Spermidine Pretreatments Mitigate the Effects of Saline Stress by Improving Growth and Saline Excretion in Frankenia pulverulenta

Round 1

Reviewer 1 Report

In this manuscript the authors evaluated the effects of the application of different plant growth regulators on a halophyte. The topic is interesting and the results look promising. I have only minor remarks:

Lines 41-44: xanthophyll cycle...certain genes: actually, all plants show this type of responses, but in halophytes are more pronounced. This point should be better explained.

Why 300 mM NaCl was used? What dictated the choice of this concentration? How many times each PGR was applied in the 10 days? Is the concentration within the brackets the final? Was it received by all plants or each plant?

I would not express the effect of salt and PGR on growth expressing the value in grams of organ per plant. Generally the effects are evaluated on the biomass of the organ (grams).

 

Author Response

I enclosed a word file of responses of reviewer 1

Author Response File: Author Response.pdf

Reviewer 2 Report

In their paper, Bueno and Cordovilla studied the effect of the application of plant growth regulators (PGRs) on Frankenia pulverulenta plants grown hydroponically under salt-free and NaCl stress. They present the results of growth parameters measurements such as fresh weight and dry weight as well as the determination of polyamines contents, proline, ethylene etc. They show a significant induction of saline stress tolerance under Spermidine (Spd) pretreatment of F. pulverulenta plants.  

The manuscript is well written, results are presented clearly, the experimental design is appropriate and the conclusions drawn are sound and logical. All parts of the manuscript (introduction, materials and methods, results and discussion) are well balanced.

In my opinion there are some minor remarks, only:

Since Frankenia pulverulenta is already a plant that resists to stresses especially to saline stress, what is the meaning of applying plant growth regulators for making it more tolerant to stresses? And furthermore, is this application justified or moreover is it a sustainable solution for the cultivation of this halophyte?

Line 92: there is a missing verb in this sentence.

Table 1. Both parts of the table (A and B) have the same headline; “Pretreatments PGRs – Salt” while there is a different description in the caption.

Line 188-189; authors state that significant differences were found only in aerial parts for all PGRs treatments. That is not accurate. There are no statistically significant differences between the control and the treatment with IAA (1μΜ).

Again, in Table 2, the increase in Na from the leaf washing solution expressed per gram of freshly rinsed leaves of F. pulverulenta is significantly higher only after the Spd pretreatment. All the other differences are not significant. Yet authors in line 236-238 refer to both Spd and SA.

 

Author Response

I enclose a word file of responses of reviewer 2

Author Response File: Author Response.pdf

Reviewer 3 Report

Dear authors and editor, in my opinion the manuscript “Spermidine pretreatments mitigate the effects of saline stress by improving growth and saline excretion in Frankenia pulverulenta” can be accepted for publication after minor revisions. The subject of the research is timely, the experiment is properly conducted and the authors gained interesting results. My suggested revisions aim at making the experiment description clearer, especially when describing treatments and results. Please find below my specific comments divided per section.

Abstract

The abstract is clear and concise, please consider the following suggestions:

Line 10 soils salinization and desertification are serious obstacles

Line 14 concentrations up to 200 mM NaCl

Line 15 were tested in hydroponic conditions

Line 22 effective in improving salt tolerance of F. pulverulenta

Introduction

The introduction is complete in the necessary information for well understanding the manuscript research, but paragraphs should be better connected. For instance, the second paragraph starts describing PGRs but is completely unconnected to the previous one. Please consider starting second paragraph somehow like: “Even if well performing also in saline conditions, plants growth regulators (PGRs) might allow halophytes to better cope with environmental stress. PGRs are related…”.

Line 73 please remove “we detected” and change it with “A high content of proline …. was detected”. Also, please add quotation.

Line 82-83 please rephrase, sentence not clear

Materials and methods

This paragraph needs some revisions. Please add in each analysis description paragraph the number of replicas used (now indicated only in 2.3 growth parameters)

Also, please modify the names of treatments which are now very confusing, in particular I would not call the control “(-PGRs)” and I suggest to name the two controls that are in saline and in non saline conditions with clear names indicating it, for instance:

Control non saline conditions (Control)

Control saline conditions (Control + NaCl)

Also, I would add an abbreviation also to Kinetin, for instance (K)

Line 92 I think there is a “collected” missing

Line 106 please add acclimation to what: to the hydroponic conditions? If so, please add it

Line 119 please move trials after growth

Line 163 from Sigma?

