Theses and Dissertations

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Open Access
Lettuce irrigation scheduling using atmometers and computers
(Colorado State University. Libraries, 1980) McSay, Ann Emery, author; Moore, Frank D., III, advisor; Workman, Milton, committee member; Angleton, George, committee member; Danielson, Robert E., committee member
Linear relationships between soil matric potential (SMP) and evaporative power of the air (EPA) were developed in order to schedule irrigation of lettuce in arid or semi-arid regions. The irrigation scheduling model is based on the assumption that SMP i.e. soil moisture "need" is a function of stage of growth, EPA, soil texture and root zone recharge. Root zone recharge may be due to an irrigation which brings the effective root zone to field capacity or a rainfall event which accomplishes the same purpose. Four linear equations similar to stage of growth coefficients are modified by soil coefficients which account for variation in hydraulic conductivities due to soil texture. Information required on a daily basis for daily output consists of milliliters of water lost from standardized Bellani plant atmometers and inches of rainfall from 8 inch diameter USWS rain gauges. The irrigation scheduling output is in 2 forms. One is graphic. Graphic analysis allows the user to visualize the progression of SMP (converted from ƩEPA) as a function of days from last recharge. The observer simply compares this plotted line to the SMP horizontal (constant) line, one for each of the 4 growth stages. An obvious reminder of tardiness occurs after the two lines intersect. This graphic form of output results from a program written in assembly language for a programmable calculator. The other form of output is digital. A FORTRAN program for a large scale computer was written. The program fits, by the least squares method; linear, quadratic and cubic regression equations to ƩEPA versus days from last recharge data. The program solves each of the 3 polynomials for days to next recharge and converts the end of the interval to a calendar date. The user then selects the most imminent of the 3 predicted dates with the aid of associated coefficients of determination. A tardiness reminder is also provided. The program is used in the interactive mode and will permit rapid daily update and query of 400 different plantings. A method was developed to protect the Bellani plate assemblies from freezing.
Open Access
Cold hardiness and cryopreservation of small fruits
(Colorado State University. Libraries, 1981) Wu, Min-Tze, author; Hughes, Harrison G., advisor; Wallner, Stephen J., committee member; Stanwood, Phillip C., committee member
This study examined cold hardiness and the occurrence of deep supercooling in stem with an attached bud of 4 cv. of grape and 4 of raspberry. Cryoprotectants were also tested for their influence on cold hardiness of raspberry vegetative bud and stem. Differential thermal analysis (DTA) of 4 cv. of grapes, Vi tis species hybrids, 'Concord', 'Beta', ' Valient', and 'Rougeon' showed that the stem and bud pieces of all cv. deep supercool in winter. They all showed a bud exotherm at approximately -25 to -30°C, and a stem tissue exotherm at approximately -40°C. The temperature at which the bud exotherm occurs may be the killing point of the bud which in turn could lead to the death of the above-ground canes. Evidence of this was the observation of the death of 'Rougeon' buds, bud exotherm observed at approximately -20°C, during the winter of 1980-1981 when the lowest temperature was -2S.6°C. DTA profiles of stem with attached bud samples of the 4 raspberry cv., 'Heritage', Ruhus idaeus L., 'Black Hawk', R. occidentalis L., ' Amethyst', R. neglectus Peck, and 'Darrow', R. allegheniensis Porter, suggest that these do not deep supercool during winter. The mechanism of freezing resistance of these may be tolerance of extracellular freezing. Survival, indicated by sprouting, on January 30, 1981 showed that the LT50 (lethal temperature for at least 50% bud sprouting) was -55°C -50°C, and -45°C for 'Black Hawk', 'Amethyst', and 'Heritage', respectively. This supports the idea that at least these 3 cv. resist freezing by tolerance of extracellular freezing. Therefore minimum temperature may not be the major limiting factor in their northernly distribution. In descending order the observed degree of hardiness was 'Black Hawk', 'Amethyst', and 'Heritage'. Survival tests of 'Heritage' samples treated with cryoprotectants showed no benefit of cryoprotectants for enhancing the resistance of acclimated buds and stem to cold injury. However, there were some implications that cryoprotectants may enhance the resistance of nonacclimated samples to lower temperatures.
