Effects of Light-Emitting Diode Grow Lights on the Growth and Yield of Hong-Tai Bok Choy and Baby Bok Choy
Round 1
Reviewer 1 Report (Previous Reviewer 3)
Comments and Suggestions for AuthorsThe resubmitted manuscript has been significantly revised in response to the previous comments, and the quality of the manuscript has improved. However, as noted in the prior comment, the scope of research presented in this manuscript remains too limited, and the depth of investigation is insufficient to warrant publication as a research article in horticulturae. The authors need to conduct more extensive and in-depth studies, such as measuring additional physiological indices, related enzyme activities, and active substance contents. Alternatively, the authors may consider publishing the current findings in another format (e.g., a communication or an abstract).
- Please verify the significance test results for Fresh Weight in Table 5.
- Error in Table 2: "13.72±155".
- The authors need to select more appropriate photographs. For instance, in Tables 2 and 4, the 'Number of Leaves' for Treatment 2 of the two Bok Choy varieties shows no significant difference compared to Treatments 1 and 3, yet Figure 3 shows an obvious discrepancy that does not align with the average leaf number.
- The SPAD values in Tables 2 and 4 require annotations.
- Line 172: "13±55" is inconsistent with the data presented in Table 2.
- Line 125: "Fresh weight, root length, and dry weight of shoots and roots were determined". The data are not presented in the manuscript.
Author Response
Reviewer 1 Comments and Suggestions
The resubmitted manuscript has been significantly revised in response to the previous comments, and the quality of the manuscript has improved. However, as noted in the prior comment, the scope of research presented in this manuscript remains too limited, and the depth of investigation is insufficient to warrant publication as a research article in horticulturae. The authors need to conduct more extensive and in-depth studies, such as measuring additional physiological indices, related enzyme activities, and active substance contents. Alternatively, the authors may consider publishing the current findings in another format (e.g., a communication or an abstract).
1.1 Please verify the significance test results for Fresh Weight in Table 5.
Answer: Already verified the significance test results for Fresh Weight in Table 5, abnormalities found and already corrected in the Fresh Weight column.
1.2 Error in Table 2: "13.72±155".
Answer: Already revised to the correct data “13.72±1.55”.
1.3 The authors need to select more appropriate photographs. For instance, in Tables 2 and 4, the 'Number of Leaves' for Treatment 1 of the two Bok Choy varieties shows no significant difference compared to Treatments 1 and 3, yet Figure 3 shows an obvious discrepancy that does not align with the average leaf number.
Answer: Already revised the photographs of Treatment 1 in Figure 3.
1.4 The SPAD values in Tables 2 and 4 require annotations.
Answer: Already added annotations of the SPAD values in Tables 2 and 4.
1.5 Line 172: "13±55" is inconsistent with the data presented in Table 2.
Answer: Already revised the data presented in Line 172 to “13.72±1.55”.
1.6 Line 125: "Fresh weight, root length, and dry weight of shoots and roots were determined". The data are not presented in the manuscript.
Answer: Already revised to “Fresh, and dry weight of shoots were determined”.
Author Response File: 
Author Response.pdf
Reviewer 2 Report (Previous Reviewer 2)
Comments and Suggestions for AuthorsAfter reviewing again, I found that the author has carefully revised and improved the manuscript based on the previous review comments, and I have no new revision suggestions or comments.
Author Response
Thank you very much for the suggestions and comments.
Reviewer 3 Report (Previous Reviewer 1)
Comments and Suggestions for Authors- 1. The introduction is generally relevant to controlled-environment agriculture; the logical link between background -> research gap -> verifiable goals needs to be strengthened.
1) It also fails to justify why the two types of "bokchoi" are expected to differ.
2) Although the stated goal is to investigate the "effects of commercial LED lamps" compared to sunlight, the introduction only talks about "spectral optimization" without any mention of how the spectrum will be quantified (e.g., spectroradiometer-based SPD, DLI). What do you think?
- 2. The study uses a CRD with five treatments; three hydroponic channels per treatment; each channel contains 10 plants.
1) This immediately raises the risk of pseudo-replication unless the hydroponic channel (not the individual plant) is treated as the experimental unit for the treatment effect.
2) Were plants analyzed as independent replicates (n = 30 per treatment) or were channel means used (n = 3 per treatment)? The manuscript currently does not specify.
- 3. Photoperiod differs between sunlight and LED treatments. Sunlight treatment is described as a 12 h photoperiod, whereas LED treatments use a 16 h photoperiod (and are held at 25 ± 2 °C).
1) This means the “sunlight vs LED” comparison is simultaneously a photoperiod/DLI and temperature regime comparison, not just a light source comparison.
2) If the sunlight condition truly followed natural day length, how was it set to 12 h?
3) If artificial shading/blackout was used, this must be described.
4) If the LED environment was temperature-controlled but sunlight was not, temperature becomes another confound.
- 4. Light intensity is not standardized across LED fixtures.
