Root Growth and Architecture of Wheat and Brachypodium Vary in Response to Algal Fertilizer in Soil and Solution

Round 1

Reviewer 1 Report

Dear Authors, 

I have reviewed the manuscript “Root growth and architecture of wheat and Brachypodium vary in response to algal fertilizer in soil and solution’. It is well written, the research is novel and interesting. Furthermore, the statistics used is correct. However, there are some points/quarries which needs to be properly addressed as follows:

1. The title “Root growth and architecture of wheat and Brachypodium vary in response to algal fertilizer in soil and solution” shall be improved as Root growth and architecture of wheat and Brachypodium vary in response to algal fertilizer in different cultivation medium” in order to further broaden the scope of the study.
2. Line 13-17 in the abstract shall be briefed and rephrased.
3. Line 17-19 shall be rephrased as “ we tested the phenotypic responses of wheat (Triticum aestivum) and its genetic model, Brachypodium (Brachypodium distachyon) to dried algal biomass (with algae, high,  low mineral P)  under  three growing conditions [fabricated ecosystems (Eco- 19 FABs); hydroponics; and sand].
4. Line 24; it would be better to show (Root hairs were shorter in Brachypodium, but longer in wheat with 24 algae compared to mineral P) in term of % .
5. Line 54; [12] [13] [14] [15] shall be amended as [12-15] and adopt the same across the manuscript.
6. Algae is a viable source of plant nutrients [16] [17]. Could you please report its quantitative nutrient concentration from the literature?
7. Line 67; (FAOstat 2019) shall be formatted as other references according to the journal requirement.
8. Add the novelty statement and research gape to the last paragraph of the introduction section.
9. What was the nutritional composition of algae?
10. How did you compensate the other nutrients obtained from algae in the remaining two treatments (high and Low mineral P).
11. What was the source of P from high and low mineral P?
12. What were your hypotheses while choosing three types of cultivation medium?
13.   Table 2 is confusing.  I suggest simplifying it. You presented your data in two ways tables while stating that your experiment is One-way-ANOVA why?
14. In fig 4. I see that the performance of low and high P is mostly at par while algae is performing inferior to those. Why?
15. The overall discussion part needs improvement.
16. In abstract line 21 you stated that “algae treated plants are taking up more P than the low mineral P plants” while in line 502 it is taking up a higher amount per root length than mineral P. your mineral P is two levels “ high and low”. Now what is needed to know is which of your statements is correct? Another thing is that, that you didn’t find the uptake; your table shows only concentration data. Then how can you say that the uptake was high? What I know is, uptake is the product of biomass and concentration. If yes, then I would suggest doing the needful corrections.

Author Response

1. The title “Root growth and architecture of wheat and Brachypodium vary in response to algal fertilizer in soil and solution” shall be improved as Root growth and architecture of wheat and Brachypodium vary in response to algal fertilizer in different cultivation medium” in order to further broaden the scope of the study.

A: Thank you for this comment. We do, however, prefer the previous version of the title. The nutritional medium used in all our three different experimental setups was exactly the same, therefore using “different cultivation medium” in the title would be confusing from our point of view.

1. Line 13-17 in the abstract shall be briefed and rephrased.

A: We have shortened and rephrased these lines.

1. Line 17-19 shall be rephrased as “ we tested the phenotypic responses of wheat (Triticum aestivum) and its genetic model, Brachypodium (Brachypodium distachyon) to dried algal biomass (with algae, high,  low mineral P)  under  three growing conditions [fabricated ecosystems (Eco- 19 FABs); hydroponics; and sand].

A: Thank you for commenting on this aspect. We have rephrased these lines in the abstract.

1. Line 24; it would be better to show (Root hairs were shorter in Brachypodium, but longer in wheat with 24 algae compared to mineral P) in term of % .

A: We have added the % differences to the abstract.

