Browsing by Subject "Plants"
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Item Allozyme investigation of the isoetes riparia alltetraploid complex(Texas Tech University, 1998-12) Caplen, Cynthia AnnThis thesis addresses a systematic problem within Isoetes, a genus comprising approximately 150 species worldwide, 25 of which are currently known from North America. Isoetes is the sole extant genus of Isoetaceae which, along with Lycopodiaceae and Selaginellaceae, are the extant families of Lycopodiophyta, the most primitive division of vascular plants. Isoetes is heterosporous, i.e., producing sexually dimorphic spores, an apomorphic condition shared via convergence with spermatophytes but restricted among pteridophytes to a few taxa. Isoetes microspores (male) are usually less than 50 microns in diameter while megaspores (female) are mostly greater than 300 microns in di£mieter (Taylor et al. 1993). Isoetes comprises herbaceous perennials with a very simple yet unique form. This uniqueness in form helps to distinguish Isoetes from other kinds of plants, but their simplicity poses difficulty in species identification due to a resultant lack of taxonomic characters. Isoetes plants have a small, lobed, subterranean stem (corm) from which a spiral array of terete to angular quill-like microphylls (leaves) ascend, acheiving lengths of 1 to 100 cm. Each microphyll possesses either a microsporangium or a megasporangium that develops on the adaxial side of the expanded microphyll base. Sporangia are covered to varying degrees by a thin layer of tissue, the velum (Taylor et al. 1993).Item An in vitro evaluation of a Pseudomonas Syringae pv. Tagetis strain as a potential biocontrol agent(Texas Tech University, 1997-12) Krieg, AndreaThe potential of SL Pseudomonas syringae pv. tageris Tox strain to provide control of the Tox* strain was tested using competition as a basis for comparison. Initially, growth curves of individual strains in both complex and defined media were developed In the complex medium 523, the Tox strain did exhibit greater growth than the other two strains tested and was significantly greater at two points during the assay. In all othCT media tested, the growth of the three strains was almost identical. Ratios of the Tox to Tox*/Rif strains -1:1 and 3:1, WCTC then tested in minimal salts (defined) and 523 (complex) media. In the defined medium, the ratio began and ended at the same point, either 1:1 or 3:1. In the complex medium, only the 1:1 ratio was tested and this ended in a 4:1 ratio in favor of the Tox strain. The 3:1 ratio as well as individual strains were then tested using sunflowCT leaf disks. The Tox and Tox*/Rif strains alone grew much faster than the Tox' strain in the ratio, while the Tox^/Rif strain grew almost as well as it did inoculated as a single strain. The ratio behaved in contradiction of the behavior obsoved in culture. The Tox strain seemed to be inhibited in the ratio and the data taken at 48 hours was 1:5 in fiavor of the Tox*/Rif strain. While still contradicting the results obtained in culture media, the whde plant assay did not follow the same pattern as that seen in the leaf disk assay. At 24 hours, the ratio between the Tox and Tox^/Rif strains which began at 3:1, had shnmk to a little more than 1:1. Data taken at 48 hours showed that the Tox^/Rif strain's population had outgrown that of the Tox' strain reversing the ratio to 1:1.4. From the data presented, it can not be concluded that the Tox strain is capable of providing any measure of biological control of the Tox*/Rif strain.Item Analysis of glutathione S-transferase (GST) gene expression in transgenic plants and its effects on environmental stress(Texas Tech University, 1998-08) Kang, Won-HeePlants cannot escape from biotic and abiotic stress factors such as extreme temperatures, high light intensity, drought, UV radiation, heavy metals, and pathogen attack. Anthropogenous stress factors, such as herbicides, also affect or block metabolism, growth, and development, and is being used every year. Plants have versatile detoxification systems to counter the phytotoxicity of a wide range of natural and synthetic compounds, which are present in the environment. Glutathione S-transferases (GSTs) are the enzymes that detoxify natural and exogenous toxic compounds by conjugation with glutathione. Glutathione, an endogenous tripeptide, is important as a reducing agent, nucleophilic scavenger, and alleviate the chemical toxicity in the plants by the reaction of GST. GSTs play an important role in the phase Ii of conjugation with xenobiotics, and have another role as glutathione peroxidase. Glutathione conjugates are can be transported to the vacuoles or apoplast and are generally much less toxic than the parent compounds. Oxygen radicals are also highly harmful to the cell components. Those toxic reactive oxygen species damage DNA, lipid layer, and