1) Treatments 3-5 used four fixtures per channel, while Treatment 2 used one fixture per channel.
2) This makes it very hard to interpret differences as "spectral" rather than "dose / intensity + hardware distribution".
3) Sunlight PPFD / PAR values appear to be taken from literature, not measured in situ. Table 1 explicitly notes sunlight PAR / PPFD data from Balázs and Kovács, while "measured illuminance" is given for sunlight.
4) Lux is not a plant-meaningful radiometric metric. For plant lighting, PPFD and DLI at canopy height in the actual experimental location are essential.
-5. The statistical analysis paragraph includes a statement about "sweet potatoes’ agronomic traits and economic yield", which is unrelated to this experiment.
1) This is not a minor typo; it suggests template text was left in place, and it undermines confidence in the rigor of analysis reporting.
- 6. Claims about "LEDs improving biomass relative to sunlight" need to acknowledge Treatment 2. For Baby Bok Choy, the lowest biomass is in Treatment 2 (LED), and sunlight is not always the lowest.
1) For Hong-Tai Bok Choy, Treatment 1 (sunlight) and Treatment 2 are both low, but the conclusion should be framed as "some commercial LED fixtures increased biomass under our conditions" rather than "LEDs (as a category) outperform sunlight".
- 7. Unclear n and SD meaning. Tables report mean ± SD.
1) But if the experimental unit is a channel (n = 3), SD would be based on three values; if the plant is treated as a replicate (n = 30), SD is based on plants but would be pseudo-replicated unless nesting is addressed.
2) The Results must state n unambiguously and align it with the design.
-8. In Baby Bok Choy, sunlight has the lowest a* (less negative) and the highest b* (more yellow) (Table 5), yet the text interprets sunlight as enhancing "leaf greenness and coloration".
1) Because a* is typically the green-red axis (more negative = greener), the manuscript should reconcile whether "greenness" is supported by a*, SPAD, or visual judgment, and avoid conflating "yellow-green" with "darker green".
9. The manuscript acknowledges key limitations but does not adjust conclusions accordingly.
1) It explicitly states that the study cannot separate intensity from spectral amd structural effects, especially in sunlight.
2) Yet later, it attributes performance differences to spectral mechanisms (e.g., phytochrome-mediated red / far-red responses) without presenting measured spectra (SPD, R:FR, blue fraction) at canopy height.
3) If the lamps are to be compared as commercial "systems", then mechanistic spectral claims should be toned down or supported by actual spectral measurements.
- 10. Photoinhibition / saturation interpretation needs evidence.
1) The Discussion proposes that sunlight may have exceeded light saturation and caused limited yield despite high SPAD, implying photoinhibition avoidance under LED.
2) This is a strong physiological claim, but no photosynthetic measurements (A-PPFD, chlorophyll fluorescence, leaf temperature, midday depression) are presented. Without those, this should be framed as a hypothesis rather than an inferred mechanism.
- 11. The trade-off between yield and quality is under-defined. The manuscript concludes a trade-off between biomass and leaf quality, but "quality" is operationalized only as SPAD and CIELAB (or CIE L*a*b*).
1) If "quality" is meant in a horticultural/market sense, consider including nutritional quality or sensory/marketability metrics (nitrate, vitamin C, carotenoids, phenolics) or soften the claim to "color indices differed".
-12. The Conclusions state cultivar-specific recommendations (e.g., Treatment 5 best for Hong-Tai; Treatments 3 and 5 for Baby) and emphasize that SPAD does not correspond with biomass.
1) Those statements are directionally consistent with the reported means, but they should be reworded to match what was actually tested:
2) If photoperiod and DLI differ between sunlight and LED treatments, the conclusion should not imply a clean "LED versus sunlight" causal inference.
3)If intensity differs substantially among LED fixtures, the conclusion should avoid implying that spectral type alone drove the differences.
4) Suggested reframing, instead of "optimal spectral requirements differed", consider -> "Under the specific fixture configurations, photoperiods, and intensities used here, certain commercial LED systems increased biomass relative to the sunlight condition, and responses differed between the two bok choy types".
- 13. Please ensure that the references in the reference list and the papers cited in the main text of the manuscript are correctly matched.
1) Among studies using white LEDs that exhibit Kelvin values (K), no papers on "Coleus" and "Tillandsia ionantha" were found in the reference list (they are mentioned in the main text but not in the reference list). Studies highlighting the color temperature of white LEDs are relatively rare, so research and linking to relevant papers are necessary.
-14. Fig. 1 raises serious ethical concerns. Unauthorized use of commercial images in this manuscript can lead to serious consequences... Furthermore, the spectral distribution image in Caption A does not appear to have been created by the authors themselves. Please use an alternative image created by the authors.
Thank you.
Author Response
Reviewer 3 Comments and Suggestions
- The introduction is generally relevant to controlled-environment agriculture; the logical link between background -> research gap -> verifiable goals needs to be strengthened.
1) It also fails to justify why the two types of "bokchoi" are expected to differ.
