Study on Regulation Mechanism of Tomato Root Growth in Greenhouse under Cycle Aerated Subsurface Drip Irrigation
, Peng Zhang 1,†, Yunpeng Deng 1, Chitao Sun 1, Xiaoxu Tian 1, Bingcheng Si 2, Bo Li 3, Xiaohong Guo 2, Fusheng Liu 1,* and Zhenhua Zhang 2,*
Round 1
Reviewer 1 Report
I find the article very interesting and well-written. I suggest only minor technical corrections, otherwise, it can be published in the present form.
Author Response
Dear Editor, Dear reviewers
We would like to thank you very much for your valuable comments and good suggestions that greatly helped to improve our manuscript. Thank you very much for your time and efforts. Based on the comments and suggestions, we have revised the manuscript accordingly. And we have uploaded a version of the revised manuscript with all the changes highlighted by using the track changes mode in MS word and a version of the revised manuscript with all changes accepted.
Appended to this letter is our point by point response to the comments raised by the reviewers. The comments are reproduced and our responses are given directly afterward in a different color (red). The line number in Reply refers to the revised manuscript with track changes.
Point 1: I find the article very interesting and well-written. I suggest only minor technical corrections, otherwise, it can be published in the present form.
Response 1: Thank you for the kind advice.
According to the reviewer’s good advice, We have corrected including the font, italics, superscript, and reference. Please see the manuscript.
We appreciate for Editor and Reviewers' warm work earnestly, and hope that the correction will meet with approval.
Once again, thank you and all the reviewers for the advice and consideration.
Sincerely,
Author Response File: 
Author Response.pdf
Reviewer 2 Report
The manuscript with the title “Study on Regulation Mechanism of Tomato Root Growth in Greenhouse Under Cycle Aerated Subsurface Drip Irrigation”, presents the results regarding the effect of underground drip irrigation at three levels of aeration on tomato root traits and transcriptome, with emphasis on mechanisms with physiological implications. The authors concluded that aeration irrigation may promote the growth and development of roots by auxin regulation.
Introduction
First paragraph - Please consider that there is a wide range of tolerance to lack of oxygen/low levels of oxygen in rhizosphere depending on the species. Root asphyxia can occur in tomato, since it does not have special adaptations, but some plants (e.g. adapted to aquatic environments) have their roots submerged. Therefore, I think is important do not speak in general terms here because it is not a fact universally available for all plants, and there is a wide range of tolerance among plants that should be delimited. It might even be interesting to briefly mention that requirements of oxygen levels in rhizosphere of plants is an evolutionary trait found in close relationship with the environment to which these plants have adapted (native environments).
Root traits are also found in relationship with functional roles and in the since the root ensures the main influx of nutrients and water – therefore with great influence on the yield.
Line 44 - I would suggest to rephrase from “A lack of oxygen leads to root respiratory disorder and physiological dysfunction, or even death” to “Low levels or lack of oxygen in rhizosphere of plants can have a more or less detrimental effect on plant fitness, depending on species. In tomato, this can lead to root asphyxia, that impairs metabolic functions and causes reversible or irreversible damage to plants, potentially leading to plant death.”
Lines 172-175 should be at the Material and Method Section, describing the experimental variants.
Throughout the manuscript use a single text font. In figures use a single type of font as well.
Best regards.
Author Response
Response to Reviewer 2 Comments
Dear Editor, Dear reviewers
We would like to thank you very much for your valuable comments and good suggestions that greatly helped to improve our manuscript. Thank you very much for your time and efforts. Based on the comments and suggestions, we have revised the manuscript accordingly. And we have uploaded a version of the revised manuscript with all the changes highlighted by using the track changes mode in MS word and a version of the revised manuscript with all changes accepted.
Appended to this letter is our point by point response to the comments raised by the reviewers. The comments are reproduced and our responses are given directly afterward in a different color (red). The line number in Reply refers to the revised manuscript with track changes.
Point 1: Introduction
First paragraph - Please consider that there is a wide range of tolerance to lack of oxygen/low levels of oxygen in rhizosphere depending on the species. Root asphyxia can occur in tomato, since it does not have special adaptations, but some plants (e.g. adapted to aquatic environments) have their roots submerged. Therefore, I think is important do not speak in general terms here because it is not a fact universally available for all plants, and there is a wide range of tolerance among plants that should be delimited. It might even be interesting to briefly mention that requirements of oxygen levels in rhizosphere of plants is an evolutionary trait found in close relationship with the environment to which these plants have adapted (native environments).
