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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Optimal Cultural Practices for Processed Sweetpotato Products

Smith, Cody Derek 29 June 2012 (has links)
As the sweetpotato industry moves towards more processed products, there is a need to develop strategies in which to optimize total yield and reduce costs. Unlike the fresh market product, desirable processing roots are larger in size and overall tonnage is preferred over aesthetic appeal. Plant spacing and row width along with planting dates and harvest dates are believed to affect the size and tonnage of sweetpotato roots. The Beauregard and Evangeline varieties were planted at an early planting date (June 1) and a late planting date (July 1) on 38 and 42 inch row spacing. Harvests were at ~125 and ~140 days after planting. The delay in harvest increased yield of all grade categories except for U.S. No.1. The first planting date was also superior to the second planting date. Row width had a marginal effect. Only the canner grade was significantly higher for the 42 inch width in 2010 which caused the total yield category to be significantly higher. Plant spacing was less important and demonstrated that lower planting densities are possible. Furthermore, results demonstrated that a delayed harvest does not reduce the U.S. No.1 yield and only increases total yield. Storage root quality must be maintained all the while reducing costs. Consumers demand processed sweetpotato products that taste as good as the fresh market product. Many times roots for processing are not cured and therefore do not gain in sugar contents and visual appeal. Roots could possibly be left in the field after de-vining and before harvest in the hot, humid times of the year which is similar to the curing room environment. Beauregard and Evangeline varieties were de-vined in successive days from day 0 to day 4 early in the harvest season (~September 1) and late in the harvest season (~November 1). Raw and French fry roots were analyzed for sucrose, fructose, glucose, maltose, and total sugar content. As the de-vining period was extended, few treatments showed trends toward higher sugar contents. Significant differences did exist but they were not consistent enough to recommend a reliable field curing schedule that would increase sugar contents.
2

Poultry Litter Ash as a Phosphorus Source for Greenhouse Crop Production

Wells, Daniel Evan 22 April 2013 (has links)
Phosphorus (P) is an essential nutrient for all life forms, including plants, but is a limited agricultural resource whose future availability is in question. Therefore, identification of alternative forms of P fertilizers is important. Poultry litter ash (PLA), a byproduct of bioenergy production, contains high concentrations of P comparable to conventional fertilizers. Forms of P contained in PLA have been characterized as having low water solubility. Nutrient losses during containerized plant production are high due to excessive inputs of water and nutrients and low nutrient sorption capacities of common horticultural substrate components. Environmental concerns over reduced water quality intensify this problem. Use of low soluble P sources has been recommended as a potential means of reducing P losses. Experiments were conducted to determine effects of PLA application on growth, quality, and nutrient uptake of two greenhouse crops (Verbena canadensis Britton Homestead Purple and Lantana camara L.New Gold), substrate chemical properties, and P losses during greenhouse crop production. In the first experiment, substrate leachate-pH increased 25% when PLA was applied instead of superphosphate (SP). Foliar P concentrations of verbena and lantana also increased 27 and 62%, respectively. Application of PLA did not reduce biomass of verbena or lantana. In a subsequent experiment, leachate-dissolved reactive phosphorus (DRP) and effluent-total phosphorus (TP) concentrations were reduced >92% and 69%, respectively, through PLA application, however, plant growth and landscape establishment was not deleteriously affected. Water solubility of PLA-P decreased markedly as combustion temperature increased. Finally, in a third experiment, concentrations of DRP were reduced 24% through reduction of PLA rate, but were reduced 134% when PLA was topdressed instead of incorporated. Plant quality was improved with PLA incorporation. These results indicate that, while P loss reduction can be achieved through PLA application, lower substrate P concentrations do not necessarily reduce plant growth or quality.
3

Viral Stress Activation of Retrotransposons in Sweetpotato [Ipomoea Batatas (L.) Lam.]

