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Jens N. Wünsche and Alan N. Lakso

The study evaluated the relationship of spur vs. extension shoot leaf area and light interception to apple (Malus {XtimesX} domesticaBorkh.) orchard productivity. Fifteen-year-old `Marshall McIntosh'/M.9 trees had significantly greater leaf area and percentage of light interception at 3-5 and 10-12 weeks after full bloom (AFB) than did 4-year-old `Jonagold'/Mark trees. Despite significant increases in leaf area and light interception with canopy development, linear relationships between total, spur, and extension shoot canopy leaf area index (LAI) and 1) light interception and 2) fruit yield were similar at both times. Mean total and spur canopy LAI and light interception were significantly and positively correlated with fruit yield; however, extension shoot LAI and light interception were poorly correlated with yield. In another study total, spur and extension shoot canopy light interception varied widely in five apple production systems: 15-year-old central leader `Redchief Delicious' MM.111, 15-year-old central leader `Redchief Delicious' MM.111/M.9, 16-year-old slender spindle `Marshall McIntosh' M.9, 14-year-old `Jerseymac' M.9 on 4-wire trellis, and 17-year-old slender spindle `MacSpur' M.9. Yields in these orchards were curvilinearly related to total and extension shoot canopy light interception and decreased when total light interception exceeded 60% and extension shoot interception exceeded 25%. Fruit yields were linearly and highly correlated (r 2 = 0.78) with spur light interception. The findings support the hypothesis that fruit yields of healthy apple orchards are better correlated with LAI and light interception by spurs than by extension shoots. The results emphasize the importance of open, well-illuminated, spur-rich tree canopies for high productivity.

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Kun Li, Qi-Chang Yang, Yu-Xin Tong, and Ruifeng Cheng

Technology Co., Laiwu, China) was employed to measure the electricity consumption of the lighting (the energy costs for cooling, ventilation, and the recirculation of the nutrient solution were not considered during our experiments). The light utilization

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David S. de Villiers, Robert W. Langhans, A.J. Both, Louis D. Albright, and Sue Sue Scholl

CO2 enrichment increases efficiency of light utilization and rate of growth, thereby reducing the need for supplemental lighting and potentially lowering cost of production. However, during warmer periods of the year, CO2 enrichment is only possible intermittently due to the need to vent for temperature control. Previous research investigated the separate and combined effects of daily light integral and continuous CO2 enrichment on biomass accumulation in lettuce. The current research was designed to look at the efficiency with which lettuce is able to utilize intermittent CO2 enrichment, test the accuracy with which growth can be predicted and controlled, and examine effects of varying CO2 enrichment and supplemental lighting on carbon assimilation and plant transpiration on a minute by minute basis. Experiments included application of various schedules of intermittent CO2 enrichment and gas exchange analysis to elucidate underlying physiological processes. Same-day and day-to-day adjustments in daily light integrals were made in response to occasional CO2 venting episodes, using an up-to-the-minute estimate of growth progress based on an integration of growth increments that were calculated from actual light levels and CO2 concentrations experienced by the plants. Results indicated lettuce integrates periods of intermittent CO2 enrichment well, achieving expected growth targets as measured by destructive sampling. The gas-exchange work quantified a pervasive impact of instantaneous light level and CO2 concentration on conductance and CO2 assimilation. Implications for when to apply supplemental lighting and CO2 enrichment to best advantage and methods for predicting and controlling growth under intermittent CO2 enrichment are discussed.

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Wenjing Guan, Daniel S. Egel, Larry D. Sutterer, and Alexander D. Plummer

461 467 Welbaum, G.E. 2015 Vegetable production and practices. CABI, Wallingford, UK Zhou, Y. Zhou, J. Huang, L. Ding, X. Shi, K. Yu, J. 2009 Grafting of Cucumis sativus onto Cucurbita ficifolia leads to improved plant growth, increased light

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Anke van der Ploeg, Susana M.P. Carvalho, and Ep Heuvelink

259 Karlsson, M.G. Heins, R.D. Holcomb, E.J. 1987 Influence of temperature, photosynthetic photon flux and plant age on light utilization efficiency in chrysanthemum Acta Hort. 197 21 30

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Jongyun Kim, Seung Won Kang, Chun Ho Pak, and Mi Seon Kim

physiological and morphological changes (i.e., acclimation), resulting either in increased light capture or improved light utilization. General acclimation responses to low light include higher shoot to root ratio (whole-plant level), increased leaf size per

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Marjorie Reyes-Diaz, Miren Alberdi, and Maria de la Luz Mora

, Editorial Salesianos Impressores Santiago, Chile Savitch, L.V. Leonardos, E.D. Krol, M. Jansson, S. Grodzinski, B. Hüner, N.P.A. Öquist, G. 2002 Two different strategies for light

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Shuai-Ping Gao, Kang-Di Hu, Lan-Ying Hu, Yan-Hong Li, Yi Han, Hui-Li Wang, Kai Lv, Yong-Sheng Liu, and Hua Zhang

( Glycine max ) induced by oxidative stress Physiol. Plant. 97 388 396 Kornyeyev, D. Logan, B.A. Payton, P. Allen, R.D. Holaday, A.S. 2001 Enhanced photochemical light utilization and decreased chilling-induced photoinhibition of photosystem II in cotton

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Giverson Mupambi, Stefano Musacchi, Sara Serra, Lee A. Kalcsits, Desmond R. Layne, and Tory Schmidt

treatments, the reduction in light intensity under blue photoselective PN resulted in better light utilization, as shown by the significantly greater F v /F m values. The combination of heat and light stress on the day with high ambient temperature increased

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Ze Li, Kai Shi, Fanhang Zhang, Lin Zhang, Hongxu Long, Yanling Zeng, Zhiming Liu, Genhua Niu, and Xiaofeng Tan

tree seedlings were found to decrease with an increase in shade levels, suggesting that light utilization efficiency was reduced dramatically in tung tree seedlings ( Chen et al., 2005 ; Sui et al., 2012 ; Yan et al., 2013 ). In addition, there was a