Dissertations / Theses on the topic 'Dormant buds'

Dormancy is one of the most important adaptive mechanisms developed by perennial plants, in order to survive the low temperatures of autumn and winter in temperate climates. The study of the genes regulated during dormancy release is crucial to understand the process, with the final objective of the development of new varieties with a better adaptation to certain environments; in particular in the Mediterranean area. The general aim of this work is to understand the molecular and physiological mechanisms underlying the maintenance and release of seasonal dormancy in peach. The first part of this work is focused on the identification of peach genes related to dormancy release by suppression subtractive hybridization (SSH) and microarray hybridization. A significant number of genes identified in this work were homologous to ABA and drought related genes from other species. Our data contribute to highlight a prominent role of ABA in dormancy processes and also uncover elements of the ABA and drought regulatory response in peach, as an ABA-INSENSITIVE5 (ABI5) binding protein (AFP)-like, a dehydration-responsive element (DRE)-binding protein (DREB2C)-like, a calcium-binding annexin, and several genes regulated by stress signalling pathways. Other identified genes were also evaluated to assess the chilling requirement of cultivars by analysis of expression showing a very good correlation between the expression pattern of DAM5, together with other transcripts (BD396, DB247, SB280 and PpB63) and the chilling requirements values of five different varieties ('Big Top', 'Catherina', 'Fergold', 'Maruja' and 'Springlady') measured following Utah and Dynamic models. Furthermore, a study of chromatin modifications associated to dormancy release in the DAM6 gene is presented. A ChIP analysis of DAM6 promoter and structural gene revealed chromatin modification events similar to those observed in vernalization of Arabidopsis and cereals.<br>Leida, CA. (2012). Molecular aspects of dormancy in peach (Prunus persica [L.] Batsch.) [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/15864<br>Palancia

A two year study examined Root Growth Potential (RGP) in a hydroponic system and Dormancy Release Index (DRI) in one-year-old (1-0) and two-year-old (2-0) eastern white pine (Pinus strobus L.), red pine (Pinus resinosa Ait.), and Scotch pine (Pinus sylvestris L.) seedlings with emphasis on eastern white pine. During 1985-86 all three species of 2-0 stock displayed a similar pattern of RGP with high levels of RGP limited to mid-March. Only 2-0 eastern white pine had a statistically significant relationship between RGP and DRI; however, this relationship was not consistent in 1986-87. The RGP/DRI relationship in 2-0 eastern white pine was strong over both years within a DRI range of 0.22 to 1.00. One-year-old and 2-0 eastern white pine stock had very different patterns of RGP over both years with 1-0 stock maintaining much wider "lifting windows" for high RGP. Cold storage (2C) of 2-0 eastern white pine resulted in variable effects on RGP although it typically progressed dormancy release. There were no strong RGP trends between northern and southern provenances of 1-0 eastern white pine and heritability values indicate that RGP is under minimal genetic control in 1-0 eastern white pine seedlings. Northern and southern provenances did display clear differences in seedling morphology and seasonal patterns of shoot activity. Results of a field outplanting study show that RGP does show promise as a measure of 2-0 eastern white pine seedling quality. The predictive ability of RGP was increased on non-irrigated versus irrigated seedlings. A comparison of greenhouse versus growthroorn RGP testing demonstrated the validity of using greenhouse RGP testing of 2-0 eastern white pine.<br>M.S.

Um die Erhaltung und Nutzung der beiden gefährdeten, hochwertigen Baumarten Pyrus pyraster und Sorbus torminalis zu fördern, wurden Methoden der in vitro Kultur und der Kryokonservierung evaluiert und optimiert. Kryokonservierung von Sorbus torminalis wird erstmalig beschrieben. Als Explantatquellen dienten Winterknospen, überwiegend von selektierten Bäumen aus Nachkommenschaftsprüfungen. Von den geprüften Faktoren Nährmedienzusammensetzung, Kulturgefäß, Schneidetechnik, Temperatur, Pikiertermin und physiologischer Zustand der Explantate erwies sich letzterer als entscheidend. Die Reiser mit den Winterknospen wurden in zwei aufeinander folgenden Jahren im November, Dezember, Januar, Februar und März geerntet und sowohl direkt als auch nach 2-monatiger Lagerung bei +5°C bearbeitet. Bei Pyrus führte Ernte im März zu den besten Ergebnissen der in vitro Kultur. Die besten Ergebnisse der Kryokonservierung wurden von Ernten im November bis Januar erzielt. Bei Sorbus differierten die Ergebnisse der in vitro Kultur zwischen den Jahren so stark, dass keine Aussage möglich war. Bei der Kryokonservierung waren die Erntetermine Dezember und Januar erfolgreich. Zur Kryokonservierung von in vitro Material wurden die Alginat-Einkapselung und die Droplet-Technik geprüft. Mit Pyrus wurden mit der Droplet-Technik Vitalitätsraten zwischen 7 und 13% erzielt, wenn eine bisher unveröffentlichte Kombination von Vorbehandlungen und PVS2-Vitrifizierung eingesetzt wurden. Die Kryokonservierung wirkte sich im Vergleich weder positiv noch negativ auf Wachstum und Entwicklung aus. Die Diskrepanz zwischen der Nutzung der tiefen Dormanz der Knospen und des damit verbundenen natürlichen Frostschutzes für die Kryokonservierung einerseits und der Vermeidung von tiefer Dormanz bei Etablierung von in vitro Kulturen wegen der damit verbundenen Wachstumshemmung andererseits wird diskutiert.<br>To facilitate conservation and utilization of the endangered valuable tree species Pyrus pyraster and Sorbus torminalis methods of in vitro culture and cryopreservation were evaluated and optimized. Cryopreservation of Sorbus torminalis is described for the first time. The explant sources were dormant winter buds, mainly from selected trees from progeny trials. The evaluation of media composition, culture vessel, cutting technique, date of pricking and physiological state proved the latter to be crucial. Twigs with winter buds were harvested in two subsequent years in November, December, January, February and March and were processed immediately and after two months of storage at +5°C. With Pyrus, the best results in in vitro culture were obtained after harvest in March while for cryopreservation harvest in November to January proved to be best. With Sorbus, the results in in vitro culture differed between the years and no conclusion could be drawn. Cryopreservation was successful after harvest in December and January. Encapsulation in alginate and the droplet-technique were evaluated for the cryopreservation of in vitro material. Vitality rates of 7 to 13% were achieved with Pyrus using the droplet-technique with a combination of pre-treatments and PVS2-vitrification not published so far. In comparison, cryopreservation was of neither positive nor negative influence on growth and development. The discrepancy between deep dormancy of buds being useful for cryopreservation because of its natural frost protection and the need to avoid it because it impedes in vitro culture is discussed.

