Digital Commons Network^™

Determining The Factors That Control Respiration And Carbon Use Efficiency In Crop Plants, Jonathan M. Frantz

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

In the literature on plant respiration, there are two viewpoints concerning the source of respiratory control: supply (photosynthate availability) or demand (temperature dependent) limitations. While different studies indicate the primary dependency for respiration is either the supply or demand side, the two paradigms cannot both be true. The relative importance of each paradigm may depend on a number of factors including period of time during which respiration is measured, phase of plant development, environmental conditions, and species.

Studies were performed using continuous CO₂ gas-exchange instrumentation to monitor short- and long-term changes in whole canopies of lettuce, tomato, soybean, and …

Physiological And Biochemical Aspects Of Agrobacterium-Wheat (Triticum Aestivum L.) Interactions, David L. Parrott Jr.

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

Agrobacterium tumefaciens and A. rhizogenes are the causal agents of gall or hairy root disease, but normally the bacteria do not cause disease in wheat. However, both bacteria grew without inhibition when exposed to intact or wounded wheat roots or embryos, and they colonized wheat root surfaces to levels similar to dicotyledonous plants. A. tumefaciens and A. rhizogenes induced 23% cell death after a 1-h exposure to wheat embryo cells grown in 7.4 mM O₂, while the extent of cell death at 2.1 mM O₂ was 8%. Contact with A. tumefaciens or A. rhizogenes caused cultured wheat …

Use Of Ground-Based Canopy Reflectance To Determine Radiation Capture, Nitrogen And Water Status, And Final Yield In Wheat, Glen L. Ritchie

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

Ground-based spectral imaging devices offer an important supplement to satellite imagery. Hand-held, ground-based sensors allow rapid, inexpensive measurements that are not affected by the earth’s atmosphere. They also provide a basis for high altitude spectral indices.

We quantified the spectral reflectance characteristics of hard red spring wheat (Triticum aestivum cv. Westbred 936) in research plots subjected to either nitrogen or water stress in a two year study. Both types of stress reduced ground cover, which was evaluated by digital photography and compared with ten spectral reflectance indices. On plots with a similar soil background, simple indices such as the …

Effect Of Drought, Flooding, And Potassium Stress On The Quantity And Composition Of Root Exudates In Axenic Culture, Amelia Henry

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

Root exudates include important chelating compounds and can change the rhizosphere pH by several units. These changes are essential for nutrient uptake and can also alter solubility of soil contaminants and increase plant uptake. Mild root-zone stress may increase exudation and more severe stress can damage membranes and increase root turnover, all of which increase root-zone carbon. Increased carbon from this rhizodeposition can increase microbial activity, which might help degrade contaminants. We studied the effect of three types of stress on root exudation of crested wheatgrass (Agropyron cristatum): low K⁺, drought, and flooding. These stresses were …