic sex chromosomes is still poorly understood and I consider explanations for this. I extend my investigation by comparing genetic diversity between loci that differ in their linkage to the sex-determining locus. I find a single male-linked marker to possess significantly lower diversity than autosomal loci, but no difference in the diversity of partially sex-linked and non-sex-linked genes. I also assess the conservation of a sex-linked marker among annual mercury lineages and conduct crosses between lineages to examine the conservation of sex determination. My findings indicate a conserved mechanism of single-locus genetic sex determination and I consider the role polyploidisation and hybridisation have played in sexual system evolution and the modification of sex-determining mechanisms in the clade. Finally, I assess the presence of environmental sex determination in androdioecious M. annua, concluding that although male frequency is not influenced by growing density, a degree of sexual lability exists in the lineage.

La compréhension des mécanismes moléculaires impliqués dans la détermination du sexe chez les plantes à fleurs est primordiale d’un point de vue fondamental et appliqué. Des processus liés à la biosynthèse des hormones, tel que l’éthylène, ou la régulation de l’expression génique via des petits ARN et des facteurs de transcription ont été associés à l’unisexualisation des fleurs chez des espèces dioïques. Cependant, les déterminants contrôlant le sexe chez les plantes sont encore largement méconnus. Le palmier dattier, Phoenix dactylifera L, est une espèce dioïque dont le dimorphisme sexuel est observé très tôt au cours du développement des fleurs. Des gènes différentiellement exprimés (DEGs) ont été identifiés pendant les stades précoces du développement floral mâle et femelle. Pour cela, un transcriptome de référence rassemblant des données d’expression relatives aux deux sexes a été généré. L’analyse d'enrichissement GO des DEGs, a révélé des processus biologiques communs aux mâles et aux femelles, associés au développement reproducteur et à la réponse aux stimuli. Ce résultat indique que des mêmes processus peuvent solliciter des gènes différents au cours du développement floral précoce en fonction du sexe. Cette analyse a également mis en évidence que le développement des fleurs mâles requiert des processus biologiques spécifiques impliqués dans la régulation cellulaire et l'expression des gènes. En outre, deux DEGs femelles, une S-adenosylmethionine synthase et une Flap endonuclease et un DEG mâle, un élément transposable, ont été identifiés dans les régions non-recombinantes du génome du palmier dattier.Cette étude est la première analyse globale des processus biologiques associés à l’acquisition du dimorphisme sexuel. Elle contribue également à la compréhension de la détermination du sexe chez le palmier dattier, et plus largement à la connaissance de ces processus chez les espèces dioïques. / Unraveling molecular mechanisms involved in sex determination in flowering plants is of outstanding basic and applied interest. Several studies on dioecious species have highlighted the molecular basis of sex determination, such as cell death and ethylene biosynthesis pathway. Sex determination mechanisms in plants are, however, still largely unknown. The date palm, Phoenix dactylifera L, is a dioecious species where sexual dimorphism is observed very early in development of flowers. Differentially expressed genes (DEGs) were identified during the early stages of the male and female flower development. A reference transcriptome including male and female data was constructed to gain insight into this process in the dioecious palm Phoenix dactylifera L. Differentially expressed genes (DEG) were subsequently identified between males and females in the early flower development stages in which the first morphological gender difference occurs in date palms.Gene ontology enrichment analysis of DEG revealed biological processes shared between males and females involved in reproductive development and response to stimulus, indicating that same processes could require different genes during early flower development in date palm. This analysis also suggested that date palm triggers biological processes specifically involved in cellular regulation and gene expression to develop male flowers. Furthermore, two female DEGs related to DNA methylation S-adenosylmethionine synthase and DNA metabolism Flap endonuclease, and one male DEGs, a transposable element were found in non-recombinant date palm regions. This study provided the first insight into biological processes involved in sex determination in date palms and more widely to knowledge of this process in dioecious species.