Articles
Response of greenhouse tomato to a long photoperiod of lighting varies with daily light integral
Article number
1423_37
Pages
293 – 300
Language
English
Abstract
The improvement in plant productivity by supplemental lighting in greenhouse crop production is closely related to the total amount of light during a day (daily light integral (DLI) = intensity × photoperiod). It is more economical to achieve target DLIs with long photoperiods of low intensity lighting because it reduces light fixture costs.
Furthermore, in jurisdictions where the price of electricity is lower during the nighttime than daytime and is from low-emission sources (such as nuclear and hydro), long photoperiods of lighting (such as 24-h light) and shifting more lighting from daytime to nighttime can reduce energy costs and CO2 emission because the heat released by the light fixtures reduces heating demand during the otherwise dark night period.
However, lighting GROTERDAN16-17 h (the conventional photoperiod) causes long photoperiod injury such as leaf chlorosis, and reduced growth and yield in tomatoes.
In our previous studies, we have observed the injury occurred mostly during the darkest months of the year and plants recovered from the injury in early spring when more sunlight is available, which indicates the tolerance to long photoperiod injury may vary with DLIs or spectra or both.
Therefore, this study investigated if the injury on tomatoes by 24-h lighting is affected by DLIs in a 200 m2 greenhouse from October 2021 to May 2022. The plant growth and fruit yield of tomatoes grown under four 24-h lighting treatments, consisting of 2 DLIs (12.5 (low) and 21.5 (high) mol m‑2 d‑1) and 2 nighttime red light intensities (72 (low) and 144 (high) µmol m‑2 s‑1), were evaluated.
The treatment with the low DLI and the low night light intensity was used as the control for this study as our previous studies have shown it has the same crop performance as conventional 16-h of supplemental lighting.
Leaf photosynthetic rates were lower at the high than at the low night light intensity at low DLI, but was not different at the high DLI. Fruit yield was not reduced by the high light intensity at the high DLI. Therefore, the high red night light intensity can be used to reduce electricity costs in regions with low night electricity price.
Furthermore, in jurisdictions where the price of electricity is lower during the nighttime than daytime and is from low-emission sources (such as nuclear and hydro), long photoperiods of lighting (such as 24-h light) and shifting more lighting from daytime to nighttime can reduce energy costs and CO2 emission because the heat released by the light fixtures reduces heating demand during the otherwise dark night period.
However, lighting GROTERDAN16-17 h (the conventional photoperiod) causes long photoperiod injury such as leaf chlorosis, and reduced growth and yield in tomatoes.
In our previous studies, we have observed the injury occurred mostly during the darkest months of the year and plants recovered from the injury in early spring when more sunlight is available, which indicates the tolerance to long photoperiod injury may vary with DLIs or spectra or both.
Therefore, this study investigated if the injury on tomatoes by 24-h lighting is affected by DLIs in a 200 m2 greenhouse from October 2021 to May 2022. The plant growth and fruit yield of tomatoes grown under four 24-h lighting treatments, consisting of 2 DLIs (12.5 (low) and 21.5 (high) mol m‑2 d‑1) and 2 nighttime red light intensities (72 (low) and 144 (high) µmol m‑2 s‑1), were evaluated.
The treatment with the low DLI and the low night light intensity was used as the control for this study as our previous studies have shown it has the same crop performance as conventional 16-h of supplemental lighting.
Leaf photosynthetic rates were lower at the high than at the low night light intensity at low DLI, but was not different at the high DLI. Fruit yield was not reduced by the high light intensity at the high DLI. Therefore, the high red night light intensity can be used to reduce electricity costs in regions with low night electricity price.
Authors
X. Hao, J. Lanoue, S. St. Louis, C. Little
Keywords
Solanum lycopersicum, daily light integral, leaf chlorosis, photoperiod, photosynthesis, yield
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