Abstract
Greenhouses with sophisticated environmental control systems, or so-called plant factories with solar light, enable growers to achieve high yields of produce with desirable qualities. In a greenhouse crop with high planting density, low photosynthetic photon flux density (PPFD) at the lower leaves tends to limit plant growth, especially in the winter when the solar altitude and PPFD at the canopy are low and day length is shorter than in summer. Therefore, providing supplemental lighting to the lower canopy can increase year-round productivity. However, supplemental lighting can be expensive. In some places, the cost of electricity is lower at night, but the effect of using supplemental light at night has not yet been examined. In this study, we examined the effects of supplemental LED inter-lighting (LED inter-lighting hereafter) during the daytime or nighttime on photosynthesis, growth, and yield of single-truss tomato plants both in winter and summer. We used LED inter-lighting modules with combined red and blue light to illuminate lower leaves right after the first anthesis. The PPFD of this light was 165 μmol m(-2) s(-1) measured at 10 cm from the LED module. LED inter-lighting was provided from 4:00 am to 4:00 pm for the daytime treatments and from 10:00 pm to 10:00 am for the nighttime treatments. Plants exposed only to solar light were used as controls. Daytime LED inter-lighting increased the photosynthetic capacity of middle and lower canopy leaves, which significantly increased yield by 27% in winter; however, photosynthetic capacity and yield were not significantly increased during summer. Nighttime LED inter-lighting increased photosynthetic capacity in both winter and summer, and yield increased by 24% in winter and 12% in summer. In addition, nighttime LED inter-lighting in winter significantly increased the total soluble solids and ascorbic acid content of the tomato fruits, by 20 and 25%, respectively. Use of nighttime LED inter-lighting was also more cost-effective than daytime inter-lighting. Thus, nighttime LED inter-lighting can effectively improve tomato plant growth and yield with lower energy cost compared with daytime both in summer and winter.
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Claims 10
Claim · model-written summary
Daytime LED lighting increased photosynthetic capacity of middle and lower leaves in winter.
- Taxon
- Tomatoes
Solanum lycopersicumt0 - Organ / stage
- middle and lower canopy leavese0
- Treatment
- Daytime LED inter-lightinge0
- Outcome
- photosynthetic capacitye0
- Direction
- increasede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Daytime LED inter-lighting increased the photosynthetic capacity of middle and lower canopy leaves”
t0“Tomatoes”
Claim · model-written summary
Daytime LED lighting significantly increased winter yield by 27%.
- Taxon
- TomatoesSolanum lycopersicumt0
- Treatment
- Daytime LED inter-lightinge0
- Outcome
- yielde0
- Direction
- increasede0
- Value
- 27%e0
- Qualifier
- in wintere0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Daytime LED inter-lighting increased the photosynthetic capacity of middle and lower canopy leaves, which significantly increased yield by 27% in winter”
t0“Tomatoes”
Claim · model-written summary
Daytime LED lighting did not significantly increase photosynthetic capacity in summer.
- Taxon
- TomatoesSolanum lycopersicumt0
- Outcome
- photosynthetic capacitye0
- Direction
- not significantly increasede0
- Qualifier
- during summere0
Not reportedTreatmentComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“photosynthetic capacity and yield were not significantly increased during summer”
t0“Tomatoes”
Claim · model-written summary
Daytime LED lighting did not significantly increase yield in summer.
- Taxon
- TomatoesSolanum lycopersicumt0
- Outcome
- yielde0
- Direction
- not significantly increasede0
- Qualifier
- during summere0
Not reportedTreatmentComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“photosynthetic capacity and yield were not significantly increased during summer”
t0“Tomatoes”
Claim · model-written summary
Nighttime LED lighting increased photosynthetic capacity in winter and summer.
- Taxon
- TomatoesSolanum lycopersicumt0
- Treatment
- Nighttime LED inter-lightinge0
- Outcome
- photosynthetic capacitye0
- Direction
- increasede0
- Qualifier
- both winter and summere0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Nighttime LED inter-lighting increased photosynthetic capacity in both winter and summer”
t0“Tomatoes”
Claim · model-written summary
Nighttime LED lighting increased winter yield by 24%.
- Taxon
- TomatoesSolanum lycopersicumt0
- Treatment
- Nighttime LED inter-lightinge0
- Outcome
- yielde0
- Direction
- increasede0
- Value
- 24%e0
- Qualifier
- in wintere0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Nighttime LED inter-lighting increased photosynthetic capacity in both winter and summer, and yield increased by 24% in winter and 12% in summer”
t0“Tomatoes”
Claim · model-written summary
Nighttime LED lighting increased summer yield by 12%.
- Taxon
- TomatoesSolanum lycopersicumt0
- Treatment
- Nighttime LED inter-lightinge0
- Outcome
- yielde0
- Direction
- increasede0
- Value
- 12%e0
- Qualifier
- in summere0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Nighttime LED inter-lighting increased photosynthetic capacity in both winter and summer, and yield increased by 24% in winter and 12% in summer”
t0“Tomatoes”
Claim · model-written summary
Nighttime LED lighting significantly increased winter fruit total soluble solids by 20%.
- Taxon
- tomatoSolanum lycopersicume0
- Treatment
- nighttime LED inter-lightinge0
- Outcome
- total soluble solidse0
- Direction
- increasede0
- Value
- 20e0
- Qualifier
- in wintere0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“nighttime LED inter-lighting in winter significantly increased the total soluble solids and ascorbic acid content of the tomato fruits, by 20 and 25%, respectively”
Claim · model-written summary
Nighttime LED lighting significantly increased winter fruit ascorbic acid by 25%.
- Taxon
- tomatoSolanum lycopersicume0
- Treatment
- nighttime LED inter-lightinge0
- Outcome
- ascorbic acid contente0
- Direction
- increasede0
- Value
- 25%e0
- Qualifier
- in wintere0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“nighttime LED inter-lighting in winter significantly increased the total soluble solids and ascorbic acid content of the tomato fruits, by 20 and 25%, respectively”
Claim · model-written summary
Nighttime lighting was more cost effective than daytime lighting.
- Taxon
- TomatoesSolanum lycopersicumt0
- Outcome
- more cost-effectivee0
- Comparator
- daytime inter-lightinge0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“nighttime LED inter-lighting was also more cost-effective than daytime inter-lighting”
t0“Tomatoes”
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