Thesis (M.S.)--Worcester Polytechnic Institute. / Keywords: phytochrome; shade avoidance; microarray; HFR1. Includes bibliographical references (p. 52-56).

This investigation was initiated to study the effect of CO₂ on phytochrome-mediated morphogenesis in flowering and seed germination. Removal of CO₂ by flushing the plant environment with CO₂-free air inhibited the red light interruption effects on flowering in Xanthium pennsylvanicum and on seed germination in Lactuca sativa cv Grand Rapids. Further experiments were done to investigate the involvement of CO₂ exchange in the effects of night interruptions on flowering in Xanthium. ¹⁴CO₂ feeding trials showed that red light given for 5 minutes caused a net increase in ¹⁴C activity in the ethanol soluble fraction when ¹⁴CO₂ was fed during the light treatment. There was no effect of red light on the extent of ¹⁴CO₂ fixation in the dark period immediately following red light. The types of free amino acids recovered after paper chromatography were essentially the same after ¹⁴CO₂ feedings in darkness, red light, and far red light following red light. However, there was a considerable increase in ¹⁴C activity in most of the amino acids in leaves given red light interruption, and the amount further increased when far red light was given following the red light. The extent of ¹⁴C label in tyrosine, valine and leucine was essentially the same in all the three treatments. In CO₂-exchange experiments using the IRGA, brief red or far red light treatments were applied to Xanthium plants under inductive dark periods and the subsequent flowering response was assessed according to bud morphology. The occurrence of flowering depended on the timing, wavelength and intensity of the light treatments, and on the CCL concentration during the light treatments. CO₂ exchange was measured during the night interruptions in single attached leaves. CO₂ exchange was influenced by the conditions during the night interruptions, but there was no apparent correlation between the pattern of CO₂ exchange observed and the subsequent flowering response. It appears that the action of during night interruptions is not associated with the exchange of during the night interruption. In an attempt to investigate other possible roles of CO₂, experiments were done with light sensitive lettuce and Amaranthus retroflexus L. seeds. These experiments pertained to changes in pH of the incubation medium and CO₂ concentration simultaneously. Germination was strongly promoted at pH 4.0 but the promotion diminished with increases in pH and did not occur at pH 7.5. The response of germination to red irradiation was suppressed by CO₂ removal and enhanced by CO₂ enrichment in air or atmospheres. There was a close similarity between the pH effects on percentage germination and pH dependence of the CO₂ /HCO₃ - equilibrium. Transfer experiments, in which lettuce seeds were exchanged between buffers of pH 4.0 and pH 3.0, showed that the red/far red photo-transformation of phytochrome v/as independent of pH. Low pH, however, was required for onset of germination following red irradiation. Thereafter, pH between 4.0 and 8.0 did not limit the progress of germination. It is postulated that following red irradiation, a product develops which is distinguishable from the Pfr form of phytochrome. The product is stable at pH 8.0 and at pH 4.0 it acts to promote germination. / Science, Faculty of / Botany, Department of / Graduate

Title from first page of PDF document. Includes bibliographical references (p. 26-29).

