Abstract
Plant light use efficiency decreases as light intensity is increased, and a better understanding of crop-specific light responses can contribute to the development of more energy-efficient supplemental lighting control strategies for greenhouses. In this study, diurnal chlorophyll fluorescence monitoring was used to characterize the photochemical responses of ‘Green Towers’ lettuce ( Lactuca sativa L.) to photosynthetic photon flux density ( PPFD ) and daily light integral (DLI) in a greenhouse during a production cycle. Plants were monitored continuously for 35 days, with chlorophyll fluorescence measurements collected once every 15 minutes. Quantum yield of photosystem II (ΦPSII) decreased exponentially with PPFD , whereas electron transport rate (ETR) increased asymptotically to 121 µmol·m –2 ·s –1 . Daily photochemical integral (DPI) is defined as the integral of ETR over a 24-hour period; DPI increased asymptotically to 3.29 mol·m –2 ·d –1 with increasing DLI. No effects of plant age or prior day’s DLI and a negligible effect of PPFD s 15 or 30 minutes before measurements within days were observed. Simulations were conducted using the regression equation of ETR as a function of PPFD {ETR = 121[1 – exp(–0.00277 PPFD )]} to illustrate methods of increasing photochemical light use efficiency for improved supplemental lighting control strategies. For a given DLI, DPI can be increased by providing light at lower PPFD s for a longer period of time, and can be maximized by providing light with a uniform PPFD throughout the entire photoperiod. Similarly, the DLI required to achieve a given DPI is reduced using these same methods.
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Claims 10
Claim · model-written summary
Photosystem II quantum yield decreased exponentially with photon flux density.
- Taxon
- Lactuca sativa L.
Lactuca sativat0 - Material
- ‘Green Towers’t0
- Treatment
- PPFDe0
- Outcome
- Quantum yield of photosystem II (ΦPSII)e0
- Direction
- decreasede0
- Qualifier
- exponentiallye0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Quantum yield of photosystem II (ΦPSII) decreased exponentially with PPFD”
t0“Lettuce (Lactuca sativa L. ‘Green Towers’)”
Claim · model-written summary
Electron transport rate increased asymptotically to 121 µmol·m –2 ·s –1 with photon flux density.
- Taxon
- Lactuca sativa L.Lactuca sativat0
- Material
- ‘Green Towers’t0
- Treatment
- PPFDe0
- Outcome
- electron transport rate (ETR)e0
- Direction
- increasede0
- Value
- 121 µmol·m –2 ·s –1e0
- Qualifier
- asymptoticallye0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Quantum yield of photosystem II (ΦPSII) decreased exponentially with PPFD , whereas electron transport rate (ETR) increased asymptotically to 121 µmol·m –2 ·s –1 .”
t0“Lettuce (Lactuca sativa L. ‘Green Towers’)”
Claim · model-written summary
Daily photochemical integral increased asymptotically to 3.29 mol·m –2 ·d –1 as daily light integral increased.
- Taxon
- Lactuca sativa L.Lactuca sativat0
- Treatment
- DLIe0
- Outcome
- DPIe0
- Direction
- increasede0
- Value
- 3.29 mol·m –2 ·d –1e0
- Qualifier
- asymptoticallye0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Daily photochemical integral (DPI) is defined as the integral of ETR over a 24-hour period; DPI increased asymptotically to 3.29 mol·m –2 ·d –1 with increasing DLI.”
t0“Lactuca sativa L.”
Claim · model-written summary
Plant age had no observed effect on the photochemical response.
- Taxon
- Lactuca sativa L.Lactuca sativat0
- Organ / stage
- plant agee0
- Outcome
- photochemical responsese1
- Direction
- No effectse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“No effects of plant age or prior day’s DLI and a negligible effect of PPFD s 15 or 30 minutes before measurements within days were observed.”
e1“photochemical responses”
t0“Lactuca sativa L.”
Claim · model-written summary
Prior-day daily light integral had no observed effect on photochemical response.
- Taxon
- Lactuca sativa L.Lactuca sativat0
- Treatment
- prior day’s DLIe0
- Outcome
- photochemical responsese1
- Direction
- No effectse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“No effects of plant age or prior day’s DLI and a negligible effect of PPFD s 15 or 30 minutes before measurements within days were observed.”
e1“photochemical responses”
t0“Lactuca sativa L.”
Claim · model-written summary
Photon flux density 15 or 30 minutes earlier had a negligible effect within days.
- Taxon
- Lactuca sativa L.Lactuca sativat0
- Treatment
- PPFD s 15 or 30 minutes before measurementse0
- Outcome
- photochemical responsese1
- Qualifier
- negligible effecte0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“a negligible effect of PPFD s 15 or 30 minutes before measurements within days were observed”
e1“photochemical responses”
t0“Lactuca sativa L.”
Claim · model-written summary
For a fixed daily light integral, lower photon flux density for longer periods can increase daily photochemical integral.
- Taxon
- Lactuca sativa L.Lactuca sativat0
- Treatment
- providing light at lower PPFD s for a longer period of timee0
- Outcome
- DPIe0
- Direction
- increasede0
- Qualifier
- For a given DLIe0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“For a given DLI, DPI can be increased by providing light at lower PPFD s for a longer period of time”
t0“Lactuca sativa L.”
Claim · model-written summary
Uniform photon flux density throughout the photoperiod can maximize daily photochemical integral.
- Taxon
- Lactuca sativa L.Lactuca sativat0
- Treatment
- providing light with a uniform PPFD throughout the entire photoperiode0
- Outcome
- DPIe0
- Direction
- maximizede0
- Qualifier
- For a given DLIe0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“For a given DLI, DPI can be increased by providing light at lower PPFD s for a longer period of time, and can be maximized by providing light with a uniform PPFD throughout the entire photoperiod.”
t0“Lactuca sativa L.”
Claim · model-written summary
Lower photon flux density for a longer period reduces the daily light integral needed for a given photochemical integral.
- Taxon
- Lactuca sativa L.Lactuca sativat0
- Treatment
- providing light at lower PPFD s for a longer period of timee1
- Outcome
- DLI required to achieve a given DPIe0
- Direction
- reducede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the DLI required to achieve a given DPI is reduced using these same methods.”
e1“providing light at lower PPFD s for a longer period of time”
t0“Lactuca sativa L.”
Claim · model-written summary
Uniform photon flux density throughout the photoperiod reduces the daily light integral needed for a given photochemical integral.
- Taxon
- Lactuca sativa L.Lactuca sativat0
- Treatment
- providing light with a uniform PPFD throughout the entire photoperiode1
- Outcome
- DLI required to achieve a given DPIe0
- Direction
- reducede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the DLI required to achieve a given DPI is reduced using these same methods.”
e1“providing light with a uniform PPFD throughout the entire photoperiod”
t0“Lactuca sativa L.”
The same questions in other papers
light · physiology: photosynthesis · Lactuca sativa (garden lettuce)Positive and negative results
55 papers in the same direction as this paper · 17 in the opposite direction · 2 reporting no difference from an alternative
- positive
- positive
- positive
71 papers more in this group
See all 75 papers →Claims are grouped by organism, treatment and what was measured or targeted. A paper counts as positive when any of its claims in the group is positive.