Plant Allelopathy in Response to Biotic and Abiotic Factors
Round 1
Reviewer 1 Report
The manuscript reviews the phenomenon of allelopathy giving emphasis to how abiotic stress impact production of allelochemicals. The paper is up-to-date and brings and interesting perspective for the scientific community. However, besides minor reviews, I suggest the authors give a clearer emphasis to the distinction between what they are dubbing secondary metabolites and allelochemicals throughout the relevant discussion on the impact of abiotic stress on allelopathy as a major review.
Minor Review
L 23 - The statement seems to suggest that leaves or plants has intention. Please consider reformulate. E.g.: The release of volatiles by leaves helps the plant to deter herbivores or attract pest herbivores that attack leaves.
L 24 - "predators that attacks" check verb confusion
L 33 - "plants,animals" insert space
L 48-49 - Consider using the more general term of nitrogen-containing compounds. There are the at least 6 thousand phenolic compounds beside flavonoids such as phenylpropanoids; benzoic acids; coumarins; stilbenes, etc. The authors mention some phenolics latter but forget this huge class here.
L65-66 - Please consider rephrase this sentence for clarity.
L67 - 'playing' check verb confusion.
L76 - Check capitalization.
L84 - 'defencive' check orthography.
L100 - '(...)the role of induced allelopathy is to enable plants to enhance their (...) tolerance (...). Check major review.
L109 - 'Jasmonic'. Check capitalization.
L159 - (...)called 'biochemical plasticity. Check for a ‘so-called’ apostrophe mark, open but not closed.
L166 - 'that's' consider not use the contraction apostrophe.
L273-274 - Citation needed.
L306-309 - The authors should avoid coffering intentionality to plant behavior. Plant responses are a result of natural selection and although they has efficient consequences, the individuals are not aware of this. Here, consider the alternative writing: Allelopathic substances released by plants when attacked by insects not only directly resist insect attacks, but also attracts natural enemies of these insects, which helps plants to defend themselves against their enemies.
L322-324 - Please indicate a reference for each affirmation.
L325 - 'Studies'. Check capitalization.
L327-330 - As herbivores can also be dubbed predators (when they eat the whole plant) and foragers, the phrase "(...)repellent to approaching herbivores and increasingly attractive to foraging predators (...)" the phase may be not clear for everyone. Consider revise for enhance clarity.
L332-335 - Hard to understand, please consider rephrasing for clarity.
L366 - Or worsen...
L368 - Do you mean "(...)by environmental and biotic factors?" Otherwise, this statement seems to say the contrary of the previous sentence.
L365 (Subtitle) and L385 - Here is important to make clear what I suggest in the Major review.
L440 - The authors should discuss more about the general reasons why higher temperature induce production of allelochemicals. It may prevent the activity of pathogens and feeders, or the growth of weeds, as suggested in the case of Microcystis aeruginosa versus Chorella vulgaris, for instance?
L461 - Avoid connoting teleology for plant responses.
L490 - 'Other species cases'. Is it a title? Consider remove this sentence.
L577 - Few?
Major review
Allelopathy, as authors clearly state, is the chemical interference among living beings through chemicals. Most allelochemicals are secondary metabolites, but secondary metabolites perform many other functions in plants and living beings in general.
The concept of allelopathy has evolved throughout the time. As initially concepted by Hans Molish, in 1937, allelopathy denoted plants influencing one each other. Later, the term was extended to plants chemical influence over its community (e.g., Rice 1979) and today, the mutual chemical influence among all living beings in an ecosystem (Rice 2012). However, from the basic etymological point of view, allelopathy allelon (reciprocal), pathos (affection, suffering), during its evolution the concept conserved its original meaning of mutual influence among individuals.
Therefore, allelopathy encompass plants seducing a pollinator insects by mimetizing a pheromone, producing a sweet nectar, or an attractive anthocyanin. Like this, allelopathy also encompass plants repelling or killing their predators or pathogens with toxins. However, epistemologically, there is a gray area there. It is not that obvious where allelopathy stops and plant immunology starts. Plants do not exactly ‘communicate’ with pathogens; they just try to get rid of them.
In addition, the production of an allelochemical is not always related with allelopathy. Ferulic acid is also an import allelochemical with a hundred of papers examining its properties, ecophysiological roles, and mechanisms of action. But ferulic acid is also an important antioxidant, osmolyte involved in salt stress, and a constitutive structural component in type II cell walls of grasses. Besides, several plants produce ferulic acid to protect their epidermic tissues against UV radiation, similarly as humans produce melanin when exposed to sun. This phenomenon is not allelopathic, but simple stress acclimatation to UV light.
