The ability of exogenous gibberellin (GA) A3 to substitute for low temperatures in inducing flowering in Phalaenopsis hybrida under high temperatures suggests a similar role for endogenous GAs in normal (low temperature) development of the inflorescence and floral buds. Changes in endogenous GAs in shoot-tips (about 2.0 cm long) were examined when potentially flowering shoot was 2-3 cm and 7-10 cm long, respectively. Treatments included warm control (30/25 ¢J day/night, non-flowering), GA3-treated (30/25 ¢J day/night, flowering) and cool-induced (25/20 ¢J day/night, flowering) plants. GA3 at 0.5 £gg•shoot-1 was injected into the cavity of the second visible bud scale below the flowering shoot apex. The contents of the tips of potentially flowering shoot of GA1, GA20, GA19 and GA53 tended to be highest in cool-induced plants, intermediate in GA3-treated plants, and lowest in the warm controls (non-flowering). Tips of potentially flowering shoots in warm controls also contained higher GA8 relative to GA3-treated and cool-induced plants. Tips of potentially flowering shoots (2-3 cm in length with no flower primordium), contained low levels of GAs than older 7-10 cm long flowering shoot (with flower primordium) under cool-inductive conditions. These results suggest that continued inflorescence development and flower bud initiation are closely associated with increases in endogenous GAs, even in GA3-treated plants. They also suggest that a more rapid biosynthetic flow-through from GA19¡÷GA20¡÷GA1¡÷GA8 leaving reduced levels of GA1 may be involved in the inhibition of flowering and shoot elongation seen in warm (30/25 ¢J day/night) control plants. A reduced conversion of ¡§active¡¨ GA1 to inactive GA8 may thus be required for successful floral initiation and development whether induced by cool temperature or by applied GA3. These results imply that the high temperature inhibitory effect on flowering is mediated through its effect on lowering the level of endogenous GA1 and its precursors.

iii, 143 leaves : diags ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--University of Adelaide, Dept. of Organic Chemistry, 1976

Thesis (Ph.D.) -- University of Adelaide, Department of Organic Chemistry, 1976.

The thesis is presented in five parts. In the first, our present knowledge of red alder {Alnus rubra Bong.) is summarized and shows a lack of specific knowledge about its seed and reproductive biology. The aims of the first study were (1) to determine the occurrence and (if present) the nature of seed dormancy; (2) to determine whether seed vigour was related to geographic location of different provenances; and (3) to examine the influence of stratification and presoaking on seed germination. Germination tests were carried out on stratified, presoaked and untreated seeds collected from several locations throughout the species' range. With one exception (seed from Haney, B. C. collected in 1976), dormancy was not a significant factor in preventing germination of untreated seeds. Germination of these exceptional seeds was improved by cold stratification for eight days and to a lesser extent, by presoaking in tap water for 2h hours. Seed collected from the same area before and after these tests showed no dormancy. Germination percent was relatively high for treated and untreated seeds of other provenances and showed few differences between provenances. There were more pronounced differences in seed vigour, as measured by germination value, between provenances. There appeared to be no direct relationship between the differences observed and geographic factors, as found in many wide ranging species native to western North America. The aims of the second study were (1) to examine the effects of fertilization and different soil types on root and nodule development, height growth, dry weight accumulation and root-shoot dry weight ratio of seedlings of red alder from different locations in its natural distribution; and (2) to relate observed differences between provenances to their geographic location. Early seedling development in fertilized and unfertilized seedlings front several sources and grown in different combinations of sand and a loamy soil, was examined. Root development was influenced by the type of growth medium and the nutrient status of the same. Nodulation, however, was little affected by these factors. Nodule development was more extensive on upper root branches than on lower ones. Fertilization increased height and dry weight, and lowered root-shoot dry weight ratio of seedlings. Height growth and dry weight accumulation were greater, and root-shoot ratio was lower in loam and in a loam-sand mixture (1:1 w/w) than in sand. Height growth did not differ between provenances. There were differences in dry weight and root-shoot ratio between provenances but these differences were not correlated with any geographic factor. In the last study, an attempt was made to identify endogenous gibberellins extracted from quiescent vegetative, male and female buds of red alder. Following fractionation of the extracts by silica gel partition chromatography, positive growth responses were obtained in the dwarf rice bioassay of several of the fractions. In gas-liquid chromatography, various fractions produced peaks with retention times similar to those of standard gibberellins. Although some qualitative indications were noted, it was not possible to confirm the presence and identity of gibberellins using combined gas-1iquid chromatography-mass spectrometry. Inadequate purification of extracts and low concentrations of endogenous gibberellins in the extracts were thought to be mainly responsible for this failure. The impact and implications arising from the results of these studies and -possible future directions for research are discussed in the final chapter. / Forestry, Faculty of / Graduate

