Responses of Maize (Zea mays L.) Roots to Nitrogen Heterogeneity and Intraspecific Competition: Evidence from a Pot Experiment Using the ‘Root Splitting’ Approach

Round 1

Reviewer 1 Report

This type of experiments is quite common. There is a lack of reference to these past studies in the introduction and the objectives are not clearly stated. The introduction should clearly expose the state of knowledge and what remains to be discovered and how this links with the present study. The methods section should say how many replicates per treatments. I feel there may have been too little replication which prevented statistical differences in treatments. I found the results section much too long with too many very small graphs. The results section was also punctuated with discussion sentences and references that do not belong there. Also the text “talks statistics” rather than biology, e.g. “heterogenous nitrogen was higher than homogenous” while it is the plants that increased in size, not the treatments.

I nevertheless found the study interesting and worth publishing

 

L32 « production » leading to … unclear

L38 should add a few references to this effect

L55 contradicts L39

L57 add a reference showing that this response depends on species

L59 add a reference

L60 plants or roots?

L78 these are concentrations not contents

L88 it is the replicates that should be disposed randomly in the greenhouse

L89 I don’t understand this. Intraspecific competition would normally relate to maize plants density, not to nutrient concentration? From Fig 1 I understand that the quantity of nutriments per seedling was the same but doubled in total when two plants were used instead of one

L93 trumpet stage?

L118 6 plants? Per treatment? How many replicates? How many plants per replicate?

L140-142 does not belong in the data analysis section

L148 I am not sure what this means

L149 what were the tested factors?

L166 Main effects should not be discussed alone if they interact with the other factor such as for plant height

L168 what is root ratio? I don’t see an effect of ND on root/shoot ratio in Table 2

Fig 2 what are the error bars and why are they absent for NC bars on graphs c and d? It seems like the number of replicates was too low and prevented to get statistical differences

L201 this kind of statement needs a reference and does not belong in results section.

Fig 3 need to say what the bars are and what the letters mean

L232 Authors need to be careful how they report results. Sentences such as “homogenous nitrogen was higher than heterogenous nitrogen” does not make any sense. It the root-to-shoot ratios that were higher in homogenous conditions.

L241 does not belong here

Fig 6 why use here different symbols for the axes?

L288 does not belong here

Top paragraph P 10 belongs to discussion

The discussion should start with most important findings of this study, not of other people’s studies

L444 all traits? Table 1 shows some effects

 

 

 

 

 

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 2 Report

 

The study uses a clever design to look at how the heterogeneity of N in the soil affects the plants growth patterns with and without intraspecific competition.

However, there are major difficulties and I would not approve it for publication. Mainly as most of the results discussed where clearly not significant. One can not even call it a tendency.

Some general comment below

 

Introduction

There are no clear reaserch questions or hypothesis in the end of the discussion

 

Results

At the end of most result section there is a paragraph with discussion which I think fits better in the discussion.

 

3.1 is not needed. There is just text saying that there are significant differences but how they are different comes in the 3.2 and onwards. I think table 2 can go to the supplements and the three significant interactions which is the only additional data as compared to the figures presented can be presented in the text

 

3.2. there is nothing significant. Not even close. Not much to present as there is nothing to discuss

 

3.3. no effect of nitrogen distribution and those traits are parts of biomass and yield where you have clearer diffrences. Skip paragraph and put digrams in suppliments

 

3.4

Row 240 and onwards.. here is the conclusion of the whole paper written. Wait with that please

And it is based on non significant results.

 

3.5 this is interesting. That the specific root length is so strongly affected by heterogeneity when no competition but not with competition. This is something that should be discussed more. And it is significant. However comparing the two sides is pointless. Thesr is nowhere even close to significant

 

Figure 5. caption: “heterogeneous distribution of nitrogen specific root length at flowering” this is not a compleast sentences. Please write longer so it is clear what it is.

 

3.5 figure 6 and 7. Yes. Roots grow where there is nitrogen but what does it answer of the questions I think you are asking?

 

 

Figure 8 should be after 5

 

Figure 9 is interesting.( Caption test is not describing the figure)

This results could be discussed more

 

Discussion

A lot of non significant results are discussed. Without being backed up by literature suggesting that this is reasonabal.

 

Conclusions.

The main conclusion is based on a non significant result. That is not okej.

 

 

 

 

 

 

 

Check that tables and tables are referd to properly. For example row 231 should also refer to the figure ad not just table 2

 

 

The results are mainly not significant. These non significant differences are still presented and to a large extent discussed. They are however always very clear saying that it was not significant but it suggests this and that.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf