Ulvan in Agriculture: An Eco-Friendly Approach to Plant Disease Management

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

see attached

Comments for author File: Comments.pdf

Comments on the Quality of English Language

Generally good, though there are a few instances of failure of making cogent logical connections between adjacent sentences.

Author Response

Reviewer 1:

Reviews should do more than simply list items in the existing literature. An attempt should be made to synthesise a comprehensive overview of the state of research in the area being reviewed, indicating gaps in knowledge and prospects for future work.

Response: We sincerely thank the reviewer for dedicating time to our manuscript and for providing meaningful insights that have greatly improved the quality of our work. In response to the suggestions, we have thoroughly revised the manuscript: the Introduction has been rewritten to provide clearer context and focus, and a new Section 9.1 has been added to strengthen the discussion and address the reviewer’s concerns.

 

This review has a significant amount of repetitive content both within itself and from previous reviews, e.g., refs 11 and 14. One case in point is that the conclusion to this review ('future work') mostly simply reiterates issues that have been canvassed in previous reviews or are completely obvious from the lack of supporting data to the many assertions made. What is presented as conclusions should have been introduced at the beginning of the manuscript, followed by a description of how the content of the review was going to either address the issues or work around the gaps in knowledge. An example is the lack of a scientifically useful definition of 'ulvan'. As a result, we are left with an amorphous entity called ulvan and a list of biological activities coalescing into a rather meaningless blob.

Response: We thank the reviewer for their valuable feedback. The manuscript has been thoroughly revised to remove repetitive content and overlapping discussions. The conclusion has been restructured to provide a more rigorous and focused analysis, and the future direction section has been separated with clearer definitions and targeted discussion of Ulvan’s role, ensuring originality and scientific clarity.

This review could usefully be improved by the authors adhering more closely to the title of the review, viz., use of ulvan in agriculture, and removing all but the barest minimum covered in previous reviews and material not directly relevant to agricultural applications. Then the authors could discuss the use of ulvan in agriculture and provide supporting information on how it was proven or shown that the application of ulvan showed a statistically significant improvement over previous treatments. If no such data is extant, then perhaps it is too early for a review such as this.

Response: We thank the reviewer for this important feedback. The manuscript has been revised to align more closely with the title, focusing specifically on ulvan’s agricultural applications. Redundant material and content not directly relevant have been removed, and the discussion now emphasizes available data on agricultural efficacy while clearly acknowledging areas where supporting evidence is limited.

 

Other general comments:

A lot of use of bland descriptors (adjectives) that do not elicit cogent meaning, typical of AI-generated text.

Many 'guesses' are made about cause and effect between ulvan and observed activity but they generally provide no more insight than an interested reader will provide for themselves.

Tables (and figures) must be constructed so they can 'stand-alone' and are comprehensible without reference to the main text. Thus, particularly column headings should be clearly and precisely defined. E.g. see below for line 181.

There seems to be a general assumption when making comparisons, that all ulvan is structurally the same and it is surrounded by the same matrix in all Ulva spp. despite that it is stated otherwise elsewhere.

I did not find a number of the figures added anything to the understanding of the content.

Response: We have thoroughly revised the manuscript as per the suggested comments.

 

Line 19: Comment

When 'Ulva' refers to the genus, format in italics. All genus and species names should be italicized.

Response: Correctly pointed out by the reviewer, we have italicized Ulva in the revised manuscript.

 

20 ulvan, the compound name, does not have an initial upper-case letter (unless at the beginning of a sentence)

Response: We have lowered the ulvan “U” in the revised submission.

 

34 I would prefer 'algae' over 'seaweed' in the keywords

Response: As suggested, we have replaced the seaweed with algae in the keywords in the revised submission.

 

42 Suggest: The very high cost and environmental risk associated with synthetic chemicals …When nominating chemicals as 'artificial', 'synthetic' is a more accurate descriptor.

Response: Reviewer marked corrected, and as suggested, we have replaced the “artificial” word with “synthetic” in the revised manuscript.

 

48 Delete: agriculture-based

Suggest: … plant diseases that affect agriculture. Green macro-algae in the Uvales family …

Response: Omitted the word in the revised submission.

 

59 Suggest: Since it is a polysaccharide, which …

However, the polysaccharide nature of ulvan does not automatically convey non-toxicity to 'other creatures. The sentence should be deleted or changed to make better logical sense.

Response: As correctly pointed out by the reviewer, we have deleted these sentences “Since it has a polysaccharide nature, which is easily decomposed by microbes and has less persistence in the environment, it is non-toxic to other creatures except its target organisms” in the revised manuscript.

