Polydimethylsiloxane (PDMS) microfluidic channels, fabricated using low cost and simple soft lithography methods, conventionally have rectangular cross-sections. Despite being often used for organs-on-a-chip and cardiovascular research, these devices do not mimic the circular cross-sections of blood vessels in the human body, creating potential inaccuracies in observed flow conditions and cell behaviours. The purpose of this thesis is to (i) compare and optimize fabrication techniques for microchannels with circular cross-sections, (ii) assess biocompatibility of different surface functionalization approaches for Human Umbilical Vein Endothelial Cell (HUVEC) adhesion and growth, (iii) culture HUVECs within circular microchannels to mimic blood vessel features, and (iv) compare gene expression of HUVECs cultured in 3D circular microchannels to those cultured on 2D surfaces. We show that wire molding is superior to the gas stream technique for producing circular cross-section microchannels with high aspect ratios, circularity, and channel geometry precision. Fibronectin (FN) and polydopamine (PD) surface coatings on PDMS, as well as alternative collagen substrates, were tested for biocompatibility with HUVECs in 2D cultures; fibronectin coated PDMS (PDMS-FN) substrates facilitated cell attachment, spreading and growth. We demonstrate the capability of growing HUVECs on the inner surface of circular PDMS microchannels created using the wire-mold method and treated with fibronectin. A syringe pump was used to induce shear stress on the HUVECs grown in circular microchannels. Relative to static growth conditions, longer cell culture growth periods were more feasible under flow and altered cell morphology was observed. Finally, Microarray analysis revealed significantly different gene expression profiles for HUVECs cultured within PDMS-FN circular cross-section microchannels as compared to HUVECs cultured on PDMS-FN in a 2D environment, thereby highlighting the critical importance of in vitro conditions for mimicking the in vivo reality.

Seeding rate in hard red spring wheat (HRSW) (Triticum aestivum L.) production impacts input cost and grain yield. Predicting the optimal seeding rate (OSR) for HRSW cultivars can aid growers and eliminate the need for costly seeding rate research. Research was conducted to determine the OSR of newer HRSW cultivars (released in 2013 or later) in diverse environments. Nine cultivars with diverse genetic and phenotypic characteristics were evaluated at four seeding rates in 11 environments throughout the northern Great Plains region in 2017-2018. Results from ANOVA indicated environment and cultivar were more important than seeding rate in determining grain yield. Though there was no environment x seeding rate interaction (P=0.37), OSR varied among cultivar within each environment. Cultivar x environment interactions were further explored with the objective of developing a decision support system (DSS) to aid growers in determining the OSR for the cultivar they select, and for the environment in which it is sown. Data from seeding rate trials conducted in ND and MN from 2013-2015 were also used. A novel method for characterizing cultivar for tillering capacity was developed and proposed as a source for information on tillering to be used in statistical modelling. A 10-fold repeated cross-validation of the seeding rate data was analyzed by 10 statistical learning algorithms to determine a model for predicting OSR of newer cultivars. Models were similar in prediction accuracy (P=0.10). The decision tree model was considered the most reliable as bias was minimized by pruning methods, and model variance was acceptable for OSR predictions (RMSE=1.24). Findings from this model were used to develop the grower DSS for determining OSR dependent on cultivar straw strength, tillering capacity, and yield of the environment. Recommendations for OSR ranged from 3.1 to 4.5 million seeds ha-1. Growers can benefit from using this DSS by sowing at OSR relative to their average yields; especially when seeding new HRSW cultivars.

Grain sorghum [Sorghum bicolor (L.) Moench] varieties fail to reach maturity in North Dakota’s short and cool growing season. The study objective was to evaluate seeding date and white grain sorghum genotypes. A randomized complete block design study was conducted at Carrington, Oakes, and Prosper, ND, in 2018 and 2019. Genotypes included two commercial hybrids and four open-pollinated genotypes. Reaching heading and anthesis, hybrids required more heat units (GDDs), compared with the open-pollinated genotypes. Highest grain yield was obtained from the first and second seeding dates. Earlier-maturing open-pollinated genotypes maintained yield across seeding dates, whereas yield was reduced at later dates for the longer maturity hybrids. Hybrids produced the highest number of kernels per panicle at the first seeding date with fewer seeds at each successive seeding date. Although the open-pollinated genotypes out-yielded the hybrids at later seeding dates, the risk of lodging is too great to recommend their commercialization.