Kokkinos, Charalambos Demetriou 10 July 2002 (has links)
Mutations in sweetpotato [Ipomoea batatas (L.) Lam.], which are poorly understood, are widely implicated as a component in cultivar decline. In sweetpotato, mutations are also likely to result from the activity of plant retrotransposons, which are known to be present in the sweetpotato genome. The majority of the transcriptional activity of plant retrotransposons that has been characterized to date, is stress-induced, involving both biotic and abiotic stresses. Viral infection, a form of biotic stress, is also one that commonly occurs in sweetpotato. The objective of this study is to test whether viral stress, in the form of single and combined viral infections, transcriptionally activates Ty1-copia elements, a family of LTR retrotransposons, at the whole-plant level. To assess activation, transcripts from the RT domain of Ty1-copia elements were relatively quantified using Real-Time Quantitative PCR. Relative amounts of transcripts from five viral inoculation treatments were then compared to those from the virus-free plants of the control treatment. Results showed that the relative amount of Ty1copia transcripts from the viral combination treatment of BWFT-3 (SPCSV isolate) + SPFMV, which produced the most severe symptoms on both varieties tested, was significantly higher than the other viral treatments and the control. No significant difference was observed among the other treatments. No significant difference was also observed in transcript amounts between the two cultivars inoculated with the same virus. This represents the first study examining the effect of stress on relative transposon transcriptional activation.
4

Control of Two Perennial Grasses in Southern Turfgrasses

Strahan, Ronald Eugene 15 November 2002 (has links)
Knotgrass (Paspalum distichum L.) and torpedograss (Panicum repens L.) are perennial grasses that are extremely difficult to remove in established turfgrass. Studies were conducted to determine the potential for controlling these troublesome perennial weeds. Pot studies were conducted for two years to evaluate several herbicides with multiple modes of action for knotgrass control. In graminicides studies, 8 weeks after initial application (WAI) single or split applications of fluazifop or quizalofop provided excellent control (88 to 95%). In contrast, single or split applications of fenoxaprop at 0.21 kg ha-1 and single applications of diclofop at 0.84 kg ha-1 were no better than the untreated check. Single applications of sethoxydim at 0.62 kg ha-1 were similar (85%) to sequential applications at 0.31 kg ha-1 (90%). MSMA, the industry standard, provided less than 40% control knotgrass control. In nonselective studies, glyphosate, glufosinate, and sulfosate were evaluated at equivalent rates (1.12, 2.24, or 4.48 kg ha-1). At 7 WAT, knotgrass control was at 99% for glufosinate, regardless of rate applied. All rates glyphosate and glufosinate or sulfosate applied at 2.24 and 4.48 kg ha-1 were similar and provided at least 95% knotgrass control. However, sulfosate applied at 1.12 kg ha-1 only controlled knotgrass 79%. In studies evaluating quinclorac, control was greater with the herbicide applied at the highest rate (2.24 kg ha-1). Knotgrass was not satisfactorily controlled, however, as control never exceeded 34%. Field and greenhouses studies were conducted to evaluate clethodim for torpedograss control in centipedegrass. Single or sequential applications of clethodim at 0.60 kg ha-1 and sequential applications at 0.30 kg ha-1 were more effective than sethoxydim applications. Torpedograss control with clethodim however, was not acceptable and did not exceed 79% throughout the study. Torpedograss control with sethoxydim was no greater than 55%. Although still commercially acceptable (< 30% injury), clethodim caused some moderate centipedegrass injury. In greenhouse studies, several spray adjuvants were evaluated to increase the efficacy of clethodim. Results indicated that herbicide rate is more critical than the adjuvant. Regardless of adjuvant, clethodim at 0.60 kg ha-1 controlled torpedograss better than the 0.30 kg ha-1 rate (62 vs 44%).
5

The Effects of Mutations and Viruses on Yield and Quality of Sweetpotato, Ipomoea batatas (L.) Lam

Carroll, Heather Wallace 01 April 2003 (has links)
Twelve virus-tested mericlones were derived from virus-infected 'Beauregard' clones to compare relative effects of viruses and mutations on yield and quality. Virus-tested refers to plants derived from meristem-tips that have been assayed three times with virus sensitive indicator plants Ipomoea aquatic and I. sestosa. The clones represent various selections from 10 production areas in Louisiana, two clones from the foundation seed program at Louisiana State University AgCenter Sweetpotato Research Station, and the industry standard virus-tested B-63 mericlone. Two yield plantings were made in the years 1998 and 1999. Overall, in three of four planting dates, virus-tested mericlones had significant yield increases of 92% to 505% for U.S.#1 over their respective virus-infected clones. Yield increases in three of four plantings ranged from 9% to 1000% for U.S.#1 grade for virus-tested mericlones when compared to their virus-infected clone counterparts. The majority of the tests showed virus-tested mericlones had a higher root and vine weight than virus-infected clones. Virus-tested roots had a significantly redder skin, while virus-infected roots had darker hued flesh and cortex. This has not been previously reported. Comparisons within virus-tested clones did not show any yield differences or differences in color, suggesting clonal variation has a minor affect on general agronomic traits of 'Beauregard' sweetpotato. Ten decamer primers were used in RAPD analysis of the virus-tested mericlones and virus-infected clones. No polymorphisms were found among 29 DNA markers assessed. In summation, data suggests that 'Beauregard' has a relatively stable genome and that variation among clones is mostly a function of virus infection.
6

