Effects of LED Lighting Configurations on the Growth and Quality of Arugula (Eruca sativa Mill.) in a Vertical NFT System

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

You can view my comments in the attached file.

Comments for author File: Comments.pdf

Author Response

Please refer to the attachment.

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

This study investigates the effects of LED light spectrum and lamp-to-canopy distance on the growth and quality of arugula in a vertical NFT system. The topic aligns with the research hotspot of low-cost and efficient lighting management in vertical farming. The experimental design is reasonable, measurement indicators are relatively comprehensive, and it clearly shows that white LED at 20 cm canopy distance is optimal for biomass and polyphenol accumulation. The results have practical guiding value for arugula production in vertical NFT systems and generally meet publication standards. However, the manuscript needs improvements in experimental details, result analysis, discussion depth, data standardization, and economic applicability. Targeted revisions and supplements are required.

 

1.L109–117. CO₂ concentration control range (500–1000 ppm) was described, but enrichment start time, daily duration, ventilation rate, and air exchange parameters of the cultivation container were missing.

2. L155–180. Light spectrum and PPFD measurement methods were described, but measurement height, repetition, and calibration of the spectrometer were not detailed.
3. L241–254. Detailed procedures for total polyphenols, ORAC antioxidant capacity, and moisture determination were too brief; reagent dosage, reaction time, temperature, and calculation formulas need supplementation.
4. L256–261. When measuring relative chlorophyll index, only “largest leaf” was mentioned; exact leaf position (e.g., 3rd fully expanded leaf) and measurement repetition per leaf should be clarified.
5. L394–399. Chlorophyll content was only expressed in SPAD units; actual chlorophyll a, chlorophyll b, total chlorophyll, and Chl a/b ratio were not measured or analyzed.
6. 6. L427–452. Nitrate content was measured but not discussed in combination with leafy vegetable safety standards and light regulatory mechanisms; depth of analysis is insufficient.
7. 7. Section 3. Variety difference analysis was lacking; the study only used one arugula variety, but intraspecific response differences under light treatments were not quantitatively analyzed.
8. 8. Section 4. Discussion mostly cited literature on other leafy vegetables; recent studies on LED spectrum regulation of arugula should be added to highlight innovation and differences.
9. 9. L495–507. Lighting cost and energy consumption analysis was missing; combining actual operation costs of vertical farms will improve industrial practicability.
10. References. Some citation formats are inconsistent; recent 2–3 years’ related literature is insufficient. Supplement latest research to reflect frontier nature.

Author Response

Please refer to the attachment.

Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

- 1. The Introduction establishes the general relevance of light management in vertical farming and identifies arugula as a suitable model crop. 
1) However, the final framing of the research question is still not sufficiently precise. The manuscript repeatedly suggests that it evaluates the effects of light spectrum and lamp-to-canopy distance, yet the treatments actually differ simultaneously in spectrum, lamp distance, PPFD, and DLI. 
2) Therefore, the conceptual claim in the Introduction is stronger than the design can truly support. The study is not isolating spectral effects in a clean way; rather, it is comparing four lighting configurations. This distinction is important and should be stated explicitly from the outset.

- 2. I also found the rationale for the 'low-cost technology' angle underdeveloped. 
1) The Introduction repeatedly emphasizes economic efficiency and low-cost lighting, but the manuscript does not actually provide any quantitative energy-use, cost, or efficiency analysis. 
2) As written, the framing creates an expectation that the paper will compare biological performance together with economic or technical performance, but the results are limited mainly to biomass and selected quality traits. This mismatch makes the objective feel broader than what is ultimately delivered.

- 3. Were plant-level values averaged within each shelf level before ANOVA, or were individual plants analyzed as replicates?

- 4. Why were the spectral treatments not equalized to the same PPFD or DLI if the goal was to infer spectral effects?

- 5. Were the RB treatments pure RB spectra, or did they also include white light, as Table 2 seems to imply?

- 6. Why were chlorophyll measurements taken from the largest plants rather than randomly selected plants?

- 7. How exactly was nitrate concentration converted into the reported unit?

- 8. The biomass data clearly favor LW20 in both experiments, and this pattern is consistent within the paper. 
1) However, because LW20 also had the highest PPFD and DLI, these results do not justify the conclusion that the white spectrum itself was superior. 
2) At most, the results show that the LW20 treatment combination performed best under the tested conditions. The current wording repeatedly overstates what the design can support.

- 9. The treatment comparisons for antioxidant capacity are especially problematic. 
1) In Table 6, ORAC antioxidant capacity is marked as nonsignificant ('a' for all treatments; p-value reported as nonsignificant), yet the text states that LW20 showed a significantly higher antioxidant capacity and RB20 a significantly lower one.

- 10. The same section also contains obvious terminology errors, such as 'LB20' and 'RA20' instead of LW20 and RB20.

- 11. The correlation analysis between total polyphenols and antioxidant capacity is also overinterpreted. 
1) The manuscript reports r = 0.64 and treats this as biologically meaningful support for a direct relationship. However, from the way the section is written, it is not clear whether this correlation is based on individual replicate data or only on treatment means. 
2) If it is based on only the four treatment means shown in Table 6, then the correlation is statistically fragile and should not be discussed with such confidence. The manuscript must state the actual sample size used for that correlation.