Open Access
Clinoptilolite, as a N, K, and Zn source for plants
(Colorado State University. Libraries, 1981) Lewis, Michael D., author; Moore, Frank Devitt, III, advisor; Goldsberry, Kenneth L., 1932-, committee member; Schmehl, W. R., committee member
Clinoptilolite was tested for its capacity to enhance availability of N, K, and Zn in the production of vegetable and flower species. Ammonium charged zeolite and mixtures of zeolite plus ammonium sulfate or urea were evaluated in a greenhouse experiment involving a medium (13% clay) textured alkaline soil with no drainage provided and a light (6% clay) textured soil which was leached 6 times during the course of the experiment. Controls were ammonium sulfate and urea. Banding provided the most effective method of application of zeolite compared to incorporation when radish, Raphanus sativus cv. Improved Scarlet Globe, was used as a test species. Banded ammonium charged zeolite increased radish growth in both medium and light textured soils. A decrease in N03-N loss occurred in the leached light soil. A physical mixture of uncharged zeolite and ammonium sulfate provided no increase in radish growth or reduction in leachate nitrate. Banding zeolite, in conjunction with urea, reduced growth suppression which occurred when only urea was added. Growth response of tomato Lycopersicon esculentum cv. Spring Giant, were evaluated under field conditions, using banded treatments of ammonium charged zeolite, ammonium charged zeolite plus ammonium sulfate and uncharged zeolite plus ammonium sulfate. No differences in plant growth occurred among zeolite and control treatments due to unavoidable additions of nitrate nitrogen in the irrigation water. Two greenhouse experiments were used to evaluate the influence of zeolite on vegetables, cut flowers and potted plant crops in two different media. Radish, Raphanus sativus cv. Improved Scarlet Globe responded positively to charged and naturally potassic zeolites, equaling growth obtained by the fertilizer injection method. Lettuce, Lactuca sativa cv. Grand Rapids Forcing (H-54); beans, Phaseolus vulgaris cv. Cherokee; chrysanthemums, Chrysanthemum morifolium cv. Bonnie Jean and snapdragon, Antirrhinum majus cv. Missouri growth was not positively affected by predesigned zeolite levels. Pot crops of poinsettia, Euphorbia pulcherrima cv. Dark Red Annette Hegg and Easter lily, Lilium longiflorum cv. Ace also were not responsive.
Open Access
Potato clone variation in blackspot susceptibility, extract darkening, and some chemical factors
(Colorado State University. Libraries, 1983) Thornton, Michael Kent, author; Workman, Milton, advisor
Six potato clones were analyzed with respect to tissue extract darkening, phenolic content, dry matter, and potassium content to determine if these properties were related to differences in blackspot susceptibility. Clones differed significantly in tissue extract darkening, dry matter and potassium content, but not phenolic content. Differences in tissue extract darkening were not significant when cell wall fragments were filtered. The potential of the tissue to darken, as determined by tissue extract darkening studies, was not consistently related to blackspot susceptibility. Clones with low tissue extract darkening darkened most in response to addition of substrate (catechol). Phenolic content (tyrosine and o-diphenols) were more consistently related to tissue extract darkening than to blackspot susceptibility. Dry matter content was most closely related to blackspot susceptibility, but did not account for all differences. Potassium content was not related to blackspot susceptibility. Changes in ascorbic acid content of bruised and nonbruised tissue of four potato clones were followed over time to determine if they were related to blackspot susceptibility. Ascorbic acid content of bruised and nonbruised tissue of three clones decreased over 24 hours. However, the ascorbic acid content of one clone increased during this same period. These changes were not related to blackspot susceptibility. Differences in ascorbic acid content between bruised and nonbruised tissue of the same tuber were significant in 3 of 4 clones but were not related to blackspot susceptibility.
Open Access
Carbon dioxide levels in the plant microenvironment as influenced by a poly-coated paper mulch
(Colorado State University. Libraries, 1983) Tarter, Cheryl K., author; Moore, Frank D., III, advisor; Wallner, Stephen J., committee member; Smith, D. D., committee member
Effectiveness of carbon dioxide (CO2) enrichment using a polyethylene coated black paper mulch, incorporated nitrogen and wheat straw particles, and field CO2 release was investigated. A mulch covering or mulch over incorporated plant residue, such as straw, has been suggested as a possible means of CO2 enrichment which results from trapping the CO2 evolved from the soil. This idea was tested using Great Lakes Mesa 659 lettuce seedlings in growth chambers and in an outdoor setting. Carbon dioxide concentrations at the base of the plants and at a 5 cm depth in the root zone were greater in mulched and mulched straw treatments. Non-mulched straw did not increase surface CO2 concentrations. Growth of mulched plants in the chambers was approximately 80% greater than that of non-mulched plants. Mulched plants in the outdoor study had a growth increase of about 13% when compared to non-mulched plants. Increases in growth of mulched plants were attributed to greater CO2 levels, since soil moisture levels and temperatures were similar in all treatments. Straw suppressed growth and would not be recommended as a CO2 source. Mulch applied over CO2 release lines in the field was found to be an effective means of CO2 enrichment of a lettuce canopy by creating a physical barrier to rapid air exchange, thereby concentrating released CO2 under the mulch. Mulch over a release line more than tripled CO2 concentrations near the soil surface when compared to CO2 release with no mulch covering or CO2 supplement. Significant enrichment levels were maintained to 25 cm above the soil surface on still days by means of a mulched CO2 release line. Subsurface CO2 concentrations were increased by the application of mulch and averaged 857 ppm which was considered non-phytotoxic. The effect on soil CO2 levels from the release line was negligible. Inconclusive results in plant response suggest further study is warranted.