Thesis (MSc)--Stellenbosch University, 2002.<br>ENGLISH ABSTRACT: The cultivation of table grapes in the warmer areas of South Africa, indeed worldwide, is complicated by rest breaking problems in spring due to delayed budbreak. In order to overcome these problems rest breaking agents, mainly hydrogen cyanamide, are applied. However, instead of alleviating the problem, additional problems such as uneven budbreak and reduced production are often induced. This study was initiated to further understand the physiological processes occurring during budbreak and how the application of hydrogen cyanamide influences these processes. The following aspects were investigated in this study: a. The effect of hydrogen cyanamide on tissue cytokinin (specifically zeatin riboside) levels of Sultanina table grape vines after application at different times before natural budbreak was studied over two seasons. In 1997, hydrogen cyanamide was applied at three weeks before induced budbreak and in 1998 at six weeks before induced budbreak. One year-old canes were sampled weekly after hydrogen cyanamide application, divided into distal and proximal sections, then further divided into buds, bark and wood tissues and the zeatin riboside (ZR) levels determined. A relatively high amount of chilling coupled to late hydrogen cyanamide application in 1997 led to a large effect on ZR release, but did not lead to significant shifting of the budbreak pattern. Zeatin riboside peaks were observed in buds, internode wood and bark of treated vines compared to control vines. The peaks were higher in distal portions compared to proximal portions in all tissues. The relatively lower chilling and earlier application of hydrogen cyanamide in 1998 had a larger effect on the budbreak pattern while the bud ZR peak was shifted earlier. The distal portion bud ZR . peak was again higher than the proximal portion bud ZR peak. In 1997, as sampling was not initiated early enough, bud ZR peaks were only observed after budbreak, while in 1998 bud ZR peaks were observed before and after budbreak. The effect of these ZR increases on the development of inflorescence primordia, subsequent bunch development and ultimately production, are discussed. b. Free xylem sap was sampled at cane and spur pruned lengths from unpruned canes of Sultanina from budswell until after budbreak in 1999 and from three table grape cultivars, i.e Sultanina, Alphonse Lavalleé and Sunred Seedless, in 2001 and ZR levels determined. The ZR levels in the buds of these three table grape cultivars, pruned to different cane lengths were also determined. One year old canes of these cultivars, were each pruned to long canes (14 buds) and short spurs (2 buds). The ZR content in buds of these canes at distal and proximal positions were determined weekly from budswell until after budbreak in 1999. Xylary ZR peaks occurred before 50% budbreak. Spur xylary ZR levels of all three cultivars followed a similar pattern, although at lower ZR levels than that of the canes. This is similar to previous studies on xylary ZR levels of apple shoots. The high levels of free ZR found in xylem sap at the distal portions of canes support the hypothesis of a cumulative ZR build-up effect as cane length increases. Spur pruning resulted in earlier budbreak and a higher final budbreak than cane pruning. The proximal portions of shoots, whether spur pruned or the proximal portions of canes, showed elevated ZR levels in all cultivars. This difference in ZR levels in bud tissue of different portions of the cane would suggest a difference in ZR consumption or turnover. The results of this study have important management implications for the cultivation of vines in warmer areas in which hydrogen cyanamide is used to alleviate budbreak problems.<br>AFRIKAANSE OPSOMMING: Die verbouing van tafeldruiwe in die warmer gebiede van Suid-Afrika, soos straks wêreldwyd, word bemoeilik deur rusbreekprobleme in die lente weens vertraagde bot. Rusbreekmiddels, meestal waterstofsiaanamied, word gevolglik toegedien om hierdie probleme te probeer oorkom. In plaas van opheffing van die probleem, veroorsaak hierdie toedienings somtyds addisionele probleme soos ongelyke bot en verlaagde produksie. Hierdie studie is aangepak om die fisiologiese prosesse wat tydens bot plaasvind, beter te verstaan, asook hoe die toediening van waterstofsiaanamied hierdie prosesse beïnvloed. Die volgende is in hierdie studie ondersoek: a. Die invloed van waterstofsiaanamied op lootweefsel sitokinien (naamlik zeatin ribosied, ZR) vlakke van 'n Sultanina tafeldruif wingerd is oor twee seisoene ondersoek na toediening op verskillende tye voor bot. Waterstofsiaanamied is in 1997 drie weke en in 1998 ses weke voor geïnduseerde bot toegedien. Een jaar oue lote is weekliks gemonster na waterstofsiaanamied toediening, verdeel in apikale en basale gedeeltes en verder verdeel in ogies, bas en houtweefsel en die ZR vlakke bepaal. Relatief hoër vlakke koue, gekoppel met later watersiaanamied toediening het in 1997 tot 'n groot effek op ZR vlakke gelei, maar het nie die botpatroon wesentlik verskuif nie. Zeatin ribosied pieke is waargeneem in ogies, internode hout en bas van behandelde wingerd in vergelyking met kontrole wingerd. Die pieke was hoër in apikale gedeeltes in vergelyking met basale gedeeltes in alle weefsels. Die relatief laer koue en vroeër toediening van waterstofsiaanamied in 1998 het 'n groter effek op die botpatroon gehad, terwyl die ogie ZR piek vroeër geskuif is. Die apikale gedeelte se ogie ZR piek was weereens hoër as die basale gedeelte se ogie ZR piek. Monstering was nie vroeg genoeg begin in 1997 