Thesis (M. S.)--Oklahoma State University, 2007. / Vita. Includes bibliographical references.

Thesis (Ph. D.)--Oklahoma State University, 2007. / Vita. Includes bibliographical references.

Thesis (M.S.)--Oklahoma State University, 2008. / Vita. Includes bibliographical references.

Thesis (M.S.)--Oklahoma State University, 2008. / Vita. Includes bibliographical references.

Experiments were carried out using pure cultures of a soil bacterium (B. globiforme) to determine optimum conditions of growth for this organism in 2:4-D culture. The effect of aeration of liquid cultures and the addition of various other substances to the media was recorded. The ability of this organism to grow on other substrates was studied. Assays of phytotoxicity in the culture media were undertaken and the effect of concentration of 2 :4-D on its decomposition studied. Isolations of fresh organisms from garden soil capable of the detoxication of 2:4-D were attempted and these organisms subsequently grown, singly and in mixtures, in 2 :4-D culture In an attempt to produce a breakdown in culture similar to that found in soil. Experiments using a soil perfusion technique and also mixtures of organisms obtained from perfusate enriched to 2:4-D were also carried out. The original isolates became ineffective in 2:4-D decomposition after culture of approximately twelve months and fresh isolations had to be made. These resulted in the eventual isolation from fresh garden soil of a strain of the Actinomycete Nocardia which proved capable of utilising 2:4-D as a carbon source In agar and in aerated liquid culture. Subsequent experiments were carried out using sub-cultures of this organism. The effects of concentration of 2:4-D and of the presence of a soil extract and agar dialysate on detoxication of the culture fluids were recorded. The growth of this organism in unaerated liquid culture on various carbon substrates was studied and the subsequent ability of organisms so cultured to decompose 2:4-D in agar recorded. The decomposition of 2 :4-D in liquid culture was followed using radioactive samples of 2:4-D labelled in either the methylene or carboxyl groups of the side chain. The changes in radioactivity and phytotoxicity were followed chromatographically and measurements of chloride and phenolic material present in the culture media made throughout the detoxication period. Measurements of radioactivity and phenolic materials absorbed in an alkali trap through which air leaving the cultures was passed were also recorded. A possible route for the early stages of breakdown of the 2:4-D molecule by this strain of Nocardia is suggested involving the formation of 2:4-dichlorophenol, o-chlorophenol and phenol.

An investigation was carried out into the effect of 2-4 dichlorophenoxyacetic acid (24D) and other herbicides on soil populations. Experiments were devised to test the hypothesis that the initial lag period in detoxication is a combination of a period of adaptation followed by proliferation. Methods employed were dilution plate counts, variations in conditions of treatment, respiration studies, and the use of a bacteriostat and pre-enrichment of the soil with autotrophic organisms. An active organism, which would decompose 24D when inoculated into an aerated suspension of sterile soil, was isolated from soil enriched to this herbicide. There is a significant correlation between 24D concentration and bacterial numbers in the soil. Applications of this herbicide stimulated the rate of respiration of an enriched soil and of a culture of the isolated active organism. Results indicate complete oxidation of the molecule. The evidence suggests that the organisms responsible occupy sites on the surfaces of the soil crumbs where the anion is adsorbed. These sites are quite distinct from those occupied by the nitrifying and thiosulphate-oxidising autotrophs. Proliferation of organisms begins on the fifth or sixth day of treatment, at which time it is calculated that a slow breakdown of herbicide begins. It was concluded that the organism responsible for the detoxication of 24D in soils undergoes a period of adaptation to the new substrate, lasting five or six days. During the following time, all the sites on the soil crumbs where the 24D anion can be adsorbed are occupied to give a saturated soil. When herbicide is reapplied, rapid breakdown ensues accompanied by a high rate of carbon dioxide evolution and sufficient proliferation to replace those bacteria which have died. It is probable that a similar process occurs when soil is treated with other phenoxyacetic acids.

Studies on the distribution of Mucor ramannianus in coniferous woodland and heathland soils of a podsolic nature resulted in the amassing of a number of isolates. Macro and micro morphological observations on these isolates revealed that they could be placed in five distinct groups, A -E.A study of the growth reactions of the isolates under a number of different cultural conditions showed that they also differed physiologically. The isolates could be placed in the same five groups on physiological grounds, as well as on morphological grounds. A study of the growth factor requirements of the species revealed that some isolates were heterotrophic for thiamin, whilst others were autotrophic or incompletely autotrophic for this vitamin. One isolate required some other growth factor, but its exact requirement was not discovered. Variation within the species was thus shown to occur at morphological, physiological and biochemical levels, the last two being related to the morphology of the isolates. Crossing experiments between isolates of the same and different groups produced negative results, i.e. zygospores were not produced. A spontaneous imitation of an autotrophic isolate resulted in sectors which required thiamin for growth. These mutant sectors were exactly similar in morphology, physiology and biochemistry to the isolates of the heterotrophic group. Thus a connection between two of the groups was discovered. Following the observation of occasional hyphal fusion and anastomosis in this species, the possibility of heterokaryosis being a means of variation within the species was considered. Induced biochemical mutants were obtained by use of X-rays and ultra-violet light. Heterokaryons were produced between certain of these mutants and the spontaneous mutant. Investigations into the distribution of M.ramannianus have revealed that there is a relationship between the type of distribution shown by a particular isolate of the species and the group to which that isolate belongs.

