Effects of Nitrate Assimilation in Leaves and Roots on Biomass Allocation and Drought Stress Responses in Poplar Seedlings
Round 1
Reviewer 1 Report
Comments and Suggestions for Authors“Effects of nitrate assimilation in leaves and roots on biomass allocation and drought stress responses in poplar seedlings”
Comments:
This manuscript evaluates the biomass allocation patterns of two poplar clones varying greatly in drought resistance under the combinations of two levels of soil water and nitrogen availabilities and some of the physiological processes related with carbon and nitrogen metabolism that might be involved in biomass partitioning, to test the hypothesis that they follow different partitioning patterns. The greenhouse experiment was carefully designed, with an adequate control of treatments and sample size for both clones, using appropriate methodological protocols for the ecophysiological traits and lab analysis. The data analysis and statistical procedures used were also adequate to test the objectives and hypothesis of the study. The results are presented in a coherent and comprehensive way, and they are appropriately interpreted and discussed. Thus, except for a few minor points, which are identified as comments directly on the manuscript (PDF file), it is clearly written and well organized, so I think this contribution has the merits to be published in this journal after a minor revision.
The minor points commented in the manuscript are:
a) In the last paragraph of the introduction section, it might be important to add a brief information on the natural distribution of the Populus species represented by the two clones, and the environmental conditions where they have evolved, since this might help explaining why they might have different partitioning patterns, associated to different selection pressures, and the reasons to use them for the objectives of the study.
b) Considering the contrasting origins of the two clones tested, it would be important to have initial data (before starting the water and nitrogen treatments) on their plant size and biomass fractioning, since initial differences between them, particularly on biomass fractions, would have affected the response to the treatments applied.
c) Even though the soil water content differs between the two treatments used (80±5% and 40±5% of field capacity), in terms of soil water potential, -0.05 MPa represents only a mild water shortage. It would be important to mention if there were any measurements of maximum and minimum values of plant water potential reached by each clone during the drought treatments. Considering the contrasting origins, and the possibly initial differences in biomass fractions, this might help to explain the contrasting response in biomass allocation patterns.
d) Check for minor editing points marked directly on the manuscript PDF file, particularly in the Methods section, the first paragraph of the introduction, in Figures 1, 2 and 4, and the footnote in Table 1.
Comments for author File: Comments.zip
Author Response
Reviewer 1:
This manuscript evaluates the biomass allocation patterns of two poplar clones varying greatly in drought resistance under the combinations of two levels of soil water and nitrogen availabilities and some of the physiological processes related with carbon and nitrogen metabolism that might be involved in biomass partitioning, to test the hypothesis that they follow different partitioning patterns. The greenhouse experiment was carefully designed, with an adequate control of treatments and sample size for both clones, using appropriate methodological protocols for the ecophysiological traits and lab analysis. The data analysis and statistical procedures used were also adequate to test the objectives and hypothesis of the study. The results are presented in a coherent and comprehensive way, and they are appropriately interpreted and discussed. Thus, except for a few minor points, which are identified as comments directly on the manuscript (PDF file), it is clearly written and well organized, so I think this contribution has the merits to be published in this journal after a minor revision.
The minor points commented in the manuscript are:
- a) In the last paragraph of the introduction section, it might be important to add a brief information on the natural distribution of the Populus species represented by the two clones, and the environmental conditions where they have evolved, since this might help explaining why they might have different partitioning patterns, associated to different selection pressures, and the reasons to use them for the objectives of the study.
Response: Thank you for the suggestion. The brief information and natural distribution of Biyu and Xiaoye has been added in the last paragraph of Introduction.
- b) Considering the contrasting origins of the two clones tested, it would be important to have initial data (before starting the water and nitrogen treatments) on their plant size and biomass fractioning, since initial differences between them, particularly on biomass fractions, would have affected the response to the treatments applied.
Response: This is a valuable comment. Unfortunately we did not measure these initial data before starting treatments. However, at the start of the experiment, plants of the two clones had approximately the same heights and diameters, which makes us believe that the differences observed are mainly due to clonal and treatment differences. This is also supported by the fact that Biyu and Xiaoye in the CK treatment showed similar height, base diameter, and biomass allocation fractions (Table S1, Figure 1). However, we thank you for the advice that we will take into account in future studies.
- c) Even though the soil water content differs between the two treatments used (80±5% and 40±5% of field capacity), in terms of soil water potential, -0.05 MPa represents only a mild water shortage. It would be important to mention if there were any measurements of maximum and minimum values of plant water potential reached by each clone during the drought treatments. Considering the contrasting origins, and the possibly initial differences in biomass fractions, this might help to explain the contrasting response in biomass allocation patterns.
Response: We agree with you that it could be a mild drought stress when soil tensiometer gave records about −0.05 MPa. Because there were not significant leaf wilting during drought treatment. However, this drought had significantly reduce the growth of two poplar clones’ seedlings, see Table S1 and Table S2.
- d) Check for minor editing points marked directly on the manuscript PDF file, particularly in the Methods section, the first paragraph of the introduction, in Figures 1, 2 and 4, and the footnote in Table 1.
Response: Thanks for your nice, careful, and helpful reminders in PDF file. We have revised these mistakes in the revised version. Figure 2 was drawn by two steps: firstly, α, logβ, R2, and p were calculated through standard major axis regressions using “mastr” package; secondly, and two straight lines with different spots were draw using logβ as intercept and α as slope.
Reviewer 2 Report
Comments and Suggestions for AuthorsThe paper is of high quality and of high importance. This is an attempt to understand biomass allocation patterns in plant species of different habitats. The methodology is appropriate. The results are clearly presented in numerous figures and well discussed.