nie, aangesien ogie ZR pieke slegs na bot waargeneem is, terwylogie ZR pieke in 1998 voor en na bot waargeneem is. Die effek van hierdie verhoging in ZR vlakke op die ontwikkeling van blom primordia, daaropvolgende tros ontwikkeling en uiteindelik produksie, is bespreek. b. Vry xileemsap is gemonster van langdraer en kortdraer gedeeltes van ongesnoeide lote van Sultanina vanaf ogieswel tot na bot in 1999 en vanaf drie tafeldruif kultivars, naamlik Sultanina, Alphonse lavalleé en Sunred Seedless, in 2001 en die ZR vlakke bepaal. Die ZR vlakke van ogies van hierdie drie kultivars, gesnoei tot verskillende lootlengtes is ook bepaal. Eenjarige lote van hierdie kultivars is gesnoei tot langdraers (14 ogies) en kortdraers (2 ogies). Die ZR vlakke in ogies geleë op apikale en basale gedeeltes van hierdie lote is weekliks in 1999 bepaal vanaf ogieswel tot na bot Xileemsap ZR pieke is waargeneem voor 50% bot. Kortdraer xileemsap ZR vlakke het 'n soortgelyke patroon as die langdraers gevolg vir al drie kultivars, alhoewel teen laer ZR vlakke as die langdraers. Hierdie waarneming is soortgelyk aan vorige studies op xileemsap ZR vlakke van appel lote. Die hoë ZR vlakke gevind in die xileemsap van die apikale gedeeltes van lote ondersteun die hipotese van 'n kumulatiewe opbou van ZR soos die lengte van die loot toeneem. Die snoei van lote as kortdraers het gelei tot vroeër bot en 'n hoër finale bot persentasie as die snoei van langdraers. Die basale gedeeltes van lote het verhoogde ZR vlakke in al drie kultivars getoon, onafhanklik van die feit dat dit vanaf die kortdraer of die basale gedeelte van 'n langdraer was. Hierdie verskil in ZR vlakke in ogie weefsel van verskillende gedeeltes van die loot impliseer 'n verskil in ZR verbruik of omset. The resultate van hierdie studie het belangrike bestuursimplikasies vir die verbouing van wingerd in warmer gebiede, waar waterstofsiaanamied gebruik word om botprobleme te oorkom.

Thesis (M.S.) -- University of Maryland, College Park, 2006.<br>Thesis research directed by: Dept. of Natural Resource Sciences and Landscape Architecture. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.

Le pommier (Malus Xdomestica Borkh.) cultivé en climat à hiver doux, avec un manque d'une quantité suffisante d'heures de températures froides, présente des anomalies morphologiques et physiologiques. Sur le plan de la phénologie, il s'agit notamment d'un débourrement printanier tardif et désynchronisé entre les différents bourgeons d'un même arbre. Sur le plan agronomique, la floraison et la nouaison sont irrégulières et étalées dans le temps et conduisent à une faible production de fruits. L'objectif de ce travail de thèse est premièrement de mieux caractériser les effets des températures hivernales sur le débourrement et la croissance des bourgeons axillaires en distinguant les effets respectifs des températures hivernales et du génotype. Il s'agit ensuite de vérifier l'hypothèse que les effets des températures sur le débourrement du bourgeon s'effectue via les effets sur son statut hydrique. Les travaux ont été réalisés en France et au Brésil. En France, les expérimentations ont porté sur quatre cultivars à fort besoin (‘Granny Smith', ‘Royal Gala', ‘Starkrimson') ou faible besoin (‘Condessa') en froid, cultivés en hiver froid (conditions extérieures) et doux (serres climatisées). Nous montrons que le débourrement résulte d'une séquence d'évènements où la température hivernale joue un rôle primordial sur les mécanismes de sortie de dormance et donc sur le débourrement proprement dit, durant la période froide. Les caractéristiques propres du cultivar jouent par contre un rôle dans la croissance ultérieure des bourgeons et donc dans l'architecture finale de la pousse du pommier. Par ailleurs, la chute tardive des feuilles, caractéristique du pommier en hiver doux, a peu d'effets sur le débourrement et la croissance des bourgeons. L'analyse du statut hydrique des bourgeons a été réalisée sur le tiers distal des pousses de pommier caractérisé par une forte fréquence de ramification en climat à hiver froid. Nous montrons que, dans la période allant de l'endordormance à la phase de pré-débourrement, la conductance hydraulique à la jonction entre l'axe porteur et le bourgeon varie peu au cours de l'hiver et entre cultivars. Par ailleurs, durant cette même période le potentiel hydrique intra-bourgeon reste négatif, entre -4.35 and -2.24 MPa. Enfin, quel que soit le cultivar, nous ne montrons pas de relation entre les températures hivernales, le potentiel hydrique ou la teneur relative en eau des bourgeons, et l'aptitude au débourrement ultérieur. Ces résultats suggèrent que le bourgeon est hydrauliquement isolé de son axe porteur pendant toute la période hivernale jusqu'à quelques jours précédant le débourrement. Les expérimentations au Brésil ont porté sur le cultivar ‘Eva ‘ à faible besoin en froid, cultivés en conditions naturelles d'hiver doux. Il s'agissait de vérifier les effets possibles de la position du bourgeon le long de l'axe porteur sur sa taille et sa teneur relative en eau. Nous montrons que, tout au long de l'hiver, les bourgeons distaux sont caractérisés par une plus grande taille et une teneur relative en eau plus élevée que les bourgeons proximaux avec une forte augmentation de la teneur relative en eau une semaine avant le débourrement printanier. Le débourrement acrotone semble donc résulter d'une évolution rapide du statut hydrique du bourgeon en fin d'écodormance. L'ensemble des résultats acquis en France et au Brésil, sur des cultivars caractérisés par des besoins variables en froid hivernal, indique que l'aptitude au