Evaluation of Fertilizer and Irrigation Production Systems for Large Nursery Containers

Witcher, Anthony Lynn 07 April 2003 (has links)
Container-grown woody ornamentals require high volumes of water and sufficient nutrients to develop into healthy, high quality plants. The increased awareness of possible contamination of ground and surface water resources from nursery runoff has forced growers to implement higher water use efficiency techniques to maximize fertilizer efficiency and reduce nutrient and irrigation runoff. Components of a large container production system that could affect irrigation volume, substrate nutrition levels and runoff include fertilizer placement, irrigation frequency and irrigation method. Irrigation and fertilization components were evaluated in two experiments to determine which would maximize growth, minimize effluent and reduce the amount of nutrient loss from container substrate. Treatments tested included fertilizer placement (incorporated and topdressed), irrigation frequency [once daily (1x) and three times daily (3x)] and irrigation method (drip rings and spray stakes). In the first experiment, Ulmus parvifolia Jacq. (Chinese elm) trees were grown for a year and new trees were planted the second year. In the second experiment, Lagerstroemia indica x fauriei 'Acoma' ('Acoma' crape myrtle) trees were grown for two consecutive years. Incorporated fertilizer produced higher growth indices and maintained higher substrate nutrient content (N, P and K) in chinese elms compared to topdressed fertilizer. Similar results where found in crape myrtle with the exception of P substrate content, where no significant differences occurred. In the chinese elm experiment, the 3x irrigation treatments resulted in higher growth indices and less effluent compared to 1x irrigation. Conversely, 3x irrigation resulted in higher growth indices but no differences in effluent in the crape myrtle experiment. Spray stake treatments resulted in less effluent in the elm study. Drip ring treatments produced larger growth indices in the crape myrtle study. These results suggest a grower could maximize growth and greatly reduce runoff by incorporating fertilizer, practicing cyclic irrigation methods and using drip rings in a large container production system. These results could be used to improve the nursery best management practices in a container nursery production setting.
7

Field Grown Cut Flower Production in Southern Louisiana

Young, John Burke, Jr. 10 April 2003 (has links)
Specialty cut flowers are nontraditional cut flowers used primarily in floral arrangements. Most specialty cut flowers are grown in an open field and production is dependent on a combination of climactic factors, which in turn affects the number of days to harvest and yield. Scheduled plantings of Celosia argentea var. cristata L., Helianthus annuus L., Zinnia elegans Jacq., and Gladiolus X hortulanus L. H. Bailey were conducted to determine the effect of time on the number of days to harvest and yield. Plants were grown in an open field from February to August in 2001 and 2002. Days to harvest decreased for the later planting dates of Gladiolus and Zinnia, but varied between planting dates for Celosia and Helianthus. Postharvest longevity of pollen-producing and pollenless cultivars was found to be similar, but longevity appears to be cultivar dependent. Few differences in yield for branching cultivars of Celosia and for two cut stem lengths of Zinnia were found over the planting dates. Scheduled plantings of cut flowers are necessary for season-long production of a particular crop however; days to harvest and yield may vary throughout the growing season for a particular crop.
8

The Integration of a Formal Garden Curriculum into Louisiana Public Elementary Schools

Smith, Leanna Lynn 06 June 2003 (has links)
School gardens have been and are in use today at schools around the United States to supplement their curriculum. Very little research, however, has been conducted to quantify the benefits that gardening provides to students. The first four chapters of a hands-on gardening curriculum (Junior Master Gardener Handbook Level One) were introduced into three East Baton Rouge Parish elementary schools the fall semester of 2002. Science achievement tests developed at Texas A&M University specifically for the Junior Master Gardener program, were given both before and after the students participated in the gardening activities to determine whether or not the activities helped improve achievement scores. The curriculum was introduced as an informal education program conducted by East Baton Rouge Parish Master Gardener volunteers and Louisiana State University students once a week for two hours during regular school hours. The results were significantly different (P < 0.0167) between the experimental classes pre- and posttest scores, while no significant difference was found between the pre- and posttest scores of the control classes. No significant difference was found between the experimental and control classes due to treatment. Several variables may have affected the outcome of the study, but the results show that even once weekly use of gardening activities and hands-on classroom activities help improve science achievement test scores.
9

