Orientador: Rogério Peres Soratto / Banca: Roberto Lyra Villas Boas / Banca: Jose Magno Queiroz Luz / Resumo: A cultura da batata tem grande importância para o Brasil e para o Estado de São Paulo. Porém, apesar de sua importância, falta maiores informações sobre a fisiologia e nutrição mineral desta cultura, limitando a obtenção de elevadas produtividades, com alta qualidade e baixo custo de produção, já que as peculiaridades de cada cultivar podem fazer grande diferença no manejo. Além disso, as doses de fertilizantes normalmente utilizadas na cultura da batata são elevadas, o que gera grande impacto no custo de produção e riscos ambientais. Assim, para obtenção da máxima eficiência produtiva, faz-se necessário o conhecimento do desenvolvimento da planta e da absorção e acumulação de nutrientes nas diferentes fases de desenvolvimento. O objetivo deste trabalho foi avaliar o crescimento, acúmulo de nutrientes durante o ciclo, produtividade de tubérculos e exportação de nutrientes em cinco cultivares de batata. O delineamento experimental utilizado foi o de blocos casualizados, em esquema de parcela subdividida, com quatro repetições. As parcelas foram constituídas pelas cultivares (Ágata, Asterix, Atlantic, Markies e Mondial) e as subparcelas por épocas de coletas de plantas, que foram realizadas a cada 7 dias após a emergência até a colheita final. Cada parcela foi constituída por 10 linhas de 10 m de comprimento. Todas as cultivares tiveram crescimento lento até o início da fase de enchimento de tubérculos. Desta época até o final do ciclo ocorreu o desenvolvimento dos tubérculos, com a máxima taxa de acúmulo de MS concentrando-se no início dessa fase. A cultivar Mondial foi mais tardia em acumular MS, apresentando as maiores taxas de crescimento na fase final do ciclo.As cultivares Ágata, Atlantic e Markies apresentam crescimento semelhante durante todo o ciclo, porém... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: The potato crop has great economical importance for Brazil and São Paulo State. However, despite its importance, it lacks more information about physiology and mineral nutrition of this crop, limiting to obtain high yield, high quality and low production cost, since the peculiarities of each cultivar can make difference in management. Furthermore, the fertilizers rates commonly used in potato crop are high, which has a strong impact on production costs and environmental risks. To get the maximum production efficiency, it is necessary to understand the development of the plant, uptake and accumulation of nutrients in different stages of the plant development. The objective of this study was to evaluate growth, nutrient accumulation, tubers yield and the nutrient exportation in five potato cultivars. The experimental design was the completely randomized block in split-plot with four replications. The plots treatments consisted of potato cultivars (Ágata, Asterix, Atlantic, Markies and Mondial) and subplots were established by harvest time of plants, were carried out every 7 day after emergence to last harvest. Each plot consisted of 10 lines of 10 m in length. All cultivars showed slow growth until the beginning of the tubers bulking stage. Since this time until the end of the cycle, occurred the tubers development, with maximum dry matter accumulation rate focusing in this initial stage. Mondial cultivar took longer time to accumulate dry matter, presenting the highest growth rates in the final stage of the cycle. Ágata, Atlantic... (Complete abstract click electronic access below) / Mestre