Pak-chung Leung. / Thesis (Ph.D.)--Chinese University of Hong Kong, 1994. / Includes bibliographical references (leaves 151-158). / Abstract --- p.i / Acknowledgments --- p.iii / Table of contents --- p.iv / List of Figures --- p.viii / List of Tables --- p.ix / List of Abbreviations --- p.xiv / Chapter / Chapter 1. --- General Introduction --- p.1 / Chapter 2. --- Literature Review: Greening process in higher plants --- p.4 / Chapter 3. --- Greening Bioassay in Excised Cucumber Cotyledons / Introduction --- p.13 / Materials and Methods / Plant material --- p.14 / Measurement of Ch1 synthesizing activity in excised cotyledons of different ages --- p.14 / Measurement of Ch1 accumulation in excised cotyledons after various pretreatment periods --- p.15 / Measurement of Ch1 accumulation in excised cotyledons under different light intensities and temperatures --- p.15 / Greening curve --- p.16 / Results and Discussion / Effect of seedling age on Ch1 accumulation --- p.16 / Effect of pretreatment period on Ch1 accumulation --- p.18 / Effects of light intensity and temperature on Ch1 accumulation --- p.18 / Effect of shaking (for oxygen replenishment) on Ch1 accumulation --- p.19 / Greening curve --- p.20 / Greening bioassay in excised cucumber cotyledons --- p.20 / Chapter 4. --- Regulation of Chlorophyll Accumulation in Excised Cucumber Cotyledons / Introduction --- p.27 / Materials and Methods / Materials --- p.28 / Seed germination --- p.28 / Harvesting and pretreatment --- p.28 / Illumination and Ch1 determination --- p.29 / Results / Effect of BA on Ch1 accumulation --- p.29 / Effect of Na2EGTA on Ch1 accumulation --- p.30 / "Effect of Na+, Ca2+ and K+ on Ch1 accumulation" --- p.32 / Effect of duration of pretreatment with Na+ ， Ca2+ and K+ on Ch1 accumulation --- p.34 / Effect of verapamil and Ca ionophore A23187 on Chl accumulation --- p.36 / Effect of TFP on Chl accumulation --- p.37 / Discussion / Effect of BA on Chl accumulation --- p.38 / "Effect of Na+, Ca2+ and K+ on Chl accumulation" --- p.39 / Demonstration of the involvement of Ca2+ in Chl accumulation --- p.43 / Chapter 5. --- The Calcium Effect on Benzyladenine-induced Stimulation of Chlorophyll Accumulation in Excised Cucumber Cotyledons / Introduction --- p.63 / Materials and Methods / Materials --- p.64 / Plant growth and treatment --- p.64 / Pretreatment experiment --- p.64 / Sequence experiment --- p.65 / Results / Pretreatment experiment --- p.65 / Sequence experiment --- p.66 / Discussion --- p.68 / Chapter 6. --- Regulation of 5-Aminolevulinic Acid and Chlorophyll Accumulation in Levulinic Acid-treated Cotyledons / Introduction --- p.80 / Materials and Methods / Materials --- p.81 / Plant growth and treatment --- p.81 / Chl determination and ALA assay --- p.82 / Measurement of ALA and Chl accumulation in LA-treated cotyledons --- p.83 / ALA accumulation curve --- p.83 / Measurement of Chl accumulation in 50 mM NaCl-treated cotyledons --- p.84 / "Measurement of ALA and Chl accumulation in BA-, cations-, Na2EGTA-, verapamil- and TFP-pretreated cotyledons" --- p.85 / Results / Concentrations effect of LA on ALA and Chl accumulation --- p.85 / ALA accumulation curve --- p.86 / Effect of 50 mM NaCl on Chl accumulation --- p.87 / Effect of BA on ALA and Chl accumulation in LA- treated cotyledons --- p.90 / "Effects of Na+, Ca2+ and K+ on ALA and Chl accumulation in LA-treated cotyledons" --- p.91 / "Effects of Na2EGTA, verapamil and TFP on ALA and Chl accumulation in LA-treated cotyledons" --- p.92 / Discussion / Measurement of ALA accumulation in LA-treated cotyledons --- p.93 / Effect of BA on ALA and Chl accumulation in LA-treated cotyledons --- p.96 / "Effects of Na+, Ca2+ and K+ on ALA and Chl accumulation in LA-treated cotyledons" --- p.98 / Demonstration of the involvement of Ca2+ in ALA accumulation --- p.99 / Chapter 7. --- Regulation of 5-Aminolevulinic Acid Accumulation in Isolated Developing Chloroplasts / Introduction --- p.123 / Materials and Methods / Materials --- p.124 / Plant materials --- p.124 / Chloroplast isolation --- p.125 / Incubation conditions --- p.126 / ALA assay --- p.127 / Measurement of ALA accumulation in LA-treated isolated developing chloroplasts --- p.128 / "Measurement of ALA accumulation in BA-, cations-, Na2EGTA-, verapamil- and TFP-treated isolated developing chloroplasts" --- p.128 / Results / Time course study of Chl accumulation in intact greening cotyledons of different ages --- p.129 / Measurement of ALA synthesizing activity in isolated developing chloroplasts incubated in the dark and light --- p.130 / Concentrations effect of LA on ALA accumulation in isolated developing chloroplasts --- p.130 / Effects of BA and the cations on ALA accumulation in isolated developing chloroplasts --- p.131 / "Effect of Na2EGTA, verapamil and TFP on ALA accumulation in isolated developing chloroplasts" --- p.132 / Discussion / Light regulation of ALA synthesizing activity in isolated developing chloroplasts --- p.132 / Regulation of ALA accumulation in isolated developing chloroplasts --- p.134 / Chapter 8. --- Conclusion --- p.147 / References --- p.151

