Abstract
Supplemental lighting can improve the growth of greenhouse crops, but the electricity required for supplemental lighting can be a significant expense for greenhouse growers. Lighting control strategies that use the dimmability of light-emitting diodes (LEDs) have the potential to decrease this cost. In our experiments, we tested the hypothesis that providing ‘Little Gem’ lettuce ( Lactuca sativa ) plants with the same daily amount of light, spread out over a longer photoperiod and at lower average photosynthetic photon flux densities ( PPFD s), would improve growth because light is used more efficiently to drive photosynthesis at lower PPFD s. We conducted two greenhouse experiments wherein supplemental light was provided to reach a minimum daily light integral (DLI) of 17 mol·m −2 ·d −1 with a 12, 15, 18, or 21-hour photoperiod using adaptive lighting control of LED lights. As the photoperiod for supplemental lighting was increased and supplemental light was provided at lower average PPFD s, plant dry weight increased. Conversion efficiency, the estimated increase in dry weight per Joule expended on supplemental lighting, increased as the photoperiod was extended from 12 to 21 hours. Leaf size and chlorophyll content index increased with longer photoperiods. The number of plants with symptoms of tipburn, including apical and marginal necrosis, also increased as the photoperiod was extended. These results demonstrate that adaptive lighting control can be used to increase the growth of ‘Little Gem’ lettuce and the energy use efficiency of supplemental lighting by providing supplemental light at relatively low PPFD s.
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Claims 4
Claim · model-written summary
Plant dry weight increased as the photoperiod for supplemental lighting was lengthened, with supplemental light at lower average PPFDs.
- Taxon
- Lactuca sativa
Lactuca sativat0 - Treatment
- photoperiod for supplemental lightinge1
- Outcome
- plant dry weighte1
- Direction
- increasede1
- Setting
- greenhouse experimentse0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Lactuca sativa”
e0“We conducted two greenhouse experiments”
e1“As the photoperiod for supplemental lighting was increased and supplemental light was provided at lower average PPFD s, plant dry weight increased”
Claim · model-written summary
Conversion efficiency increased as the supplemental-lighting photoperiod was extended from 12 to 21 hours.
- Taxon
- Lactuca sativaLactuca sativat0
- Treatment
- photoperiode2
- Outcome
- Conversion efficiencye2
- Direction
- increasede2
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Lactuca sativa”
e2“Conversion efficiency, the estimated increase in dry weight per Joule expended on supplemental lighting, increased as the photoperiod was extended from 12 to 21 hours”
Claim · model-written summary
Leaf size and chlorophyll content index increased with longer photoperiods.
- Taxon
- Lactuca sativaLactuca sativat0
- Treatment
- longer photoperiodse3
- Outcome
- Leaf size and chlorophyll content indexe3
- Direction
- increasede3
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Lactuca sativa”
e3“Leaf size and chlorophyll content index increased with longer photoperiods”
Claim · model-written summary
The number of plants with tipburn symptoms increased as the photoperiod was extended.
- Taxon
- Lactuca sativaLactuca sativat0
- Treatment
- photoperiode4
- Outcome
- The number of plants with symptoms of tipburne4
- Direction
- increasede4
- Qualifier
- apical and marginal necrosise4
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Lactuca sativa”
e4“The number of plants with symptoms of tipburn, including apical and marginal necrosis, also increased as the photoperiod was extended”
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