Therefore, the authors should be more explicit and cautious when approaching the concept of plants producing ‘allelochemical’ in response to abiotic stress. It can be sound like a sophism if I simply say that plant create allelochemical in response to light. Maybe, plants are just producing sunscreen that eventually have to be allelochemical implications. I understand that it is the general intention behind the authors text. And the authors make it quite clear in the conclusion remarks. However, I strongly recommend that you do it better at the end of the text of the subitem 3. Environmental factors. Instead of the last sentence I recommend a broader discussion on the theme summed up there. It is true that plants produce secondary metabolites in response to abiotic stress. And it is also true that many of these metabolites perhaps most of them are potentially implicated in allelopathic interactions. But it is also equally important highlight that some of them may not be and are specifically related to damage control and each hypothetical allelopathic interference must be experimentally demonstrated. The authors make it clear after in the text that the allelopathic interference during stress might be especially relevant for plant survival, since at the edge of temperature, water, nutrient, light or CO2 competition, herbivores and pathogens might be critical. It would make clear for the readers why the authors use production of secondary metabolites and allelochemicals almost as synonymous in the following writing. In conclusion, the paper is relevant, is worth to be published but must receive this final refining before being published.
It seems ok, but I am not a native English speaker and indicated the errors I found.
Author Response
Dear Reviewer
Thank you very much for reviewing our manuscript carefully. These comments are all valuable and very helpful for improving the quality of our manuscript and have provided significant guidance for our studies. Point to point response is uploaded in attached word document below.
Author Response File: 
Author Response.pdf
Reviewer 2 Report
The manuscript entitled “Allelopathy in response to biotic and abiotic factors” is a review article that partially fills this important topic, although similar published papers are already available. The subject provides some interesting aspects. However, the manuscript shows severe gaps and weaknesses that make it not acceptable in its present form. With regret, I therefore suggest to reject the paper.
Please see my comments and suggestions that have the only purpose of improving the overall quality of the manuscript.
GENERAL COMMENTS
· Overall, the level of English language, grammar and style is low and it needs to be enhanced with the help of a mother-tongue and professional proof-reader.
· In my opinion, the review is too focused on biotic factors (about three-fourths of the length), whereas poor attention is provided on abiotic stress factors, on which there is a wide literature available. I therefore suggest balancing more the whole manuscript.
· I have some concerns about the novelty level. In fact, other papers have been already published about the effects of biotic and abiotic factors on allelopathy, although they are not cited. See for instance:
§ Scavo, A.; Restuccia, A.; Mauromicale, G. Allelopathy: General principles and basic aspects for agroecosystem control. In Sustainable Agriculture Reviews; Gaba, S., Smith, B., Lichtfouse, E., Eds.; Springer: Cham, Switzerland, 2018; Volume 28, pp. 47–101.
§ Bakhshayeshan-Agdam, H., Salehi-Lisar, S.Y. (2020). Agronomic Crops Response and Tolerance to Allelopathic Stress. In: Hasanuzzaman, M. (eds) Agronomic Crops. Springer, Singapore. https://doi.org/10.1007/978-981-15-0025-1_17
§ Pedrol, N., González, L., Reigosa, M. (2006). Allelopathy and abiotic stress. In: Reigosa, M., Pedrol, N., González, L. (eds) Allelopathy. Springer, Dordrecht. https://doi.org/10.1007/1-4020-4280-9_9
§ Gawronska H., Golisz A. (2006). Allelopathy and biotic stresses. In: Reigosa, M., Pedrol, N., González, L. (eds) Allelopathy. Springer, Dordrecht. https://doi.org/10.1007/1-4020-4280-9_10
· Therefore, what is the novelty level? What are the differences with the previous published papers? Nothing is mentioned
· In my opinion, references are not used correctly. There are many and many outdated and not pertinent citations (e.g. 1, 2, 10, 17, 18, and so on), while other more appropriate and recent references are not included. This means that literature search was not carried out properly
· Following my two previous comments, nothing is reported about the methodology of literature search (databases, keywords, criteria of exclusion/inclusion, etc.). This is an important aspect of review articles
· Another important aspect of review article is the presence of figures and tables. This manuscript shows only two Figures that do not provided anything new compared to the text. Some detailed Figures about some physiological mechanism or the presence of Tables summarising the effects of some research papers on the allelopathic expression would have been useful
SPECIFIC COMMENTS:
· Title: I suggest adding “Plant” Allelopathy, since this biological phenomenon encompasses different living organisms
· L15: I think that “inhibition” is more appropriate than “exclusion”
· L26: please write CO2 subscript
· keywords are not much pertinent in my opinion (especially “induce”), since they repeat the same words as the title. On the contrary, keywords are commonly different from title in order to increase the visibility of the manuscript on wed databases
· L32-35: the sentence shows grammatical mistakes (the verb is lacking). In addition, the definition provided by the International Allelopathy Society is “any process involving secondary metabolites produced by plants, microorganisms, viruses, and fungi that influence the growth and development of agricultural and biological systems”. The two provided references of Rice are not valid in this case
· L35-38: Also, this sentence is grammatically wrong. Moreover, this is not always true. Please keep in mind that there are two types of allelopathy: true (or direct) and functional (or indirect) allelopathy. In true allelopathy, any transformation of allelochemicals in the environment happen.
