Early maturity is one of the most important aerial growth traits next to bunch size, in determining banana productivity. However, low seed fertility in banana and the lack of breeding lines limit the application of conventional breeding for this trait. Genetic transformation with a CyclinD2-type gene, responsible for the CyclinD2 protein sub unit, which modulates the cell cycle progression at the G1/S phase, enhanced growth of tobacco plants. On this basis, investigations were carried out on the possibility of increasing the growth rate of banana plants through transformation with and expression of a CyclinD2- type coding sequence. Arabidopsis thaliana;CyclinD2;1 (Arath;CycD2;1) gene and its banana ortholog were over-expressed in banana to test their growth enhancement potential. The banana CyclinD2;1 (Musac;CycD2;1) was isolated from an East African highland cooking banana (AAA) cultivar “Nakasabira” and a cDNA was created by PCR using degenerated primers which was followed by genome walking. Characterization of the banana cyclin protein revealed an IWKVHAHY motif that was found to be conserved across the Musaceae family. Phylogenic analysis revealed a higher protein sequence identity of this banana cyclin to CyclinD2;1 of monocot plants than that of Arabidopsis. This cyclin was also found to be expressed highly in meristematic tissue which linked it to the cell cycle. The coding sequence was submitted to the GeneBank under accession number HQ839770. Arabidopsis and banana CyclinD2;1 gene coding sequences under the control of a constitutive promoter were used to transform embryogenic cells of the banana cultivar “Sukalindiizi” (AAB) using the Agrobacterium transformation system. A higher relative expression of Arath;CyclinD2;1 was found in the shoot than in the root apices and expression reduced transcript amounts of the endogenous banana CyclinD2;1. Plants of transformed banana line D2-41 had the highest Arath;CyclinD2;1 transcript amount and exhibited a significantly faster leaf elongation rate, better root growth, faster first leaf opening and a bigger lamina composed of bigger epidermal cells than non-transformed control plants. Banana plants transformed with Musac;CyclinD2;1 had a higher transcript amount of the transgene in the root apices when compared to the shoot apices. The higher transcript amount in the roots of plants of transformed line NKS-30 was related to faster root growth and development of an extensive root system. Overall, this study has provided evidence that expression of cyclin coding sequences in transformed banana is related to growth promotion. Specifically, Arath;CyclinD2;1 promoted shoot growth while the Musa homolog promoted root growth. Shoot and root growth phenotypes obtained in this study might have the potential to improve banana productivity in terms of short plant growth cycle, increased bunch weight, improved plant anchorage and increased plant resistance to root nematode damage. Future work should assess the produced plants in the field to allow transformed plants to exhibit their full potential and to be able to fully evaluate the vegetative and flowering phases. / Thesis (PhD)--University of Pretoria, 2012. / Plant Science / unrestricted

Root systems are a fundamental concept in the theory of Lie algebra. In this thesis, we will use two different kind of graphs to represent the group generated by reflections acting on the elements of the root system. The root systems we are interested in are those of type A2, B2 and G2. After drawing the graphs, we will study the algebraic groups corresponding to those root systems. We will use three different techniques to give a geometric description of the homogeneous spaces G/P where G is the algebraic group corresponding to the root system and P is one of its parabolic subgroup. Finally, we will make a link between the graphs and the multiplication of basis elements in the Chow group CH(G/P).

