The Effect of Light Intensity and Photoperiod on the Yield and Antioxidant Activity of Beet Microgreens Produced in an Indoor System
Round 1
Reviewer 1 Report
The MS "The effect of light intensity and photoperiod on the yield and antioxidant activity of beet microgreens produced in an indoor system" is very timely as the microgreen is in the focus of the research now. Lighting responses are species-specific and its crucial to fine-tune the lighting strategy for the crop in question. However, despite species specificity there are general physiological regularities and light-growth relations, which are underestimated in the present work. Unfortunately, the MS has many shortcomings.
Major concerns.
1. The abstract is poorly written. The conclusion is made that better yield and resource use efficiency was reached under 12 h photoperiod, but not mentioned that maximum antioxidant content was determined under 16 h photoperiod. Why then to use antioxidant activity in the title?
Line 16 - raised compared to what? the largest photoperiod at what PPFD?
Line 18 - reduction compared to what? The low and medium intensities at what photoperiod?
Line 22 - resource use efficiency (not resource efficiency)
Line 24 - it's not possible to save already used electricity
Line 25 - repetition of lines 14-15
Line 23 - shortest (not shorter) photoperiod
2. Introduction is very weak and has no particular structure. All known facts interspersed with examples from not always related researches. In particular, the paragraph on the effects of photoperiod on growth and antioxidant activity is very poor. There are a lot of research on the effect of photoperiod on microgreens, including long photoperiods and continuous lighting. So, it is better to analyze them than refer to injuries caused by long photoperiods in sensitive species like tomato (lines 94-96).
Line 47 - comparing (not concerning)
Lines 91-92 - evaluated photoperiods in beet leaves. What does it mean?
Lines 99-107 - There are review papers on the effects of light spectra on plants, including microgreens. It is better to refer to them than to 4 different papers.
Line 154 - What is ref 35 for?
Line 246 - Does the electricity consumtion depend on light intensity or not?
3. Results. Tables 2-5, lines 265-270 and throughout the text - I don't understand the data for different light intensities for what photoperiod are presented and data for photoperiod at what light intensities? Provided statistics made the data not understandable.
Lines 272-273 - dry matter percentage (not dry matter)
Lines 297, 302 - What are Chroma and hue?
Lines 407-409 - Re-write the sentence.
Lines 401-410 - Variations in temperature and air humidity are to be described in the section Methods and Materials
4. Discussion. The DLI values are provided for all the treatments. Why do authors did not make an attempt to explain why yield decreases with the increase in DLI? It is not according to physiology laws except photoinhibition occurs. It requires to be discussed.
No discussion about the role of FR light in the spectra.
5. Conclusion. It is not correct to say that the ratio B:R:FR 23:75:2 is optimal as the other ratios were not studied or compared.
Author Response
The MS "The effect of light intensity and photoperiod on the yield and antioxidant activity of beet microgreens produced in an indoor system" is very timely as the microgreen is in the focus of the research now. Lighting responses are species-specific and its crucial to fine-tune the lighting strategy for the crop in question. However, despite species specificity there are general physiological regularities and light-growth relations, which are underestimated in the present work. Unfortunately, the MS has many shortcomings.
Major concerns.
- The abstract is poorly written. The conclusion is made that better yield and resource use efficiency was reached under 12 h photoperiod, but not mentioned that maximum antioxidant content was determined under 16 h photoperiod. Why then to use antioxidant activity in the title?
Improved the wording of the abstract and added a concluding sentence on the antioxidant activity, colored in green.
Line 16 - raised compared to what? the largest photoperiod at what PPFD?
The sentence was completed and colored in green. In this case, the result is explained considering photoperiod as an independent factor. Hence, PPFD cannot be indicated as a function of photoperiod since there is no significant interaction.
Line 18 - reduction compared to what? The low and medium intensities at what photoperiod?
The sentence was modified and colored green. In this case, the result is explained, considering intensity as an independent factor. Hence, photoperiod cannot be indicated as a function of intensity since there is no significant interaction.
Line 22 - resource use efficiency (not resource efficiency)
It was corrected and colored green.
Line 24 - it's not possible to save already used electricity
The word "used" was deleted.
Line 25 - repetition of lines 14-15
The wording of lines 14-15 was modified so as not to be similar to line 25.
Line 23 - shortest (not shorter) photoperiod
The word "shorter" was modified to shortest and colored green.