débourrement printanier des bourgeons de pommier est davantage lié à un « effet rameau entier » qu'au statut hydrique proprement dit des bourgeons individuels, tout au moins jusqu'à quelques jours avant le débourrement effectif. La pousse annuelle de pommier apparait donc comme une unité morphologique et physiologique intégrée qui, dans un contexte climatique donné, conditionne le statut hydrique de chaque bourgeon et son aptitude au débourrement<br>The apple tree (Malus Xdomestica Borkh.) presents morphological and physiological anomalies when grown in mild winter climates with insufficient winter chilling to overcome winter dormancy. Symptoms are typically delayed and erratic budburst, entailing desynchronized flowering and fruit-set and poor agronomic performances. This thesis aimed at gaining more insights on the following issues. Firstly, what are the effects of winter temperatures on axillary burdburst and bud outgrowth, and what are the respective effects of winter temperatures and cultivar?, and secondly, is there a link between the temperature-dependent budburst and bud water status? Works were done in France and Brazil. In France, experiments were carried out in controlled conditions on four apple cultivars characterized by either high chilling (‘Granny Smith', ‘Royal Gala', ‘Starkrimson') or low chilling (‘Condessa') requirements and were submitted to outdoor-cold and greenhouse-mild winter temperatures. We showed that the actual shoot architecture and budburst resulted from an ordered sequence of events with a pivotal role of winter temperatures on the dormancy completion of individual lateral buds. Endogenous factors related to the cultivar branching pattern overtook the temperature effect on the lateral bud outgrowth. Furthermore, the delayed senescence and subsequent leaf persistence during winter, characterizing the apple tree in the mild winter temperature conditions, had only a weak effect on the topological distribution of budburst and lateral outgrowth. The analyses of bud water status were done on distal buds only, characterized by high budburst frequency in cold winter conditions. We showed that, from endodormancy to the pre-budburst stage, xylem conductance at the stem-to-bud junction did not show consistent changes across cultivars and winter temperature treatments. Bud water potential had negative values, between -4.35 and -2.24 MPa, depending on cultivars and winter temperature treatments. Moreover, whatever the cultivar, there were no significant trends across dates for the effects of winter temperatures on bud water potential and relative water content without a consistent relationship with actual spring budburst frequency. These results suggested that lateral buds were hydraulically isolated from the parent stem during winter until a few days before budburst. The other set of experiments was carried out in Brazil, under mild winter conditions, on the low chilling apple cultivar ‘Eva'. The objectives were to gain more insights on the effect of the position of the over-wintering lateral bud along the whole-parent shoot on bud size and water content. Results highlighted that distal buds were larger and had a higher water content than proximal buds with a strong increase of water content a week before spring budburst. It was concluded that the acrotonic pattern of budburst was mainly established during ecodormancy. As a whole, we showed that spring budburst seemed more related to a whole-shoot effect than to the water status of the individual bud during winter dormancy. Our study substantiated the importance of the whole shoot as an integrated morphological and physiological unit in driving budburst and further growth

Des recherches sur la micropropagation in vitro du muguet ont été envisagées pour répondre à 2 prothèses majeurs rencontrées dans les cultures traditionnelles : la faiblesse des taux de multiplication (2 à 3 par an) et la dégradation de l'état sanitaire des cultures avec leur âge. Différents types de tissus ont été introduits in vitro : boutons floraux, rachis de l'inflorescence et fragments de rhizomes. Les néoformations observées à partir des boutons floraux sont de type bouton floral en présence d'ana (1 à 4 mg/l) et d'une cytokinine à noyau purine (bap, kin, 2ip, z) ou à noyau urée (thidiazuron). La section longitudinale des boutons floraux a considérablement augmenté leur réactivité. Une phase de prolifération, qu'il est possible d'entretenir pendant une longue période, a été obtenue en présence de tdz (2 mg/l) et d'ana (1 mg/l). Des bourgeons végétatifs ont été régénérés sur des explants en phase de prolifération après transfert sur un milieu contenant de la bap (4 mg/l), en présence d'ana. Seulement 25% des explants ont régénéré des bourgeons végétatifs qui sont obtenus soit dormants soit en début de croissance aérienne. L'enracinement des bourgeons en début de croissance aérienne est réalisé après développement complet des feuilles sur un milieu dépourvu de régulateurs de croissance (pourcentage d'enracinement de l'ordre de 95%). Un traitement de 8 semaines a +4c permet la levée de dormance pour 98 à 100% des bourgeons. Apres enracinement le vitroplant va terminer son cycle végétatif in vitro. Lorsque la senescence des feuilles est complète, on obtient une vitrogriffe qui peut être plantée directement à l'extérieur. Par ailleurs, une approche de la conformité du matériel issu de culture in vitro a été effectuée par la détermination du nombre de chromosomes et par électrophorèse de protéines. Ce type d'étude a également permis la caractérisation de plusieurs variétés appartenant à l'espèce convallaria majalis L.