 

65 There are many unsupported assertions made above without references.

Response: We have revised the manuscript and, for validation, added specific references as well. 

 

82 There is very loose use of the words 'chemical' , 'synthetic' and 'artificial', which appear to inserted for effect rather than as useful scientific descriptors.

The references quoted make no logical connection between ulvan [chemical] structure and 'numerous biological and agricultural uses' as suggested in the text. Such biological activity has been found but there is no indication of structure-activity relationship(s).

Response: We have done language editing for the whole manuscript and tried to present a more analytical and in-depth discussion.

 

84 'degraded': The use of this word in the context of soil is normally used to indicate loss of agricultural (or flora) potential due to loss of nutrients and/or soil structure, not due to the presence of residual pesticides, among other things.

Response: We have “deleted” the term and added “amending soil nutrient dynamics” for the formation of a more meaningful sentence. 

 

96 1. The transition between the previous paragraph and this one is non-existent.

2. The first 4 lines or so are a word salad—re-write so that the sentences are logically connected or may be anticipated by the foregoing one.

Response: We have revised the whole introduction and tried to create a logical flow in the manuscript.

 

107 The second Colletotrichum can be abbreviated as C.

Response: Full names are used now.

 

108 alfalfa anthracnose should be in roman font

Response: Font changed

 

112 Delete 'Somehow'

Response: Deleted

 

154 lower case 'B'

Response: Lowered the case

 

181 How is the 1.1% calculated? based on wet weight, air-dried weight, lyophilized weight? Are all the % shown in Table 1 calculated in the same way?

Response: In Table 1, calculation has been done using the following formulae:

 Ulvan Yield (%) Formula + Calculation Method

Standard Formula (Dry Weight Basis)

Ulvan yield is almost always calculated on a dry weight (DW) basis in the literature:

Ulvan Yield (%)=Weight of extracted ulvan (dry)Weight of dried Ulva biomass×100Yield (%)=W2W1×100

• We have mentioned this in our revised manuscript along with the references. As multiple manuscripts followed by the same formulae for the calculation [64] [54], [34], [67], [68] [7], [11], [60]. 

 

199 Sentence starting with 'Owing to' makes no logical sense—re-word. 

Response: Omitted “owing” in the revised submission.

 

Table 2 How is 'mole%' calculated?

Response: Conversion to molar amounts

• The measured mass (mg) of each sugar is converted into moles using its molecular weight: moles of sugar=mass of sugar (mg)/molecular weight (g/mol)

     Calculation of mole percentage

• The mole percentage of each sugar is then calculated relative to the total moles of all sugars: mol% of sugar=moles of sugar/ total moles of all sugars×100

 

Table 3 Entries require references.

Response: We have added the specific references in the revised manuscript to support the Functional Significance of Chemicals in Table no-3.

 

Figure 3 Why are some structures shown as pyranoses and others as alditols?

Response: We thank the reviewer for raising this point. The choice of representing some monosaccharides as pyranoses and others as alditols reflects the conventions used in structural carbohydrate analysis. 

To improve clarity, we have revised the figure legends and text to explicitly state why certain sugars are represented as pyranoses and others as alditols, ensuring consistency and avoiding confusion for readers unfamiliar with these conventions.

 

Which stereoisomers are they (/, D/L) and carefully check that the correct structures are shown.

Close up ulvanobiuronic legend Suggest: Structures of the main monomers that constitute the disaccharides

Response: We have revised as suggested.

 

242 Discussion of the biosynthesis is not relevant to the topic.

Response: As suggested, we have reduced the section.

 

271   If this section is to be included, as it stands, the only useful information that can be conveyed is a list of extraction methods and their pros and cons. Inclusion of yields are meaningless without comparative data. E.g. this method (yield X%) was better than that method (Y%); Of course, these extractions should have been performed on the identical algal sample. In addition, there is the continual problem of whether one extraction is producing the same kind of ulvan as the other extraction.

Response: As the reviewer suggested, we have created Figure 4 to conclude useful information on the advantages and disadvantages of different methods for the extraction of ulvan. Kindly go through it.

 

290 Is it 18 ± 2% or 18±2%? Make consistent throughout. 

Response: We have revised and maintained the consistency.

 

Figure 5 legend should explain/expand 'EAE etc.' fenestrat panel (b): replace 'reaction' with 'extraction'

Response: As suggested, we have made the changes.