Open Access
Leaching of salt from container media
(Colorado State University. Libraries, 1983) Kerr, Gregory P., author; Hanan, Joe J., advisor
The leaching of salt from container media was investigated by means of miscible displacement theory for a series of six peat-perlite-glass bead mixes and four other mixes. Columns were salinized with a 30 meq 1-1 solution of CaCl2 and NaCl, and allowed to equilibrate. Electrical conductivity of the effluent was monitored as columns were leached using 1 cm constant head with 2, 8 and 14 meq 1-1 solutions of CaCl2 and NaCl. A continuous series of physical properties were seen in the glass bead mixes, with efficiency of replacement of the soil solution by leaching solution increasing as glass bead content increased. Replacement efficiency had good correlations to physical properties of mixes, but insufficient data was available to relate this to particle size distribution. Leaching solution concentration did not influence replacement efficiency and, generally, after 1 to 1.5 container capacities of effluent, removal of original soil solution decreased substantially. A method is presented to determine the leaching requirement for potting mixes.
Open Access
Onion growth and water use patterns in relation to drought stress
(Colorado State University. Libraries, 1983) Bosley, Donald Bruce, author; Wallner, Stephen J., advisor; Moore, Frank D., III, advisor; Reid, C. P. P., committee member; Danielson, Robert E., committee member
Four distinct growth stages of storage onions were established using growth analysis techniques; stand establishment (0 - 4 leaves), leafing (4 - 8 leaves), bulbing (8 - 10 leaves), and sizing (less than 10 leaves. Visible developmental observations such as number of functional leaves were determined to be the best indicator of crop growth stage. Linear relationships between soil matric potential (SMP) and evaporative demand (ED) were developed for each of the latter three growth stages in order to determine proper irrigation timing. It was assumed that SMP i.e. soil moisture "need" is a function of stage of growth, EPA, soil texture and root zone recharge. It was determined that to limit SMP to no greater than -40 kilopascals (kPa), irrigation or a significant rainfall should occur at or before 789 ml of water are evaporated from a black Bellani plate atmometer during the leafing growth stage. In a like manner, soil recharge should occur at or before 340 ml are evaporated during the bulbing and sizing growth stages. Onions were stressed during the leafing, bulbing, and sizing growth stages by withholding irrigation until a soil matric potential of -70 kilopascals was reached. No significant differences were observed in either the growth pattern or final yield between each stress treatment and the unstressed control. Hydroponically grown onions were transplanted into containers located in a greenhouse so that roots were subjected to six different levels of polyethylene glycol (PEG) 3500 osmotic solutions for five weeks. Leaf, bulb, and root dry weights were found to be significantly reduced in the treatment of -274 kPa or more negative osmotic potential than treatments of -147 kPa or less negative potential. Root:shoot ratio was found to be significantly greater in only one instance. After three weeks of growth the highest stress level (-622 kPa) resulted in the largest root:shoot ratio. This observation was believed to result from aproportionately greater leaf tissue decline than root tissue decline in response to high osmotic stress.
