Physiological Investigation of Drought Stress Tolerance of ‘W. Murcott’ Mandarin Grafted onto ‘Carrizo’, ‘Sour Orange’, and ‘Volkameriana’ Rootstocks

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The paper investigates the effects of deficit irrigation on the drought tolerance of ‘W. Murcott’ mandarin grafted onto three different rootstocks: Carrizo citrange, Sour Orange, and Volkameriana. It assesses various physiological parameters like plant height, chlorophyll concentration, net photosynthetic rate, and chlorophyll fluorescence under different drought stress levels. The results suggest that rootstock choice significantly influences drought tolerance, with Sour Orange showing the lowest resilience. However, there are a few suggestions from my side for the authors to improve. 

1) Write full genus name in L11 of abstract. i-e W. Murcott' mandarin grafted onto three rootstocks; sour orange

2) in the abstract section the authors say "Overall, this study underscores the potential of selecting appropriate rootstocks to enhance citrus resilience to drought, crucial for sustainable citrus production in Mediterranean climates" please explain. 

3) In L21 the authors claim that "Citrus fruits are one of the most produced fruit groups in the world". However, Banana is the top most produced fruit in the world. In order to provide a base to the authors claim include a recent citation. 

4) Merge the two columns from L47-61. 

5) L86-88 provide a reference.

6)The results section could benefit from clearer interpretation. While the paper presents statistical findings, it would be helpful to have a more explicit discussion of what these results mean in practical terms. For example, explaining the significance of the differences in chlorophyll content between rootstocks and irrigation treatments would provide more clarity.

7)Why specific rootstocks were selected i-e What makes Carrizo, Sour Orange, and Volkameriana particularly relevant for this study in terms of drought tolerance?

8)The discussion part is poorly written. The authors have mainly focused on the comparison of the current study with the past similar studies. However, it would be helpful to address the limitations of the current study.

9) The authors must revise the figures and tables for good understanding. Specifically the Fig 2 must be revised. 

10) The authors must use consistent terminologies such as "photosynthetic rate" and "net photosynthetic rate" are used interchangeably but could be better defined.

11) Many references are older than 2005. A lot of work has been done specifically on drought stress in the recent years. The authors must avoid references older than 2010. 

 

Comments on the Quality of English Language

The English is good and easy to understand. 

Author Response

Reviewer 1

 

The paper investigates the effects of deficit irrigation on the drought tolerance of ‘W. Murcott’ mandarin grafted onto three different rootstocks: Carrizo citrange, Sour Orange, and Volkameriana. It assesses various physiological parameters like plant height, chlorophyll concentration, net photosynthetic rate, and chlorophyll fluorescence under different drought stress levels. The results suggest that rootstock choice significantly influences drought tolerance, with Sour Orange showing the lowest resilience. However, there are a few suggestions from my side for the authors to improve. 

 

• Write full genus name in L11 of abstract. i-e W. Murcott' mandarin grafted onto three rootstocks; sour orange

1. murcott Afourer (Citrus reticulataBlanco), sour orange (Citrus aurantium L.), volkameriana (Citrus volkameriana V. Ten. Pasq), carrizo citrange (Citrus sinensis 'Washington' sweet orange X Poncirus trifoliata)

 

• in the abstract section the authors say "Overall, this study underscores the potential of selecting appropriate rootstocks to enhance citrus resilience to drought, crucial for sustainable citrus production in Mediterranean climates" please explain. 

The Cukurova region is one of the most important citrus production areas in Turkey. The recent drought stress has been causing problems in citrus production. Due to climate change, the orchards have been irrigated even in the winter months due to insufficient rainfall. Producers are looking for rootstocks that are more tolerant to drought stress. Due to the high quality and marketability of W. Murcott mandarin, the drought stress tolerance of sour orange, volkameriana and carrizo citrange, which are widely used in Cukurova, was examined to determine the most drought tolerant rootstock.

 

3) In L21 the authors claim that "Citrus fruits are one of the most produced fruit groups in the world". However, Banana is the top most produced fruit in the world. In order to provide a base to the authors claim include a recent citation. 

This situation is changed in the MS file as follows; Citrus production quantity is one of the highest amount among the other fruits groups in the world.

 

4) Merge the two columns from L47-61. 

Has been merged

 

5) L86-88 provide a reference.