 

419 A discussion of whether inducing plant defenses is useful and, if so, under what circumstances might be appropriate here. Inducible defences are beneficial to a plant in that they are activated when the plant is under threat. Defence responses are metabolically expensive, so inducible defences may be regarded as an evolutionary adaptation which does not waste resources when the plant is not under threat, improving the plants overall fitness. Artificially inducing these defences by application of ulvan may decrease plant production.

There seems to be a proliferation of acronyms in this section. Check whether they are all necessary (AzA?) and were identified that they are subsequently used in the text.

Response: We appreciate the reviewer’s thoughtful suggestion. We agree that a brief discussion on the utility and context of inducing plant defenses would add a valuable perspective. In the revised manuscript, we have included a paragraph acknowledging that inducible defenses are beneficial as adaptive, resource-efficient responses activated under threat, but that artificial induction by ulvan application may impose metabolic costs and potentially reduce plant productivity under non-stress conditions. This addition provides a balanced view of the ecological and agronomic implications of ulvan-mediated defense activation.

We have also reviewed all acronyms used in this section, ensuring that each is defined upon first mention and retained only if subsequently used (e.g., AzA has been evaluated for necessity). This revision improves clarity and readability while maintaining scientific precision.

 

Figure 6: I do not think this figure adds anything more to what may be conveyed through the text.

Response: The figure has been deleted in the revised manuscript

 

Table 5 Re concentrations (w/v)? What is the solvent? Any additives (detergent?)? 

Response: Water is the solvent, and no additives were mentioned.

 

647 There seems to be an introduction of a new mode of action in this section, viz.

enhanced production with very low ulvan concentrations rather than pathogen defences, which are elicited by much higher concentrations. Should be in a section separate from 'Formulations Strategies …'

Response: We have included a separate section on formulation strategies and have revised it in the manuscript.

 

699 LC50 (subscript)

Response: Corrected

 

References Formatting: generally better than most; however, re-check that plant names are italicised, ref. 136 seems to be incomplete; ref. 138 has formatting issues

Response: Reference formatting has been checked and corrected.

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

Reviewer Report

General Assessment

The manuscript provides a comprehensive review of ulvan, a sulfated polysaccharide derived from Ulva spp., and its potential applications in sustainable plant disease management. The topic is timely and highly relevant, considering the growing demand for eco-friendly alternatives to synthetic pesticides and the increasing interest in marine-derived biostimulants. The review is extensive and covers multiple aspects such as the chemical composition and structural motifs of ulvan, its biosynthesis pathways, extraction and purification techniques, physicochemical characterization, mechanisms of plant defense induction, direct antimicrobial effects, and applications against fungal, bacterial, and viral phytopathogens. Overall, the manuscript demonstrates significant effort and contains valuable compiled information. However, substantial revisions are required before it can be considered for publication, as the main concerns relate to language quality, conceptual clarity, mechanistic overinterpretation, structural organization, and scientific precision.

1. Language and Readability

The manuscript requires extensive English editing. Numerous grammatical errors, awkward constructions, inconsistent terminology, and repetition reduce clarity. Examples include:

• “Structured green seaweeds, Ulvales…” (Ulvales is an order, not “structured seaweeds”).
• “It is organic certified…” (unclear and grammatically incorrect).
• Frequent misuse of articles and plural forms.
• Repetitive and redundant phrasing throughout.

Professional language editing is strongly recommended.

2. Overstatement of Mechanistic Certainty

In Section 6, entitled Ulvan-Induced Mechanisms for Phytopathogen Inhibition, the manuscript presents highly detailed molecular pathways, including pattern recognition receptors such as CERK1 and WAKs, MAPK cascades, receptor-like cytoplasmic kinases such as BIK1 and PBL1, intracellular NLR receptors such as RPS2 and RPM1, PhoPQ regulatory systems, and specific quorum sensing molecules. While these pathways are well established in plant immunity research in general, it is not always clear whether the mechanisms described have been directly demonstrated for ulvan specifically or whether they are extrapolated from studies on other elicitors such as chitosan, laminarin, or other MAMPs. In several instances, the review presents these pathways as confirmed mechanisms of ulvan action, although the available evidence may be indirect or based on analogy.

To improve scientific rigor and accuracy, the manuscript should clearly distinguish between mechanisms that have been experimentally demonstrated for ulvan, mechanisms inferred from analogous elicitors, and hypothetical or proposed models. Where direct experimental evidence is lacking, qualifying language should be used to reflect the current level of certainty, for example by stating that a mechanism is “likely,” “suggested,” “proposed,” or “based on analogy to other elicitors.” Such clarification would strengthen the credibility of the review and prevent overinterpretation of existing data.