Open Access
Cool season turfgrass quality as related to evapotranspiration and drought
(Colorado State University. Libraries, 1984) Minner, David Drew, author; Butler, Jackie D., advisor; Moore, Frank D., III, committee member; Wallner, Stephen J., committee member; Danielson, Robert E., committee member
Irrigation is required in semi-arid regions to produce acceptable turf (at least 70 percent live biomass). This study was conducted to provide turfgrass water management information. Irrigation amount and frequency to produce acceptable Kentucky bluegrass (Poa pratensis L.) or to insure recovery when water eventually became available was determined. Deficit irrigation effects were studied using sand filled weighing lysimeters. Grass watered at 100 percent irrigation every 2 days (maximum ET) used 4 to 8 percent more water than that irrigated every 7 days. Acceptable Kentucky bluegrass was produced when grass was watered every 2 days and ET was 77 percent of maximum. Lysimeter turf quality was acceptable when the average soil moisture tension was 0.9 to 1.5 bars. 'Merion' Kentucky bluegrass, grown in field plots on clay loam soil, was watered at 100, 75, 50, 25 and 10 percent every 2, 4, 7, or 14 days. Kentucky bluegrass appearance improved as water amounts increased and irrigation interval decreased. Average soil moisture tensions between 4.5 and 1.4 bars produced acceptable turf. Irrigation at 75 percent every two days provided acceptable turf during July and August, however, only 25 percent irrigation was needed during this time to provide acceptable turf after an irrigated recovery period in September. Four grasses were grown on sand in lysimeters to determine their water use. When soil moisture did not restrict ET, water use was greatest by tall fescue (Festuca arundinacea Schreb.) and lowest for fine fescue (Festuca sp. L.), while Kentucky bluegrass and perennial ryegrass (Lolium perenne L.) were intermediate in water use. These grasses provided acceptable turf during most of July and August with 75 percent irrigation. Drought tolerant cultivars of Kentucky bluegrass, perennial ryegrass and fine fescue were identified by withholding irrigation during two summers except for a recovery period in September. 'Majestic' and 'H-7' Kentucky bluegrass and 'Aristocrat', 'Bellatrix', 'Citation' and 'Yorktown' perennial ryegrass had the best drought tolerance. None of the fine fescues produced suitable turf under severe drought conditions.
Open Access
Studies of temperature stress in cultured pear cells
(Colorado State University. Libraries, 1984) Wu, Min-Tze, author; Wallner, Stephen J., advisor; Ross, Cleon, committee member; Stack, Stephen, committee member; Bedford, Joel S., committee member; Hughes, Harrison G., committee member
Studies were undertaken to examine the heat stress and freezing stress responses of cultured plant cells. Suspension- cultured pear (Pyrus communis cv. Bartlett} cells were used as the experimental materials. The response of pear cells to heat stress was studied using three viability tests: regrowth (culture growth during 10 days after stress); triphenyltetrazolium chloride reduction; and electrolyte leakage. Critical temperatures (those causing 50% injury} for a 20 minute exposure were 42°, 52°, and 56°C , respectively, for these viability tests. The measurements of direct response, i. e., TTC reduction and electrolyte leakage, were not adequate substitutes for regrowth tests in assessing heat injury to cultured plant cells. The pipetting of pear suspension cultures was followed by a substantial but transient decrease in heat sensitivity. During a culture cycle, pear cells were most sensitive to heat at around day three. The influence of these normal culture variables (handling and age) are potentially serious artefacts and must be well characterized in order to minimize systematic errors in measuring heat tolerance. Beyond this, they may provide clues concerning physiological factors governing the responses of cells to heat. Both elevated growth temperature and brief heat shock increased the heat tolerance of pear cells. Several features of heat acclimation induced by these two methods were compared. Based on these comparisons, it was concluded that heat acclimation in response to growth at 30°C and to heat shock occurred via different mechanisms. The effect of low temperature on heat tolerance and high temperature on freezing tolerance of pear cells was also examined. The heat acclimation induced by elevated growth temperature increased freezing tolerance, but cold acclimation did not increase heat tolerance. It seems likely that some component(s) of cold and heat acclimation may be the same. This indicates that studies of response to different stimuli may help in clarifying mechanisms of temperature acclimation. The only potential mechanism examined in this study was the role of extracellular polysaccharides in cell response to freezing stress. Extracellular macromolecules from non-acclimated cultures aggregated irreversibly during freezing, while those from acclimated cultures did not. The aggregation of polysaccharides may be related to the observation that macromolecules from a non-acclimated medium increased the freezing injury of pear cells. Analyses of polysaccharides from acclimated and non-acclimated cultures indicated that the polysaccharides were changed during cold acclimation.
Open Access
Cultural studies of greenhouse grown Eustoma grandiflorum
(Colorado State University. Libraries, 1984) Azrak, Mohamed F., author; Goldsberry, Kenneth L., advisor; Baker, Ralph, committee member; Workman, Milton, committee member
Change in photoperiod had no affect on flower initiation of Sakata F-1 hybrid E, grandiflorum; however, plant flower buds developed faster, had increased stem length, greater number of bud nodes, and more plant fresh and dry weight when exposed to day growing temperature and relative humidities of 22° C and 70%, compared to 17° C and 30-50% respectively. Sakata plants grown in volcanic scoria, gravel, and idealite had better growth and production than those in soil medium. The removal of terminal shoots at the fourth, fifth or sixth leaf pairs above the base, had no effect on growth, however, the removal of the growing tip only, reduced the flowering time by 10 days. The Weddle hybrid of E. grandiflorum was more productive and had larger stems than the Sakata hybrids. Both hybrids had two definite flowering cycles per year, one from May through June, and a second from August to mid-October. The vase life of both hybrids ranged from 8 to 18 days, but was not increased by preservative addition of 8-hydroxyquinoline citrate, (8-HQC), plus sugar. E. grandiflorum was attacked by red spider mite (Tetranychus urticae) and white fly (Trialeurades vaporariorurn) and was highly susceptible to Rhizoctonia solani and Fusarium spp.