Increasing salinity is a worldwide problem, but the knowledge on how salt enters the roots of plants remains largely unknown. Non-selective cation channels (NSCCs) have been suggested to be the major pathway for the entry of sodium ions (Na+) in several species. The hypothesis tested in this research is that PQ loop (PQL) proteins could form NSCCs, mediate some of the Na+ influx into the root and contribute to ion accumulation and the inhibition of growth in saline conditions. This is based on previous preliminary evidence indicating similarities in the properties of NSCC currents and currents mediated by PQL proteins, such as the inhibition of an inward cation current mediated by PQL proteins by high external calcium and pH acidification. PQL family members belonging to clade one in Arabidopsis and barley were characterized using a reverse genetics approach, electrophysiology and high-throughput phenotyping. Expression of AtPQL1a and HvPQL1 in HEK293 cells increased Na+ and K+ inward currents in whole cell membranes. However, when GFP-tagged PQL proteins were transiently overexpressed in tobacco leaf cells, the proteins appeared to localize to intracellular membrane structures. Based on q-RT-PCR, the levels of mRNA of AtPQL1a, AtPQL1b and AtPQL1c is higher in salt stressed plants compared to control plants in the shoot tissue, while the mRNA levels in the root tissue did not change in response to stress. Salt stress responses of lines with altered expression of AtPQL1a, AtPQL1b and AtPQL1c were examined using RGB and chlorophyll fluorescence imaging of plants growing in soil in a controlled environment chamber. Decreases in the levels of expression of AtPQL1a, AtPQL1b and AtPQL1c resulted in larger rosettes, when measured seven days after salt stress imposition. Interestingly, overexpression of AtPQL1a also resulted in plants having larger rosettes in salt stress conditions. Differences between the mutants and the wild-type plants were not observed at earlier stages, suggesting that PQLs might be involved in long-term responses to salt stress. These results contribute towards a better understanding of the role of PQLs in salinity tolerance and provide new targets for crop improvement.

Monitoring, tracking, and analyzing the dynamic growth of a living organism is essential to understanding its response to changes in its surrounding environment. Imaging tools to study these dynamics at spatial and temporal scales with optimal resolution rely on high-performance instrumentations. These systems are generally costly, stationary, and not flexible. In addition, performing non-destructive high-throughput phenotyping to extract roots' structural and morphological features remains challenging. We developed the MultipleXLab: a modular, mobile, and cost-effective robotic root imager to tackle these limitations. Among its advantages associated with a large field-of-view, integrated programmable plant-growth lighting, and high magnification with a high resolving power, the system is useful for a wide range of biological applications. We have also created the MultipleXLab Advanced; this configuration turns the system into a mobile environmental chamber by also featuring temperature control and automated irrigation. Another system we developed was the MultipleXLab Advanced Fluorescence to allow fluorescence imaging with a resolution that competes with a fluorescence binocular or even a fluorescence microscope. Furthermore, we have implemented various technologies and techniques to facilitate 3D imaging and quantification, ranging from X-ray micro-Computed Tomography to 3D segmentation of tissues, cells, and cellular compartments within the cell imaged using Confocal Laser Scanning Microscopy. For future research, we have conceptualized an upscaled system named MultipleXLabXL. This larger system will allow tracking, monitoring, and quantifying root growth of a much higher number of seedlings for more extended periods.

No description available.

Crop yields are expected to face more threatening circumstances due to ongoing climatic and environmental change. The continued sustainability of crop production will depend on genetic capacity of crops to adapt to increased biotic and abiotic barriers induced by climate change. Historically, shoot-based traits were breeding targets for overcoming yield gaps between developed and undeveloped nations. However, the rate of genetic gain has stabilized with conventional breeding targets for indirect yield improvement. As the availability of mineral fertilizers is steadily declining and the occurrence of low-fertility soils has increased, reoccurring yield disparities worldwide are propelling us to evaluate new breeding targets. There is potential for plant breeders to shift their focus to the root system architecture (RSA) as a new target for indirect selection, enabled by the phenotypic plasticity of winter wheat (Triticum sp.), one of the main staple agronomic crops. Our current limited understanding of the dynamic nature of the root system architecture is due to the difficulties associated with in situ phenotyping and characterization of anatomical traits. The objectives of this thesis were to 1) review advancements in root phenotyping methodologies and past, present, and future predictions; 2) evaluate differences in root biomass accumulation and remobilization among 22 Virginia Tech-developed elite germplasm; 3) evaluate potential genetic variability for root biomass accumulation across breeding lines. Minimal genetic variation was observed for root biomass accumulation through time. Soil coring proved not to be a very effective method for capturing genetic variability of root biomass accumulation from a soil depth of 10 cm. However, a low genetic signal was also observed for shoot biomass, even though the entire field plot for each genotype was sampled. Yet, a considerably higher genetic signal was observed for plant height. These results suggest that both root and shoot biomass are complex, polygenic traits that require significantly more attention to evaluate genetic differences. / Master of Science / Climate change induces numerous abiotic and biotic barriers to our global cropping systems. Mineral fertilizer reserves are expected to deplete within the next 80 years while our agricultural lands continue losing fertility. This translates into increased yield discrepancies among the most prominent staple agronomic crops. Historically, crop improvement has been performed through indirect selection upon shoot-based traits for yield improvement. However, the capacity of genetic gain from these conventional selection criteria is projected to stabilize. Therefore, it would be beneficial for future global crop production if the initiative was taken to identify a new breeding target that can ensure climate resiliency in staple crops, such as winter wheat (Triticum). Root system architecture (RSA) is defined as the spatial distribution of embryonic and post-embryonic roots throughout a growth medium. This has the potential to become a new breeding target. However, there are numerous difficulties to overcome when evaluating roots in situ. In addition, there is no standardized root phenotyping method that can be implemented nationwide due to the variability in phenotypic response in various growing environments. The objectives of this thesis are to 1) reveal the advancements in root phenotyping and its legitimacy for standardization, 2) explore the genetic architecture of root system architecture, and 3) evaluate the genetic variability of root biomass accumulation for climate resiliency. Minimal genetic variation was observed for root biomass accumulation through time. Soil coring proved not to be a very effective method for capturing genetic variability of root biomass accumulation from a soil depth of 10 cm. However, a low genetic signal was also observed for shoot biomass, even though the entire field plot for each genotype was sampled. Yet, a considerably higher genetic signal was observed for plant height. These results suggest that both root and shoot biomass are complex, polygenic traits that require significantly more attention to evaluate genetic differences.