Results

This section is the one requiring rewriting. In fact, several sentences here reported do not belong to this section, but to the discussion or materials and methods. Authors can decide to merge the “Results” and the “Discussion” sections, while if you decide to keep it separate then you have to move the following indicated parts.

Line 183 needs quotation and goes in the Discussion section

Line 185 not a result, I suggest to move it in the Materials and methods section

Line 185-187 not a result

Line 190-191 not a result, please move it to the Discussion

Line 214-215 not a result

Line 229-231 not a result

Line 239-242 not a result

Line 252-254 not a result

Line 276-278 not a result, please move in the discussion

Line 292-293 not a result, please move in the discussion

 

Another aspect requiring attention is connected to what already mentioned in the Materials and methods section regarding the names of the treatments. You can see in Table 1 how confusing they are right now.

Table 1: please note that both A. and B. parts of the Table have the same subtitle “Pretreatments PGRs – Salt”, whereas A. , according to the table title, should refer to non-saline conditions  I do not recommend the use of “-“ because confusing, i.e. when you name the Control (-PGRs) with the “-“ you want to state that PGRs are not present but is not that clear. Alike, the “-Salt” is not very communicative in stating whether salt is present or not.

I suggest to call A.  Pretreatments PGRs – non saline  and B. Pretreatments PGRs – saline

And regarding treatments, here and in the Materials and methods section, I would keep treatments names as you did in the Table 1, but without the concentration used (already reported in the Material and methods section), so for instance in A “Control” and in B “Control + NaCl”; in A “IAA” and in B. “IAA + NaCl”, and so on

Table 2 please remove the concentrations of the PGRs and of NaCl from both table and table title

Table 3 and 4 again please fix the mistakes in indicating salt and non salt

Figures

Please check Figure 1: cultivated instead of cultivates

Figure 2: why putting 52 days on the x axis? That’s not a useful information, you already stated that analyses have been made at that time. Please delete it and write below (maybe in vertical?) each bar the relative name (for A: Control¸ IAA; K… For B. Control + NaCl; IAA + NaCl; K + NaCl…). Also, there is no need to indicate in the figure legend the concentration used, you already wrote it in the materials and methods

Discussion

Since several parts are to be moved from the Results to the Discussion section, also this part requires some rewriting. Please also consider the following questions:

Line 327 when you state “increases in NaCl” what do you mean? That M. crystallinum is a sodium includer? As it is written now, it seems that the plant produces NaCl, please rephrase.

Line 334 In general, while glycophyte limit…, most halophytic…

Line 336 when you say toxic ions, are you still talking about Na and Cl or also of others? Please specify

Line 338-339 already said

Line 339-340 I would not mention about the reason behind performing analyses only on leaves: the study is rich in results and can stands on its feet even without root analyses, I suggest to delete the sentence

Line 357-359 please add references. I suggest some but literature is very rich. For desalinating degraded soils and revegetation Hasanuzzaman et al. 2014 Potential use of halophytes to remediate saline soils; Jesus et al. 2015 Phytoremediation of salt-affected soils: a review of processes, applicability, and the impact of climate change. For biosaline agriculture Nikalje et al. 2017 Halophytes in biosaline agriculture: Mechanism, utilization, and value addition; Atzori et al. 2020 Tetragonia tetragonioides (Pallas) Kuntz. as promising salt-tolerant crop in a saline agricultural context; Atzori 2021 The Potential of Edible Halophytes as New Crops in Saline Agriculture The Ice Plant (Mesembryanthemum crystallinum L.) Case Study, Future of Sustainable Agriculture in Saline Environments. CRC Press, 2021. 443-460; Duarte and Caçador 2021 Iberian halophytes as agroecological solutions for degraded lands and biosaline agriculture. For biofuel producing producing crops Christiansen et al. 2021 Increasing the value of Salicornia bigelovii green biomass grown in a desert environment through biorefining

Line 371 is “exist” supposed to be there?

Conclusions

Clear and concise. I only suggest to delete soil contaminants at line 401 and to modify “phytoremediation” with “phytodesalination” at line 413.

 

 

 

 

 

Author Response

I enclose a word file of responses of reviewer 3

Author Response File: Author Response.pdf