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Soohyun Kang, Yating Zhang, Yuqi Zhang, Jie Zou, Qichang Yang, and Tao Li

factories has been conducted with only blue and red light ( Hernández and Kubota, 2016 ; Trouwborst et al., 2016 ). As a consequence, it is still unknown whether additional UV-A radiation would benefit indoor plant cultivation. Plants adjust their

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Edward J. Nangle, David S. Gardner, James D. Metzger, Dominic P. Petrella, Tom K. Danneberger, Luis Rodriguez-Saona, and John L. Cisar

exposure to wavelengths in the ultraviolet (UV-A 400–320 nm/UV-B 320–290 nm/UV-C 290–100 nm) range ( Kerr and McElroy, 1993 ). The UV-B wavelengths that contact the earth’s surface are predicted to increase in springtime radiation by 50% to 60% from 2010 to

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Maria E. Cramer, Kathleen Demchak, Richard Marini, and Tracy Leskey

less discouraging to Japanese beetle. All plastics evaluated in this study reduced significantly the number of Japanese beetles on both cultivars, and differences between plastics were usually apparent. In addition to transmittance of UV-A radiation

Open access

Kaitlyn M. Orde, Rich Marini, Kathleen Demchak, and Rebecca Sideman

can result in more compact strawberry plants ( Fletcher et al., 2004 ). Furthermore, plant exposure to ultraviolet (UV) radiation triggers the production of secondary metabolites involved in a number of important processes and compounds, including

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Kelly M. Gude, Eleni D. Pliakoni, Brianna Cunningham, Kanwal Ayub, Qing Kang, Channa B. Rajashekar, and Cary L. Rivard

spring and summer, the soil increased in temperature under the clear covering compared with the other tested coverings, which past studies suggest may be a result of the increased radiation ( Miles et al., 2012 ). Understanding how the use of UV

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Richard M. Klein

In order to determine whether the concentration of floral petal anthocyanin pigments could be increased, ultraviolet radiations in the UV-A and UV-B wavelength bands were presented to a variety of flowering plants to partly restore those wavelengths filtered out by greenhouse glass. In no tested plant did the supplementary ultraviolet radiation enhance floral anthocyanin content. Supplementary UV radiation has no economic value in greenhouse production of flowering plants.

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Donald T. Krizek, Roman M. Mirecki, and Steven J. Britz

The influence of ambient UV radiation on growth, chlorosis, and flavonoid content was examined in four cultivars of cucumber (`Ashley', `Poinsett', `Marketmore', and `Salad Bush'). Plants were grown from seed in UV exclusion chambers consisting of UV transmitting plexiglass (10% T, 285 nm), lined with 3- or 5-mil Llumar (10% T, 399 or 404 nm) to exclude UV-A and UV-B, 5-mil polyester (10%T, 319 nm) to exclude UVB, or cellulose acetate (10% T, 291 nm) to transmit UV-A and UV-B. Plants were grown in 15 cm plastic pots containing vermiculite and were fertilized daily with nutrient solution. Despite their differential sensitivity to supplemental UV-B radiation, all four cultivars responded similarly to the exclusion treatments. After 19 to 21 days, plants grown under ambient UV-A and UV-B generally had less stem, leaf, and root biomass and less total height and total leaf area than those grown under conditions in which UV-A and UV-B or only UV-B was excluded. Flavonoid content, leaf number, and floral development were unaffected by UV. These findings demonstrate the extreme sensitivity of cucumber to current levels of solar UV radiation.

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Donald T. Krizek, Steven J. Britz, and Roman M. Mirecki

The influence of ambient UV radiation on growth and flavonoid concentration of Lactuca sativa L. (`New Red Fire' lettuce) was examined. Plants were grown outdoors for 31 days from seed in window boxes covered with one of three different UV filters—UV transparent tefzel (10%T, 245 nm), UV-B-absorbing polyester (10%T, 319 nm), or UV-Aand UV-B-absorbing Llumar (10%T, 399 nm). Plants were grown in plastic pots filled with vermiculite and subirrigated with nutrient solution. Lettuce plants grown in the absence of solar UV-A and UV-B radiation showed a significant increase in leaf number and biomass of tops and roots as compared to those grown under ambient UV-A and UV-B. They also had a lower concentration of flavonoids and other UV-absorbing substances at 270, 300, and 330 nm (on both an area and on a dry-weight basis). These findings should be of interest to researchers involved in protected cultivation because the transmission of UV-B radiation is greatly attenuated by standard greenhouse glass. Our results also have implications for human nutrition, since bioflavonoids are important as antioxidants.

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Erik H. Ervin, Xunzhong Zhang, and John H. Fike

1 Assistant professor. 2 Research scientist. This research was conducted as part of USDA-CSREES project no. VA-135660. Mention of a trademark, proprietary product, or vendor does not constitute a guarantee or warranty of the product by

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Beatriz M. Díaz, Ricardo Biurrún, Aránzazu Moreno, Miguel Nebreda, and Alberto Fereres

Ultraviolet (UV)-absorbing plastic films are being used as a photoselective barrier to control insect vectors and associated virus diseases in different horticultural crops. A 2-year experiment was carried out in northeastern Spain (Navarra) to evaluate the impact of a UV-blocking film (AD-IR AV) on the population density of insect pests and the spread of insect-transmitted virus diseases associated with head lettuce [Lactuca sativa (L.)]. Results showed that the UV-absorbing plastic film did not loose its ability to filter UV radiation after three lettuce crop cycles (14 months). The UV-absorbing plastic film was effective in reducing the abundance and in delaying the colonization of lettuce by aphids [Macrosiphum euphorbiae (Thomas) and Acyrthosiphum lactucae (Passerini)]. A significant increase in the percentage of marketable plants was achieved under UV-absorbing films due to a reduction in the number of plants infested by aphids and by insect-transmitted virus diseases (mainly potyviruses). Also the UV-absorbing plastic films were effective in reducing the population density of Frankliniella occidentalis (Pergande) and the spread of tomato spotted wilt virus (TSWV) as well as the population density of the lepidopteran pest, Autographa gamma (L.), a common pest of lettuce in Spain. However, no effective control of the greenhouse whitefly Trialeurodes vaporariorum (Westwood) was achieved. The results showed that UV-absorbing plastic films are a very promising tool to protect greenhouse lettuce from the main pests and insect-transmitted virus diseases occurring in northeastern Spain.