proteins. Many GSTs can also act as glutathione peroxidases to sacvenge toxic peroxides from cells. A cDNA named Gh-5 was isolated from cotton fiber cDNA library, using PCR-based cloning methods. Analysis of this cDNA revealed high sequence similarity with other plant GSTs. Expression of Gh-5 in E. coli resulted in protein extracts with high GST activity. Overexpression of Gh-5 in tobacco has led to about a two-fold increase in GST specific activity compared to the nonexpressing control plants. These results indicate that Gh-5 encodes an active GST both bacterial and in plant cells. Antisense GST constructs were also developed to deactivate native cotton GST and to evaluate the effect of the decreased enzyme in cotton plants. In order to determine whether GST overexpression could confer protection to plants against oxidative stresses, transgenic plants were exposed to herbicides, salinity, low temperature, heavy metals and photooxidation. The GST overexpressing plants showed enhanced seedling tolerance to low temperature and salinaty. These results indicate that increased level of GST can protect plants from certain types of environmental stresses.Item Biochemical factors associated with photosynthetic activity of cotton(Texas Tech University, 1980-12) Tang, RueilienRecent observations and measurements of whole leaf photosynthetic rates in cotton indicate that the productivity of leaves declines rather significantly prior to the completion of fruit development. These results, coupled with a loss of existing leaf area, indicate that yield potential is possibly not maximized due to inadequate organic material to completely fill the fruit. The photosynthetic rate decline is apparently related to source:sink ratios and possibly to the need for nitrogenous material by the fruit. The exact cause of the response is not known, although it is suspected that carboxylation enzyme activity is intimately involved. The basic objective of this project was to develop an understanding of the causes of the photosynthetic rate decline in aging leaves of cotton.Item Biochemistry and physiology of water stress in cotton, corn, and sorghum(Texas Tech University, 1977-05) Ackerson, Robert CharlesThe purpose of this study was to investigate the effects of water stress on specific physiological and biochemical processes in field grown cotton (Gossypium hirsutum L.), com (Zea mays L.) , and sorghum (Sorghum bicolor L. Moench)o These three crops are distinctly different witli respect to their drought tolerance. Investigation of such processes as regulation of water use, photosynthesis and specific enzyme activity were conducted in order to ascertain whether these parameters were differentially affected by water stress in the three species. Elucidating the level of water stress required to inhibit a physiological process or identifying specific factors that confer drought tolerance to one species as opposed to another, may aid in enhancing agricultural productivity particularly in many arid and semi-arid environments. Furthermore, once specific limiting factors of growth under water stress situations are identified, these data can be utilized in a comprehensive effort toward producing more drought tolerant genotypes within a crop species.Item Biosolids and chemical fertilizer application on the Chihuahuan desert grasslands(Texas Tech University, 1998-08) Cooley, Philip EarlSewage sludge or biosolids refers to the solids removed from municipal waste water during treatment. Currently, sewage sludge is used to refer to untreated material, while biosolids refers to treated material., There are several estimates as to how much sewage sludge is currently produced or will be produced in the U.S. in the future. On average, a typical person generates 16.9 liters of sewage sludge per week (Chermisinoff, 1993). According to the U.S. Environmental Protection Agency (USEPA, 1989) approximately 6.5 million dry tons of sewage sludge are generated annually, and this is expected to increase to approximately 13 million dry tons by the year 2000. Due to the large quantities of sewage sludge generated, management of treated sewage sludge, or biosolids, is becommg increasingly important. The Marine Protection Research and Sanctuary Act of 1988 banned ocean dumping of biosolids as a disposal technique, leaving only land filling, incineration, and land application. Land filling is facing increased regulations because of ground water pollution and decreases in available land fill space. Incineration is also plagued with problems, such as air pollution, high energy input, and capital costs. Land application is a promising alternative to ocean dumping. Land application is defined as the spreading of biosolids on or just below the soil surface, and is becoming a widely used sludge management option. Land application is divided into four categories: agricultural use, forest lands, land reclamation, and