Biostimulants on Crops: Their Impact under Abiotic Stress Conditions
Round 1
Reviewer 1 Report
Franzoni and colleagues submitted a review on "Biostimulants and their impact on crops under biotic stress". Indeed, biostimulants are an important topic, but I feel that the manuscript deserves some more rework before it is ready for publication. I strongly encourage the authors to revise the manuscript thoroughly before resubmit it to Horticulturae. Some paragraphs are too general and should be more elaborated e.g. 2.4.. Sometimes I lost track while reading. There is a long explanation about the basics of Metabolomics starting in line 467. This information is far beyond the scope of the review. Why not restructure the paper and combine chapter 2 and chapter 3 for example?
Further comments:
Title: Biostimulants and impact on crops under biotic stress. Do the authors mean: Biostimulants and their impact on crops under biotic stress?
Line 9: biostimulants -> Biostimulants
Line 15: In this review, an overview of the biostimulants and their effects have been reported and insight molecular studies have been discussed. Revise sentence.
Line 19-20: “…innovative sensors and data analysis..” is written in the abstract, but innovative sensors are not discussed in the following paragraphs. Why do the authors mention them in the abstract?
Line 33: EU n. 1009/2009? -> 1009/2019; References for regulations need to be added in the text as well.
Line 54-55: To make biostimulants more and more stable.. This phrase is not clear to the reader. I assume the authors wanted to state that the effect of biostimulants should be more stable, right?
Line 58: “Over the years, several authors have proposed different classifications of biostimulants based on their origin, main component, or mode of action [3].” Why only one reference is given then in the text?
Line 63: Biostimulants are classified into these main groups. The reference that is given is from 2015: du Jardin, P. Plant Biostimulants: Definition, Concept, Main Categories and Regulation. Scientia Horticulturae 2015. To me it is not clear from the manuscript whether the authors concentrate on biostimulants by definition according the new regulation EU 1009/2019 or in a broader context.
Line 152, Table 1: Please add references to the table.
Line 215: There is only one subchapter for chapter 4. Are there some subchapters missing in the submitted manuscript? It appears a bit strange to the reader. What about other secondary metabolites? Volatiles, hormones?
e.g. https://doi.org/10.3390/plants10081623; https://dx.doi.org/10.3389%2Ffpls.2020.567388; https://doi.org/10.3390/pathogens10070797
Line 234: EBIC. Please provide the full name.
Line 340: The authors state that: “RNA-seq approach is used not only to clarify the mode of action of commercial biostimulant products with a known efficacy, but it might become a successful strategy to develop new products.” Then, in line 347 they authors write about metabolites not about transcripts. This needs to be clarified.
Line 249-250: .”.on model plants such as Arabidopsis or Micro-tom and other non-model species.” The authors should use the term Arabidopsis thaliana or do they talk about other Arabidopsis as well? Moreover, not all readers are familiar with the term Micro-tom, better write “tomato cultivar Micro Tom”.
The authors conclude that: “The omics approach can provide fast and reliable data that can link the crop’s responses and its performance under different environmental conditions.” What I really do miss in the manuscript is the discussion about the meaning of well-designed, repeated glasshouse and field experiments that are the foundation of all the omics analysis.
Please also check the reference list for spelling mistakes.
Author Response
Dear Reviewer,
first of all, I would like to thank you for your useful suggestions.
To improve the readability of the manuscript, after the addition of a few new references, we have reported only the revised list of the references in the References section. Similarly, we have removed the old figure 1 substituting it with the revised one.
I would like to inform you that all revisions were done by using the “track changes” function and are visible in the revised version of the manuscript.
We have revised the text on the basis of all the suggested corrections, in detail:
Responses to the comments and suggestions
Comments and Suggestions for Authors
Franzoni and colleagues submitted a review on "Biostimulants and their impact on crops under biotic stress". Indeed, biostimulants are an important topic, but I feel that the manuscript deserves some more rework before it is ready for publication. I strongly encourage the authors to revise the manuscript thoroughly before resubmit it to Horticulturae. Some paragraphs are too general and should be more elaborated e.g. 2.4.. Sometimes I lost track while reading. There is a long explanation about the basics of Metabolomics starting in line 467. This information is far beyond the scope of the review. Why not restructure the paper and combine chapter 2 and chapter 3 for example?