Planting date (PD), seeding rate (SR), genotype, and row spacing (RS) influence hard red spring wheat (HRSW, Triticum aestivum L. emend. Thell.) and soybean [Glycine max (L.) Merr.] yield. Evaluating HRSW economic optimum seeding rates (EOSR) is needed as modern hybrids may improve performance and have different SR requirements than cultivars. Two cultivars and five hybrids were evaluated in five North Dakota environments at two PDs and five SRs ranging from 2.22-5.19 million live seeds ha-1 in 2019-2020. Planting date, SR, and genotypes have unique yield responses across environments. Hybrid yield was the most associated with kernels spike-1 (r=0.17 to 0.43). The best hybrid yielded greater than cultivars in three environments. The EOSR ranged from 4.08-4.15 and 3.67-3.85 million seeds ha-1 for cultivars and hybrids, respectively. Hybrids are economical if seed prices are within $0.18 kg-1 of cultivars. In soybean, individual and synergistic effects of PD, SR, genotype relative maturity (RM), and RS on seed yield and agronomic characteristics, and how well canopy measurements can predict seed yield in North Dakota were investigated. Early and late PD, early and late RM, and two SRs (457 000 and 408 000 seed ha-1) were evaluated in 14 environments and two RS (30.5 and 61 cm) were included in four environments in 2019-2020. Individual factors resulted in 245 and 189 kg ha-1 more yield for early PD and late RM, respectively. The improved treatment of early PD, late RM, and high SR factors had 16% yield and $140 ha-1 more partial profit greater than the control. When including RS, 30.5 cm RS had 7% more yield than 61 cm RS. Adding 30.5 cm RS to the improved treatment in four environments resulted in 26% yield and $291 ha-1 more partial net profit compared to the control. A normalized difference vegetative index (NDVI) at R5 was the single best yield predictor, and stepwise regression using canopy measurements explained 69% of yield variation. North Dakota farmers are recommended to combine early PDs, late RM cultivars, 457 000 seed ha-1 SR, and 30.5 cm RS to improve soybean yield and profit compared to current management trends.

Dormant bermudagrass (Cynodon dactylon) fairways become matted down and thinned out from winter traffic. This appears to be more of a problem on the coarser textured, winter hardy, improved varieties (e.g., 'Midiron' and 'Vamont') typically used in the colder regions of the upper transition zone. Winter overseeding with cool-season species can improve dormant bermudagrass winter and spring quality. However, bermudagrass persistence can decline in golf course fairways overseeded with ryegrasses (Lolium sp.) for winter quality if ryegrasses persist due to cool spring temperatures, use of persistent ryegrass varieties, and management practices that favor ryegrasses over bermudagrass. Winter overseeding practices that facilitate a reliable transition from overseeded species to bermudagrass would enable transition zone golf courses to overseed bermudagrass fairways for winter-spring quality while allowing the bermudagrass turf to persist without excessive competition from cool-season overseeded species. Studies were conducted to determine the effects of perennial ryegrass (L. perenne) and annual ryegrass (L. multiflorum) seeding rates on winter-spring quality and subsequent transition to bermudagrass in two transition zone locations. Studies were also conducted to determine the potential influence trinexapac-ethyl (TE), a plant growth regulator used by many professional turfgrass managers to suppress foliar growth, has on encouraging overseeded species to transition to bermudagrass. These studies demonstrated that higher overseeding rates (448 and 896 kg ha-1) can provide greater winter-spring quality but do not enhance transition to bermudagrass over lower overseeding rates (224 kg ha-1). This was especially evident in cooler transition zone climate, where higher overseeding rates delayed transition to bermudagrass. Annual ryegrass transitioned to bermudagrass better than perennial ryegrass, but the overseeded winter-spring quality of annual ryegrass was unacceptable. Perennial ryegrass varieties differed in transition. Some perennial ryegrass varieties were too persistent to fully transition to bermudagrass even with the onset of summer temperatures. Intermediate ryegrasses (L. multiflorum x L. perenne) appeared to be promising alternatives to overseeding perennial ryegrass in areas of the transition zone where summer reliance on bermudagrass turf is strongly preferred. Trinexapac-ethyl, when applied to overseeded perennial ryegrasses, did not enhance overseeded ryegrass transition to bermudagrass. Spring TE applications to overseeded perennial ryegrasses were found to reduce or delay their transition to bermudagrass. / Master of Science

