京都大学 / 0048 / 新制・課程博士 / 博士(農学) / 甲第19051号 / 農博第2129号 / 新制||農||1033(附属図書館) / 学位論文||H27||N4933(農学部図書室) / 32002 / 京都大学大学院農学研究科農学専攻 / (主査)教授 白岩 立彦, 教授 奥本 裕, 准教授 中﨑 鉄也 / 学位規則第4条第1項該当 / Doctor of Agricultural Science / Kyoto University / DFAM

Bromus tectorum, an invasive winter annual, has displaced native vegetation throughout the western United States. Bromus tectorum litter influences nutrient cycling near the soil surface as well as plant establishment. Failed seed production of B. tectorum occasionally occurs in the field, with plants exhibiting weak flowering culms that turn straw-colored in spring when normal plants are green or purple in color. Because annual grasses transport most soluble carbon (C) and nitrogen (N) to reproductive organs, seed production failure results in significantly different fates for these nutrients compared with normal plants. As part of larger efforts to understand events leading to large-scale seedling emergence failure (termed die-offs), occasionally observed in near mono-cultures of B. tectorum, we here test the hypothesis that prematurely senesced litter associated with seed production failure has higher soluble C and N than normal litter. C and N concentrations of aboveground biomass were compared for normal and prematurely senesced B. tectorum plants. Two methods were used to cause premature senescence: fungal pathogen infection with Clarireedia capillus-albis and glyphosate herbicide application. In a related experiment, field sampling of normal and prematurely senesced plants under natural conditions was conducted to compare C and N levels in-situ. Herbicide-induced senescence resulted in 1.5 to 2 times greater soluble C concentrations, but fungal infection had no effect on soluble C under experiment conditions. Prematurely senesced litter had increased total N concentrations, resulting in lower C:N ratios. The C:N ratio for prematurely senesced plants (averaged across all studies) was 68:1, whereas mature normal plants averaged 243:1. These findings illustrate failed seed production associated with premature senescence results in B. tectorum litter with significantly higher N concentrations and can result in increased soluble C concentrations. Altered nutrient status may contribute to changes in soil microbial activity, including activity of soilborne pathogens found in die-offs.

Flooding is a major environmental stress that damages agricultural production worldwide. Using the key regulator of submergence tolerance in rice, SUB1A, as a model, we have advanced our understanding of how plants coordinate transcriptional, hormonal, and metabolic responses to submergence. However, the contribution of SUB1A to recovery from sublethal submergence is still unknown. This study revealed SUB1A's additional role in the recovery phase: promotion of a rapid return to normal metabolic status upon desubmergence through quick recovery of photosystem II photochemistry and carbon fixation. We also investigated how SUB1A differentially regulates adaptive responses in two functionally distinct leaves, growing and mature leaves, under submergence. This study revealed that rice plants promote rapid carbohydrate and nitrogen remobilization and transport in mature leaves, supporting quick elongation growth of growing leaves. In the presence of SUB1A, these metabolic processes were suppressed in mature leaves, resulting in the avoidance of energy starvation in the source tissues. In growing leaves, SUB1A enhanced the accumulation of abscisic acid, but repressed the level of ACC, a precursor of ethylene, contributing to the restriction of elongation growth and leaf senescence in the sink tissues. Application of nitrogen fertilizers is a necessary step to maintain high grain yield in cereals, but plants absorb only 30-50% of supplied N. Wheat, one of the most widely grown crops in the world, requires a high level of nitrogen application to maintain grain yield and protein content. In this study, we investigated how nitrogen input affects the accumulation of major N and C compounds and expression of genes associated with N and C metabolism in flag leaves of wheat. We used two genotypes with distinct nitrogen use efficiencies (NUE), VA08MAS-369 and VA07W-415. VA08MAS-369 displayed higher grain yield, stover biomass, and stover N content at low N, which results from greater N-uptake efficiency in this genotype. Consistently, high