Response:
According to your suggestion we have revised all parts of the manuscript to present more detailed information. To support the new sentences, we have cited further articles. Moreover, we reduced the part regarding the presentation of metabolomics basis.
Further comments:
Title: Biostimulants and impact on crops under biotic stress. Do the authors mean: Biostimulants and their impact on crops under biotic stress?
Response: thank you for the comment. We have modified the title. We think that it is clearer now.
Line 9: biostimulants -> Biostimulants
Response: Done.
Line 15: In this review, an overview of the biostimulants and their effects have been reported and insight molecular studies have been discussed. Revise sentence.
Response: Thank you for the comment. The sentence has been revised
Line 19-20: “…innovative sensors and data analysis..” is written in the abstract, but innovative sensors are not discussed in the following paragraphs. Why do the authors mention them in the abstract?
Response: The sentence has been removed.
Line 33: EU n. 1009/2009? -> 1009/2019; References for regulations need to be added in the text as well.
Response: The link has been added.
Line 54-55: To make biostimulants more and more stable. This phrase is not clear to the reader. I assume the authors wanted to state that the effect of biostimulants should be more stable, right?
Response: It is right. We modified the sentence.
Line 58: “Over the years, several authors have proposed different classifications of biostimulants based on their origin, main component, or mode of action [3].” Why only one reference is given then in the text?
Response: We have added new references concerning the origin, main component, or mode of action of biostimulants.
Line 63: Biostimulants are classified into these main groups. The reference that is given is from 2015: du Jardin, P. Plant Biostimulants: Definition, Concept, Main Categories and Regulation. Scientia Horticulturae 2015. To me it is not clear from the manuscript whether the authors concentrate on biostimulants by definition according the new regulation EU 1009/2019 or in a broader context.
Response: The review also takes in consideration compounds that can be used as potential biostimulants.
Line 152, Table 1: Please add references to the table.
Response: As suggested, we have added the references.
Line 215: There is only one subchapter for chapter 4. Are there some subchapters missing in the submitted manuscript? It appears a bit strange to the reader. What about other secondary metabolites? Volatiles, hormones?
e.g. https://doi.org/10.3390/plants10081623; https://dx.doi.org/10.3389%2Ffpls.2020.567388; https://doi.org/10.3390/pathogens10070797
Response: According to your comment, we have expanded this part. More information has been added regarding some of the main classes of secondary metabolites, including phenolic compounds and glucosinolates. All the references suggested have been added to improve the quality of this section.
Line 234: EBIC. Please provide the full name.
Response: Done.
Line 340: The authors state that: “RNA-seq approach is used not only to clarify the mode of action of commercial biostimulant products with a known efficacy, but it might become a successful strategy to develop new products.” Then, in line 347 they authors write about metabolites not about transcripts. This needs to be clarified.
Response: Thank you for the correction, the text has been revised
Line 249-250: .”.on model plants such as Arabidopsis or Micro-tom and other non-model species.” The authors should use the term Arabidopsis thaliana or do they talk about other Arabidopsis as well? Moreover, not all readers are familiar with the term Micro-tom, better write “tomato cultivar Micro Tom”.
Response: Done.
The authors conclude that: “The omics approach can provide fast and reliable data that can link the crop’s responses and its performance under different environmental conditions.” What I really do miss in the manuscript is the discussion about the meaning of well-designed, repeated glasshouse and field experiments that are the foundation of all the omics analysis.
Response: A specific section has been added at the end of the manuscript, taking into consideration the experimental design and minimum requirements for data analysis.
Please also check the reference list for spelling mistakes.
Response: We checked all references
Reviewer 2 Report
- A major issue in this review is the English writing. There are many places in the text where the writing should be refined. The text should undergo English editing.
- When mentioning regulations, details of the regulatory body and the topic of regulation should be mentioned. In line 11 in the abstract here is a mention of regulation with no such information so it is not clear what regulations the authors are referring to.
