., 2019 ). Dimmable LED lights can be interfaced with quantum sensors and control systems, allowing for adaptive lighting control ( van Iersel and Gianino, 2017 ). With adaptive lighting, supplemental light is provided so that the PPFD of sunlight and
Geoffrey Weaver and Marc W. van Iersel
Marc W. van Iersel and David Gianino
enough supplemental light from LEDs to reach the threshold PPF . This adaptive control approach to lighting control should reduce energy use, by providing supplemental light only when needed and, in the case of PWM control, in the amount needed. To
Claudia Elkins and Marc W. van Iersel
precisely controlled and programmed to respond to environmental parameters (e.g., sunlight) in real time ( van Iersel and Gianino, 2017 ; van Iersel et al., 2016 ; Weaver et al., 2019 ). Our adaptive lighting control system measures the PPFD of the
Shuyang Zhen and Marc W. van Iersel
supplemental lighting in controlled environments based on plant physiological responses to light ( van Iersel et al., 2016a , 2016b ) and there is a need for information on how supplemental lighting can be optimized for crops adapted and/or acclimated to
Zhengnan Yan, Long Wang, Jiaxi Dai, Yufeng Liu, Duo Lin, and Yanjie Yang
energy to adapt to the lighting environment. However, chlorophyll content based on leaf area increased with the increasing PPFD ( Feng et al., 2019 ; Yu et al., 2016 ), which was associated with higher concentration of the RuBisCo enzyme, thus affecting
Michel Carrier, André Gosselin, and Laurent Gauthier
A dynamic management strategy for supplemental lighting in greenhouses was developed. It makes use of a plant growth model and of a rule-based decisionmaking protocol within the framework of a generic greenhouse climate management software system. The model, an adapted version of SUCROS87, tracks plant growth and predicts dry weight production based on measured or estimated values of light intensity, temperature, and CO2 concentration. A set of logical predicates (rules) implements the strategy's behavior. Optimization of lamp use was conducted as a function of economic criteria that enable a comparison between the additional income associated with yield increases due to supplemental lighting and incurred cost increases. Although the model is not perfectly reliable in its predictions, the system can be used to simulate the effect of changes to economic parameters on the decisions of the management strategy. The dynamic strategy described here differs from conventional supplemental lighting scenarios in the sense that it increases the length of the period of supplemental lighting when the daily solar light integral is low, and reduces or eliminates the use of supplemental lighting when the weather forecast predicts that the daily solar light integral will exceed plant requirements.
Olfa Ayari, Martine Dorais, Gilles Turcotte, and André Gosselin
Yield of greenhouse tomatoes has greatly increased during the past decade due to the development of more-productive cultivars and to the use of new technologies, such as supplemental lighting and CO2 enrichment. Under high PPF and p[CO2], however, the capacity of tomato plants to use supplemental energy and CO2 decreases. Our project aimed at determining the limits of photosynthetic capacity of tomato plants under supplemental lighting (HPS lamps, 100 μmol·m–2·s–1, photoperiod of 14 to 17 h) and high p[CO2] (900 ppm). The following measurements were made on the 5th and the 10th leaves of tomato plants at regular intervals from November to May: diurnal changes in net (Pn) and maximum (Pmax) photosynthetic rate, Chla fluorescence of dark-adapted and no dark-adapted leaves, and the soluble sugars and starch contents of the 5th and 10th leaves. Changes in global radiation from 250 W/m2 in winter to about 850 W/m2 in spring resulted in Pn increases of 45% and 42% in the 5th and 10th leaves, respectively. During the winter period, Pmax was higher than Pn, suggesting that leaves were not at maximum photosynthetic capacity. In the spring, no difference was found between Pmax and Pn. Sucrose concentration in leaves increased progressively up to a maximum of 12-h photoperiod, while hexoses remained constant. The Fv/Fm ratio did not vary during winter, but significantly decreased during spring due to photoinhibition. Increases in global radiation during spring resulted in lower photosynthetic rates, higher fluorescence, and starch accumulation in leaves. Data will be discussed in terms of crop efficiency and yield.
Jyotsna Joshi, Geng Zhang, Shanqi Shen, Kanyaratt Supaibulwatana, Chihiro K.A. Watanabe, and Wataru Yamori
“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
O. Ayari, M. Dorais, and A. Gosselin
Daily and seasonal variations of photosynthetic activity, chlorophyll a (Chl-a) fluorescence and foliar carbohydrate content were studied in situ on greenhouse tomato (Lycopersicon esculentum Mill. `Trust') plants grown under CO2 enrichment and supplemental lighting. The objective of this study was to assess the effect of seasonal variation of the photosynthetic photon flux (PPF) on photosynthetic efficiency of tomato plants and to determine the presence or absence of photosynthetic down-regulation under greenhouse growing conditions prevailing in northern latitudes. During winter, the fifth and the tenth leaves of tomato plants showed low, constant daily photosynthetic activity suggesting a source limitation under low PPF. In winter, the ratio of variable to maximum Chl-a fluorescence in dark adapted state (Fv/Fm) remained constant during the day indicating no photoinhibition occurred. In February, an increase in photosynthetic activity was followed by a decline during March, April, and May accompanied by an increase in sucrose and daily starch concentrations and constant but high hexose level. This accumulation was a long-term response to high PPF and CO2 enrichment which would be caused by a sink limitation. Thus, in spring we observed an in situ downregulation of photosynthesis. The ratio Fv/Fm decreased in spring compared to winter in response to increasing PPF. The daily decline of Fv/Fm was observed particularly as a midday depression followed by a recovery towards the end of the day. This indicated that tomato leaves were subject to a reversible inhibition in spring. Fv/Fm was lower in March than in April and May even though PPF was higher in April and May than in March. These results suggest that tomato plants develop an adaptive and protective strategy as PPF increases in spring.
Heidi M. Wollaeger and Erik S. Runkle
plants, which causes a dark green coloration of leaves, is also desirable in commercial production of young plants such as microgreens, herbs, and ornamental propagules. Growing plants under sole-source solid-state lighting that includes B light in an R