Effect of a Directional Electromagnetic Field on the Early Stages of Plant (Raphanus sativus and Saccharum officinarum) Growth

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

“Effect of directional electromagnetic forces on the early stages of plant growth.” is an interesting topic on providing a solid theoretical framework to design and develop control systems of plant growth rate using a directional EMF based on a simple solenoid. However, there are some important points that need to be improved before further processing. 

Firstly, in the abstract of of the manuscript, when it comes to electromagnetic forces  for the first time, abbreviations (EMF) should not be used directly.

Secondly, in the introduction of the manuscript, the authors did not mention why the two plant species of common radish (Raphanus sativus) and sugarcane (Saccharum officinarum) were chosen as research subjects ?

Thirdly, in the manuscript, some writing formats are not standardized, for example: L164, L231, L237, L 279, p < 0.05. P should be in italic form. L255, Figure 5. The image can be enlarged to look clearer.

Finally, this study lacks tracking of the latest relevant research progress in the past two years. In References, only 1 relevant literatures in 2023 are shown, and no one in 2024. I checked “Web of Science” and found 139 literatures on the relation of  electromagnetic field and plant on 2023 and 2024 Year.

Author Response

General Comments:

“Effect of directional electromagnetic forces on the early stages of plant growth.” is an interesting topic on providing a solid theoretical framework to design and develop control systems of plant growth rate using a directional EMF based on a simple solenoid. However, there are some important points that need to be improved before further processing. 

 

Answer:

Thank you very much for your kind comments and advice. We have responded to all your comments below.

 

Comment 1

Firstly, in the abstract of the manuscript, when it comes to electromagnetic forces for the first time, abbreviations (EMF) should not be used directly.

 

Answer 1

Thank you very much for this valuable comment.

As suggested, the abbreviation was defined in line 14:

“In this study, we aimed to develop a novel directional electromagnetic field (EMF) application method for promoting plant growth using a solenoid coil-based cultivation system.”

 

 

Comment 2

Secondly, in the introduction of the manuscript, the authors did not mention why the two plant species of common radish (Raphanus sativus) and sugarcane (Saccharum officinarum) were chosen as research subjects ?

 

Answer 2

The test plants used in this study are now widely used in factories for food preparation. Further, these plants have rapid germination and easy cultivation characteristics. We have added the reason for selecting these experimental plants to the revised text (line 86-89).

 

“In this study, we examined the effect of applying a directional EMF on seed germination and growth of two different plant species: common radish (Raphanus sativus) and sugarcane (Saccharum officinarum), which were selected because of their rapid germination and easy cultivation characteristics [19, 20].”

 

 

Comment 3

Thirdly, in the manuscript, some writing formats are not standardized, for example: L164, L231, L237, L 279, p < 0.05. P should be in italic form. L255, Figure 4. The image can be enlarged to look clearer.

 

Answer 3

As suggested, the “p”s in L170, L240, L246, and L292 were changed to italic form. Figure 4 was also enlarged for clarification.

 

 

Comment 4

Finally, this study lacks tracking of the latest relevant research progress in the past two years. In References, only 1 relevant literatures in 2023 are shown, and no one in 2024. I checked “Web of Science” and found 139 literatures on the relation of  electromagnetic field and plant on 2023 and 2024 Year.

 

Answer 4

As recommended, we have added some recent references (#6, 7, 12)

Reference 6: L38, L356-358

Reference 7: L38, L359-360

Reference 12: L41, L367-368

 

Again, thank you for your kind and valuable comments and suggestions.

 

 

Reviewer 2 Report

Comments and Suggestions for Authors

1.     In the abstract part(line 23), the author mentioned “plant growth hormone analyses”, but in the later paragraphs, the author only tested and analyzed IAA(a kind of plant growth hormone), and different plant growth hormones vary a lot in their effect on the plant. It would be more accurate if the author use “IAA” to replace “plant growth hormone” in the abstract part.

2.     The author fully explained the EMF application to radish and sugarcane. Still, some plant physiology indicators are suggested to be added to the paper, to fully clarify the mechanisms of the EMF system affecting the plants.

3.     Some figures of the EMF application system especially on working conditions are required to add to the paper.

4.     In the references part(line 353), the author should make sure whether there is one more “12” added in the front of the sentence.

5.     Line 210 should be carefully checked to see whether the formation of the sentence has slight differences.

Author Response

Comment 1

In the abstract part(line 23), the author mentioned “plant growth hormone analyses”, but in the later paragraphs, the author only tested and analyzed IAA(a kind of plant growth hormone), and different plant growth hormones vary a lot in their effect on the plant. It would be more accurate if the author use “IAA” to replace “plant growth hormone” in the abstract part.

 

Answer 1

Thank you for your valuable comments. As you commented, we added indole-3-acetic acid (IAA) instead of plant growth hormone at line 23.

“Similarly, plant root proliferation and indole-3-acetic acid (IAA) analyses indicated that directional EMF application was associated with root proliferation and hormone synthesis.”

 

 

Comment 2

The author fully explained the EMF application to radish and sugarcane. Still, some plant physiology indicators are suggested to be added to the paper, to fully clarify the mechanisms of the EMF system affecting the plants.

 

Answer 2

Thank you for this valuable comment. We think that the addition of plant physiology indicators is very important to study the effect of EMF on the plant. However, in this study, plants at a very early stage (after 7 days of cultivation) were used, and measurement of their additional physiology indicators such as photosynthesis activity was very difficult because of the limited leaf area. However, we agree that the addition of more additional plant physiology indicators is very important to interpret the effect of EMF on plants. Therefore, we have added additional sentences at Lines 306 to 311. Thank you for your suggestion.

“In particular, our study was only related to the early stages of plant growth, while grown plants may show very different sensitivity to EMF application. Therefore, the effect of longer durations of EMF application to plants need to be verified to interpret the EMF-plant interactions. Further, conducting future studies on other growth-related physiological indicators such as photosynthetic efficiency measurements could help clarify the mechanisms by which the EMF system affects plants.”

 

 

Comment 3

Some figures of the EMF application system especially on working conditions are required to add to the paper.

 

Answer 3

Thank you for this valuable comment. As suggested, we have added the photograph of EMF application in working condition as Figure S1. 

Figure S1. Photograph of the experimental plant growth control system used in this study

 

Comment 4

In the references part(line 353), the author should make sure whether there is one more “12” added in the front of the sentence.

 

Answer 4

As indicated, we have added the reference number (line 370-372). Apologies for the error. 

 

14. Song, H.J.; Yang, S.W.; Jo, J.W.; Choi, Y.K.; Lee, I.S.; Lee, B.U.; Lee, S.H.; Kim, H.H.; Kim, K.J.; Kim, H.J. Submerged leaves of live indoor foliage plants adsorb H1N1 influenza virus from suspension. Plant Signal. Behav. 2023, 18, 2163869. DOI:10.1080/15592324.2022.2163869.

 

 

Comment 5

Line 210 should be carefully checked to see whether the formation of the sentence has slight differences.

 

Answer 5

The sentence was modified as follows (currently line 217 to 219): “As inferred, directional variation of EMF application with different application times influenced this growth promotion/inhibition.”

 

 

Again, thank you for your kind and valuable comments and suggestions.

 

Reviewer 3 Report

Comments and Suggestions for Authors

Dear authors, 

My considerations are in the attached PDF, highlighted in orange and comments in the sticky notes.

Comments for author File: Comments.pdf

Author Response

 

Comment 1

Could you please be more specific and mention the two plant species studied ( Raphanus sativus and Saccharum officinarum)? The results differ depending on the species

 

Answer 1

Thank you for these valuable comments. As suggested, we have added the scientific names of the plants in the title.

“Effect of directional electromagnetic forces on the early stages of plant (Raphanus sativus and Saccharum officinarum) growth”

 

 

Comment 2

Please be specific, Which kind of plant activity? and give an example with references

 

Answer 2

Thank you for your comment. We have added specific information regarding the plant activity along with the references in the sentence (line 56) as follows:  

 

“Further, measurement of the EMF surrounding the pots based on inductance or the standing wave ratio (SWR) using a simple solenoid-type sensor was found to be a useful tool for monitoring plant water content [15] or plant vital activity [16].”