- In section 2 the authors present several ways to classily bio stimulants. At the introductory paragraph to this section it is written that "The current classification is based on the source of raw materials even if this choice does not always provide the correct information on the biological activity of the product.". It is not clear and should further detailed what classification are the authors referring to. For example a certain specific legal classification, or conventional scientific classification? Or other?
- There are issues with scientific terminology in the manuscript. The text should edited for correct scientific terminology. For example in line 66 "algae brown, red and green", the correct terminology is brown algae, etc.
- The sub-sections in section 2 2.1-2.5 present various classes of biostimulants. The discussion of each group is not in-depth enough , and lacks sufficient references to published studies.
- The information presented in table 1 should be backed up by reference. Each mode of action, and reported effect, should be backed up by a scientific reference.
- The information presented in section 3.1 is not backed up by sufficient references. Much of the written information do not refer to the publication The same applied also to the sext section – salinity stress and to section 3.3. Also, section 3.1 should not be focused only on Mediterranean areas. Drought stress is not limited to these region of the world.
- The text describing Biostimulant-induced accumulation of secondary metabolites and their role against abiotic stresses (section 4) is not robust enough. There are many groups of secondary metabolites that were shown to be affected by biostimulants, but the authors only present and discuss effects on carotenoids. Effects on other groups of secondary metabolites should be discussed and presented. Some examples out of many arehttps://doi.org/10.1016/j.jarmap.2018.11.004; cannabinoids: https://doi.org/10.3389/fpls.2019.00736, withanolides 116: 283-9. (2015) ; terpenoids: Plants 8(12):534
- In Figure 1: the list of physiological parameters suggested to be evaluated is very restricted. No justification is given to why only these specific limited parameters chosen to represent the physiology aspect.
Author Response
Dear Reviewer,
first of all, I would like to thank you for your useful suggestions.
To improve the readability of the manuscript, after the addition of a few new references, we have reported only the revised list of the references in the References section. Similarly, we have removed the old figure 1 substituting it with the revised one.
I would like to inform you that all revisions were done by using the “track changes” function and are visible in the revised version of the manuscript.
We have revised the text on the basis of all the suggested corrections, in detail:
Responses to the comments and suggestions
- A major issue in this review is the English writing. There are many places in the text where the writing should be refined. The text should undergo English editing.
Response: We checked the manuscript carefully to improve the quality of the text as well as to correct English editing mistakes.
- When mentioning regulations, details of the regulatory body and the topic of regulation should be mentioned. In line 11 in the abstract here is a mention of regulation with no such information so it is not clear what regulations the authors are referring to.
Response: It has been removed since we agreed that the mention in the abstract is not appropriate
- In section 2 the authors present several ways to classily bio stimulants. At the introductory paragraph to this section it is written that "The current classification is based on the source of raw materials even if this choice does not always provide the correct information on the biological activity of the product.". It is not clear and should further detailed what classification are the authors referring to. For example a certain specific legal classification, or conventional scientific classification? Or other?
Response: In our opinion, the biostimulants can have different origins, we focused on materials that can be classified as biostimulants even if they are not currently classified by regulation as biostimulants. We think that in the future the research works can provide information for including in the official biostimulants compounds or microorganisms that currently are not included. This approach was used in the review.
- There are issues with scientific terminology in the manuscript. The text should edited for correct scientific terminology. For example in line 66 "algae brown, red and green", the correct terminology is brown algae, etc.
Response: We have checked the scientific terminology.
- The sub-sections in sections 2 2.1-2.5 present various classes of biostimulants. The discussion of each group is not in-depth enough and lacks sufficient references to published studies.
Response: Addition references have been added through the manuscript and the text has been improved.
- The information presented in table 1 should be backed up by reference. Each mode of action, and reported effect, should be backed up by a scientific reference.
Response: As also suggested by Reviewer 1, we have added the references in Table 1.
- The information presented in section 3.1 is not backed up by sufficient references. Much of the written information do not refer to the publication The same applied also to the sext section – salinity stress and to section 3.3. Also, section 3.1 should not be focused only on Mediterranean areas. Drought stress is not limited to these region of the world.
Response: The text has been revised.
