Understanding the dynamical bases of the interaction between the plant mineral nutrition and the circadian clock could contribute to improve crop yield and resistance to adverse conditions, such as mineral element deficiencies. Magnesium is an essential element that catalyzes more than six hundred enzymatic reactions and occupies the center of the chlorophyll structure in plants. Physiological targets of magnesium deficiency are generally better described in aerial than in belowground organs. In this thesis, we first characterized the root morphology of the model species Arabidopsis thaliana (Columbia-0) in response to magnesium supply during in vitro culture. The length of primary root and the number and length of lateral roots decreased during magnesium depletion. A local magnesium-rich source does not enhance the root foraging capacity, unlike some other major nutrients. Auxin and abscisic acid emerged as two hormones shaping root morphology in response to magnesium deficiency. Second, we investigated the natural variation of the root morphology response to magnesium supply in Arabidopsis. Thirty-six accessions were screened in vitro. Compared to the reference Columbia-0, some accessions had higher number and length of lateral roots at low magnesium supply. Root or shoot magnesium concentrations did not implicitly correlate with the root morphological traits. However, shoot calcium and root phosphorus concentrations correlated positively with the lateral root number and length, while root iron negatively with the length of primary root. Third, we focused on the interaction between the plant magnesium nutrition and the circadian clock circuit. We tested for a possible involvement of PHYTOCHROME INTERACTING FACTOR 3-LIKE 1 (PIL1) - a clock-associated gene that is down-regulated during magnesium depletion - in morphological and physiological responses, and for a circadian connection of PIL1 in the context of magnesium deficiency. The phenotypes of loss-of-function and overexpression lines did not reveal a major role of PIL1 in the magnesium deficiency symptom manifestation but rather in the plant mineral profile. The expression of PIL1 was apparently not under any circadian control. However, PIL1 seemed to regulate the expressions of some core clock genes (CCA1, LHY and PRR9), which were also targets during magnesium deficiency. In conclusion, PIL1 has a link with the circadian rhythm machinery but it does not emerge as a pivotal regulator of magnesium stress responses. / Doctorat en Sciences / info:eu-repo/semantics/nonPublished

Made available in DSpace on 2014-06-11T19:22:16Z (GMT). No. of bitstreams: 0 Previous issue date: 2012-02-24Bitstream added on 2014-06-13T19:48:26Z : No. of bitstreams: 1 figueiredo_pg_me_botfca.pdf: 864751 bytes, checksum: 77b495899b271a3df8c49ee115f500a4 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Características físicas do solo como porosidade, retenção de água, densidade e resistência a penetração são influenciadas diretamente pelo tipo de preparo do solo. Em resposta a estas modificações ocorrem adaptações morfofisiológicas das raízes. Verifica-se na literatura relatos sobre a influência de diferentes tipos de preparos do solo na produção e na qualidade culinária de raízes de mandioca cultivadas em diferentes tipos de solo, entretanto são desconhecidos os fatores, pertinentes às raízes, que determinam essas diferenças, o que leva a hipótese de que estes fatores possam ser de ordem morfo-anatômica. Diante disso, objetivou-se através deste trabalho de pesquisa estudar a influência de três tipos de preparo do solo (cultivo mínimo, plantio convencional e plantio direto) nas características físicas do solo, produção, morfologia e anatomia de raízes tuberosas de Manihot esculenta Crantz cultivar IAC 576-70. Para isso foi conduzido um experimento a campo em delineamento experimental de blocos ao acaso com parcelas subdivididas e seis repetições. Foram consideradas as causas de variação os tratamentos, preparos do solo, a saber: cultivo mínimo (CM), preparo convencional (PC) e plantio direto (PD) e a idade da planta, em dias após o plantio (DAP). No delineamento experimental os preparos do solo foram considerados parcelas e as idades da planta ou épocas de amostragens as subparcelas, neste experimento foram avaliados a micro, macro e porosidade total, teor de água e resistência a penetração do solo, número, comprimento, diâmetro, massas fresca e seca, porcentagem... / Soil physical characteristics such as porosity, soil water content, bulk density and penetration resistance are directly affected by tillage. In response to these changes occur roots’ morpho-physiological adaptations. In the literature there are reports about the influence of different tillage on the cassava root yields and culinary qualities affected by soil types. However the factors inner roots which determine these differences are unknown, which leads to the hypothesis that these factors may be morphological or anatomical. So the objective of this work was to study the influence of three tillage types (minimum tillage, conventional tillage and no tillage) on soil physical properties, yield, morphology and anatomy of Manihot esculenta Crantz, cultivar IAC 576-70 roots. For those was conducted a field experiment, which experimental design was randomized block in split-plot with six replications. That were considered variation causes, the treatments: minimum tillage (MT), conventional tillage (CT) and no tillage (NT) and plant age, in days after planting (DAP). In the experiment the treatments, tillages, were considered the plots and the subplots were established by plant ages or times of sampling (DAP). In this experiment were evaluated micro, macro and total porosity, soil water content and soil penetration resistance, number, length, diameter, fresh and dry weight, percentage of dry mass, morphological and anatomical characteristics and the proportion of tissues that make up the cassava tuberous roots at different ages of the plant. From the results of these evaluations there was possible to conclude that he order of setting of yield components of sweet cassava cv. IAC 576-70 are independent of tillage, and are defined in the following order: number of root, length, diameter, fresh weight, dry weight... (Complete abstract click electronic access below)