 

 

Comment 3

Kindly, add a suitable reference at line 74.

 

Answer 3

We have added reference 18 as suggested.

 

 

Comment 4

Please mention the two plant species studied here

 

Answer 4

As suggested, we have added the names of the plant species to the sentence in line 76 to 77.

“In this study, we aimed to monitor the effects of a directional EMF generated by a solenoid on seed germination and plant growth in two plant species: common radish (Raphanus sativus) and sugarcane (Saccharum officinarum).”

 

 

Comment 5

These references are unnecessary here; please remove them

 

Answer 5

Thank you for your suggestion. We intended to explain why the plant species were used in this experiment. To clarify this problem, we have modified the sentences and added references as follows: “In this study, we examined the effect of applying a directional EMF on seed germination and growth of two different plant species: common radish (Raphanus sativus) and sugarcane (Saccharum officinarum), which were selected because of their rapid germination and easy cultivation characteristics [19, 20].”

 

 

Comment 6

If possible, please provide the names of the studied varieties and briefly describe their characteristics.

 

Answer 6

As indicated in our response to comment 5 above, we have added the characteristics (and references) of the plants used in this study.

“In this study, we examined the effect of applying a directional EMF on seed germination and growth of two different plant species: common radish (Raphanus sativus) and sugarcane (Saccharum officinarum), which were selected because of their rapid germination and easy cultivation characteristics [19, 20].”

 

 

Comment 7

Were the seeds disinfected? If so, please specify the disinfectant or agent used and the duration of the treatment.

 

Answer 7

Currently, we did not use disinfection in the experiment to minimize the effect of disinfectants. We have modified the sentence to convey why we did not apply the disinfection procedure in the experiment at line 90-91 along with the reference.   

 

“Seeds were not surface-sterilized to avoid any influence of this process on seed germination kinetics [21].”

 

 

Comment 8

Could you please specify the characteristics of the pots, their dimensions, the type of substrate used, the amount of substrate, the irrigation frequency, and the method used to determine the volume of water to be added?

 

Answer 8

We have inserted the additional information in line 100–106 as follows:

“The bobbin was then placed in a 50-mL conical tube used as a pot containing 17 g of organic soil (Jeil Co., Seoul, Korea). Seeds were placed in the pot (diameter: 30 mm, height: 115 mm) at a depth of 10 mm from the soil surface. When the system was initially set up with the seeds in it, 10 mL of tap water was added to the pot with a 10-mL serological pipette (91010; SPL Life Science, Pocheon, Korea), and both solenoid taps were connected to a DC power supply (5.0 V) to generate a directional EMF inside the pot.”

 

Further, we have added a photograph of the EMF application in working condition as Figure S1.

 

 

 

Figure S1. Photograph of the experimental plant growth control system used in this study

 

Comment 9

And humidity ? altitude ?

 

Answer 9

We included additional information related to humidity and illumination to the sentences in lines 112 to 115 as follows:

“This experimental system was maintained under a light (PAR38; Philips, Eindhoven, Holland) intensity of 90 μmol/m²/s (distance from the surface of the soil to the light: 450 mm), and a temperature of 25 ± 1 °C with 45–50% relative humidity (Figure S1).”

 

 

Comment 10

Could you please specify the characteristics of the pots, their dimensions, the type of substrate used, the amount of substrate, the irrigation frequency, and the method used to determine the volume of water to be added?

 

Answer 10

We have modified the sentence (line 102 to 107) to add more information related to dimension, irrigation frequency, and the method used to determine the volume of water to be added. Currently, no additional substrate was used for plant growth because of the short period of the experiments.

 

“Seeds were placed in a pot (diameter: 30 mm, height: 115 mm) at a depth of 10 mm from the soil surface. When the system was initially set up with seeds in it, 10 mL of tap water was added to the pot with a 10-mL serological pipette (91010; SPL Life Science, Pocheon, Korea), and both solenoid taps were connected to a DC power supply (5.0 V) to generate a directional EMF inside the pot. When the experiment was initiated, no additional watering was made.”

