Light Spectrum Effects on the Ions, and Primary and Secondary Metabolites of Red Beets (Beta vulgaris L.)
Round 1
Reviewer 1 Report
The manuscripts is devoted to the topical issue - optimization of LED lighting conditions in a vertical farm (VF) greenhouse. This problem statement is not original. Philips supplies the market with special lighting products of the GreenPower series (toplighting, interlighting, Tissue Culture Module), which have a high luminous efficiency in the region of photosynthetically active radiation (PAR). Samsung, Seoul Semiconductor, LG Innotek, Nichia Corporation, Sharp, Osram Opto Semiconductors and others are also optimizing the spectral composition of semiconductor grow lights. The novelty of the presented study may lie in the selection of various LED models that create a favorable light regime when growing Red beets (Beta vulgaris L.) under VF conditions.
The authors have done significant work to determine the accumulation of wet and dry mass of shoots and roots, as well as the content of phenols, sugars, betalains, and other biochemical parameters in Red beets plants cultivated in VF under three types of LED lighting and also in open ground (OF) conditions. In a number of cases, the indicators obtained in VF exceeded those in OF. More often, but not for all indicators, the best results were registered when using radiation with the dominance of red rays (RED variant). The results obtained may be of practical importance for the production of food dyes, food additives and medical preparations.
The study is of interest, corresponds to the subject of the journal and meets its main requirements. At the same time, it contains a number of shortcomings that require improvement and correction.
1. It is not clear how the emission intensity of the LEDs was determined? The methodological section states that “…radiated of 150.2 ± 5.4 μmol/m2 of light intensity…”. (Seconds are lost in the specified dimension.) It is possible to correctly determine the quantum flux density (μmol/m2s) only for narrow-spectrum (quasi-monochromatic) radiation. For the polychromatic radiation in question, it is necessary to integrate over the spectral curve of the emitters. Therefore, in the article it is necessary to present the spectra of all three LED sources, as well as calculations of the quantum flux density.
2. Throughout the work, there is a comparison of the biochemical parameters of plants grown in VF and OF. Such a comparison is incorrect. Vegetation conditions in the greenhouse and open ground differ significantly in terms of light and thermal conditions, humidity, mineral nutrition and microbiotic background. Judging by Figure 1, plants B and D from VF and OF were at different stages of ontogeny, which could also affect biochemical parameters. All of them are calculated per unit dry weight of the biomaterial (Figure 2 - 5). For practical purposes, it is not this characteristic that is important, but the quantity of the product (phenols, sugars, betalains, etc.) per unit area of vegetative plants and the cost of this product. Such calculations need to be made. To assess the effectiveness of LED lighting one should use the plants cultivated under the influence of light from fluorescent lamps widely used in greenhouses (instead of plants grown under OF conditions).
3. To assess the biological effectiveness of a particular type of illumination, it would be advisable to measure the dynamics of induced chlorophyll fluorescence (the Kautsky effect) and use it to determine the specific photosynthetic activity of cultivated plants. This is easy to do with the help of special devices that are currently widely used, for example, Pulse-Amplitude-Modulation PAM-2500 (Germany).
4. Technical notes. “…Red LEDs (maximum absorption at 660-700 nm)…”. LEDs do not absorb light, but emit it. The introduction is full of popular information, but the mechanisms of action of light, in particular on vegetable crops, are not considered. There are many semantic repetitions in the text. In Figure 3, there are no data in a number of options, which makes it difficult to analyze the information. The abstract uses undeciphered designations (for example, RED, CON), which makes it impossible to understand the meaning of the described work. The DBPia.co.kr abstract version was much better in this regard. Taking into account modern possibilities, color illustrations would be much more convenient for perception. The English language in the manuscript needs careful checking. It may be a good practice to test expressions via search engines such as google-scholar. For example, the expression "times higher than them" occurs 60 times, while "times higher than that" occurs 470000 times.
Author Response
Please see the attachment.
Author Response File: 
Author Response.pdf
Reviewer 2 Report
Manuscript_1794163 under the title Light spectrum effects on the ions, and 1st and 2nd metabolites 2 of Red beets (Beta vulgaris L.) by Changmin Oh, Jai-Eok Park, Yang-Ju Son, Chu Won Nho, Nam Il Park and Gyhye Yoo interesting and original.
Notes are included in the manuscript PDF.
The style of the English language should be checked by an English language specialist. I am not an expert on the English language, I recommend that it be checked by an authorized person.
Comments for author File: Comments.pdf
Author Response
Thanks for your advice. Thanks for confirming our mistake. Based on your advice, I've made a lot of corrections right. I think a lot of readers must have been confused by what we wrote. Once again, thank you for looking at our article and pointing out the errors in detail.
We received English editing from a professional editor (Editage, #AEKRF_2).
Author Response File: Author Response.pdf
Reviewer 3 Report
Light spectrum effects agronomy
Lines 90 and 204: The unit should be mmol m-2 s-1, not mmol m-2. ‘120 mmol m-2 s-1’ of PPFD (photosynthetic photon flux density) is a better expression than ‘120 mmol m-2 s-1 of light intensity’ because the light intensity has several meanings and units.
Lines 102: Red and blue LEDs emit red and blue photons, respectively. However, white LEDs emit a mixture of blue, green and red photons (Some white LEDs emit ultraviolet and far-red photons, too). (Spectral distribution of a white LED shows 3 peaks in blue, green and red regions.) The percentages of green photons of white LEDs vary in a range between 5% and 45% with the product type. The percentages or its spectral distribution are provided in the product catalog. In short, the white LEDs mean nothing in this experiment if the percentages of blue, green and red photons are not given. Give the photon percentages of blue, green and red and the PPFD in each of the 3 treatments in Materials and Methods section. These percentages and the presence/absence of ultraviolet photons generally affect the production of 2nd metabolites significantly.
Author Response
Reviewer 3
Lines 90 and 204: The unit should be mmol m-2 s-1, not mmol m-2. ‘120 m mol m-2 s-1’ of PPFD (photosynthetic photon flux density) is a better expression than ‘120 mmol m-2 s-1 of light intensity’ because the light intensity has several meanings and units.
Thanks for your comments. There was our typo-error. We corrected the units for light intensity correctly (Lines 97 & 113)
Lines 102: Red and blue LEDs emit red and blue photons, respectively. However, white LEDs emit a mixture of blue, green and red photons (Some white LEDs emit ultraviolet and far-red photons, too). (Spectral distribution of a white LED shows 3 peaks in blue, green and red regions.) The percentages of green photons of white LEDs vary in a range between 5% and 45% with the product type. The percentages or its spectral distribution are provided in the product catalog. In short, the white LEDs mean nothing in this experiment if the percentages of blue, green and red photons are not given. Give the photon percentages of blue, green and red and the PPFD in each of the 3 treatments in Materials and Methods section. These percentages and the presence/absence of ultraviolet photons generally affect the production of 2nd metabolites significantly.
As you ask, the spectrum information of the three LED (red, blue and warm white) chips used in the experiment is added to supplementary Figure S1 (explanation in M&M line 112).
Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
A minor note: the spectra of emitting elements presented in the supplementary do not correspond much to the real spectrum of the light source, since the final spectrum will be determined by the intensity of each element, the radiation pattern (location of plants relative to the lamp), etc. Therefore, it would be more correct to give the spectrum of the lamp itself, taken under conditions as close as possible to experimental ones.
