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Leora Radetsky, Jaimin S. Patel, and Mark S. Rea

provided equal nighttime irradiance levels of top lighting to DM-infected basil plants, but those irradiances were delivered using three temporal profiles: one continuous profile with 10 h of light and 0 h of dark (Treatment 2), one intermittent profile

Open access

Mary Hockenberry Meyer and Diane M. Narem

intermittent mist (5 s mist every 8 min) and 600-W high-pressure sodium lighting (Gavita, Vancouver, WA; GE Lighting, Cleveland, OH) with a 16-h daylength. For treatment 2, germination mix cold, after seed placement, the trays were lightly covered with clear, 6

Free access

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.

Free access

J. Raymond Kessler Jr. and Gary J. Keever

Vegetative cuttings of Coreopsis verticillata `Moonbeam' were rooted under intermittent mist, pinched, and potted into 10-cm pots in a greenhouse. Plants were sheared to 6.5 cm above the pot rim 2 weeks after potting and given foliar sprays of daminozide at 0, 2550, 5100, or 7650 mg·L-1 or flurprimidol at 0, 50, 100, or 150 mg·L-1. Night-break lighting to provide long photoperiods was started the day of shearing. Growth retardants were applied at 0, 3, 6, 9, 12, or 15 days after shearing. Daminozide reduced shoot height, growth index, and lateral shoot length compared to the control by 69.3%, 69.2%, and 70.0%, respectively, while increasing quality rating by 67.3% and time to flower by 8 days at 5100 and 7650 mg·L-1. Response surface regression predicted that minimum plant size and maximum quality rating occurred when growth retardants were applied 5.7 to 8.3 days after shearing. Application timing had no effect on responses to flurprimidol. Shoot height, growth index, and lateral shoot length decreased quadratically with increasing rate while quality rating only improved compared to control. Flurprimidol did not cause a flowering delay.

Free access

Matthew G. Blanchard and Erik S. Runkle

-Prue, 1975 ). Another NI lighting strategy is to provide cyclic or intermittent lighting. During cyclic lighting, INC lamps are turned on and off at specific intervals for a certain duration. Runkle et al. (1998) reported that LD herbaceous perennials

Full access

Qingwu Meng and Erik S. Runkle

short, low-intensity photoperiodic lighting can be used to control flowering of LDPs and SDPs. This can be achieved by delivering light beginning at the end of the day until the desired photoperiod is met (day extension) or during the middle of the night

Open access

Hunter A. Hammock, Dean A. Kopsell, and Carl E. Sams

light interacts with plants at a fundamental level, it is pertinent to determine the overall metabolic impacts of various discrete narrowband wavelengths along with potential synergetic and antagonistic interactions in broad spectrum lighting

Open access

Rui Wang, Masatake Eguchi, Yuqing Gui, and Yasunaga Iwasaki

quality/photoperiod ( Nestby and Sønsteby, 2017 ; Zahedi and Sarikhani, 2017 ). Researchers have attempted to explain how various lighting environments affect plant physiological responses such as leaf initiation, time to flowering, flowering rate, and

Free access

W. Garrett Owen, Qingwu Meng, and Roberto G. Lopez

northern latitudes, greenhouse growers can use low-intensity electric lighting to shorten long nights and promote or inhibit flowering of long- or short-day plants, respectively. Accelerating flowering of long-day plants shortens production time, whereas

Open access

Noriko Ohtake, Masaharu Ishikura, Hiroshi Suzuki, Wataru Yamori, and Eiji Goto

Plant factories with artificial lighting have been developed for efficient production of food crops and are now used for the commercial production of leafy greens and herbs in many countries ( Kozai, 2013 ). As the demands for year-round production