- Introduction is very weak and has no particular structure. All known facts interspersed with examples from not always related researches. In particular, the paragraph on the effects of photoperiod on growth and antioxidant activity is very poor. There are a lot of research on the effect of photoperiod on microgreens, including long photoperiods and continuous lighting. So, it is better to analyze them than refer to injuries caused by long photoperiods in sensitive species like tomato (lines 94-96).
The introduction was improved according to the reviewer's comments; the new information was colored in green.
Line 47 - comparing (not concerning)
The word "concerning" was replaced for “comparing” and colored in green
Lines 91-92 - evaluated photoperiods in beet leaves. What does it mean?
The sentence was reworded for understanding and colored in green
Lines 99-107 - There are review papers on the effects of light spectra on plants, including microgreens. It is better to refer to them than to 4 different papers.
The authors modified the paragraph as suggested by the reviewer; the changes were colored in green.
Line 154 - What is ref 35 for?
The reference's position was corrected. The reference support to the methodology used was colored in green
Line 246 - Does the electricity consumtion depend on light intensity or not?
The authors did not find this phrase in the line indicated by the reviewer. Nevertheless, in section 4.5. Effect of intensity and photoperiod on resources, we added a sentence to clarify the reviewer's question
- Results. Tables 2-5, lines 265-270 and throughout the text – I don't understand the data for different light intensities for what photoperiod are presented and data for photoperiod at what light intensities? Provided statistics made the data not understandable.
Because the study was carried out under a factorial structure, the aim of the statistical analysis was aimed at observing whether the interaction between the factors (intensity and photoperiod), however non-significant interaction was detected. According to that result, each factor was analyzed independently. In section 2.5. “Experimental design and statistical analysis” interaction or independent factors analysis was clarified (colored in green).
Lines 272-273 - dry matter percentage (not dry matter)
The authors assume that the correct line is 172-173; the sentence was changed as suggested, colored in green. Also, it was changed in the results section.
Lines 297, 302 - What are Chroma and hue?
The authors assume that the correct line is 197-202; both terms are explained and colored in green.
Lines 407-409 - Re-write the sentence.
There was an error in the spelling of the word mesophiles; the changes was colored in red, as it was indicated by reviewer 2.
Lines 401-410 - Variations in temperature and air humidity are to be described in the section Methods and Materials
The variation of both variables was described in materials and methods and colored in green.
- Discussion. The DLI values are provided for all the treatments. Why do authors did not make an attempt to explain why yield decreases with the increase in DLI? It is not according to physiology laws except photoinhibition occurs. It requires to be discussed.
The DLI corresponds to the combination of intensity x photoperiod. According to the statistical analysis performed in our study, this interaction was not significant. Therefore, it is not possible to discuss yield based on DLI. Therefore, intensity and photoperiod were discussed independently.
No discussion about the role of FR light in the spectra.
A discussion was added in section “4.2 Effect of intensity and photoperiod on physical evaluations” and colored in green
- Conclusion. It is not correct to say that the ratio B:R:FR 23:75:2 is optimal as the other ratios were not studied or compared.
The authors corrected the conclusion and deleted the spectrum.
Author Response File: 
Author Response.docx
Reviewer 2 Report
The manuscript overall must undergo the following revisions and some of the few corrections seen as listed below:
line 153: "massaged" should be "measured"
line 236: "psychrophilic" should be "psychrophiles"
line 261: indicate the current versions of the software applied for both Infostat and R
line 357: "mesophyll" should be corrected into "mesophile"
line 360: "y" should be corrected as "and"
line 379: "o" shoud be "or"
Table 4: What do "a", "b", "c" after the numerical values should be superscript and must have their corresponding connotations in the footnote below the table.
line 614: "founded" should be "found"
Please go through the entire manuscript conscientiously to check for other minor errors in spelling, verb tenses, etc.
Check the format for in text citation specific for Horticulturae. The in text citation looks redundant by mentioning the source and then indicating their respective numbering. Should there be only one preferred format? Please check.
Very important:
There are just a few particular concerns regarding the research design and outcome of the microbiological counts.
The authors stated that,
"According to 593 D'Souza et al. (2015) [70], LEDs provide an alternative to chemical sanitizers in ascertaining microbiological food safety and an additional means of decontamination as microbial resistance becomes a more urgent problem. Specifically, irradiance is used to quantify the 596 amount of monochromatic light in microbial inactivation operations in terms of light energy."
