Articles
New lighting strategy for indoor leafy greens by segmenting the photoperiod and replacing the dark period by their light compensation point
Article number
1337_15
Pages
107 – 116
Language
English
Abstract
New growing systems such as indoor vertical farming maximize the benefits of LED lighting systems and crop sustainability.
We hypothesized that for a same day light integral (DLI), leafy greens exposed alternatively to short photoperiod having high PPFD followed by an equivalent or shorter photoperiod of low photosynthetic photon flux density (PPFD), corresponding to their light compensation point (LCP), have a better light use efficiency and profitability than plants grown under moderate PPFD with a short dark period.
To test this hypothesis, three lighting treatments were compared for 4 leafy greens (arugula (A), Eruca sativa Mill.; lettuce, Lactuca sativa L. cultivars Salanova Green Butter (SG), Salanova Red Butter (SR), and Bergams Green (BG)) grown in growth chambers under LED having a Blue: Red ratio of 0.13. Two experiments were performed by using two lighting treatments: 5L/1N (5 h at PPFD of 180 µmol m‑2 s‑1 and 1 h of dark; total of 20 h of lighting day-1, control) and 6L/6LCP (6 h at PPFD of 280 µmol m‑2 s‑1 and 6 h of LCP at 20 µmol m‑2 s‑1; total of 12 h of lighting day-1 + 12 h at LCP) for a similar day light integral of 12.96 mol m‑2 day-1. A third experiment using the same DLI was performed to compare 5L/1N (20 h lighting + 4 h dark day-1) and 5L/1LCP (20 h lighting + 4 h LCP day-1) treatments.
Significant interactions between species and light treatments were observed for the leaf chlorophyll content (SPAD value), the Fv/Fm ratio, the apparent quantum yield (φ), the shoot fresh and dry biomass, the plant leaf area and LAI, while Amax, Rd and LCP, the root fresh and dry biomass and the biomass partitioning between the shoot and the root were not impacted by the light treatments.
However, the performance index (PI) was higher under 5L/1LCP, regardless of the species or cultivars.
Furthermore, the photon yield (g mol-1 of photons) was species and cultivars dependent.
In terms of the fresh biomass produced mol-1 photons received, little difference was observed between the light treatments, except the lower performance of SR exposed to 6L/6LCP. On a dry weight basis, 6L/6LCP increased the photon yield of BG by 29% compared with 5L/1LCP, while 5L/1LCP decreased the photon yield of arugula compared with 5L/1N; no difference was observed between 5L/1N and 6L/6LCP.
We hypothesized that for a same day light integral (DLI), leafy greens exposed alternatively to short photoperiod having high PPFD followed by an equivalent or shorter photoperiod of low photosynthetic photon flux density (PPFD), corresponding to their light compensation point (LCP), have a better light use efficiency and profitability than plants grown under moderate PPFD with a short dark period.
To test this hypothesis, three lighting treatments were compared for 4 leafy greens (arugula (A), Eruca sativa Mill.; lettuce, Lactuca sativa L. cultivars Salanova Green Butter (SG), Salanova Red Butter (SR), and Bergams Green (BG)) grown in growth chambers under LED having a Blue: Red ratio of 0.13. Two experiments were performed by using two lighting treatments: 5L/1N (5 h at PPFD of 180 µmol m‑2 s‑1 and 1 h of dark; total of 20 h of lighting day-1, control) and 6L/6LCP (6 h at PPFD of 280 µmol m‑2 s‑1 and 6 h of LCP at 20 µmol m‑2 s‑1; total of 12 h of lighting day-1 + 12 h at LCP) for a similar day light integral of 12.96 mol m‑2 day-1. A third experiment using the same DLI was performed to compare 5L/1N (20 h lighting + 4 h dark day-1) and 5L/1LCP (20 h lighting + 4 h LCP day-1) treatments.
Significant interactions between species and light treatments were observed for the leaf chlorophyll content (SPAD value), the Fv/Fm ratio, the apparent quantum yield (φ), the shoot fresh and dry biomass, the plant leaf area and LAI, while Amax, Rd and LCP, the root fresh and dry biomass and the biomass partitioning between the shoot and the root were not impacted by the light treatments.
However, the performance index (PI) was higher under 5L/1LCP, regardless of the species or cultivars.
Furthermore, the photon yield (g mol-1 of photons) was species and cultivars dependent.
In terms of the fresh biomass produced mol-1 photons received, little difference was observed between the light treatments, except the lower performance of SR exposed to 6L/6LCP. On a dry weight basis, 6L/6LCP increased the photon yield of BG by 29% compared with 5L/1LCP, while 5L/1LCP decreased the photon yield of arugula compared with 5L/1N; no difference was observed between 5L/1N and 6L/6LCP.
Authors
L. Boucher, J. Eaves, A. Brégard, S. Pepin, M. Dorais
Keywords
artificial lighting management, LED, light emitting diode, photoperiod, plant factory
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