1. Line 54; [12] [13] [14] [15] shall be amended as [12-15] and adopt the same across the manuscript.

A: Thank you very much, we have edited the reference manager accordingly.

1. Algae is a viable source of plant nutrients [16] [17]. Could you please report its quantitative nutrient concentration from the literature?

A: The composition of algal biomass is highly dependent on their overall growth conditions. P content can vary between 2-5% in dry weight. The algal biomass used in this study was commercially produced and tested for elemental composition before experimental start; summarized in Figure 1B and Supplemental Table1 as is indicated on lines 120-122 in the manuscript.

1. Line 67; (FAOstat 2019) shall be formatted as other references according to the journal requirement.

A: Thank you very much, we have edited the reference manager accordingly.

1. Add the novelty statement and research gape to the last paragraph of the introduction section.

A:Thank you very much, we have edited the specific section accordingly. 

1. What was the nutritional composition of algae?

A: The algal biomass used in this study was commercially produced and tested for elemental composition before experimental start; it contained 0.5 mM P, 6.3 mM N, 0.57 mM K, 0.12 mM Mg, 0.20 mM S, 0.04 mM Fe, 0.11 mM Ca and was substituted with mineral N,K,Mg,S,Fe,Ca to reach Hoagland level for all nutrients (summarized in Figure 1B and Supplemental Table1), as indicated in lines 120-122 in the manuscript.

1. How did you compensate the other nutrients obtained from algae in the remaining two treatments (high and Low mineral P).

A: Nutritional components of algae were compensated based on their elemental composition and matched to the nutrient contents of the mineral media composition. Highest elemental component in algal biomass (compared to the elemental composition of Hoagland) was P, all other elements were present in lower concentrations, therefore only the algal treatment required additional supplementation. The total composition is shown in Suppl. Table 1, as referenced in line 120 of the manuscript. 

1. What was the source of P from high and low mineral P?

A: The mineral media composition was based on Hoagland medium. Therefore the P source was NH4H2PO4 (see Suppl. Table 1).

1. What were your hypotheses while choosing three types of cultivation medium?

A: Algal biomass as source of P fertilizer replacement- both, as they can store a high amount of P as well as the limited nature of rock phosphate as P source of conventional P fertilizers. The high and low  P amount is based on previously reported evidence see e.g. Nestler et al. 2016.

1.   Table 2 is confusing.  I suggest simplifying it. You presented your data in two ways tables while stating that your experiment is One-way-ANOVA why?

A: Tables 1 and 2 have the same structure, separating tissues per treatment and illustrating those differences in the 3 different experimental setups used. We have optimized this separation.

1. In fig 4. I see that the performance of low and high P is mostly at par while algae is performing inferior to those. Why?

A: The overall amount of nutrients is the same, according to their elemental composition, but the availability of these nutrients is likely to differ, because in algal biomass they are mostly incorporated in larger molecules and not presented as the mineral form that is provided in the liquid nutrient media we used in our experiments. We have improved the discussion to cover this aspekt better, see lines 484-494, as well as results around (figure poly-P and sequential P fractionation).

1. The overall discussion part needs improvement.

A: Thank you for this comment, we have improved the overall discussion.

1. In abstract line 21 you stated that “algae treated plants are taking up more P than the low mineral P plants” while in line 502 it is taking up a higher amount per root length than mineral P. your mineral P is two levels “ high and low”. Now what is needed to know is which of your statements is correct? Another thing is that, that you didn’t find the uptake; your table shows only concentration data. Then how can you say that the uptake was high? What I know is, uptake is the product of biomass and concentration. If yes, then I would suggest doing the needful corrections.

A: Thank you for that comment. The total P amount taken up and the amount taken up per root length do not necessarily have to have the same trend, since the root length of the treatments differed greatly. Table 1 and 2 display both the concentration, as well as the total amount of P that was taken up (weight*concentration); we changed the naming of that parameter to make it clearer. 