- The text describing Biostimulant-induced accumulation of secondary metabolites and their role against abiotic stresses (section 4) is not robust enough. There are many groups of secondary metabolites that were shown to be affected by biostimulants, but the authors only present and discuss effects on carotenoids. Effects on other groups of secondary metabolites should be discussed and presented. Some examples out of many are https://doi.org/10.1016/j.jarmap.2018.11.004; cannabinoids: https://doi.org/10.3389/fpls.2019.00736, withanolides 116: 283-9. (2015) ; terpenoids: Plants 8(12):534
Response: According to your comment, we have expanded this part. More information has been added regarding some of the main classes of secondary metabolites, including phenolic compounds and glucosinolates. About the papers suggested by the reviewer, we decided not to include “Plants 8(12):534”, because methyljasmonate is usually referred as a plant regulator/elicitor/hormone, and it could not be included in the category of biostimulants. Unfortunately, we were not able to find the reference suggested as: “with anolides 116: 283-9”, but we added several new references to improve the robustness of this paragraph.
- In Figure 1: the list of physiological parameters suggested to be evaluated is very restricted. No justification is given to why only these specific limited parameters chosen to represent the physiology aspect.
Response: We reported the main parameters that currently are studied in the characterization. Accepting the suggestion, we have however added other parameters.
Round 2
Reviewer 1 Report
Clearly, the manuscript has been improved.
Some statements are still diffuse and must elaborated in detail for example:
Many experimental tests have highlighted that the applications of protein hydrolysates of both animal and plant origin can improve the growth of crops and their tolerance to abiotic stresses.
Explain "many" with more substantial information on the tests.
Some biostimulants obtained from seaweed extracts can increase the accumulation in the cells of osmotically active compounds.
Which are the "some" biostimulants?
The crops of some coastal areas may be subject to saline stress due to the high concentration of soluble salts in the irrigation water or in the soil.
What are the "some" coastal areas? Define.
Some biostimulants have shown ability to counteract the plant growth reduction of under cold stress by increasing osmolytes (osmotically active substances), antioxidant compounds and substances that protect the cytoplasmic cell membranes.
Name the "some biostimulants" and explain them.
There can be more of these examples find in the manuscript. Please revise the text carefully and define "some", "many"
Please add references for the following statements:
Non-microbis a review. al biostimulants are obtained from different organic matrices subjected to different extraction processes that allow to concentrate bioactive compounds responsible for increasing the growth or tolerance of the crop to adverse environmental conditions.
Seaweeds are a large group including macroscopic marine algae and multicellular algae belonging to different taxonomic group, such as algae brown, red and green algae.
The algae used for the production of biostimulants contain plant hormones such as cytokines and auxins or other hormone-like substances.
Humic substances mainly comprise humic and fulvic acids. Treatments with humic substances can stimulate the growth and development of plant roots.
This group mainly includes bacteria, yeasts, and filamentous fungi.
In the last fertilizers the microorganisms recognized as biostimulants are. Azotobacter spp., Mycorrhiza, Rhizobium spp., and Azospirillum spp.
Chemical elements that promote plant growth and which can be not essential for all plants are called beneficial elements.
The reduction in water availability directly affects the photosynthetic activity and affecting the leaf gas ex-changes.
Some biostimulants obtained from seaweed extracts can increase the accumulation in the cells of osmotically active compounds in cells and increase the absorption capacity of plantsthat contribute to buffer the changes in the water status of plants.
This list can be easily contiuned, so please revise the text carefully and add references to your statements.
Author Response
Response to Reviewer 1
Dear Reviewer,
to improve the readability of the manuscript, we have accepted all changes of the previous version and then we have used the “track changes” function to make visible the new modifications introduced into the manuscript. To permit a better comprehension, after the addition of the new references, we have reported only the revised list of the references in the References section.
We have revised the text on the basis of all the suggested corrections, in detail:
Responses to the comments and suggestions
Clearly, the manuscript has been improved.
Authors Answer (A.A.): I would like to thank you for your positive judgement of the MS and for your useful suggestions.
Some statements are still diffuse and must elaborated in detail for example:
Many experimental tests have highlighted that the applications of protein hydrolysates of both animal and plant origin can improve the growth of crops and their tolerance to abiotic stresses.