Open Access
Drought stress by growth stage and onion plant growth
(Colorado State University. Libraries, 1984) Richwine, Paul Allen, author; Moore, Frank D., III, advisor; Danielson, Robert E., committee member; Wallner, Stephen J., committee member
Three distinct growth stages of the onion's vegetative development have been defined: early (73-101 days), mid (102-122 days), and late season (123-143 days). Two years of field experiments and a greenhouse study with onions examined the effects of drought stress applied during these stages. Influence of excessive nitrate salts was also investigated. Rootview boxes submerged in a furrow-irrigated onion field allowed for a continuous study of root, leaf, and bulb development. A drought stress of -100 kPa soil matric potential was imposed for three weeks during each growth stage. Soil matric potential of -55 kPa was used as a standard. Onion plants located in the greenhouse were hydroponically grown in cans containing half-strength Hoagland's solution. Polyethylene glycol (PEG 3500) was used as the osmotic potential modifier creating drought stresses of -100 kPa and -200 kPa which were applied for 3 weeks during each growth stage. Ammonium nitrate (NH4NO3) at levels of 153 and 202 ppm NO3-N provided the high nitrate source. Both field and greenhouse studies identified the mid-season growth stage as the most sensitive to drought stress equal to or greater than -100 kPa. Bulb, root, and top components were significantly reduced as compared with the no stress treatment. Drought stress of -100 kPa during the early season growth stage had no significant negative effect on onion growth, however, a drought stress of -200 kPa applied during the early season growth stage caused growth to be suppressed. Drought stress had no significant effect on onion growth when applied during the late season growth stage. There was no significant influence of high nitrate levels on onion top, bulb, or root growth.
Open Access
Interference of apple seedling growth by green foxtail
(Colorado State University. Libraries, 1984) Omezine, Abdessatar, author; Wallner, Stephen J., advisor; Zimdahl, Robert L., committee member; Rogoyski, Matthew, committee member
Because of the documented benefits of cover crops in orchards, the interactions of one potential candidate-green foxtail (Setaria viridis L . Beauv.)-with apple seedlings (Malus domestica L.) have been investigated. Two possible interference mechanisms have been studied under greenhouse conditions: competition and allelopathic effects of green foxtail on apple seedling growth. Inhibition of apple seedling growth by green foxtail was recorded only in interference experiments where competition for water or nutrients was a present factor. No inhibition was detected when competition was removed or minimized in a hydroponic system. The incorporation of green foxtail root debris into soil mixture did not result in inhibition of apple growth. Thus, competition for water was the most likely reason for inhibition of apple seedling growth by green foxtail. The presence of green foxtail did not affect dry matter distribution in apple seedlings when water and nutrients were equally available to both plants. Studies of allometric parameters anatomical indices suggested that green foxtail roots did not release any allelopathic chemicals. Green foxtail might be used as cover crop in apple orchards when competition for water and nutrients is minimized. Elimination of competition is a difficult and expensive task and is often impossible in the field. However, the reduction of competition can be made by using strip herbicidal treatment in the tree rows.
Open Access
Trichoderma, Truban@, Pythium, and lighting influence on carnation development and flowering
(Colorado State University. Libraries, 1985) Graper, David F., author; Hanan, Joe J., advisor; Goldsberry, Kenneth L., committee member; Baker, Ralph, committee member
Investigations were carried out on the merit of utilizing Trichoderma in the production of carnations. Two different strains of Trichoderma harzianum, T-12 and T-95 were used. The effectiveness of Trichoderma as a control agent against Pythium root rot was found to be small. Some alterations in carnation development were observed, but were insufficient to warrant recommending it use. Growth response as a consequence of Trichoderma were insignificant. If a soil-borne disease problem, such as Pythium root rot, does exist, Truban@ is recommended for control, as it was very effective in these experiments. Two experiments were conducted on photoperiodism and timing in the carnation. These were designed to determine if current carnation culture should be modified. Potential benefit was observed, for the grower, in the use of a long day treatment for an older crop of carnations, increasing production prior to a holiday demand period or a crop ' s removal from production. The use of a period of short days, prior to the long day period, was also investigated. Results were ambiguous, and no recommendations could be made.
