Made available in DSpace on 2014-06-11T19:22:16Z (GMT). No. of bitstreams: 0 Previous issue date: 2005-06-20Bitstream added on 2014-06-13T18:48:47Z : No. of bitstreams: 1 leite_ghp_me_botfca.pdf: 653749 bytes, checksum: d0d894254b462b26f17369f46012f018 (MD5) / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / O projeto de pesquisa teve por objetivo avaliar as alterações fisiológicas na cana-de-açúcar decorrente da aplicação de maturadores químicos com diferentes mecanismos de ação e os reflexos na produtividade e qualidade tecnológica. Dessa forma foram instalados e conduzidos dois experimentos em cana soca nas Fazendas São Joaquim e Bosque, situadas no município de Igaraçú do Tietê, Estado de São Paulo, pertencentes ao Grupo COSAN - Unidade Barra (Usina da Barra). O delineamento experimental utilizado foi o em blocos casualizados com cinco repetições. No experimento 1 (Fazenda São Joaquim) utilizou-se a variedade de cana-de-açúcar RB855453 e no Experimento 2 (Fazenda Bosque) a variedade SP80-3280. Os tratamentos consistiram na aplicação de sete maturadores químicos (KNO3 (p.c. Krista Kana), Etil-trinexapac (p.c. Moddus), Sulfometuron metil (p.c. Curavial), Etefon (p.c. Ethrel), KNO3 + boro (p.c. Krista Kana Plus), Glifosato (p.c. Roundup) e Compostos de radicais carboxílicos orgânicos + Glifosato (p.c. MTD + Roundup)) e uma testemunha, maturação natural. As doses empregadas foram, respectivamente: 3 kg p.c. ha-1, 0,8 L p.c. ha-1, 20 g p.c. ha-1, 2 L p.c. ha-1, 3,0 kg p.c. ha-1, 0,4 L p.c. ha-1 e 1,0 L p.c. ha-1 + 0,15 L p.c. ha-1. A aplicação dos maturadores ocorreu nos meses de março (Experimento 1) e maio (Experimento 2) de 2004, utilizando-se equipamento costal pressurizado (CO2). As parcelas foram constituídas de 8 linhas de 10m de comprimento com espaçamento de 1,5m. Foram avaliados os seguintes parâmetros bioquímicos, biométricos e tecnológicos: atividade das enzimas invertases ácida solúvel e neutra em caldo de cana; altura de plantas, diâmetro dos colmos, número de colmos, rebrota, florescimento, chochamento, brotação lateral, produtividade de colmos e açúcar; pH, acidez, pol, pureza... / The purpose of research was to evaluate physiological alterations in sugarcane due to the application of chemical compounds with different actions and its reflects in the productivity and technological quality. Two experiments were carried out in ratoon cane in São Joaquim Farm and Bosque Farm, in Igaraçú do Tietê, São Paulo State, Brazil, belonging to Grupo COSAN - Unidade Barra (Usina da Barra). The experimental design used was random blocks with five repetitions. In experiment one (São Joaquim Farm) sigarcane RB855453 was used, and in experiment two (Bosque Farm) sugarcane SP80-3280. The treatments consisted of seven chemical compounds (potassium nitrate (trademark Krista Kana), Ethyl-trinexapac (trademark Moddus), Sulfometuron methil (trademark Curavial), Ethephon (trademark Ethrel), potassium nitrate + boron (trademark Krista Kana Plus), Glyphosate (trademark Roundup) and compounds of organic carboxilic radicals + Glyphosate (trademark MTD + Roundup)), and one control. The doses were, respectively: 3.0 kg ha-1 Potassium nitrate, 0.8 L ha-1 Ethyl-trinexapac, 20 g ha-1 Sulfometuron methil, 2.0 L ha-1 Ethephon, 3.0 kg ha-1 KNO3 + Boro, 0.4 L ha-1 Glyphosate, 1.0 L ha-1 Comp. carboxílicos + 0.15 ha-1 Glyphosate. The applications of chemicals were performed in March (Experiment one) and in May (Experiment two) in 2004, with constant spraying pressure... (Complete abstract, click electronic address below)

Factors affecting flowering time have been extensively studied for decades. Greater understanding of flowering time has wider implications in agriculture and ecology as the trait is crucial to optimising reproductive success. It is best understood in the genetic model Arabidopsis thaliana (Arabidopsis), in which loss and gain of function mutations have identified several pathways that regulate flowering and its response to the environment. This has been complemented by studies of natural variation in flowering. Worldwide accessions of Arabidopsis have been used to identify additional flowering regulators and to examine the evolution of these genes and their potential involvement in adaptation to different