 

 

Comment 11

Please removed it, should be quoted in the Results section

 

Answer 11

As suggested, the sentences in lines 129 to 130 were modified as follows:  

“During cultivation, the germination rate was monitored visually and shoot elongation was measured using a caliper (Model Inoxyd, Helios, Gammertingen, Germany) [23].”

 

 

Comment 12

As an example (Figure 2), for the shoot length parameter (S. officinarum) at 120 h, there is a significant difference between 24 h and 72 h.

Please be cautious with the statistical interpretation of your results! the interpretation of the results must be reviewed

 

Answer 12

Thank you for your comment. In the results, the EMF application did not affect the germination rate. In the case of shoot length monitoring from the seed, the EMF application showed a negative effect. To clarify this expression in the results, we have modified the sentence as follows (line 174 to 176): 

“The application of an EMF during the experimental period (i.e., from seeding to shoot emergence from the soil surface) had no significant effect on the germination rate and rather had a negative effect on shoot elongation.”

 

 

Comment 13

Regarding the interpretation of results from a statistical analysis perspective, could you clarify the significant differences observed at 96 h (Y axis) between 72 h and both 24 and 48 hours for R. sativus? Additionally, please clarify the significant differences at 24 hours between 48 and 72 hours. For S. officinarum, there are significant differences between 48 and 72 h at all time points (24, 48, 72, and 96 h) on the Y-axis ...

This is a general comment applicable to all the results

 

Answer 13

Thank you for your valuable comment. In the current study, the EMF was applied for 0, 24 h, 48 h, and 72 h after germination. The 96-h EMF was not applied to the plant (after germination). In the cases of both R. sativus and S. officinarum for 72 h of EMF application (upward), the growth rates of both plants were inhibited. However, in the downward application, the 48-h application (both in the upward and downward direction) showed the highest growth from both plant species in the system. The reason for these differences is not clear. However, it is tentatively attributed to the differences in the nature of plant species. Therefore, to clarify the result interpretation, the sentences were modified as followed (line 197-221):  

“Thus, in the case of radish seedlings cultivated for 96 h after germination under an upwardly-directed EMF, the 48 h treatment had the greatest effect on shoot growth (113.43 ± 0.35 mm). This finding indicated a 25.65% ± 4.21% growth increase compared with that in the control group (i.e., no EMF application). However, the 72 h EMF treatment had a negative effect on shoot growth (-6.45% ± 8.76%), compared with that in the control treatment (Figure 3a). Conversely, EMF application promoted growth when a reversed EMF (i.e., in a downward direction) was applied to the same species (Figure 3b), but shoot growth was slightly less than that of the plants subjected to the 48 h EMF treatment in the upward direction. Notably, 72 h of EMF application in the downward direction produced a positive effect on the growth of shoot length compared to the negative result produced by the EMF application in the upward direction.

An almost identical trend was observed in sugarcane seedlings grown under the two different EMF application directions (Figure 3c). Thus, in the case of upward EMF application, the highest growth rate was observed in the 48 h treatment (105.19 ± 4.71 mm). Similarly, the 72 h EMF-treated seedlings showed a lower growth rate compared to that of the control group. In contrast, when the EMF direction was reversed (Figure 3d), the results showed an increase in growth induced by all the EMF treatment durations tested, compared to that in the controls. In particular, the 48 h EMF treatment resulted in the greatest growth (127.09 ± 1.95 mm), indicating a 38.57% ± 12.81% increase compared with that in the control group, whose final length was 92.15 ± 1.95 mm. As inferred, directional variation of EMF application with different application times influenced this growth promotion/inhibition. The possible reasons for these effects of directional EMF application may be closely related to water and nutrient transport through the xylem and/or phloem [35,36].” 