Modifications of the perfusion and cress-assay techniques of Audus were used to study breakdown in soil of 2,4-D and some related compounds. Attempts to produce active bacterial (pure) cultures from the enriched soils proved abortive. Mixed, crude cultures were partially successful though never energetic. A wide range of stimulants failed to induce pure culture activity. Enrichment was transferrable to fresh soil by treating it with perfusate from an active perfuser. The activating principle was thermolabile, probably consisting of adapted bacteria. The technique was used to quickly produce numbers of similar enriched perfusers without the necessity of lengthy adaptation processes. Compounds labile in soil followed the same general course, a characteristic lag phase being followed by a period of rapid breakdown. Further added substrate was usually decomposed with no further lag. Some control of the lag was obtainable by pre-treatment of the soil, or perfusion in mixture, with related compounds. Mixtures of certain phenoxyacetic acids appeared to be synergistic in their inhibition of root growth. 2,4-D adaptation proved very stable, persisting through prolonged perfusion with water, or storage for over a year, of Enriched soil. The optical isomers of the chlorophenoxypropionic acids appear to differ in resistance to attack as well as having different physiological activities. Relative Toxicity to cress and lability in soil appear to be controlled by the same molecular features and a close correlation exists between the two functions. Attachment to substrate ( enzyme? ) in each case is probably through the ?-H and carboxyl groups of the side-chain and the 3- or 5-nuclear positions. The effects of molecular substitution on stability and physiological activity are discussed as also are the possibilities of phenol formation and / or ring fission during breakdown. A possible relationship between the breakdown products and biotin metabolism is also indicated.

<p> Eastern North Dakota has received excessive rainfall events since 1995, and soils are prone to waterlogging. This research evaluated the effects of subsurface tile drainage, raised beds, and iron-chelate (Fe-EDDHA) seed-application on iron-deficiency chlorosis (IDC) incidence in soybean [<i>Glycine max </i> (L.) Merr.], soybean growth, and yield, across six environments during 2013 and 2014. Tile drainage without beds increased soybean yield and reduced IDC by 11%. Beds resulted in more vigorous plants with 9% more biomass and increased soybean yield by 6%. There was no yield advantage to using both tile and raised beds within the same field. The Fe-EDDHA reduced plant population and IDC expression, increased plant biomass, but did not result in a yield increase. Farmers are encouraged to consider utilizing raised beds as a means to mitigate excess water. Additional research is needed to determine the cause of lower established plant density after seed application with Fe-EDDHA.</p><p>

The herbicides Ioxynil, Bromoxynil, NPH 1320. Totril, Dieamba, Tricamba, Trifluralin, Oxadiazon, Legurame, M and B 9057 and M and B 9555 were tested for their effects on the process of nitrification in soil as well as in pure cultures. An improved version of the perfusion apparatus was developed and the perfusion technique was used as the principal experimental method in the soil studies in which the effects of different herbicides on the rates of nitrification in soils previously enriched with nltrifiers and in fresh soils continuously perfused with the herbicides were estimated. These estimates were made use of in the assessment of the degree of toxicities of the herbicides under consideration, on the metabolic rates per cell of nitrifiers and on their degree of proliferation in soil. An attempt was also made to study the possible differential effects of these herbicides on the two main groups of chemoautotrophic soil nitrifiers and the results obtained revealed that the metabolic activities of Nitrosomonas populations in soil were much less sensitive to the lower concentrations of many of the herbicides tested when compared with the sensitivities shown by the Nitrobacter populations, of the same soils, to the toxic effects of the same herbicides. But the rates of metabolic activities of Nitrosomonas populations were found to be the factor limiting the overall rates of the nitrification process in soils treated with the higher concentrations of most of these herbicides. The nitrification experiments carried out with cell suspensions of pure cultures of Nitrosomonas Euronaea and Nitrobacter Winogradski indicated that the herbicides exerted differential effects on the metabolic activities of these two organisms even in artificial media. The only other method used in studying the effects of herbicides on soil nitrification involved the measurement of the rates of oxygen uptake by samples of enriched soil treated with known concentrations of herbicides, making use of the conventional Warburg respirometrie technique. The qualitative effects of most of the herbicides on the activities of nitrifiers, grown in artificial media and in the natural medium of soil, were found to be essentially similar although the concentrations effective in causing these toxicities in pure cultures were much less than the concentrations needed to cause similar levels of toxicities in soil media.