Citation has been provided

 

6)The results section could benefit from clearer interpretation. While the paper presents statistical findings, it would be helpful to have a more explicit discussion of what these results mean in practical terms. For example, explaining the significance of the differences in chlorophyll content between rootstocks and irrigation treatments would provide more clarity.

More explicit discussions of the results in terms of practices have been provided.

 

7)Why specific rootstocks were selected i-e What makes Carrizo, Sour Orange, and Volkameriana particularly relevant for this study in terms of drought tolerance?

The soils of Çukurova are quite calcareous. Producers use sour orange rootstock due to the lime problem. However, due to tristeza, Carrizo citrange has become the second most used rootstock in the region. In recent years, the volkameriana rootstock has become widespread due to the increase in fruit size. In summary, since these three rootstocks are most commonly used in the Çukurova region, a comparison in terms of drought stress has arisen.

 

8)The discussion part is poorly written. The authors have mainly focused on the comparison of the current study with the past similar studies. However, it would be helpful to address the limitations of the current study.

The discussion section has been improved according to the reviewer’s suggestions.

 

9) The authors must revise the figures and tables for good understanding. Specifically the Fig 2 must be revised. 

Has been improved.

 

10) The authors must use consistent terminologies such as "photosynthetic rate" and "net photosynthetic rate" are used interchangeably but could be better defined.

Have been changed as "photosynthetic rate" in the entire MS.

 

11) Many references are older than 2005. A lot of work has been done specifically on drought stress in the recent years. The authors must avoid references older than 2010. 

Recent research and studies have been supplied and cited in the MS.

 

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

The current manuscript tried to determine the drought tolerance of three different root stocks with a concentration on photosystem. Additional chlorophyll fluorescence parameters should be provided. The data of net photosynthetic rate should be double-checked. More data such as yield might be provided to further improve the experiment. After careful evaluation, a decision of “reconsider after drastic revision” was reached. The authors are recommended to revise the manuscript properly based on the following concerns raised by the reviewer.

1. The title was not accurate. The current study was focused on the physiological mechanism especially on photosystem, the present title seems lack of innovation.
2. Line 86-91: This paragraph was so confused, the authors should clarify the internal logical relationships between drought and salinity stress. Why salinity resulted in drought? The authors should concentrate on drought stress, not salinity in the current study.
3. In materials and methods section, the year and place the experiment was carried out should be added. Were the seeds sterilized before sowing? Moreover, literatures concerning the physiological methods should be added.
4. Line 134-142: The parameters of the leaf chamber in Li-6400 including CO₂ concentration, photosynthetic photon flux density, leaf temperature and relative air humidity should be provided.
5. Line 143-144: The instrument model of the portable fluorimeter should be provided as well as the parameter setup in the fluorimeter. It is highly recommended that other parameters including Fv/Fm, NPQ, qP, qN, ΦPSII, ETR et al. are also marker indicators of leaf chlorophyll fluorescence, which should be also determined. Fv’/Fm’ was not sufficient to support the chlorophyll fluorescence data.
6. In Table 1, apart from ANOVA, the original data of these physiological parameters should also be provided.
7. In Table 4, the data of Pn and Gs were so confused. Usually the values of Pn should be greater than 10. Moreover, the Gs data were so small, which seems that the stomata were closed. Usually the values of Gs should be greater than 100 mmol m^-2s^-1.
8. Figure 2 was a useless figure because in most cases, literatures have advocated that strong relationships exist between “Pn and chlorophyll content” and “Gs and Tr”. These results are largely known by the readership.
9. The whole experiment lacks of yield data. It is suggested to provide the yield data of each treatment. To the best of the reviewer’s knowledge, the physiological data presented in the current investigation were not sufficient to support the hypothesis of the work. In some cases, higher Pn and chlorophyll content might not result in higher production. Under drought stress, higher plant growth rate might induce the imbalance between the vegetable growth and the reproductive growth. Conversely, some more resistant plants will close their stoma and reduce photosynthetic rate to cope with the severe environment. The authors should consider the above information provided by the reviewer and revise their discussion section accordingly.

Author Response

Reviewer 2

The current manuscript tried to determine the drought tolerance of three different root stocks with a concentration on photosystem. Additional chlorophyll fluorescence parameters should be provided. The data of net photosynthetic rate should be double-checked. More data such as yield might be provided to further improve the experiment. After careful evaluation, a decision of “reconsider after drastic revision” was reached. The authors are recommended to revise the manuscript properly based on the following concerns raised by the reviewer.

