This thesis covers the development of high-resolution model spectra of simple-stellar-populations (SSP) to be used in the measurement of the ages, metallicities and chemical abundances of unresolved extragalactic globular clusters (GCs). The models are compared to low- and high-resolution spectra of GCs in the Milky Way and M31 galaxies, whose properties are already known, to establish the effectiveness of both the SSP spectral grid and of the direct spectral fitting procedure employed in this work. The model SSP spectra were created using Dotter et al. (2007) isochrones, populated using the flux derived from a grid of stellar spectra, weighted by the Kroupa (2001) mass function. Models with varying mass loss from the red giant branch and varying numbers of He-burning stars were generated. The spectral grid currently covers a parameter range of 2 to 15 Gyrs in age, and -2.5 to 0 dex in [Fe/H] at an [alpha/Fe] of +0.4 dex. Metallicities derived for Milky Way GCs from Lick index comparisons to the model grid are in good agreement with values in the literature. The stellar spectral grid, from which the GC spectra are generated, has been created using ATLAS9 and SYNTHE. The spectra are at a resolution of R = 100,000 and cover a wavelength range from 3000 - 9000 Angstroms. Extensive work was undertaken in creating appropriate lists of atomic and molecular transition oscillator strength (log gf) values for this spectral grid. An automated program was created to alter the strengths of millions of atomic transition lines in the Kurucz atomic line lists to fit a model spectrum of appropriate parameters to that of the red-giant star Arcturus and to the Solar spectrum at shorter wavelengths (3000 - 3727 Angstroms). Comparisons to these observed spectra were made manually for several molecular lines and band-heads, and log gf values changed en-mass for all the lines of a given molecular species. The SSP spectra were compared to low-resolution spectra of Milky Way GCs. Integrated-light spectra of a large number of Galactic GCs were obtained from three sources: the Schiavon et al. (2005) Library of Integrated Spectra of Galactic Globular Clusters, taken using the Ritchey-Chretien spectrograph on the Blanco 4m telescope at Cerro Tololo Inter-American Observatory; spectra obtained through private communication with M. Bessell using the Double Beam Spectrograph on the 2.3m telescope at Siding Springs Observatory; and spectra obtained using the Robert Stobie Spectrograph on the 11m diameter Southern African Large Telescope. With resolutions of 1500 to 2800, abundances of individual elements could not be determined, but overall ages and metallicities were derived. The model spectra were fitted to the observed spectra using a Chi^2 minimisation procedure over large wavelength regions to fully utilise the information available in the spectra. Derived metallicity values were in agreement with literature values. However, age determinations were not consistent with those derived from photometric methods and had large associated uncertainties. The lack of age information in the spectra at such resolutions is a similar result to that found by other studies using the Schiavon data (eg. Mendel et al., 2007; Koleva et al., 2008). The SSP spectral grid was used to determine ages, metallicities and individual elemental abundances of three clusters (GCM06, GC5 and GC10) in the outer halo of M31. High-resolution spectra from Keck-HIRES were obtained through private communication with D. Forbes. Age and metallicity determinations were made simultaneously by fitting un-blended FeI lines and the H-beta and H-gamma lines. Diagnostic analysis (such as that done by Colucci et al., 2009) and simultaneous fitting of the FeI lines alone gave unrealistic age values that tended towards the lower limits (2 Gyrs) of the age grid. The age and metallicities derived in this work for these clusters are consistent with those found by Alves-Brito et al. (2009) using the same data. Abundances of a number of elements were derived from the high-resolution spectra. An overall enhancement of alpha-elements (from measurements of Ca, Si and Ti) was seen in all three clusters ([alpha/Fe] = 0.67 +/- 0.2, 0.63 +/- 0.2 and 0.5 +/- 0.2 dex for clusters GCM06, GC5 and GC10 respectively) which is greater than that found for other M31 GCs (Puzia et al., 2005; Colucci et al., 2009). A depletion in Mg compared to the other alpha-elements is seen, in accordance with patterns seen in both Milky Way and M31 GCs (Gratton et al., 2004; Colucci et al., 2009). All three clusters show varying levels of enhancements and depletion in the other measured elements (C, Sc, V, Cr, Mn, Ni, Ba), none of which follow the trends seen in Milky Way clusters. Comparisons to high-resolution spectra of Milky Way GCs, for which abundance ratios are known from the measurement of individual stars, need to be made to establish the accuracy of this elemental-abundance analysis. Overall, the system presented in this thesis is well designed to be used in the analysis of integrated-light spectra from distant, unresolved GCs. The uncertainties in the derived ages are still larger than desired, but the metallicity determination is very consistent when tested against clusters of known metallicities.

Light spectra distributions were measured in two different montane forests: temperate and tropical. Spectral light measurements were made in different sized canopy gaps in the conifer forest at H. J. Andrews Experimental Forest in Oregon, USA. Researchers at Oregon State University created these gaps of 20 m, 30 m, and 50 m in diameter. In the tropical cloud forest, spectral light measurements were made in two plots that were permanently established at La Mucuy Parque Nacional in Venezuela, in collaboration with researchers at Universidad de Los Andes. In both studies, spectra and distributions of physiologically active light were analyzed: red, far-red, R/FR ratio, and blue light.