Response 1: Thank you for the kind advice.
According to the reviewer’s good advice, We have corrected. Please see Line39-49.
“In the whole life, plants were subjected to abiotic stresses such as flood, freezing, drought and salt stress. For most vegetables and fruit trees, flood seriously affected the growth and development of plants, which made the water around the soil saturated and extrudes the oxygen in the soil, resulting in root hypoxia. O2 and CO2 are the main gas components of the plant rhizosphere, and their concentrations play an important role in root metabolism and soil microbial activity (Lu, 2006). Low levels or lack of oxygen in rhizosphere of plants can have a more or less detrimental effect on plant fitness, depending on species. In tomato, root asphyxia will impair metabolic functions and causes reversible or irreversible damage to plants, potentially leading to death. ”
Point 2: Root traits are also found in relationship with functional roles and in the since the root ensures the main influx of nutrients and water – therefore with great influence on the yield.
Line 44 - I would suggest to rephrase from “A lack of oxygen leads to root respiratory disorder and physiological dysfunction, or even death” to “Low levels or lack of oxygen in rhizosphere of plants can have a more or less detrimental effect on plant fitness, depending on species. In tomato, this can lead to root asphyxia, that impairs metabolic functions and causes reversible or irreversible damage to plants, potentially leading to plant death.”
Response 2: Thank you for the kind advice. The root system is an important organ for normal plant growth and development. Its main function is to obtain nutrients and water from soil for aboveground growth and development. It plays a key role in the plant yield. In this study, the aeration irrigation significantly promoted tomato root development, and The aeration treatment had significant effects on the overground organ development of tomato. At the same fertilization level, the plant height, stem diameter, Chlorophyll content, dry matter (stem, leaves, fruit) under the aeration irrigation were significantly higher than that of CK respectively, with the highest was HAI treatment, followed by MAI and LAI treatments (Supplementary Table 1, 2, and 3). Please see line 259-264 and Supplementary Table 1, 2, 3.
Supplementary Table 1 Impacts of cycle aerated subsurface drip irrigation on plant height and stem diameter in Tomato
|
Treatment |
Height/cm |
Stem diameter/cm |
|
HAI |
212.5±32.76 |
1.480±0.080 |
|
MAI |
187.17±21.91 |
1.466±0.065 |
|
LAI |
186.67±20.34 |
1.455±0.116 |
|
CK |
177.17±26.72 |
1.421±0.143 |
Supplementary table 2 Effects of cycle aerated subsurface drip irrigation on photosynthetic pigment content of leaves
|
Treatment |
Chlorophyll a content (mg·g-1) |
Chlorophyll b content (mg·g-1) |
Total chlorophyll content (mg·g-1) |
|
HAI |
0.83±0.013 |
0.34±0.077 |
1.17±0.069 |
|
MAI |
0.72±0.018 |
0.26±0.020b |
0.98±0.031 |
|
LAI |
0.66±0.044 |
0.24±0.020 |
0.90±0.063 |
|
CK |
0.60±0.093 |
0.22±0.029 |
0.81±0.123 |
Supplementary table 3 Impacts of cycle aerated subsurface drip irrigation on plant dry matter in tomato
|
Treatments |
Stems dry matter accumulation (g/ plant) |
Leaves dry matter accumulation (g/ plant) |
Fruit dry matter accumulation (g/ plant) |
Total dry matter accumulation (g/ plant) |
|
HAI |
39.38±11.43 |
44.56±7.45 |
3.56±1.29 |
89.37±20.03 |
|
MAI |
36.39±1.33 |
36.82±4.88b |
4.34±0.32 |
79.20±13.74 |
|
LAI |
30.70±5.88 |
38.10±5.46 |
2.57±0.19 |
72.99±22.17 |
|
CK |
26.41±5.39 |
37.58±4.59 |
2.22±0.17 |
67.88±15.60 |
Point 3: Line 44 - I would suggest to rephrase from “A lack of oxygen leads to root respiratory disorder and physiological dysfunction, or even death” to “Low levels or lack of oxygen in rhizosphere of plants can have a more or less detrimental effect on plant fitness, depending on species. In tomato, this can lead to root asphyxia, that impairs metabolic functions and causes reversible or irreversible damage to plants, potentially leading to plant death.”
