Pb Pollution Stress in Alnus cremastogyne Monitored by Antioxidant Enzymes

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

This paper deals with the effect of soluble Pb upon nutrient concentrations and anti-oxidant enzymes as environmental stress factors. Though the title might reflect the financial source, I would recommend to change it.

Maybe: "Pb pollution stress in Alnus cremastogyne monitored by Anti-oxidant enzymes"  (or else)

The abbreviations of the enzymes has been given in lines 184-189, but in the abstract they are mentioned as well. 

The effects are named "hormesis", which is common in treatments with Rare Earth elements also. Small pollution (50 mg/kg) causes activation of the defence mechanism of the organism, which overrides toxicity effects. Therefore, the effects versus Pb-concentration are not linear. You may refer to this term within the discussion.

How did you discriminate absorbing roots and transport roots? Diameter? Wood contents?

Line 189: spelling error "sugar"

Line 211-215: the text is a bit contradictory. Write e.g. "Nutrient content ... did hardly change with increasing Pb content", or write e.g. "Nutrient content ... did not depend in a linear way from increasing Pb content"

Line 282: BCF (undefined) surely means "bio concentration factor"

Author Response

Reply to the comments

 

Dear Editor, Dear reviewers

Thanks very much for taking your time to review this manuscript. I really appreciate all your comments and suggestions! Please find my itemized responses in below and myrevisions/corrections in the re-submitted files. Thanks again!

 

Reply to the comments of Reviewer 1

(1)Comments: This paper deals with the effect of soluble Pb upon nutrient concentrations and anti-oxidant enzymes as environmental stress factors. Though the title might reflect the financial source, I would recommend to change it. Maybe: "Pb pollution stress in Alnus cremastogyne monitored by Anti-oxidant enzymes" (or else)

Reply: According to the reviewers' comments, the title has been changed to "Pb pollution stress in Alnus cremastogyne monitored by Anti-oxidant enzymes"

 

(2)Comments: The abbreviations of the enzymes has been given in lines 184-189, but in the abstract they are mentioned as well.

Reply: We have removed the abbreviations from the summary. Thanks for your correction.

 

(3)Comments: The effects are named "hormesis", which is common in treatments with Rare Earth elements also. Small pollution (50 mg/kg) causes activation of the defence mechanism of the organism, which overrides toxicity effects. Therefore, the effects versus Pb concentration are not linear. You may refer to this term within the discussion.

Reply: At the suggestion of the reviewers, we have added "hormesis" content to the Discussion section to explain in more depth the reasons for the increase and then decrease of some plant stress indicators. (Line 339-341)

 

(4)Comments: How did you discriminate absorbing roots and transport roots? Diameter? Wood contents?

Reply: We classified the root system according to meristematic class (the most terminal, smallest diameter root tip was defined as a class 1 root, two class 1 roots intersected to form a class 2 root, and so on, with classes 1-3 classified (not lignified) as absorptive roots, and class 4 and above classified (lignified) as transport roots.

 

(5)Comments: Line 189: spelling error "sugar"

Reply: We apologize for our carelessness. The error has been corrected in our resubmitted manuscript.

 

(6)Comments: Line 211-215: the text is a bit contradictory. Write e.g. "Nutrient content ... did hardly change with increasing Pb content", or write e.g. "Nutrient content ... did not depend in a linear way from increasing Pb content"

Reply: At the suggestion of the reviewers, We have re-written this sentence to make it clearer. "Nitrogen content in the transport roots of Alnus cremastogyne saplings increased significantly with increasing soil Pb content; phosphorus and potassium content in the leaves and phosphorus content in the absorbing roots decreased significantly; and there were no significant changes in nitrogen, phosphorus, and potassium content in the branches and trunks (Table 5). " (Line288-292)

 

(7)Comments: Line 282: BCF (undefined) surely means "bioconcentration factor"

Reply: We apologize for our carelessness. The error has been corrected in our resubmitted manuscript.