However some minor corrections are recommended:
Line 16, Abstract: the information about Populus ×euramericana is inconsistent with the information provided in lines 93-93. Populus ×euramericana is a hybrid of Populus deltoides and Populus nigra, not a hybrid of two Populus deltoides clones.
Lines 31-39, Introduction: please remove these journal instructions.
Line 80, Introduction: “(Robinson” should be removed.
Line 189-190, M&M: was normality od data tested? If not, non-parametric statistical tests should be performed instead of ANOVA.
Line 216, Figure 1, caption: I can't see SD shown in the figures. Please, do not mention it in the caption if not shown.
Lines 294-302, Results: please use subscripts when necessary.
Comments on the Quality of English LanguageLine 184, M&M: Dry weight of these parts WAS determinated.
Author Response
Reviewer 2:
The paper is of high quality and of high importance. This is an attempt to understand biomass allocation patterns in plant species of different habitats. The methodology is appropriate. The results are clearly presented in numerous figures and well discussed.
However some minor corrections are recommended:
Line 16, Abstract: the information about Populus × euramericana is inconsistent with the information provided in lines 93-93. Populus × euramericana is a hybrid of Populus deltoides and Populus nigra, not a hybrid of two Populus deltoides clones.
Response: The scientific name of ‘Biyu’ clone has been revised to give clearer information about its parents.
Lines 31-39, Introduction: please remove these journal instructions.
Response: Apologies for this. The paragraph has been deleted.
Line 80, Introduction: “(Robinson” should be removed.
Response: “(Robinson” has been deleted.
Line 189-190, M&M: was normality of data tested? If not, non-parametric statistical tests should be performed instead of ANOVA.
Response: This sentence has been revised to add the normality test method.
Line 216, Figure 1, caption: I can't see SD shown in the figures. Please, do not mention it in the caption if not shown.
Response: Yes, SD was not shown in Figure 1. So “± SD” has been deleted in the caption of Figure 1.
Lines 294-302, Results: please use subscripts when necessary.
Response: Some sentences in Results and other parts have been revised to improve the readability of the manuscript.
Line 184, M&M: Dry weight of these parts WAS determined.
Response: This mistake has been corrected and the whole manuscript has been checked carefully to revise similar mistakes.
Reviewer 3 Report
Comments and Suggestions for AuthorsAuthors investigates the effects of nitrate assimilation under drought conditions on two different poplar clones. They found that Biyu poplar followed APT theory and Xiaoye followed OPT theory. They hypothesize that allocation of biomass based on different strategy is due to place of nitrate assimilation. The paper reads well, however the Introduction part must be substantially rewritten. The very beginning of Introduction is written in bad English with incorrectly formulated sentences. The rest of the paper is better. Authors should put their focus more in discussion on enhancing CO2, rather than reducing it (reduction does not exist in real world).
Moreover, what is the novelty of the paper? It is not stated clearly in Introduction. You should depict in Introduction what is known and why do you investigate your topic - where are the white places of knowledge. Similarly, in discussion you should answer this.
lines 31-39: why do you have it here?
line 42-43: does not make sense, rephrase
line 43?: check typo errors
line 45-46: write better English. Moreover, it is not true.
lines 61-65: this seems strange, why would be CO2 limited? It is rather the opposite, CO2 is increasing? You should re-write this paragraphs in a manner what happens when there is drought and increasing CO2. See paper 10.1093/treephys/tpad024 which you might add here.
Comments on the Quality of English LanguageFirst part of Introduction is incomprehensible and must be rewritten.
Author Response
Reviewer 3:
Authors investigates the effects of nitrate assimilation under drought conditions on two different poplar clones. They found that Biyu poplar followed APT theory and Xiaoye followed OPT theory. They hypothesize that allocation of biomass based on different strategy is due to place of nitrate assimilation. The paper reads well, however the Introduction part must be substantially rewritten. The very beginning of Introduction is written in bad English with incorrectly formulated sentences. The rest of the paper is better. Authors should put their focus more in discussion on enhancing CO2, rather than reducing it (reduction does not exist in real world).
Response: The first paragraph has been deleted and English language has also been checked in other parts of the manuscript.
Moreover, what is the novelty of the paper? It is not stated clearly in Introduction. You should depict in Introduction what is known and why do you investigate your topic - where are the white places of knowledge. Similarly, in discussion you should answer this.
Response: The knowledge gap was added in the last paragraph of Introduction. We also revised the Discussion to answer it more clearly.
lines 31-39: why do you have it here?
Response: This paragraph was from Journal Template and it has been deleted. We apologize.
line 42-43: does not make sense, rephrase
Response: This sentence has been rewritten to make it clearer.
line 43?: check typo errors
Response: English typo errors and mistakes throughout the manuscript have been checked.
line 45-46: write better English. Moreover, it is not true.
Response: This sentence has been deleted.
lines 61-65: this seems strange, why would be CO2 limited? It is rather the opposite, CO2 is increasing? You should re-write this paragraphs in a manner what happens when there is drought and increasing CO2. See paper 10.1093/treephys/tpad024 which you might add here.
Response: Thank you for observing this. CO2 should not been mentioned here and has been deleted.
First part of Introduction is incomprehensible and must be rewritten.
Response: This part of Introduction has been considerably revised to make it clearer to read.
Round 2
Reviewer 3 Report
Comments and Suggestions for AuthorsI thank authors for the changes they did. The quality of the paper and presentation togehther with English is better now.
