The Photosynthetic Performance of Red Leaf Lettuce under UV-A Irradiation

Round 1

Reviewer 1 Report

Dear Authors/Colleagues

Thank you for submitting the manuscript for consideration. The research theme is interesting, especially for the photosynthesis performance of UV-A light under a controlled environment. The theoretical and practical part of the paper is nicely presented. However, the reviewer had some minor inquiry, please follow bellow-  

1. The author should be mentioned the distance between canopy and light.

2. Figure 2 is ambiguous. The reviewer suggested revising the figure with clear remark, small or capital letter on the bar. Please follow it with all figures.

3. Do you have any results on light or CO₂ compensation point under BRUV-A lights? If you have, please mention it. The reviewer anticipated that it is an important factor for the survival or photosynthesis functioning of plants grown under artificial light conditions in a controlled environment. 

4. Please add or show the photographs of the lettuce growth results on the manuscript that treated under all BRUV-A lights. 

Thank you.

Best of luck!

 

Author Response

Dear Reviever,

The manuscript was improved according to the comments:

1. The author should be mentioned the distance between canopy and light. – The distance between canopy and light source was 25 cm.
2. Figure 2 is ambiguous. The reviewer suggested revising the figure with clear remark, small or capital letter on the bar. Please follow it with all figures. - corrected
3. Do you have any results on light or CO₂compensation point under BRUV-A lights? If you have, please mention it. The reviewer anticipated that it is an important factor for the survival or photosynthesis functioning of plants grown under artificial light conditions in a controlled environment. – The parameters were supported equal and did not changed during the experiment. Only one variable (composition of the light with different UV-A wavelengths) was used in this experiment.
4. Please add or show the photographs of the lettuce growth results on the manuscript that treated under all BRUV-A lights. – The photographs of the lettuce growth results were added.

Reviewer 2 Report

Article: 794206

Title: Photosynthetic performance of red leaf lettuce under UV-A irradiation

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General Comments

Overall a very informative paper (and concise, thank you!) and one that addresses an area of great interest in CEA  that is currently deficient in available research; although that is rapidly changing.  I like the fact that this paper takes such a broad and wholistic look at plant responses, covering a wide array of metrics.

My only significant point of discussion (bordering on concern in a general CEA/plant biology context) is in the use of irradiance as the governing metric in the UVA treatments.  All UVA treatments are reported as an irradiance of 2.2. mW cm^-2.  There is now some evidence for a direct role in photosynthesis at these wavelengths and based on that  , and to better relate to the other wavelengths, the UVA should be reported as photon flux density with units of mol m^-2 s^-1, or perhaps even PPFD but that is still being debated.  On a similar note, this study is looking at specific wavelengths of UVA (or rather narrow wavebands). In this case I would argue that the energy delivered to the plant at each of these wave lengths is different given that shorter wavelengths transmit greater energy; a difference that may play a role in physiological responses to UVA.  Following this, 2.2 mW cm^-2 at say 402 nm would require more photons than 2.2 mW cm^-2 at 367nm, again, this could have an influence on physiological responses to the treatments.  I would strongly suggest that the authors report in PFD or report the spectral irradiance (W m^-2 nm).  This is a discussion that has not been widely resolved in the literature but is worth addressing here.

The material and methods, specifically the experiment set-up/design details are insufficient (i.e., to determine if replicates are real or pseudo).  I have highlighted some of the deficiencies in the line-by-line evaluation.  Along these lines, more detail is needed in the statistical analysis section (e.g., in the first sentence, what type of analysis was used?).

The paper would be significantly improved in terms of flow and readability with additional editing for grammar and language.  The discussion in particular would benefit from a thorough edit for flow.  I have made a few editorial suggestions but additional editing will benefit the paper significantly.

 

Figures 1-3

It is probably a function of the PDF generator the journal uses but:

1) all the significance indicators (letters above bars) are cut off.

2) I don’t see any error bars on any of the graphs. 

3) There are no legend labels.

 

——————————————— —

Line-by-line

L30: I don’t think ‘indices’ is the right word, or at least it is not clear. Perhaps “…different light spectra…” or “…different wavelengths of light…”

L32/33: Needs rewording.  Try — “Despite major research efforts focused on…”

L42/43: The authors state that, “ There is currently no data concerning pant responses to UV-A”.  Are the authors referring to a specific response to UV-A?  If not, then this statement is false.  Although the available research on UVA is limited relative to say blue light, there is still ample data around UV-A and plant responses.