environments. One of the most extensively studied pathways is responsible for accelerated flowering in response to an extended period of cold (vernalization). Several studies have attributed a substantial proportion of worldwide variation to the genes FRIGIDA (FRI) and FLOWERING LOCUS C (FLC), both of which are instrumental in conferring sensitivity to vernalization, though other genes have also been found. This study examines flowering time variation locally in populations of Arabidopsis from in and around Edinburgh. It identifies substantial, genetically determined variation in flowering time and in sensitivity to photoperiod and vernalization between local accessions. Variation in FRI and FLC sequences and in their levels of expression were detected in local accessions, but these were able to explain little of the phenotypic variation observed. Hybrids between local accessions showing extreme differences in flowering time or responses to photoperiod and vernalization were therefore used to map genes underlying their differences as quantitative trait loci (QTL). This analysis identified a locus in chromosome 5 that could account for differences in vernalization sensitivity. This region includes the VERNALIZATION INSENSITIVE 3 (VIN3) gene. Sequence differences between VIN3 alleles and their expression in response to vernalization supported the potential involvement of this gene in local flowering time variation.

Environmental signals such as photoperiod and temperature provide plants with seasonal information, allowing them to time flowering to occur in favourable conditions. Most ecotypes of the model plant Arabidopsis thaliana flower earlier in long photoperiods and after prolonged exposure to cold (vernalization). The vernalized state is stable through mitosis, but is not transmitted to progeny, suggesting that the vernalization signal may be transmitted via a modification of DNA such as cytosine methylation. The role of methylation in the vernalization response is investigated in this thesis. ¶ Arabidopsis plants transformed with an antisense construct to the cytosine methyltransferase METI (AMT) showed significant decreases in methylation. AMT plants flowered significantly earlier than unvernalized wildtype plants, and the promotion of flowering correlated with the extent of demethylation. The flowering time of mutants with decreased DNA methylation (ddm1) was promoted only in growth conditions in which wildtype plants showed a vernalization response, suggesting that the early flowering response to demethylation operated specifically through the vernalization pathway. ¶ The AMT construct was crossed into two late flowering mutants that differed in vernalization responsiveness. Demethylation promoted flowering of the vernalization responsive mutant fca, but not of the fe mutant, which has only a slight vernalization response. This supports the hypothesis that demethylation is a step in the vernalization pathway. ¶ The role of gibberellic acid (GA) in the early flowering response to demethylation was investigated by observing the effect of the gai mutation, which disrupts the GA signal transduction pathway, on flowering time in plants with demethylated DNA. The presence of a single gai allele delayed flowering, suggesting that the early flowering response to demethylation requires a functional GA signal transduction pathway, and that demethylation increases GA levels or responses, directly or indirectly. ¶ In most transgenic lines, AMT-mediated demethylation did not fully substitute for vernalization. This indicates that part of the response is not affected by METI-mediated methylation, and may involve a second methyltransferase or a factor other than methylation. A second Arabidopsis methyltransferase, METIIa, was characterized and compared to METI. The two genes are very similar throughout the coding region, and share the location of their eleven introns, indicating that they diverged relatively recently. Both are transcribed in all tissues and at all developmental stages assayed, but the level of expression of METI is significantly higher than that of METIIa. The possible functions of METI, METIIa, and other Arabidopsis cytosine methyltransferase genes recently identified are discussed.