land dedicated to sludge application. Land application is encouraged by the EPA wherever environmentally feasible (USEPA, 1989). Land application has been beneficially used on croplands, forest lands, and reclaimed mines throughout the U.S. However, land application has not been widely studied in the arid and semi-arid southwest or on native rangelands. The desert southwest, including the Trans-Pecos region of Texas, receives low and unpredictable rainfall and has high temperatures, high evaporation rates, and low organic matter contents in the soil All of these factors limit native plant growth on rangelands. Application of biosolids might ameliorate some of these conditions by providing organic matter to the soil and reducing soil water evaporation. In addition, biosolids contains several plant macro- and micro- nutrients such as nitrogen, phosphorus, copper, manganese, and zinc that can increase plant production. As long as biosolids do not cause detrimental effects in this semi-arid environment, the Trans-Pecos is an excellent area for land dedicated to sludge application for several reasons: vast acreages of available land, and few estimated number of days when biosolids can not be applied because of unfavorable weather (precipitation) (USEPA, 1989).Item Item Correlation between chlorophyll levels, photosynthetic rates and palisade chloroplast morphology in selected strains of cotton (Gossypium hirsutum)(Texas Tech University, 1986-05) Short-Russell, Sharla Rene'The relationships between chlorophyll levels, photosynthetic rates and palisade chloroplast morphology (determined with stereological techniques) were investigated using two groups of cotton varieties grown in open fields. The first group was studied for two years and consisted of four strains, T-125, T-166, T-231 and T-766, which had no differences in net photosynthesis per leaf area of tissue (mg carbon dioxide/dm^/h). However, T-125 and T-166 had less total chlorophyll per leaf area of tissue than did T-231 and T-766. The second group, consisting of T-249 and T-301, had no differences in total chlorophyll, but did have differences in net photosynthesis per area of leaf tissue—T-249 had a significantly lower rate of photosynthesis per leaf area than did T-301.Item Diurnal and seasonal patterns of xylem water potential in three cultivars of cowpeas (Vigna unguiculata (L.) Walp.)(Texas Tech University, 1982-12) Smallwood, Douglas GaleThe purpose of this investigation was to determine the optimum sampling time for detection of maximum genotypic differences in 4' and the feasibility of using 4' as a drought screening tool, with the ultimate goal of developing high nitrogen fixing, drought-resistant cowpea cultivars.Item Effect of nitrogen on the uptake of perchlorate by plants(Texas Tech University, 2004-08) Joseph, Preethi CPrevious studies have shown that plants were tolerant to perchlorate and will accumulate perchlorate in plant tissues. The objectives of this research were to determine the effect of nitrogen type (Ammonium or Nitrate) and concentration on the rate and extent of perchlorate uptake in lettuce and soybean plants. Studies were conducted in plant growth chambers and in greenhouses using sand as a support medium. Treatments included studies with defined laboratory fertilizer solutions at varying concentrations of nitrogen and constant concentrations of other ions, as well as with commercial NH4+ and NO3- based fertilizers at varying loading rates. The growth of plants was affected in response to varying nitrogen concentrations and sources. The perchlorate accumulation in plants was determined on a weekly basis by extracting the plant and sand samples and analyzing them for perchlorate levels using ion chromatography. In all experiments, plant growth was severely affected, and in most cases, plants did not proceed past the two leaf stage of growth. Perchlorate was detected in all plants with peak concentrations occurring between 3-6 weeks of growth and declining thereafter. The plant perchlorate concentrations were higher in plants fertilized with ammonium fertilizer than with the nitrate fertilizer although the difference in plant growth between treatments makes it difficult to say whether this would be observed under normal conditions. The perchlorate concentration also generally increased with an increase in nitrogen concentrations applied to the plants. Overall, the effects of source and nitrogen concentration are unlikely to have significant effects on perchlorate uptake in plants under normal environmental conditions.Item Effects of different seasons of biosolids application on tobosagrass growth(Texas Tech University, 1996-08) Jurado-Guerra, PedroBiosolids are a by-product of wastewater treatment with high organic matter content. The use of biosolids to improve arid rangelands has not been extensively studied. Biosolids rates of 0, 14, 36, or 68 dry