Nitrogen (N) is an essential plant nutrient, widely applied as N-fertilizer to improve yields of agriculturally important crops. An alternative to fertilizer use could be the exploitation of plant growth-promoting bacteria, capable of enhancing growth and yield of many plant species. Azospirillum and Gluconacetobacter are root colonizing, free-living, N2-fixing bacteria (diazotrophs) with the potential to transfer fixed N to associated plants. The purpose of this study was to evaluate the agronomic efficiency of two diazotrophs, Azospirillum lipoferum and Gluconacetobacter azotocaptans, inoculated onto wheat. Physiological parameters and yield components were evaluated. The objectives of this study were to: 1) determine the survival of each diazotroph species on wheat seeds over time; 2) determine the survival of A. lipoferum and G. azotocaptans inoculated on wheat seed treated with a fungicide seed treatment, Dividend® XL RTA®; 3) determine if inoculation of wheat with the diazotrophs under controlled conditions causes an increase in dry matter, N2-fixation and N uptake; 4) determine if fertilizer N applied at three levels influences atmospheric N2-fixation by A. lipoferum or G. azotocaptans; 5) determine if inoculation of wheat with A. lipoferum or G. azotocaptans under field conditions causes any increase in dry matter, N2-fixation and N uptake; 6) determine if N-fertilization levels under field conditions influenced N2-fixation by A. lipoferum or G. azotocaptans. In order to meet these objectives lab, growth chamber, and field studies were completed. Laboratory investigations revealed that the decline in recovery of colony forming units (CFU) of G. azotocaptans was not significantly different (P<0.05) for any seed treatment. There was a general decrease in CFU over time regardless of seed treatment. Analysis of the recovered CFU of A. lipoferum over time showed that there was a significant difference (P<0.05) between both the non-sterilized seed and the Dividend® XL RTA® treated seed when compared sterilized seed. Recovery of CFU on sterilized seed declined at a more rapid rate compared to the other two seed treatments. Gluconacetobacter azotocaptans and A. lipoferum were not negatively influenced by the Dividend® XL RTA® seed treatment. Also, both diazotrophs were able to compete with other microorganisms that may have been on the seed coat of unsterilized seeds. Azospirillum lipoferum and G. azotocaptans were able to fix atmospheric N, but, there were no significant (P<0.05) differences between the diazotroph species. Additions of fertilizer N enhanced N2-fixation, in both the growth chamber and field studies. As the amount of fertilizer N increased, so did the %Ndfa and N uptake. In the growth chamber study, inoculated wheat, and fertilized with 12.2 and 24.5 µg N g-1 had the highest %Ndfa of 25.5%, and wheat fertilized with 24 µg N g-1 had the highest N uptake (1.3 g pot-1) at maturity. In the field study, inoculated wheat fertilized with of 80 kg N ha-1 had significantly higher (P<0.05) %Ndfa (10.5%) compared to wheat grown with the other fertilizer levels, which also corresponded to the highest N uptake in wheat plants (47 kg ha-1). The diazotrophs also affected the partitioning of N in the wheat plants differently. Wheat inoculated with A. lipoferum had significantly higher (P<0.05) amounts of N accumulated in heads of plants, and wheat inoculated with G. azotocaptans had significantly higher (P<0.05) amounts of N accumulated in stems of plants. However, this trend was not evident in the field study.

Vegetable grafting confers soil-borne disease resistance through the use of selected rootstocks. Additional costs associated with grafted vegetable seedling propagation limit grower access to this technology. The use of low temperature storage in grafted seedling production reduces labor costs and allows propagators to meet the seasonal and narrow-window demand of growers. For the first part of the experiment 22 genotypes of Solanaceae or Cucurbitaceae seedlings were evaluated in low temperature storage conditions (5 or 12°C). Seedling performance was better in 12°C storage than in 5°C storage. For the second part of the experiment watermelon, the most low-temperature sensitive species found in our first study, was grafted onto two different commercial rootstocks or on to other watermelon seedlings and stored at 12°C for two and four weeks. Both 'Strong Tosa' and 'Emphasis' rootstocks conferred chilling tolerance during storage to watermelon scions, allowing storage of grafted plants for two weeks.