2) Although the stated goal is to investigate the "effects of commercial LED lamps" compared to sunlight, the introduction only talks about "spectral optimization" without any mention of how the spectrum will be quantified (e.g., spectroradiometer-based SPD, DLI). What do you think?
Answer: Already revised the introduction part. Because commercially available LED lights already specify their spectrum range, the light spectrum is not measured again.
- The study uses a CRD with five treatments; three hydroponic channels per treatment; each channel contains 10 plants.
1) This immediately raises the risk of pseudo-replication unless the hydroponic channel (not the individual plant) is treated as the experimental unit for the treatment effect.
2) Were plants analyzed as independent replicates (n = 30 per treatment) or were channel means used (n = 3 per treatment)? The manuscript currently does not specify.
Answer: Already added in 2.1.
- Photoperiod differs between sunlight and LED treatments. Sunlight treatment is described as a 12 h photoperiod, whereas LED treatments use a 16 h photoperiod (and are held at 25 ± 2 °C).
1) This means the “sunlight vs LED” comparison is simultaneously a photoperiod/DLI and temperature regime comparison, not just a light source comparison.
Answer: Already revised the results by not comparing to sunlight. But use the sunlight as a reference treatment.
2) If the sunlight condition truly followed natural day length, how was it set to 12 h?
Answer: The experiment was run in the summer season, sunrise starts at 6.00 am and sunset at 18.00 pm. Then the plants get the natural day length for 12 h.
3) If artificial shading/blackout was used, this must be described.
Answer: No artificial shading.
4) If the LED environment was temperature-controlled but sunlight was not, temperature becomes another confound.
Answer: Already revised the results by not comparing to sunlight. But use the sunlight as a reference treatment.
- Light intensity is not standardized across LED fixtures.
1) Treatments 2-4 used four fixtures per channel, while Treatment 1 used one fixture per channel.
Answer: Based on the size of the LED, LED Treatment 1 is long 95 cm, while the LED Treatments 2-4 are long 50 cm, then it needs to use four fixtures to complete the channel.
2) This makes it very hard to interpret differences as "spectral" rather than "dose / intensity + hardware distribution".
Answer: The same spectrum but light intensity increase.
3) Sunlight PPFD / PAR values appear to be taken from literature, not measured in situ. Table 1 explicitly notes sunlight PAR / PPFD data from Balázs and Kovács, while "measured illuminance" is given for sunlight.
Answer: Our experiment uses the data of PPFD / PAR from Balázs and Kovács, as we do not have the equipment to measure.
4) Lux is not a plant-meaningful radiometric metric. For plant lighting, PPFD and DLI at canopy height in the actual experimental location are essential.
Answer: Already measured and added PPFD and DLI in Table 1.
- The statistical analysis paragraph includes a statement about "sweet potatoes’ agronomic traits and economic yield", which is unrelated to this experiment.
1) This is not a minor typo; it suggests template text was left in place, and it undermines confidence in the rigor of analysis reporting.
Answer: Already revised to the Bok Choy traits.
- Claims about "LEDs improving biomass relative to sunlight" need to acknowledge Treatment 2. For Baby Bok Choy, the lowest biomass is in Treatment 2 (LED), and sunlight is not always the lowest.
1) For Hong-Tai Bok Choy, Treatment 1 (sunlight) and Treatment 2 are both low, but the conclusion should be framed as "some commercial LED fixtures increased biomass under our conditions" rather than "LEDs (as a category) outperform sunlight".
Answer: Already revised the results part of both Bok Choy.
- Unclear n and SD meaning. Tables report mean ± SD.
1) But if the experimental unit is a channel (n = 3), SD would be based on three values; if the plant is treated as a replicate (n = 30), SD is based on plants but would be pseudo-replicated unless nesting is addressed.
Answer: (n = 3), SD based on three values.
2) The Results must state n unambiguously and align it with the design.
Answer: Already revised in 2.1.
- In Baby Bok Choy, sunlight has the lowest a* (less negative) and the highest b* (more yellow) (Table 5), yet the text interprets sunlight as enhancing "leaf greenness and coloration".
1) Because a* is typically the green-red axis (more negative = greener), the manuscript should reconcile whether "greenness" is supported by a*, SPAD, or visual judgment, and avoid conflating "yellow-green" with "darker green".
Answer: Since we do not compare sunlight with the LED, the results in part 3.1.2 were revised.
- The manuscript acknowledges key limitations but does not adjust conclusions accordingly.
1) It explicitly states that the study cannot separate intensity from spectral amd structural effects, especially in sunlight.
2) Yet later, it attributes performance differences to spectral mechanisms (e.g., phytochrome-mediated red / far-red responses) without presenting measured spectra (SPD, R:FR, blue fraction) at canopy height.
3) If the lamps are to be compared as commercial "systems", then mechanistic spectral claims should be toned down or supported by actual spectral measurements.
Answer: Already revised the conclusions part.
