Influence of Drought Stress on Growth and Essential Oil Yield of Ocimum Species

Round 1

Reviewer 1 Report

Introduction

- even if the purpose of the research is mentioned in the Discussions section, I recommend that it be presented in the Introduction, along with the Objectives that the authors mentioned

Material and methods

- the materials and methods used in the research are presented in detail and clearly

- research or focused on a large number of observations: Relative water content, Chlorophyll content, Plant growth measurement, Glandular hair density (original and interesting method of determining glandular hair density - Radácsi et al., Essential oil content determination, Total polyphenol content, Antioxidant capacity, Essential oil composition

Results and discussions

- the results obtained and presented in the 11 tables are quite complex and relevant to build the proposed objectives

- the discussions are well punctuated and amply presented

References are properly chosen, contain recent publications and are correctly cited

Author Response

Dear Reviewer 

Thank you very much for your constructive feedback and suggestions. I have amended the manuscript based on the comments given. I have included a few points in the introduction. The material and methods and references are also further improved. I have attached the corrected version for your reference. 

I look forward to your comments and concerns if any. 

Sincerely,

Sintayehu Musie

Author Response File: Author Response.docx

Reviewer 2 Report

The paper reports the effect of drought stress on growth and secondary metabolites (polyphenols and essential oil) accumulation of Ocimum species (O. basilicum, O. africanum and O. americanum). The work is well-designed and the experiments have been carried out properly.However, in some cases I made some corrections and suggestions.

L117: 40 µL

L128: TPTZ (2,4,6-tripyridyl-s-triazine)

L130: 10 µL

Table 9: camphene, limonene, germacrene D

- plant species written in italics throughout the text

Author Response

Dear reviewer

Thank you very much for your constructive feedback. I have amended the manuscript based on your suggestions and comments made by others. I have attached the corrected version for your reference. 

with regards,

Sintayehu Musie

Author Response File: Author Response.docx

Reviewer 3 Report

In this study, the authors described the effects of different drought stress on the growth, accumulation of secondary metabolites, and antioxidant capacity of three Ocimum species in pot experiment. The results provide important information for the artificial cultivation of Ocimum plant, especially on the plant species choice and important cultivation condition. However, in my opinion, there are few issues needing improvement.

1. Seedlings picture after plantation should be given, and the plant number in the pot experiment should be given.
2. How the SWC was created and maintained in the whole treatment time should be described in more details.
3. In the pot experiment, I was wondering that, with different location, plants in the center of the bush will be exposed under different sunlight condition compared with plants in outer layer, which will complicate the sampling of the plant leaves.
4. In the analysis of TPC and antioxidant activity, since there is no compound identification, the main compounds reported responsible for the anti-oxidant activity should be reviewed in the introduction part, and discussed.
5. I don’t understand why only two replicates were used in the experimental design. In the data listed, there are no errors at all, which will cover the differences between samples and groups.

Author Response

Dear reviewer

Thank you very much for your constructive comments and suggestions. I have amended the manuscripts based on your comments. Additional points are indicated with track change on the manuscript for your further references. I have attached the corrected manuscript with this letter. 

Point 1. I have included a picture that shows the overall setup and growth of the plants. I have also amended the number of plants per pot.

Point 2. Based on your suggestions, I highlighted how the moisture content was maintained during the experiment.

Point 3. You are right there could be a shading effect as a result of the radiation angle of the sun. That is why we used the RCBD design in the greenhouse. Plants were arranged randomly in each block. As it is shown in the first photo in the manuscript, there were a manageable number of plants.

Point 4. Sure, I have included a couple of paragraphs about antioxidant activities and polyphenol content. If you are not convinced let me know.

Point 5. Based on our previous experiences, we reduced the number of replications and plants per treatment. Regular moisture maintenance was very time-consuming and not easily manageable. On top of that resources were limited too. Initially, we included mean ± SD but the table was way bigger and it cannot fit the page layout. Then we rearranged the table to include more data.

I look forward to your constructive suggestions. 