3. Critical Evaluation Is Limited

The review is largely descriptive and provides an extensive compilation of literature; however, it lacks deeper critical analysis. Although extraction yields are presented in detail across Tables 1–4, the manuscript does not include a meta-level discussion of variability, reproducibility, or the challenges associated with standardization across species and methodologies. In addition, there is no direct comparison between ulvan and other well-studied algal elicitors such as laminarin or carrageenan, which would help position ulvan within the broader context of marine-derived biostimulants. Field-level reproducibility, scalability, and long-term agronomic performance are not critically addressed, and while regulatory approval is mentioned, the discussion remains superficial and does not explore practical regulatory frameworks or approval pathways.

To strengthen the manuscript, the authors should consider adding a dedicated section that critically discusses the limitations of ulvan applications, variability related to species, season, and extraction method, challenges in standardization and quality control, economic feasibility and industrial scalability, and regulatory hurdles, particularly in EU and US contexts. Such a section would substantially improve the analytical depth and practical relevance of the review.

4. Structural Redundancy

The manuscript contains noticeable repetition across sections, particularly in the discussion of defense pathways such as PTI, ETI, SAR, and ISR, which are described in detail multiple times. Furthermore, the sections on direct antimicrobial effects and competitive inhibition of pathogen adhesion partly overlap conceptually, and the nutrient deprivation mechanism is presented separately although it could logically be integrated into the broader antimicrobial framework.

To improve clarity and coherence, Section 6 should be streamlined and reorganized into clearly structured subsections focusing on elicitor-mediated plant immunity, direct antimicrobial effects, surface interactions and biofilm inhibition, and nutrient chelation. Reducing redundancy and avoiding repeated explanations of general plant immunity concepts would enhance readability and maintain focus on ulvan-specific mechanisms.

5. Tables Are Informative but Overloaded

Tables 1–5 provide a large amount of useful data; however, some information lacks standardization and clarity. Certain entries are vague, such as “High (not specified)” in Table 4, and concentration units are not always consistently formatted. Additionally, some disease-agent associations should be carefully rechecked to ensure correct classification of fungal and bacterial pathogens. The presentation would benefit from clearer differentiation between in vitro, greenhouse, and field experiments.

The authors should verify all pathogen classifications, standardize concentration units and formatting, specify experimental conditions where possible, and consider summarizing rather than listing overly detailed species-level data when it does not add significant analytical value.

6. Biosynthesis Section Requires Caution

Section 3 describes ulvan biosynthesis with a high degree of mechanistic certainty, including epimerization processes, Golgi-localized sulfotransferases, and post-synthetic modifications in the apoplast. However, the biosynthetic pathways of ulvan in Ulva species are not yet fully elucidated, and some mechanistic details appear to be inferred from analogous systems rather than directly demonstrated.

The manuscript would benefit from clearly indicating which biosynthetic steps have been experimentally confirmed in Ulva and which are proposed based on comparisons with animal glycosaminoglycan pathways or other polysaccharide systems. Introducing appropriate qualifiers would improve scientific accuracy and prevent overinterpretation.

Minor Comments

The manuscript should ensure consistent spelling throughout, choosing either “sulfated” or “sulphated” and applying it uniformly. Formatting issues should be corrected, including spacing in chemical names, appropriate use of the ± symbol. Species names should be formatted consistently in italics, genus name capital letter, species name lowercase (not Ulva Lactuca), and figure captions should be expanded where necessary to improve methodological clarity. The addition of a schematic summary figure integrating extraction, structural features, mechanisms of action, and agricultural application would significantly enhance the conceptual flow of the review.

Strengths of the Manuscript

The manuscript demonstrates a comprehensive compilation of relevant literature and addresses a topic of clear agricultural and environmental importance. It successfully integrates chemical, biochemical, and plant pathological perspectives and combines mechanistic insights with applied agricultural examples. The inclusion of numerous figures and tables provides strong visual support and enhances the informational value of the review.

Recommendation

Major Revision

The manuscript has strong potential but requires substantial revision, including thorough language editing, reduction of redundancy, clearer separation between experimentally supported mechanisms and hypothetical models, deeper critical analysis of limitations and scalability, and structural refinement to improve clarity and coherence. With these improvements, the review could become a valuable and impactful contribution to the field of marine-derived biostimulants and sustainable agriculture.