- Photoinhibition / saturation interpretation needs evidence.
1) The Discussion proposes that sunlight may have exceeded light saturation and caused limited yield despite high SPAD, implying photoinhibition avoidance under LED.
2) This is a strong physiological claim, but no photosynthetic measurements (A-PPFD, chlorophyll fluorescence, leaf temperature, midday depression) are presented. Without those, this should be framed as a hypothesis rather than an inferred mechanism.
Answer: Already revised the Discussion part.
- The trade-off between yield and quality is under-defined. The manuscript concludes a trade-off between biomass and leaf quality, but "quality" is operationalized only as SPAD and CIELAB (or CIE L*a*b*).
1) If "quality" is meant in a horticultural/market sense, consider including nutritional quality or sensory/marketability metrics (nitrate, vitamin C, carotenoids, phenolics) or soften the claim to "color indices differed".
Answer: Already revised in the Discussion part.
- The Conclusions state cultivar-specific recommendations (e.g., Treatment 5 best for Hong-Tai; Treatments 3 and 5 for Baby) and emphasize that SPAD does not correspond with biomass.
1) Those statements are directionally consistent with the reported means, but they should be reworded to match what was actually tested:
2) If photoperiod and DLI differ between sunlight and LED treatments, the conclusion should not imply a clean "LED versus sunlight" causal inference.
3) If intensity differs substantially among LED fixtures, the conclusion should avoid implying that spectral type alone drove the differences.
4) Suggested reframing, instead of "optimal spectral requirements differed", consider -> "Under the specific fixture configurations, photoperiods, and intensities used here, certain commercial LED systems increased biomass relative to the sunlight condition, and responses differed between the two bok choy types".
Answer: Already revised The Conclusions part.
- Please ensure that the references in the reference list and the papers cited in the main text of the manuscript are correctly matched.
1) Among studies using white LEDs that exhibit Kelvin values (K), no papers on "Coleus" and "Tillandsia ionantha" were found in the reference list (they are mentioned in the main text but not in the reference list). Studies highlighting the color temperature of white LEDs are relatively rare, so research and linking to relevant papers are necessary.
Answer: Already added the reference of “Park, B.G.; Lee, J.H.; Shin, E.J.; Kim, E.A.; Nam, S.Y. Light Quality Influence on Growth Performance and Physiological Activity of Coleus Cultivars. Int. J. Plant Biol. 2024, 15, 807-826. https://doi.org/10.3390/ijpb15030058”
- Fig. 1 raises serious ethical concerns. Unauthorized use of commercial images in this manuscript can lead to serious consequences... Furthermore, the spectral distribution image in Caption A does not appear to have been created by the authors themselves. Please use an alternative image created by the authors.
Answer: Already revised Figure 1.
Author Response File: Author Response.pdf
Round 2
Reviewer 3 Report (Previous Reviewer 1)
Comments and Suggestions for AuthorsThe manuscript has been significantly improved, and some unclear points have been clarified. However, several important revisions remain. Authors should discuss the recommendations below among themselves and make revisions.
- 1. Describe exactly how sunlight was set to 12 h (blackout / shading? fixed schedule?).
- 2.Reframe conclusions to avoid causal claims like "LED outperforms sunlight" and instead limit claims to the specific configurations and environments used.
- 3. Table 1 states PPFD, DLI, and CCT were measured using a Photone smartphone app at canopy height, while sunlight PAR / PPFD are partly referenced to literature and not necessarily measured in situ. Additionally, Table 1 contains both PPFD (μmol) and measured PPFD, but they are dramatically inconsistent (e.g., Treatment 1: PPFD 1003 vs measured 170). What do you think?
1) If any values are derived / converted, clearly state the calculation method and inputs.
2) If mechanistic spectral claims are retained, provide measured spectra (SPD) or, at a minimum, quantitative spectral descriptors (R:FR, blue fraction, etc.) at canopy height.
- 4. The methods specify that Treatment 1 used one fixture per channel, whereas Treatments 2-4 used four fixtures per channel. This strongly suggests that differences may reflect dose / intensity and light distribution / hardware layout, not "spectrum" alone. The manuscript also explicitly acknowledges that it cannot separate intensity, spectrum, and structural effects.
1) Tone down any statements implying spectral causality.
2) Present findings as "commercial lighting systems under the tested setups", unless a matched-PPFD design or additional measurements are added.
- 5. In Table 6, Fresh weight, a* shows r = -0.0278 yet is marked as significant (* p ≤ 0.05). In Table 7, similarly small correlations are marked significant, e.g., Leaf length-Canopy r = 0.1492 and SPAD-b* r = -0.0869.
1)These values cannot reasonably be significant under channel-level n (n = 3 per treatment), and are unlikely even under moderate n unless something is very inconsistent.
2) Clearly define what constitutes one observation in the correlation analysis (channel means versus individual plants).
3) If individual plants were used, the analysis must address nesting / non-independence (mixed models or appropriate hierarchical structure), otherwise it reintroduces pseudo-replication.