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Masters of Science / Bacterial endophytes are able to improve the growth of their hosts through a number of different mechanisms such as nutrient uptake regulation, plant hormone production and regulation, siderophore production and phosphate solubilisation. They have also been shown to be able to provide protection to plants against various abiotic stressors, through various means such as oxidative stress protection. The purpose of this study was therefore to isolate endophytic bacteria from the stems of different weeds, to characterize their ability to use some of the most important growth promoting mechanisms including the ability to produce IAA, siderophores and ACC deaminase, what effect they had on the nutrient uptake in their hosts and to determine to what extent they could promote growth in the roots, stems and leaves of Brassica napus plants. In addition to this the endophytes were tested to see to what extent they could protect Brassica napus from the negative effects of vanadium stress and how this affected the plant physiologically in terms of morphology, overall biomass, the plants nutrient profile, lipid peroxidation and levels of cell death. The effect of vanadium stress on the oxidative state of Brassica napus was also monitored by determining the levels of stress induced reactive oxygen species (ROS) and the corresponding antioxidants that are responsible for regulating these reactive oxygen species. Six different endophytes (P1, P2, P3, P4, P5, P6) were isolated from different weed samples. Each endophyte was found to be able to significantly improve germination and growth in their host plant. Each isolate was able to improve the uptake of certain macronutrients and micronutrients in their respective hosts, while all of the isolates were shown to be capable of producing siderophores and ACC deaminase. One isolate had high levels of IAA production, with the remaining isolates producing small amounts of IAA. All isolates were also unable to solubilize phosphate. The five best performing endophytes (P1, P2, P3, P5, P6) in the preliminary growth trials were used in the follow up vanadium stressed growth trials, with endophyte P4 being left out of the remaining experiments. All of the endophytes showed improvements in growth promotion in comparison to the control, with endophyte treated plants showing both increased growth and biomass in both the non-stressed and vanadium stressed treatments of the vanadium stressed growth trial; however, the leaves of the vanadium stressed plants were significantly smaller than their non-stressed counterparts. When looking at the oxidative state it was found that vanadium stress caused a significant increase in the development of O2 -, H2O2 and •OH in the control and in addition to this it was shown that treatment with endophytes was able to cause a significant decrease in the levels of stress induced H2O2 and •OH in all of the treatments and O2 - for plants treated with endophyte P5. The noted change in the oxidative state of endophyte treated plants was attributed to an increase in the antioxidant activity of these plants, as it was found that endophyte treated plants showed a combination of increased activity for Superoxide dismutase, catalase and ascorbate peroxidase. This study has shown that endophytic bacteria from plant stems can be used to improve crop growth and yield, while simultaneously producing more nutrient dense crops from the same amount of land. It has also determined that endophytes P1, P2, P3, P5 and P6 are able to successfully provide protection to crop plants from the harmful effects of exposure to vanadium stress. This has great potential for improving food security locally and around the world, by allowing those who cannot gain access to large amounts of food to take in more nutrients from the same amount of food. Furthermore, it also presents the opportunity to use endophyte treatments to grow crops on land that has been previously contaminated with certain heavy metals. / 2023-12-01

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Reindeer appear to have strong positive effects on plant productivity and nutrient cycling in strongly nutrient-limited ecosystems. While the direct effects of grazing on vegetation composition have been intensively studied, much less is known about the indirect effect of grazing on plant-soil interactions. This thesis investigated the indirect effects of ungulate grazing on arctic plant communities via soil nutrient availability and plant nutrient uptake. At high density, the deposition of dung alone increased plant productivity both in nutrient rich and nutrient poor tundra habitats without causing major changes in soil possesses. Plant community responses to dung addition was slow, with a delay of at least some years. By contrast, a 15N-urea tracer study revealed that nutrients from reindeer urine could be rapidly incorporated into arctic plant tissues. Soil and microbial N pools only sequestered small proportions of the tracer. This thesis therefore suggests a strong effect of dung and urine on plant productivity by directly providing nutrient-rich resources, rather than by stimulating soil microbial activities, N mineralization and ultimately increasing soil nutrient availability. Further, defoliation alone did not induce compensatory growth, but resulted in plants with higher nutrient contents. This grazing-induced increase in plant quality could drive the high N cycling in arctic secondary grasslands by providing litter of a better quality to the belowground system and thus increase organic matter decomposition and enhance soil nutrient availability. Finally, a 15N natural abundance study revealed that intense reindeer grazing influences how plants are taking up their nutrients and thus decreased plant N partitioning among coexisting plant species. Taken together these results demonstrate the central role of dung and urine and grazing-induced changes in plant quality for plant productivity. Soil nutrient concentrations alone do not reveal nutrient availability for plants since reindeer have a strong influence on how plants are taking up their nutrients. This thesis highlights that both direct and indirect effects of reindeer grazing are strong determinants of tundra ecosystem functioning. Therefore, their complex influence on the aboveground and belowground linkages should be integrated in future work on tundra ecosystem N dynamic.