Box-Ironbark forests occur on the inland hills of the Great Dividing Range in Australia, from western Victoria to southern Queensland. These dry, open forests are characteristically dominated by Eucalyptus species such as Red Ironbark E. tricarpa, Mugga Ironbark E. sideroxylon and Grey Box E. microcarpa. Within these forests, several Eucalyptus species are a major source of nectar for the blossom-feeding birds and marsupials that form a distinctive component of the fauna. In Victoria, approximately 83% of the original pre - European forests of the Box-Ironbark region have been cleared, and the remaining fragmented forests have been heavily exploited for gold and timber. This exploitation has lead to a change in the structure of these forests, from one dominated by large 80-100 cm diameter, widely -spaced trees to mostly small (≥40 cm DBH), more densely - spaced trees. This thesis examines the flowering ecology of seven Eucalyptus species within a Box-Ironbark community. These species are characteristic of Victorian Box-Ironbark forests; River Red Gum E. camaldulensis, Yellow Gum E. leucoxylon, Red Stringybark E. macrorhyncha, Yellow Box E. melliodora, Grey Box E. microcarpa, Red Box E. polyanthemos and Red Ironbark E. tricarpa. Specifically, the topics examined in this thesis are: (1) the floral character traits of species, and the extent to which these traits can be associated with syndromes of bird or insect pollination; (2) the timing, frequency, duration, intensity, and synchrony of flowering of populations and individual trees; (3) the factors that may explain variation in flowering patterns of individual trees through examination of the relationships between flowering and tree-specific factors of individually marked trees; (4) the influence of tree size on the flowering patterns of individually marked trees, and (5) the spatial and temporal distribution of the floral resources of a dominant species, E. tricarpa. The results are discussed in relation to the evolutionary processes that may have lead to the flowering patterns, and the likely effects of these flowering patterns on blossom-feeding fauna of the Box-Ironbark region. Flowering observations were made for approximately 100 individually marked trees for each species (a total of 754 trees). The flower cover of each tree was assessed at a mean interval of 22 (+ 0.6) days for three years; 1997, 1998 and 1999. The seven species of eucalypt each had characteristic flowering seasons, the timing of which was similar each year. In particular, the timing of peak flowering intensity was consistent between years. Other spatial and temporal aspects of flowering patterns for each species, including the percentage of trees that flowered, frequency of flowering, intensity of flowering and duration of flowering, displayed significant variation between years, between forest stands (sites) and between individual trees within sites. All seven species displayed similar trends in flowering phenology over the study, such that 1997 was a relatively 'poor' flowering year, 1998 a 'good' year and 1999 an 'average' year in this study area. The floral character traits and flowering seasons of the seven Eucalyptus species suggest that each species has traits that can be broadly associated with particular pollinator types. Differences between species in floral traits were most apparent between 'summer' and 'winter' flowering species. Winter - flowering species displayed pollination syndromes associated with bird pollination and summer -flowering species displayed syndromes more associated with insect pollination. Winter - flowering E. tricarpa and E. leucoxylon flowers, for example, were significantly larger, and contained significantly greater volumes of nectar, than those of the summer flowering species, such as E. camaldulensis and E. melliodom. An examination of environmental and tree-specific factors was undertaken to investigate relationships between flowering patterns of individually marked trees of E. microcarpa and E. tricarpa and a range of measures that may influence the observed patterns. A positive association with tree-size was the most consistent explanatory variable for variation between trees in the frequency and intensity of flowering. Competition from near-neighbours, tree health and the number of shrubs within the canopy area were also explanatory variables. The relationship between tree size and flowering phenology was further examined by using the marked trees of all seven species, selected to represent five size-classes. Larger trees (≥40 cm DBH) flowered more frequently, more intensely, and for a greater duration than smaller trees. Larger trees provide more abundant floral resources than smaller trees because they have more flowers per unit area of canopy, they have larger canopies in which more flowers can be supported, and they provide a greater abundance of floral resources over the duration of the flowering season. Heterogeneity in the distribution of floral resources was further highlighted by the study of flowering patterns of E. tricarpa at several spatial and temporal scales. A total of approximately 5,500 trees of different size classes were sampled for flower cover along transects in major forest blocks at each of five sample dates. The abundance of flowers varied between forest blocks, between transects and among tree size - classes. Nectar volumes in flowers of E. tricarpa were sampled. The volume of nectar varied significantly among flowers, between trees, and between forest stands. Mean nectar volume per flower was similar on each sample date. The study of large numbers of individual trees for each of seven species was useful in obtaining quantitative data on flowering patterns of species' populations and individual trees. The timing of flowering for a species is likely to be a result of evolutionary selective forces tempered by environmental conditions. The seven species' populations showed a similar pattern in the frequency and intensity of flowering between years (e.g. 1998 was a 'good' year for most species) suggesting that there is some underlying environmental influence acting on these aspects of flowering. For individual trees, the timing of flowering may be influenced by tree-specific factors that affect the ability of each tree to access soil moisture and nutrients. In turn, local weather patterns, edaphic and biotic associations are likely to influence the available soil moisture. The relationships between the timing of flowering and environmental conditions are likely to be complex. There was no evidence that competition for pollinators has a strong selective influence on the timing of flowering. However, as there is year-round flowering in this community, particular types of pollinators may be differentiated along a temporal gradient (e.g. insects in summer, birds in winter). This type of differentiation may have resulted in the co-evolution of floral traits and pollinator types, with flowers displaying adaptations that match the morphologies and energy requirements of the most abundant pollinators in any particular season. Spatial variation in flowering patterns was evident at several levels. This is likely to occur because of variation in climate, weather patterns, soil types, degrees of disturbance and biotic associations, which vary across the Box-Ironbark region. There was no consistency among sites between years in flowering patterns suggesting that factors affecting flowering at this level are complex. Blossom-feeding animals are confronted with a highly spatially and temporally patchy resource. This patchiness has been increased with human exploitation of these forests leading to a much greater abundance of small trees and fewer large trees. Blossom-feeding birds are likely to respond to this variation in different ways, depending upon diet-breadth, mobility and morphological and behavioural characteristics. Future conservation of the blossom-feeding fauna of Box-Ironbark forests would benefit from the retention of a greater number of large trees, the protection and enhancement of existing remnants, and revegetation with key species, such as E. leucoxylon, E. microcarpa and E. tricarpa. The selective clearing of summer flowering species, which occur on the more fertile areas, may have negatively affected the year-round abundance and distribution of floral resources. The unpredictability of the spatial distribution of flowering patches within the region means that all remnants are likely to be important foraging areas in some years.

Flowering time and flower quality of three nobile dendrobium hybrids in relation to vernalization duration and light intensity during vernalization were studied in the first experiment. Mature Dendrobium Red Emperor 'Prince', Dendrobium Sea Mary 'Snow King', and Dendrobium Love Memory 'Fizz' were cooled at 10 degrees C with 300 to 350 mol·m–2·s–1 photosynthetic photon flux (PPF) (12-h photoperiod) or darkness, each with four cooling durations (2, 4, 6, or 8 weeks). Plants were forced in a greenhouse after vernalization. At least 4 weeks of 10 degrees C cooling in light was needed for flower initiation of Red Emperor 'Prince'; whereas Sea Mary 'Snow King' and Love Memory 'Fizz' only needed 2 weeks of 10 degrees C cooling regardless of light. Darkness during vernalization slightly delayed flowering and resulted in fewer but larger flowers. Longer cooling duration delayed flowering, decreased the flower longevity, and produced larger and more flowers. In the second experiment, Love Memory 'Fizz' were cooled at 15 degrees C for 4 weeks with PPF of 0, 50, 100, or 200 mol·m–2·s–1 (12-h photoperiod). Compared to 200 mol·m–2·s–1, low PPF of 50 or 100 mol·m–2·s–1 did not affect flowering time or flower quality; however, darkness delayed flowering and reduced flower quality. The third experiment was aimed at developing a strategy to defer flowering of nobile dendrobium orchids by holding them under low temperature. Mature Den. Red Emperor 'Prince' and Den. Sea Mary 'Snow King' were held at 10 degrees C for various durations (0, 4, 8, 12 or 16 weeks) after vernalization (4 weeks at 10 degrees C). Plants were forced in a greenhouse after holding. Time to flowering, flower differentiation and flower quality were determined. Increase of low temperature holding duration from 0 to 16 weeks extended time to flowering up to 3 months and did not affect parameters of flower except producing larger flowers and reducing flower number per flowering node for Den. Red Emperor 'Prince'. Notably, the flower longevity was not adversely affected. Defoliation was aggravated in Den. Red Emperor 'Prince' by longer duration of cooling and was considered a detrimental effect of low temperature holding.