Response 3: Thanks for your advice. We have corrected. Please see Line 45-50，“Low levels or lack of oxygen in rhizosphere of plants can have a more or less detrimental effect on plant fitness, depending on species. In tomato, root asphyxia will impair metabolic functions and causes reversible or irreversible damage to plants, potentially leading to death.”
Point 4：Lines 172-175 should be at the Material and Method Section, describing the experimental variants.
Response 4: Thanks for your advice. We have corrected. Please see Line159-179.
Point 5： Throughout the manuscript use a single text font. In figures use a single type of font as well.
Response 5: Thanks for your advice. We have corrected. Please see the manuscript.
We appreciate for Editor and Reviewers' warm work earnestly, and hope that the correction will meet with approval.
Once again, thank you and all the reviewers for the advice and consideration.
Sincerely,
Reviewer 3 Report
Serious climate changes are taking place in the world due to floods and as a result negatively affects the agricultural sector. Because of the floods plants suffer from a lack of oxygen. And the consequences of this phenomenon as well as the mechanisms of getting out of this state (hypoxia) are relevant for studying and not only for solving problems of an agriculture (i.e. of an applied nature), but also because of the fundamental nature of these studies. This is what the authors of the article tried to do.
Is watering not related to promoting root growth through auxin regulation? What is the novelty?
The new data obtained demands "maximizing".
Updating of references to sources is also required (less than 30% in the last 10 years).
The design and description of the methods require refinement, disclosure and specification.
How was the hormone content measured (methodology, references, procedure), is it written differently in different places (GC-MS is indicated in the abstract and the results, LC-MS/MS is mentioned in the methods)? This also applies to other methods.
There is no schematic diagram of the aeration device. There is no data on dissolved oxygen concentrations for each variant.
Have any fertilizers been used for the treatments?
Why was the aboveground part of the plants not evaluated? Chlorophyll content?
Growth characteristics??
Remarks:
Line 41: Replace O2 with O2 (the number "two" must be in lowercase)
Line 41: Replace CO2 with CO2 (the number "two" must be in lowercase)
Line 43: Replace (Lu 2006) to (Lu, 2006)
Line 115, 128: Replace m2 to m2 (the number "two" must be in lowercase)
Line 127-137: The aeration installation is poorly described. It is not specified how this
is done and how the degree of oxygen saturation is controlled.
146-149: Fix the font
152, 154: no references to the software used in the work
237-257, 294-...: adjust font.
Author Response
Response to Reviewer 3 Comments
Dear Editor, Dear reviewers
We would like to thank you very much for your valuable comments and good suggestions that greatly helped to improve our manuscript. Thank you very much for your time and efforts. Based on the comments and suggestions, we have revised the manuscript accordingly. And we have uploaded a version of the revised manuscript with all the changes highlighted by using the track changes mode in MS word and a version of the revised manuscript with all changes accepted.
Appended to this letter is our point by point response to the comments raised by the reviewers. The comments are reproduced and our responses are given directly afterward in a different color (red). The line number in Reply refers to the revised manuscript with track changes.
Reviewer 3
Point 1: Serious climate changes are taking place in the world due to floods and as a result negatively affects the agricultural sector. Because of the floods plants suffer from a lack of oxygen. And the consequences of this phenomenon as well as the mechanisms of getting out of this state (hypoxia) are relevant for studying and not only for solving problems of an agriculture (i.e. of an applied nature), but also because of the fundamental nature of these studies. This is what the authors of the article tried to do.
Response 1: Thanks for your advice. For most vegetables and fruit trees, flood seriously affected the growth and development of plants, which made the water around the soil saturated and extrudes the oxygen in the soil, resulting in root hypoxia. In tomato, root asphyxia will impair metabolic functions and causes reversible or irreversible damage to plants, potentially leading to death. To solve this problem, tomato under underground drip irrigation was irrigated with oxygen in this study. We found that the aeration irrigation significantly promoted root development including total root length, total surface area, total volume, and root activity. Moreover, aeration irrigation promoted the increase of auxin content in plant root, and the transcript of the corresponding synthetic genes were also up-regulated significantly. This study was helpful to understand the regulatory mechanism of aerobic irrigation exerts on root growth from perspective of hormone. Please see Line 39-49 and 108-116.
Point 2: Is watering not related to promoting root growth through auxin regulation? What is the novelty?
Response 2: Thanks for your advice. The root system is an important organ for normal plant growth and development. The internal factors affecting plant root development include organic nutrition and endogenous hormones, while the most significant external factors are soil permeability and temperature, soil moisture, soil nutrient availability, soil pH value, etc. In this study, tomato under underground drip irrigation was irrigated with oxygen under the same fertilization amount and irrigation amount. We found that the aeration irrigation significantly promoted root development including total root length, total surface area, total volume, and root activity compared with no oxygen irrigation. Moreover, aeration irrigation promoted the increase of auxin content in plant root, and the transcript of the corresponding synthetic genes were also up-regulated significantly. This study was helpful to understand the regulatory mechanism of aerobic irrigation exerts on root growth from perspective of hormone. So, we concluded that aeration irrigation can promote root growth and development by regulating auxin synthesis. Please see Line108-116 and 425-435.
Point 3: Updating of references to sources is also required (less than 30% in the last 10 years).
Response 3: Thanks for your advice. We supplemented the reference for the last 10 years. Please see reference.
Abuarab M., Mostafa E., Ibrahim M. 2013. Effect of air injection under subsurface drip irrigation on yield and water use efficiency of corn in a sandy clay loam soil. Journal of Advanced Research, 4: 493-499. https://doi.org/10.1016/j.jare.2012.08.009
Bagatur T. 2014. Evaluation of plant growth with aerated irrigation water using venturi pipe part. Arabian Journal for Science and Engineering, 39: 2525-2533. https://www.researchgate.net/publication/271950895
Chen H., Hou H., Wang X., Zhu Y., Qaisar S., Wang Y., Cai H. 2018. The effects of aeration and irrigation regimes on soil CO2 and N2O emissions in a greenhouse tomato production system. Journal of Integrative Agriculture 17(2): 449-460 https://doi.org/10.1016/S2095-3119(17)61761-1
Lei H., Bhattarai S., Balsys R., Midmore D., Holmes T., Zimmerman W. 2016. Temporal and spatial dimension of dissolved oxygen saturation with fluidic oscillator and Mazzei air injector in soil-less irrigation systems. Irrigation Science, 34: 421-430. https://www.researchgate.net/publication/304924042
Pan R., Jiang W., Wang Q., Xu L., Shabala S., Zhang W. 2019. Differential response of growth and photosynthesis in diverse cotton genotypes under hypoxia stress. Photosynthetica, 57(3): 772-779. https://www.researchgate.net/publication/333796427
Pendergast L., Bhattarai S., Midmore D. 2014. Benefits of oxygation of subsurface drip-irrigation water for cotton in a Vertosol. Crop and Pasture Science, 64: 1171-1181. https://doi.org/10.1071/CP13348
Peng Y., Zhou Z., Tong R., Hu X., Du K. 2017. Anatomy and ultrastructure adaptations to soil flooding of two full-sib poplar clones differing in flood-tolerance. Flora, 233: 90-98. https://doi.org/10.1016/j.flora.2017.05.014
Ren B., Zhang J., Dong S., Liu P., Zhao B. 2016. Root and shoot responses of summer maize to waterlogging at different stages. Agronomy Journal, 108(3). https://doi.org/10.2134/agronj2015.0547
Zheng X., Zhou J., Tan D., Wang N., Wang L., Shan D., Kong J. 2017. Melatonin improves waterlogging tolerance of Malus baccata (Linn) borkh seedlings by maintaining aerobic respiration, photosynthesis and ROS migration. Frontiers in plant science, 8: 483. https://pubmed.ncbi.nlm.nih.gov/28424730/
Zhu Y., Cai H., Song L., Wang X., Shang Z., Sun Y. 2020. Aerated irrigation of different irrigation levels and subsurface dripper depths affects fruit yield, quality and water use efficiency of greenhouse tomato. Sustainability. 12:2703. https://doi.org/10.3390/su12072703
Point 4: The design and description of the methods require refinement, disclosure and specification.
Response 4: Thanks for your advice. We supplemented the methods. Please see Line 132-133 and 159-178.
Point 5: How was the hormone content measured (methodology, references, procedure), is it written differently in different places (GC-MS is indicated in the abstract and the results, LC-MS/MS is mentioned in the methods)? This also applies to other methods.
Response 5: Thanks for your advice. The hormone determination was measured using the Liquid Chromatograph Mass Spectrometer (LC-MS), not GC-MS. We have corrected. Please see Line 207-210.
Point 6: There is no schematic diagram of the aeration device. There is no data on dissolved oxygen concentrations for each variant.
Response 6: Thanks for your advice. We supplemented the information about the cycle aeration device. Please see Line135-179.
“The cycle aeration device is used for aeration, as shown in Figure 1 (patent No.: CN103314697A). In this experiment, three pressure levels of 0.05MPa, 0.1MPa and 0.15MPa are set as three aeration levels: high aeration rate (H), medium aeration rate (M) and low aeration rate (L) with the aeration ratio 17.25% (H), 14.58% (M) and 10.79% (L), respectively (the aeration ratio is the ratio of air volume to liquid volume) under the temperature of irrigation water of 18 ℃. In the test, the maximum pressure of drip irrigation pipe used is 0.2MPa. The irrigation water is circulated for 15 minutes for aeration treatment, and then the water and gas mixture is transported to each test area through the underground drip irrigation belt.”
The aeration installation is showed in Fig.1.
Figure 1. The cycle aeration device and schematic diagram. 1: Air compressor, 2: Pressure safety valve, 3: Water monitor, 4: Pressure control valve, 5: High water level, 6: Lower water level,7: Reference level, 8: Internal circulation orifice, 9: Air circulation port , 10: Water inlet, 11: Booster pump, 12: Air jet generator, 13: Check valve, 14: Inlet solenoid valve, 15: Water inlet, 16: Drain outlet, 17: Pressure water tank, 18: Water outlet solenoid valve, 19: Low level water outlet, 20: Deflector, 21: Temperature transmitter, 22: Dissolved oxygen controller, 23: Water outlet solenoid valve, 24: High level water outlet, 25: Fertilizer applicator, 26: Check valve.
Point 7: Have any fertilizers been used for the treatments?
Response 7: Thanks for your advice. We supplemented the data about the fertilization level. In this experiment, for aeration irrigation or CK treatment, the fertilization level is N 180 kg/hm2 - P2O 590 kg/hm2- K2O 112.5 kg/hm2. Please see Line 132-133.
“In this experiment, the fertilization level is N 180 kg/hm2 - P2O 590 kg/hm2- K2O 112.5 kg/hm2”.
Point 8: Why was the aboveground part of the plants not evaluated? Chlorophyll content?
Growth characteristics??
Response 8: Thanks for your advice. The root system is an important organ for normal plant growth and development. Its main function is to obtain nutrients and water from soil for aboveground growth and development. It plays a key role in the plant yield. In this study, the aeration irrigation significantly promoted tomato root development, and The aeration treatment had significant effects on the overground organ development of tomato. At the same fertilization level, the plant height, stem diameter, Chlorophyll content, dry matter (stem, leaves, fruit) under the aeration irrigation were significantly higher than that of CK respectively, with the highest was HAI treatment, followed by MAI and LAI treatments (Supplementary Table 1, 2, and 3). Please see Line 259-264. Supplementary Table 1, 2, 3.