Open Access
Effect of tissue culture propagation on phenotypic variation of eight potato cultivars
(Colorado State University. Libraries, 1985) Allen, Jim R., author; Knutson, Kenneth W., advisor; Ladd, Sheldon L., committee member; Harrison, Monty D., committee member; Workman, Milton, committee member
The effect of a rapid multiplication tissue culture propagation scheme on phenotypic variation of potato clones was studied. Mother stock consisted of eight virus-free commonly grown potato cultivars, along with field and mutant selections of Centennial Russet and Russet Burbank cultivars. These cultivars and selections were cultured via shoot-tip culture and propagated by nodal transfers. The experiments consisted of comparisons of plants propagated via nodal transfers for approximately one year with tuber propagated mother stock as the control. Also, the effects of different time periods in culture, cold storage and heat stress were studied. Tubers from first generation plants were harvested and replanted for second generation comparisons. The second generation comparisons provided the best analysis when all plants were grown from tubers. Much of the experimental error from juvenile growth characteristics of tissue culture plantlets was eliminated. Observations were taken on eighteen plant characters, such as pigment on nodes. Measurements were taken on fourteen plant characters, such as terminal leaf index. There were some instances where variable readings on pigment of some plant parts were found. These instances were few in relation to the size of the experiment and were most likely the result of environmental and physiological differences rather than genetic variation. Factors such as tuber weight and tuber dormancy that resulted in delayed emergence had more effect on plant variability than the tissue culture treatments. Repeated nodal transfers (up to one year), cold storage or heat stress did not induce phenotypic variation in these experiments.
Open Access
Evapotranspiration and water management of turf canopies in a semi-arid environment
(Colorado State University. Libraries, 1987) Fry, Jack Douglas, author; Butler, Jackie D., advisor; Wallner, Stephen J., committee member; Smith, D. D., committee member; Marlatt, William E., committee member; Moore, Frank D., III, committee member
Several investigations were undertaken to better define water requirements of turf canopies in an area of limited precipitation. Potential evapotranspiration (ET) (i.e., ET under conditions where soil water is not limiting) was determined using lysimeters in the field in three studies. When evaluated under putting green conditions, annual bluegrass (Poa annua L.) had a significantly lower water use rate (4.6 mm day-1) than creeping bentgrass (Agrostis palustris Huds.) (4.9 mm day-1) during the summer of 1986, but not 1985. Furthermore, both species had lower water use rates in 1986 when cut at 0.6 cm (4.6 mm day-1) compared to 1.2 cm (4.9 mm day- 1). Evapotranspiration rates of several turf weeds and groundcovers were also evaluated using lysimeters in the field. Results indicated that white clover (Trifolium repens L.), a C3 dicot, had the highest mean water use rate of all species (6.6 mm day-1). Lowest water use rates were seen with dichondra (Dichondra repens J.R. Forst. and G. Forst.), a C4 dicot, and barnyard grass [Echinochloa crusgalli (L.) Beauv.], a c. monocot (4.2 and 4.4 mm day-1, respectively). 'Merion' Kentucky bluegrass (Poa pratensis L.), yellow foxtail [Setaria glauca (L.) Beauv.], and crabgrass [Digitaria ischaemum (Schreb.) Muhl.] exhibited intermediate ET rates. Potential ET rates of 'Merion' Kentucky bluegrass and 'Rebel' tall fescue (Festuca arundinacea Schreb.) were determined during establishment using lysimeters. Over two summers, the mean ET rate for these two species was 5.2 and 5.3 mm day-1, respectively. In 1985, tall fescue began using significantly more water than Kentucky bluegrass twenty days after seeding. Tall fescue, irrigated at 50 and 100% of potential ET of a mature turf, did not achieve satisfactory establishment at the former irrigation level. Preplant soil incorporation of a hydrophilic polymer was also evaluated in greenhouse and field studies for effectiveness in reducing tall fescue drought stress during establishment. When applied at reasonable rates, the polymer was ineffective in enhancing tall fescue establishment. Mature 'Reliant' hard fescue [Festuca ovina var. duriuscula (L.) Koch.] and 'Rebel' tall fescue were evaluated in field plots under irrigation levels of 50, 75, and 100% of potential ET, applied on 2, 4, 7, or 14 day intervals. Hard fescue had the best quality when irrigated at 75 or 100% of potential ET on 2 or 4 day intervals. Acceptable tall fescue quality resulted when turf was watered once weekly at 50% of potential ET. These studies have better defined water management requirements and conservation strategies for turf canopies where water supplies are often limited.
