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Only Extreme Fluctuations in Light Levels Reduce Lettuce Growth Under Sole Source Lighting.

ABSTRACT: The cost of providing lighting in greenhouses and plant factories can be high. In the case of variable electricity prices, providing most of the light when electricity prices are low can reduce costs. However, it is not clear how plants respond to the resulting fluctuating light levels. We hypothesized that plants that receive a constant photosynthetic photon flux density (PPFD) will produce more biomass than those grown under fluctuating light levels. To understand potential growth reductions caused by fluctuating light levels, we quantified the effects of fluctuating PPFD on the photosynthetic physiology, morphology, and growth of 'Little Gem' and 'Green Salad Bowl' lettuce. Plants were grown in a growth chamber with dimmable white LED bars, alternating between high and low PPFDs every 15 min. The PPFDs were ?400/0, 360/40, 320/80, 280/120, 240/160, and 200/200 ?mol?m^-2?s^-1, with a photoperiod of 16 h and a DLI of ?11.5 mol?m^-2?day^-1 in all treatments. CO₂ was ?800 ?mol?mol^-1. Plants in the 400/0 ?mol?m^-2?s^-1 treatment had ?69% lower A_n,₃₀ (net assimilation averaged over 15 min at high and 15 min at low PPFD) than plants grown at a PPFD of 320/80 ?mol?m^-2?s^-1 (or treatments with smaller PPFD fluctuations). The low A_n,₃₀ in the 400/0, and to a lesser extent the 360/40 ?mol?m^-2?s^-1 treatment was caused by low net assimilation at 360 and 400 ?mol?m^-2?s^-1. Plants grown at 400/0 ?mol?m^-2?s^-1 also had fewer leaves and lower chlorophyll content compared to those in other treatments. The four treatments with the smallest PPFD fluctuations produced plants with similar numbers of leaves, chlorophyll content, specific leaf area (SLA), dry mass, and leaf area. Chlorophyll content, A_n,₃₀, and dry mass were positively correlated with each other. Our results show that lettuce tolerates a wide range of fluctuating PPFD without negative effects on growth and development. However, when fluctuations in PPFD are extreme (400/0 or 360/40 ?mol?m^-2?s^-1), chlorophyll levels and A_n,₃₀ are low, which can explain the low poor growth in these treatments. The ability of lettuce to tolerate a wide range of fluctuating light levels suggests that PPFD can be adjusted in response to variable electricity pricing.

SUBMITTER: Bhuiyan R

PROVIDER: S-EPMC7875872 | biostudies-literature | 2021

REPOSITORIES: biostudies-literature

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Only Extreme Fluctuations in Light Levels Reduce Lettuce Growth Under Sole Source Lighting.

Bhuiyan Ruqayah R van Iersel Marc W MW

Frontiers in plant science 20210128

The cost of providing lighting in greenhouses and plant factories can be high. In the case of variable electricity prices, providing most of the light when electricity prices are low can reduce costs. However, it is not clear how plants respond to the resulting fluctuating light levels. We hypothesized that plants that receive a constant photosynthetic photon flux density (PPFD) will produce more biomass than those grown under fluctuating light levels. To understand potential growth reductions c ...[more]

PMID: 33584773

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Project description:Background:Abiotic stress reduces photosynthetic yield and plant growth, negatively impacting global crop production and is a major constraint faced by agriculture. However, the knowledge on the impact on plants under extremely high irradiance is limited. We present the first in-depth proteomics analysis of plants treated with a method developed by our research group to generate a light gradient using an extremely intense light. Methods:The method consists of utilizing light emitting diodes (LED) to create a single spot at 24,000??mol?m-?2?s-?1 irradiance, generating three light stress levels. A light map and temperature profile were obtained during the light experiment. The proteins expressed in the treated tomato (Solanum lycopersicum, Heinz H1706) leaves were harvested 10?days after the treatment, allowing for the detection of proteins involved in a long-term recovery. A multiplex labeled proteomics method (iTRAQ) was analyzed by LC-MS/MS. Results:A total of 3994 proteins were identified at 1% false discovery rate and matched additional quality filters. Hierarchical clustering analysis resulted in four types of patterns related to the protein expression, with one being directly linked to the increased LED irradiation. A total of 37 proteins were found unique to the least damaged leaf zone, while the medium damaged zone had 372 proteins, and the severely damaged presented unique 1003 proteins. Oxygen evolving complex and PSII complex proteins (PsbH, PsbS, PsbR and Psb28) were found to be abundant in the most damaged leaf zone. This leaf zone presented a protein involved in the salicylic acid response, while it was not abundant in the other leaf zones. The mRNA level of PsbR was significantly lower (1-fold) compared the control in the most damaged zone of the leaf, while Psb28 and PsbH were lower (1-fold) in the less damaged leaf zones. PsbS mRNA abundance in all leaf zones tested presented no statistically significant change from the control. Conclusions:We present the first characterization of the proteome changes caused by an extreme level of high-light intensity (24,000??mol?m-?2?s-?1). The proteomics results show the presence of specific defense responses to each level of light intensity, with a possible involvement of proteins PsbH, Psb28, PsbR, and PsbS.

Dataset Information

Only Extreme Fluctuations in Light Levels Reduce Lettuce Growth Under Sole Source Lighting.

Publications

Only Extreme Fluctuations in Light Levels Reduce Lettuce Growth Under Sole Source Lighting.

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