 

 

Author Response

Reviewer 2:

General Assessment

The manuscript provides a comprehensive review of ulvan, a sulfated polysaccharide derived from Ulva spp., and its potential applications in sustainable plant disease management. The topic is timely and highly relevant, considering the growing demand for eco-friendly alternatives to synthetic pesticides and the increasing interest in marine-derived biostimulants. The review is extensive and covers multiple aspects such as the chemical composition and structural motifs of ulvan, its biosynthesis pathways, extraction and purification techniques, physicochemical characterization, mechanisms of plant defense induction, direct antimicrobial effects, and applications against fungal, bacterial, and viral phytopathogens. Overall, the manuscript demonstrates significant effort and contains valuable compiled information. However, substantial revisions are required before it can be considered for publication, as the main concerns relate to language quality, conceptual clarity, mechanistic overinterpretation, structural organization, and scientific precision.

1. Language and Readability

The manuscript requires extensive English editing. Numerous grammatical errors, awkward constructions, inconsistent terminology, and repetition reduce clarity. Examples include:

• “Structured green seaweeds, Ulvales…” (Ulvales is an order, not “structured seaweeds”).
• “It is organic certified…” (unclear and grammatically incorrect).
• Frequent misuse of articles and plural forms.
• Repetitive and redundant phrasing throughout.

Professional language editing is strongly recommended.

Response: Language editing has been done thoroughly.

 

1. Overstatement of Mechanistic Certainty

In Section 6, entitled Ulvan-Induced Mechanisms for Phytopathogen Inhibition, the manuscript presents highly detailed molecular pathways, including pattern recognition receptors such as CERK1 and WAKs, MAPK cascades, receptor-like cytoplasmic kinases such as BIK1 and PBL1, intracellular NLR receptors such as RPS2 and RPM1, PhoPQ regulatory systems, and specific quorum-sensing molecules. While these pathways are well established in plant immunity research in general, it is not always clear whether the mechanisms described have been directly demonstrated for ulvan specifically or whether they are extrapolated from studies on other elicitors such as chitosan, laminarin, or other MAMPs. In several instances, the review presents these pathways as confirmed mechanisms of ulvan action, although the available evidence may be indirect or based on analogy.

To improve scientific rigor and accuracy, the manuscript should clearly distinguish between mechanisms that have been experimentally demonstrated for ulvan, mechanisms inferred from analogous elicitors, and hypothetical or proposed models. Where direct experimental evidence is lacking, qualifying language should be used to reflect the current level of certainty, for example by stating that a mechanism is “likely,” “suggested,” “proposed,” or “based on analogy to other elicitors.” Such clarification would strengthen the credibility of the review and prevent overinterpretation of existing data.

Response: We thank the reviewer for this constructive suggestion regarding Section 6. We agree that the current version contains some repetition and overlapping conceptual explanations of plant defense pathways (PTI, ETI, SAR, ISR) and antimicrobial mechanisms.

In the revised manuscript, we have:

Streamlined Section 6 by reorganizing it into four clearly defined subsections:

1. Elicitor-mediated plant immunity (covering PTI, ETI, SAR, and ISR concisely)
2. Direct antimicrobial effects
3. Surface interactions and biofilm inhibition
4. Nutrient chelation and deprivation are integrated within the antimicrobial framework.
5. Effect of Ulvan on Phytopathogens  

 

1. Critical Evaluation Is Limited

The review is largely descriptive and provides an extensive compilation of literature; however, it lacks deeper critical analysis. Although extraction yields are presented in detail across Tables 1–4, the manuscript does not include a meta-level discussion of variability, reproducibility, or the challenges associated with standardization across species and methodologies. In addition, there is no direct comparison between ulvan and other well-studied algal elicitors such as laminarin or carrageenan, which would help position ulvan within the broader context of marine-derived biostimulants. Field-level reproducibility, scalability, and long-term agronomic performance are not critically addressed, and while regulatory approval is mentioned, the discussion remains superficial and does not explore practical regulatory frameworks or approval pathways.

To strengthen the manuscript, the authors should consider adding a dedicated section that critically discusses the limitations of ulvan applications, variability related to species, season, and extraction method, challenges in standardization and quality control, economic feasibility and industrial scalability, and regulatory hurdles, particularly in the EU and US contexts. Such a section would substantially improve the analytical depth and practical relevance of the review.

