Habilitationsschrift--Bonn. / Includes bibliographical references.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1965. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1964. / Typescript. Vita. Includes bibliographical references (leaves 54-57).

Thesis (M.S.)--University of Wisconsin--Madison, 1983. / Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 149-162).

Call number: LD2668 .T4 1961 F87

Tomato plants (Lycopersicon esculentum Mill.) were grown in a greenhouse in Arizona in order to determine the effect of aeration, flooding, and exogenously applied benzyladenine (BA) on growth and cytokinin production at different growth stages. The structural changes in roots at different soil environments were also studied. Fresh and dry weight of roots and shoots and root exudate were collected at various stages of growth. Results showed that aerated plants significantly outperformed flooded and BA treated plants due to increased root and shoot output. The level of cytokinin in root exudate was higher during the early phase of vegetative growth. At the time of bud formation and anthesis, the level of cytokinin declined. In the vegetative stage, the competition between removed sinks and the rest of the shoot was reduced and, as a result, more cytokinin was believed to come from the roots to the shoots. Besides, additional carbohydrates were available to the roots. Determination of cytokinins in aerated plants showed a significant increase. However, in flooded plants, a smaller amount of cytokinin was detected. This is believed to be due to death of root apices, a major site for cytokinin production. Under experimental conditions, the application of BA to foliage of flooded plants had an adverse effect on growth of roots and shoot of tomato plants. However, a slight increase in cytokinin level was detected. Histological studies showed an increase in air-spaces (aerenchyma) in roots of flooded plants. This acclimation improved survival in inadequately aerated plants that were waterlogged.

The rate at which volatile organic compounds (VOCs) are removed from the vadose zone by forced ventilation may be reduced by slow micro-scale processes such as diffusion through intra-aggregate and pore water and slow reactions at sorption sites located at the soil-water interface. Column experiments using benzene and p-xylene were performed in order to simulate cleanup of VOC's in the vadose zone by forced ventilation. Analytical solutions of the one-dimensional advection-dispersion equation coupled to mass transfer equations were fitted to the data. Parameter estimates were used in order to determine time scales of diffusion through water, desorption from, and sorption to, soil organic matter. Lower limits for the time scales for these processes were calculated to be on the order of minutes. Results indicate that these micro-scale processes reduce the rate of removal on the laboratory scale but may have no effect on the field scale.

Gaseous transport through soil in the presence of soil microorganisms has been investigated. More recently, modeling of gaseous transport in the unsaturated zone has been investigated. However, the problem of mathematical model of oxygen and carbon dioxide transport through soil, as affected by the climatic conditions, the transport of soil water, and the biological activities, has not been studied. The problem of time-dependent diffusion of oxygen and carbon dioxide through plant canopy and soil system, as affected by the infiltration and evaporation of soil water and the rate of consumption of oxygen and production of carbon dioxide by plant leaves and roots and soil microorganisms was studied, using a one-dimensional mathematical model. This model consists of four sets of non-linear partial differential field equations, which describe the time-dependent simultaneous transport of water, heat, oxygen, and carbon dioxide through the soils. Finite difference methods were used to find the approximate solutions for the four sets of non-linear partial differential field equations. The field equations for the transport of water and heat were approximated by using the implicit scheme. The field equations for the transport of oxygen and carbon dioxide were approximated by using the explicit scheme. A computer program was written in Fortran code to conduct the simulations of the mathematical model. Simultaneous transport of water, heat, oxygen, and carbon dioxide through the unsaturated Indio loam soil, through the compacted and the non-compacted soil during infiltration, redistribution, and evaporation of soil water was evaluated. Diffusion of oxygen and carbon dioxide within the canopy and soil system was examined. Several different functions for the root elongation and the root oxygen consumption rates were used. Root elongation rate was chosen to depend on oxygen or carbon dioxide concentrations, in addition to being a function of time. Root oxygen consumption rate was assumed to be a function of root age, in addition to being a function of oxygen or carbon dioxide concentrations. Results illustrate that the behaviors of the simultaneous transport of water, heat, oxygen, and carbon dioxide were well predicted by the model. / Graduation date: 1991

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