Morphological and Physiological Responses of Cymbopogon citratus and Pennisetum alopecuroides to Saline Water Irrigation

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The manuscript titled “Morphological and Physiological Responses of Cymbopogon citratus and Pennisetum alopecuroides to Saline Water Irrigation” provides valuable insights into the salinity tolerance of two ornamental grasses under greenhouse conditions. The experimental approach is well-structured, and the topic is timely given increasing use of reclaimed water in landscape irrigation. However, several methodological and interpretive limitations should be addressed or acknowledged to strengthen the study’s impact and ecological relevance.

1. Salinity Relevance:

   While both species exhibited tolerance to salinity, the highest treatment level (EC 10.0 dS·m⁻¹) exceeds the salinity typically found in reclaimed water, which often averages around EC 3.0 dS·m⁻¹. The ecological relevance of this high treatment level should be discussed more critically, especially in the context of urban landscaping.

2. Experimental Duration:

   The treatment period of 62 days may be too short to capture long-term or chronic effects of salinity on perennial species. Potential impacts such as root deterioration, ion toxicity over time, or seasonal tolerance variation could be missed. Extending the study duration in future work is recommended.

3. Physiological Data Asymmetry:

   Gas exchange and SPAD measurements were conducted only for C. citratus, citing “unsuitable leaf morphology” in P. alopecuroides. However, with methodological adjustments (e.g., smaller cuvette or alternative instrumentation), it is likely that these measurements could still have been obtained. This asymmetry limits the ability to make full physiological comparisons between species and should be more clearly justified or mitigated.

4. Nutrient Imbalance Interpretation:

   While detailed nutrient data are presented (e.g., reductions in Mg²⁺, Ca²⁺, K⁺), the discussion does not clearly link these imbalances to physiological outcomes. For instance, the potential role of Mg deficiency in contributing to chlorosis in C. citratus is mentioned but not sufficiently explored.

5. Discussion Depth:

   The discussion primarily reiterates observed results without sufficiently probing into potential underlying mechanisms. Greater attention should be given to known physiological strategies for salinity tolerance, such as osmotic adjustment, ion compartmentalization, or the synthesis of compatible solutes. References to relevant molecular or biochemical studies would enhance the mechanistic insight of the findings.

6. Suggested Improvements:

   • Include root growth parameters (e.g., root dry weight, root:shoot ratio) in future studies to assess whole-plant responses.

   • Consider extending the duration to assess long-term tolerance and potential recovery mechanisms.

   • Validate the results with field-based experiments using actual reclaimed water.

   • Explore biochemical markers of salt stress (e.g., proline accumulation, antioxidant enzyme activity) for mechanistic clarity.

   • Expand the discussion to address the practical implications and limitations of applying these findings in real-world landscaping scenarios.

 

Overall, the manuscript addresses an important topic and presents meaningful data. Addressing the points above will enhance the scientific rigor, ecological relevance, and applicability of the work.

Author Response

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Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

Firstly, I would like to thank for giving me the opportunity to review the manuscript entitled 'Morphological and Physiological Responses of Cymbopogon citratus and Pennisetum alopecuroides to Saline Water Irrigation'.

This research project addresses a current and relevant horticultural issue: the sensitivity of two ornamental grasses to sodium (Na) and chloride (Cl).

The experimental setup, sampling time and method, and the analysis techniques employed are presented clearly.

Comments on the results section are provided below:

Differences in salt sensitivity were found between the two species studied. The tolerance differences between the two species were indirectly demonstrated; for example, the Na content in P. alupecuroides shoots increased to a lesser extent with increasing doses.

Examining the roots would have provided useful information: For example, it would have revealed how the development of the roots was affected by the treatments and how much Na and Cl were present in the roots. Such measurements would have provided direct evidence of how Na and Cl uptake was distributed between the two organs. Overall, do the two species take up the tested/dosed elements in equal proportions?

Studies on the roots are lacking in this research.

An important mechanism of Na tolerance is the transport of Na from the roots into the shoots of tolerant plants, where it is excreted into the vacuoles.

In order to gain a better understanding of salt tolerance, it would also have been useful to investigate the distribution of sodium (Na) and chloride (Cl) in shoot and root cells, as well as the quantities of these elements present in different cell compartments.

Question regarding the results in Figure 2:

What caused the significant difference in the control results for the two species? Was it due to the larger species having a higher nutrient uptake?

Suggestions for displaying Figures 3 and 4:

The treatment labels should be included for each sub-figure, or written in a note under the final figure.

Question for Section 3.8:

Why was the absolute chlorophyll content not measured instead of the SPAD value? Solvent extraction would be used to measure the chlorophyll content of plants whose leaves cannot be placed on the sensing part of the SPAD instrument. If you have frozen samples, it is possible to carry out retrospective measurements.

General question:

What is the osmotic potential of the salt solutions used? Could they have caused osmotic stress in addition to the toxic effects of sodium and chloride?

Author Response

please see the attachment.

Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

This is a very interesting research, and also very current regardless of the period when it was conducted.

In the Introduction, the issue is well covered, and it provides enough information, while the goal of the research is adequately set.

The Material and method is clear, reproducible and contains the necessary information.

The results are clearly presented, while the discussion could be expanded, in terms of connecting with the results of previous research, avoiding commonly known facts. In addition, the graphical representation of the results is too simple and monotonous.

The conclusion summarizes the research results well.

It is necessary to correct inconsistencies in formatting and remove errors in text writing. Pay attention to citing references in the text, but also in the list.

 

Author Response

please see the attachment.

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

No comments, satisfied with the first revision

Reviewer 2 Report

Comments and Suggestions for Authors

The authors have responded to the comments. The suggested corrections have been accepted and incorporated into the manuscript.

Reviewer 3 Report

Comments and Suggestions for Authors

The authors have made minimal corrections.

There are still some errors in the references, especially in the way the journal names are written. Please make them consistent.