Sincerely, 

SIntayehu Musie

Author Response File: Author Response.docx

Reviewer 4 Report

Manuscript Number: horticulturae-1589827, titled:

Influence of drought stress on growth and essential oil yield of Ocimum species

Review 1 – 29 January 2022

Dear Editor of Horticulturae

the argument is interesting but has to be improved. The manuscript has to be arranged as suggested by Horticulturae. The introduction section has to be better argued and the bibliography has to be extended. The M&M section has to be completed. Inaccuracies in the text and mainly in the references section.

I suggest a major revision

To the Authors (in detail):

1. Introduction section, lines 37-38. You have stated that essential oil production is influenced by various environmental factors, but you have not supported this statement with pertinent references. In addition, the essential oil composition is not only influenced by environmental factors. You have to explain that the essential oil composition of a part of a plant is influenced by many factors such as: geographical area of cultivation [X1]; cultivation condition [X2]; harvest year [X3], harvest date [X4], variety or cultivar if it is a cultivated plant [X5], age of plant or parts of plant [X6], essential oil extraction system [X7],  ..and so on. Support this statement, at least, with the following references. Insert each reference after each influencing factor (point by point) and do not cumulate all references at the end of the sentence. After this you can focus on drought stress.

[X1] Variability in essential oil composition, antioxidant and antimicrobial activities of Ruta montana L. collected from different geographical regions in Algeria.

Journal of Essential Oil Research Volume 32, 2020 - Issue 1. https://doi.org/10.1080/10412905.2019.1660238

[X2] Chemical components of essential oils and biological activities of the aqueous extract of Anethum graveolens L. grown under inorganic and organic conditions.

Chem. Biol. Technol. Agric. (2021) 8:20 https://doi.org/10.1186/s40538-021-00224-9

[X3] The peel essential oil composition of bergamot fruit (Citrus bergamia, Risso) of Reggio Calabria  (Italy): a review.

Emirates Journal of Food and Agriculture  32 (11) 835-845 (2020)

[X4] Variations of Essential Oil Constituents in Oregano (Origanum vulgare subsp. viridulum (= O. heracleoticum) over Cultivation Cycles.

Plants 2020, 9, 1174; doi:10.3390/plants9091174

[X5] Citrus bergamia, Risso: the peel, the juice and the seed oil of the bergamot fruit of Reggio Calabria (South Italy).

Emirates Journal of Food and Agriculture 32(7) 522-532 (2020).

DOI: 10.9755/ejfa.2020.v32.i7.2128

[X6] Plant Shoot Age and Temperature Effects on Essential Oil Yield and Oil Composition of Rose-Scented Geranium (Pelargonium sp.) Grown in South Africa.

Journal of Essential Oil Research Volume 18, 2006 - Issue sup1.

 https://doi.org/10.1080/10412905.2006.12067129

[X7] A study on the extraction of essential oil of Persian black cumin using static supercritical CO2 extraction, and comparison with hydro-distillation extraction method.

Separation Science, 10.1080/01496395.2018.1541907Technology (Philadelphia)Volume 54, Issue 11, Pages 1778 - 178624 July 2019

