Abstract
In this work, energy costs for LED (light emitting diodes) lighting of a virtual plant stand exhibiting C3photosynthesis have been calculated via a model considering the quantum demand to build-up dry matter and energy efficiency of state-of-the art LEDs. Optimistic and pessimistic scenarios have been calculated by taking into account uncertainties regarding the H+/ATP stoichiometry of photosynthesis and different management strategies for indoor plant production. Energy costs were between 265 and 606 kWh for a production cycle ranging over 100 days and resulting in 2500 g dry matter per square meter for the optimistic and the pessimistic scenario respectively. The conversion efficiencies from electrical energy to energy bound in phytomass at the end of the production cycle were 2.07 % and 4.72 % (pessimistic and optimistic scenario, respectively). This was lower than the theoretical maximum values calculated for C3 plants that are given as 9.5 % in the literature. However, when the losses that occur during the conversion from electrical energy to light energy were excluded and only the efficiency of the conversion from incident light energy to phyto-energy was calculated, values increased to 4.0 and 9.1 %. The differences between the optimistic and the pessimistic scenario was caused by decreased photorespiration via carbon dioxide fertilization, which increased the conversion efficiencies by 38 %, followed by different assumptions about the H+ requirement for ATP production (34 %) and an increased rate of active absorption of light energy (24 %). Considering cumulative as well as feedback effects of all of the mentioned parameters, the conversion efficiency in the optimistic scenario was 2.3 times higher than in the pessimistic scenario. A system for measuring gas-exchange of whole plants or plant stands was developed in order to be able to investigate and improve the above mentioned management strategies in the future. CO2 sensors and temperature and humidity sensors were used to detect water loss and CO2. Readily available off-the-shelf electronic and mechanical materials were used in order to build a low-cost system that can be used in high throughput experiments. The results indicate that around 90 % of the transpirational water was detected by the system. We conclude that parts of the transpirational water condensed on the surfaces thus not leaving the chamber. When checking the accuracy of the H2O and CO2 sensors using an industry quality infrared gas analyser (IRGA), we found significant deviations from the values given by the IRGA and used this data for calibration of the CO2 sensors. The responses of the CO2-sensors were also linearly coupled to the H2O concentrations (about -0.1 % ppm CO2 / ppm H2O). A regression analysis was performed and the coefficients were used to correct the sensor readings. Since LEDs exhibit a higher energy-to-light ratio when operated at lower light levels, we tested a very small growing gibberellin (GA) deficient super dwarf rice genotype in a climate chamber experiment under different illumination levels and different levels of nitrogen supply to assess its suitability for crop production in artificial environments. A 25 % reduction in illumination lead to a 75 % reduction in yield, mainly due to a 60 % reduction in formed tillers and 20 % reduction in kernel weight, and an 80 % reduction in illumination caused total yield loss. Whereas leaf area under reduced illumination was significantly lower, only marginal changes in the dimensions of single leaves were observed. Photosynthesis at growing light conditions was not different between control plants and plants under 75 % illumination. This was explained by a higher photochemical efficiency under lower light conditions and a reduced mesophyll resistance. Therefore, we conclude that this genotype is an interesting candidate for crop production in vertical plant production systems, especially because of its short stature and the absence of shade avoidance mechanisms, such as leaf elongation, that would complicate production in small-height growing racks under low-light conditions. Nitrogen concentrations of 2.8 and 1.4 mmol L-1 in the nutrient solution lead to no differences in plant growth. We conclude that a nitrogen concentration of 1.4 mmol L-1 is sufficient for this genotype under the light intensities that were applied here. A software tool for simulations of photosynthesis in the python programming language was developed. The software implements a classical Farquhar-von CaemmererBerry (FvCB) model of leaf photosynthesis coupled with a model for the estimation of stomatal behaviour dependent on environmental conditions. We want to emphasize that the use of such models is essential to understand the complex interactions between plant growth, leaf photosynthesis and the environment. Knowledge on those relationships is the key to improve the efficiency of plant production in controlled environments.
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Claims 19
Claim · model-written summary
Energy costs for LED lighting of the virtual plant stand were 265 to 606 kWh per production cycle, for the optimistic and pessimistic scenarios respectively.
Verbatim
e0“energy costs for LED (light emitting diodes) lighting of a virtual plant stand exhibiting C3photosynthesis”
e1“Energy costs were between 265 and 606 kWh for a production cycle ranging over 100 days and resulting in 2500 g dry matter per square meter for the optimistic and the pessimistic scenario respectively”
Claim · model-written summary
Conversion efficiencies from electrical energy to phytomass energy were 2.07 % and 4.72 % in the pessimistic and optimistic scenarios.