N-uptake efficiency was reflected by increased mRNA accumulation of nitrate transporters and their transcriptional regulator, NAC2, in flag leaves at the post-anthesis stage. Overall, this study advanced our knowledge of the important mechanisms in plant response to flooding and N limitation in these key staple cereals. / PHD / Flooding is a serious natural disaster that damages agricultural production worldwide. Rice is a wetland plant that adapts to flooding conditions, but its tolerance to flooding varies in cultivars. Functional characterization of a submergence tolerance gene, SUB1A, has led to our understanding of various mechanisms that regulate flooding tolerance in rice and other plants. However, the role of SUB1A in plant recovery from mild submergence stress is still unknown. This study revealed that SUB1A contributes to the maintenance of photosynthetic performance and provides protection from sudden exposure to high light after floodwater subsides. These processes aid in a quick recovery from reduced metabolic activities. We also investigated the role of SUB1A in adaptive responses in growing and mature leaves of rice plants during submergence. Mature and growing leaves looked similar, but their functional importance was distinct. In general, mature leaves serve as energy production tissues through photosynthesis. The excess carbohydrate and nitrogen reserves produced in mature leaves are transferred to growing leaves that consume a large amount of energy for rapid growth. This study revealed that SUB1A restricted the consumption and transfer of energy reserves in mature leaves to avoid an energy crisis. In growing leaves, SUB1A suppressed elongation growth and leaf senescence through the proper regulation of key hormones controlling these processes. Nitrogen (N) fertilizer application is a necessary process to improve agricultural productivity in many crops. However, crops only take up 30-50% of applied N, resulting in water and air pollution and altered ecosystems. Improvement of plant N use efficiency (NUE) is one of the ways to address this issue. This study compared two soft red winter wheat lines with contrasting NUE under low and normal N supply. It was concluded that one line, VA08MAS-369, had higher grain yield and N uptake efficiency under low N supply. Our physiological and molecular study indicated that VA08MAS-369 significantly promoted N remobilization in leaves and N transport to grains after flowering under limited N. This study advanced our understanding of NUE mechanisms in winter wheat, which may aid the development of new cultivars with enhanced NUE through modern biotechnological approaches.

京都大学 / 0048 / 新制・課程博士 / 博士(農学) / 甲第21835号 / 農博第2348号 / 新制||農||1068(附属図書館) / 学位論文||H31||N5207(農学部図書室) / 京都大学大学院農学研究科農学専攻 / (主査)教授 白岩 立彦, 教授 稲村 達也, 准教授 田中 朋之 / 学位規則第4条第1項該当 / Doctor of Agricultural Science / Kyoto University / DFAM

Cette thèse en électronique moléculaire porte essentiellement sur le développement d’une méthode pour le calcul de la transmission de dispositifs électroniques moléculaires (DEMs), c’est-à-dire des molécules branchées à des contacts qui forment un dispositif électronique de taille moléculaire. D’une part, la méthode développée vise à apporter un point de vue différent de celui provenant des méthodes déjà existantes pour ce type de calculs. D’autre part, elle permet d’intégrer de manière rigoureuse des outils théoriques déjà développés dans le but d’augmenter la qualité des calculs. Les exemples simples présentés dans ce travail permettent de mettre en lumière certains phénomènes, tel que l’interférence destructive dans les dispositifs électroniques moléculaires. Les chapitres proviennent d’articles publiés dans la littérature. Au chapitre 2, nous étudions à l’aide d’un modèle fini avec la méthode de la théorie de la fonctionnelle de la densité de Kohn-Sham un point quantique moléculaire. De plus, nous calculons la conductance du point quantique moléculaire avec une implémentation de la formule de Landauer. Nous trouvons que la structure électronique et la conductance moléculaire dépendent fortement de la fonctionnelle d’échange et de corrélation employée. Au chapitre 3, nous discutons de l’effet de l’ajout d’une chaîne ramifiée à des molécules conductrices sur la probabilité de transmission de dispositifs électroniques moléculaires. Nous trouvons que des interférences destructives apparaissent aux valeurs propres de l’énergie des chaînes ramifiées isolées, si ces valeurs ne correspondent pas à des états localisés éloignés du conducteur moléculaire. Au chapitre 4, nous montrons que les dispositifs électroniques moléculaires contenant une molécule aromatique présentent généralement des courants circulaires qui sont associés aux phénomènes d’interférence destructive dans ces systèmes. Au chapitre 5, nous employons l’approche « source-sink potential » (SSP) pour étudier la transmission de dispositifs électroniques moléculaires. Au lieu de considérer les potentiels de sources et de drains exactement, nous utilisons la théorie des perturbations pour trouver une expression de la probabilité de transmission, T(E) = 1 − |r(E)|2, où r(E) est le coefficient de réflexion qui dépend de l’énergie. Cette expression dépend des propriétés de la molécule isolée, en effet nous montrons que c’est la densité orbitalaire sur les atomes de la molécule qui sont connectés aux contacts qui détermine principalement la transmission du dispositif à une énergie de l’électron incident donnée. Au chapitre 6, nous présentons une extension de l’approche SSP à un canal pour des dispositifs électroniques moléculaires à plusieurs canaux. La méthode à multiples canaux proposée repose sur une description des canaux propres des états conducteurs du dispositif électronique moléculaire (DEM) qui sont obtenus par un algorithme auto-cohérent. Finalement, nous utilisons le modèle développé afin d’étudier la transmission du 1-phényl-1,3-butadiène branché à deux rangées d’atomes couplées agissant comme contacts à gauche et à la droite. / This thesis is on molecular electronics concentrates mostly on the development of a method for the calculation of the transmission probability of molecules that are connected to contacts. On the one hand, this method aims at bringing a different point of view among the other methods for such calculations. On the other hand, it allows the integration of already developed theoretical tools in a rigorous manner, which increases the quality of the calculations. The work presented here often contains simple examples that shine some light on phenomena, such as the destructive interference, in molecular electronic devices. The chapters are from articles already published in the litterature. In chapter 2, we study a molecular quantum dot using a finite model with Kohn-Sham density functional theory. Moreover, using an implementation of the Landauer formula, we calculate the conductance of the quantum dot. We find that the electronic structure and molecular conductance depend strongly on the exchange and correlation functional employed. In chapter 3, we discuss the effect of adding a side chain to conducting molecules on the transmission probability of molecular electronic devices. We find that destructive interferences appear approximately at the energy eigenvalues of the isolated side chain, if these values do not correspond to localized states far away from the conductor. In chapter 4, we show that molecular electronic devices containing an aromatic molecule generaly possess circular currents which are associated with destructive interference phenomena in these systems. In chapter 5, we use the source-sink potential (SSP) approach to study the electronic transmission of some devices. Instead of considering the source and sink potentials exactly, we use perturbation theory to find an expression for the transmission probability T(E) = 1 − |r(E)|2 that depends on the properties of the bare molecule, where r(E) is the energy-dependent reflection coefficient. We show that in the first-order, it is the orbital density on the atoms connected to the contacts that largely determines the transmission probability for a given incoming electron energy. In chapter 6, we present an extension of the single channel source-sink potential approach for molecular electronic devices to multiple channels. The proposed multichannel method relies on an eigenchannel description of the conducting states of the molecular electronic device, which are obtained by a self-consistent algorithm. We use the model to study the transport of the 1-phenyl-1,3-butadiene molecule connected to two coupled rows of atoms that act as contacts on the left and right sides.

Disputats. Rheinische Friedrick-Wilhelms-Universität, 2001. / Haves kun i elektronisk udg.