Explain "many" with more substantial information on the tests.
Some biostimulants obtained from seaweed extracts can increase the accumulation in the cells of osmotically active compounds.
Which are the "some" biostimulants?
The crops of some coastal areas may be subject to saline stress due to the high concentration of soluble salts in the irrigation water or in the soil.
What are the "some" coastal areas? Define.
Some biostimulants have shown ability to counteract the plant growth reduction of under cold stress by increasing osmolytes (osmotically active substances), antioxidant compounds and substances that protect the cytoplasmic cell membranes.
Name the "some biostimulants" and explain them.
There can be more of these examples find in the manuscript. Please revise the text carefully and define "some", "many"
A.A.: We have revised all the sentences that were still too generic.
Please add references for the following statements:
Non-microbis a review. al biostimulants are obtained from different organic matrices subjected to different extraction processes that allow to concentrate bioactive compounds responsible for increasing the growth or tolerance of the crop to adverse environmental conditions.
Seaweeds are a large group including macroscopic marine algae and multicellular algae belonging to different taxonomic group, such as algae brown, red and green algae.
The algae used for the production of biostimulants contain plant hormones such as cytokines and auxins or other hormone-like substances.
Humic substances mainly comprise humic and fulvic acids. Treatments with humic substances can stimulate the growth and development of plant roots.
This group mainly includes bacteria, yeasts, and filamentous fungi.
In the last fertilizers the microorganisms recognized as biostimulants are. Azotobacter spp., Mycorrhiza, Rhizobium spp., and Azospirillum spp.
Chemical elements that promote plant growth and which can be not essential for all plants are called beneficial elements.
The reduction in water availability directly affects the photosynthetic activity and affecting the leaf gas ex-changes.
Some biostimulants obtained from seaweed extracts can increase the accumulation in the cells of osmotically active compounds in cells and increase the absorption capacity of plantsthat contribute to buffer the changes in the water status of plants.
This list can be easily contiuned, so please revise the text carefully and add references to your statements.
A.A.: According to your suggestions, we introduced new references to support better these and others sentences as well as we revised all parts of the manuscript.
Reviewer 2 Report
The manuscript was greatly improved. An issue remained that needs to be be corrected is that the information in the various subsections of biostimulant classes is still not backed up by sufficient reference. You should avoid making claims which you do not support by scientific results. There are many cases in this text that information presented is not backed up by references. https://doi.org/10.1016/j.phytochem.2015.02.029This is the reference to the ms which was not fully detailed in my previous comments.
Author Response
Response to Reviewer 2
Dear Reviewer,
to improve the readability of the manuscript, we have accepted all changes of the previous version and then we have used the “track changes” function to make visible the new modifications introduced into the manuscript. To permit a better comprehension, after the addition of the new references, we have reported only the revised list of the references in the References section.
We have revised the text on the basis of all the suggested corrections, in detail:
Responses to the comments and suggestions
The manuscript was greatly improved.
Authors Answer (A.A.): I would like to thank you for your positive judgement of the MS and for your useful suggestions.
An issue remained that needs to be corrected is that the information in the various subsections of biostimulant classes is still not backed up by sufficient reference. You should avoid making claims that you do not support by scientific results. There are many cases in this text that the information presented is not backed up by references.
A.A.: According to your suggestion, we introduced new references to support better these and others sentences as well as we revised all parts of the manuscript.
https://doi.org/10.1016/j.phytochem.2015.02.029 This is the reference to the ms which was not fully detailed in my previous comments.
A.A.: We read the suggested paper and we reported that Withania somnifera could be a potential source of bioactive compounds to be used as potential biostimulant (2.2). We also mention the paper in section 4, when describing the mode of action by which biostimulants and elicitors could stimulate the production of secondary metabolites).
Round 3
Reviewer 1 Report
The manuscript has been carefully revised. I am fine with it.
Author Response
we agree with your comment. In accordance with it, we modified the last part of the abstract as well as we improved the conclusion section adding a sentence. To better support this aspect, we also added a reference (ref 124).
Hoping that the MS is now suitable for publication in Horticulturae,