No description available.

Plant development is an iterative process of organ formation from the primary meristems of the plant. Meristem activity is driven by dynamic transcriptional programs that determine cell fate and identity as cells are displaced trough the meristematic tissue to initiate organ primordia. This regulatory network includes members of the TCP and KNOX family of transcription factors, and integrates external and intrinsic cues to efficiently adapt meristem activity to an ever-changing environment. However, how this integration occurs is not clear yet. DELLA proteins have been proposed to modulate transcriptional circuits in plants in response to environmental signals. Although they do not show DNA binding capacity, DELLAs regulate transcription through physical interaction with a large number of DNA-binding transcription factors and other transcriptional regulators. Given the observed interaction between DELLAs and several members of the TCP family of transcription factors, we have explored the relevance of this interaction in the regulation of primary meristems. We have confirmed that DELLAs interact with members of both Class I and Class II TCPs, and prevent their ability to regulate downstream targets. In the embryonic roots, DELLAs maintain a dormant meristem by impairing TCP14/15-dependent activation of cell-cycle genes. On the other hand, DELLAs participate in the establishment of the shoot apical meristem domain that keeps an indeterminate fate, through the control of KNAT1 gene expression by the TCP2/4-AS1 regulatory module. In summary, this Thesis provides a mechanistic framework to eventually explain environmental regulation of meristem activity. / El desarrollo de las plantas es un proceso iterativo de formación de órganos a partir de los meristemos primarios de la planta. La actividad meristemática está dirigida por programas transcripcionales dinámicos que determinan el destino y la identidad celular conforme las células son desplazadas a través del tejido meristemático para iniciar el primordio del órgano. Esta red regulatoria incluye miembros de las familias de factores de transcripción TCP y KNOX, e integra señales externas e intrínsecas para adaptar eficientemente la actividad meristemática al medio ambiente, siempre cambiante. Sin embargo, la manera en que esta integración ocurre no se ha desvelado todavía. Se ha propuesto que en plantas, las proteínas DELLA modulan los circuitos transcripcionales en respuesta a señales medioambientales. Aunque no muestran capacidad de unión al ADN, las DELLAs regulan la transcripción a través de su interacción física con un gran número de factores de transcripción capaces de unirse al ADN y otros reguladores transcripcionales. Dada la interacción observada entre las DELLA y varios miembros de la familia de factores de transcripción TCP, hemos explorado la relevancia de esta interacción en la regulación de los meristemos primarios. Hemos confirmado que las DELLA interaccionan con miembros de las dos clases de TCPs (Clase I y Clase II) e impiden su capacidad de regular dianas aguas abajo. En la raíz del embrión, las DELLAs mantienen el meristemo durmiente al impedir la activación de los genes de ciclo celular dependiente del módulo TCP14/15. Por otro lado, las DELLAs participan en el establecimiento del meristemo apical del tallo, que mantiene un estado indiferenciado, a través del control el módulo TCP2/4-AS1, el cual regula la expresión del gen KNAT1. En resumen, esta Tesis aporta un marco mecanístico para explicar, con el tiempo, la regulación medioambiental de la actividad meristemática. / El desenvolupament de les plantes consiteix en un procés iteratiu de formació d'órgans a partir dels meristems primaris. L'activitat meristemàtica està diridida per programes transcripcionals dinàmics que determinen el destí i la identitat cel.lular a mesura que les cèl.lules es van allunyant del meristem per formar els primordis d`órgans. Esta xarxa de regulació inclou membres de les famílies de factors de transcripció TCP i KNOX, i integra senyals externes i intrínseques per adaptar d'una manera eficient l'activitat del meristem als canvis del medi ambient. No obstant, no es coneix de quina manera la planta fa esta integració. S'ha proposat que les proteïnes DELLA modulen estes xarxes transcripcionals en resposta a senyals del medi. Estes proteïnes no tenen capacitat d'unir-se a l'ADN, però regulen la transcripció mitjançant la interacció amb factors de transcripció i altres reguladors transcripcionals. Donada la interacció entre les proteïnes DELLA i alguns membres de la família de factors de transcripció TCP, hem explorat la rellevància d'esta interacció a la regulació dels meristems primaris. Hem confirmat que les DELLA interaccionen amb membres de les dos classes de TCPs (Classe I i Classe II) i els impedeixen regular les seues dianes. A l'arrel de l'embrió, les DELLA mantenen el meristem dorment al impedir l'activació de gens del cicle cel.lular depenent del mòdul TCP14/15. Per una altra banda, les DELLA particípen a l'establiment del meristem apical de la tija, al que mantenen en un estat indiferenciat, mitjançant el control del mòdul TCP2/4-AS1, que regula l'expressió de KNAT1. En resum, esta Tesi aporta un marc mecanístic per poder explicar, més endavant, la regulació mediambiental de l'activitat meristemàtica. / Felipo Benavent, A. (2017). Modulation of primary meristem activity by gibberellins through DELLA-TCP interaction in Arabidopsis [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/82237