Mg/ha/yr were applied to tobosagrass (Hilaria mutica (Buckl.) Benth.) in a desert grassland in west Texas. Biosolids were applied twice-a-year either in winter/summer (WS) or spring/summer (SS) for one year only or two consecutive years. Half of the plots were irrigated. In the first growing season, tobosagrass plant length increased with WS appHcations, irrigation and at 36 and 68 Mg/ha application rates. Tobosagrass standing crop increased at the 68 Mg/ha rate in both seasons, with a more dramatic increase (86%) above control rates with WS applications. In the second growing season, tobosagrass length responded to all biosolids rates, WS applications for one year only, and irrigation. Tobosagrass standing crop responded with 26, 51 or 41% increases above the control at 14, 36 or 68 Mg/ha, respectively. Standing crop increased in irrigated plots applied for one year only and for two consecutive years. Biosolids either did not affect or increased tobosagrass plant length and standing crop during the two years of this study. Application of biosolids to desert grasslands appears to offer a viable alternative for biosolids management and recycling.Item Effects of short-duration grazing trampling on seedling emergence and soil strength(Texas Tech University, 1987-08) Weigel, Jeffrey RichardEmergence of broadcast-seeded kleingrass (Panicum COloratum L. 'Selection 75') and of native annual forbs and grasses was compared for two seasons in short-duration grazed areas and ungrazed exclosures. Stocking rate in short-duration grazed areas was 2.0 and 1.5 times recommended in 1985 and 1986, respectively. Kleingrass emergence was similar between treatments in both years. Emergence was unrelated to percent foliar cover of preexisting vegetation. In both study years, soil strength was greater in grazed areas. Short-duration grazing provided no beneficial effect on kleingrass emergence or soil strength in either year. Emergence did not differ by treatment in either year for five of ten species of annual forbs and two species of annual grass. Common broomweed fXanthocephalum dracunculoides (DC.) Shinners.], Texas filaree (Erodium texanum Gray.), and meadow flax FLinum pratense (Nort.) Small.] were more abundant in the grazed treatment in one year, while bitterweed (Hymenoxys odorata DC.) emerged more frequently in ungrazed areas in one season. Short-duration grazing at the stocking rates used did not consistently improve or harm emergence of any of the annual species studied.Item Evaluation of limited quality water on landscape ornamentals(Texas Tech University, 2003-12) Stoker, V. J HalbrooksThe quality and quantity of irrigation water is a growing concern for urban and rural areas. The level of salinity in the natural water supply is on the rise due to natural weathering of minerals (Richards, 1954). Landscape plants that tolerate poor water quality could be beneficial for homeowners and growers. The objective of this study was to identify heat and drought tolerant landscape ornamentals that are also useful in areas with elevated salinity levels in the water supply. Treatments included a control and three salinity levels ranging from 1.56 to 6.25 dS/m. Many of the annuals and herbaceous perennials selected for inclusion in this study were Texas Superstar's™. Species chosen for this study Included Coleus X hybrida 'Plum Parfait' (Plum Parfait SuperSun Coleus), Cuphea hyssopifolia (Mexican Heather), Lantana x hybrida 'New Gold' ™ (New Gold ™ Lantana), Mattiholia incanna (Stock plant), Melampodium leucanthum (Blackfoot Daisy), Oenothera missouriensis (Missouri Primrose), Portulaca oleraceae 'Yubi™ (Large-Flowered Purslane), Salvia leucantha (Mexican Bush Sage), Scaveola aemula 'New Wonder™ (New Wonder™ Fan flower), and Verbena bipinnatifida (Prairie Verbena). The irrigation treatments were applied to the 10 species to achieve a minimum 30% leaching fraction each day. Weekly leachates were tested for EC and pH levels. This study took place in the container holding area outside of the Texas Tech University greenhouse in Lubbock, TX, and was repeated four times. Experiment 1 (studies 1 and 2), conducted in summer 2001, ran for a 13 week period, whereas experiment 2 (studies 3 and 4), conducted in 2002, ran for a six-week period. Final EC and pH were measured on the leachate. Final visual ratings were taken at termination of the study and days of survival were recorded along with the dry weights of the roots and shoot. Portulaca oleraceae was determined to be the most salt tolerant (EC 6.25) of the species studied, followed by Lantana x hybrida 'New Gold™ being moderately salt tolerant (EC 3.12). Further research to identify additional herbaceous annuals and perennials for salinity tolerance, and the level of salinity tolerated for desirable production, is recommended.Item Evaluation of seed applied plant growth regulators on cotton germination, emergence, and