4) Recompute p-values and correct the asterisk logic and legend.
- 6. The discussion states that higher b* under sunlight implies "darker green leaves". But b* typically represents the yellow-blue axis (more positive = more yellow), not "darker green".
1) Greenness is more directly reflected by a* (green–red axis; more negative often indicates greener), plus SPAD and other evidence.
2) Reconcile "greenness" using appropriate indices (a*, SPAD, possibly ΔE*), and avoid equating higher b* with darker green.
-7. Mechanistic claims (e.g., phytochrome-mediated red / far-red explanations) remain overreaching without spectral measurements. The discussion attributes performance to "red / far-red richness" and phytochrome-mediated effects.
1) But no measured SPD / R:FR at canopy height is provided, and the manuscript admits it cannot separate dose / spectrum / structure.
2) Downgrade mechanistic statements to hypotheses, or provide the necessary spectral measurements to support them.
- 8. The introduction cites a Tillandsia ionantha result as reference [31]. But reference [31] appears to be a different topic (J. Exp. Bot. 2010; not evidently Tillandsia..). This suggests citation misalignment or an incorrect reference.
1) If you want to expand the discussion on white LEDs based on Kelvin (K), it may be more beneficial to cover previous studies (e.g., https://doi.org/10.11628/ksppe.2025.28.6.799) on horticultural crops that use leaves rather than the succulent species of Tillandsia.
- 9. Fig. 1 caption includes "Modified from Tranyton LED Lighting…shorturl…".
1) Simply stating "modified from" does not resolve permission issues for commercial imagery and spectral plots not generated by the authors.
2)Replace Fig. 1 with an author-created figure (ideally based on measured SPD) or provide explicit permission consistent with the journal’s policy.
- 10. Table 1 title uses "different plant species", which reads like template residue; revise for accuracy.
- 11. Typographical errors remain (e.g., "Bok Choyies’", "coef icients").
Thank you.
Author Response
Comments and Suggestions
- Describe exactly how sunlight was set to 12 h (blackout / shading? fixed schedule?).
Answer: Already added more information of fixed schedule in 2.2.
- Reframe conclusions to avoidcausal claims like "LED outperforms sunlight" and instead limit claims to the specific configurations and environments used.
Answer: Already revised the conclusions part.
- Table 1 statesPPFD, DLI, and CCT were measured using a Photone smartphone app at canopy height, while sunlight PAR / PPFD are partly referenced to literature and not necessarily measured in situ. Additionally, Table 1 contains both PPFD (μmol) and measured PPFD, but they are dramatically inconsistent (e.g., Treatment 1: PPFD 1003 vs measured 170). What do you think?
1) If any values are derived / converted, clearly state the calculation method and inputs.
2) If mechanistic spectral claims are retained, provide measured spectra (SPD) or, at a minimum, quantitative spectral descriptors (R:FR, blue fraction, etc.) at canopy height.
Answer: Already revised Table 1.
- The methods specify that Treatment 1 used one fixture per channel, whereas Treatments 2-4 used four fixtures per channel. This strongly suggests that differences may reflect dose / intensity and light distribution / hardware layout, not "spectrum" alone. The manuscript also explicitly acknowledges that it cannot separate intensity, spectrum, and structural effects.
1) Tone down any statements implying spectral causality.
2) Present findings as "commercial lighting systems under the tested setups", unless a matched-PPFD design or additional measurements are added.
Answer: Already revised the discussion part.
- In Table 6, Fresh weight, a* shows r = -0.0278 yet is marked as significant (* p ≤ 0.05). In Table 7, similarly small correlations are marked significant, e.g., Leaf length-Canopy r = 0.1492 and SPAD-b* r = -0.0869.
1)These values cannot reasonably be significant under channel-level n (n = 3 per treatment), and are unlikely even under moderate n unless something is very inconsistent.
2) Clearly define what constitutes one observation in the correlation analysis (channel means versus individual plants).
3) If individual plants were used, the analysis must address nesting / non-independence (mixed models or appropriate hierarchical structure), otherwise it reintroduces pseudo-replication.
4) Recompute p-values and correct the asterisk logic and legend.
Answer: Already revised Tables 6 and 7 with the explanation.
- The discussion states that higher b* under sunlight implies "darker green leaves". But b* typically represents the yellow-blue axis (more positive = more yellow), not "darker green".
1) Greenness is more directly reflected by a* (green–red axis; more negative often indicates greener), plus SPAD and other evidence.
2) Reconcile "greenness" using appropriate indices (a*, SPAD, possibly ΔE*), and avoid equating higher b* with darker green.
Answer: Already revised the discussion part.
- Mechanistic claims (e.g., phytochrome-mediated red / far-red explanations) remain overreaching without spectral measurements. The discussion attributes performance to "red / far-red richness" and phytochrome-mediated effects.
1) But no measured SPD / R:FR at canopy height is provided, and the manuscript admits it cannot separate dose / spectrum / structure.