The need to curb increased pollution of environmental resources caused by excessive nitrogen (N) fertilizer application and N fertilizer use inefficiencies in wheat (Triticum aestivum) production systems warrants an inexpensive, sustainable, environmentally sound solution, the root system. Wheat germplasm containing the short arm of rye chromosome 1 (1RS) has recently been found to have larger root system sizes in pot experiments in addition to previously documented higher yields and resistance to leaf, stem and yellow rust. These 1RS lines could therefore be useful in wheat breeding efforts targeting superior root system traits for yield improvements as well as environmental and economic benefits. This dissertation evaluated field root biomass production of Pavon 76 and its wheat-rye (1RS) translocations, effects of root biomass on nitrogen use efficiency, and the temporal variation in their root morphological traits and early growth vigor. The translocation 1RS.1BL had 9 and 23 % higher total root biomass than Pavon 76 at jointing and physiological maturity respectively. Root N uptake peaked at the jointing, where it comprised 22-34% of the total plant N uptake and was lowest at physiological maturity for all genotypes. The inclusion of root N uptake reduced the N utilization efficiency and N harvest index by 6-14 and 7-15% respectively, indicating that the use of only the above ground plant parts over estimates these parameters. In pot experiments, the translocation 1RS .1AL had 12 and 39% higher root biomass than Pavon 76 at anthesis and maturity respectively. 1RS.1BL had 38% higher root mass and 16% longer roots than Pavon76 at physiological maturity. This suggests the existence of differences among the genotypes in below ground partitioning of assimilates at peak nutrient demand (anthesis) for grain filling, and also in rates of root decay and senescence. The lack of differences in root morphological traits among genotypes at early growth stages (6-46 days after sowing) indicates that there are minimal differences in early root growth vigor. The 1RS translocations could therefore expand the wheat breeder's tool box in selections for superior root traits for improved NUE without adverse effects on grain yield.