growth(Texas Tech University, 1998-12) Becker, William DavidSeveral PGRs, each with numerous formulations, are registered for use in cotton as foliar, seed treatment, or in-furrow applications. Manufacturers of these PGRs purport beneficial plant responses, which include more rapid germination and emergence, increased root and shoot development, increased ability to withstand various stresses, as well as increased yields. Research investigating the effects of PGRs on early season growth of cotton has shown inconsistent results. Fungicides and insecticides are routinely applied to cottonseed prior to planting because of the convenience this method of application affords. This same convenience might prove beneficial for PGR applications, but research investigating the effects of seed applied PGRs has also shown inconsistent results. Thus, the objective of this study was to investigate the effects of several commercially available plant growth regulators on germination, emergence, and early season growth of cotton when applied as seed treatments at 0.5x, 1 .0x, and 2.0x the manufacturer's recommended rates.Item Flammability-internal water status of shrubs(Texas Tech University, 1980-12) Peacock, George LouieIn Guadalupe Montains National Park (Texas) a study was conducted to determine the relationship between the internal water status of selected woody shrubs and their tendency to burn. Low correlations v/ere found between leaf relative water content and flammability, .652, .429 and .596, and xylem sap tension and flammability, .658, .665 and .787 for Cercocarpus montanus, Fallugia paradoxa and Quercus grisea, respectively. Leaf relative water content-xylem sap tension curves were developed for each species to determine if xylem sap tension could be used to estimate leaf relative water content. The low correlation coefficients indicated that no significant reliability could be placed on using these curves.Item Genetic and environmental influences on cold tolerance of cotton seedling germination(Texas Tech University, 1995-05) Speed, Thomas R.The Southern High Plains of Texas represents the largest contiguous cotton production area in the United States with over 3.5 million acres planted annually. The Texas High Plains cotton producing region is faced with the challenge of a short growing season. Due to the high elevation and the dry air, cool nights associated with cold fronts are common during the planting season and during the latter part of the boll maturation period. These conditions can keep the mean daily temperature below 15°C and minimum temperatures can drop below 10°C. Temperatures below 15° will not provide adequate heat required for germination and growth or fiber maturation. Lowering the temperature requirement for germination and growth would provide added insurance for early season germination and seedling establishment, extend the growing season, and allow cotton production to move fiarther north on the High Plains. During the germination phase, cotton is very sensitive to chilling injury if soil temperatures drop below 15°C and temperatures at or below 10°C for a few hours can cause serious damage with long term consequences. Soil temperatures at planting can vary greatly from day to day depending upon air temperature, radiation and precipitation events. Subsequently, it is desirable to have varieties that possess the ability to emerge rapidly under differing soil temperature conditions. A nonuniform stand of weak seedlings is a common result of low temperatures during the planting season. Providing a uniform stand of seedlings, as early as possible in the growing season, is critical to the High Plains producer already faced with a short growing season.Item Genotypic and environmental effects on coleoptile length and subcrown internode length in wheat(Texas Tech University, 1986-08) Mnyenyembe, Parichi HanockColeoptile length, crown depth, subcrown internode length and emergence rate index (ERI) of ten commonly grown wheat cultivars in the Central and Southern Great Plains of the USA were studied in the controlled environments and in the field under various planting depths and temperature regimes. In the germination chamber tests, there were significant genetic differences in coleoptile length at 15, 20, 25 and 30 C temperatures. Coleoptile length of all cultivars was maximum at 15 and 20 C. Temperature x cultivar interaction was significant, partially due to a significant reduction in coleoptile length at 30 C. In the greenhouse, cultivars and planting depths differed significantly for coleoptile length, ERI, crown depth and subcrown internode length in most cases. Cultivar x depth and cultivar x temperature interactions were highly significant for all the characters studied.Item Glufosinate-tolerant cotton: tolerance and weed management(Texas Tech University, 1999-12) Blair, Lesli KristenField studies conducted in 1997 and 1998 