1. The title was not accurate. The current study was focused on the physiological mechanism especially on photosystem, the present title seems lack of innovation.

The title of the MS has been changed as; Physiological Investigation of Drought Stress Tolerance of ‘W. Murcott’ Mandarin Grafted on to ‘Carrizo’, ‘Sour orange’ and ‘Volkameriana’ Rootstocks

 

1. Line 86-91: This paragraph was so confused, the authors should clarify the internal logical relationships between drought and salinity stress. Why salinity resulted in drought? The authors should concentrate on drought stress, not salinity in the current study.

In line 86-91, the situation has been improved as follows; “The Cukurova region is one of the most important citrus production areas in Turkey. The recent drought stress has been causing problems in citrus production. Due to climate change, the orchards have been irrigated even in the winter months due to insufficient rainfall. Producers are looking for rootstocks that are more tolerant to drought stress” regarding reviewer’s suggestions.

 

1. In materials and methods section, the year and place the experiment was carried out should be added. Were the seeds sterilized before sowing? Moreover, literatures concerning the physiological methods should be added.

Suggestions have been added in the manuscript file.

 

1. Line 134-142: The parameters of the leaf chamber in Li-6400 including CO₂ concentration, photosynthetic photon flux density, leaf temperature and relative air humidity should be provided.

During the gas exchange measurements, leaf temperature ranged between 24 and 26^oC and the relative humidity was 50% where PFD was detected as 800-850 μmol m^-2 s^-1.

 

1. Line 143-144: The instrument model of the portable fluorimeter should be provided as well as the parameter setup in the fluorimeter. It is highly recommended that other parameters including Fv/Fm, NPQ, qP, qN, ΦPSII, ETR et al. are also marker indicators of leaf chlorophyll fluorescence, which should be also determined. Fv’/Fm’ was not sufficient to support the chlorophyll fluorescence data.

QY is a measure of the Photosystem II efficiency. In a dark-adapted leaf this is equivalent to Fv/Fm. In a light-adapted leaf it is equivalent to Fv’/Fm’. Our measurements were recorded in light-adapted stage of the leaves. We were not able to measure dark adapted stage of QY. Therefore Fv’/Fm’ measurement data were presented in this work.

 

In Table 1, apart from ANOVA, the original data of these physiological parameters should also be provided.

Table 1 represents the results of a two-way anova conducted to results all the investigated variables in this study. So, data represents F values according to anova conducted. Following Table 2, 3 and 4 represents the original mean data related to the investigated variables.

1. In Table 4, the data of Pn and Gs were so confused. Usually the values of Pn should be greater than 10. Moreover, the Gs data were so small, which seems that the stomata were closed. Usually the values of Gs should be greater than 100 mmol m^-2s^-1.

Citrus fruits are evergreen plant species that do not shed their leaves. Therefore, unlike temperate climate fruit species, they do not photosynthesize in a certain season of the year but throughout the year. Therefore, their photosynthesis rates are quite low compared to other fruit species (peach, apple, apricot, cherry).Figure 2 was a useless figure because in most cases, literatures have advocated that strong relationships exist between “Pn and chlorophyll content” and “Gs and Tr”. These results are largely known by the readership.

 

1. The whole experiment lacks of yield data. It is suggested to provide the yield data of each treatment. To the best of the reviewer’s knowledge, the physiological data presented in the current investigation were not sufficient to support the hypothesis of the work. In some cases, higher Pn and chlorophyll content might not result in higher production. Under drought stress, higher plant growth rate might induce the imbalance between the vegetable growth and the reproductive growth. Conversely, some more resistant plants will close their stoma and reduce photosynthetic rate to cope with the severe environment. The authors should consider the above information provided by the reviewer and revise their discussion section accordingly.

The fact that the sour orange is better than the other two rootstocks in terms of chlorophyll and Fv/Fm requires the stress period to be extended and its performance to be seen. Even though plant development is lower than the other two rootstocks, the high chlorophyll and Fv/Fm levels were found to be promising in terms of drought tolerance. Perhaps the fact that the plant grafted onto the orange rootstock does not grow too much is due to its self-protection mechanism against water deficiency due to the decrease in stomatal conductance under water deficit irrigation.