· Perhaps, once released into the soil, allelochemicals interact with the physical, chemical and biological soil characteristics that affect their retention, transformation and transport processes and, consequently, their phytotoxic level (https://doi.org/10.1007/s11104-019-04190-y)
· L38: I suggest using always throughout the manuscript the terms “donor plants” and “target plants”
· L38: Previously? When? Please be more specific
· Why writing Allelopathy and the name of chemical classes (e.g. Flavonoids) with capital letters?
· L49-59: this part is not relevant for this review. It could be summarised with one single sentence explaining that allelochemicals belong to a wide range of chemical classes
· L67-68: the verb is wrong
· The background provided in the introduction is not appropriate. What are the goals of this review? What are the differences with the available literature? How the literature search was carried out?
· ABIOTIC FACTORS: the authors did not discuss the effect of shading. For instance, it was found that 60% plant shading in cultivated cardoon increased the sesquiterpene lactone content and phytotoxicity of its leaf extracts (Scavo et al. 2020. https://doi.org/10.1021/acs.jafc.0c03527)
· BIOTIC FACTORS: other biotic factors not discussed here are plant age and plant part, which highly affect the quali-quantitative composition of donor plant allelochemicals. See for instance https://doi.org/10.3390/plants11081021
The manuscript shows many grammatical mistakes and misleading sentences. It will benefit of an important linguistic revision by a mother-tongue proof-reader.
Author Response
Dear Reviewer
thank you very much for reviewing our manuscript. The comments were very valuable and helpful for revising and improving our manuscript and have provided significant guidelines for our studies. We have studied your comments carefully and made corrections which we hope to meet with approval. Point to point response is uploaded in attached word file below
Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
I am satisfied with the authors' improvements of the revised manuscript. The Figure 1 works as an elegant graphical abstract. I disagreed with with the legend: 'Biotic and abiotic factors induce plants to produce allelopathy', since allelopathy is not a product, but rather a relationship mediated by chemicals. The editor and author may consider it is rather a preciosism and I would be glad to see the paper published just as it is. Nonetheless, I would prefer to see the legend changed to something like "Stress factors that affect allelopathy", which would also work as a good running title to the manuscript.
Author Response
Dear Reviewer,
Thank you very much for reviewing our manuscript carefully. These comments are valuable and very helpful for revising and improving our manuscript and have provided significant guidance for our studies. We have studied your comments carefully and made corrections which we hope to meet with approval. Point to point response is uploaded in attached word document below.
Author Response File: Author Response.pdf
Reviewer 2 Report
The authors addressed most of my comments and suggestions, thus improving the overall quality of the manuscript.
I would like to highlight some minor comments that still need to be incorporated into the text:
- references are not written according to journal guidelines. Please check it
- L36 and 37: the Greek words are "allelon" and "pathos"
- Please note that the right name is "International Allelopathy Society". Check throughout the manuscript
- L572 can be deleted
- Please write the binomial names in full (including the taxonomist, written not in italics) on they first appearance, then abbreviated. For instance: Cynara cardunculus L. the first time, C. cardunculus from the second time onwards
- I am not satisfied about your answer on the novelty level. I still not understand what the novelty level is. Please specify better, at the end of the introduction, the differences with the review articles previously published on this topic
- In my opinion, carrying out a literature search on just one database and with only two keywords is not sufficient. I invite the authors to perform a more accurate literature search and specify the total number of initial papers and the criteria of inclusion/exclusion
- Following my previous comment on the first round of revision, I invite the authors to add (if possible) two summarising tables (one for abiotic and the other one for biotic factors) with some examples taken from the text. You could add the following columns: Factor, Target Plant, Description, Reference
Author Response
Dear Reviewer,
Thank you very much for reviewing our manuscript carefully once again. These comments are all valuable and very helpful for improving the quality of our manuscript and have provided significant guidance for our studies. Point to point response is uploaded in attached word document below.
Author Response File: Author Response.pdf
Round 3
Reviewer 2 Report
Dear Authors, I have no further comments. I hope my suggestions were useful to improve the quality of your manuscript. Best wishes
Minor editing