 

 

We also amended the discussion section to define the limitation of this study (line 306- 311) as follows: “In particular, our study was only related to the early stages of plant growth, while grown plants may show very different sensitivity to EMF application. Therefore, the effect of longer durations of EMF application to plants need to be verified to interpret the EMF-plant interactions. Further, conducting future studies on other growth-related physiological indicators such as photosynthetic efficiency measurements could help clarify the mechanisms by which the EMF system affects plants.”

 

 

Comment 14

Could you please expand on the discussion section of the results to provide a clearer and more detailed interpretation? This would help in better understanding and contextualizing the findings.

 

Answer 14

As previously described, the aim of the current experimental stage is to provide a primary research technique to control the plant growth. We believe that further investigation could provide more precise information on the mechanisms of EMF-plant interactions. Therefore, further studies aimed at understanding the interactions between EMF and various plants with different experimental conditions would be useful for clarifying such mechanisms. Based on your suggestion, we have added the following sentences in the discussion section (lines 307–309):

“Therefore, the effect of longer durations of EMF application to plants need to be verified to interpret the EMF-plant interactions.”

 

We truly appreciate your helpful suggestions.

 

Reviewer 4 Report

Comments and Suggestions for Authors

I think that specific directional EMF can have a positive or negative effect on the early growth of plants. However, the 96 or 168 hours conducted in this experiment are too short to prove such a hypothesis. The results shown in graphs 2 and 3 are weak in trend and the results are not enough to show the effect of directional EMF. It is necessary to analyze other growth-related factors besides shoot length through a longer period of treatment to see how they affect.

Author Response

Comment 1

I think that specific directional EMF can have a positive or negative effect on the early growth of plants. However, the 96 or 168 hours conducted in this experiment are too short to prove such a hypothesis. The results shown in graphs 2 and 3 are weak in trend and the results are not enough to show the effect of directional EMF. It is necessary to analyze other growth-related factors besides shoot length through a longer period of treatment to see how they affect.

 

Response 1

Thank you for this important comment. We agree that there are limitations in this study owing to the short EMF application period with restricted species of plants. We believe that further experiments including a long experimental period with other growth-related factors (e.g., photosynthesis activity monitoring) may reveal precise mechanisms of the EMF-plant relationship. Therefore, based on your comments, we have added following sentences to the discussion section (line 306-313):     

“In particular, our study was only related to the early stages of plant growth, while grown plants may show very different sensitivity to EMF application. Therefore, the effect of longer durations of EMF application to plants need to be verified to interpret the EMF-plant interactions. Further, conducting future studies on other growth-related physiological indicators such as photosynthetic efficiency measurements could help clarify the mechanisms by which the EMF system affects plants. Future research prospects include assessment of all these possibilities and the applicability of our method to the investigation of other plant species under different cultivation environments.”

We truly appreciate your helpful suggestions.

 

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

Accept in present form

Author Response

 

Comment 1: Accept in present form

Response 1: Thank you for your help and valuable comments.

 

Reviewer 2 Report

Comments and Suggestions for Authors

No further comments

Author Response

Comment 1: No further comments

Response 1: Thank you for your kind and valuable comments and suggestions.

Reviewer 4 Report

Comments and Suggestions for Authors

I think the manuscript could be published after revision, provided that the discussion paragraph includes comments on the current research results and future research plans, as the corresponding author mentioned. 

Author Response

Comment 1: I think the manuscript could be published after revision, provided that the discussion paragraph includes comments on the current research results and future research plans, as the corresponding author mentioned. 

 

Response 1:

Thank you for this valuable comment. We have modified the discussion section as follows (line 306 to 314):

"In particular, our study was only related to the early stages of plant growth, while grown plants may show very different sensitivity to EMF application. Therefore, the effect of longer durations of EMF application to various species of plants at different cultivation stages need to be verified to interpret the EMF-plant interactions. Further, conducting future studies on other growth-related physiological indicators such as photosynthetic efficiency measurements, plant exudates and rhizobacteria analysis could help to clarify the mechanisms by which the EMF system affects plants. Future research prospects include assessment of all these possibilities and the applicability of our method to the investigation of other plant species under different cultivation environments."

 

Again, thank you for your kind and valuable comments and suggestions.