Thesis (M.S.)--University of Wisconsin--Madison, 2003.<br>Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 56-59).

碩士<br>國立臺灣大學<br>園藝學研究所<br>90<br>This study was carried out in Taipei (12 m elevation), Shinshou (500 m elevation), Kuohsin (500 m elevation) and Meifeng (2100 m elevation), from 2000 to 2001. Three peach cultivars were tested: high-chill cultivar ''Nakatsu Hakutoh'', low-chill cultivar ''Premier'' and local cultivar ''In-ge taur''. The objective of this study was to figure out phenology and dormancy performance of low-chill peach in subtropics. The dynamics of bud endodormancy were estimated by defoliation treatment and ''single node cuttings'' method. At Meifeng, buds of ''Nakatsu Hakutoh'' peach entered deeper dormancy gradually from August. Leaf buds sampled on 28 Feb 2001 whose break percentage of single node cuttings achieved 51% released from endodormancy. Endodormancy of flower buds was also broken in mid Feb. Dormancy of ''Premier'' peach at Meifeng was shallower and shorter than ''Nakatsu Hakutoh'' peach. Leaf buds of ''Premier'' peach entered endodormancy on 28 Nov. 2000. and released on 19 Dec. Flower buds released from endodormancy on 9 Jan, 2001. Budbreak percentage of ''Premier'' and ''In-ge taur'' peach trees grown in low altitude was often small. The growth capacity of leaf buds of ''Premier'' peach at Shinshou was weak from 14 Nov. to 28 Nov. 2000, as expressed by the budbreak percentage of defoliation treatment and single node cuttings. But buds of experimental plants in field broke naturally and successively from Oct. 2000 to Mar. 2001. The growth pattern of ''Premier'' at Shinshou was similar to overlapping double crops in Brisbane, Australia. In Taipei, Spraying chemical agent in Dec., Jan. and Feb. could defoliate ''Premier'' peach trees and advanced bud break. Terminal buds could growth until Nov. in greenhouse where air temperature was never lower than 20℃. We speculated that low-chill peach cultivar ''Premier'' do not enter endodormancy in low altitude in Taiwan.

[EN] The general aim of this thesis is to study the dormancy process from a molecular point of view identifying mechanisms and targeting genes that control it. In order to do that we have focused on the study of three genes that are differentially expressed during reproductive bud development within the conceptual framework of the three major processes that converge spatially and temporally in a reproductive bud: dormancy, stress tolerance and flower development. The first gene is down-regulated in dormancy release flower buds and encodes a STRESS ASSOCIATED PROTEIN (PpSAP1) that contains Zn-finger domains A20 and AN1. SAP proteins have been related to stress tolerance response in both plants and animals and in fact, we have shown that drought stress induces its expression in buds, resembling other SAP genes in plants. Moreover, the constitutive expression of PpSAP1 in plum increases its tolerance to water stress by increasing water retention. Likewise, transgenic plum plants show leaf alterations related to reduced cell size concomitant with the down-regulation of genes involved in cell growth. All these studies suggest a dual role of PpSAP1 in stress tolerance response and cell growth during peach dormancy. The second gene is PpeS6PDH, coding for an enzyme with sorbitol-6-phosphate dehydrogenase activity. PpeS6PDH is differentially regulated during bud development, highly expressed in dormant buds consistently with sorbitol accumulation. Concomitantly with PpeS6PDH down-regulation in dormancy-released flower buds, chromatin around the translation start site of the gene shows changes in the methylation state of specific residues of histone H3 (H3K4 and H3K27). These data suggest the transcriptional regulation of PpeS6PDH expression by chromatin modification mechanisms. Moreover, abiotic stresses affect PpeS6PDH expression. Low temperature treatments induce gene expression in buds and leaves, whereas desiccation up-regulates PpeS6PDH in buds and represses the gene in leaves. These data suggest the participation of PpeS6PDH in tolerance against cold and water deficit stresses in buds. Finally, the third gene is PpeDAM6, one of the major regulators of bud dormancy in peach. PpeDAM6 is sharply down-regulated during bud development concomitantly with dormancy release events. This repression is in part due to the direct binding of PpeBPC1, a BASIC PENTACYSTEINE PROTEIN, to the GAGA motifs present in an intronic regulatory region of PpeDAM6 gene that becomes enriched in H3K27me3 chromatin modification after dormancy release. In addition, the ectopic expression of PpeDAM6 in Arabidopsis shows abnormal flower phenotypes resembling 35S::SVP plants. On the other hand, overexpression in plum causes stunted growth in the transgenic lines due to an altered hormonal homeostasis. The changes in hormone content are mediated by the modulation of genes involved in jasmonic acid, cytokinins and gibberellic acid metabolism and signalling pathways. These results suggest that PpeDAM6 works as a master growth repressor maintaining dormancy, stress tolerance response and flowering inhibition by mainly modulating hormone homeostasis. Therefore, this thesis provides a dynamic snapshot of different molecular mechanism that take place inside the bud. The studied genes have a crucial role regulating dormancy processes, stress tolerance response and flowering pathways and all of them are potential candidate genes for breeding new plants more adapted to the climate change.