Verbatim
e0“energy costs for LED (light emitting diodes) lighting of a virtual plant stand exhibiting C3photosynthesis”
e2“The conversion efficiencies from electrical energy to energy bound in phytomass at the end of the production cycle were 2.07 % and 4.72 % (pessimistic and optimistic scenario, respectively)”
Claim · model-written summary
Carbon dioxide fertilization, via decreased photorespiration, increased the conversion efficiencies by 38 %.
- Taxon
- virtual plant stande0
- Treatment
- carbon dioxide fertilizatione3
- Outcome
- conversion efficienciese3
- Direction
- increasede3
- Value
- 38 %e3
- Qualifier
- decreased photorespiratione3
Not reportedComparator
Verbatim
e0“energy costs for LED (light emitting diodes) lighting of a virtual plant stand exhibiting C3photosynthesis”
e3“decreased photorespiration via carbon dioxide fertilization, which increased the conversion efficiencies by 38 %, followed by different assumptions about the H+ requirement for ATP production (34 %) and an increased rate of active absorption of light energy (24 %)”
Claim · model-written summary
Different assumptions about the H+ requirement for ATP production changed the conversion efficiencies by 34 % in the scenario comparison.
Verbatim
e0“energy costs for LED (light emitting diodes) lighting of a virtual plant stand exhibiting C3photosynthesis”
e3“decreased photorespiration via carbon dioxide fertilization, which increased the conversion efficiencies by 38 %, followed by different assumptions about the H+ requirement for ATP production (34 %) and an increased rate of active absorption of light energy (24 %)”
Claim · model-written summary
An increased rate of active absorption of light energy changed the conversion efficiencies by 24 % in the scenario comparison.
Verbatim
e0“energy costs for LED (light emitting diodes) lighting of a virtual plant stand exhibiting C3photosynthesis”
e3“decreased photorespiration via carbon dioxide fertilization, which increased the conversion efficiencies by 38 %, followed by different assumptions about the H+ requirement for ATP production (34 %) and an increased rate of active absorption of light energy (24 %)”
Claim · model-written summary
With cumulative and feedback effects considered, the conversion efficiency in the optimistic scenario was 2.3 times higher than in the pessimistic scenario.
Verbatim
e0“energy costs for LED (light emitting diodes) lighting of a virtual plant stand exhibiting C3photosynthesis”
e5“the conversion efficiency in the optimistic scenario was 2.3 times higher than in the pessimistic scenario”
Claim · model-written summary
A 25 % reduction in illumination reduced rice yield by 75 %.
- Taxon
- rice
Oryza sativae7 - Material
- gibberellin (GA) deficient super dwarf rice genotypee7
- Treatment
- 25 % reduction in illuminatione6
- Outcome
- yielde6
- Direction
- reductione6
- Value
- 75 %e6
- Setting
- climate chamber experimente7
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e7“we tested a very small growing gibberellin (GA) deficient super dwarf rice genotype in a climate chamber experiment under different illumination levels”
e6“A 25 % reduction in illumination lead to a 75 % reduction in yield, mainly due to a 60 % reduction in formed tillers and 20 % reduction in kernel weight, and an 80 % reduction in illumination caused total yield loss”
Claim · model-written summary
A 25 % reduction in illumination reduced formed tillers of rice by 60 %.
- Taxon
- riceOryza sativae7
- Treatment
- 25 % reduction in illuminatione6
- Outcome
- formed tillerse6
- Direction
- reductione6
- Value
- 60 %e6
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e7“we tested a very small growing gibberellin (GA) deficient super dwarf rice genotype in a climate chamber experiment under different illumination levels”
e6“A 25 % reduction in illumination lead to a 75 % reduction in yield, mainly due to a 60 % reduction in formed tillers and 20 % reduction in kernel weight, and an 80 % reduction in illumination caused total yield loss”
Claim · model-written summary
A 25 % reduction in illumination reduced rice kernel weight by 20 %.
- Taxon
- riceOryza sativae7
- Treatment
- 25 % reduction in illuminatione6
- Outcome
- kernel weighte6
- Direction
- reductione6
- Value
- 20 %e6
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e7“we tested a very small growing gibberellin (GA) deficient super dwarf rice genotype in a climate chamber experiment under different illumination levels”
e6“A 25 % reduction in illumination lead to a 75 % reduction in yield, mainly due to a 60 % reduction in formed tillers and 20 % reduction in kernel weight, and an 80 % reduction in illumination caused total yield loss”
Claim · model-written summary
An 80 % reduction in illumination caused total yield loss of rice.
- Taxon
- riceOryza sativae7
- Treatment
- 80 % reduction in illuminatione6
- Outcome
- total yield losse6
- Direction
- decreaseinferrede6
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e7“we tested a very small growing gibberellin (GA) deficient super dwarf rice genotype in a climate chamber experiment under different illumination levels”
e6“A 25 % reduction in illumination lead to a 75 % reduction in yield, mainly due to a 60 % reduction in formed tillers and 20 % reduction in kernel weight, and an 80 % reduction in illumination caused total yield loss”
Claim · model-written summary
Under reduced illumination, rice leaf area was significantly lower.