examined plant growth and development, yield and fiber quality of glufosinate-tolerant cotton. Regardless of glufosinate application rate, number of applications, or cotton growth stage at application, no visual injury nor adverse effects on cotton development, yield or fiber quality were observed. Amaranthus palmer! and Proboscidea louisianica control in glufosinate-tolerant cotton using preplant incorporated, preemergence and postemergence-topical herbicide applications with and without cultivation was examined also. Amaranthus palmeri and Proboscidea louisianica was controlled at least 90% when trifluralin preplant incorporated followed by prometryn preemergence followed by glufosinate postemergence was applied. These weeds were controlled 0 to 100% following soil applied herbicides alone and 47 to 99% following glufosinate alone. This research indicated that the transformation events for glufosinate-tolerance in Gossypium hirsutum L. cv. 'Coker 312' were successful and the gene expressing glufosinate-tolerance was expressed throughout the growing season. In addition, Amaranthus palmeri and Proboscidea louisianica control was greater when glufosinate was used in combination with soil applied herbicides as opposed to glufosinate applied alone.Item Herbicide tolerance during seedling establishment in cool and warm season turfgrass(Texas Tech University, 1999-05) Sebastian, William BryantThe turfgrass industry contributes more than $6 billion to the economy of Texas each year (Lard et al., 1996). Not only is the economic contribution of the turfgrass industry vital to the State's economy, but the aesthetic value of turfgrass is important to the quality of life. West Texas is a transitional area where both cool season and warm season grasses are seeded to establish lawns, golf courses and athletic fields, as well as for erosion control (Beard, 1973). Seeding turfgrass is a popular and economical method used by professionals as well as homeowners. However, the high soil pH and the broad weed spectrum in this region requires tailoring herbicide recommendations based on both the species and the time of establishment. Limited information is available on using herbicides to enhance turfgrass establishment under the semi-arid environmental conditions of West Texas. Two field experiments were conducted in 1994 and 1995 at Lubbock, Texas, to determine turfgrass seedling tolerance to herbicides commonly used in established turfgrass. These studies were conducted to evaluate: 1) cool season turfgrass seedling tolerance to preemergence herbicides; 2) cool season turfgrass seedling tolerance to postemergence herbicides; 3) warm season turfgrass seedling tolerance to preemergence herbicides; and 4) warm season turfgrass seedling tolerance to postemergence herbicides. This information could be used to develop comprehensive weed management strategies for turfgrass establishment across the region.Item Impacts of water quality of plug production of gaillardia, salvia, and pepper(Texas Tech University, 1997-12) McGann, Linda S.The objectives of this study were to evaluate the effects of poor quality irrigation water fi-om two different water sources on the growth of Capsicum annuum fpepper), Gaillardia x grandiflora (gaillardia), and Salvia farinacea ("salvia) in plugs, to asses the feasibility of blending poor quality water with reverse osmosis treated water (RO) to remediate the potentially damaging effects of poor quality irrigation water on plant growth, and to empirically determine the most effective ratio of RO to poor quality water for each species. The study was a 2 x 5 factorial in a split plot design and was replicated over three runs. Two poor quality water sources (WS) were blended with RO in dilutions of 100 WS: 0 RO, 75 WS: 25 RO, 50 WS: 50 RO, 25 WS: 75 RO, and 0 WS: 100 RO. Seeds of each species were sown by hand into plug trays and measured volumes of each dilution were applied by hand. ANOVA analysis revealed that dilution of each water source significantly impacted dry weights for all three species. Pepper, a crop rated as moderately tolerant to soluble salts, generally produced more dry weight with 25 WS: 75 RO. However, visual evaluation scores for uniformity, quality, and salability of pepper revealed little difference between 0 WS: 100 RO, 25 WS: 75 RO, and 50 WS: 50 RO dilutions. Therefore, higher percentages of a poor quality water source and less RO may be tolerated in pepper plug production. Overall trends in gaillardia production revealed a trend for maximum dry weights with the 25 WS: 75 RO dilution. With few exceptions, the highest evaluation scores for uniformity, quality, and salability of gaillardia were with the 25 WS: 75 RO dilution. For salvia, a crop sensitive to soluble salts. 100% reverse osmosis treated irrigation water produced the highest dry weights with the best evaluation ratings for uniformity, quality, and salability.