Orientador: Prof. Dr. Luciano Soares da Cruz / Dissertação (mestrado) - Universidade Federal do ABC, Programa de Pós-Graduação em Biotecnociência, 2017. / O desenvolvimento das plantas depende fortemente das condições ambientais em que estes organismos se encontram. Assim, as plantas desenvolveram mecanismos de adaptação e defesa que permitem seu crescimento e proliferação, mesmo sem a habilidade de se deslocar. Devido a este altamente sofisticado sistema de defesa e adaptação das plantas, as suas características (fenotípicas e bioquímicas) são fortemente influenciadas pelo ambiente no qual a planta se desenvolve. Para garantir a reprodutibilidade dos experimentos em biologia de plantas é fundamental a mensuração e, se possível, o controle adequado dos parâmetros ambientais essenciais ao crescimento das plantas. A não observação disso pode incorrer na não reprodutibilidade do experimento e, consequentemente, obtenção de conclusões incorretas ou distorcidas dos resultados experimentais. Neste trabalho analisamos a manipulação do espectro luminoso a fim de controlar as características da luz incidente nas plantas. Para isto, foram estudados materiais poliméricos para uso como filtros da luz solar e isolamento dos espécimes do ambiente externo. Dessa forma, analisamos os efeitos destes filtros na qualidade e quantidade de luz e seu uso no redirecionamento das trajetórias metabólicas e propriedades biométricas no ciclo de crescimento das plantas. Além disso, para fins práticos, também verificamos as mudanças nas propriedades físicas destes materiais ao longo do tempo por meio de exposição a processos de degradação acelerada. Dessa forma, verificamos os possíveis efeitos de deterioração nos materiais poliméricos devido a sua exposição ao meio ambiente por longos períodos, o que nos permite garantir o uso das câmaras de crescimento desenvolvidas por um período de tempo adequado, no qual suas características essenciais não sofram danos que poderiam influir nos resultados experimentais esperados. / The development of the plans depends heavily on the environmental conditions in which these organisms are. Thus, plants are developed to adapt and defend maximizing their growth and proliferation, even without the ability to move. Due to this highly sophisticated system of defense and adaptation of the plants, their characteristics (phenotypic and biochemical) are strongly influenced by the environment where plant develops. In order to guarantee the reproducibility of the experiments in plant biology, it is fundamental the measurement and, if it is possible, adequate control of environmental parameters essential to plant growth. Failure to observe this may result in non-reproducibility of the experiment and consequently incorrect or distorted conclusions of the experimental results. In this work, we analyzed the manipulation of the light spectrum in order to control the characteristics of the incident light in the plants. For this, we studied polymeric materials for use as sunlight filters and isolation of the specimens from the external environment. Thus, we analyzed the effects of these filters on the quality and quantity of light and their effects in the redirection of the metabolic trajectories and biometric properties in the plant growth cycle. In addition, for practical purposes, we also monitoring at changes in the physical properties of these materials over time through exposure to accelerated degradation processes. In this way, we verify the possible effects of deterioration in the polymeric materials due to their exposure to the environment for long periods, which allows us to guarantee the use of developed growth chambers for an adequate period of time, in which their essential characteristics do not suffer degradation that could influence incorrectly the experimental results.

The aim of this thesis is modelling of chamber for plant cultivation under defined conditions. First part of the thesis contains theoretical introduction to thermodynamics and humid air problematics. In the next part of thesis, the growth chamber model was designed. Model parameters were obtained during fytotron identification. Chamber control algorithm was designed using the model. The control algorithm was programmed into chamber control unit and its functionality was practically tested.

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Competition between different species (interspecific competition) is an important factor to consider when estimating population trends, geographic distributions, and management options of species. Many historically common vascular plant species found in agricultural environments have been negatively affected by changes in community composition and in turn, changes in competition pressures. Even so, the relative importance of plant competition in an ecological context is still unclear. In this study I examine the competitive ability of the meadow plant cornflower (Centaurea cyanus L.) when grown together with common oat (Avena sativa) and common poppy (Papaver rhoeas), during a seven-week long growth chamber experiment. Seeds were sown in pots in four different setups; 1) C. cyanus control, 2) C. cyanus + P. rhoeas, 3) C. cyanus + A.sativa, 4) All three species. Six different growth parameters were measured (aboveground dry-weight, belowground dry-weight, root length, leaf area, number of leaves and above/belowground dry-weight ratio). I found that growth rates of C. cyanus were significantly inhibited according to all six growth parameters when C. cyanus competed solely with A. sativa. Competition from P. rhoeas had an insignificant effect on C. cyanus growth in five out of six growth parameters. Finally, I discuss the possibility that historically common meadow plants have declined in abundance in part because of weak competitive abilities, and that rare vascular plant species are negatively affected by growing in proximity with cereal crops.

Competition between plant individuals and how plants alter soil properties are key processes which drive changes in plant communities over time. Estimating the relative importance of these processes and how they affect plant growth in different ecological contexts and communities is an active area of research. Furthermore, interdependencies between the two processes have been suggested to occur in many cases, but research in this area is also lacking. In this study, soil conditioned by common yarrow (Achillea millefolium) was collected from field plots and was then used in a growth chamber competition experiment, which controlled for plant-soil feedbacks. Measured soil properties such as soil pH, soil nitrogen, and soil texture were primarily used as background data in the experiment. Field parameters such as light availability, plant density, and grass to forbs ratio were used to predict optimal A. millefolium habitat in relation to other vascular plant species. The results indicate that A. millefolium was a weaker competitor than cornflower (Centaurea cyanus), while a positive plant-soil feedback effect was observed by A. millefolium grown in field soil. Intraspecific competition had a strong negative effect on A. millefolium growth when grown in non-conditioned soil, but not when grown in A. millefolium conditioned soil. Finally, competition and plant-soil feedbacks appeared to be additively affecting A. millefolium growth, meaning the plant-soil feedback effect did not have a disproportionate effect on competitive outcomes, or vice versa. The findings of this study can be of interest to conservationists or farmers who wish to predict how plant communities respond to plant competition and plant-soil feedbacks as processes.

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