Fractal and Topological Analyses and Antioxidant Defense Systems of Alfalfa (Medicago sativa L.) Root System under Drought and Rehydration Regimes
Round 1
Reviewer 1 Report
This paper provides findings on architectural characters and physiological functions of Alfalfa the root system in response to different drought stress and rehydration. This could be an interesting topic for the readers of the Water journal. Research is appropriately designed and results are discussed adequately.
My major comment is that the conclusions are not well written as per the results. The author need to re-write the conclusions accordingly to the objectives and the results. see my comments below.
key discussion and conclusions have to be included in the abstract.
Line 14: In a greenhouse
Line 36-39: “It is concluded that water stress-induced damage and rehydration could mitigate water deficit induced damage in alfalfa root after drought stress, and Medicago sativa L. cv Zhaodong (ZD) and cv Aohan (AH) alfalfa cultivars exhibited higher drought resistances than the cv Golden empress (GE) cultivar due to differences in root system architecture.” This concluding sentence is too long and does not read well. I suggest the authors break this into two sentences and re-write the conclusion.
Line 73-74: The sentence should be supported with a reference.
Line: 136-143: I was wondering about the basis for the different soil moisture levels (water holding capacity %) and rehydration % used for the two greenhouse experiments. Do soil moisture levels represent the field capacity of the soils? Can the authors explain the basis for this and add this to the methods?
I was wondering about the bulk density of the mixture pots and can authors indicate how the packing was done in a bit detail. This is important because the whole experiment depends on the % of water holding capacity of pots.
Line 157 “Each pot weighed” add “was” check for the missing grammar.
Line 174: “2.4.2 design” Design
Line 584-587: “Plant root systems tended to exhibit herringbone branching with smaller total lateral root length, total lateral root number, root surface area and root volume and greater root diameter under less stressful water deficit and rehydration than under severe stressful soil moisture conditions.
For me, it looks like repeating the results in the conclusion section, authors really need to indicate the conclusions drawn from these results.
Further, one of the objectives was to explore the optimum soil moisture levels for alfalfa plant growth using the fractal and topological analysis. However, I do not see such findings in the conclusions part. Can the authors re-write the conclusions according to the objectives?
Author Response
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Author Response.docx
Reviewer 2 Report
This manuscript entitled “Fractal and topological analyses and antioxidant defense systems of alfalfa (Medicago sativa L.) root system under drought and rehydration regimes " is in journal topic and could be of interest for plant scientific community although some other similar studies had been published. The topic is relevant but not original and the paper is too much descriptive with some too speculative discussion according to presented results; some presented conclusions are not in accordance with presented results. However, the manuscript is well-written and can be easily read. I do not agree with the conclusions drawn from part of this study.
Abstract:
L36-40 « It is concluded that water stress-induced damage and rehydration could mitigate water deficit induced damage in alfalfa root after drought stress, and Medicago sativa L. cv Zhaodong (ZD) and cv Aohan (AH) alfalfa cultivars exhibited higher drought resistances than the cv Golden empress (GE) cultivar due to differences in root system architecture. »
Authors can’t conclude that because absence of control plants without rehydration step can’t allow author to know the impact of drought stress alone. Observed phenotypes can be the result of drought or/and rehydration steps (analysis being realized on samples collected at the final time). That’s why I do not agree with this sentences.
L39 : I do not agree with this conclusions since for all alfalfa cultivars, particular observed differences in root systems is concomitant with more or less drought resistance capacity without proving that it is the reason of drought resistance. In fact, other plant molecular modifications could explain these variations on drought tolerance too!
Introduction
Introduction gives sufficient background according to the topic of this paper and the references are relevant.
In L 82 -83 authors: “Recently, root topology and root system architecture have attracted increasing research interests [15]”; cited references are not recent!! Update them!
Material method
Plant cultures were done in a greenhouse without temperature, light and humidity ambient control. Although all the plants were grown together, authors must give some information’s about these parameters.
Are plants fertilized during experimentations?
L.170-172: For plant material choice, authors could specify the range of drought tolerance between cvs. Which cv is known to be tolerant? Sensible?
Drought stress is not evaluated at plant level ; Was plant water potential be modified upon each treatment???