Made available in DSpace on 2014-06-11T19:31:01Z (GMT). No. of bitstreams: 0 Previous issue date: 2009-02-27Bitstream added on 2014-06-13T18:41:25Z : No. of bitstreams: 1 klein_j_dr_botib.pdf: 464105 bytes, checksum: a5a7f19019acd7bf085f6e55562af753 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / A luz pode ser considerada um dos principais fatores ambientais no controle da germinação e desenvolvimento de diferentes espécies, principalmente em plantas nativas. Tendo em vista a importância da espécie Peltophorum dubium para a utilização no re-povoamento de áreas degradadas, arborização e paisagismo, avaliou-se o comportamento fisiológico de suas sementes analisando a influência da luz eo efeito de um protetor físico com diferentes filtros no processo germinativo, emergência, crescimento inicial e trocas gasosas de suas plântulas. Para tanto, frutos maduros de canafístula foram coletadas em diversas matrizes em setembro de 2007. Após a coleta, os frutos foram levados para o Laboratório de Interações Tróficas do Departamento de Botânica do Instituto de Biociência da Unesp/Botucatu onde foram beneficiadas e escarificadas. Desta forma, instalou-se os seguintes tratamentos: T 1- gerbox transparente; T2- gerbox transparente + celofane transparente; T3- gerbox preto; T4- gerbox preto + celofane transparente; T5- gerbox transparente + celofane azul e T6- gerbox transparente + celofane vermelho. Foram avaliadas as seguintes características: porcentagem de germinação, IVG, comprimentos de radícula, de epicótilo, de cotilédone e da plântula, massa seca, clorofilas a, b, totais e relação a/b. Em um segundo experimento realizado na área aberta do Departamento de Botânica (22° 52' de latitude, 48 ° 26' de longitude), no Instituto de Biociências, Unesp, Botucatu - SP, utilizando-se um protetor físico constituido por garrafas do tipo P.E.T. (Polietileno Teraftalato) com volume de 2500 mL sem fundo e sem tampa. Diferentes comprimentos de ondas luminosas foram obtidos acoplando as garrafas do tipo P.ET. com duas camadas de papel celofane com diferentes tonalidades (transparente, azul e vermelho). Desta forma, obtiveram-se os seguintes tratamentos: T1, ausência... / Light is considered one of the major environmental factors controlling the germination and development of different species, mainly native ones. Based on the importance of the species Peltophorum dubium for revegetation of degraded areas, tree planting and landscaping, this study evaluated germination, emergence, initial growth and gas exchanges of canafistula seedlings under light influence by using physical protectors presenting different filters. Thus, the following treatments were adopted: T1, transparent germination box; T2, transparent germination box + transparent cellophane; T3, black germination box; T4, black germination box + transparent cellophane; T5, transparent germination box + blue cellophane; T6, transparent germination box + red cellophane. The evaluated characteristics were: germination percentage, germination velocity index (GVI), radicle, epicotyl, cotyledon and seedling ngth, dry matter, total chlorophylls and their fractions a and b, and the ratio a/b. A second experiment was carried out in an open area from the Department of Botany (22° 52' S, 48 ° 26' W), Institute of Biosciences, Sao Paulo State University (UNESP), Botucatu, Sao Paulo State, Brazil, in which physical protectors corresponding to polyethylene terephthalate (PET)-type bottles (2500 mL) without lid and bottom were used. Different wavelengths were obtained when two layers of cellophane paper of different colors (transparent, blue and red) were added to the PET-type bottles. Thus, the following treatments ere established: T1, absence of physical protector (APP); T2, transparent physical protector (TPP); T3, transparent physical protector + blue cellophane (BPP); and T4, transparent physical protector + red cellophane (RPP). The experimental design was completely randomized, with 4 treatments x 6 evaluation times and 5 replicates. Emergence velocity index (EVI), seedling emergence, survival... (Complete abstract click electronic access below)