Response: As mentioned by the reviewer, we have added and elaborated on the challenges and limitations of the Ulvan application under 9 sections, including all the mentioned aspects in the revised manuscript. Similarly, we have added a refined, detailed table discussing ulvan and other well-studied algal elicitors, such as laminarin or carrageenan, comparing the different properties and multiple aspects of each of the following. 

 

1. Structural Redundancy

The manuscript contains noticeable repetition across sections, particularly in the discussion of defense pathways such as PTI, ETI, SAR, and ISR, which are described in detail multiple times. Furthermore, the sections on direct antimicrobial effects and competitive inhibition of pathogen adhesion partly overlap conceptually, and the nutrient deprivation mechanism is presented separately, although it could logically be integrated into the broader antimicrobial framework.

To improve clarity and coherence, Section 6 should be streamlined and reorganized into clearly structured subsections focusing on elicitor-mediated plant immunity, direct antimicrobial effects, surface interactions and biofilm inhibition, and nutrient chelation. Reducing redundancy and avoiding repeated explanations of general plant immunity concepts would enhance readability and maintain focus on ulvan-specific mechanisms.

Response: We thank the reviewer for this constructive suggestion regarding Section 6. We agree that the current version contains some repetition and overlapping conceptual explanations of plant defense pathways (PTI, ETI, SAR, ISR) and antimicrobial mechanisms.

In the revised manuscript, we have:

Streamlined Section 6 by reorganizing it into four clearly defined subsections:

1. Elicitor-mediated plant immunity (covering PTI, ETI, SAR, and ISR concisely)
2. Direct antimicrobial effects
3. Surface interactions and biofilm inhibition
4. Nutrient chelation and deprivation are integrated within the antimicrobial framework.
5. Effect of Ulvan on Phytopathogens 

 

1. Tables Are Informative but Overloaded

Tables 1–5 provide a large amount of useful data; however, some information lacks standardization and clarity. Certain entries are vague, such as “High (not specified)” in Table 4, and concentration units are not always consistently formatted. Additionally, some disease-agent associations should be carefully rechecked to ensure correct classification of fungal and bacterial pathogens. The presentation would benefit from clearer differentiation between in vitro, greenhouse, and field experiments.

The authors should verify all pathogen classifications, standardize concentration units and formatting, specify experimental conditions where possible, and consider summarizing rather than listing overly detailed species-level data when it does not add significant analytical value.

Response: As suggested, we have revised all the tables as per the instructions.

 

1. Biosynthesis Section Requires Caution

Section 3 describes ulvan biosynthesis with a high degree of mechanistic certainty, including epimerization processes, Golgi-localized sulfotransferases, and post-synthetic modifications in the apoplast. However, the biosynthetic pathways of ulvan in Ulva species are not yet fully elucidated, and some mechanistic details appear to be inferred from analogous systems rather than directly demonstrated.

The manuscript would benefit from clearly indicating which biosynthetic steps have been experimentally confirmed in Ulva and which are proposed based on comparisons with animal glycosaminoglycan pathways or other polysaccharide systems. Introducing appropriate qualifiers would improve scientific accuracy and prevent overinterpretation.

 

Response: We appreciate the reviewer’s insightful observation regarding Section 3 and agree that distinguishing experimentally confirmed steps from those inferred by analogy will strengthen the manuscript’s scientific rigor. The current description of ulvan biosynthesis indeed integrates both direct evidence from Ulva studies and mechanistic parallels drawn from glycosaminoglycan and other polysaccharide systems.

In the revised version, we have:

• Clarified experimental evidence
• Added qualifiers such as “putatively,” “presumed,” or “based on analogy with animal glycosaminoglycan pathways” where mechanisms remain hypothetical.
• Revised the section introduction to acknowledge that the ulvan biosynthetic pathway 

 

Minor Comments

The manuscript should ensure consistent spelling throughout, choosing either “sulfated” or “sulphated” and applying it uniformly. Formatting issues should be corrected, including spacing in chemical names, appropriate use of the ± symbol. Species names should be formatted consistently in italics, genus name capital letter, species name lowercase (not Ulva Lactuca), and figure captions should be expanded where necessary to improve methodological clarity. The addition of a schematic summary figure integrating extraction, structural features, mechanisms of action, and agricultural application would significantly enhance the conceptual flow of the review.

Response: In the revised manuscript, we have corrected all the minor mistakes and tried to compile a structural in-depth, collective information about ulvan. 