L54/55: Awkward sentence.  Consider — “The complex set of photo- and non-photochemical quenching reactions that have evolved in plants to mitigate photoinhibition has allowed them to thrive.”

L62/83: Did the authors log the temperature data over the course of the experiment?  If so, use this data to report the actual mean and SD (not SE) of the Day/Night temperatures.  The set points reported and the rather precise (but large) errors raise some questions.  The errors overlap for one thing so it is quite possible, without seeing the actual logged data, that the day and night temperatures often overlapped.   

Please provide specific levels of all nutrients, including micronutrients.  Nutrition plays a big part in physiology and hence it is important, from a repeatability perspective, to provide all this information.

Please provide additional information on the ‘vessels’ used — e.g., dimensions.

            Line 69-71 — Remove brackets

How were the individual light treatments separated within the single chamber?  How did you prevent light bleed from one treatment to another?  How did you randomize the treatments?

When reporting growth chamber conditions I suggest looking at the recommendations of the NCERA-101 working group.  https://www.controlledenvironments.org/growth-chamber-handbook/

 

L96: is the third developed leaf the ‘last fully expanded leaf’, which is the standard for measuring these parameters?

L131/143: Is there a methods reference for this or did you come up with the procedure on your own (and validated)?

L230: DA supposed to be DW

 

Author Response

Dear Reviewer,

thank you for valuable comments. 

Overall a very informative paper (and concise, thank you!) and one that addresses an area of great interest in CEA  that is currently deficient in available research; although that is rapidly changing.  I like the fact that this paper takes such a broad and wholistic look at plant responses, covering a wide array of metrics.

My only significant point of discussion (bordering on concern in a general CEA/plant biology context) is in the use of irradiance as the governing metric in the UVA treatments.  All UVA treatments are reported as an irradiance of 2.2. mW cm^-2.  There is now some evidence for a direct role in photosynthesis at these wavelengths and based on that  , and to better relate to the other wavelengths, the UVA should be reported as photon flux density with units of mol m^-2 s^-1, or perhaps even PPFD but that is still being debated.  On a similar note, this study is looking at specific wavelengths of UVA (or rather narrow wavebands). In this case I would argue that the energy delivered to the plant at each of these wave lengths is different given that shorter wavelengths transmit greater energy; a difference that may play a role in physiological responses to UVA.  Following this, 2.2 mW cm^-2 at say 402 nm would require more photons than 2.2 mW cm^-2 at 367nm, again, this could have an influence on physiological responses to the treatments.  I would strongly suggest that the authors report in PFD or report the spectral irradiance (W m^-2 nm).  This is a discussion that has not been widely resolved in the literature but is worth addressing here. - Authors agree with the reviewer about the disputable metrics of UV-A. However, as the UV-A wavelengths exceeds the region of Photosynthetically active radiation and the limits of standard tools for PPFD (photosynthetic photon flux density) measurement, we chose another measure, standard for UV and equalized the amount of UV-A light accordingly. According reviewer's recommendations, Table 1 was supplemented with the PFD (photon flux densities) of UV-A wavelengths.

The material and methods, specifically the experiment set-up/design details are insufficient (i.e., to determine if replicates are real or pseudo).  I have highlighted some of the deficiencies in the line-by-line evaluation.  Along these lines, more detail is needed in the statistical analysis section (e.g., in the first sentence, what type of analysis was used?).

The paper would be significantly improved in terms of flow and readability with additional editing for grammar and language.  The discussion in particular would benefit from a thorough edit for flow.  I have made a few editorial suggestions but additional editing will benefit the paper significantly.

 

Figures 1-3 - corrected

It is probably a function of the PDF generator the journal uses but:

1) all the significance indicators (letters above bars) are cut off.

2) I don’t see any error bars on any of the graphs. 

3) There are no legend labels.

 

——————————————— —

Line-by-line

L30: I don’t think ‘indices’ is the right word, or at least it is not clear. Perhaps “…different light spectra…” or “…different wavelengths of light…” – changed to “The impact of different light indices, such as wavelengths and intensity, on plant photophysiological responses is well described.”

