The fungus Phoma menthae Strasser causes black lesions and cankers on stems and rhizomes of Mentha piperita L. The purpose of this thesis was to: 1) study the production of polygalacturonase (PG) and macerating enzymes (ME) by P. menthae in vivo and in vitro, 2) study the effects of phenolic compounds on the activity of PG and ME produced by P. menthae in vivo, and in vitro, 3) compare polyphenol oxidase acitvities in healthy and diseased peppermint rhizome tissues. PG activity was measured by both viscosity reduction and reducing groups assays, using sodium polypectate (NaPP) as substrate. Fungal PG was first detected in cultures two days old. PG activity in filtrates was highest in cultures five and 23 days old, as determined by reducing groups assay. PG activity, as determined by viscosity reduction assay, was highest in cultures seven days old and remained the same for 28 more days. Growth (dry wt.) of the fungus was highest after 13 days and then gradually declined. In young cultures (two and three days old) pectin was a better substrate than NaPP for production of PG by P. menthae. In older cultures (five to 13 days old), NaPP was a better substrate than pectin for production of PG. PG activities in both cases were measured by reducing groups assay. The hydrolysis curve of NaPP produced by PG from culture filtrate differed from that producted by diseased rhizomes extract, as determined by viscosity reduction assay. When determined by reducing groups assay, hydrolysis curves of NaPP produced by culture filtrate and diseased rhizomes extract did not differ. Therefore, differences in PG produced in vitro and in vivo were revealed only by the viscosity reduction assay method; the reducing groups assay did not reveal this difference. ME activities were highest in filtrates from cultures ten days old. ME activities were determined by an optical density method, using potato discs as substrate. This method accurately detected differences in potato tissue maceration. Culture filtrate of P. menthae macerated peppermint rhizomes. Young peppermint rhizome sections were more susceptible to maceration than older sections. Colored phenolic compounds, were released from the macerated rhizomes and the amount released was correlated with degree of maceration. Among nine phenolic compounds incubated for 15 hrs with culture filtrate of P. menthae (containing PG and ME), tannic acid, 1,2 naphthoquinone and digallic acid inhibited PG and ME, as determined by viscosity reduction and the action on potato discs, respectively. Inhibition of PG and ME by these phenolics indicates that PG plays an important role in the maceration process. PG activity, as determined by reducing groups assay, was inhibited considerably by tannic acid and activated by phenol, p-benzoquinone, 1,2 napthoquinone, 1,4 naphthoquinone and 2 methyl 1,4 naphthoquinone. When healthy and diseased peppermint rhizomes were homogenized in culture filtrate of P. menthae, PG activity was inhibited, as measured by viscosity reduction. In a similar test, PG was activated by healthy and inhibited by diseased rhizome tissues, as determined by reducing groups assay. Biologically oxidized catechol and polymerized p-benzoquinone inhibited PG activity in culture filtrates, as determined by viscosity reduction assay; they activated PG as determined by reducing groups assay. Both PG and ME reached their highest activities in diseased peppermint rhizomes five days after inoculation with P. menthae. PG was determined by both viscosity reduction and reducing groups assays. Extracts from healthy peppermint rhizomes did not show PG or ME activity. Tannic acid, 1,2 naphthoquinone, p-benzoquinone and digallic acid inhibited PG extracted from inoculated peppermint rhizomes, as determined by both viscosity reduction and reducing groups assays. Among nine phenolic compounds tested on the activity of ME extracted from diseased peppermint rhizomes, only catechol, p-benzoquinone and tannic acid showed strong inhibition, while 1,2 naphthoquinone, 1,4 naphthoquinone, 2 methyl 1,4 napthoquinone, and digallic acid showed a moderate inhibition, as measured by the action on potato discs. The effect of phenolic compounds on PG produced by P. menthae both in vivo and in vitro (as determined by both viscosity reduction and reducing groups assays) suggests that two PG's are being produced. One PG is more active in hydrolyzing NaPP thus releasing large quantities of reducing groups, and the other is more active in hydrolyzing NaPP solutions causing a rapid reduction in their viscosity. Healthy peppermint rhizome tissues had higher activities of polyphenol oxidase than diseased tissues; also, polyphenoi oxidase activities in inoculated peppermint rhizomes decreased as time of incubation increased.

Soil-sulfur in Volcanic-ash derived soils was determined in soil extracts. The sulfur extracted was transformed into sulfate ions and organic matter destroyed by means of a 30% H₂O₂ solution. Sulfate ions were precipitated with a 15% BaCl₂ solution and the precipitate then dissolved in (NH₄)₂ EDTA, and Barium determined by Atomic Absorption Spectrophotometry. Sulfur recovery was ascertained using an internal standard.