 

Strengths of the Manuscript

The manuscript demonstrates a comprehensive compilation of relevant literature and addresses a topic of clear agricultural and environmental importance. It successfully integrates chemical, biochemical, and plant pathological perspectives and combines mechanistic insights with applied agricultural examples. The inclusion of numerous figures and tables provides strong visual support and enhances the informational value of the review.

Response: We would like to thank the reviewer for acknowledging the significance of the topic and marking out the strengths so impactfully.

Reviewer 3 Report

Comments and Suggestions for Authors

Dear authors,

The topic chosen for this review is of significant importance to studies seeking marine-based alternatives for agricultural production, with a focus on reducing environmental impact. I have only a few comments and suggestions regarding the manuscript.

ABSTRACT: Ok

INTRODUCTION: The passage between lines 57 and 64 provides quite specific information. I suggest that at least one citation be inserted.

TABLES: Ok

FIGURES: Ok

CONCLUSION: I think this section should be more concise.

Author Response

Reviewer 3:

INTRODUCTION: The passage between lines 57 and 64 provides quite specific information. I suggest that at least one citation be inserted.

Response: As suggested by the reviewer, we have included the supporting references mentioned below in the specific paragraph.

• Badilli, U., & Inal, O. (2025). Current approaches in cosmeceuticals: Peptides, biotics and marine biopolymers. Polymers, 17(6), 798.
• Pari, R. F., Uju, U., Hardiningtyas, S. D., Ramadhan, W., Wakabayashi, R., Goto, M., & Kamiya, N. (2025). Ulva seaweed-derived Ulvan: A promising marine polysaccharide as a sustainable resource for biomaterial design. Marine Drugs, 23(2), 56.
• Joshi, D., Oza, D. H., & Vyas, P. (2026). Unlocking the Potential of Algal Polysaccharides: Nature’s Versatile Biopolymers. In Algae and Algal Metabolites: Emerging Applications, Trends and Prospects (pp. 1-36). Cham: Springer Nature Switzerland.

 

TABLES: Ok

Response: Thank you for your confirmation.

 

FIGURES: Ok

Response: Thank you for your confirmation.

 

CONCLUSION: I think this section should be more concise.

Response: As suggested by the reviewer conclusion has been revised. 

Round 2

Reviewer 2 Report

Comments and Suggestions for Authors

The revised manuscript is substantially improved compared with the original version and addresses many of the reviewer’s concerns in a meaningful and visible way.

Language quality and readability have improved considerably throughout the manuscript. Numerous awkward expressions, grammatical inconsistencies, and unclear formulations present in the original submission have been corrected. The revised text is clearer, more coherent, and more professional in tone, which significantly improves readability.

The introduction has been extensively rewritten and now provides a stronger scientific context for sustainable agriculture, current limitations of conventional plant protection strategies, and the relevance of marine macroalgae as alternative resources. Definitions and transitions are clearer, and the rationale of the review is better justified.

The overall structure of the manuscript is better organized. Several sections have been rearranged or refined, making the manuscript easier to follow. The logical flow between background information, physicochemical properties, mechanisms of action, applications, and future perspectives is stronger than in the previous version.

A major improvement is the addition of a dedicated section discussing current challenges and limitations of ulvan application. This substantially increases the analytical and practical value of the review. Important aspects such as variability related to species, season, and extraction methods, challenges in standardization and quality control, economic feasibility, industrial scalability, and regulatory hurdles in the EU and US contexts are now explicitly addressed.

The manuscript also better positions ulvan within the broader context of sustainable agriculture and marine biostimulants. The expanded discussion of practical implementation, market relevance, and future development pathways strengthens the real-world significance of the review.

Section 6 has been improved through clearer subdivision of mechanisms into more distinct thematic parts, including plant immune activation, direct antimicrobial effects, and pathogen adhesion related processes. This reduces some of the redundancy present in the earlier version and improves readability.

The biosynthesis section has been revised with the inclusion of more cautious wording in several places. Terms such as likely, believed, and may help distinguish partially supported mechanisms from fully demonstrated pathways, which improves scientific balance.

Figures and visual presentation appear more polished and informative. The manuscript overall has a more complete and publishable presentation than the original submission.

However, some mechanistic statements remain too definitive and should still be moderated further by clearly distinguishing experimentally demonstrated effects from hypotheses, proposed models, or analogies with other elicitors. This is particularly relevant in the discussion of signaling pathways and direct antimicrobial mechanisms.

Some sections could still be slightly shortened or streamlined to reduce repetition and maintain stronger focus on ulvan-specific evidence rather than broader general concepts.