Thesis (MScAgric)--Stellenbosch University, 2013. / ENGLISH ABSTRACT: The relationships between leaf and fruit represent a fundamental concept in perennial plants. This concept allows to understand and to manage, with regard to farming, the balance of a vine, which is important in terms of fruit quality (i.e. fruit composition), mainly when it comes to producing wines of different categories and styles. The understanding of vine structure, physiology and vine functioning ultimately allows for appropriate recommendations to be given with regard to farming procedures. These include the adaptation of the canopy architecture to achieve a certain yield per vine, the determination of an appropriate fruit microclimate as well as the prediction of harvest dates. One of the central notions of vine balance involves the relationship between the source and the sink organs. The definition of source-sink relationships incorporates several concepts, including the ability of a source tissue to produce carbohydrates through photosynthesis, the transport of these carbohydrates to various plant organs-tissues via appropriate transport channels, and the assimilation and storage of the carbohydrates in the sink organs. In past years, a number of simple ratios have been created to incorporate the relationship between source and sink organs and thereby define vine balance in order to aid in practical management decisions (choice of a training system, irrigation, canopy manipulation etc.). However, vine functioning is very complex and cannot be defined accurately by simple, static ratios. More integrated and dynamic physiological indicators of vine balance and functioning are needed in order to understand the complex communication between organs and ultimately improve on farming practices. In order to achieve this, a better grasp of source-sink relationships, including the signalisation between organs and the functioning of the transport tissues is required. A two year experiment was proposed to study the interaction between source and sink organs using a combination of both primary shoot girdling methods and berry classification according to size. Girdling removes the bark and phloem tissue, thereby interrupting carbon import as well as water flow to the bunch to a certain degree. The aim of the study was to demonstrate the complexity of vine functioning by investigating the dynamics of berry sugar and water accumulation (used as physiological indicators) and the influence thereof on berry fresh mass evolution. Furthermore, the use of berry sugar loading was proposed as an improved physiological indicator of vine balance as it is directly linked to source and sink functioning. Sugar production and the dynamics of berry sugar accumulation rely on photosynthesis which in turn is dependent on stomatal conductance and therefore also incorporates the effects of external abiotic factors (temperature, light and water). It furthermore gives a direct indication of sink functioning as it shows the progressive accumulation of sugar throughout the ripening period and the possible consequences on berry volume evolution. A primary shoot which bore two bunches was used to represent a biological replicate. The lower bunches were girdled above and below in order to completely isolate them from any carbohydrate import. These bunches, along with the upper ungirdled bunches and two control bunches from another shoot were sampled. The berries from these bunches were classified according to diameter, thereby providing the unique opportunity to study berries of the same volume/size. Measurements were done to determine the fresh and dry masses of the sampled berries, as well as to analyse the concomitant sugar concentrations. It was found that girdling clearly had an effect on berry sugar dynamics and the method was improved in the second year of the trial. Girdling in interaction with berry classification according to diameter demonstrated that berries from the same size could have different sugar concentrations. It further showed that, to a certain degree, a relationship exists between the first rapid phase of sugar accumulation and the post véraison increase in berry fresh mass, until the plateau of fruit sugar accumulation, which generally occurs around a sugar concentration of 20 Brix. Additionally, and more importantly, it was found that vine functioning and the balance between the source and the sink organs may be controlled to a certain degree. There is a strong degree of compensation within a vine which results from signalling between and within organs. When taking the results of this study into consideration, it becomes clear that the classical ratios used to quantify the complex relationships between the fruit and the leaves may not be completely adequate to do so. The current way of looking at source-sink relationships and thereby determining whether a vine is balanced or not is over-simplified