Since the results of the microbiological counts show that the amounts passed the criteria for food safety, how can the Authors conclude that the LED exposures influence the decrease in number of counts when the substrates, prior to experimentation, were not tested first for mirobial count? I was looking for the "unexposed" substrate total microbial counts but no data are shown. The Authors should include these since these are very important. I understand that there were also other factors mentioned further explaining the minimal counts. But it is still very important that the initial microbial counts of the substrates must be performed prior to experimentation. This is a very important baseline.
Author Response
The manuscript overall must undergo the following revisions and some of the few corrections seen as listed below:
line 153: “massaged” should be “measured”
The word “massaged” was changed to “measured”, colored in red in the text
line 236: “psychrophilic” should be “psychrophiles”
The word “psychrophilic” was changed to “psychrophiles”, colored in red in the text
line 261: indicate the current versions of the software applied for both Infostat and R
The versions were added and colored in red in the text.
line 357: “mesophyll” should be corrected into “mesophile”
The word “mesophyll” was changed to “mesophile”, colored in red in the text
line 360: “y” should be corrected as “and”
“y” was changed to “and”, colored in red in the text
line 379: "o" shoud be "or"
“o” was changed to “or” in all footnotes, colored in red in the text
Table 4: What do “a”, “b”, “c” after the numerical values should be superscript and must have their corresponding connotations in the footnote below the table.
A superscript and the corresponding footnote were added below all the tables, colored in red in the text
line 614: “founded” should be “found”
The word “founded” was changed to “found”, colored in red in the text
Please go through the entire manuscript conscientiously to check for other minor errors in spelling, verb tenses, etc.
The manuscript was checked, and errors were corrected.
Check the format for in text citation specific for Horticulturae. The in text citation looks redundant by mentioning the source and then indicating their respective numbering. Should there be only one preferred format? Please check.
It was a mistake to send the citation together with the respective numbers. The error has been corrected.
Very important:
There are just a few particular concerns regarding the research design and outcome of the microbiological counts.
The authors stated that,
“According to 593 D’Souza et al. (2015) [70], LEDs provide an alternative to chemical sanitizers in ascertaining microbiological food safety and an additional means of decontamination as microbial resistance becomes a more urgent problem. Specifically, irradiance is used to quantify the 596 amount of monochromatic light in microbial inactivation operations in terms of light energy.”
Since the results of the microbiological counts show that the amounts passed the criteria for food safety, how can the Authors conclude that the LED exposures influence the decrease in number of counts when the substrates, prior to experimentation, were not tested first for mirobial count? I was looking for the “unexposed” substrate total microbial counts but no data are shown. The Authors should include these since these are very important. I understand that there were also other factors mentioned further explaining the minimal counts. But it is still very important that the initial microbial counts of the substrates must be performed prior to experimentation. This is a very important baseline.
The authors added the count of microorganisms analyzed in the substrate before seeding item microorganism counts in the materials and methods section (colored in red). In addition, we added a sentence in the discussion emphasizing that the counts observed in the substrate for the different microorganisms did not exceed the limit for causing a health risk.
Author Response File: Author Response.docx
Round 2
Reviewer 1 Report
The MS was improved, but unfortunately the answer to question 4 is very strange and shows that the authors do not understand what the DLI is.
DLI is not a result of interaction of photoperiod and intensity. It is a sum of light received by plants per day (photoperiod x light intensity). Generally the more DLI the higher yield (to a certain level when higher DLI causes photoinhibition). In your research the yield decreases at higher DLI, but you do not report that photoinhibition took place. Thus, the question is how it is possible? Without explanation of this phenomenonn the whole paper has no scirntific significance. Please, provide an explanation or check carefully your data.
Author Response
The authors thank the reviewer for his suggestions and comments that improved the manuscript. In addition, the discussion was broadened by adding more information and bibliographic references to answer the question. The additional information was colored in light blue. Also, the manuscript was reviewed to correct minor errors, which were colored in light blue.
Reviewer 2 Report
Accepted. Please go through another round of checking to make sure that overlooked errors are corrected.
Author Response
The authors thank the reviewer for his suggestions and comments that improved the manuscript. Minor corrections were made throughout the manuscript and were colored in light blue.