1. Caption of table 1: why have you written here Soroksar?
2. 2.2 section, the information about the type of soil used is missed;
3. 2.3 section: specify from how many plant you have picked leaves;
4. Essential oil content determination. Please, describe the applied method because for an International reader it is not easy to find the reference [22] you have included. Describe: type of solvent; ratio leaves solvent; temperature of extraction; extraction duration; the container used to store the essential oil; the temperature of storage; how long between EO extraction and analyses;
5. TPC content section: how have you filetered the EO?
6. TPC content section: why have you included only here some extraction condition? These condition are proper for this analysis or not?
7. TPC content section and in the whole manuscript, tables, sometime ml and sometime mL, please, be consistent. I suggest mL for consistency;
8. Line 138, delete one space before … initial;
9. Lines 129 and 141 and in the whole manuscript, when you have indicated the quantities, sometime you have used the fraction and sometime the exponent. Please, be consistent in the whole manuscript;
10. Captions of table 3-4-5-6-7-8-9: why have you written here Budapest 2020?
11. Lines 203-204 and in the whole manuscript: the botanical names in italics;
12. Lines 156 and 207 and in the whole manuscript: when you indicate the significance, verify the spacing between letter, symbol and numeric value for consistency;
13. Lines 156 and 207 and in the whole manuscript: when you indicate the significance, verify if p or P, if italicized or not. Please, be consistent;
14. Table  9, sometime you have written the name of each compound in capital letter and sometime in small letter. Please, be consistent here and in the whole manuscript;
15. Table 9, β-pinene. The symbol you have used for β (beta), is wrong. You have used probably a symbol of the actual German alphabet, whereas you have to use the correct symbol of the ancient Greek alphabet. Please make the same in this table and in the whole manuscript;
16. Table 9. Please, insert a different symbol for each class of compounds to recognize each single component with the total content of proper class of component and use the same symbol in the total of each class of compounds……Monoterpenes and so on…;
17. Table 9: Limonen or Limonene?, Please, verify;
18. Table 9, the one-way Anova analysis is missed. Please, do it and discuss your data also in light of the statistical results;
19. Line 269-270 and in the whole manuscript. Sometime you have written the word… specie in italics and sometime non. Please, be consistent and apply the International rules and the guidelines of Horticulturae. Use some recently published paper as a template;
20. References section. This section has to be arranged as required by Hortuculturae. For example: the publication year in bold; a comma after the volume number, and so on….;
21. References section and in the whole manuscript: when you write a botanical name, the botanist has not to be italicized (ref 7);
22. References section: sometime you have written the title of a paper in capital letter (ref 10) and sometime non. Please, be consistent with the guidelines and use a recently published papera s a template;
23. References section, the symbol & is not required before the last author, in the guidelines, please, re-arrange
24.  Please, write in blue color or evidence differently the corrections you will do

I suggest a major revision

Regards.

Author Response

Dear Reviewer

Honestly, thank you very much for your detailed constructive comments and suggestions. I’m sorry for taking much of your time in some of the inconsistencies, reference-related problems, and standards. I should have rechecked it several times in advance.

Based on your suggestions I have amended the manuscript. The additional points are indicated with track change in the manuscript attached here for your reference.

Point 1. I have included additional factors influencing essential oil production and composition (cultivation, harvesting, processing, and storages conditions).

Point 2 and 11. Soroksar is the name of the experimental field. It’s redundant so I have removed Soroksar as well as Budapest (2020) from the tables.

Point 3 and 4. We used sandy loam soil and peat moss mixture. The chemical property of the soil media is indicated in table 1.  

Point 4. The number of plants used for leave picking is indicated for both destructive samples (Relative water content and Leaf area)

Point 5 and 6. Detail is given on essential oil extraction and storage. Also, the description of filter paper used for extract filtration.

Point 7. TPC is determined based on the standard mentioned by Folin–Ciocalteu method. Based on department experience a sight modification on the concentration of the extract was used. But the standard reaction, chemicals used, the time of reaction, and absorbance reading were based on the standard protocol.  

The other points are about inconsistency in SI unit, botanical names (italics), standard symbols, mixed-use of capital vs small letters, and reference writing problems. I have corrected all of this and indicated it in the manuscript. For reference writing, I strictly followed the journal style and recently published templates.

One last thing, I have not fully understood this comment ‘Table 9. Please, insert a different symbol for each class of compounds to recognize each single component with the total content of proper class of component and use the same symbol in the total of each class of compounds……Monoterpenes and so on…;’

I look forward to your feedback and suggestion. Once again Thank you

Sincerely, 

Sintayehu Musie

Author Response File: Author Response.docx

Round 2

Reviewer 4 Report

Manuscript Number: horticulturae-1589827, titled:

Influence of drought stress on growth and essential oil yield of Ocimum species

Review 2 – 8 February 2022

Dear Editor of Horticulturae

the argument is interesting. The Authors have included the large part pf my comment. However, some improvement is necessary.

I suggest a major revision

To the Authors (in detail):

1. In the introduction section please include also the references I have listed, in relation with the effect of various factors influencing the essential oil production. It is important to evidence that these factors influence not only the Ocimum genus but also the EO of all plants. Explain that the essential oil composition of a part of a plant is influenced by many factors such as: geographical area of cultivation [X1]; cultivation condition [X2]; harvest year [X3], harvest date [X4], variety or cultivar if it is a cultivated plant [X5], age of plant or parts of plant [X6], essential oil extraction system [X7],  ..and so on. Support this statement, at least, with the following references. Insert each reference after each influencing factor (point by point) and do not cumulate all references at the end of the sentence. After this you can focus on drought stress.

