Pakchoi Antioxidant Improvement and Differential Rhizobacterial Community Composition under Organic Fertilization
Round 1
Reviewer 1 Report
The paper is well written and the results are discussed using statistical methods. This Integrated approach of research should be marked in Introduction and definition given together with related references. In conclusion limits and advantages of research should be added and a new section Perspective inserted.
Author Response
Response to Reviewer 1 Comments
Point 1: The paper is well written and the results are discussed using statistical methods. This Integrated approach of research should be marked in Introduction and definition given together with related references. In conclusion limits and advantages of research should be added and a new section Perspective inserted.
Response 1: Thanks for pointing this out and we agree with the reviewer. We have added a section in Introduction to provide background of pyrosequencing and its analysis approach (Line 82-93). We also add the Conclusion part, as shown in the Line 474-487.
Author Response File: 
Author Response.docx
Reviewer 2 Report
Very good and well written manuscript. I have only a few suggestions that in my point of view might even improve the manuscript:
I am slightly missing relation to sustainability. I would propose to include one or two sentences into the aims of the study relation.
The discussion is very good, but I am missing discussion on production of antioxidizers from the point of view of the plant (i.e. why does the plant produce higher level of antioxiderz in better conditions, I feel this a bit like contradiction).
I am missing clear recommendation related to sustainability. I would propose to add a short section into the discussion and compare the traditional way of pakchoi production (I suppose is not done using organic fertilizers) to use of organic fertilizers. Here it looks like the possibility of increasing sustaiability together with improved production.
I would recommend to include the short conclusions of the study, since the data are numerous and reveal several interesting facts.
Author Response
Response to Reviewer 2 Comments
Very good and well written manuscript. I have only a few suggestions that in my point of view might even improve the manuscript:
Point 1: I am slightly missing relation to sustainability. I would propose to include one or two sentences into the aims of the study relation.
Response 1: Thanks for your suggestion. We have added two sentences at the end of Introduction. (Line 100-103)
Point 2: The discussion is very good, but I am missing discussion on production of antioxidizers from the point of view of the plant (i.e. why does the plant produce higher level of antioxiderz in better conditions, I feel this a bit like contradiction).
Response 2: Thanks for your comments. It is well known that organic farming improves soil quality when compared to conventional farming. Our previous studies have been demonstrated that organic N (e.g. glycine) application could stimulate the accumulation of diverse antioxidants in plant [1-3]. Consistently, our results also showed that total organic N in soil was positively correlated to phenolic content and phenolic acid. Therefore, the high antioxidant level in plant was a direct consequence caused by high organic N in the organic fertilized soil. In addition, we analyzed the relationship between rhizobacterial community composition and plant antioxidant level. The results showed that specific rhizobacteria were positively correlated to plant antioxidants, including Rhodoplanes, Solirubrobacter, Bacillus and Planctomyces. Interestingly, we also found that Bacillus spp. were differential rhizobacteria in OF. As Bacillus spp. were well known beneficial rhizobacteria, which have been reported to increase plant biotic and abiotic stress by stimulating the antioxidants (e.g. phenolics and antioxidant enzymes) accumulation in plant [4]. Hence, we speculated that the antioxidants improvement in OF might not only cause by the increased organic N but also the enriched specific rhizobacteria. Indeed, the pathogen invasion and stress conditions generally induce higher antioxidant levels since this is the original defense system in plant. In other words, the plant with high antioxidant levels in OF might possess relative high resistance of the environmental stresses or pathogenic microbes.
Point 3: I am missing clear recommendation related to sustainability. I would propose to add a short section into the discussion and compare the traditional way of pakchoi production (I suppose is not done using organic fertilizers) to use of organic fertilizers. Here it looks like the possibility of increasing sustaiability together with improved production.