2) Downgrade mechanistic statements to hypotheses, or provide the necessary spectral measurements to support them.
Answer: Already revised the discussion part.
- The introduction cites a Tillandsia ionantha result as reference [31]. But reference [31] appears to be a different topic (J. Exp. Bot. 2010; not evidently Tillandsia..). This suggests citation misalignment or an incorrect reference.
1) If you want to expand the discussion on white LEDs based on Kelvin (K), it may be more beneficial to cover previous studies (e.g., https://doi.org/10.11628/ksppe.2025.28.6.799) on horticultural crops that use leaves rather than the succulent species of Tillandsia.
Answer: Already revised the Introduction part.
- Fig. 1 caption includes "Modified from Tranyton LED Lighting…shorturl…".
1) Simply stating "modified from" does not resolve permission issues for commercial imagery and spectral plots not generated by the authors.
2)Replace Fig. 1 with an author-created figure (ideally based on measured SPD) or provide explicit permission consistent with the journal’s policy.
Answer: I have obtained permission to use the images of Figure 1 from Tranyton LED Lighting: https://shorturl.at/ZVmjD [37].
- Table 1 title uses "different plant species", which reads like template residue; revise for accuracy.
Answer: Already revised Table 1 title.
- Typographical errors remain (e.g., "Bok Choyies’", "coef icients").
Answer: Already revised “Bok Choyies” in 3.2 and Already checked “coef icients” but did not found the wrong word.
Author Response File: Author Response.pdf
This manuscript is a resubmission of an earlier submission. The following is a list of the peer review reports and author responses from that submission.
Round 1
Reviewer 1 Report
Comments and Suggestions for Authors- 1. The text emphasizes that commercial LED products are widely available in Thailand and mentions previous local work on lettuce under commercial LEDs.
1) Yet, the final sentence of the Introduction states that this study aims to investigate "the effects of commercially available LED light intensity" on "Hong-tai" and "Baby Bok Choy" compared to natural light. This is unnatural.
2. Could the authors sharpen the Introduction so that the precise novelty is stated explicitly?
1) “While previous Thai studies examined commercial LEDs in lettuce, the effects of these off-the-shelf lamps on hydroponic Bok Choy cultivars, relative to natural light in semi-controlled conditions, remain unclear.” Without such a sentence, the study risks feeling like a small variant of existing lettuce work.
- 3. The Introduction states that this study focuses on "LED light intensity", but Table 1 clearly shows that the four LED treatments differ not only in PAR/PPFD, but also in lamp structure, diode mix and correlated color temperature.
1) Furthermore, natural light is treated as a "controlled" treatment, but its PAR/PPFD is not quantified; only illuminance (lux) is given.
2)Are the authors primarily testing intensity or "lamp type" (i.e., bundled effects of spectral distribution + intensity + structural design)? If the latter, the wording in the Aim statement should reflect that, rather than implying a clean intensity experiment.
- 4. Natural sunlight is presented as a baseline "Type B / C plant factory" condition. However, later in the paper, the differences between natural light and LEDs are interpreted partly as intensity effects, partly as spectral effects.
1) It would be helpful to more clearly define, in the Introduction, what natural light represents in this study:
2) Is it a realistic greenhouse baseline, with variable intensity and full spectrum, against which commercial LED-only systems are compared? Or is it conceptually treated as a "low-light" condition? What do you think?
-5. The experiment is described as a completely randomized design (CRD) with five treatments. Later, in the Figure 1 legend, each rail is 120 cm long with a given planting spacing, and Figure 2 indicates n = 5 for the measured variables. However, it is not clearly stated (please check below).
1) How many hydroponic channels / rails per treatment were used.
2) Whether each treatment had multiple physically separate channels, or if there was one channel per treatment, amd multiple plants within that channel served as replicates.
3)This is critical for avoiding pseudoreplication: if all five measured plants under a given LED grow on the same rail under the same single fixture, the true experimental unit is the rail/lighting system, not the individual plants.
- 6. It is not completely clear whether.
1) The natural-light treatment also used an enforced 16 h day (e.g., by blackout and / or supplementary light), or natural-light plants simply experienced ambient daylength, and only LEDs had a controlled 16 h photoperiod.
2) Were all treatments, including "natural light", subjected to the same 16 h photoperiod? If so, how was this controlled for the natural-light treatment (e.g., shading curtains, supplemental light to fill gaps)? If not, then differences among treatments confound photoperiod with light source.
- 7. For natural light, only measured illuminance (37303 lux) is given; PAR and PPFD are missing.
1) Yet, in the abstract and text, the conclusion that LEDs "significantly enhanced growth and yield relative to natural light" is partly attributed to intensity and spectral factors.
2) Without comparable PPFD or DLI data for natural light, how can we disentangle whether LEDs are superior because of intensity, spectrum, or some other environmental difference (e.g., shading, greenhouse structure)?
3) Would it be possible to provide at least an approximate PPFD for the natural-light treatment, or otherwise acknowledge this limitation?
- 8. Statistical analysis is described very briefly -> ANOVA followed by DMRT at p < 0.05. Important details are missing.
1) Were "Hong-tai" and "Baby Bok Choy" analyzed completely separately, or in a combined model with species as a factor?
2) Were any assumptions (normality, homoscedasticity) checked?
3) Given the high coefficients of variation (CVs) reported for some traits (e.g., fresh and dry weights), how robust are the F-tests?
- 9. For "Hong-tai Bok Choy" (Table 3), the CV for fresh weight is reported as 69.02%, and for dry weight, 57.30%.
1) For Baby Bok Choy (Table 5), CVs are 52.68% (fresh weight) and 42.40% (dry weight). These values are extremely high for hydroponic leafy vegetable experiments.
2) Yet, the text confidently states that LED treatments "significantly enhanced" biomass compared with natural light and interprets treatment rankings as robust.
3) How do the authors explain such high variability within treatments?
4) Were there issues of uneven light distribution, nutrient flow, or other environmental heterogeneity?
5) Would it be more cautious to acknowledge that, despite significant F-tests, the high CVs reduce confidence in fine distinctions among LED treatments?
- 10. In the text (Section 3.2), it is stated that...
1)"Treatment 5 yielded the highest fresh weight (100.10 g) and dry weight (4.33 g), followed by Treatments 4 and 3, while Treatments 1 and 2 produced the lowest values (31.25 g and 16.52 g, respectively)".
2) However, Table 5 shows for fresh weight: treatment 1: 51.24 ± 5.81 g; treatment 2: 16.52 ± 5.10 g; treatment 3: 110.79 ± 3.53 g; treatment 4: 63.59 ± 16.42 g; treatment 5: 101.00 ± 3.51 g.
There is no 31.25 g value in the table, and Treatment 3 appears to have the highest mean fresh weight (110.79 g), not Treatment 5.
- 11. The text states that this reflects "greener and more yellowish leaves" and even "darker green leaves" under natural light compared with LEDs.
1) However, in the CIELAB color space system, "darker" is more associated with lower L*, not higher b*.
2) Here, L* differences among treatments are small, and an increase in b* generally indicates more yellow, not necessarily “darker green.”
3) Would it be more precise to describe the natural-light leaves as more intensely yellow-green (higher b*, more negative a*) rather than “darker green”?
4) And please indicate in your manuscript whether these parameters are CIELAB (i.e., CIE76 or CIEL*a*b*) or Hunter Lab.
- 12. For Baby Bok Choy, SCMR is highest under natural light; for "Hong-tai Bok Choy", the Discussion states that Treatment 5 had the highest chlorophyll content.
1) This is interesting, but the Results section does not deeply explore how SCMR relates to biomass variation.
2) Given that only one time point is measured and no gas-exchange data are provided, SCMR differences are not straightforward to interpret as "higher photosynthetic efficiency".
3) Also, SCMR is a strange and unfamiliar acronym. I strongly recommend using "SPAD" or "SPAD units".
- 13. The Discussion states that....
1) "…LED lighting regimes differing in spectral composition, luminous intensity, and structural design… Overall, LED treatments significantly enhanced vegetative growth….." and attributes species-specific responses to differences in PAR, PPFD, luminous intensity, and diode configuration.
2) Yet, for natural light, PPFD is not reported. Environmental conditions (daily light integral, temporal variation) are not characterized. This makes it difficult to disentangle whether the "superiority" of LEDs is driven by higher or more stable intensity, spectral composition, or other factors.
3) Could the authors more explicitly acknowledge that the study cannot cleanly separate intensity effects from spectral and structural effects, especially relative to natural sunlight?
- 14. The discussion refers to literature on the effects of red, blue, and mixed spectra in a relatively fine-grained way (e.g., red causing elongation, blue enhancing chlorophyll).
1) However, the current experiment does not include pure red or pure blue treatments; it uses complex commercial lamps with mixed diodes (e.g., warm white, cool white, red, blue, UV, IR).
2) When discussing mechanisms, could the authors more clearly separate general knowledge from the literature (e.g., "blue light is known to….") from what is directly demonstrated in this study (e.g., “the pink lamp with RB mix produced the highest biomass in Hong-tai”)?
- 15 Some passages in the discussion sound close to mechanistic conclusions, for example, that differences in diode configuration "may underlie species-specific responses" in a more causal sense.
1) Given the absence of physiological measurements (no photosynthesis, fluorescence, or anatomical data), this should probably remain at the level of informed speculation.
16. The conclusions section currently goes well beyond the specific findings of this experiment.
1) The conclusions assert that... "Blue light enhanced chlorophyll accumulation and photosynthetic efficiency, while red light promoted stem elongation and biomass accumulation. Importantly, the combined use of red and blue wavelengths produced synergistic effects…"
2)However.. The experiment did not include isolated "blue-only" or "red-only" LED treatments. Photosynthetic efficiency was not directly measured (no gas exchange measurements or fluorescence measurements). All lamps were multi-component commercial products (white + red + blue + UV + IR in various combinations).