Detection of H2O2: a brief description of technique could be done.
The research design and methods to respond to aims are not completely in adequation with conclusions the authors seem to obtain particularly for biochemical/molecular aspects. We can’t discriminate rehydration impact from drought stress impact since as justified in abstract comment paragraph.
Results
Results are consistent and well described. However, the profusion of figures/tables can lose reader, particularly if he is not a specialist of root anatomy apparatus. Although I am not a specialist in statistics, I recommend verifying if used statistical tests are suitable.
Along result parts, authors characterized each treatment by drought and rehydration regime or by treatment number. Homogenate that.
Discussion
L472: to conclude about a higher proportion of biomass allocated to roots, authors should discuss allocation at plant above-ground level… calculating the shoot/root ratio for each treatment…
The increased of root biomass can be the result of bigger plants (ie. Higher belowground and aboveground parts). So, more precisions are needed to conclude as authors done in this paragraph.
Paragraph 4.4:
Some notions are confused… Some times, the authors refer to drought or to drought followed by rehydration as the same thing. That’s need to be clarify!
L553: “there was a downward trend in MDA content under severe water deficit”
I do not observe this trend…
L554: “drought stress leads to the production of MDA and rehydration could mitigate MDA-induced damage in alfalfa root after drought stress.” Results show in the experiment can not allow to conclude that, since drought and rehydration stages are not decoupled. Where are MDA results upon drought stress alone??
L558-561 : Same last remarks
Author Response
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Author Response File: Author Response.docx
Reviewer 3 Report
The manuscript is interesting and well written. however, sometimes it becomes hard to the reader to follow the information and experiments of the manuscript. I would suggest that the author include schematic figure summerizing the experimental setup of all treatment and measurements.
I would recommend to include transcriptomic analyses in your work. This kind of analysis shall give the exact story behind the observed root phenotypes after drought conditions and rehydration.
Author Response
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Author Response File: Author Response.docx
Round 2
Reviewer 2 Report
Dear Authors,
The authors have revised and improved the paper based on last comments.
L411-413 : Not clear ; I think the interpretations of figure 7 were wrong. I don ’t understand how authors can conclued that. Measurements were made at final time (e.g. 3 weeks after rehydratation beginning) and authors wrote « by subsequent rehydration to 45%--50% ». However at harvest date, the plants had been in rehydration regime for a few weeks untill 75-80% !!!
Must be seriously revised.
L590 : « indicating that rehydration did not increase CAT activity after drought stress ».
I dont find the interest of this interpretation. Why the authors would expect an incresase of this activity ? Drought could induce an oxidative burst with an increase of H202. CAT activity probably increased during drought stress before rehydratation regime application and decreased after.
I find it a pity that the authors did not harvest samples before rehydrating the plants allowing characterization of drought impact on plants.
L594 : « The lower activity of GPX resulted from water deficit, » : Authors can not conclued that since they had no drought treatment alone ! All plants had been rehydrated after water deprivation ! So GPX decreases could result of each of these 2 treatments !
« and the increase in GPX activity from 45%-50% water holding capacity followed by rehydration or 30%-35% water holding capacity followed by rehydration demonstrated that drought stress could decrease the activity of GPX and rehydration could enhance the activity of GR and GPX after severe drought stress. » : In fig 10, we can see an increase in GPX activity comparing soil misture treatments IV or III and I. However, we can’t see if drought stress alone induced this GPX activity because this treatment is missing ! Morever, we have no evidence that rehydratation could enhanced GR and GPX activity .
Soil mixture I to IV are 4 independant treatment in which initial drought stress is different between them ! Drought stress being different, its impact on plants was different… The interpretation of these results are not correct.
Conclusion :
"Water stress induced damage and rehydration could mitigate water deficit-induced damage in alfalfa root" : same remark !
How author can affirm that water stress induced damage and rehydratation mitigate them ??? They can not differenciate drought stress impact and plant rehydratation impact. Harvesting and analysing plants just after drought treatment is missing ! The authors assume (which is certainly true), that water stress induced damages ... but none of the presented results allowed to demonstrate this without ambiguity.
Author Response
please see the attachment.
Author Response File: Author Response.docx