Response 3: Thanks for your comments. Indeed, organic farming generally has lower yield than conventional farming. The main reason is the relative low efficient nutrient supply by organic fertilizer. To reach the same yield of conventional farming, organic farmers usually apply 2-3 times organic fertilizer than chemical fertilizer in China. Thus, the amount of organic fertilizer used in our study was two times higher than chemical fertilizer based on N content. Our results showed that the yields of both CF and OF were significantly higher than CK. It should be noted that this is short-term experiment. Since the overuse of organic fertilizer may result in high salinity in the soil in long-term application. This phenomenon is not a sustainable agricultural system. Therefore, It should be evaluated under long-term fertilization to obtain more reliable results, and further applied in field conditions. In this regard, we cannot recommend the suitable fertilization strategy for sustainable agricultural production. However, we found that several rhizobacteria were positively correlated to plant biomass or antioxidant activity. This allowed us to explore the potential beneficial rhizobacteria for sustainable agricultural production by combining plant performance and rhizobacterial community composition. We have added two sentences at the end of Introduction, emphasized the relationship between plant performance and rhizobacterial community composition, and their implication for the selection of beneficial rhizobacteria for sustainable agricultural production.
Point 4: I would recommend to include the short conclusions of the study, since the data are numerous and reveal several interesting facts.
Reponse 4: Thanks for your kindly suggestion. We have added the Conclusions part in the revision (Line 474-487).
Thanks again for the reviewer 2’s positive comments and suggestions!
[1] W. Xiaoli, Y. Wenjuan, Z. Qian, H. Ruifeng, H. Danfeng, Metabolic response of pakchoi leaves to amino acid nitrogen, Journal of Integrative Agriculture, (2013).
[2] X. Yang, L. Feng, L. Zhao, X. Liu, D. Hassani, D. Huang, Effect of glycine nitrogen on lettuce growth under soilless culture: a metabolomics approach to identify the main changes occurred in plant primary and secondary metabolism, J Sci. Food Agric., 98 (2018) 467-477.
[3] X. Yang, X. Cui, L. Zhao, D. Guo, L. Feng, S. Wei, C. Zhao, D. Huang, Exogenous Glycine Nitrogen Enhances Accumulation of Glycosylated Flavonoids and Antioxidant Activity in Lettuce (Lactuca sativa L.), Front Plant Sci, 8 (2017) 2098.
[4] C.W. Bacon, E.R. Palencia, D.M. Hinton, Abiotic and Biotic Plant Stress-Tolerant and Beneficial Secondary Metabolites Produced by Endophytic Bacillus Species, Springer India, 2015.
Author Response File: Author Response.docx
Reviewer 3 Report
The manuscript is well written and included valuable solid data and information. Please find my specific comments as follow and my general comments on the attached file.
Line 2: In the title, can you be more specific about using this term: shifts ?
Can you indicate if it is positive shift or if the application of OF and CF improved the level of antioxidant based on your results.
Line 35: You may add 'Pakchoi' to the keywords
Line 82-83: Pakchoi, a common short-term leafy vegetable with an economic importance in China was used as the model system.
Line 90: (0-20 cm sampling depth include the entire root zone)
Line 114: How many seeds?
Line 115: 1/2 Murashige and Skoog-MS solid medium
Line 119: edit the font for C
Line 120: Please indicate the water was tap water or DI?
Line 124: The pakchoi plants and soils
Line 136 and 141: edit the font for C
Line 229: have
Line 238: than the control
Line 253: variables.
Figure 2, 3 and 4. Graphs font must be match with the body of manuscript
line 434: Planctomyces
Comments for author File: 
Comments.pdf
Author Response
The manuscript is well written and included valuable solid data and information. Please find my specific comments as follow and my general comments on the attached file.
Point 1: Line 2: In the title, can you be more specific about using this term: shifts ?
Can you indicate if it is positive shift or if the application of OF and CF improved the level of antioxidant based on your results.
Response 1: Thanks for your comments. We changed the title as “Pakchoi antioxidants improvement and differential rhizobacterial community composition under organic fertilization”
Point 2:
Line 35: You may add 'Pakchoi' to the keywords
Line 82-83: Pakchoi, a common short-term leafy vegetable with an economic importance in China was used as the model system.
Line 90: (0-20 cm sampling depth include the entire root zone)
Line 114: How many seeds?
Line 115: 1/2 Murashige and Skoog-MS solid medium
Line 119: edit the font for C
Line 120: Please indicate the water was tap water or DI?
Line 124: The pakchoi plants and soils
Line 136 and 141: edit the font for C
Line 229: have
Line 238: than the control
Line 253: variables.
Figure 2, 3 and 4. Graphs font must be match with the body of manuscript
line 434: Planctomyces
Response 2:
We appreciate these suggestions and the suggested changed has been made in this revision. In addition, this revision was modified by the professional Engilish-editing service provided by MDPI.
Author Response File: Author Response.docx