Orientador: Silvio José Bicudo / Coorientador: Marina Aparecida de Moraes Dallaqua / Banca: Teresa Lousada Valle / Banca: Mario Takahashi / Resumo: Características físicas do solo como porosidade, retenção de água, densidade e resistência a penetração são influenciadas diretamente pelo tipo de preparo do solo. Em resposta a estas modificações ocorrem adaptações morfofisiológicas das raízes. Verifica-se na literatura relatos sobre a influência de diferentes tipos de preparos do solo na produção e na qualidade culinária de raízes de mandioca cultivadas em diferentes tipos de solo, entretanto são desconhecidos os fatores, pertinentes às raízes, que determinam essas diferenças, o que leva a hipótese de que estes fatores possam ser de ordem morfo-anatômica. Diante disso, objetivou-se através deste trabalho de pesquisa estudar a influência de três tipos de preparo do solo (cultivo mínimo, plantio convencional e plantio direto) nas características físicas do solo, produção, morfologia e anatomia de raízes tuberosas de Manihot esculenta Crantz cultivar IAC 576-70. Para isso foi conduzido um experimento a campo em delineamento experimental de blocos ao acaso com parcelas subdivididas e seis repetições. Foram consideradas as causas de variação os tratamentos, preparos do solo, a saber: cultivo mínimo (CM), preparo convencional (PC) e plantio direto (PD) e a idade da planta, em dias após o plantio (DAP). No delineamento experimental os preparos do solo foram considerados parcelas e as idades da planta ou épocas de amostragens as subparcelas, neste experimento foram avaliados a micro, macro e porosidade total, teor de água e resistência a penetração do solo, número, comprimento, diâmetro, massas fresca e seca, porcentagem... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Soil physical characteristics such as porosity, soil water content, bulk density and penetration resistance are directly affected by tillage. In response to these changes occur roots' morpho-physiological adaptations. In the literature there are reports about the influence of different tillage on the cassava root yields and culinary qualities affected by soil types. However the factors inner roots which determine these differences are unknown, which leads to the hypothesis that these factors may be morphological or anatomical. So the objective of this work was to study the influence of three tillage types (minimum tillage, conventional tillage and no tillage) on soil physical properties, yield, morphology and anatomy of Manihot esculenta Crantz, cultivar IAC 576-70 roots. For those was conducted a field experiment, which experimental design was randomized block in split-plot with six replications. That were considered variation causes, the treatments: minimum tillage (MT), conventional tillage (CT) and no tillage (NT) and plant age, in days after planting (DAP). In the experiment the treatments, tillages, were considered the plots and the subplots were established by plant ages or times of sampling (DAP). In this experiment were evaluated micro, macro and total porosity, soil water content and soil penetration resistance, number, length, diameter, fresh and dry weight, percentage of dry mass, morphological and anatomical characteristics and the proportion of tissues that make up the cassava tuberous roots at different ages of the plant. From the results of these evaluations there was possible to conclude that he order of setting of yield components of sweet cassava cv. IAC 576-70 are independent of tillage, and are defined in the following order: number of root, length, diameter, fresh weight, dry weight... (Complete abstract click electronic access below) / Mestre

Softwood cuttings of Euonymus alatus and the cultivar Rudy Haag, a nearly seedless cultivar, were taken in Kentucky on two cutting dates. E. alatus Rudy Haag cuttings taken in mid-May, untreated or treated with 1000 - 3000 ppm IBA, produced many roots on a high percentage of cuttings. Post-rooting shoot growth was reduced for the species with cuttings taken in June. Rudy Haag produced new growth on cuttings taken in May with no IBA treatment. Transplanting resulted in a decrease in new growth. Liner plants of E. alatus Compactus and Rudy Haag were planted into 1 and 3 gallon containers of two different types, conventional black plastic and root training. A second experiment exposed plants to two levels of supplemental fertilizer in addition to slow release. A subsample was sprayed with Fascination (BA + GA4+7) at 1500 ppm in late July. No difference was seen in above-ground growth due to container type or supplemental fertilizer. A change in root morphology is seen with root trainers. Three gallon containers produced a larger plant than one gallon containers. Rudy Haag sprayed with Fascination were greater in size and branch number than those not sprayed.