 

Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

Please see the attachement

Comments for author File: Comments.pdf

Comments on the Quality of English Language

Some awkward phrases were found.

Author Response

Reviewer 3

 

Line 16, Abstract: please include findings concerning rootstocks with the best growth parameters.

Abstract section has been improved.

 

Line 20-21, Abstract, IMPORTANT: the phrase “emphasizing the role … on citrus productivity” is not true, there was no evidence from THIS experiment that chlorophyll protects from deficit irrigation consequences.

Abstract section has been changed.

 

Lines 35-36, Introduction:  “Citrus fruit... is quality high” - awkward phrasing.

Sentence has been rephrased

 

Lines 44, Introduction:  “Gamir et al. 2010” is lacking in References.

Change as; Rodriguez-Gamir et al., 2010.

 

Line 107, M&M: please specify properly three levels of drought stress.

Changed as; The plants were subjected to three levels of control, 50% and 40 % drought stress.

 

Line 117, M&M: “Klute 1986” is lacking in References.

Klute, A. (1986) Methods of soil analysis. Part 1: Physical and mineralogical methods. 2nd Edition, American Society of Agronomy and Soil Science Society of America, Madison, USA. Has been added to references.

 

Line 119, M&M: please describe in details how fresh weight was determined at the beginning of the experiment. Was this determination performed on the plants included in the experiment or on the additional plants which were removed afterwards?

At the beginning of the experiment, all plants were labeled and weighed, and at the end of the experiment, the same plants were measured and their growth was calculated.

 

Lines 127-128, M&M: not understandable.

After leaf chlorophyll concentration and leaf gas exchange measurements, the plants were harvested for dry mass (DM) measurements for this purpose, samples were dried at 72 °C for 48 h using a thermo ventilated oven for further plant nutrition concentration analyses.

 

Lines 138, 143, M&M: please specify the producer of these devices.

The producers of these devices were supplied

 

Lines 143-144, M&M: please specify the device for chl fl measurements and the producer.

The producers of these devices were supplied

 

Lines 179-180, Results: please check this phrase, what about 40% irrigation?

The highest fresh weight was determined in control plants with 186.40 g, followed by 50% deficit irrigation treatment (153.73 g), whereas the lowest fresh weight was recorded in 40% plants as 153.73 g.

 

Figure 1, Results, please use PN or A for assimilation rate consistently throughout the whole manuscript.

Throughout the whole manuscript PN used as abbreviation for photosynthetic rate

 

Line 276-278, Discussion: please rewrite.

Discussion section has been rewritten.

 

Line 297-301, Discussion: please be consistent when describing or referring to Fv'/Fm'.

Discussion section has been rewritten.

 

Line 303-308, Discussion: please rewrite.

Discussion section has been rewritten.

 

 Line 313, Discussion: as the results of rootstock comparison in terms of gas exchange are different from these concerning growth parameters, please discuss the importance of these results in the context of the threat of drought.

Rewritten according to reviewer’s suggestions

Conclusions: should be rewritten. They should contain the summarised results of the Authors' research. Which rootstock(s) seems to be the most promising in the face of the threat of drought?

 

References: please provide English versions of the titles in the references in lines: 365, 393, 398, 400.

Cerçi S (2012). Effects of Drought Stress on Some Photosynthetic Parameters and Plant Nutrient Concentrations in Different Citrus Rootstocks. Çukurova University, Institute of Science, Master Thesis. p83s.

Kaçar B, Katkat AV, Öztürk Ş (2002). Plant Physiology. Uludag University Strengthening Foundation Publication No: 198, Vipaş Publication No:74., Bursa.

Kuşvuran Ş, Daşgan HY, Abak K (2008). Responses of Different Okra Genotypes to Drought Stress. VII. Vegetable Farming Symposium, 26-29 August, Yalova, Türkiye, 329-333.

Kutlu I (2010). Drought Stress in Cereals. Turkish Journal of Scientific Reviews 3(1): 35-41.

 

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

After going through the revised article. I am satisfied with the changes made by the authors and hereby suggest that now the paper can be accepted.

Reviewer 2 Report

Comments and Suggestions for Authors

During the whole manuscript, Pn, PN, P_N, and P_N should be unified.

Line 145:"H2O" should be revised to "H₂O". 

Line 455: "CO2" should be revised to "CO₂".