<br>[ES] El objetivo general de esta tesis es el estudio de la latencia desde un punto de vista molecular, identificando mecanismos y genes diana que la controlen. Para ello, nos hemos centrado en el estudio de tres genes que se expresan de manera diferencial durante el desarrollo de una yema reproductiva en melocotón, bajo el marco conceptual de los tres procesos que convergen espacialmente y temporalmente en una yema reproductiva: latencia, tolerancia a estrés y desarrollo floral. El primer gen que se estudió codificó para una STRESS ASSOCIATED PROTEIN (PpSAP1) con dos dominios tipo Zn-finger, A20 y AN1 que disminuye su expresión durante la latencia. Las proteínas tipo SAP se han relacionado con resistencias a distintos tipos de estrés tanto en plantas como en animales. De hecho, se ha visto que PpSAP1 aumentó su expresión en yemas de melocotón bajo condiciones de estrés por sequía, de forma similar a como lo hacen otras SAP en distintas plantas. Además, la expresión ectópica de PpSAP1 en ciruelos transgénicos ha permitido aumentar la tolerancia a estrés hídrico en estas líneas al incrementar la cantidad de agua retenida. Asimismo, estas plantas transgénicas también mostraron alteraciones en el tamaño de las hojas, provocadas principalmente por una menor área celular de las células que formaban parte de ellas y relacionadas con una represión de distintos genes implicados en crecimiento celular. Todo ello sugiere que PpSAP1 probablemente tenga una doble función relacionada tanto con resistencia a estrés como con crecimiento celular durante la latencia de melocotonero. El segundo gen de estudio fue PpeS6PDH, el cual codifica para una enzima con actividad sorbitol-6-fosfato deshidrogenasa. PpeS6PDH está diferencialmente regulado durante el desarrollo de la yema, aumentando su expresión en yemas latentes de manera consistente a la acumulación de sorbitol. Simultáneamente a la disminución de PpeS6pDH en las yemas no latentes, alrededor del sitio de inicio de la traducción del gen se mostraron cambios a nivel de cromatina en el estado de metilación de los residuos específicos de la histona H3 (H3K4 y H3K27). Estos datos apuntan a la existencia de una regulación transcripcional de PpeS6PDH a nivel de modificaciones de la cromatina. Además, también se ha visto que distintos tipos de estrés abiótico afectan a la expresión de PpeS6PDH. Tratamientos con bajas temperaturas inducieron su expresión tanto en yemas como en hojas, mientras que la desecación aumentó la expresión en yemas pero no en hojas. Estos estudios sugieren que la función de PpeS6PDH durante la latencia de melocotonero es dar tolerancia a estrés por frío y sequía. Finalmente, el tercer gen de estudio fue PpeDAM6, uno de los mayores reguladores de la latencia en yemas de melocotonero. PpeDAM6 está fuertemente reprimido durante el desarrollo de la yema con una relación directa con los eventos de salida de latencia. Esta represión se debe en parte a la unión directa de PpeBPC1, una BASIC PENTACYSTEINE PROTEIN, a dos motivos GAGA presentes en la región intrónica reguladora de PpeDAM6. Justamente esta región se encuentra modificada a nivel de cromatina con un enriquecimiento en H3K27me3 después de la salida de latencia. Además, la expresión ectópica de PpeDAM6 en Arabidopsis mostró fenotipos de floración anormal parecidos a los producidos en plantas 35S::SVP. Por otro lado, la sobreexpresión en ciruelos provocó retrasos en el crecimiento de las líneas transgénicas, debido a una alteración en los niveles hormonales. Así mismo, se determinó que estos cambios en la homeostasis hormonal estaban producidos por la regulación diferencial de genes involucrados en las rutas del ácido jasmónico, las citoquininas y del ácido giberélico en las plantas transgénicas. Estos resultados sugieren que PpeDAM6 actúa como un represor máster del crecimiento, manteniendo la latencia, la respuesta de tolerancia a estrés y la inhibición floral a través de la regulación del equilibrio hormonal. Con todo ello, esta tesis proporciona una instantánea dinámica de los diferentes mecanismos moleculares que tienen lugar dentro de la yema. Los genes estudiados tienen una función crucial regulando tanto el proceso de latencia como la respuesta de tolerancia a estrés y las rutas de floración, y todos ellos son potenciales candidatos para mejorar nuevas plantas más adaptadas al cambio climático.<br>[CA] L'objectiu general d'aquesta tesi és l'estudi de la latència des d'un punt de vista molecular, identificant mecanismes i gens diana que la controlen. Per això, ens hem centrat en l'estudi de tres gens que s'expressen d'una manera diferencial durant el desenvolupament d'una gemma reproductiva en el préssec, sota el marc conceptual dels tres processos que convergeixen espacialment i temporalment en una gemma reproductiva: latència, tolerància a estrés i desenvolupament floral. El primer gen d'estudi codifica per a una STRESS ASSOCIATED PROTEIN (PpSAP1) amb dos dominis tipus Zn-finger, A20 i AN1, i disminueix la seua expressió durant la latència. Les proteïnes tipus SAP s'han relacionat amb resistències a diferents tipus d'estrés tant en plantes com en animals. De fet, s'ha vist que PpSAP1 va augmentar la seua expressió en gemmes de préssec sota condiciones d'estrés per sequia, de manera similar a com ho fan altres SAPs en diferents plantes. A més, l'expressió ectòpica de PpSAP1 en pruneres transgèniques ha permés augmentar la tolerància a estrés en aquestes línies en