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Gregory D. Goins, Neil C. Yorio, and Lynn V. Lewis

Various electric lamp sources have been proposed for growing plants in controlled environments. Although it is desirable for any light source to provide as much photosynthetically active radiation (PAR) as possible, light spectral quality is critical in regard to plant development and morphology. Light-emitting diodes (LEDs) and microwave lamps are promising light sources that have appealing features for applications in controlled environments. Light-emitting diodes can illuminate a narrow spectrum of light, which corresponds with absorption regions of chlorophyll. The sulfur-microwave lamp uses microwave energy to excite sulfur and argon, which produces a bright, continuous broad-spectrum white light. Compared to conventional broad-spectrum sources, the microwave lamp has higher electrical efficiency, and produces limited ultraviolet and infrared radiation. Experiments were conducted with spinach to test the feasibility of using LEDs and microwave lamps for spinach production in controlled environments. Growth and development comparisons were made during 28-day growth cycles with spinach grown under LED (at various red wavelengths), microwave, cool-white fluorescent, or high-pressure sodium lamps. Plant harvests were conducted at 14, 21, and 28 days after planting. At each harvest under all broad-spectrum light sources, spinach leaf growth and photosynthetic responses were similar. Major differences were observed in terms of specific leaf area and weight between spinach plants grown under 700 and 725 nm LEDs as compared to plants grown under shorter red wavelengths.

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Megh Singh, Mayank Malik, Analiza H.M. Ramirez, and Amit J. Jhala

to herbicide selection and application rates because the area around the tree is more exposed to sunlight and have greater weed pressure compared with older trees ( Futch and Singh, 2000 ). Because of its broad weed spectrum, relatively low cost, and

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Charles J. Wasonga, Marcial A. Pastor-Corrales, Timothy G. Porch, and Phillip D. Griffiths

Common bean rust disease (caused by Uromyces appendiculatus) and high temperatures (heat stress) limit snap bean (Phaseolus vulgaris) production in many tropical and temperate regions. We have developed snap bean lines combining broad-spectrum rust resistance with heat tolerance for tropical agroecosystems. Eight breeding populations were developed by hybridizing BelJersey-RR-15 and BelFla-RR-1 (each possessing the Ur-4 and Ur-11 rust resistance genes) and the heat-tolerant snap bean breeding lines HT601, HT603, HT608, and HT611. F2–F4 generations of the populations were evaluated under greenhouse conditions and selected for heat tolerance while simultaneously selecting for the rust resistance genes Ur-4 and Ur-11. Three heat-tolerant F5 lines, which were homozygous for Ur-4 and Ur-11 genes, were selected together with a rust-resistant but heat-sensitive control. These and 12 cultivars adapted to different geographical regions were evaluated for their reaction to rust and yield at six contrasting field sites in eastern Africa and their response to high temperature verified in Puerto Rico. Rust incidence and severity was high at three of the trial sites in eastern Africa. Two of the 12 cultivars were resistant to rust at most of these sites, and three of the four breeding lines were resistant at all sites. The Ur-11 gene effectively conferred rust resistance at all sites. Yield in Puerto Rico was strongly correlated (R 2 = 0.71, P < 0.001) with that of the hottest site in eastern Africa, highlighting the similarity in genotypic response to high temperatures at the two distinct sites. The newly developed rust-resistant and heat-tolerant breeding lines showed stable yield at the eastern Africa sites with contrasting mean temperatures compared with the cultivars presently grown in the region. Two of these lines, HT1 and HT2, were confirmed to be homozygous for Ur-4 and Ur-11 and with high heat tolerance under both greenhouse and field environments. This research validates the effectiveness of targeted rust resistance gene combinations for tropical environments and the effective selection of high temperature tolerance traits correlating across multiple environments. The breeding lines HT1 and HT2 developed in this research could be used to improve snap beans for the tropics and other environments with similar constraints.

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Shih-Wei Kong, Hsin-Ying Chung, Ming-Yi Chang, and Wei Fang

. Understanding the correlation between light quality and the plant growth will be advantageous to plant cultivation and the development of optimum light spectrum in the future. Materials and Methods Experiment equipment. There were six light spectra used in this

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Isidro Morales, Gabino Alberto Martínez-Gutiérrez, Cirenio Escamirosa-Tinoco, Cinthia Nájera, Tatiana Pagan Loeiro da Cunha-Chiamolera, and Miguel Urrestarazu

spectrum was also measured ( Fig. 2 ), resulting in an average of three measurements made under the net at a 20-cm distance with a UPRtek MK350S LED Meter (Miaoli, Taiwan). A HD 2302.0 photometer (Delta OHM ® , Veneto, Italy) was used to quantitatively

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Dave Hawley, Thomas Graham, Michael Stasiak, and Mike Dixon

(THC) and cannabidiol (CBD), respectively. Perhaps by supplementing additional light, particularly a spectrum relatively rich in green light that is normally absorbed by some terpenes ( Miller et al., 1935 ; Zur et al., 2000 ), the plants up

Open access

Alexandra Boini, Enrico Muzzi, Aude Tixier, Maciej Zwieniecki, Luigi Manfrini, and Luca Corelli Grappadelli

, 2008 ) and negative impacts of artificial shading on flower bud weight were found in Japanese pear during flower bud formation ( Ito et al., 2003 ). There appears to be no information about the effect of light spectrum during dormancy in orchard systems

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Thitipat Weeplian, Tsair-Bor Yen, and Yunn-Shy Ho

environmental factor that affects plant survival, growth, and reproduction and also influences the metabolism of phytochemicals in plants ( Li and Kubota, 2009 ). The light spectrum, quantity, and duration that plants receive all affect photosynthesis, plant

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John L. Jifon, James P. Syvertsen, and Eric Whaley

This research was partially supported by grants from US/IS BARD and Spectrum Technologies Inc. and was funded by the Florida Agricultural Experiment Station. Approved for publication as Journal Series No. R-10091. Special thanks to Spectrum

Open access

Seon-Ok Kim, Ji-Eun Jeong, Yun-Ah Oh, Ha-Ram Kim, and Sin-Ae Park

stable condition, beta waves signify brain activity, and gamma waves show anxiety or excitement ( Kim and Choi, 2001 ). This study analyzed the RT power spectrum, RMB power spectrum, and RSMT. The RT power spectrum was obtained by dividing the theta wave