distribution and uniformity at a given height within the greenhouse. Although the wide-angle beam distribution of top lighting can maximize upper-canopy photon capture efficiency for mature crops, when plants are young and widely spaced, energy is wasted when
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
assimilation light ( Aaslyng et al., 2006 , Körner et al. 2006 ), were developed. Controlling greenhouse climate dynamically results in fluctuating greenhouse air temperature. Greenhouse air temperature and crop temperature influence each other, but due to
Chrysanthemum morifolium Ramat. cvs. White Marble and Improved Mefo were rooted and grown in cell paks for 34 days under ambient light plus: photoperiodic incandescent night-break lighting 2μE (m−2s−1); 64 μE m−2s−1 high pressure sodium (HPS) dusk to dawn lighting; or 126 μE m−2s−1 HPS dusk to dawn lighting. Container-grown chrysanthemums were fertilized with either 200 ppm N, 86 ppm P and 166 ppm K or 300 ppm N, 129 ppm P and 249 ppm K with every irrigation. After 34 long days these plants were transplanted into raised beds, immediately given short day conditions, and treated as a normal commercial crop. The container-grown treatments were compared to each other and to a bench-grown control which received a total of 48 long days. Supplemental HPS lighting increased the net assimilation rate (NAR), plant dry weight, and height of ‘White Marble’ chrysanthemums after 4 weeks. Increased fertility increased NAR and dry weight in the supplemental light treatment but not in the ambient light treatment. Results were less obvious for “Improved Mefo’. The container-grown treatments were ready for harvest 14 to 22 days before the controls. In both cultivars the high light-high fertility treatment was superior to the other container-grown treatments. The ‘White Marble’ high light-high fertility treatment produced higher quality chrysanthemums than the control, while the same ‘Improved Mefo’ treatment produced chrysanthemums slightly inferior to the control.
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.
The effects of planting density and short-term changes in photoperiod on the growth and photosynthesis of bean (Phaseolus vulgaris L.) was investigated. Two cultivars of bean (cv. Etna, a dry bean variety; cv. Hystyle, a snap bean variety) were grown using nutrient film technique hydroponics in a walk-in growth chamber with a 12 h/12 h (light/dark) photoperiod and a corresponding thermoperiod of 28/24 °C (light/dark) and constant 65% relative humidity. Lighting for the chamber consisted of VHO fluorescent lamps and irradiance at canopy level was 400 μmol·m-2·s-1 PPF. For each cultivar, plants were grown at densities of 16 or 32 plants/m2. Short-term photoperiod changes were imposed during vegetative growth (21-29 DAP) and pod-fill (42-57 DAP). From the base 12 h/12h (light/dark) photoperiod, lighting in the chamber was cycled to provide 18 h/06 h (light/dark) or 24 h/0 h(continuous light) for 48 h. Diurnal single leaf net photosynthetic rates (Pn) and net assimilation vs. internal CO2 (Aci) measurements were taken during the short-term photoperiod adjustments. Results showed that there was no difference between cultivars or planting density with regard to total biomass or single leaf photosynthetic rates, but cv. Etna produced 35% more edible biomass than cv. Hystyle. Additionally, there was no effect of short-term photoperiod adjustment on single leaf Pn or Aci.
“Plant factories with artificial lighting” are a new type of facility that can produce high yield with high quality all year round in a controlled environment (e.g., lighting, temperature, CO 2 concentration, and nutrients) ( Kozai, 2013a ; Yamori
previously ( Yamori et al., 2009 , 2010 ). We measured net CO 2 assimilation rates and g S in upper leaves with 150 μmol⋅m −2 ⋅s −1 downward lighting and in lower leaves with 150 μmol⋅m −2 ⋅s −1 upward lighting from each treatment. The CO 2
below a photosynthetic photon flux ( PPF ) of 200 μmol·m −2 ·s −1 , the leaf assimilation of chrysanthemum can be considered as responding close to linearly to irradiance levels. Supplemental light levels differ but are often lower than 200 μmol·m −2 ·s
Heat injury in creeping bentgrass (Agrostis stolonifera var. palustris Huds) has been associated with decreases in carbohydrate availability. Extending light duration may increase carbohydrate availability and thus improve growth of creeping bentgrass under heat stress. The objective of this study was to investigate whether turf performance and carbohydrate status could be improved by extending daily light duration for creeping bentgrass exposed to supraoptimal temperature conditions. `Penncross' plants were initially grown in growth chambers set at a day/night temperature of 20/15 °C and 14-hour photoperiod and then exposed to a day/night temperature of 33/28 °C (heat stress) and three different light durations: 14 (control), 18, and 22 hours (extended light duration) for 30 days. Turf quality and tiller density decreased with the duration of heat stress, as compared to the initial level at 20 °C, regardless of the light duration. However, both parameters increased with extended light duration from 14 to 18 or 22 hours. Extended light duration, particularly to 22 hours, also improved canopy net photosynthetic rate from -1.26 to 0.39 μmol·m-2·s-1 and daily total amount of carbon assimilation from -6.4 to 31.0 mmol·m-2·d-1, but reduced daily total amount of carbon loss or consumption to 50% through dark respiration compared to 14 hours treatment by the end of experiment. In addition, extending light duration from 14 to 22 hours increased water-soluble carbohydrate content in leaves both at the end of light duration and the dark period. These results demonstrated that extending light duration improved turf performance of creeping bentgrass under heat stress, as manifested by the increased tiller density and turf quality. This could be related to the increased carbohydrate production and accumulation. Supplemental lighting could be used to improve performance if creeping bentgrass is suffering from heat stress.