Open Access
Air and medium temperatures for Alstroemeria 'Atlas' and 'Monika'
(Colorado State University. Libraries, 1987) Keil, Linda Sue, author; Goldsberry, Kenneth L., advisor; Hanan, Joe J., committee member; Ross, Cleon, committee member
Alstroemeria cultivars 'Atlas' and 'Monika' were grown in four 25.4 m2 fiberglass-covered greenhouse compartments at the W.D. Holley Plant Environmental Research Center, Colorado State University. Each compartment contained two raised redwood benches subdivided into four 75 x 105 cm plots with buffer zones at either end of the bench, Individual benches had replicated plots of cooled and noncooled substrate treatments. The cooled plots contained seven loops of .625 cm OD Biotherm tubing buried 15 cm beneath the pea gravel surface. A thermostatically-controlled cooling system supplied cold water, upon demand, in an attempt to maintain a medium temperature of 11°C. Compartments were heated to 10° to 11°C during night periods, and the following daytime temperature regimes were established: Compartment A, 14° to 20°C; Compartment B, 20° to 26°C; Compartment C, 23° to 28°C; and Compartment D, 17° to 23°C. A night break was provided with incandescent lamps when natural daylengths were less than 12 hours. Developing cultivar rhizomes were transferred from 10 cm pots to the bench plots on November 18, 1985. The first flower data were taken on February 10, 1986, then collected every other day and summarized weekly during the next 52 weeks. Parameters measured included: stem length, flower grade, and total production. Data were analyzed as a split-split plot design with media treatments randomized within each pair of plots. Total flower production of 'Atlas' in all compartments was 1.6 times as great as 'Monika'. Significantly larger numbers of flower stems were produced in the cooled substrate of compartments A and D. The results provided evidence that the greatest production of 'Atlas' and 'Monika' occurred with average daytime temperatures of 20°C combined with an average medium temperature of 12°C to 14°C. Consequently, the cooled medium treatment coupled with cooler air temperatures allowed production to continue virtually year-round. The warmer daytime temperatures of compartments B and C increased the flower quality. However, the higher production in compartments A and D far outweighed the advantage that warmer temperatures contributed to quality. The flower quality of 'Monika' was considerably less than that of 'Atlas' in all temperature treatments. Warmer daytime temperatures also contributed to longer stems. 'Atlas' and 'Monika' stems from compartment C averaged a maximum of 13 cm longer than those from the remaining compartments. 'Atlas' stems were significantly longer than those of 'Monika' in all compartments. A five week sub-trial was conducted to determine air temperature effects on Alstroemeria inflorescence characteristics. Parameters measured included: number of cymes per stem, cyme length, stem thickness, and number of buds per cyme. Data were analyzed as a split plot design. No significant differences were observed for number of cymes per stem and stem thickness between compartments, although 'Atlas' had thicker stems than 'Monika'. A significant trend toward increasing cyme length with increasing daytime temperature was evident in both cultivars. Significantly more buds were produced on stems of both cultivars in compartment D (i.e., 20°C average day air temperature) compared to all other compartments.
Open Access
Micropropagation techniques as tools for studying plant growth, tuberization and sprouting of potatoes
(Colorado State University. Libraries, 1988) Alsadon, Abdulla A., author; Knutson, Kenneth W., advisor; Hanan, Joe J., committee member; Fenwick, Jack R., committee member; Wallner, Stephen J., committee member; Moore, Frank D., III, committee member
Several investigations were undertaken to determine if micropropagated potato cultivars of different maturity classes performed under field conditions in a manner similar to that reported for seed tuber propagated plants of the same cultivars. Plant growth analysis was carried out with special emphasis using Richards' function for evaluating growth attributes such as plant height, leaf area, and derived growth quantities such as RGR. Early, medium, and late maturing potato cultivars were grown under field, greenhouse and vitro conditions to measure tuber yields. Two sprouting indices (sprouting rate index, and sprouting ratio index) were developed and used to quantify the sprouting characteristics of field, greenhouse, and in vitro produced tubers. Storage temperatures were 5, 10, and 20° C. The combined field data of 1986 and 1987 indicated that plant growth, development and tuber yield were in general agreement to that of seed tuber propagated plants. The derived growth quantities (i.e. RSER, RLAER, RTGR, and RUGR) provided a useful way of comparing cultivar response and explained how the overall growth and development can be understood. Significant correlations were reported between selected yield characteristics of field grown, greenhouse grown and in vitro produced tubers. Both Kennebec and Spunta had the highest yield under field, greenhouse, and in vitro conditions. Russet Burbank and Norland had the lowest yield while Desiree and Norgold Russet had an intermediate response. Both sprouting indices incorporate the influence of factors such as cultivar, temperature and tuber size. Both indices also indicate that earliest sprouting occurred in Norland followed by Desiree and Russet Burbank. Field grown, and greenhouse grown tubers exhibited earlier sprouting than] in vitro produced tubers. Overall, these investigations illustrate the potential value of micropropagation methods in predicting yielding ability and sprouting characteristics of potato cultivars.