and there are numerous limitations involved in this approach. The vine is far more complex and various aspects must be taken into consideration before any claims can be made concerning source-sink relationships and consequently leaf to fruit balance. / AFRIKAANSE OPSOMMING: Die verhoudings tussen blaar en vrug verteenwoordig ‘n fundamentele konsep in meerjarige plante. Begrip van hierdie konsep maak dit moontlik om in boerdery die balans van ‘n wingerdstok te verstaan en bestuur. Hierdie wingerdbalans is belangrik in terme van vrugkwaliteit (d.w.s. vrugsamestelling), hoofsaaklik met betrekking tot die produksie van wyne van verskillende kategorieë en style. Begrip van die wingerdstok se struktuur, fisiologie en funksionering maak dit moontlik om gepaste aanbevelings te maak rakende boerdery prosedures. Dit sluit in die aanpassing van die lower argitektuur om ‘n sekere opbrengs per wingerdstok te verkry, die vasstel van ‘n geskikte vrug mikroklimaat asook die voorspelling van oesdatums. Een van die sentrale denkwyses rondom wingerdstok funksionering behels die die bron-vragpunt verhouding. Die definisie van bron-vragpunt verhoudings inkorporeer verskeie konsepte, insluitende die vermoë van ‘n bronweefsel om koolhidrate te produseer deur fotosintese, die vervoer van hierdie koolhidrate na verskeie plantorgaan weefsels via die gepaste vervoerkanale asook die opname en berging van hierdie koolhidrate in die vragpunt organe. In die verlede is ‘n aantal eenvoudige verhoudings geskep om die verband tussen die bron en vragpunt organe te beskryf en sodoende die wingerdstokbalans te definieer met die doel om ondersteuning te bied in praktiese bestuursbesluite (die keuse van opleistelsel, besproeiing, lowermanipulasie, ens.). Wingerdstok funksionering is egter baie kompleks en kan nie akkuraat gedefinieer word deur eenvoudige, statiese verhoudings nie. Meer geïntegreerde en dinamiese fisiologiese aanwysers van wingerdstokbalans en funksionering is nodig om die komplekse kommunikasie tussen organe te verstaan en uiteindelik boerdery praktyke te verbeter. Om dit te bereik is ‘n beter begrip van bron-vragpunt verhoudings asook die seinoordrag tussen organe en die werking van die vervoerweefsels nodig. ‘n Twee jaar lange eksperiment is voorgestel om die interaksie tussen bron- en benuttingsorgane te ondersoek deur gebruik te maak van beide die primêre loot ringelering metode en korrel klassifikasie volgens grootte. Ringelering verwyder die bas en floëem weefsel en onderbreek sodoende koolstof invoer sowel as watertoevoer na die tros tot ‘n sekere mate. Die doel van die studie was om die kompleksiteit van wingerdstok funksionering aan te toon deur die dinamika van suiker en water akkumulasie in die korrel te ondersoek asook die invloed daarvan op korrel vars massa ontwikkeling. Verder is die gebruik van korrel suikerlading voorgestel as ‘n beter fisiologiese aanduiding van wingerdstok funksionering aangesien dit direk geassosieer is met bron-vragpunt funksionering. Suikerproduksie en die dinamika van suiker akkumulasie in die korrel berus op fotosintese wat weer afhanklik is van stomatale geleiding en daarom ook die effek van eksterne abiotiese faktore (temperatuur, lig en water) inkorporeer. Dit gee verder ‘n direkte aanduiding van die funksionering van die vragpunt organe omdat dit die progressiewe akkumulasie van suiker gedurende die rypwordingsperiode aantoon, asook die moontlike gevolge op korrelvolume ontwikkeling. ‘n Primêre loot wat twee trosse dra is gebruik om ‘n biologiese herhaling te verteenwoordig. Die laer trosse is bo en onder geringeleer om hulle heeltemal te isoleer van enige koolhidraat invoer. Hierdie trosse, tesame met boonste ongeringeleerde trosse en twee kontrole trosse vanaf ‘n ander loot is gemonster. Die korrels van hierdie trosse is geklassifiseer volgens hulle deursnee, om sodoende die unieke moontlikheid daar te stel om korrels van dieselfde volume/ grootte te bestudeer. Metings is gedoen om die vars en droë massas van die gemonsterde korrels te bepaal, asook om die gepaardgaande suikerkonsentrasies te analiseer. Daar is gevind dat ringelering duidelik ‘n effek gehad het op korrelsuiker dinamika en die metode is verbeter in die tweede jaar van die proef. Ringelering in wisselwerking met korrel klassifikasie volgens korrel deursnee het aangetoon dat korrels met dieselfde grootte verskillende suikerkonsentrasies kon hê. Dit het verder aangedui dat daar, tot ‘n sekere mate, ‘n verhouding bestaan tussen die vinnige fase van suiker akkumulasie en die na-véraison toename in korrel vars massa, totdat die plato in suiker akkumulasie bereik word, gewoonlik rondom ‘n suikerkonsentrasie van 20 Brix. Daarbenewens, en van groter belang, is gevind dat wingerdstok funksionering en die balans tussen die bron en vragpunt organe onder ‘n mate van beheer is. Daar is ‘n sterk mate van kompensasie binne ‘n wingerdstok wat die gevolg is van seinoordrag tussen en binne organe in die wingerdstok. Wanneer die resultate van hierdie studie in aanmerking geneem word, word dit duidelik dat die klassieke verhoudings, wat gebruik word om wingerdstok funksionering en balans mee te bepaal, moontlik nie beduidend betekenisvol is nie. Die wyse waarop bron-vragpunt verhoudings tans beskou word is, tot ‘n mate, ‘n oorvereenvoudiging en daar is heelwat beperkinge betrokke by hierdie benadering. Die wingerd is baie meer kompleks en verskeie aspekte moet in aanmerking geneem word voordat enige bewering gemaak kan word rakende bron-vragpunt verhoudings. / The University of Stellenbosch and Winetech for financial support