3) These statements read as if they were directly demonstrated here, rather than being a summary of general LED literature.
4) Would the authors consider adding a short paragraph explicitly acknowledging limitations, such as a restricted number of cultivars and environmental conditions, limited quality metrics (no phytochemical data).
- 17. Please reorder your keywords in alphabetical order and include two more keywords that are highly relevant to create a total of five keywords.
- 18. This manuscript emphasizes the color temperature of LEDs.
1) Previous studies (e.g., https://doi.org/10.3390/ijpb15030058, https://doi.org/10.22698/jales.20240042) have also shown that differences in the color temperature of white LEDs lead to differences in spectral distribution, which in turn lead to various differences in plant growth, physiological function (chlorophyll fluorescence response and remote sensing vegetation indices), and chlorophyll content.
2) Meanwhile, very few studies have emphasized color temperature in LED cultivation. To support this paper, even the few studies on color temperature should be identified and supplemented.
3) Connecting these findings to the current manuscript effectively supports the results of this paper and highlights the need for such research.
-19. The scholarly richness of this manuscript seems relatively low compared to other articles in the journal.
1) If possible, please add "Pearson correlation analysis", "hierarchical clustering analysis", or "PCA". This will increase the scholarly richness of this manuscript.
-20. This manuscript itself has a limited number of figures, but the quality is also quite low. For those two figures, you need to improve their quality by using a professional editing service.
Please carefully review the above and use them to strengthen the content of your manuscript and improve clarity.
Thank you.
Reviewer 2 Report
Comments and Suggestions for Authors1.The overall impression of the article is that the content is somewhat thin.
2.There are too few conclusive statements (core content) in the abstract, while there are too many other secondary contents. In addition, key results should be quantified and not described in a general way.
3.In section 2.1. Plant Materials and Growth Conditions:â‘ what are the considerations for selecting plant materials (including material characteristics); â‘¡ What does' 2.1. Plant Materials and Growth Conditions' mean? Is it light processing for 16 hours? Still not clear, what is the situation with the remaining (24-16) hours? Is it darkness or natural light?
4.In "2.1. Plant Materials and Growth Conditions"：①what are the environmental conditions in the laboratory, including light (whether natural light affects it, whether natural light cycles affect it) and ventilation (carbon dioxide and oxygen concentrations)? ② Based on Figure 1, will the various light treatments interfere with each other (illuminating other treatments)? ③ What is the light quality (composition of different wavelengths of light) of the LED used? Is there any influence of "light quality" factors other than "light intensity"?
5.In section 2.3. Growth and Physiological Measurements：①only a few growth indicators and chlorophyll content were measured. Can this indicate the impact of LED on quality? ② Did you not carry out withering treatment before drying and measuring dry weight?
6.In "5. Conclusions", expressions such as "Blue light", "while red light", and "red+blue" appear, but there is no detailed explanation in "2.3. Growth and Physiological Measures". Therefore, what needs to be supplemented must be supplemented, and what needs to be rewritten, such as the conclusion and abstract, must be rewritten.
Reviewer 3 Report
Comments and Suggestions for AuthorsThis manuscript focuses on the effects of commercial Light-Emitting Diodes (LEDs) light sources on the growth performance and yield of two Pak Choi varieties. While the results could serve as a reference for optimizing light environment management in plant factories, the current manuscript is considered too simplistic. The dataset is insufficient, the result analysis contains several errors, and the discussion needs substantial strengthening. As it stands, this manuscript is not suitable for publication as a research paper in Horticulturae.
- The result analysis requires careful checking. For example, the statement in Lines 121–123 is inconsistent with the data presented in Table 2. Furthermore, the authors should focus on stating the statistical significance of differences rather than merely reporting absolute value differences, as the latter lacks scientific rigor.
- The abstract should present more specific results. For instance, it should clearly state that the LED light sources had no significant effect on the number of leaves, plant height, canopy width, and leaf length of Hong-tai Bok Choy.
- The effects of LEDs on crop growth and development have been extensively studied. The authors need to further elaborate on the novelty of this study and the practical application value of these results in agriculture.
- It is recommended to provide spectral distribution graphs for each LED luminaire. This information would greatly assist in explaining the impact of each treatment on Bok Choy.
- The discussion section needs to be strengthened. For example, the authors should discuss why the "Pink" lamp (a mixture of red and blue) is superior to "White" light (broad spectrum). This could be explored by combining the mechanisms of Photosynthetically Active Radiation (e.g., red light promoting photosynthesis, blue light regulating morphology) with photoreceptor functions (e.g., phytochromes, cryptochromes).
- Figure 1: The figure lacks a scale bar.
- The authors need to conduct more extensive and in-depth research, measuring more physiological and biochemical indicators, to fully support the effects of LEDs on the growth and development of Bok Choy.