The aim of this study was to establish a classification system for use in immediate implant placement by examining fresh extraction sockets in maxillary premolars and evaluation of the varying morphologies using CBCT imaging. Selection criteria included dentulous patients ages 15-85 that had CBCT imaging taken for varying treatment. A total of 400 maxillary premolars were classified by their root morphology as Type I (two-rooted premolar with interradicular bone), II (fused roots with mesiodistal alveolar constriction) or III (single blunted root with no interradicular bone). The internal root angle was measured for all Type 1 maxillary first premolars (n=40), as well as the interradicular septal bone height. A Type 1 premolar socket is present in 32% of the sampled maxillary first and second premolars. Type 2 socket was present in 22% of premolars, and type 3 socket was present in 46% of premolars. The average internal angle formed between the long axis of the crown versus the long axis of the palatal root was 11.46 ± 4.35° (range 4° to 20.7°). The average interradicular septal bone height was of 6.9 ± 1.6 mm (range 3.28 to 9.61). Type I root form had the highest incidence at maxillary first premolars sites and has the most alveolar bone available, thus having a higher probability for primary stability. The type III root form is most common in the maxillary second premolar site and has the least amount of alveolar support for immediate implant placement. The angulation and alveolar bone support provided by the palatal root in Type I root form maxillary first premolar sites may provide stability for an immediate implant at an appropriate prosthetic position.

With the increasing scarcity of water resources, soil moisture stress is the single most threat to global soybean production causing extensive yield losses. The objectives of this study were to investigate soil moisture stress effects on all aspects of soybean growth and development processes and to develop functional algorithms that could be used for field management decisions and in soybean crop modeling. To fulfill these objectives, six experiments were conducted; one in vitro osmotic stress study on seed germination, four studies by imposing five soil moisture treatments, 100, 80, 60, 40, and 20% of daily evapotranspiration of the control at different growth stages using sunlit plant growth chambers, and one transgenerational study on seed germination at different osmotic levels and offspring growth at three irrigation treatments (100, 66, and 33% based on field capacity) for plants grown at different soil moisture levels. Two cultivars from maturity group V, Asgrow AG5332 and Progeny P5333RY, with different growth habits were used in all these studies. Midday leaf water potential, plant height, mainstem nodes, gas-exchange traits, canopy reflectance, and several yield components including pod weight, seed yield, and seed quality were measured. Soil moisture stress decreased biomass, net photosynthesis, yield, individual seed weight, maximum seed germination, protein, fatty acids, sucrose, N, and P and increased oil, stachyose, Fe, Mg, Zn, Cu, and B contents. Overall, Asgrow AG5332 was more tolerant to drought stress than Progeny P5333RY. Soil moisture stress induced changes in seed quality that were correlated with seed germination and seedling vigor in the F1 generation. These data can be used to build a model-based decision support system capable of predicting yield under field conditions.

The purpose of this study was to determine the effects of amendments (control, (1x) compost, (2x) compost, (TS) topsoil, and 1x+TS) and microtopography (level, pit and mound) on three parameters (plant species composition, above-ground characteristics of Taxodium distichum, and plant root characteristics) of vegetation growing at a created tidal freshwater swamp in Virginia. None of the soil treatments met the traditional vegetation criteria for federal wetland jurisdictional determination, which only considers dominant species. When the same criteria were used for all of the species, the control, 1x, and 2x treatments met jurisdictional criteria. Considering these findings, vegetative criteria should be re-evaluated for young created wetlands. Compost addition produced the highest proportion of obligate wetland species (30%) while topsoil additions created the lowest proportion of wetland obligates (11%) and the highest proportion of upland plants. The 1x treatment generated the greatest species evenness and lowest weighted average (2.57). Topsoil treatments had the lowest diversity and evenness. Therefore, compost amendment is recommended to increase hydrophytes without compromising evenness and diversity. Bald cypress in pits were taller, had larger trunk diameter and basal trunk swelling than trees growing at higher elevations. Roots growing in mounds were more numerous with greater length than roots at lower elevations. Root length and count were highest for the control soil treatment. Amended treatments may have had lower rooting values because nutrient supply was adequate. Overall, incorporating microtopography and compost during wetland creation had a positive effect on vegetative function in this system. / Master of Science