Coffee (Coffea arabica L.) nutrient demand depends on fruit load and intensity of the annual variation of vegetative growth. However, nutrient rates recommended for this crop are based only on bean yield, manily yields of old crops. Therefore, this research aimed to determine the source-sink relationship, through the effect of fruit load on vegetative growth, to understand coffee nutritional demand. The hypotheses were (i) the annual biomass of stem, branches and leaves should have a strong negative linear relationship regarding fruit load, (ii) the average nutrients concentration changes in the vegetative plant part due to the number of fruits, and (iii) the plant nutrient demand varies in years of high and low production due to the different proportions between fruiting and annual vegetation. The study was carried out from November 2015 to June 2016 in coffee trees in the municipality of Jacuí - MG, Brazil. The experimental design was completely randomized with one factor (fruit load), six factor levels (100%, 80%, 60%, 40%, 20% and 0%) and five replicates. After flowering, in early November 2015, six fruit loads were manually imposed and the base of the last pair of fully expanded leaf was labeled with wire on all branches of the trees. In early June 2016, during the coffee harvest, branches were cut from the wire-label and characterized. The variables analyzed were: numbers of nodes, leaf area, dry vegetation yield, dry bean yield, volume of fruits and concentration of macro and micro nutrients in vegetation and fruiting. The study revealed that fruit load strongly affects vegetative growth in Coffee arabica L. For each liter of fruit produced, ~ 103 g of dry vegetation yield decreases per tree. Furthermore, the concentration of the macronutrients N, P, K, Mg and S and the micronutrients Mn, Fe, Cu and Zn in vegetation and fruiting not dependent on fruit load. Nutrient demand of a given plant density varies in years of high and low production due to the different yield proportions of mass between fruiting and annual vegetation. / A demanda de nutrients do cafeeiro (Coffea arabica L.) depende da carga de frutos e da intensidade da variação anual do crescimento vegetativo. No entanto, as doses de nutrientes recomendadas para a cultura são baseadas apenas na produtividade de frutos, especialmente produtividades de lavouras antigas. Portanto, o objetivo principal desta pesquisa foi determinar a relação fonte-dreno, por meio do efeito da carga de frutos no crescimento vegetativo, para compreender a demanda nutricional do café. As hipóteses foram (i) a biomassa vegetativa anual teria uma forte relação linear negativa em função da carga de frutos, (ii) a concentração média de nutrientes seria variável na parte vegetativa da planta devido à quantidade de frutos e (iii) a demanda de nutrientes variaria em anos de alta e baixa produção devido às diferentes proporções entre frutificação e vegetação anual. O experimento foi realizado de novembro de 2015 a junho de 2016 em Jacuí - MG, Brasil. O delineamento experimental foi inteiramente casualizado com um fator (carga de frutos), seis níveis do fator (100%, 80%, 60%, 40%, 20% e 0%) e cinco repetições. Após o florescimento, no início de novembro de 2015, as seis cargas de frutos foram aplicadas manualmente e a base do último par de folhas totalmente expandidas foi marcada com um arame indicador em todos os ramos das plantas. No início de junho de 2016, durante o período de colheita do café, os ramos foram cortados a partir do arame indicador e caracterizados. As variáveis analisadas foram: número de nós, área foliar, massa seca da vegetação, massa seca de frutos, volume de frutos e concentração de macro e micronutrientes na vegetação e na frutificação. O estudo revelou que a carga de frutos afeta fortemente o crescimento vegetativo de Coffee arabica L. Para cada litro de fruto produzido a planta deixa de vegetar ~ 103 g de massa seca. Além disso, as concentrações dos macronutrientes N, P, K, Mg e S e os micronutrientes Mn, Fe, Cu e Zn na vegetação e na frutificação não dependeram da carga de frutos. A demanda de nutrientes de uma dada densidade de plantas varia em anos de alta e baixa produção devido às diferentes proporções de produção de massa entre frutificação e vegetação anual.

