Roots Structure and Development of Austrobaileya scandens (Austrobaileyaceae) and Implications for Their Evolution in Angiosperms
Round 1
Reviewer 1 Report
In this manuscript, the authors investigated the cellular structure of the root tip of Austrobaileya scandens, an ANA grade species. First they investigated the global cellular structure of the root tip. Then they focus on the differentiation in different tissue along the root axis: vasculature (phloem and xylem), pericyle, cortex and epidermis. Finally, they study the secondary growth in the root.
My main remarks concern the quality of the picture included in the paper. This is an important point since all the article is based on them. Pixelization and JPEG compression of the images hide the details of the pictures. It is impossible to see on the picture what the authors claimed. For example, on Fig 5F, the author point with an arrow the phloem, but we cannot see it. If there is not possibility to have better image quality for press, inset as in Fig 1I are required each time the authors point a specific zone with arrow or other annotations. These remarks apply at least to Fig 1D to Fig 1H, centre of figure 6, Fig 7 to 9, Fig 13 (oil gland), 14 (endodermis), 16, 19.
Certainly linked to the previous remark on pixelization and JPEG compression, the white text labels on figures 22 to 24 are difficult to discern.
Methods:
I would be nice to have the details of the microscope setting for each fluorescent dye used, ie excitation wavelength used, emission filter used.
Formatting:
I was puzzle by the figure numbering. I would have the group panels have the same figure number with per figure panel numbering (as for figure 5). Therefore, I would relabel figure 1 to 4 as figure 1A to 1D, figure 5 as figure 2, figure 6 as figure 3, figure 7 to 21, as figure 4A to 4O and figure 22-24 to figure 5A to 5C.
There is no title for the first part of the results.
I think there is an error l 123. The sentence do not make sense to me : "because its cells appeared more cytoplasmic". Do you mean the cells have more cytoplasm?
Fig 11: from where was the inset taken?
Author Response
Reviewer 1:
Comments and Suggestions for Authors
In this manuscript, the authors investigated the cellular structure of the root tip of Austrobaileya scandens, an ANA grade species. First they investigated the global cellular structure of the root tip. Then they focus on the differentiation in different tissue along the root axis: vasculature (phloem and xylem), pericyle, cortex and epidermis. Finally, they study the secondary growth in the root.
My main remarks concern the quality of the picture included in the paper. This is an important point since all the article is based on them. Pixelization and JPEG compression of the images hide the details of the pictures. It is impossible to see on the picture what the authors claimed. For example, on Fig 5F, the author point with an arrow the phloem, but we cannot see it. If there is not possibility to have better image quality for press, inset as in Fig 1I are required each time the authors point a specific zone with arrow or other annotations. These remarks apply at least to Fig 1D to Fig 1H, centre of figure 6, Fig 7 to 9, Fig 13 (oil gland), 14 (endodermis), 16, 19.
Certainly linked to the previous remark on pixelization and JPEG compression, the white text labels on figures 22 to 24 are difficult to discern.
We are sorry to hear that the rendering of some figures was not very good. All microscopy pictures were converted to TIFF and we hope that the problem is resolved However, we do not exclude the possibility that for practical reasons, you were (and will be) provided with lower quality pdfs files for the figures than those we uploaded. As for the annotations of figures 22 to 24, we have tried to increase the contrast around their edges and hope that they are not easier to see.
Methods:
I would be nice to have the details of the microscope setting for each fluorescent dye used, ie excitation wavelength used, emission filter used.
You are right but since the excitation and emission wavelength of these fluorochromes are all available online (e.g., cospheric.com ), and we think that it would make the methods or the legends of figures more difficult to read, especially with confocal images where one also use tissue autofluorescence. However, we have revised the material and methods to be a bit more concise and precise and added also in the legends of the figures which stains were used for each picture. We hope that this is now acceptable and would you or the editor still request more details, we could make a list providing for each image all relevant technical information in an appendix.
Formatting:
I was puzzle by the figure numbering. I would have the group panels have the same figure number with per figure panel numbering (as for figure 5). Therefore, I would relabel figure 1 to 4 as figure 1A to 1D, figure 5 as figure 2, figure 6 as figure 3, figure 7 to 21, as figure 4A to 4O and figure 22-24 to figure 5A to 5C.
This is a very good point and we thank you for your suggestion, and we amended the numbers of the figures and their references in the text accordingly.
There is no title for the first part of the results.
Thank you for noticing and we now have for each of the three sections the following titles: “”Root system and apex structure””, “Primary root growth and tissue differentiation”, “Secondary root growth and tissue differentiation”.
I think there is an error l 123. The sentence do not make sense to me : "because its cells appeared more cytoplasmic". Do you mean the cells have more cytoplasm?
Thank you for noticing, we meant that they had a denser cytoplasm and amended the text accordingly.
Fig 11: from where was the inset taken?