The original purpose of this study was to examine the influences of ecological site, seeding method and planting season on rangeland seeding success within the Tooele Fire Rehabilitation Project (TFRP) in northwestern Utah. The major objective of the TFRP, designed by the USDI Bureau of Land Management, was to establish a permanent cover of 'Nordan' crested wheatgrass (Aqropyron desertorum (Fischer ex Link) Schultes), 'Luna' pubescent wheat grass (Thinopyrum intermedium ssp. barbulatum (Schur) Barkw. and D. R. Dewey) and 'Al kar' tall wheatqrass (Thinopyrum ponticum (Podp.) Barkw. and D. R. Dewey) on approximately 20,000 ha of rangeland burned by a wildfire in July 1983. Thirteen combinations of site, method and planting season were identified within the study area; each was treated as an experimental unit. There were no significant differences (Pi0.05) in seedling densities between these treatment combinations. Means ranged from O to 1.9 seedlings/m2. There was significant variation (Pi0.05) among seedling densities within each treatment combination. Because of low seedling densities and non-uniform seedling establishment patterns, seedings within the study area were failures. Study effort was redirected to identify the causes of seeding failure. viii Among planting seasons and seeding methods, spring plantings and broadcast seeding contributed to failure. Most sites within the study area were suitable for seeding, with the exception of desert shallow loam. This site should not have been seeded because of steep topography and shallow soil. Planting during spring, broadcast seeding and the seeding of low potential sites explained only localized failure, however. The absence of crested wheatgrass seedlings within the study area was a major factor contributing to failure. Only two crested wheatgrass plants were found on a total of 195 permanently established transects. Of the three species seeded, crested wheatgrass was the best adapted to site conditions. Seeding technique was considered the most important factor causing failure. Contract workers on the project had no rangeland seeding experience. Drills were not properly equipped to control seed placement at the proper soil depth. Seeding was done during periods when site conditions were unfavorable. There was no evidence suggesting weather, grasshopper damage or cheatgrass competition caused failure.

Seeding deteriorated range lands efficiently and economically has become one of the most promising means of improving the agricultural economy of the western range states. By providing the most rapid means of increasing the quantity and improving the quality of forage for livestock, and aiding in the prevention of soil erosion, artificial seeding contributes directly to the stability of agriculture.

In growing alfalfa it is important to obtain a good initial stand. However, it is difficult to predict the exact amount of seed necessary to insure a good stand.

Pastures in the Intermountain Western United States mainly consist of cool-season grasses which lack production without supplemental nitrogen. Legumes provide nitrogen at reduced cost compared to nitrogen fertilizer. There is a need for proven methods of inter-seeding legumes into existing cool-season grass pastures as well as knowledge of how animals prefer legumes to grasses and how the nutritive value of forages change throughout the growing season. This research provides a resource for effective integration of legumes into pastures of the Intermountain West. Alfalfa, birdsfoot trefoil, and cicer milkvetch were inter-seeded into existing cool-season grass pastures following pretreatments of light tillage, mowing and glyphosate. Early spring and fall inter-seeding was unsuccessful, while late spring was moderately successful with overall alfalfa frequency of 30% after a year. Summer inter-seeding was the most successful with birdsfoot trefoil, alfalfa, and cicer milkvetch frequency of 42, 32, and 22%, respectively. In the animal preference study, when compared to tall fescue, birdsfoot trefoil was always utilized more.In most observations birdsfoot trefoil utilization was higher than orchard grass. While in all comparisons with meadow bromegrass there was no difference in utilization. During early growth, perennial ryegrass utilization was higher than birdsfoot trefoil utilization, but no difference in utilization was detected in later observations. Overall, birdsfoot trefoil was utilized 73% overall while grass utilization was 74, 67, 64, and 53% for perennial ryegrass, meadow bromegrass, orchardgrass and tall fescue, respectively. The interaction of growth stage and time of season on the nutritive value of alfalfa, birdsfoot trefoil, cicer milkvetch, orchardgrass, perennial ryegrass and tall fescue was determined. In the spring to early summer, legume nutritive value decreased rapidly with maturity, in midsummer the nutritive value decreased slowly with maturity, while in late summer the nutritive value remained stable. In the spring, grass nutritive value decreased rapidly, while in mid to late summer all grass regrowth was vegetative and the nutritive value remained stable. By inter-seeding in the summer, effectively managing mixed pastures, and utilizing forage at its highest nutritive value, legumes can benefit the pastures of the Intermountain West.

Rehabilitation of deteriorated and abused range lands is being accomplished with greater success each year by the aid of better methods of seeding which include seedbed preparation, intensities of seeding, implements for planting and improvised methods of eliminating competition. Much more information is needed however in order to recommend suitable methods and species for seeding various vegetation types and genes with reasonable reliability. Throughout the arid and semi-arid range lands, moisture is the principal factor limiting satisfactory seedling establishment. Special attention should therefore be given to more efficient utilization of the moisture supply. Closely related species of species with similar growth characteristics are said to compete for more water, for space and for nutrients; therefore, studies dealing with the effect of spacing and intensity of seeding upon seedling establishment are of paramount importance.