L32/33: Needs rewording.  Try — “Despite major research efforts focused on…” -corrected

L42/43: The authors state that, “ There is currently no data concerning pant responses to UV-A”.  Are the authors referring to a specific response to UV-A?  If not, then this statement is false.  Although the available research on UVA is limited relative to say blue light, there is still ample data around UV-A and plant responses. – changed to: “There is currently no limited data concerning plant responses to UV-A”

L54/55: Awkward sentence.  Consider — “The complex set of photo- and non-photochemical quenching reactions that have evolved in plants to mitigate photoinhibition has allowed them to thrive.” – corrected.

L62/83: Did the authors log the temperature data over the course of the experiment?  If so, use this data to report the actual mean and SD (not SE) of the Day/Night temperatures.  The set points reported and the rather precise (but large) errors raise some questions.  The errors overlap for one thing so it is quite possible, without seeing the actual logged data, that the day and night temperatures often overlapped. - Experiments were performed in walk-in controlled-environment growth chamber (4 x 6 m). The is no any model or manufacturer, as it is custom made. The day/night temperature was set at 21/17 °C, the deviation was maximum up to 2 °C.

Please provide specific levels of all nutrients, including micronutrients.  Nutrition plays a big part in physiology and hence it is important, from a repeatability perspective, to provide all this information. - The average amounts of nutrients, including micronutrients (mg L^-1) in the substrate are provided according to producer’s information. Unfortunately, but we do not have more information.

Please provide additional information on the ‘vessels’ used — e.g., dimensions.- 120 ml vessel (58x55x70 mm)

            Line 69-71 — Remove brackets -corrected

How were the individual light treatments separated within the single chamber?  How did you prevent light bleed from one treatment to another?  How did you randomize the treatments?

Each module has top frame, which prevents light bleed from the treatment. The walk-in controlled-environment growth chamber is large (4 x 6 m), thus the light modules were arranged at a distance of about 1.2-1.5 m from each other.

 

When reporting growth chamber conditions I suggest looking at the recommendations of the NCERA-101 working group.  https://www.controlledenvironments.org/growth-chamber-handbook/ - thank you for the recommendations.

 

L96: is the third developed leaf the ‘last fully expanded leaf’, which is the standard for measuring these parameters? – 6-7 leaves were formed, 4-5 leaves were fully developed, thus for the unique measurements 3^rd fully developed leaf was selected.

L131/143: Is there a methods reference for this or did you come up with the procedure on your own (and validated)? – The references were added:

Ma C., Sun Z., Chen C., Zhang L., Zhu S. (2014) Simultaneous separation and determination of fructose, sorbitol, glucose and sucrose in fruits by HPLC–ELSD. Food Chemistry 145:784–788.

Brons C., Olieman C. (1983) Study of the High-Performance Liquid Chromatographic Separation of Reducing Sugars, Applied to the Determination of Lactose in Milk. Journal of Chromatography, 259:79-86.

L230: DA supposed to be DW- corrected

 

Author Response File: Author Response.docx

Reviewer 3 Report

The authors of this manuscript studied the effects of red and blue light combined with UV light on the growth and development of lettuce. There are many studies on plant irradiation by red, blue or UV lights respectively, but there are relatively few literatures for combined studies. This experiment is novel in design and logical, and the conclusion supports the results. The only problem was the format of the figures. Suggest to accept after minor revision.

Line 65:  litre shoud be 'L'

Line 81: photosynthetic photon flux density (PPFD)

Figure 2,3,&4: 

1. Upper and lower indices need to correct.
2. Lowercase letters with significant differences are not clearly displayed.
3. Error bars are not shown.
4. No horizontal and vertical titles and units are shown.

 

Author Response

Dear Reviewer,

The manuscript was corrected according to the reviewers comments.

 

Reviewer 4 Report

This is a well-written paper evaluating the influence of UV-A wavelength on the morphology and photosynthetic behavior of red leaf lettuce.

Minor edits and formatting throughout manuscript.

l17: delete "that"

keywords: delete lettuce and UV-A

l33: remove space and/or

l45: [16], and

l45: plants' pigments

142: 88% B

l149: data were.....2019) or MS Excel (version 7.0).

l150: 0.05

delete "data....(version 7.0)"

representing

replications, and multivariate

l151: were performed

l163: resulted in a significant

l164: RBUV387,

RBUV367,

 

Reformat figures so that means separations are not cut off

l266: Despite this, phototropins

l277:  change neither nor to either or

Table titles should stand independent of manuscript

Author Response

Dear Reviewer,

The manuscript was corrected according to the reviewers comments.

Author Response File: Author Response.docx