Shallow foundations rested on Leda clay that are widely distributed in Eastern Canada exhibit shrinkage characteristics and are prone to differential settlements. Due to this reason, significant repairs are necessary to the foundations and basements of residential structures constructed in Leda clay deposits. Differential settlements are commonly attributed to the changes in the natural water content of soils associated with water infiltration, evaporation or plant transpiration (i.e., tree-roots-suction). Various research studies have been undertaken to estimate the possible settlements of shallow foundations associated with the water infiltration or evaporation. Several thumb rules have been proposed through research studies, providing recommendations with respect to the distance at which trees must be planted as a function of their heights at maturity such that differential settlements can be avoided. However, limited studies have been carried out to estimate or model the settlements of shallow foundations taking into account the influence of tree-roots-suction. In the present research program, a comprehensive experimental study regarding the deformation characteristics of a sandy loam soil from Ottawa due to tree-root-suction is undertaken, using specially designed equipment. The study has been undertaken using a sandy loam soil so that the testing program can be conducted in a shorter period of time. An artificial rooting system (ARS) was designed and placed in a specially designed tank at the University of Ottawa to simulate tree-roots-suction and measure soil surface settlements associated with a decrease in natural water content (or increase in soil suction) using particle image velocimetry (PIV) technique. The ARS consists of an artificial root, suction generator, matric suction and volumetric water content monitoring devices. The variation of matric suction and volumetric water content are monitored at various depths using the instrumentation of the ARS. Based on the results of the experimental studies, a methodology is proposed to model the settlement behaviour of sandy loam soils due to suction from ARS, using commercial finite element software, SEEP/W and SIGMA/W (i.e. software package of GeoStudio 2007). The study offers a reasonably good comparison between the measured surface settlements and those estimated using the finite element modelling analysis. The modelling methodology presented in this thesis is promising and may be extended for estimating the settlement behaviour associated with the tree roots suction of Leda clay deposits and to other soils.

No description available.

Root system development in the early phases of plant ontogeny Seed germination and subsequential developement of the root system is a critical stage of life of a newly rising plant. The plant must recognise and suitably and quickly find an answer to the environmental conditions in which it finds itself. However, the way in which the root system develops and its final architecture depends not only on the environmental conditions but also on the plant itself. In addition, responses to different conditions may vary among different plant species. This work examines the developement of a root system in the first four weeks of a plant's life. It observes the dependence on the amount of available nutrients in the substrate and on the amount of available nutrients the seed is given by the mother plant. It also briefly touches on the relations between seed germination, seed size and the amount of available nutrients. No differences relating to the amount of available nutrients were found in seed germination. However, differences in germination speeds were found between plant species. Plant biomass increases with the increasing amount of available nutrients in the substrate. This increase is relatively greater for plant species with a small seed size. Plant species with a big seed size invest relatively more...