Mineral-associated organic carbon (MAOC) is a vital component of soil health and ecosystem productivity, playing a key role in carbon (C) sequestration and nutrient cycling. This dissertation investigates how plant root traits, nitrogen (N) fertilization, and cover cropping influence soil organic carbon (SOC) and MAOC. In the first chapter, a greenhouse experiment with 30 herbaceous plant species found that non-N-fixing plants exhibited stronger positive correlations with MAOC compared to N-fixing species, which were more closely linked to SOC. Root biomass contributed to decreases in MAOC, while specific root length (SRL), and coarse root traits were found to significantly contribute to increases in MAOC, highlighting the importance of plant root architecture in stabilizing C. In the second chapter which focused on relationships among N-fertilization, root traits, and MAOC, moderate N fertilization (56 and 112 kg N/ha) was found to enhance total SOC (∆SOC) and MAOC (∆MAOC) accumulation in the system, while higher N inputs (168 kg/ha) reduced C gains. Notably, the use of stable isotopes allowed for the quantification of fresh C additions, with results that indicate plant-added MAOC (PA-MAOC) was influenced more by plant species and root traits, such as coarse root length and aboveground biomass, rather than N fertilization. In the third chapter, a long-term field study demonstrated the effectiveness of cover cropping in increasing both SOC and MAOC by 43–59% and 27–36%, respectively, compared to conventional and no-till systems without cover crops. Despite triennial additions of N fertilizer over nine years, no significant increases in SOC or MAOC was observed. Additionally, root biomass exhibited positive trends with MAOC. These findings suggest that cover cropping, combined with no till practices, plays a pivotal role in enhancing MAOC by minimizing soil disturbance and promoting root-driven C inputs. This research highlights the importance of integrating plant species selection, root morphological traits, N management, and conservation practices to optimize long-term C storage (i.e., MAOC) and support sustainable soil management. Future studies should continue to include MAOC and particulate organic carbon fractions as these functional C sub pools may respond differently than bulk SOC pool. Including further studies on the interactions between root morphology, environmental factors, and C/N dynamics is necessary to develop more resilient agroecosystems capable of mitigating C losses and improving long-term soil health. / Doctor of Philosophy / This dissertation explores soil organic carbon, an important component of soil organic matter, which is vital for soil health and fertility. Soil organic matter promotes plant growth and agricultural productivity, and is critical for mitigating climate change by acting as a carbon sink, absorbing carbon dioxide from the atmosphere, which is why maintaining and building soil carbon is important. Soil carbon that is bound to minerals such as clays, is referred to as mineral-associated carbon (MAOC), which holds the largest pool of carbon on land and is often believed to persist over longer time-scales. Cover crops, their plant roots, and nitrogen fertilizer may have different relationships with MAOC when compared to total soil carbon, and these responses are not well understood. To address some of these knowledge gaps, this dissertation measured MAOC, plant root traits such as root size and structure, among different types of plants commonly used in agriculture and land reclamation practices. Results from this work show that root traits play an important role in increasing MAOC during short-term plant growth, with different effects depending on whether the plants can fix nitrogen from the air. Nitrogen fertilization was found to strongly impact MAOC, with moderate levels increasing amounts of MAOC, but low or too much nitrogen caused losses. Additionally, plant traits like root and stem biomass had a stronger influence on fresh carbon inputs from plants to the soil versus nitrogen alone. Cover crops proved to be a highly effective strategy for improving MAOC storage over 9 years, while additional nitrogen fertilizer had little long-term effect. These findings highlight the importance of balancing plant selection, fertilization, and sustainable practices to maintain healthy, carbon-rich soils.

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