Les relations entre l'activité de la source et l'activité du puits contrôlent en grande partie la croissance des plantes. Ces activités varient au cours du développement, mais aussi en réponse à des changements des conditions environnementales. Notre étude avait pour but d'identifier le rôle du métabolisme carboné dans la réponse de la croissance d'E. americanum à la modulation des activités de la source et du puits. Dans une première partie, l'activité du puits est modulée par la température de croissance. Aux fortes températures, l'activité du puits est plus élevée, alors que sa capacité est réduite. Ces effets, dus à la modulation du métabolisme du saccharose, mènent à une saturation précoce en amidon des bulbes à forte température. Par la suite, la baisse de la demande en carbone du puits induit un rétrocontrôle négatif de l'activité photosynthétique et finalement, la sénescence foliaire. À l'inverse, l'activité du puits à faible température est en rythme avec l'accroissement de la capacité, menant à une biomasse supérieure du bulbe en fin de croissance épigée. Dans une seconde partie, l'activité de la source est modulée en changeant la concentration en CO2 et en O3. Malgré la stimulation de la source sous fort CO2 et son inhibition sous fort O3, l'accumulation d'amidon et la biomasse du bulbe ne sont pas affectées. En effet, le surplus de carbone parvenant au puits est brûlé par la voie alternative de la respiration, celle-ci étant stimulée par l'activité de l'enzyme malique. La voie alternative de la respiration évite ainsi une saturation hâtive en amidon et éventuellement, une sénescence foliaire précoce. Dans une dernière partie, l'activité de la source est modulée par l'irradiance et la photopériode. L'accumulation d'amidon varie en fonction de la photopériode alors que l'irradiance n'a aucun effet. De plus, l'activité photosynthétique est inhibée très précocement sous longue photopériode. Cette inhibition semble due à un déséquilibre entre la quantité totale de carbone fixé par jour et son utilisation suite à son transfert au sein du bulbe. Nous pouvons donc conclure que les régulations du métabolisme carboné permettent d'ajuster l'activité du puits à la capacité de celui-ci chez l’E. americanum / Relationships between source and sink activities largely control the growth of plants. Both activities vary during development as well as in response to changes in environmental conditions. The aim of our study was to identify the role carbon metabolism plays in the response of E. americanum growth to changes in source and sink activities. Firstly, sink activity is modulated by changing growth temperature. Sink activity is higher at higher temperatures, whereas sink capacity is more restricted. These effects, due to the modulation of sucrose metabolism, lead to an earlier starch saturation of bulbs at higher temperature. Thereafter, the reduction in carbon sink demand induces a feedback inhibition of photosynthetic activity and finally, leaf senescence. In contrast, sink activity at low temperature is more in rhythm with the increasing sink capacity, leading to larger bulbs at the end of the epigeous growth season. Secondly, source activity is modulated by changing CO2 and O3 concentrations. Despite a stimulation of the source activity under high CO2 and its inhibition under high O3, neither plant growth nor starch accumulation was affected. Indeed, excess carbon translocated within the sink is burned by the alternative respiratory pathway. This pathway is stimulated by malic enzyme. Alternative respiratory pathway thus avoids an early starch saturation of the bulb and eventually, an early leaf senescence. Finally, source activity is also modulated by changing irradiance and photoperiod regimes. Starch accumulation changes in response to photoperiod but not to irradiance. Furthermore, photosynthetic activity is inhibited early in the season under long photoperiod. This inhibition seems due to an imbalance between the total amount of carbon fixed per day and its utilisation following translocation to the bulb. We can thus conclude that regulation of carbon metabolism allow to adjust sink activity to sink capacity in E. americanum.

