Abstract
Light recommendations for horticultural crops often focus on the optimal daily light integral (DLI) without regard to how that light is delivered throughout each day. Because photosynthesis is more efficient at lower photosynthetic photon flux density (PPFD), we hypothesized that longer photoperiods with lower PPFD results in faster growth than shorter photoperiods with higher PPFD and the same DLI. We quantified the effect of different photoperiods, all providing the same DLI, on photosynthesis and growth of two leafy greens. Mizuna (Brassica rapa var. japonica) and lettuce (Lactuca sativa) “Little Gem” were grown from seed in a controlled environment chamber (20 °C and 819 µmol·mol−1 CO2) under six photoperiods (10, 12, 14, 16, 18, and 20 h). LED fixtures provided white light and PPFD was adjusted so each treatment received a DLI of 16 mol·m−2·d−1. Mizuna and lettuce were harvested 30 and 41 days after planting, respectively. Longer photoperiods with lower PPFD increased light interception, chlorophyll content index, quantum yield of photosystem II, and aboveground biomass, but decreased instantaneous CO2 assimilation of lettuce and mizuna. Aboveground biomass increased 16.0% in lettuce and 18.7% in mizuna in response to increasing the photoperiod from 10 to 20 h. In summary, extending the photoperiod and lowering PPFD increases growth of lettuce and mizuna by increasing light interception and the quantum yield of photosystem II.
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Claims 6
Claim · model-written summary
Longer photoperiods with lower PPFD increased light interception, chlorophyll content index and quantum yield of photosystem II in lettuce.
- Taxon
- lettuce
Lactuca sativat0 - Material
- Little Geme3
- Treatment
- Longer photoperiods with lower PPFDe1
- Outcome
- light interception, chlorophyll content index, quantum yield of photosystem IIe1
- Direction
- increasede1
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Increasing Growth of Lettuce and Mizuna”
e1“Longer photoperiods with lower PPFD increased light interception, chlorophyll content index, quantum yield of photosystem II, and aboveground biomass, but decreased instantaneous CO2 assimilation of lettuce and mizuna”
e3“lettuce (Lactuca sativa) “Little Gem” were grown from seed”
Claim · model-written summary
Longer photoperiods with lower PPFD increased light interception, chlorophyll content index and quantum yield of photosystem II in mizuna.
- Taxon
- Mizuna
Brassica rapa subsp. nipposinicat0 - Treatment
- Longer photoperiods with lower PPFDe1
- Outcome
- light interception, chlorophyll content index, quantum yield of photosystem IIe1
- Direction
- increasede1
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Increasing Growth of Lettuce and Mizuna”
e1“Longer photoperiods with lower PPFD increased light interception, chlorophyll content index, quantum yield of photosystem II, and aboveground biomass, but decreased instantaneous CO2 assimilation of lettuce and mizuna”
Claim · model-written summary
Aboveground biomass of lettuce increased 16.0% when the photoperiod was increased from 10 to 20 h.
- Taxon
- lettuceLactuca sativat0
- Material
- Little Geme3
- Treatment
- increasing the photoperiod from 10 to 20 he2
- Outcome
- Aboveground biomasse2
- Direction
- increasede2
- Value
- 16.0%e2
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Increasing Growth of Lettuce and Mizuna”
e2“Aboveground biomass increased 16.0% in lettuce and 18.7% in mizuna in response to increasing the photoperiod from 10 to 20 h”
e3“lettuce (Lactuca sativa) “Little Gem” were grown from seed”
Claim · model-written summary
Aboveground biomass of mizuna increased 18.7% when the photoperiod was increased from 10 to 20 h.
- Taxon
- MizunaBrassica rapa subsp. nipposinicat0
- Treatment
- increasing the photoperiod from 10 to 20 he2
- Outcome
- Aboveground biomasse2
- Direction
- increasede2
- Value
- 18.7%e2
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Increasing Growth of Lettuce and Mizuna”
e2“Aboveground biomass increased 16.0% in lettuce and 18.7% in mizuna in response to increasing the photoperiod from 10 to 20 h”
Claim · model-written summary
Longer photoperiods with lower PPFD decreased instantaneous CO2 assimilation of lettuce.
- Taxon
- lettuceLactuca sativat0
- Material
- Little Geme3
- Treatment
- Longer photoperiods with lower PPFDe1
- Outcome
- instantaneous CO2 assimilatione1
- Direction
- decreasede1
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Increasing Growth of Lettuce and Mizuna”
e1“Longer photoperiods with lower PPFD increased light interception, chlorophyll content index, quantum yield of photosystem II, and aboveground biomass, but decreased instantaneous CO2 assimilation of lettuce and mizuna”
e3“lettuce (Lactuca sativa) “Little Gem” were grown from seed”
Claim · model-written summary
Longer photoperiods with lower PPFD decreased instantaneous CO2 assimilation of mizuna.
- Taxon
- MizunaBrassica rapa subsp. nipposinicat0
- Treatment
- Longer photoperiods with lower PPFDe1
- Outcome
- instantaneous CO2 assimilatione1
- Direction
- decreasede1
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Increasing Growth of Lettuce and Mizuna”
e1“Longer photoperiods with lower PPFD increased light interception, chlorophyll content index, quantum yield of photosystem II, and aboveground biomass, but decreased instantaneous CO2 assimilation of lettuce and mizuna”
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