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

This article studies the feasibility of Alnus cremastogyne to be used for Pb phytoremediation purposes.

Results are quite predictable, taking to about the behavior of this element, and there were not any data about this plant considering it for extraction of any metal.

Do you know is this plant can accumulate other trace elements?

Did you have some data using real Pb contaminated soil? Sometimes results are quite different.

Did you analyze the Pb in soil after the experimental pollution? To make sure the level of pollution in soil.

Experimental design: add that plants were growing for 6 months.

Line 135: plants do not baked…were dried

Lines 145-160. Explain this in a clear way…sometimes confuse methods

Line 191-92 explain this sentence. Re-write.

Explain deeper why some plant stress indicators increase and then decrease.

Author Response

Reply to the comments

 

Dear Editor, Dear reviewers

Thanks very much for taking your time to review this manuscript. I really appreciate all your comments and suggestions! Please find my itemized responses in below and myrevisions/corrections in the re-submitted files. Thanks again!

 

Reply to the comments of Reviewer 2

(1)Comments: This article studies the feasibility of Alnus cremastogyne to be used for Pb phytoremediation purposes. Results are quite predictable, taking to about the behavior of this element, and there was not any data about this plant considering it for extraction of any metal. Do you know is this plant can accumulate other trace elements?

Reply: Through reviewing relevant literature, We found that poplar can also enrich metal elements such as Cd, Cr, Cu, Zn and Ni. As a widely distributed species, Alnus cremastogyne grows rapidly and has a large biomass, which can be used for timber or paper making. Lead (Pb) is one of the most common toxic heavy metal elements in soil contamination, which can be continuously enriched in the food chain and eventually threaten human health. Therefore, We used Alnus cremastogyne as an experimental tree species to investigate its phytoremediation potential on Pb-contaminated soil.

 

(2)Comments: Did you have some data using real Pb-contaminated soil? Sometimes results are quite different.

Reply: Before the experiment, we had checked the relevant information. According to the GB36600-2018 soil pollution risk control standard, the screening value of Pb for Class I land use is 400mg kg, and the screening value of Pb for Class II land use is 800mg kg. The amount of Pb contained in soil is generally between 2-200 mg/kg, and there are variations between different regions. Therefore, in the experiment, I set the concentration of Pb as 0, 50, 100, 200, and 400 mg/kg.

 

(3)Comments: Did you analyze the Pb in the soil after the experimental pollution? To make sure the level of pollution in soil.

Reply: Yes, after the experiment, We determined the soil Pb concentration under different treatments, which was used to understand the level of contamination in the soil and to calculate the bioconcentration factor of the plants. These data are presented in Tables 3 and 4.

 

(4)Comments: Experimental design: add that plants were growing for 6 months.

Reply: We have added this to the experimental design (Line 120)

 

(5)Comments: Line 135: plants do not baked…were dried (Line 136)

Reply: We apologize for our carelessness. The error has been corrected in our resubmitted manuscript.

 

(6)Comments: Lines 145-160. Explain this in a clear way…sometimes confusing methods.

Reply: We did our best to improve the manuscript and made some changes to it. These changes do not affect the content or framework of the paper. Instead of listing these changes here, we have highlighted them in red in the revised paper. We sincerely thank the editors/reviewers for their enthusiastic work and hope that the corrections will be approved.

 

(7)Comments: Line 191-92 explain this sentence. Re-write.

Reply: We have re-written this sentence to make it clearer. (Line 189-192)

“The total biomass of plants tended to decrease with increasing Pb concentration. When the Pb concentration was lower than 100 mg kg^-1, the biomass of each organ of the plant was not significantly different from that of CK, which indicated that the effect of low Pb concentration on the growth of Alnus cremastogyne saplings was small.”

 

(8)Comments: Explain deeper why some plant stress indicators increase and then decrease.

Reply: At the suggestion of the reviewers, we have added "hormesis" content to the Discussion section to explain in more depth the reasons for the increase and then decrease of some plant stress indicators. (Line 339-341)

Author Response File: Author Response.pdf