Coffee (Coffea arabica L.) nutrient demand depends on fruit load and intensity of the annual variation of vegetative growth. However, nutrient rates recommended for this crop are based only on bean yield, manily yields of old crops. Therefore, this research aimed to determine the source-sink relationship, through the effect of fruit load on vegetative growth, to understand coffee nutritional demand. The hypotheses were (i) the annual biomass of stem, branches and leaves should have a strong negative linear relationship regarding fruit load, (ii) the average nutrients concentration changes in the vegetative plant part due to the number of fruits, and (iii) the plant nutrient demand varies in years of high and low production due to the different proportions between fruiting and annual vegetation. The study was carried out from November 2015 to June 2016 in coffee trees in the municipality of Jacuí - MG, Brazil. The experimental design was completely randomized with one factor (fruit load), six factor levels (100%, 80%, 60%, 40%, 20% and 0%) and five replicates. After flowering, in early November 2015, six fruit loads were manually imposed and the base of the last pair of fully expanded leaf was labeled with wire on all branches of the trees. In early June 2016, during the coffee harvest, branches were cut from the wire-label and characterized. The variables analyzed were: numbers of nodes, leaf area, dry vegetation yield, dry bean yield, volume of fruits and concentration of macro and micro nutrients in vegetation and fruiting. The study revealed that fruit load strongly affects vegetative growth in Coffee arabica L. For each liter of fruit produced, ~ 103 g of dry vegetation yield decreases per tree. Furthermore, the concentration of the macronutrients N, P, K, Mg and S and the micronutrients Mn, Fe, Cu and Zn in vegetation and fruiting not dependent on fruit load. Nutrient demand of a given plant density varies in years of high and low production due to the different yield proportions of mass between fruiting and annual vegetation. / A demanda de nutrients do cafeeiro (Coffea arabica L.) depende da carga de frutos e da intensidade da variação anual do crescimento vegetativo. No entanto, as doses de nutrientes recomendadas para a cultura são baseadas apenas na produtividade de frutos, especialmente produtividades de lavouras antigas. Portanto, o objetivo principal desta pesquisa foi determinar a relação fonte-dreno, por meio do efeito da carga de frutos no crescimento vegetativo, para compreender a demanda nutricional do café. As hipóteses foram (i) a biomassa vegetativa anual teria uma forte relação linear negativa em função da carga de frutos, (ii) a concentração média de nutrientes seria variável na parte vegetativa da planta devido à quantidade de frutos e (iii) a demanda de nutrientes variaria em anos de alta e baixa produção devido às diferentes proporções entre frutificação e vegetação anual. O experimento foi realizado de novembro de 2015 a junho de 2016 em Jacuí - MG, Brasil. O delineamento experimental foi inteiramente casualizado com um fator (carga de frutos), seis níveis do fator (100%, 80%, 60%, 40%, 20% e 0%) e cinco repetições. Após o florescimento, no início de novembro de 2015, as seis cargas de frutos foram aplicadas manualmente e a base do último par de folhas totalmente expandidas foi marcada com um arame indicador em todos os ramos das plantas. No início de junho de 2016, durante o período de colheita do café, os ramos foram cortados a partir do arame indicador e caracterizados. As variáveis analisadas foram: número de nós, área foliar, massa seca da vegetação, massa seca de frutos, volume de frutos e concentração de macro e micronutrientes na vegetação e na frutificação. O estudo revelou que a carga de frutos afeta fortemente o crescimento vegetativo de Coffee arabica L. Para cada litro de fruto produzido a planta deixa de vegetar ~ 103 g de massa seca. Além disso, as concentrações dos macronutrientes N, P, K, Mg e S e os micronutrientes Mn, Fe, Cu e Zn na vegetação e na frutificação não dependeram da carga de frutos. A demanda de nutrientes de uma dada densidade de plantas varia em anos de alta e baixa produção devido às diferentes proporções de produção de massa entre frutificação e vegetação anual.