The inset was taken from another section of the same sample using bright field illumination with the Yellow filter, and we replaced it with a higher magnification image of the same section from the region now indicated with a white box.
Reviewer 2 Report
Review of the manuscript entitled: ‘Roots structure and development of Austrobaileya scandens (Austrobaileyaceae) and implications for their evolution in angiosperms’ by Bachelier et al., submitted to Plants.
The Authors present data and conclude that root structure and RAMs of A. scandens are similar to many magnolids, and suggest that the first woody flowering plants likely had an open meristem with common initials. There have been confirmed that anatomical traits could be of importance to understanding root evolutionary development and angiosperm phylogeny.
Generally, this work presents well understood concept and well prepared experiment. This work is well documented, interesting and original study that merits publication. Authors used appropriate histological methods that make the results reliable.
Please consider to make few small changes:
Abstract – line 20-21 – ‘secondary growth follows primary growth’ – is it possible another scenario? Please, correct this statement
Line 26 – ‘roots and RAMs of….’ – in fact RAMs are a part of the root, please modify it
Methods – line 101-105 – Please provide data for other images – not only for Figure 1 or decide to remove this sub-section transfer information (line 102-104) to line 75.
Line 68-69 - There is a lack of the information of repetitions, how many roots/plants were analyzed? Is it possible to provide statistical analyses, e.g. micrographic measurements of anatomical traits?
Line 76, 82, 88 – what does it mean ‘some roots’? How many, exactly?
Results – Please, be sure that the resolution of each original Figure is sufficient for publication, if not – it is necessary to increase the resolution
Disscusion – this chapter could be extended, there are only over a dozen cited references, I believe that the topic was not exhausted; moreover it seems that paper by Baylis [25], line 322 is not cited with the appropriate number [25], if I am not wrong it should be 28? Please verify the whole list to avoid such errors
Author Response
Reviewer 2:
Comments and Suggestions for Authors
Review of the manuscript entitled: ‘Roots structure and development of Austrobaileya scandens (Austrobaileyaceae) and implications for their evolution in angiosperms’ by Bachelier et al., submitted to Plants.
The Authors present data and conclude that root structure and RAMs of A. scandens are similar to many magnolids, and suggest that the first woody flowering plants likely had an open meristem with common initials. There have been confirmed that anatomical traits could be of importance to understanding root evolutionary development and angiosperm phylogeny.
Generally, this work presents well understood concept and well prepared experiment. This work is well documented, interesting and original study that merits publication. Authors used appropriate histological methods that make the results reliable.
Please consider to make few small changes:
Abstract – line 20-21 – ‘secondary growth follows primary growth’ – is it possible another scenario? Please, correct this statement
This is a good point and we deleted “secondary growth follows primary growth. The stele is”
Line 26 – ‘roots and RAMs of….’ – in fact RAMs are a part of the root, please modify it
Yes, we agree, and modified the sentence, which now reads “Roots structure and anatomy of scandens are thus essentially similar to some previously described in Amborella or Illicium in the ANA grade and many magnoliids, and suggest that the first woody flowering plants likely had an open RAM with common initials.”
Methods – line 101-105 – Please provide data for other images – not only for Figure 1 or decide to remove this sub-section transfer information (line 102-104) to line 75.
You are right and we have revised the material and methods to be a bit more concise and precise, and added also in the legends of the figures which stains were used for each picture. We hope that this is now acceptable and would you or the editor still request more details, we could make a list providing for each image all relevant technical information in an appendix.
Line 68-69 - There is a lack of the information of repetitions, how many roots/plants were analyzed? Is it possible to provide statistical analyses, e.g. micrographic measurements of anatomical traits?
This is a good point and we inserted rough estimates of the number of roots we studied, but we did not add details on measurements since the focus is on the patterns of development and structure, and not on such variations
Line 76, 82, 88 – what does it mean ‘some roots’? How many, exactly?
We sometimes did not count but still tried to indicate how many roots we studied using each technic in the material and methods l. 76, 82, and 88.
Results – Please, be sure that the resolution of each original Figure is sufficient for publication, if not – it is necessary to increase the resolution
As we replied to the other reviewer who seems to have received plates with a low resolutions, we are sorry to hear that the rendering of some figures was not very good. All microscopy pictures were converted to TIFF and we hope that the problem is resolved However, we do not exclude the possibility that for practical reasons, you were (and will be) provided with lower quality pdfs files for the figures than those we uploaded. As for the annotations of figures 22 to 24, we have tried to increase the contrast around their edges and hope that they are not easier to see.
Disscusion – this chapter could be extended, there are only over a dozen cited references, I believe that the topic was not exhausted; moreover it seems that paper by Baylis [25], line 322 is not cited with the appropriate number [25], if I am not wrong it should be 28? Please verify the whole list to avoid such errors
We agree, however, decided not to modify the discussion and leave it as is. We also thank you for noticing and we also made sure that all references were now all correctly referred to and Bailys was consistently referred to as [25].