The optimal combination of wavelengths of light (spectral quality) for single leaf photosynthesis has been well characterized, but spectral quality is not well characterized in whole plants in long-term studies. Here we report the effects of eight light spectra at two photosynthetic photon fluxes (200 and 500 µmol m-2 s-1) on dry mass, leaf area index and net assimilation of seven species in replicate 21-day studies. The combination of treatments allowed us to separately assess the effects of blue and green light fraction among species and PPF. At a PPF of 500, increasing blue light from 11 to 28 % significantly decreased dry mass in tomato, cucumber, and pepper, but there was no significant effect on soybean, lettuce and wheat. At a PPF of 200, dry mass significantly decreased only in tomato across the blue light range. Effects on leaf area paralleled effects on dry mass in all species at both PPFs, indicating that the effects of blue light on dry mass were mediated by changes in leaf area. Contrary to predictions of net assimilation based on blue light response of single leaves, there was no evidence of decreasing net assimilation with increasing blue light. In contrast to the significant effect of blue light dry mass and leaf area, increasing green light fraction from zero to 30 % resulted in few significant differences. Contrary to several reports on significant green light effects on growth (both increases and decreases), we found no consistent effect of green light among species on growth, leaf area or net assimilation. Collectively, these results indicate significant differences among species in sensitivity to blue light and less sensitivity to green light, and that the effect of blue light on dry mass is primarily determined by changes in leaf area.

<p>  </p> <p>With the rapid growth in population and urbanization, an increased supply of fresh, nutritious, and safe food in urban areas is required. Relying solely on conventional agriculture for food production can be risky due to climate change and decreasing natural resources (i.e., water, and arable land). Vertical farming (VF) involves growing food crops (primarily leafy greens and small-statured fruits) at multiple levels in controlled environments with less land and water inputs. However, high operational costs have resulted in low-profit margins in VF, which are challenging the economic sustainability of the VF industry. With the present VF technology, it may be difficult to significantly reduce the operational costs. Therefore, maximizing the wholesale value of produce, which is determined by the total yield and sale price per unit quantity (or crop value), is critical for increasing profits in VF. In this research, the overall goal is to increase lettuce growth, nutritional quality, and food safety by optimizing the light quality of light-emitting diodes (LED) in VF to increase the whole value of produce and thus increase the VF profits. The objectives of the research were to (i) study the independent and interactive effects of monochromatic wavebands of light from UV-A (365 nm) to far-red (750 nm) on lettuce growth and nutritional quality; (ii) identify the effects of substituting moderate proportions of UV-A and a high proportion of UV-A coupled with far-red light in growth lighting on lettuce growth and nutritional quality; (iii) study the effects of lettuce cultivars and UV LED light on the survival of <em>E. coli</em> O157:H7 on lettuce in VF production.</p> <p>In the first study, we investigated the effects of different wavebands of light ranging from UV-A (370 nm) to far-red (733 nm), both independently and in combination with commercial growth lighting on lettuce growth, incident light-use efficiency (LUEinc), and levels of phytochemicals. Results showed that the monochromatic wavebands 389 and 733 nm had positive interactions with the growth lighting on lettuce. In addition, results also indicated that UV-A light at a peak wavelength of 389 nm could potentially increase phytochemical concentrations. In the second study, the effects of 40% UV-A (UV 389 nm) and 60% UV-A (UV 389 nm) plus 10% far-red (FR 733 nm) light for growth light during the plant stationary growth stage on lettuce biomass and biosynthesis of phytochemicals were examined. Results showed that substituting UV-A for 40% growth lighting during the plant stationary growth stage for seven days resulted in significantly increased levels of beta-carotene and phylloquinone in lettuce while slightly lowering lettuce growth. And the addition of far-red light to UV-A did not result in the expected increase in vegetative growth, while the levels of phytochemicals were not affected. In the third study, we first investigated the effects of four lettuce cultivars, including oakleaf, romaine, butterhead, and leaf lettuce on the survival of <em>E. coli</em> O157:H7 gfp+. Results showed that leaf lettuce had the lowest while oakleaf and romaine had the highest concentrations of <em>E. coli</em> O157:H7 gfp+ when sampled on days 2 and 7 after the inoculation, and on day 7 after harvest and storage at 4 °C. Then we examined the feasibility of supplementing UV-A, UV A+B, and UV A+C during plant growth stages to reduce <em>E. coli</em> O157:H7 gfp+ contamination on lettuce. Our results indicated that only the UV A+C light at an intensity of 54.4 μmol·m-2·s-1 for 15 minutes per day after inoculation reduced <em>E. coli</em> O157:H7 gfp+ contamination by 0.33 log CFU·g-1 without affecting plant growth and levels of phytochemicals.</p> <p>The outcomes from our research suggested that the interactive effects of monochromatic wavebands should be considered in developing light recipes. In addition, VF growers who are interested in improving the nutritional phytochemical levels such as beta-carotene and phylloquinone in lettuce while maintaining growth should consider adding a moderate proportion (< 40%) of near-blue UV-A (i.e., 389 nm) radiation during the plant stationary growth phase to growth lighting. However, shorter wavelengths of UV-A radiation are not recommended due to their negative effects on plant growth and high economic cost. For growers who are at high risk of <em>E. coli</em> O157:H7 contamination, it is suggested that growing leaf lettuce and supplementation of UV A+C LED light during the plant-growth period should be considered to reduce the <em>E. coli</em> O157:H7 contamination levels.</p>