- 12. The nitrate results are nonsignificant across treatments, yet the manuscript still frames lighting as improving 'quality-related traits' in a broad sense. That claim should be more carefully delimited. 
1) In this study, some quality-associated variables responded, but nitrate did not; moisture did not differ significantly, and antioxidant capacity appears inconsistent between table and text.

- 13. Why do the authors interpret the result primarily as a spectral effect when the white treatments also received substantially greater PPFD and DLI?

- 14. If economic efficiency is part of the claimed contribution, where is the supporting evidence on energy use, electrical consumption, or biomass per unit energy?

- 15. How do the authors explain the inconsistency between the ORAC statistics in Table 6 and the narrative description in the text?

- 16. The Conclusions are currently too strong for the design and data presented. 
1) The statement that white LED lighting at a shorter distance was the most favorable configuration is acceptable only if it is clearly framed as a result specific to the tested treatment combination.
2) The conclusion also continues the 'low-cost' framing without any quantitative support. As a result, the practical recommendation feels premature. 
3) A more defensible conclusion would be that, under the specific conditions tested, LW20 produced the best overall performance, but further experiments with equalized PPFD / DLI are required before attributing the effect specifically to spectral composition.

- 17. To further clarify the position of this study in the current literature on artificial lighting in controlled environment agriculture (CEA; included vertical NFT system), the authors should highlight in the Introduction or Discussion section the wide-ranging benefits of artificial lighting use on plant physiology and quality optimization, and link to recent studies (e.g., https://doi.org/10.11628/ksppe.2025.28.6.799) as supporting evidence, which would strengthen the legitimacy of this manuscript.

- 18. Keywords should be rearranged in alphabetical order.

- 19. The quality of the figure is very poor. There is no standard deviation or standard error. This needs to be added.

- 20. The number of papers that adequately support the content of the manuscript is very small. Consequently, the content of the manuscript gives the impression that it was written solely based on the authors' estimations. The legitimacy of the manuscript is strengthened by reinforcing the hypotheses or phenomena presented in the manuscript through references.

Thank you.

Author Response

Please refer to the attachment.

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

The corrections were sufficient.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

1. The overall framing is improved, but the interpretation still needs restraint. The revised manuscript now states more clearly that spectral composition and lamp-to-canopy distance varied simultaneously, together with the resulting PPFD and DLI.
1) However, some parts of the Abstract, Results, and Conclusions still read as if the superiority of the white spectrum itself had been demonstrated.
2) The safer interpretation is that LW20 was the best-performing lighting configuration under the tested conditions, rather than that white light per se was proven superior.

2. The optical characterization is still incomplete at the treatment level. The revised version clarifies that the RB treatments consisted of white LED light plus red and blue light, which is an important improvement.
1) However, Figure 3 still presents only the spectra of the individual emitters (red, blue, and white LEDs), not the actual combined spectra received by plants under LW20, LW40, RB20, and RB40.
2) Since the manuscript repeatedly interprets responses in terms of the canopy-level radiation environment, this remains a methodological limitation.

3. The comparison is still more complex than a simple 'white vs red-blue' contrast. The manuscript now makes clear that the RB treatments were not pure RB spectra.
1) As a result, the study compares four combined lighting configurations that differ in both spectral mixture and source distance.
2) Any wording implying a clean, isolated comparison of white versus RB spectral quality alone should therefore be avoided.

4. The chlorophyll section still contains a serious internal inconsistency. In the Results, Experiment 1 is described as having the highest relative chlorophyll index in LW40.
1) However, the following interpretive sentence attributes the higher chlorophyll content in Experiment 1 to LW20. In addition, the Conclusions state that no significant differences were observed in the chlorophyll index among treatments.
2) These statements are internally inconsistent and should be corrected explicitly.

5. The correlation analysis is still not fully interpretable. The manuscript reports a positive correlation between total polyphenols and antioxidant capacity (r = 0.64).
1) However, the actual sample size and analytical unit used for this correlation are still not stated clearly.
2) It remains unclear whether the analysis is based on treatment means, replicate means, or pooled observations. Without this clarification, the biological interpretation remains too strong.

6. The broad 'quality improvement' claim should still be narrowed. It is positive that the previous ORAC inconsistency has been corrected.
1) However, antioxidant capacity remains nonsignificant, moisture remains nonsignificant, and nitrate remains nonsignificant.
2) Under the current data, the clearest treatment-level quality effect is total polyphenols, not overall quality in a broad sense. The wording should therefore remain more selective and precise.

7. The low-cost and economic-efficiency angle is only partially supported. The revised Conclusions now appropriately acknowledge that no quantitative analysis of energy consumption or biomass per unit of energy was performed. This is a valuable correction.
1) Nevertheless, the Introduction and Methods still emphasize low-cost lighting and practical efficiency strongly enough to create expectations that the study does not fully meet.
2) The manuscript is stronger as a biological comparison of affordable lighting configurations than as an energy-efficiency study.

8. English-language revision is still needed. The chlorophyll section is the clearest example, because the wording now creates a factual contradiction. The nitrate discussion also contains overly long sentences and punctuation problems.

9. The manuscript is improved, but the best-treatment claim is still slightly overextended.
1) It is now much clearer that LW20 was the best-performing configuration under the tested conditions.
2) Nevertheless, phrases such as 'the most favorable overall response' remain somewhat stronger than necessary when several quality variables were nonsignificant, and the design still combines multiple changing factors.
3) The manuscript would be more defensible if it consistently stated that LW20 was the most favorable among the four evaluated configurations.

Thank you.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf