Overview of Multiple Applications of Basil Species and Cultivars and the Effects of Production Environmental Parameters on Yields and Secondary Metabolites in Hydroponic Systems

Round 1

Reviewer 1 Report

Peer review report on “multiple applications of basil (Ocimum basilicum L.) and the effects of production environmental parameters on  yields and secondary metabolites in hydroponic system

Comments

This review paper discusses the importance of the use of hydroponic to minimize high greenhouse gases. Here the authors focused on microgreens with the use of different substrates. They mainly concentrate on basil plants intending to provide multiple benefits of basils. They also review the data on available hydroponic systems and the effects of the production environment on basil yield quantity 103 and quality basil microgreens

Major comments

• One main point is that the authors should include the period for which they conducted the literature survey. The literature databases the authors used and the keywords they used for searching.
• Are there any isolated compounds from Basil leaves?
• It is not clear whether the hydrophobic systems the authors are discussing use to grow Basil plants.

Minor Comments

• The title should be corrected as “…secondary metabolites in the hydroponic system.”
• Table 3. Why are there 2 lines for temperature?
• Table 3, 1.1 is the light intensity in the growth chamber? And what is meant by “light” in 1?

Author Response

Dear reviewer,

Thank you very much for your recommendations. These were very useful for our paper.

We mention that we have made all these corrections, see below.

Comments

Query: This review paper discusses the importance of the use of hydroponic to minimize high greenhouse gases. Here the authors focused on microgreens with the use of different substrates. They mainly concentrate on basil plants intending to provide multiple benefits of basils. They also review the data on available hydroponic systems and the effects of the production environment on basil yield quantity and quality basil microgreens

Response: Your review is very correct

Major comments

Query: One main point is that the authors should include the period for which they conducted the literature survey. The literature databases the authors used and the keywords they used for searching.

Response: We have included in point 2. Materials and Methods: *The research was conducted between December 2020 and August 2021, using the databases: Web of Sciences, Scopus, Science Direct, Google Scholars* (L: 118-119).

Regarding the search keys, we have included the following specification: *The review of the literature and data collection followed in detail certain keywords relevant for the production of basil microgreens in hydroponic systems, such as: temperature, humidity, pH, electrical conductivity, oxygen dissolved in water, carbon dioxide, nutrient solutions, and the influence of light (quantity, quality and photoperiods)* (L:122-125 ).

Query: Are there any isolated compounds from Basil leaves?

Response: Yes, there is, we refer to them in point 3.1 Multiple applications of Basil, paragraph 2-3  (L: 146-186).

Query: It is not clear whether the hydroponic systems the authors are discussing use to grow Basil plants.

Response: Yes, they can all be used for hydroponic basil. We changed phrasing to reflect this (L: 202).

Minor Comments

Query: The title should be corrected as “…secondary metabolites in the hydroponic system.”

Response: the correction has been made (L: 4).

Query: Table 3. Why are there 2 lines for temperature?

Response: I corrected, it is the ambient (air) temperature in growth chamber and the temperature of the nutrient solution, which has significant affects on growth in controlled environment agriculture (L: 224).

Query: Table 3, 1.1 is the light intensity in the growth chamber? And what is meant by “light” in 1?:

Response: In table 3, light under 1 is the deleted as we find it not relevant. 1.1 is photoperiodicity defined as the number of hours that the plants are exposed to light in growth chambers (L: 224).

Reviewer 2 Report

The effort made by the authors is very valuable, as nowadays it is impossible to follow most of the current literature on a topic of interest. This paper is a comprehensive review focused on the applications of Ocimum basilicum L. and the effects of production environmental parameters on yields and secondary metabolites in a hydroponic system. The manuscript fits within the scope of the journal. The title is clear and it is adequate to the content of the article. The author’s work on discussing achieved results is appreciated but the revisions are necessary to improve the clarity of the presentation.

I suggest restructuring the abstract. It is currently too long.

I suggest including a graphical abstract

I suggest including in-text some diagram/scheme if is possible.

Please standardize the writing of citation indexes in the text, in accordance with the requirements of the journal

- Please include citations for all paragraphs. For example: ” Hydroponic production of microgreens offers the potential to produce fresh produce with a short production cycle that has a high concentration of nutrients, vitamins and beneficial secondary metabolites. Hydroponics practices are increasing due to the increasing effects of conventional agriculture on human health, aquatic bodies and environmental externalities. However, there are a number of challenges faced by the microgreens producers, hindering uptake and adoption. Firstly, there are a number of hydroponics systems available in the market and it can be overwhelming for a producer to make a decision on the hydroponic system. Secondly, production parameters viz. light intensity, light quality (spectrum combinations) and photoperiod, pH, electrical conductivity, air and water temperature, nutrient solution, CO2 content and air circulation have huge effects on the crop yield in terms of quantity and quality. Thirdly, there is wide species-specific and cultivar-specific variation in crop yields and nutritional contents under similar production environments for microgreens.”

” For instance, basil is used both in traditional and in scientific medicine as a result of the presence of health-promoting compounds and essential oils. Basil essential oils have an important role in reducing inflammation, muscle spasms, have antibacterial and antifungal activity, and have a beneficial influence on the respiratory and digestive system”

” Flavonoids and other phenolic compounds are secondary metabolites of plants, and they are known to have beneficial effects on the human body. Currently, more than 8000 compounds have been identified”

…and others

Check the bibliography to be written according to the requirements of the journal.

Author Response

Please see the attachment

Author Response File: Author Response.pdf

Reviewer 3 Report

The present review submitted to sustainability MDPI fits within the general scope of the Journal. The authors presented a detailed review paper on basil and how hydroponics of basil could modulate yield and nutritional and functional uality of basil. However, from my humble point of view the review is of low originality especially that several parts are very confusing since in the abstract section and the conclusions the authors focused on speciality crops such as microgreens while in the whole review very broad and well known concepts were reported such as the influence of environmetal factors such as light quantity and quality, air temperature, relative humidity as well as the nutrient solution management in terms of pH and EC could modulate the quality of basil. The review paper seems more a Master or a PhD thesis rather a critical review and it is very hard to follow the major stream of the paper: hydroponics of mature basil or microgreens.

In few words the review paper is very descriptive and does not bring new insight for the readers of sustainability.

Author Response

Dear reviewer,

Thank you very much for your recommendations. These were very useful for our paper.

We mention that we have made all these corrections, see the revised paper.

Query: The present review submitted to sustainability MDPI fits within the general scope of the Journal. The authors presented a detailed review paper on basil and how hydroponics of basil could modulate yield and nutritional and functional quality of basil. However, from my humble point of view the review is of low originality especially that several parts are very confusing since in the abstract section and the conclusions the authors focused on speciality crops such as microgreens while in the whole review very broad and well known concepts were reported such as the influence of environmental factors such as light quantity and quality, air temperature, relative humidity as well as the nutrient solution management in terms of pH and EC could modulate the quality of basil. The review paper seems more a Master or a PhD thesis rather a critical review and it is very hard to follow the major stream of the paper: hydroponics of mature basil or microgreens.

Response: The authors have taken note of the comments and have revisited the manuscript to emphasize the main message that basil microgreen is the focus but can be also applied to other microgreens in general.  Furthermore, any mention of mature basil is because this is where the research has been focused on valuable secondary metabolite (oils, etc.) production. The paper was carried out in order to evaluate the advantages of cultivating basil, its vegetation requirements in the hydroponic environment, but especially in the microgreens stage. This is because hydroponic microgreens basil (but also to other species) production environmental parameters to obtain quality microgreens are not standardized, and best practices are not established. We are interested in the possibilities of managing and augmenting these environmental conditions in order to obtain qualitative and quantitative improvements of the production; i.e. the desirable qualities of microgreens basil and mature basil are not the same, which necessitates different input standardizations, which do not currently exist. The objective of the project in which this paper was made comes from the following project: https://www.gohydro.org/, whose goal is to synthesize the information for quality and quantity hydroponic basil microgreens production.

Query: In few words the review paper is very descriptive and does not bring new insight for the readers of sustainability.

Response: In our opinion, the paper presents all the necessary information and provides a synthesis of current substrates used, describes a diversity of production systems and ranges of production parameters to be maintained for basil microgreen production, which depends on the production objective of the producer to plan for quantity and quality production. The findings are put together in 5 tables, which provides a good overview of production practices in microgreens, which are useful resources for the microgreen producers and for the researchers to further improve upon those tested environments. The study findings will facilitate the testing and improvement of microgreen hydroponic platforms, in order to obtain basil microgreens, as well as the possibilities to improve the quality and quantity of production. These ‘best practices’ are not known, which necessitates future research and the collection of existing research into reviews to help make this novel research possible.

Reviewer 4 Report

The manuscript entitled "Overview of multiple applications of basil (Ocimum basilicum L.) and the effects of production environmental parameters on yields and secondary metabolites in hydroponic system" deals with an interesting topic, however, the study needs to be improved since authors failed to present some of the results appropriately. The English language needs to be corrected carefully throughout the whole manuscript, since at this point, many mistakes can be seen, both in grammar and in used terms. The main flow of  the study is that the authors used as an object (in the title and through the whole manuscript) species Ocimum basilicum. However, it is evident that tables and the main text references are related to different species of genus Ocimum. This should be carefully checked and authors should decide whether to use only O. basilicum as an object or to improve the presentation of obtained results to other species or cultivars of basil. 

L 12 - add Latin name

L26 - correct to "between 200 and 400"

L26-27 - "Basil microgreens are an excellent source of nutritional compounds which maintain human health" please delete this part since maintenance of human health was not part of the review

L30-33 - please improve this part, it is unclear.

L60 - stage, not "state"

L83 - "silos", please use the appropriate term.

L84 - "to produce fresh produce", please correct.

L84-88 - this is the repetition of the previous paragraph.

L88-89 - "However, there are a number of challenges faced by the microgreens producers, hindering uptake and adoption", please correct.

L90 - please correct "overwhelming"

L102 - please correct "qualityin" to quality in 

L103-104 - reformulate

General remark - why are the numbers included in the first column for most of the tables? Tables should be presented better; there is no need for "can be" or "is"...

L150 - phenolic instead of "organic"; rosemary?

L156 - "more than 8000 compounds have been identified", which type of compounds, phenolics?

L164 - please correct rosemary to rosmarinic acid

L166 - what is the "basil type"? Also, the concentration of phenolic acids in basil is very variable, authors should exclude concentrations.

L167-172 - it is not relevant, please delete it.

L174-176 - please reformulate.

L207 - what do you mean by "specialized literature"?

L231 - "dermination faculty", what do you mean?

Table 4 - please explain how is this related to basil in hydroponics?

L309-327 - to the best of my knowledge, basil plants are indifferent to light. Therefore, this paragraph could not be related to basil plants in general. Please delete it. 

Author Response

Please see the attachment

Author Response File: Author Response.pdf

Round 2

Reviewer 3 Report

the apper has been improved it can be accepted

Author Response

Thank you very much.

Reviewer 4 Report

L 31-34: "This information is useful for the food entrepreneurs producing their own microgreens or budding entrepreneurs, who are either planning to produce or want to improve the quality and quantity of microgreen production for better acceptance by the consumers." 

I don't see the scientific significance of this part of the abstract.

For a better presentation of the reviewed literature, please delete from the table terms like "basil has demonstrated", "has been shown", "has shown", "it has also been shown"... The tables are, of course, related to basil, there is no need to put additional text in tables and to repeat it constantly.

Author Response

Dear Reviewer,
Thanks for your recommendations.
Please find below the corrections made:

Query: L 31-34: "This information is useful for the food entrepreneurs producing their own microgreens or budding entrepreneurs, who are either planning to produce or want to improve the quality and quantity of microgreen production for better acceptance by the consumers." 

I don't see the scientific significance of this part of the abstract.

Response: We have therefore changed the lines to “This information can inform research that will test platforms for both successfully obtaining microgreens, with a focus on basil species and cultivars, and establishing testing protocols to improve the quantity and quality of the harvest.” L 31-34

Query: For a better presentation of the reviewed literature, please delete from the table terms like "basil has demonstrated", "has been shown", "has shown", "it has also been shown"... The tables are, of course, related to basil, there is no need to put additional text in tables and to repeat it constantly.

Response: We have deleted all incidences of ‘basil,’ or ‘basil has demonstrated,’ etc., in response to this request. See track changes in Table 1, 5, 6 (L 144, 330, 472).

Round 3

Reviewer 4 Report

The authors put the effort into improving the manuscript.