Arbuscular mycorrhizal (AM) fungi are root and soil inhabiting symbionts with higher plants. The fungi are especially nutrient-function efficient in nutrient deficient soils. There have been innumerable studies of AM fungal facilitation of plant nutrient uptake in controlled environments. Comparatively little similar investigation has been undertaken in natural soils, including investigation of taxon specific nutrient-function efficiency in the phylum. Plant diversity and frequency, soil chemistry statuses, and AM spore diversity and abundance were sampled in an interrupted-belt transect in an aggrading dune sytem on west-coast India, followed by foredunes and transect nutrient amendment experiments in selected plant species. The transect extends 175 m inland from mean high-water mark (MH-WM). Examination showed nutrients were consistently deficient. A plant zonation pattern and increasing frequency over the transect were indicated, as well as decreasing pH and increasing organic matter (OM)-amendment AM species diversity gradients. Plant zonation does not correlate with soil chemistry. There was a distinct soil transition at the 175 m point and evidence of further system partition between foredune and behind-foredune regions. Plant and AM demographies bore no resemblance suggesting neither is driven by the other. Four AM genera were recovered, Acaulospora, Gigaspora and Scutellospora in high abundance, Glomus in comparatively low abundance. The two co-dominant species, A. spinosa and Gi. margarita, displayed divergent strategies in OM amendment. Certain AM taxa may be functionally associated with particular soil nutrients. There was no evidence of taxon-specific nutrient-function efficiency.

<p>Ecohydrological models are extensively used to evaluate land use, land management and climate change impacts on hydrology and in-stream water quality conditions. The scale at which these models operate influences the complexity of processes incorporated within the models. For instance, a large scale hydrological model such as Soil and Water Assessment Tool (SWAT) that runs on a daily scale may ignore the sub-daily scale in-stream processes. The key processes affecting in-stream solute transport such as advection, dispersion and transient storage (dead zone) exchange can have considerable effect on the predicted stream solute concentrations, especially for localized studies. To represent realistic field conditions, it is therefore required to modify the in-stream water quality algorithms of SWAT by including these additional processes. Existing reach-scale solute transport models like OTIS (One-dimensional Transport with Inflow and Storage) considers these processes but excludes the actual biochemical reactions occurring in the stream and models nutrient uptake using an empirical first-order decay equation. Alternatively, comprehensive stream water quality models like QUAL2E (The Enhanced Stream Water Quality Model) incorporates actual biochemical reactions but neglects the transient storage exchange component which is crucial is predicting the peak and timing of solute concentrations. In this study, these two popular models (OTIS and QUAL2E) are merged to integrate all essential solute transport processes into a single in-stream water quality model known as ‘Enhanced OTIS model’. A generalized model with an improved graphical user interface was developed on MATLAB platform that performed reasonably well for both experimental data and previously published data (R²=0.76). To incorporate this model into large-scale hydrological models, it was necessary to find an alternative to estimate transient storage parameters, which are otherwise derived through calibration using experimental tracer tests. Through a meta-analysis approach, simple regression models were therefore developed for dispersion coefficient (D), storage zone area (A_s) and storage exchange coefficient (α) by relating them to easily obtainable hydraulic characteristics such as discharge, velocity, flow width and flow depth. For experimental data from two study sites, breakthrough curves and storage potential of conservative tracers were predicted with good accuracy (R²>0.5) by using the new regression equations. These equations were hence recommended as a tool for obtaining preliminary and approximate estimates of D, A_s and α when reach-specific calibration is unfeasible. </p> <p> </p> <p>The existing water quality module in SWAT was replaced with the newly developed ‘Enhanced OTIS model’ along with the regression equations for storage parameters. Water quality predictions using the modified SWAT model (Mir-SWAT) for a study catchment in Germany showed that the improvements in process representation yields better results for dissolved oxygen (DO), phosphate and Chlorophyll-a. While the existing model simulated extreme low values of DO, Mir-SWAT improved these values with a 0.11 increase in R² value between modeled and measured values. No major improvement was observed for nitrate loads but modeled phosphate peak loads were reduced to be much closer to measured values with Mir-SWAT model. A qualitative analysis on Chl-<i>a</i> concentrations also indicated that average and maximum monthly Chl-<i>a</i> values were better predicted with Mir-SWAT when compared to SWAT model, especially for winter months. The newly developed in-stream water quality model is expected to act as a stand alone model or coupled with larger models to improve the representation of solute transport processes and nutrient uptake in these models. The improvements made to SWAT model will increase the model confidence and widen its extent of applicability to short-term and localized studies that require understanding of fine-scale solute transport dynamics. </p>