incrementar la quantitat d'aigua retinguda. Així mateix, aquestes plantes trnasgèniques també mostraren alteracions en la mida de les fulles, causades principalmente per una menor àrea cel¿lular de les cèl¿lules que formen part d'elles i relacionades amb una repressió de diferents gens implicats en el creixement cel¿lular. Tot aço, suggereix que PpSAP1 probablement tinga una doble funció relacionada tant amb resistència a estrés com amb creixement cel¿lular durant la latència del préssec. El segon gen d'estudi va ser una PpeS6PDH, la qual codificava per a un enzim amb activitat sorbitol-6-fosfato dehidrogenasa. PpeS6PDH està diferencialment regulada durant el desenvolupament de la gemma, augmentant la seua expressió en gemmes latents de manera consistent a l'acumulació de sorbitol. Simultàniament a la disminució de PpeS6PDH en les gemmes no latents, al voltant del lloc d'iniciació de la traducció del gen es van mostrar canvis a nivell de cromatina en l'estat de metilació dels residus específics de la històna H3 (H3K4 i H3K27). Aquestes dades assenyalen l'existència d'una regulació transcripcional de PpeS6PDH a nivell de modificacions de la cromatina. A més, també s'ha vist que diferents tipus d'estrés abiòtic afecten a l'expressió de PpeS6PDH. Tractaments amb baixes temperatures van induir la seua expressió tant en gemmes com en fulles, mentres que la desecació va augmentar l'expressió en gemmes però no en fulles. Aquests estudis suggereixen que la funció de PpeS6PDH durant la latència del préssec és donar tolerància a estrés per fred i sequia. Finalment, el tercer gen d'estudi va ser PpeDAM6, un dels majors reguladors de la latència en gemmes de préssec. PpeDAM6 està fortament représ durant el desenvolupament de la gemma amb una relació directa amb els events d'eixida de la latència. Aquesta repressió és deguda en part a la unió directa de PpeBPC1, una BASIC PENTACUSTEINE PROTEIN, a dos motius GAGA presents en la regió intrònica reguladora de PpeDAM6. Justament aquesta regió es troba modificada a nivell de cromatina amb un enriquiment en H3K27me3 després de l'eixida de latència. A més, l'expressió ectòpica de PpeDAM6 en Arabidopsis va mostrar fenotips de floració anormal semblants als produïts en plantes 35S::SVP. Per un altra banda, la sobreexpressió en pruneres va provocar retards en el creixement de les línies transgèniques a causa d'una alteració en els nivells hormonals. Aixi mateix, es va determinar que aquests canvis en l'homeostasi hormonal estaven produïts per la regulació diferencial de gens involucrats en les rutes d'àcid jasmònic, citoquinines i àcid gibberèl·lic en les plantes transgèniques. Aquests resultats suggereixen que PpeDAM6 actua com un repressor master del creixement, mantenint la latència, la resposta de tolerància a estrés i la inhibició floral a través de la regulació de l’equilibri hormonal. Com a conclusió, aquesta tesi proporciona una instantània dinàmica dels diferents mecanismes moleculars que tenen lloc dins de la gemma. Els gens estudiats tenen una funció fonamental, regulant tant el mateix procés de la latència com la resposta de tolerància a estrés i les rutes de floració i tots ells són potencials candidats per a millorar noves plantes més adaptades al canvi climàtic.<br>Lloret Compañ, A. (2020). A dynamic snapshot of bud dormancy in peach [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/153795<br>TESIS

碩士<br>國立臺灣大學<br>園藝暨景觀學系<br>104<br>The long high temperature period makes flower bud abortion. In this study, pruning and 49% cynamide applcaition were used to let new lateral shoot growth in autumn (August to October) and the shoot length, flower formation, and dormancy were investigated in ‘Shinko’ (Pyrus pyrifolia) in Zhou-Lan. The highest percentage of bud break occurred in August, and it decreased in October as the dormancy development. Flower buds could be found during August to October, but the new shoot length was only 10 cm, and the growth ceased after a short time. These kind of shoots are not good enough to be the pear scion next year. Temperature is the key point to bud dormancy. Three Asian pear, bird pear (P. lindleyi), ‘Heng-Shan’ (P. pyrifolia), and ‘Shinko’ (P. pyrifolia) were put into 15/13℃, 25/20℃, 25/20℃, and 30/25℃, respectively, for 180 days. The vegetative growth of bird pear in 30/25℃, 25/20℃ ceased after 60-75 days. The shoots growth in 20/15℃ stopped after 120 days. However, the vegetative growth last for 180 days in 15/13℃. The vegetative growth of ‘Heng-Shan’ in 30/25℃ and 25/20℃ ceased after 45-60 days. The shoots growth in 20/15℃ stopped after 120 days. However, the vegetative growth also last for 180 days in 15/13℃. The vegetative growth of ‘Shinko’ stopped after 45-60 days in all temperature treatments. The floral formation could be investigated in all 3 varieties in 30/25℃. Three shoots were cut per month after July (after 120-day investigation) in every variety in all treatment. The percentage of bud break were above 33% during July to September in three varieties. It suggests the dormancy stage may be between paradormancy and endodormancy stage in September. However, comparing the bud break ratio of the shoots from Zhou-Lan dereased from 60% to 38% during July to September. Analyzing the carbohydrates and nitrogen contents in the shoots from Zhou-Lan during July to November. The total soluble solid decreased and the starch increased to the highest level after September. It suggests the dormancy stage would be into endodormancy in September.