Supplementary Table 1 Impacts of cycle aerated subsurface drip irrigation on plant height and stem diameter in Tomato
|
Treatment |
Height/cm |
Stem diameter/cm |
|
HAI |
212.5±32.76 |
1.480±0.080 |
|
MAI |
187.17±21.91 |
1.466±0.065 |
|
LAI |
186.67±20.34 |
1.455±0.116 |
|
CK |
177.17±26.72 |
1.421±0.143 |
Supplementary table 2 Effects of cycle aerated subsurface drip irrigation on photosynthetic pigment content of leaves
|
Treatment |
Chlorophyll a content (mg·g-1) |
Chlorophyll b content (mg·g-1) |
Total chlorophyll content (mg·g-1) |
|
HAI |
0.83±0.013 |
0.34±0.077 |
1.17±0.069 |
|
MAI |
0.72±0.018 |
0.26±0.020b |
0.98±0.031 |
|
LAI |
0.66±0.044 |
0.24±0.020 |
0.90±0.063 |
|
CK |
0.60±0.093 |
0.22±0.029 |
0.81±0.123 |
Supplementary table 3 Impacts of cycle aerated subsurface drip irrigation on plant dry matter in tomato
|
Treatments |
Stems dry matter accumulation (g/ plant) |
Leaves dry matter accumulation (g/ plant) |
Fruit dry matter accumulation (g/ plant) |
Total dry matter accumulation (g/ plant) |
|
HAI |
39.38±11.43 |
44.56±7.45 |
3.56±1.29 |
89.37±20.03 |
|
MAI |
36.39±1.33 |
36.82±4.88b |
4.34±0.32 |
79.20±13.74 |
|
LAI |
30.70±5.88 |
38.10±5.46 |
2.57±0.19 |
72.99±22.17 |
|
CK |
26.41±5.39 |
37.58±4.59 |
2.22±0.17 |
67.88±15.60 |
Point 9: Remarks:
9 .1 Line 41: Replace O2 with O2 (the number "two" must be in lowercase)
Response 9.1: Thanks for your advice. We have corrected. Please see Line 39-49.
9 .2 Line 41: Replace CO2 with CO2 (the number "two" must be in lowercase)
Response 9.2: Thanks for your advice. We have corrected. Please see Line 39-49
9 .3 Line 43: Replace (Lu 2006) to (Lu, 2006)
Response 9.3: Thanks for your advice. We have corrected. Please see Line 45.
9 .4 Line 115, 128: Replace m2 to m2 (the number "two" must be in lowercase)
Response 9.4: Thanks for your advice. We have corrected. Please see Line126-153 （方法2.1）
9 .5 Line 127-137: The aeration installation is poorly described. It is not specified how thisis done and how the degree of oxygen saturation is controlled.
Response 9.5: Thanks for your advice. We supplemented the data. Please see Line159-168.
“In this experiment, three pressure levels of 0.05MPa, 0.1MPa and 0.15MPa are set as three aeration levels: high aeration rate (H), medium aeration rate (M) and low aeration rate (L) with the aeration ratio 17.25% (H), 14.58% (M) and 10.79% (L), respectively (the aeration ratio is the ratio of air volume to liquid volume) under the temperature of irrigation water of 18 ℃. In the test, the maximum pressure of drip irrigation pipe used is 0.2MPa. The irrigation water is circulated for 15 minutes for aeration treatment, and then the water and gas mixture is transported to each test area through the underground drip irrigation belt.”
The aeration installation is showed in Fig.1.
Figure 1. The cycle aeration device and schematic diagram. 1: Air compressor, 2: Pressure safety valve, 3: Water monitor, 4: Pressure control valve, 5: High water level, 6: Lower water level,7: Reference level, 8: Internal circulation orifice, 9: Air circulation port , 10: Water inlet, 11: Booster pump, 12: Air jet generator, 13: Check valve, 14: Inlet solenoid valve, 15: Water inlet, 16: Drain outlet, 17: Pressure water tank, 18: Water outlet solenoid valve, 19: Low level water outlet, 20: Deflector, 21: Temperature transmitter, 22: Dissolved oxygen controller, 23: Water outlet solenoid valve, 24: High level water outlet, 25: Fertilizer applicator, 26: Check valve.
9 .6 146-149: Fix the font
Response 9.6: Thanks for your advice. We have corrected. Please see the manuscript.
9 .7 152, 154: no references to the software used in the work
Response 9.7: Thanks for your advice. We have supplemented the reference. Please see Line 201-205.
Livak, K., and Schmittgen, D., 2001. Analysis of Relative Gene Expression Data Using Real-Time Quantitative PCR and the 2−ΔΔCT Method. Methods 25, 402–408.
9 .8 237-257, 294-...: adjust font.
Response 9.8: Thanks for your advice. We have corrected. Please see Line285-306, 344-435.
Author Response File: Author Response.pdf