Light is one of the environmental signals that regulate axillary shoot development. However, little is known about molecular and physiological mechanisms regulating the development of the axillary shoot in response to light signals. Molecular events associated with the enhanced apical dominance of phytochrome B mutant sorghum (Sorghum bicolor) were analyzed to reveal processes mediating axillary shoot development in response to light. The enhanced apical dominance of phyB-1 mutant sorghum is due to inhibition of bud outgrowth and is accompanied by upregulation of the dormancy-associated gene (SbDRM1) in the buds. Increased expression of the Teosinte Branched1 (SbTB1) gene (encoding a putative transcription factor that represses bud outgrowth) suggests that the inhibition of bud outgrowth in phyB-1 sorghum is due to the absence of active phyB to repress SbTB1. The results were confirmed by growing wild type seedlings at high plant density or with supplemental farred (FR) light that induces enhanced apical dominance. However, the SbTB1 gene is not involved in the inhibition of bud outgrowth induced by defoliation in wild type seedlings. The results indicate variations in molecular mechanisms among different signals inhibiting branching. Increased expression of SbMAX2 (which encodes an F-box protein that represses bud outgrowth) in buds repressed by light and defoliation suggests common mechanisms at the downstream end of pathways inhibiting branching. The expression levels of several cell cycle-related genes including SbPCNA, SbHis4, SbCycD2, SbCycB and SbCDKB were down-regulated in the repressed buds of FRtreated and defoliated seedlings indicating the suspension of cell division in those buds. However, these cell cycle-related genes were continuously expressed in the repressed buds of phyB-1, suggesting that inhibition of bud outgrowth in phyB-1 is not associated with down-regulation of cell cycle-related gene expression. The down-regulation of cell cycle-related genes in the buds of FR-treated wild type seedlings indicates that other sensors, in addition to phyB, regulate bud outgrowth in response to FR enrichment. The approaches used and results achieved will provide direction for future research on this important topic.

Leaf senescence is the final stage of leaf development, during which the leaf relocates most of itsvaluable nutrients to developing or storing parts of the plant. As this process progresses, leaves losetheir green color and their capacity to perform photosynthesis. Shade and darkness are well-knownas factors inducing leaf senescence and it has been proposed that senescence can be initiated byreductions in photosynthesis, photomorphogenesis and transpiration. However, despite the fact thatthe signaling mechanisms regulating each of these processes have been extensively described,particularly in seedlings, their contribution to the initiation of senescence in mature leaves stillremains unclear. Furthermore, the use of different experimental systems to study shade-inducedleaf senescence has yielded several divergent results, which altogether complicate the overallunderstanding of leaf senescence. To address this, darkened plants and individually darkened leaves, which show different rates of leafsenescence, were studied. Comparing the transcriptome and metabolome of these two darktreatmentsrevealed that they differed distinctly with regard to their metabolic strategies. Wholedarkened plants were severely carbohydrate-starved, accumulated amino acids and slowed downtheir metabolism. In contrast, individually darkened leaves showed continued active metabolismcoupled to senescence-associated degradation and relocation of amino acids. This knowledge was used to set up a new system to study how shade affects leaf senescence in themodel plant Arabidopsis thaliana. Use of this system revealed that different senescence-associatedhallmarks appeared in response to different intensities of shade. Some of these hallmarks werefurther shown to be part of both leaf senescence and photosynthetic acclimation to low light. Finally, using this system on phytochrome mutants revealed that loss of phytochrome A increasedthe loss of chlorophyll under shade, without increasing the expression of senescence-associatedgenes. Together, these findings suggest that shade-induced leaf senescence, which is generally perceived asa single process, is actually an intricate network of different processes that work together tomaintain an optimal distribution of nutrients within the plant.