A method is described that was used to experimentally determine an intensity correction for gamma-ray attenuation. The correction is determined by using the minute nonlinearity of a semi-log plot of gamma-ray intensity versus the thickness or the product of thickness and density of a material. The experimentally determined correction is expressed in terms of resolving time and varied with both material and counting rate. A correction of 5.0 µsec/count was determined experimentally as the best resolving time to correct the observed counting rates for water content determination. Part of the 5.0 µsec/count correction was evidently due to causes other than resolving time. Mass absorption coefficients of water and soil were 0.08105 and 0.07309 cm²/g, respectively, with no correction and were 0.0871 and 0.0773 cm²/g with a 5.0 µsec/count correction. The difference between gravimetric water content and gamma-ray water content dropped from 3.02% to 0.60% when this correction was used.

The relative merits of several different chemical agents as collecting agents were determined in a lotic system under laboratory conditions at 12 degrees Centigrade. The materials tested were quinaldine, McNeil-JR-7464, and three isomers of cresol. Efficacy and toxicity were tested. In general, the cresols were determined to be too harsh physiologically to warrant further development as fish-collecting agents. MS-222 did not induce surfacing and required high concentrations for total incapacitation. Quinaldine may be useful in collecting fish in small streams with rapid flow, but its physiological effects need elucidation. McNeil-JR-7464 does not induce surfacing, but is effective at low concentrations and appears to have desirable characteristics as a fish-collecting agent which merits further investigation.

Methods for the fractionation of P in soils were evaluated in the fractionation of P in lake sediments. Both Al-P and Fe-P may be determined readily and precisely by the Chang and Jackson procedure. Reductant-soluble P was more difficult: modifications of a citrate oxidation procedure utilizing KMnO₄ produced an acceptable method. Large amounts of Fe in the Ca-P extracts caused low results, but this was overcome by limiting the aliquot size. Organic P determined by difference between total and inorganic P was not related to the organic matter content of the sediments. An alternative measure of inorganic P, obtained by summing the inorganic P fractions, yielded values for organic P which were correlated with organic matter.

Measurements of canopy opening, understory light, throughfall precipitation, and understory herb response in leaf surface area per square meter in pine forests on light—textured soils in northern Wisconsin show that the understory herb layer is more responsive to differences in throughfall precipitation determined by canopy opening than to difference in light. Canopy opening controls both the level of light reaching the herb layer and the proportion of total precipitation reaching the litter layer, but the light levels are apparently considerably above the minimum thresholds for these species. On the light—textured soil—moisture recharge in the surface layers, as influenced by canopy opening, exerts the major control over the total cover of herbaceous species. Moisture content of the lower litter layers and upper soil layer, where most of the northern understory herbs are rooted, is greatly influenced by variations in throughfall determined by canopy opening.

Total plant leaf area of individual maize plants (Zea mays L.) at anthesis was estimated by multiplying the area of leaf number seven, the best estimator in these studies based on correlation analyses, by an appropriate “leaf area factor.” This factor was determined by dividing total plant leaf area by the area of leaf seven, which was the largest or nearly the largest leaf for the 23 genotypes studied. For precise estimation, a factor should be determined for the largest leaf of each genotype or treatment in each population and each year. A very close correlation between estimated and actual leaf areas was observed when the leaf area factor was used. To minimize the error incurred by plant-to-plant variation, at least five plants should be completely measured to determine the leaf area factor for a given genotype. This method of estimation could be applied widely to leaf area measurements in maize and should make it possible to determine leaf areas in yield trials, breeding nurseries, and extensive field tests.

Sodium 2,4,5-trichlorophenate (Dowcide B) (D-B) is used generally as a postharvest dip for Gladiolus corms in the control of Fusarium oxysporium f. sp. gladioli Synd. and Hans. D-B solutions were reduced gradually in fungicidal effectiveness and the pH was reduced similarly when used continuously for dipping corms. The end point for renewing solution was determined in terms of pH and number of corms treated.

A method for experimental determination of residual stresses in electro-deposits is described. According to this method a deposit to be investigated is deposited on the external surface of a thin-walled tubular cathode (Fig. 4) placed in a tank with rotating anodes (Fig. 3). At the same time, by using electrical-resistance strain gauges on the internal surface of the cathode strains are measured as a function of variable deposit thickness. Initial stress and residual stresses are determined via approximation of experimental information, applying the method of averaged sum. Determination of elastic constants of the substrate and coating materials is described. Technological problems of strain measurement are considered. An example of the processing of measurement data is presented. Initial stresses are determined for a number of cathode materials and galvanic iron coatings (Table 3). | Õhukeseseinalise torukatoodi deformatsioonimeetodiga uuriti omapingeid kulunud masinaelementide taastamiseks kasutatavates galvaanilistes raudkatetes. Artiklis esitatakse nende uurimiste metoodika ja tulemused. | Bei der Untersuchung von Eigenspannungen in galvanischen Eisenüberzügen zwecks Wiederherstellung der verschlissenen Maschinenelemente wurde das Formänderungsverfahren der dünnwandigen Rohrkathode verwendet. Der Beitrag erläutert die Methodik und Ergebnisse dieser Untersuchungen.