Abstract
Pakchoi, a popular leafy vegetable in China, is expected to be planted in plant factories with artificial lighting (PFALs). In order to examine the effects of different red and blue light ratios (R:B ratio) on growth, photosynthesis, and absorption spectrum of plant leaves, and to analyze the energy use efficiency, the pakchoi (Brassica Chinensis L. cv. Xiazhijiao) was cultivated hydroponically under white LEDs with R:B ratios of 0.9 (L0.9) and 1.8 (L1.8), white plus red LEDs with R:B ratios of 2.7 (L2.7) and 4.0 (L4.0) for 40 d, respectively. The results showed that the leaf length and width were significantly greater in the L0.9 treatment than in other treatments, and the dry weight per plant increased by over 33% when R:B ratio decreased from 4.0 to 0.9. The net photosynthesis rates of pakchoi leaves ranged from 9.2 to 9.6 μmol/(m2·s) under different lighting conditions, which had no significant difference. The biggest difference in the spectrum absorptance of pakchoi leaves was expressed in green light waveband, and the highest absorption of plant leaves was under L0.9 and L1.8 treatments. The light energy use efficiency (LUE), photon yield (PY), and energy yield (EY) in L0.9 were over 25% higher than that in the other treatments, while there was no significant difference in the electrical energy use efficiency (EUE). In conclusion, an optimal light quality to cultivate pakchoi in PFALs was the white LEDs with R:B ratio of 0.9, and this finding could provide a promising lighting environment to hydroponic pakchoi yield and energy use efficiency. Keywords: pakchoi, R:B ratio, yield, absorption spectrum, energy use efficiency DOI: 10.25165/j.ijabe.20221503.7362 Citation: Li Y N, Liu N, Ji F, He D X. Optimal red:blue ratio of full spectrum LEDs for hydroponic pakchoi cultivation in plant factory. Int J Agric & Biol Eng, 2022; 15(3): 72–77.
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Claims 10
Claim · model-written summary
Pakchoi leaf length and width were greater at L0.9 than under other lights.
Verbatim
e0“the leaf length and width were significantly greater in the L0.9 treatment than in other treatments”
t0“Optimal red:blue ratio of full spectrum LEDs for hydroponic pakchoi cultivation in plant factory”
Claim · model-written summary
Pakchoi dry weight increased by over 33% as the red:blue ratio fell from 4.0 to 0.9.
Verbatim
e0“the dry weight per plant increased by over 33% when R:B ratio decreased from 4.0 to 0.9”
t0“Optimal red:blue ratio of full spectrum LEDs for hydroponic pakchoi cultivation in plant factory”
Claim · model-written summary
Pakchoi net photosynthesis did not differ significantly across lighting conditions.
- Taxon
- pakchoie0
- Treatment
- different lighting conditionse0
- Outcome
- net photosynthesis ratese0
- Direction
- no significant differencee0
- Value
- 9.2 to 9.6 μmol/(m2·s)e0
Not reportedComparator
Verbatim
e0“The net photosynthesis rates of pakchoi leaves ranged from 9.2 to 9.6 μmol/(m2·s) under different lighting conditions, which had no significant difference.”
Claim · model-written summary
The largest spectral absorptance difference in pakchoi leaves occurred in the green waveband.
Verbatim
e0“The biggest difference in the spectrum absorptance of pakchoi leaves was expressed in green light waveband”
Claim · model-written summary
Pakchoi leaves had highest absorption under L0.9 and L1.8 lights.
- Taxon
- pakchoit0
- Treatment
- L0.9 and L1.8 treatmentse0
- Outcome
- absorption of plant leavese0
- Direction
- higheste0
Not reportedComparator
Verbatim
e0“the highest absorption of plant leaves was under L0.9 and L1.8 treatments”
t0“Optimal red:blue ratio of full spectrum LEDs for hydroponic pakchoi cultivation in plant factory”
Claim · model-written summary
Light energy use efficiency at L0.9 exceeded other treatments by over 25%.
Verbatim
e0“The light energy use efficiency (LUE), photon yield (PY), and energy yield (EY) in L0.9 were over 25% higher than that in the other treatments”
t0“Optimal red:blue ratio of full spectrum LEDs for hydroponic pakchoi cultivation in plant factory”
Claim · model-written summary
Photon yield at L0.9 exceeded other treatments by over 25%.
Verbatim
e0“The light energy use efficiency (LUE), photon yield (PY), and energy yield (EY) in L0.9 were over 25% higher than that in the other treatments”
t0“Optimal red:blue ratio of full spectrum LEDs for hydroponic pakchoi cultivation in plant factory”
Claim · model-written summary
Energy yield at L0.9 exceeded other treatments by over 25%.
Verbatim
e0“The light energy use efficiency (LUE), photon yield (PY), and energy yield (EY) in L0.9 were over 25% higher than that in the other treatments”
t0“Optimal red:blue ratio of full spectrum LEDs for hydroponic pakchoi cultivation in plant factory”
Claim · model-written summary
Electrical energy use efficiency did not differ significantly between lighting treatments.
Not reportedTreatmentComparator
Verbatim
e0“there was no significant difference in the electrical energy use efficiency (EUE)”
t0“Optimal red:blue ratio of full spectrum LEDs for hydroponic pakchoi cultivation in plant factory”
Claim · model-written summary
The authors recommend white LEDs with a red:blue ratio of 0.9 for pakchoi cultivation.
Verbatim
e0“an optimal light quality to cultivate pakchoi in PFALs was the white LEDs with R:B ratio of 0.9”
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