Copies of author's previously published articles inserted. Bibliography: leaves 150-166.

Thesis--University of Florida. / Description based on print version record. Typescript. Vita. Includes bibliographical references (leaves 137-153).

Call number: LD2668 .T4 1946 H33 / Master of Science

No description available.

Thesis (MSc)--Stellenbosch University. / VOORWOORD: Die skrywer wens daarop te wys dat in sover dit die wynstok aangaan, hierdie werk wat Suid-Afrika betref, van 'n aanvoor-geaardheid is. Ook in verband met die wortelverspreidings van bladwisselende vrugtebome is daar, sover bekend, in hierdie land nog geen wetenskaplike werk gepubliseer nie. Direkte leiding in verband met hierdie studie was dus tot 'n groot mate onverkrygbaar. Daar dien ten slotte daarop gewys te word, dat hierdie studie op 'n beperkte hoeveelheid geskikte onderstokke uitgevoer is, en dat wingerde nie vooraf vir die doel aangelê kon word nie. By 'n studie van hierdie aard sou die voltydse samewerking van 'n grondskeikundige ook 'n aanbeveling gewees het.

Adventitious root formation can be inhibited in stem cuttings of Pisum sativum L. (pea), an easy-to-root species, if the apical and lateral buds are removed. Application of exogenous auxin to the apical stump can replace the rooting stimulus produced by the buds. Root number was reduced by 50 to 100% in the decapitated and disbudded cuttings supplied with an apical source of auxin if photosynthesis was inhibited by 50 to 100% by any of several treatments. The extent to which rooting was reduced was roughly proportional to the extent to which photosynthesis was reduced. Basipetal transport of radioactivity from apically applied ¹⁴C-IAA, as well as basal carbohydrate content, was also consistently reduced under conditions where photosynthesis was inhibited. It appears the reduction in rooting due to a reduction in photosynthesis must take at least two factors into consideration, the transport of auxin from the apex to the base of the cutting and the basal carbohydrate content. The environmental conditions during the stock plant growth are important to the rooting of cuttings. In the present investigation, when pea and Rhododendron stock plants were subjected to low light or to a period of darkness, the rooting of cuttings taken from these plants was significantly promoted. For pea, the promotive effect of darkness was significantly greater when the entire plant was placed in the dark compared to a localized darkening of the stem segment from which roots emerge after excision. The timing of the light and dark periods during stock plant growth also greatly influenced rooting, the greatest promotion was observed when the dark period was given immediately after emergence of the stock plant. This suggests that the root promoting effect of darkness can be destroyed by a brief period of light early in the development of the stock plant. The basal carbohydrate concentration during the first week of rooting was similar in cuttings taken from stock plants receiving light throughout the growth period and those receiving a dark period of 4 days, regardless of whether the dark period was given immediately after emergence or after an exposure to light. This suggests carbohydrates do not play a major role in the promotion of rooting due to a dark treatment on the stock plant. / Graduation date: 1985

No description available.

No description available.

Dissertation submitted for the qualification Master of Science in Chemistry (full time) University of Witwatersrand November 2015 / Irones are the pleasantly smelling terpenoids of orris oil used in the fragrance industry that are extracted from the rhizomes of Iris species through a lengthy process. Unfortunately syntheses of irones using chemical methods or Iris rhizome-derived sources have been reported to be long, unsafe and low yielding. These inefficient methods have therefore resulted in a high cost of the orris absolute (an alcohol extract of orris butter) which costs between 40 000 and 70 000 Euros/kg. A promising enzymatic process for irones production with good conversion of the precursors has been reported. However, the processing of the irone source into iridals (irone precursors) requires high temperatures and as a result the safety as well as energy input of the method is affected. Moreover, the prior solvent extraction was reported to affect the quality of the product. The present research aimed to develop a rapid and effective enzymatic process for the production of α- and γ-irones at 2L scale-up, as well as obtaining the final product in the form of orris butter. During the current studies a method for analysis of the irones samples was developed, and subsequently different solvents were investigated to identify the best sampling method. Thereafter different oxidoreductases were screened to identify the best enzyme source for maximum production of irones. Optimization of temperature, loading of lipoxidase, orris root, oleic acid, and dioxane, the ratio of minerals to irone concentration, incubation period and use of anti-fungal agents were investigated for maximum irones production. Furthermore, different methods to concentrate the irones and to produce the final orris butter product were evaluated. Lastly, testing the effect of purifying the enzyme on the production of irones was investigated. At laboratory scale the optimum reaction conditions were found to consist of incubating 5 g of fresh homogenised orris root with 20 mL crude soybean lipoxidase (prepared as 1 g soybean flour in 25 mL of 0.01 M borate buffer pH 9.2), with 50 mg manganese chloride and 25 mg ferrous sulphate, 1 mL dioxane and 0.25 mL oleic acid, for 5 days at 37°C in a rotatory shaker incubator. The laboratory scale product could be recovered by using a mixture of equal proportions of acetone and-DMSO for sampling under stringent sterile conditions. At the 700 mL and 2L scale it was determined that with improved agitation and oxygenation of the reaction mixture and subjecting the maturated suspension to Likens-Nickerson distillation resulted in the required orris butter profile. It was further found that purification of the enzyme reduced its ability to efficiently convert the precursors in fresh orris root into irones. Alpha (α-) and gamma (γ-) irones) of the same retention times (3.79 and 3.82) and mass (207 Da) as the α-irone commercial sample were produced at yields around 696 mg irone/kg dry orris root compared with 530 mg irone/kg dry orris root seen with traditionally processed rhizome. The current research is the first to use crude soybean lipoxidase to oxidize macerated fresh orris root into irones, and the first to identify the importance of minerals in the bioconversion.

Contemporary methods of resection and management of the root end during apical surgery were reviewed. Two studies are reported here, one on the amount of peripheral root structure remaining after root-end cavity preparation in maxillary central incisors and canines, and the other on the effect of the dimensions of the cut root face on the size of the root-end cavities cut by experienced endodontists. To investigate the amount of peripheral root structure remaining after root-end cavity preparation, three senior endodontic graduate students were asked to prepare conservative root-end cavities in thirty root-treated maxillary central incisors and thirty canines. Not a single tooth had the recommended 2 mm circumferential root dentine after 3 mm resection. Sixty two percent of the central incisors did not have a 2 mm dentine periphery around the root-end cavity preparations after 6 mm resection. To investigate the effect of the dimensions of the cut root face on the size of root-end cavities, five practicing endodontic specialists prepared conservative root-end cavities in thirty single-rooted teeth each after resection of the apical 3 mm. The endodontists prepared larger cavities in larger root faces. More precisely, the cavity sizes suggested that the endodontists were suffering from the effects of a visual illusion, the Delboeuf illusion. There are two major conclusions. First, the theory concerning the amount of circumferential dentine in a resected root face needs revision. Second, endodontists need to be aware of how the appearance of a cut root face can influence the size of cavities they cut.