Rhizome Manipulation Affects Growth and Development of Ornamental Gingers

Paz, Maria del Pilar 12 November 2003 (has links)
Ornamental gingers are popular cut flowers and have been promoted as a promising potted flower crop because of unique foliage, long-lasting colorful bracts, and few pest problems. Rhizomes are the primary means of propagation in late spring followed by shoot growth and flowering, and plants enter dormancy under short days in the fall. Termination of dormancy is important for greenhouse forcing and extending the growing season. Rhizomes of five ginger species (Curcuma alismatifolia Gagnep., C. cordata L., C. roscoeana Wallich, Globba winittii C.H. Wright, and Kaempferia galanga L.) were either: 1) stored for 0 to 16 weeks at 15, 20 or 25 C; or, 2) stored for 0 to 2 weeks at 10 or 15 ºC followed by 0 to 2 weeks at 25, 30, or 35 ºC; or, 3) treated with 0 to 300 ppm ethephon or BA and then stored for 0 to 3 weeks to determine the effect on growth, development, respiration rates, and carbohydrate content. Upon completion of treatment application, rhizomes were planted in a peat moss:bark:perlite mix and placed in a greenhouse with 25 ºC day/21 ºC night temperatures with 40% shade. DTE and DTF for Globba were hastened when rhizomes were stored for 16 weeks at 25 ºC or 3 weeks at 15 ºC followed by 3 weeks at 30 ºC. For C. alismatifolia, DTE and DTF were hastened when rhizomes were stored for 3 weeks at 10 ºC followed by 3 weeks at 30 ºC. For C. cordata, DTE and DTF were hastened with rhizome storage of 2 weeks at 10 ºC followed by 3 weeks at 35 ºC. For C. roscoeana a 3 or 4 month storage treatment was found to hasten emergence. Results indicated that Kaempferia should be stored at 25ºC for 16 weeks to enhance emergence and flowering. Neither application of ethephon nor BA significantly affected growth or flowering of any in the ginger species after storage. The response of respiration and carbohydrate concentration was not consistent with rhizome and plant growth responses.
10

Enhanced Pectin Degradation is Associated with the Ease of Fruit Detachment in Tabasco Pepper

Arancibia, Ramon Alejandro 14 November 2003 (has links)
Pectin metabolism was analyzed in tabasco pepper (Capsicum frutescens L.) to determine the metabolic process associated with the ease of fruit detachment from the calyx. Two genotypes that differ in the fruit detachment force (FDF) were used: 'Easy Pick' (EZ) which requires a low force and 'Hard Pick' (HP) which requires higher force. Pectin dissolution in fresh ripe fruit tissue and in extracted fruit cell wall was higher in the EZ genotype than the HP genotype and inversely correlated to the FDF. Size-exclusion chromatography of EDTA-soluble polyuronides indicated that pectin was degraded in ripe tissue from both genotypes, but the degree of depolymerization was more extensive in the EZ genotype. The ease of fruit detachment was, therefore, attributed to pectin ultra-degradation. Polygalacturonase activity, however, was the same in protein extracts from both genotypes. In contrast, pectin methyl-esterase (PME) activity in vivo assessed by methanol production was detected in ripe fruit of the EZ genotype only and it was associated with the FDF decline. The decrease in degree of pectin esterification and pH at the fruit junction area detected in EZ ripe fruit was attributed to PME activity in vivo. PME activity in vitro, however, was detected in protein extracts and disrupted tissue from both genotypes at all ripening stages. This suggests that a PME regulatory mechanism may be blocking PME activity in vivo. Two PME isoforms were detected in protein extracts from ripe fruit. The PME-1 form was detected in EZ genotype only and appears to be responsible for methanol production in vivo. A predominant 36.7 k protein was associated with localized pH reduction in a pectin-agarose gel. The PME-2 form was detected in both genotypes and appears to be active in disrupted tissue only. A 40.8 k protein was resolved consistently in PME-2 active fractions. In conclusion, PME-1 appears to be responsible for PME activity in vivo and was associated with the ease of fruit detachment in tabasco pepper.

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