Šio magistrinio darbo tikslas buvo ištirti giberelinų ir jų sintezės inhibitorių poveikį paprastosios drebulės (Populus tremula L.) eksplantų vystymuisi in vitro. Palyginus su auksinų ir citokininų klasių fitohormonais, kurie plačiai pritaikomi medžių mikrovegetatyviniam dauginimui, giberelinų poveikis sumedėjusiems augalams in vitro kultūroje yra ištirtas gana mažai. Tokie tyrimai svarbūs dėl jų praktinio pritaikymo galimybės, kadangi vis didėja vegetatyviškai padaugintų medžių, ypač plantacinei miškininkystei tinkamų drebulių, poreikis. / The aim of this research work was to investigate the effect of gibberellins and gibberellin biosynthesis inhibitors on common aspen (Populus tremula L.) explants. In comparison to phytohormones of auxin and cytokinin classes that are widely applied for the micropropagation of trees, the effect of gibberellins on woody plants in in vitro culture is not so well known. The investigation of this effect seems to be important because of the possibility of practical application, inasmuch as the need for vegetatively multiplied trees, especially for aspens suitable for plantation forestry, is constantly increasing.

xx, 277 leaves : ill. ; 26 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.1974) from the Dept. of Plant Physiology, University of Adelaide

Thesis (Ph.D. 1974) from the Dept. of Plant Physiology, University of Adelaide.

Magister Scientiae (Biodiversity and Conservation Biology) - MSc (Biodiv and Cons Biol) / Randomized block experiments were conducted to examine the putative amelioratory effects of kinetin or gibberellic acid at concentrations (0, 4, 12.5, 40, and 125 μM) in Erucastrum strigosum plants subjected to a salinity series (0, 100, 200, 300, and 400 mM NaCl) in the greenhouse. When the highest salinity concentration (increased stepwise) was reached, growth effects in relation to water and cation content of the plants were evaluated. Growth and water content were reduced progressively with salinity treatments. Na+ concentration accumulated with salinity treatments to levels that were much higher than that of other cations (K+, Ca2+ and Mg2+) in both organs. However, it is noteworthy that Na+ distribution was more in shoots than in roots. In kinetin treated plants, shoot growth decreased whilst root growth increased with moderate hormonal treatments.