Climate change and introduced species are among the top five threats to freshwater systems face. Tropical regions are considered to be especially sensitive to the effects of climate change, while island systems are more susceptible to species introductions. Climate-driven changes in rainfall are predicted to decrease streamflow and increase flash flooding in many tropical streams. In addition, guppies (Poecilia reticulata), an invasive fish, have been introduced to many tropical freshwater ecosystems, either intentionally for mosquito population control, or accidentally because of the aquarium trade. This dissertation examines the effects of climate-driven change in rainfall and introduced guppies on stream structure (resource and invertebrate biomass and composition) and function (nutrient recycling) in Trinidad and Hawaii. In the first data chapter we used a time series to examine how nutrient recycling of guppies changes in the first 6 years after introduction to a new habitat and to examine drivers of these changes. We found that when guppy populations establish in a new environment, they show considerable variation in nutrient recycling through time. This resulted from changes in guppy density in the first two years of introductions, and changes in individual excretion in subsequent stages. In the following chapter we utilized a rainfall gradient that mimics forecasted, climate-driven changes in precipitation and resulting changes in streamflow to examine the effects of climate change on stream food resources and macroinvertebrates. We found that the drying of streams across the gradient was associated with a decrease in resource quality and a 35-fold decline in macroinvertebrate biomass. Invertebrate composition also switched to taxa with faster turnover rates. In the third data chapter we used this same space-for-time substitution approach to determine if climate-driven changes in stream structure also affected stream function. We showed that population nutrient recycling rates declined at the drier end of our rainfall gradient as a result of drops in population densities. We also found that under the current climate scenario, community excretion supplied up to 70% of the nutrient demand, which was ten-fold lower with projected climate changes in streamflow. Lastly, since freshwater ecosystems often face multiple human impacts, including climate change and invasive species, we wanted to understand how climate-driven changes in flow might alter the impact of introduced guppies on stream ecosystems. We selected several streams with guppies and several without guppies along the Hawaii rainfall gradient to examine if the effect of guppies changed with differences in streamflow. We found that the two stressors had synergistic effects on macroinvertebrate biomass and nutrient recycling rates. We concluded that climate change appeared to enhance effects of guppies, through direct and indirect effects. Overall, this dissertation shows that both climate change and species invasion can affect stream ecosystems at multiple levels of organization. This dissertation demonstrates that the effects of anthropogenic stressors are not static through time, and emphasizes the need and utility of using several methodological approaches when measuring the temporal effects of stressors. We also underline the significance of assessing multiple stressor interactions, as more than one stressor often impacts ecosystems. / Graduate / 2019-09-01

Diss. (sammanfattning) Umeå : Sveriges lantbruksuniv. / Härtill 4 uppsatser.

Diss. (sammanfattning) Ultuna : Sveriges lantbruksuniv., 2006. / Härtill 4 uppsatser.