In Search of Phytoremediation Candidates: Eu(III) Bioassociation and Root Exudation in Hydroponically Grown Plants

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

only minor revison:

line 92. An explain og REE is missing. It is first time in text.

part 2.1. It is missing information, how many plants were growing at general and for which part of experiment desing. 

Figure 1. If the information above had been provided, it would not have been required. However, the information used to calculate the standart deviation is indicated near Fig. 2, but is missing at Fig. 1. 
Also in Fig. 1 part a are two slow increases: (1) for T. incarnatum between 2.5h and 24h looks insignificant (it uses the purple color, and it is clear that the value does not go beyond the frame bars); (2) for L. corniculatus between 48h and 72h, the same level later is unclear (it uses very lite color, error bars are not visible clearly).

part 3.3.  It looks very good as a separate part, however, the term "species" usable not only for biological meaning confusing in the context of the entire text (because five biological species were used in full experiment desing, moreover, additional information supported part 3.3  is provided in supplemental Fig. S3 ). Maybe it has reason to find and use sinomyms.

Part 3.5. Very interesting calculation. If the information about pH measurements in the liquid medium during all experiments (effect of exudates to liquid medium) would be provided, it would be interesting and supported calculations. However, experiments are fin, so maybe in the future.

Author Response

Comments 1: line 92. An explain og REE is missing. It is first time in text.

Response 1: Thank you for pointing this out. We totally agree with this comment and added the respective explanation in line 92.            “… such as rare earth elements (REE).”

 

 

Comments 2: part 2.1. It is missing information, how many plants were growing at general and for which part of experiment desing. 

Response 2: Indeed, this information is not provided in part 2.1, because we were continuously cultivating many plants of the same species at the same time to have them readily at hand when needed for the experiment. We have added information on the number of replicates to the description of Figure 1.       “… Error bars represent the standard deviation of four biological replicates.”

 

 

Comments 3: Figure 1. If the information above had been provided, it would not have been required. However, the information used to calculate the standart deviation is indicated near Fig. 2, but is missing at Fig. 1. 
Also in Fig. 1 part a are two slow increases: (1) for T. incarnatum between 2.5h and 24h looks insignificant (it uses the purple color, and it is clear that the value does not go beyond the frame bars); (2) for L. corniculatus between 48h and 72h, the same level later is unclear (it uses very lite color, error bars are not visible clearly).

Response 3: Thank you for this elaborated comment. Regarding the missing information on the calculation of the standard deviation, we added the information below Figure 1 (see also Response 2). Regarding the second part of Comments 3, we added a possible explanation for this phenomenon in the text. “…For L. corniculatus, a slow increase of Eu(III) concentration becomes visible between 48 and 72 h. One possible explanation is the desorption, i.e. the release of Eu(III) from the roots or root surface due to plant defense or homeostasis mechanisms.”

 

 

Comments 4: part 3.3.  It looks very good as a separate part, however, the term "species" usable not only for biological meaning confusing in the context of the entire text (because five biological species were used in full experiment desing, moreover, additional information supported part 3.3  is provided in supplemental Fig. S3 ). Maybe it has reason to find and use sinomyms.

Response 4: Thank you for this remark. We totally agree that the term ‘species’ can be confusing in the context of this work. For better clarity, we substituted all ‘species’ referring to biological species by ‘type of plant’ or only ‘plant’ – where applicable – in the entire manuscript. Additionally, we added ‘luminescence’ in front of ‘species’ outside section 3.3 to underline the correct interpretation of this term.

Comments 5: Part 3.5. Very interesting calculation. If the information about pH measurements in the liquid medium during all experiments (effect of exudates to liquid medium) would be provided, it would be interesting and supported calculations. However, experiments are fin, so maybe in the future.

Response 5: Thank you for pointing this out. We agree, that information on pH is missing in the text. We measured pH in the liquid medium samples and found a slow increase of pH from initial 5.5 to 6.5 and sometimes 7 throughout the experiment time. This can be attributed to the interaction of the plant with the medium, i.e. root exudates but also a variety of other elements and organic compounds released by the roots. In order to show the reader that the calculation data shown in the graph are reasonable, we added a phrase regarding the pH-range during the experiment in the text. “Remarkably, the pH of the liquid medium increased slowly during the experiment, but not higher than pH 7 after 96 h.”

Author Response File: Author Response.docx

Reviewer 2 Report

Comments and Suggestions for Authors

The authors of manuscript entitled: “In search of phytoremediation candidates: Eu(III) bioassociation and root exudation in hydroponically grown plants.” studied the ability of various agricultural plants

to bioassociate Eu(III) in hydroponic culture.

 

The manuscript is well written. There are few minor corrections:

 

- the manuscript should be written in the third person.

- page 3, line 126 – seed were stored should be written seeds were stored

- page 5, Figure 1 – the quality of Figure is low. Also, please explain how it is possible that the concentration of Eu(III) rises for some plants during the time (L. corniculatus, and A. strigosa) as it is presented in Figure 1. a).

- page 7, line 285 – please delete the extra dot

- page 9, line 379 – it should be written are instead of all

- page 12, line 452 – it should be written above instead of below

- page 12, line 474 – please delete the extra space between the bracket and comma

- name of the plants in supplementary materials should be italic.

 

Overall, it is an interesting study and should be accepted after these minor corrections.

Author Response

Comments 1: the manuscript should be written in the third person.

Response 1: Thank you for pointing this out. We totally agree with this comment and exchanged first person against third person perspective/passive voice. The changes are highlighted in red in the revised manuscript.

 

 

Comments 2: page 3, line 126 – seed were stored should be written seeds were stored

Response 2: Thank you for this correction, we changed the spelling accordingly.

 

 

Comments 3: page 5, Figure 1 – the quality of Figure is low. Also, please explain how it is possible that the concentration of Eu(III) rises for some plants during the time (L. corniculatus, and A. strigosa) as it is presented in Figure 1. a).

Response 3: Thank you for noticing the low quality. We replaced the low resolution image by a high resolution one. The concentration rise could be explained by a partial desorption of the loosely bioassociated Eu(III) from the roots into the solution again. This can be induced by plant defense reactions or homeostasis mechanisms by the plant. We added an extra paragraph referring to this phenomenon in the text.

For L. corniculatus, a slow increase of Eu(III) concentration becomes visible between 48 and 72 h. One possible explanation is the desorption, i.e. the release of Eu(III) from the roots or root surface due to plant defense or homeostasis mechanisms.

 

 

Comments 4: page 7, line 285 – please delete the extra dot

Response 4: Thank you for spotting this mistake, we deleted the extra dot.

 

 

Comments 5: page 9, line 379 – it should be written are instead of all

Response 5: Thank you for this remark. Of course, it was meant to be ‘are’ instead of ‘all’. We changed the spelling accordingly.

 

 

Comments 6: page 12, line 452 – it should be written above instead of below

Response 6: Thank you for this correction. We totally agree and exchanges the word to ‘above’.

 

 

Comments 7: page 12, line 474 – please delete the extra space between the bracket and comma

Response 7: We thank the reviewer for this remark and deleted the accidentally placed extra space.

 

 

Comments 8: name of the plants in supplementary materials should be italic.

Response 8: Thank you for this remark. We totally agree and corrected this formatting issue.

Author Response File: Author Response.docx