Reviewer 2 Report

Title: Root growth and architecture of wheat and Brachypodium vary in response to algal fertilizer in soil and solution

By

Mau et al.

General Comments

The manuscript is well written and based on original data. The subject is clearly of interest for the Journal. The authors presented the core of the study in a coherent manner. However, I recommend authors check their style of scholarly writing. The tone of scholarly writing is strictly formal and as such sentences should be more precise and straightforward. References were appropriately cited and listed.

Concerns/suggestions

1. Spell out all abbreviations on their first use
2. For all plants/organisms, include the common names in addition to the scientific name; either one in parenthesis.
3. The background and rationale for the study in the introduction section is too generic and loses the uniqueness of the study. State categorically the justification(s) for this particular study to clearly bring out the novelty of this study.
4. There is a disconnect between the hypothesis and the objectives? How can the study answer the hypothesis being tested?
5. Clearly describe the treatments in the materials and methods sectons for readers to clearly follow the results and discussions better.
6. The discussion was rather less thorough with less emphasis on the implications of the core findings In general, I think the discussion could be improved by further analysis of the potential mechanisms causing the observed results. In general, I think the discussion could be improved by further analysis of the potential mechanisms causing the observed results. The paper has to have a strong mechanistic basis: it cannot merely show WHICH practice had the greater effects but WHY.
7. Table 1. Use letters to indicate differences among treatments
8. The conclusions of the study must be written to clearly indicate the “take-home” message from the study. Authors must highlight the implications of the core findings.

Specific comments and suggestions:

Specific comments and suggestions are provided directly on the pdf file of the manuscript.

Comments for author File: Comments.pdf

Author Response

Concerns/suggestions

1. Spell out all abbreviations on their first use

A: Thank you for this comment. We have edited the manuscript text accordingly.

1. For all plants/organisms, include the common names in addition to the scientific name; either one in parenthesis.

A: The introduction now contains both common and scientific names for wheat and Brachypodium.

1. The background and rationale for the study in the introduction section is too generic and loses the uniqueness of the study. State categorically the justification(s) for this particular study to clearly bring out the novelty of this study.

A: Thank you for this comment. We have edited the last, specific paragraph at the end of the introduction to make the rationale clearer.

1. There is a disconnect between the hypothesis and the objectives? How can the study answer the hypothesis being tested?

A: We have optimized the last paragraph in the introduction to make the connection between our objectives and the hypotheses being tested clearer.

1. Clearly describe the treatments in the materials and methods sectons for readers to clearly follow the results and discussions better.

A: We have edited the materials and methods section for easier reading; the information is also summarized in Figure 1 and Supplemental Table1.

1. The discussion was rather less thorough with less emphasis on the implications of the core findings In general, I think the discussion could be improved by further analysis of the potential mechanisms causing the observed results. In general, I think the discussion could be improved by further analysis of the potential mechanisms causing the observed results. The paper has to have a strong mechanistic basis: it cannot merely show WHICH practice had the greater effects but WHY.

A: Thank you for this comment. We have improved the discussion part and included more speculation about the observed effects, we also include an outlook describing what is needed for better mechanistic understanding of the plant response.

1. Table 1. Use letters to indicate differences among treatments

A: Table 1, the N and P measurements of brachypodium tissue, can unfortunately not contain letters to show significant differences. The material amounts needed for the analyses required pooling of tissue among replicates (so n=1), as described in lines 206-208. We include a clarification in the Table description.

1. The conclusions of the study must be written to clearly indicate the “take-home” message from the study. Authors must highlight the implications of the core findings.

A: Thank you for this comment, we have improved the concluding paragraph of this manuscript highlighting implications of our findings.

Specific comments and suggestions:

Specific comments and suggestions are provided directly on the pdf file of the manuscript.

A: Thank you for the specific comments and suggestions in the pdf file. We have edited these points in the word document and marked all. Differences in P content in our experimental systems are due to the different volumes used while using the same concentrations.