Effects of Arbuscular Mycorrhizal Fungi on Growth and Physiological Performance of Catalpa bungei C.A.Mey. under Drought Stress

Round 1

Reviewer 1 Report

Dear authors,

Hope you all are safe and in good health. 

The article is very interesting but needs a major revision before publishing. You can see below my comments:

General comments

This research deals with aspects of the effects of arbuscular mycorrhizal fungi on the growth and physiological performance of Catalpa bungei under drought stress. More specifically, in this study, the authors used 86 pot experiments to simulate drought stress and explore the effects of AMF inoculation on the 87 growth characteristics of C. bungei under different water conditions. Specifically, they aimed to 88 elucidate the relevant mechanisms of action of AMF with regard to root morphology, nutrient 89 absorptions, photosynthesis, ROS removal capacity, endogenous hormone regulation, and the effect 90 of AMF on soil structure. The authors intend to provide a theoretical basis for the application of AMF in the 91 afforestation and cultivation of C. bungei in Northwest China. The article concluded that inoculation with R. intraradices is potentially useful for afforestation and cultivation of C. bungei in Northwest China.

 

Specific comments

Line 10-38: Please reduce the words of the abstract (300 words, see the instructions of authors), and write the most important results.

Line 92: Please add a map with geographical coordinates for the study area.

Line 92: Please describe the study area.

Line 144: Please add a reference.

Line 152: Please add a reference.

Line 162: Please add a reference.

Line 166: Please add a reference.

Line 191: Please add a reference.

Line 196: Please add a reference.

Line 779:  Please write clear only the main conclusions and refer a future prospect.

Please, the manuscript should be thoroughly and carefully checked for language corrections/improvements, and these changes will have to be made accordingly.

Author Response

Please see the attachment, thank you.

Author Response File: Author Response.docx

Reviewer 2 Report

General comment

 

I was generally impressed by the way this paper was constructed and written. It sets the scene nicely with a comprehensive but not overly dense introduction which is well grounded and projects a depth of understanding of the topic at hand. The data represents a substantial body of work that seems (for the most part) to be thoroughly completed. My comments as a result are largely just detailed suggestions designed to improve. I do however have a few comments that are more substantive however and that should be addressed.

The more substantive comments are :

I am not convinced that their ethylene measurement protocol would actually truly reflect the ethylene concentrations present. The mere act of cutting the leaves into pieces would likely induce ETH production and therefore this method is possibly more a way of analyzing the maximum possible ETH production rather than the ETH present at the time of sampling. If they can quote precedent for using this method and highlight justifications in this (these) paper(s) that the method is not negatively affected by de novo synthesis of ethylene after the wounding process I would be more comfortable with leaving this data in the manuscript. It does not feature greatly in the rest of the manuscript anyway, so I think it could be deleted without taking too much away from the central message. Alternatively the measurements need to state a proviso that makes it clear what the uncertainty is around this method.

They also need to provide greater clarity about which GA form (or is it several?) that they are measuring. There are many possible forms of GA and there is still a great deal of uncertainty about the possibility of specialized roles for some of these forms. For greater clarity the work needs to make it clear exactly what their GA data refers to.

I would like more clarity around their method for measuring GRSP as it seems to just measure total protein released under two variants of extraction procedures. If there is evidence that this largely releases GRSP proteins then that needs to be presented to allow people to determine whether their specific mention of two forms of GRSP is warranted or they need to refer to total protein content instead and describe how this is "suggested" to contain significant amounts of the two forms of GRSP and that they infer these are the main varying constituents.

The less substantive/more detailed comments on the sections are:

AMF source:

I would have preferred to know the original source of the AMF inoculum used rather than just referencing the institution from which it was obtained as this could well end up influencing the effects-questions like did it come from a similar soil type, was it adapted to the host upon which it is now being tailed come to mind as relevant.

Soil water content:

How was the maximum soil water content determined and how were the figures of 70%, 50% and 30% of this capacity worked out? At least a reference here would be helpful so it can be repeated.

Sterilization:

The protocol states 121C for 2 hours but I know from practical experience that this is almost impossible to achieve at such a simple "single temperature -time" profile within the soil when it comes to sterilizing significant quantities of soil. If this was just the setting on the autoclave that should be stipulated. In that case the reality will be that the temperature of 121C was only reached for a portion of the 2 hour process. I am not saying this invalidates the approach but this is often glossed over by people and that means some do not realise the limitations of the technology.

Section 2.6-please reference these methods

AMF genetics:

There is no inclusion or reference to the fact that the genetics of the AMF samples chosen to treat plants with could have a significant impact on the outcome of the interaction. This was partly behind my comment about identifying AMF source as this would be expected to have an impact on the genetics of the inoculum used and with the possibility of adaptation to the major symbiotic plant partners at the source this should be recognized as another area of uncertainty and future focus. Often AMF papers treat a species of AMF as effectively uniform in effect -which I seriously doubt is really the case in nature. Please don't ignore the influence of genetics on all the players -as a major contributing factor that we often fail to understand.

AMF root colonization:

How was this % calculated was the presence of any one of the three structures mentioned counted as a positive colonization or was a minimum number of one or all three required before the root was declared colonized…?

Figure 1. The legend almost implies the AMF develop as a result of staining -but I am sure what they mean to say is that this development was monitored by staining-suggest rewording.

 

Table 1 Define DS as Drought Stress

 

Be careful about using a short-hand way to refer to plants treated with mycorrhiza as that (in my opinion) can read very strangely as implying the plants are mycorrhiza. There are many instances of these throughout the document but some examples and suggested modifications include:

                                   inoculated

Line 549 …for mycorrhizal   V       Broussonetia papyrifera..

                                        treated

Line 551 ..non-mycorrhizal    V       seedlings

 

Author Response

Please see the attachment, thank you.

Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

Dear authors,

you have made all necessary changes in the manuscript. Good work.