In Tripsacum dactyloides, an ancestor of modem maize, genes that control floral development have not been described. A research program to identify and analyze the genes that control and regulate floral development in Tripsacum, has been undertaken through the bioinformatics analysis of Tripsacum cDNA libraries and suppression subtractive EST libraries of stage- and developmentally- specific Tripsacum floral tissue. Comparative analysis of nucleotide sequence data has revealed numerous genes previously described within other floral genomes such as Oryza sativa (rice), Zea mays (maize), Arabidopsis thaliana (thale cress), Triticum spp. (wheat) and Rosa rosesum (rose) well as unique gene sequences. Attempts have been made to characterize the unique genes through analysis of conserved domain sequence segments. / Department of Biology

Harnessing the control of flowering time in sorghum bicolor has been essential to programs committed to the development and improvement of this crop. The success of such programs was dependent on the utilization of six Maturity Loci, photoperiod- responsive floral repressors discovered through classic heritability studies. However, the identities of the genes underlying these loci have remained largely unknown. The elucidation of these genes allows for accelerated marker-assisted breeding programs and contributes to the understanding of flowering time in short day plants. Thus, in these studies, two Maturity Loci were identified using a map-based cloning approach, and alleles of each were sequenced in the germplasm. Expression analysis of individual genes by qRT-PCR and the transcriptome by RNAseq was utilized to characterize their response to photoperiod. Maturity Locus 1 (Ma1), the most effective of the loci, was identified as PSEUDORESPONSE REGULATOR 37, a component of the circadian clock. Sequence analysis revealed an allelic series at this locus, each conferring photoperiod insensitivity to varying degrees. It was demonstrated that the expression of this gene is regulated by the circadian clock, yet also highly dependent on light. Moreover, PRR37 was found to up-regulate floral repressors while down-regulating activators, providing a mechanism of flowering control consistent with the external coincidence model. Maturity Locus 6 (Ma6) also generated interest through its genetic interaction with Ma1, and was identified as Grain Yield, Plant Height and Heading Date 7 (Ghd7). Sequence analysis of Ghd7 revealed several severe mutations and these were traced through several Milo maturity standards, sweet and bioenergy varieties, as well as the pedigree of lines used heavily in the conversion of tropical sorghum to early flowering types. The expression of Ghd7 mirrors that observed for PRR37 and is also regulated by both light and the circadian clock. PRR37 and Ghd7 together confer greater repression of floral activators than either alone, but do so independently via pathways that converge on the same downstream "florigen". Thus in sorghum varieties with functional alleles of both, floral initiation is delayed indefinitely in long day photoperiods. The identification of these two genes provides a novel perspective on flowering in short day plants, while also accelerating breeding efforts that ultimately result in improved sorghum varieties for food, forage, and biofuels.