[X1] Variability in essential oil composition, antioxidant and antimicrobial activities of Ruta montana L. collected from different geographical regions in Algeria.

Journal of Essential Oil Research Volume 32, 2020 - Issue 1, Pages 88-101. https://doi.org/10.1080/10412905.2019.1660238

[X2] Chemical components of essential oils and biological activities of the aqueous extract of Anethum graveolens L. grown under inorganic and organic conditions.

Chemical and Biological Technologies in Agriculture volume 8, Article number: 20 (2021)

https://doi.org/10.1186/s40538-021-00224-9

[X3] The peel essential oil composition of bergamot fruit (Citrus bergamia, Risso) of Reggio Calabria  (Italy): a review.

            Emirates Journal of Food and Agriculture, Vol. 32, no. 11, Nov. 2020, pp. 835-4,

            DOI https://doi.org/10.9755/ejfa.2020.v32.i11.2197

[X4] Variations of Essential Oil Constituents in Oregano (Origanum vulgare subsp. viridulum (= O. heracleoticum) over Cultivation Cycles.

Plants 2020, 9, 1174; doi:10.3390/plants9091174

[X5] Citrus bergamia, Risso: the peel, the juice and the seed oil of the bergamot fruit of Reggio Calabria (South Italy).

Emirates Journal of Food and Agriculture, Vol. 32, no. 7, Sept. 2020, pp. 522-3,

DOI: 10.9755/ejfa.2020.v32.i7.2128

[X6] Plant Shoot Age and Temperature Effects on Essential Oil Yield and Oil Composition of Rose-Scented Geranium (Pelargonium sp.) Grown in South Africa.

Journal of Essential Oil Research Volume 18, 2006 - Issue sup1.

 https://doi.org/10.1080/10412905.2006.12067129

[X7] A study on the extraction of essential oil of Persian black cumin using static supercritical CO2 extraction, and comparison with hydro-distillation extraction method.

Separation Science, 10.1080/01496395.2018.1541907Technology (Philadelphia) Volume 54, Issue 11, Pages 1778 – 1786 24 July 2019

https://doi.org/10.1080/01496395.2018.1541907

1. Re-arrange the numbering of references in the manuscript from the first one to the last one. References have to be numbered with the same order of appearance in the text. Whereas your first reference is the number 13 and after the number 18 and 31. Please. Re-arrange: 1, 2, 3 ….. and so on. Re-arrange the manuscript and the whole references section;
2. Table 9, please an International Reader want to know as you have considered α-pinene, in which group of component. The same for each component. Before or after each component insert one symbol (the same symbol) for all Monoterpenes you have listed; a different symbol (the same symbol) for all Oxygenated Monoterpenes you have listed; a different symbol (the same symbol) for all Sesquiterpenes you have listed, and so on. After this apply the symbol you have choosen for each monoterpenes before or after the total content of monoterpenes, and so on…;
3. Table 9, why have you written α-pinene and its RT in bold?
4. Table 9: Monoterpens or Monoterpenes? Please, verify, the same for each group of components in the table and in the whole manuscript, verify the correct names;
5. Please, write in blue color or evidence differently the corrections you will do

I suggest a major revision

Regards.

Comments for author File: Comments.pdf

Author Response

Dear reviewer 

Thank you for your constructive suggestions for the second round. I have incorporated the point you raised and also corrected the errors. 

Point 1. I have included all the references you listed and a few others. 

Point 2. The references are also re-arranged according to their appearance in the text. 

Point 3.  I have included a symbol in a bracket for easy identification of the chemical components and their respective chemical classes. 

Point 4 and 5. I have corrected the errors

Point 6. I have indicated all the corrections in blue color for your reference. 

Once more, thank you, and let me know if you have additional suggestions. Meanwhile, I will further check the manuscript for improvement. 

Author Response File: Author Response.docx