Open Access
Cold hardiness and water content during deacclimation of grapevine bud and cane tissue
(Colorado State University. Libraries, 1988) Hamman, Richard A., Jr., author
Computer assisted thermal analysis was used to measure deep supercooling in dormant bud and cane tissue of Vitis vinifera L. cv. 'Merlot' during a five week deacclimation time period. The temperature of the Low Temperature Exotherm (LTE), an indicator of hardiness, of both cane (internode) and primary bud tissue responded to weekly increases in air temperatures with bud tissue responding faster than cane tissue. Bud tissue from pruned and unpruned canes retained the capacity to supercool until early bud swell 18 April 1987, when the mean LTE temperature of -9.8°C became obscured by High Temperature Exotherms (HTEs) occurring between -5 and -8°C. Cane tissue had lower LTEs than bud tissue on each date and at each position. Cane positions nearest the trunk, whether canes were pruned or unpruned, were found to be slightly hardier than those more distally oriented, which was not observed with buds. Pruning treatments did not influence the loss of hardiness in either bud or cane tissue. Water content of canes was more affected by all three factors (date, position, and pruning) than was hardiness. Bud water content was only affected by date, and was lower than cane water content for every date and each position throughout the study. Canes increased in water content with each more distal position. Pruning slowed the rate of cane hydration during the week it was most rapid, especially at the most distal position. Observations during the most pertinent three weeks of this study indicate that cane tissue hydrates rapidly but dehardens only slowly, while buds deharden more quickly yet have only a small increase in bulk water content. The main effect of pruning was on cane water content.
Open Access
Role of the cell wall in freezing tolerance of plants
(Colorado State University. Libraries, 1989) Weiser, Russell L., author; Wallner, Stephen J., advisor; Ross, Cleon, committee member; Stanwood, Phillip, committee member; Towill, Leigh E., committee member
Acoustic emissions were observed during freezing of woody supercooling (Fraxinus americana, Malus x 'Dolgo', Pyrus communis, and Fraxinus pennsylvanica) and nonsupercooling species (Pinus edulis, Pinus ponderosa, and Cornus sericea). Observations of hundreds of samples revealed several consistent responses. Acoustic emissions were in no case associated with the high temperature exotherm (extracellular freezing) and are therefore not a result of ice formation per se. The emissions just preceded the low temperature exotherm in supercooling species and stopped at the same time intracellular freezing was completed (near -40°C). Although some acoustic emissions occurred during freezing of non-supercooling species the quantity was considerably less. The concept of negative turgor as a cause of cavitation of cellular water, detected as acoustic emissions, is proposed to explain these observations. When etiolated pea (Pisum sativum) cv. Alaska) seedlings were acclimated at 2°C, changes in several cell wall properties were observed. The weight of the cell wall increased by 40% and arabinosyl content doubled while other glycosyl residues and cellulose remained essentially unchanged. The level of hydroxyproline increased by 80%. Arabinose and especially hydroxyproline are indicators of the glycoprotein extensin. The increase in these components translates to a significant increase in this cell wall structural protein. Measurement of the mRNA for extensin by Northern blot analysis revealed a more than 3-fold increase in the total of all transcripts found (6.0, 4.5, 3.5, 2.6, 2.3, and 1.5 kilobases), while increases in certain transcripts (6.0, 2.6, and 1.5 kilobases) appeared to be especially promoted. The possible structural role of extensin in freezing tolerance and its regulation at the gene level are examined. Pea epicotyls grown in osmotic stress up to -1.15 MPa imposed by growth in polyethylene glycol solutions were visibly stunted and became 10°C more tolerant to freezing. During this period extensin level in the cell wall increased significantly. When water was withheld from etiolated seedlings the water potential dropped from -0.42 to -1.14 MPa and was coincident with a 7°C increase in freezing tolerance, a 44% increase in cell wall extensin, and a dramatic drop in extensin mRNA. In both water stress treatments there was no specific increase in extensin mRNA transcripts identified at 6.0, 4.5, 3.5, 2.6, 2.3, 1.8, and 1.5 kilobases. Pea epicotyls that were either wounded or exposed to ethylene showed no clear change in freezing tolerance, or total extensin mRNA, but had a significant rise in cell wall extensin. The same mRNA transcripts were found with the addition of a band at 1.2 kilobases. Interestingly, the 1.5 kilobase transcript was upregulated significantly more than other bands in both wounded and ethylene treated peas.
Open Access
CO₂ profiles in the field and response to enriched atmospheres using strawberry
(Colorado State University. Libraries, 1989) Cahn, Helen K., author