Overall, the revised version represents a clear and substantial improvement over the original submission and is now much closer to publication standard.

After minor suggested and largely optional revisions focused on scientific precision and wording, the manuscript may be considered suitable for publication without the need for further rounds of external review.

Author Response

Reviewer 2

Comments:

The revised manuscript is substantially improved compared with the original version and addresses many of the reviewer’s concerns in a meaningful and visible way.

Language quality and readability have improved considerably throughout the manuscript. Numerous awkward expressions, grammatical inconsistencies, and unclear formulations present in the original submission have been corrected. The revised text is clearer, more coherent, and more professional in tone, which significantly improves readability.

The introduction has been extensively rewritten and now provides a stronger scientific context for sustainable agriculture, current limitations of conventional plant protection strategies, and the relevance of marine macroalgae as alternative resources. Definitions and transitions are clearer, and the rationale of the review is better justified. 

The overall structure of the manuscript is better organized. Several sections have been rearranged or refined, making the manuscript easier to follow. The logical flow between background information, physicochemical properties, mechanisms of action, applications, and future perspectives is stronger than in the previous version.

A major improvement is the addition of a dedicated section discussing current challenges and limitations of ulvan application. This substantially increases the analytical and practical value of the review. Important aspects such as variability related to species, season, and extraction methods, challenges in standardization and quality control, economic feasibility, industrial scalability, and regulatory hurdles in the EU and US contexts are now explicitly addressed. 

The manuscript also better positions ulvan within the broader context of sustainable agriculture and marine bio-stimulants. The expanded discussion of practical implementation, market relevance, and future development pathways strengthens the real-world significance of the review.

Section 6 has been improved through clearer subdivision of mechanisms into more distinct thematic parts, including plant immune activation, direct antimicrobial effects, and pathogen adhesion related processes. This reduces some of the redundancy present in the earlier version and improves readability. 

The biosynthesis section has been revised with the inclusion of more cautious wording in several places. Terms such as likely, believed, and may help distinguish partially supported mechanisms from fully demonstrated pathways, which improves scientific balance. 

Figures and visual presentation appear more polished and informative. The manuscript overall has a more complete and publishable presentation than the original submission.

However, some mechanistic statements remain too definitive and should still be moderated further by clearly distinguishing experimentally demonstrated effects from hypotheses, proposed models, or analogies with other elicitors. This is particularly relevant in the discussion of signalling pathways and direct antimicrobial mechanisms. 

Some sections could still be slightly shortened or streamlined to reduce repetition and maintain a stronger focus on ulvan-specific evidence rather than broader general concepts.

Overall, the revised version represents a clear and substantial improvement over the original submission and is now much closer to publication standard. 

After minor suggested and largely optional revisions focused on scientific precision and wording, the manuscript may be considered suitable for publication without the need for further rounds of external review.

 

Response to Reviewer: 

We are thankful and express our sincere gratitude to the reviewer for thoroughly reviewing our revised version of the manuscript and for the constructive, encouraging, and motivating comments. We sincerely appreciate and are thankful to the reviewer for acknowledging the improvement in language, structure, and other aspects of the revised manuscript. We are especially appreciative of the identification of the revised introduction and inclusion of the section on challenges in the use of ulvan.

We sincerely appreciate your valuable suggestions for minor corrections to improve the quality of our manuscript. To address your concerns, we made the required minor changes to make the manuscript scientifically precise and clear. The specific changes are as follows:

1. Moderation of mechanistic statements:

Mechanisms of action were reviewed in detail, particularly the discussion of signalling pathways and antimicrobial activity, to ensure that experimentally validated observations were not mixed with proposed or hypothetical mechanisms. Terms such as “may,” “likely,” “is proposed to,” and “has been suggested” have been used where necessary.

2. Reduced redundancy and enhanced conciseness

Some parts of the manuscript have been slightly corrected and trimmed down to minimize redundancy and ensure continued emphasis on evidence specific to ulvan.

3. Minor linguistic and clarity improvements:

Several minor modifications have been made across the revised manuscript to enhance readability and consistency.

4. Enhanced scientific balance:

Overly definitive statements, which lacked strong experimental evidence, have been corrected. Analogies between ulvan and other polysaccharide elicitors have been explicitly stated where relevant.

With these corrections, we believe that we have addressed all of your remaining concerns and have further improved the clarity, balance, and overall quality of our revised manuscript. Once again, we would like to express our sincere gratitude for your valuable comments, which have enabled us to further enhance the quality and scientific clarity of our manuscript.