Response of Tracheid Structure Characteristics and Lignin Distribution of Taxodium Hybrid Zhongshanshan to External Stress

Round 1

Reviewer 1 Report

It is an interesting work that presents appropriate and novel techniques. I liked the way you approach the subject and the way you discuss your results.

Author Response

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Reviewer 2 Report

General comment: In this paper, the changes in anatomical characteristics, morphology, lignin distribution of the tracheids in reaction wood of Taxodium hybrid ‘Zhongshanshan’ were analyzed by optical microscope, SEM, LSCM, and Raman imaging techniques. This is an interesting topic, which may provide the theoretical basis for the response mechanism of Taxodium hybrid ‘Zhongshanshan’ reaction wood anatomical structure to the external environment. There are some minor issues that should be addressed.

Point 1: Abstract, Please check the experimental methods described in the abstract.

Point 2: Tracheid dimensions analysis, “For the tracheid dimensions observation, the CW, LW, and OW samples were delignified using Franklin’s method” A more detailed information in the methods for tracheid dimensions analysis shall be added.

Point 3: Roundness value of tracheid measurement. This parameter is a general dimension index for compression cells? If so, please add some reference.  

Point 4: Tracheid dimensions analysis, Please add the software used for data analysis.

Point 5: Cell wall structure of reaction wood, “However, with the help of the presence or absence of the secondary cell wall S2L layer, a relatively clear demarcation line between normal and compressed tracheids in the transition region can be determined.” If possible, please draw this demarcation line in the figure.

Point 6: Anatomical characteristics of reaction wood,“Lignin in wood is the main object of staining for saffron.” please add the references here.

Point 7: Figure9, Please indicate the meaning of the arrow.

Point 8: Conclusion. Please clarified the conclusion, just give some important output from the investigation.

Author Response

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Reviewer 3 Report

The manuscript submitted for review, entitled: Response of tracheid structure characteristics and lignin distribution of Taxodium hybrid ‘Zhongshansha’ to external stress addresses an important only partially understood issue related to compression wood formation.

Merits

The work is clearly written, the layout is logical, and the difficult subject matter is presented in an interesting way.

The strengths of the work are the clear figures and good quality microscopic images made with various techniques. The object of observation is well exposed and does not raise questions.

The major premise of the paper regarding the distribution of lignin in compression, opposition and lateral wood was presented very well and is valuable.

Critique and suggestions

The major shortcoming of the work is the poor discussion, or rather the lack of it. No works on similar topics were cited, and it is unclear to what extent lignin decomposition in compression wood has been studied. There are certainly no studies on Taxodium hybrid 'Zhongshansha', but there are works on other coniferous species. A paper at this level should include a reference to the results obtained for other species. This section should be expanded in the context of confirming or disputing the results obtained by other authors. Similar methods for pine were applied by Ji Z. et al. (2013), and this work was not mentioned.

The paper does not say whether the compression wood was formed in the juvenile or mature zone, and this may affect the proportion of lignin, which is related to the maturation of the tissue (Purusatama et al. 2020).

The proportion of lignin also depends on other chemicals and shows some correlations, as they can affect the proportion of lignin (Chen et al. 2007).

It is also worth considering other works, such as Fahey et al. (2018), Peng et al. (2019, 2020).

I suggest supplementing the Discussion chapter with works by other authors. Please also consider combining Discussion with the Results chapter.

ll. 42-48 What exactly are the limitations associated with high lignification, which properties are changed and why is this important? A broader description regarding the changes in hardness, strength, and irregularity of the structure in the context of compression wood or pointing to works that describe this, is welcome.

Markings a) b) c) d) on fig 8 should be described

References

 Chen, Q. M., Hu, Z., Chang, H. M., & Li, B. (2007). Micro analytical methods for determination of compression wood content in loblolly pine. Journal of wood chemistry and technology, 27(3-4), 169-178.

Fahey, L. M., Nieuwoudt, M. K., & Harris, P. J. (2018). Using near infrared spectroscopy to predict the lignin content and monosaccharide compositions of Pinus radiata wood cell walls. International Journal of Biological Macromolecules, 113, 507-514.

Ji, Z., Ma, J. F., Zhang, Z. H., Xu, F., & Sun, R. C. (2013). Distribution of lignin and cellulose in compression wood tracheids of Pinus yunnanensis determined by fluorescence microscopy and confocal Raman microscopy. Industrial Crops and Products, 47, 212-217.

Peng, H., Salmén, L., Jiang, J., & Lu, J. (2020). Contribution of lignin to the stress transfer in compression wood viewed by tensile FTIR loading. Holzforschung, 74(5), 459-467.

Peng, H., Salmén, L., Stevanic, J. S., & Lu, J. (2019). Structural organization of the cell wall polymers in compression wood as revealed by FTIR microspectroscopy. Planta, 250(1), 163-171.

Purusatama, B. D., Choi, J. K., Lee, S. H., & Kim, N. H. (2020). Microfibril angle, crystalline characteristics, and chemical compounds of reaction wood in stem wood of Pinus densiflora. Wood science and technology, 54(1), 123-137.

Author Response

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