Typescript. Bibliography: leaves 75-80

ABSTRACT The ability to detect and respond to environmental signals is fundamental in coordinating floral induction in plants to favourable conditions. An important flowering time cue is day length and it is proposed that light signals are perceived and measured by an interaction between photoreceptors and an internal pacemaker, the circadian clock. The control of flowering has been best characterised in the model plant Arabidopsis thaliana L. Heynh (Arabidopsis). The GIGANTEA (GI) gene has a complex role in both the promotion of flowering in response to photoperiod and the regulation of the circadian clock. The expression of GI is under circadian control and is affected by day length, light quality and temperature changes. The GI protein is also circadian regulated and is actively degraded in the dark. The biochemical function of GI is unknown and one method to elucidate the role of this protein is to identify protein interactors. The aim of this thesis project was to characterise proteins that interacted with GI. Previously, the BELL-LIKE HOMEODOMAIN 3 (BLH3) protein was identified as a putative GI protein interactor. As part of this thesis work, yeast 2-hybrid and in vitro pull down assays were utilised to confirm the interaction between GI and BLH3. Sequence and phylogenetic analyses were used to further examine the BELL family of proteins. The BELL-LIKE HOMEODOMAIN 10 (BLH10) protein was found to be closely related to BLH3 and also interacted with GI. Reverse 2-hybrid assays were used to determine the regions or domains within the GI, BLH3 and BLH10 proteins required to mediate protein interactions. Expression assays established that the BLH3 and BLH10 transcripts were present throughout plant tissues and times of development. Further analyses revealed that BLH3 and BLH10 are not directly regulated by the circadian clock. The results of GFP expression assays demonstrated that the BLH3 protein is localised to the nucleus in plant cells. Transgenic blh3 and blh10 mutant plants were identified and analysed for flowering and light response phenotypes. BLH3 and BLH10 do not function with GI in the photoperiodic pathway to control flowering, yet the blh3 and blh10 mutants do have a flowering phenotype in short day conditions. Like gi, the blh3 and blh10 mutants exhibited exaggerated hypocotyl elongation in response to red and low light conditions. These results are suggestive of a role for BLH3, BLH10 and GI in flowering and deetiolation responses to specific light conditions in plants. / This PhD research was sponsored by Dr George Mason

ABSTRACT The ability to detect and respond to environmental signals is fundamental in coordinating floral induction in plants to favourable conditions. An important flowering time cue is day length and it is proposed that light signals are perceived and measured by an interaction between photoreceptors and an internal pacemaker, the circadian clock. The control of flowering has been best characterised in the model plant Arabidopsis thaliana L. Heynh (Arabidopsis). The GIGANTEA (GI) gene has a complex role in both the promotion of flowering in response to photoperiod and the regulation of the circadian clock. The expression of GI is under circadian control and is affected by day length, light quality and temperature changes. The GI protein is also circadian regulated and is actively degraded in the dark. The biochemical function of GI is unknown and one method to elucidate the role of this protein is to identify protein interactors. The aim of this thesis project was to characterise proteins that interacted with GI. Previously, the BELL-LIKE HOMEODOMAIN 3 (BLH3) protein was identified as a putative GI protein interactor. As part of this thesis work, yeast 2-hybrid and in vitro pull down assays were utilised to confirm the interaction between GI and BLH3. Sequence and phylogenetic analyses were used to further examine the BELL family of proteins. The BELL-LIKE HOMEODOMAIN 10 (BLH10) protein was found to be closely related to BLH3 and also interacted with GI. Reverse 2-hybrid assays were used to determine the regions or domains within the GI, BLH3 and BLH10 proteins required to mediate protein interactions. Expression assays established that the BLH3 and BLH10 transcripts were present throughout plant tissues and times of development. Further analyses revealed that BLH3 and BLH10 are not directly regulated by the circadian clock. The results of GFP expression assays demonstrated that the BLH3 protein is localised to the nucleus in plant cells. Transgenic blh3 and blh10 mutant plants were identified and analysed for flowering and light response phenotypes. BLH3 and BLH10 do not function with GI in the photoperiodic pathway to control flowering, yet the blh3 and blh10 mutants do have a flowering phenotype in short day conditions. Like gi, the blh3 and blh10 mutants exhibited exaggerated hypocotyl elongation in response to red and low light conditions. These results are suggestive of a role for BLH3, BLH10 and GI in flowering and deetiolation responses to specific light conditions in plants. / This PhD research was sponsored by Dr George Mason