博士<br>國立中興大學<br>生命科學系所<br>98<br>Hydrogen cyanamide (HC) has been applied to break bud and seed dormancy in several crops. The effect of HC (0.5 and 1.0 M) on sprouting percentage, bud length, number of leaves and plant height of calla lily (Zantedeschia spp.) was investigated in the two cultivars Florex Gold and Pacific Pink. Results showed that tuber dormancy was released after 20 min treatment with 0.5 or 1.0 M concentration of the HC when the tubers were embedded into moistened media and moved into an incubator at 20℃for 20 days. The HC-treated tubers in two cultivars produced more sprouts, plant height and number of leaves after 8 week planting in greenhouse, compared with the control (untreated). Although both concentrations of HC release bud dormancy, HC at 0.5 M was the more suitable treatment. Meanwhile, sprouting time of HC-treated tubers in Florex Gold was 4 days earlier than that in Pacific Pink. Calla lily tubers from summer season producted with the tubers have long dormancy period. Carbohydrates were measured in apical region, medulla region and cortex region from Pacific Pink to determine whether concentrations change after HC treated （0.5 M）colored calla lily tubers. Obsevations on paraffin-embedded sections of colored calla lily tuber tissues treated with 0.5 M HC for 2 days showed imbibition formed in medulla region and cortex region cells. Starch degraded from medulla by inner of vascular ring. HPLC analysis showed that decreases in the level of sucrose within medulla region, and change in maltose had occurred. In addition, the level of glucose and fructose were increased with increasing activities of meristem and tuber sprouting. The response of the antioxidant enzymes activities and metabolites of ascorbate-glutatione pathway to oxidative stress caused by HC was studied in Pacific Pink cultivar treated with 0.5 M HC at dark conditions for 0-16 days. Total superoxide dismutase (SOD), dehydroascorbate reductase (DHAR) and glutathione reductase (GR) enzyme activities increase under HC induced, whereas monodehydroascorbate reductase (MDHAR) enzyme activity decreased. Therefore, these results infer reactive oxygen species (ROS) induced by HC treatment in colored calla lily belong to the metabolisms of SOD and ascorbate-glutatione cycle. On the other hand, we also infer ascorbate-glutatione cycle may be a DHAR reduced pathway because MDHAR is a negative regulation. However, MDHAR played a role in tuber dormancy release needs more research.

Some ill. mounted<br>Bibliography: leaves 198-215<br>xv, 215 leaves, [4] leaves of plates : ill. (some col.) ; 30 cm.<br>Title page, contents and abstract only. The complete thesis in print form is available from the University Library.<br>Thesis (Ph.D.)--University of Adelaide, Dept. of Plant Physiology, 1985

博士<br>國立臺灣大學<br>園藝學研究所<br>103<br>Three experiments were conducted to improved high quality pear production at lowland areas in Taiwan. I. Effect of altitude on flower bud formation and necrosis in ‘Shinko’ pears in subtropical Region. Time-specific responses of flower bud formation were investigated in ‘Shinko’ (Pyrus pyrifolia Nakai) pear grown at two altitudes from July through December 2013 in order to determine the suitability of using them as scions in the top-grafting system. Flower bud formation and bud necrosis were determined on each of three sections of one-year-old shoots: terminal, middle, and basal. Flower bud visible started in September in the highland of Li-Shan area, whereas in July in the lowland of Zhou-Lan area. In Li-Shan area, flower bud formation was higher in the middle and basal segments during growing season. However, flower bud formation occurred rapidly in the terminal segment after leaf fall. Flower buds began to development from the terminal segment of the shoot and severe flower bud necrosis was noted in Zhou-lan area. Flower buds developed normally in July however, some of the buds at the basal segment showed browning in early August. During leaf fall, some flower buds showed the symptoms of necrosis with rapid and complete browning. Flower bud necrosis began at the basal segment and progressed rapidly towards middle and terminal sections. Before leaf fall, flower buds fell off when scales swelled. The terminal and middle parts of the current-year shoots Collected on October or later from Li-Shan area, with some flower buds, could be used as scions for top-grafting of ''Shinko'' pear. Each grafting scion is a 3-5cm shoot with one flower bud. Those shoot collected from Zhou-Lan area show necrosis and might not be suitable as scions. II. Effect of cold storage duration on bud-burst and flowering of ‘Shinko’ pear scion. Current year shoot of ‘Shinko’ pear were collected in January, November and December, 2013, respectively, from Li-Shan and Zhou-Lan. Materials were sterilized by 8-HQS for 10 minutes, then stored in 5°C for 0, 2, 4, 6, 8 weeks for those collected in January 2013, and 0, 2, 4, 6 weeks for those collected in November and December Bud burst and flowering ratio were investigated after storage. Ten one-bud-cutting with similar length were incubated in growth chamber at 20/15°C condition for each treatment. The results showed that the bud from Li-Shan sprouted after one week in all treatments and had 90% bud burst rate for those stored for 4 and 6 weeks in the material collected in January, Those collected in November and December after 4-weeks cold storage was the best treatment, which had almost 90% bud bursting. The highest flowering rate of the materials from Li-Shan area was 60%, 40% and 40% for January, November, and December samples, respectively. Both bud burst and flowering rate of shoots collected from Zhou-Lan were low. The shoots from Zhou-Lan area are not suggested to be used due to the low flowering rate and high chilling requirement. III. The potassium to magnesium ratio enables the prediction of water core during cold storage of asian pears Taichung No. 2’ is a new Asian pear cultivar developed in Taiwan with low chilling requirement; however, is likely to develop water core under low temperature storage conditions. The impact of storage time on flesh water core in pears were investigated fruits were harvested from 22 orchards in 2010 and 2011, and analyzed the levels of nutrients in different fruit parts such as the peel, flesh, and core. Calcium and potassium contents were higher in the flesh and peel, respectively, of more severely browned fruits, whereas a lower magnesium content was recorded in the peel and core of these fruits. Nitrogen and potassium contents in the peel, and calcium content in the flesh were positively correlated with the water core severity level. In contrast, the magnesium content in the core was negatively correlated with the water core severity level. However, the nutrient contents in fruits varied between the two sampling years considered. Only the K/Mg ratio was an effective predictor of the water core severity and showed a positive linear correlation in the two years. We recommend that the K/Mg ratio should be lower than 10 to avoid severe water core in pears.