The stage of maturity of seeds at harvest is an important factor that determines seed vigor. Separating seeds from a seed lot composed of many different stages of development can be difficult especially after maximum dry mass is attained. Separating seeds based on their physiological maturity is more challenging than sorting seeds based on their physical properties. Seeds may be non-destructively sorted using chlorophyll fluorescence (CF) as a marker of seed maturity. This study was conducted to test whether CF could be used to remove low vigor immature seeds from muskmelon (Cucumis melo L.'Top Mark') and tomato (Lycopersicum esculentum) seed lots. Light treatments were applied to determine whether the light environment during seed harvesting and processing could affect chlorophyll content and seed vigor. Seeds from nine stages of development were collected from 'TopMark'. Seeds from three stages of fruit development (red ripe, breaker, and mature green) were harvested from tomato cultivar Money Maker and two phytochrome mutants: phytochrome A mutant, fri-1 and phytochrome B mutant, tri-1. The SeedMaster Analyzer (Satake USA Inc., Houston Texas) was used to measure CF and to sort individual seeds according to CF levels. Immature tomato seeds and muskmelon, harvested from green fruits, had the highest CF (p>0.001). Contrary to the results obtained with the other tomato genotypes, the vigor of tri-1 did not change inversely with changing CF levels, rather, seeds with low CF had the same vigor as seeds with high CF. This result may suggest that the presence of phytochrome B exerts an inhibitory influence on vigor in tomato seeds, and that the persistent presence of chlorophyll during seed development does not affect vigor. The light treatments had no consistent effect on seed chlorophyll content or on vigor in either tomato or muskmelon. / Master of Science

No description available.

As plants are sessile organisms, processes controlling plant growth and development must react to fluctuations in the external environment to aid plant survival. However, as the climate of the Earth changes and becomes more extreme, plants become less able to develop to their optimal capacity and this can have an adverse effect on crop yield and biofuel feedstock production. Thus, it is becoming increasingly important to understand the molecular mechanisms used by plants to respond to external stimuli. One important system that plants utilise in their response to environmental fluctuations is the circadian clock. The circadian clock is a time-measuring device that buffers the timing of plant growth and development against fluctuations in the local environment, such as temperature, light quality and light intensity. Importantly, the circadian clock is also able to measure day-length (photoperiod). Thus, plant development and growth is co-ordinated with photoperiod that is closely linked to seasonal changes. A key example of this is the time taken for a plant to flower. Flowering of Arabidopsis thaliana occurs specifically in long-days (LDs) of spring/summer months. Thus, the circadian clock is a key regulator promoting flowering in LD conditions. In conjunction with experimental studies, mathematical modelling has proven to be a successful method of elucidating the mechanisms that underlie complex biological systems. One example of this 'systems biology' approach is in uncovering the components that make up the Arabidopsis circadian clock mechanism. Previous research in our group has also led to the development of a model describing photoperiodic flowering that is tentatively linked to the circadian clock mechanism. In this thesis I shall develop on these models to highlight five key results: 1. using rhythmic PHYTOCHROME INTERACTING FACTOR 4 (PIF4) and PIF5 mRNA as an example, I shall show that multiple circadian regulators are required to describe rhythmic transcription of target genes across multiple photoperiods; 2. the stabilisation of CONSTANS (CO) protein by the blue light-signalling component FLAVIN-BINDING, KELCH REPEAT, F-BOX 1 (FKF1) is required to for flowering in LDs and has a relatively larger impact on photoperiodic flowering than FKF1-dependent degradation of CYCLING DOF FACTOR 1 (CDF1), an inhibitor of flowering; 3. multiple components of the circadian clock play specific post-translational roles in photoperiodic flowering to promote the acceleration of flowering specifically in LDs; 4. temperature regulation of photoperiodic flowering can be explained through an interaction between CO and PIF proteins, limiting the effects of temperature to a specific time-window in a 24-hour day; 5. red light- and temperature-control of the circadian clock can be explained by altering the post-translational regulation of circadian clock components.