Dentre as pragas encontradas em pastagens as cigarrinhas ocupam lugar de destaque visto aos grandes prejuízos econômicos causados. No entanto, a falta de estudos que quantifiquem respostas de plantas forrageiras ao ataque do inseto dificulta a compreensão da magnitude dos danos, impossibilitando a definição de estratégias de controle. O objetivo deste experimento foi caracterizar e quantificar respostas de Brachiaria brizantha cv. Marandu sob níveis de infestações de cigarrinhas adultas do gênero Mahanarva sp. (Hemiptera: Cercopidae). O ensaio foi realizado em casa de vegetação na cidade de Piracicaba SP e seus tratamentos corresponderam a quatro níveis de infestações de cigarrinhas (5, 10, 20 e 40 insetos adultos vaso- 1) mais o controle (sem cigarrinhas), distribuídos nas unidades experimentais (vasos) segundo delineamento inteiramente casualizado. O estudo compreendeu período de infestação pelo inseto e de rebrota das plantas, sendo avaliadas as seguintes variáveis-resposta: acúmulo e composição morfológica da forragem, parâmetros bromatológicos (fósforo (P), potássio (K), cálcio (Ca), magnésio (Mg), enxofre (S), proteína bruta (PB) e fibra em detergente neutro (FDN)), massa de raiz, teor de reservas orgânicas em órgãos de reserva, características morfogênicas e estruturais. A elevação dos níveis de infestação proporcionou redução no acúmulo de forragem com resultados ajustando-se a modelo quadrático de regressão. A proporção de folhas, hastes e material morto também foram afetadas pelos insetos. De maneira geral, a concentração dos parâmetros bromatológicos foi elevada com aumento dos níveis de infestação, PB e S responderam linearmente, e P e Ca ajustaram-se a modelo quadrático de regressão. O número de perfilhos vivos aumentou com a elevação dos níveis de infestação de maneira quadrática. A massa do resíduo e raízes, assim como a concentração de carboidratos não estruturais nesses órgãos de acúmulo, sofreram influência apenas do período de rebrota. A concentração de nitrogênio total foi influenciada pela interação entre níveis de infestação e período de rebrota tanto na fração resíduo como nas raízes. Dentre as características morfogênicas, a taxa de alongamento e de senescência de folhas foram influenciadas com resultados ajuntando-se a modelo quadrático e linear de regressão, respectivamente. Já entre as estruturais o comprimento final da folha e comprimento médio do colmo responderam de maneira linear e quadrática respectivamente. / Among the pests found in pastures spittlebugs have a prominent place due to large economic losses. However, the lack of studies to quantify forage plants responses to insect attack difficult to understand the magnitude of the damage, preventing the definition of control strategies. The objective of this experiment was to characterize and quantify responses of Brachiaria brizantha cv. Marandu under infestation levels of adult spittlebugs of the genus Mahanarva sp. (Hemiptera: Cercopidae). The experiment was carried out in a greenhouse, at Piracicaba SP and their treatments corresponded to four spittlebugs infestation levels (5, 10, 20 and 40 adults pot-1) plus the control (no spittlebugs), distributed in the experimental units (pots) according to a completely randomized design. The study included period of infestation by insects and regrowth of plants and evaluated the following response variables: forage accumulation and morphological composition, bromatological parameters (phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), sulfur (S), crude protein (CP) and neutral detergent fiber (NDF)), root mass, organic reserves content in reserve organs, morphogenetic and structural characteristics. Increased infestation levels provided reduction in forage accumulation with results adjusted to the quadratic regression model. The proportion of leaves, stems and dead material were also affected by the insects. In general, the concentration of bromatological parameters was elevated with increasing infestation levels, CP and S responded linearly, and P and Ca were adjusted to a quadratic regression model. The number of live tillers increased with increasing infestation levels in quadratic manner. The residue and roots mass, as well as the nonstructural carbohydrates concentration in accumulation organs, was influenced only during the regrowth period. The total nitrogen concentration was influenced by the interaction between infestation levels and regrowth period both in the residue fraction as in roots. Among morphogenetic characteristics, the elongation and leaf senescence rates were affected with results adjusted to linear and quadratic regression model, respectively. Among the structural, the final leaf length and stem length responded linearly and quadratically respectively.