- Taxon
- riceOryza sativae7
- Treatment
- reduced illuminatione4
- Outcome
- leaf areae4
- Direction
- significantly lowere4
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e7“we tested a very small growing gibberellin (GA) deficient super dwarf rice genotype in a climate chamber experiment under different illumination levels”
e4“Whereas leaf area under reduced illumination was significantly lower, only marginal changes in the dimensions of single leaves were observed”
Claim · model-written summary
Under reduced illumination, the dimensions of single rice leaves showed only marginal changes.
- Taxon
- riceOryza sativae7
- Treatment
- reduced illuminatione4
- Outcome
- dimensions of single leavese4
- Direction
- no_changeinferrede4
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e7“we tested a very small growing gibberellin (GA) deficient super dwarf rice genotype in a climate chamber experiment under different illumination levels”
e4“Whereas leaf area under reduced illumination was significantly lower, only marginal changes in the dimensions of single leaves were observed”
Claim · model-written summary
Photosynthesis at growing light conditions was not different between control rice plants and plants under 75 % illumination.
- Taxon
- riceOryza sativae7
- Treatment
- 75 % illuminatione4
- Outcome
- Photosynthesis at growing light conditionse4
- Direction
- not differente4
- Comparator
- control plantse4
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e7“we tested a very small growing gibberellin (GA) deficient super dwarf rice genotype in a climate chamber experiment under different illumination levels”
e4“Photosynthesis at growing light conditions was not different between control plants and plants under 75 % illumination”
Claim · model-written summary
The authors explain the unchanged photosynthesis under low light by a higher photochemical efficiency and a reduced mesophyll resistance.
- Taxon
- riceOryza sativae7
- Outcome
- Photosynthesis at growing light conditionse4
- Qualifier
- a higher photochemical efficiency under lower light conditions and a reduced mesophyll resistancee3
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e7“we tested a very small growing gibberellin (GA) deficient super dwarf rice genotype in a climate chamber experiment under different illumination levels”
e4“Photosynthesis at growing light conditions was not different between control plants and plants under 75 % illumination”
e3“This was explained by a higher photochemical efficiency under lower light conditions and a reduced mesophyll resistance”
Claim · model-written summary
Nitrogen concentrations of 2.8 and 1.4 mmol L-1 gave no differences in rice plant growth.
- Taxon
- riceOryza sativae7
- Treatment
- Nitrogen concentrations of 2.8 and 1.4 mmol L-1e4
- Outcome
- plant growthe4
- Direction
- no_changeinferrede4
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e7“we tested a very small growing gibberellin (GA) deficient super dwarf rice genotype in a climate chamber experiment under different illumination levels”
e4“Nitrogen concentrations of 2.8 and 1.4 mmol L-1 in the nutrient solution lead to no differences in plant growth”
Claim · model-written summary
The authors conclude that 1.4 mmol L-1 nitrogen is sufficient for this rice genotype at the light intensities applied.
- Taxon
- riceOryza sativae7
- Outcome
- a nitrogen concentration of 1.4 mmol L-1 is sufficiente4
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e7“we tested a very small growing gibberellin (GA) deficient super dwarf rice genotype in a climate chamber experiment under different illumination levels”
e4“We conclude that a nitrogen concentration of 1.4 mmol L-1 is sufficient for this genotype under the light intensities that were applied here”
Claim · model-written summary
The gas-exchange system detected around 90 % of the transpirational water.
Verbatim
e6“A system for measuring gas-exchange of whole plants or plant stands was developed”
e5“The results indicate that around 90 % of the transpirational water was detected by the system”
Claim · model-written summary
The H2O and CO2 sensors of the gas-exchange system showed significant deviations from the values of an infrared gas analyser.
Verbatim
e6“A system for measuring gas-exchange of whole plants or plant stands was developed”
e5“When checking the accuracy of the H2O and CO2 sensors using an industry quality infrared gas analyser (IRGA), we found significant deviations from the values given by the IRGA”
Claim · model-written summary
The CO2 sensor responses were linearly coupled to H2O concentrations, at about -0.1 % ppm CO2 per ppm H2O.
- Taxon
- plant standse6
- Treatment
- H2O concentrationse5
- Outcome
- responses of the CO2-sensorse5
- Value
- -0.1 % ppm CO2 / ppm H2Oe5
Not reportedDirection
Verbatim
e6“A system for measuring gas-exchange of whole plants or plant stands was developed”
e5“The responses of the CO2-sensors were also linearly coupled to the H2O concentrations (about -0.1 % ppm CO2 / ppm H2O)”
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