Shading Inhibits Sugar Accumulation in Leaf and Fruit of Jujube (Ziziphus jujuba Mill.)

Round 1

Reviewer 1 Report

This is an interesting and important contribution to the field of plant shading, but the manuscript itself required some corrections and additions.

I would like the authors to address the following issues:

11. Line 42: Is Xu et al. 2021 should be Xu & Liesche 2021

     Lines: 440-441: this paper was not cited in manuscript.

22. There are several misformattings of plant Latin names. Latin name should be in Italic (eg. line 50, 68). Full name should be used only when it first mentioned in the text.

33.  In the manuscript were cited: Palmer et al. 2013 (line 30), Peavey et al. 2020 (line 31), (Li et al. 2019 (line 37) but above authors did not included in References. 

44. Materials and methods. There is a lack of crucial information to understand the experiments.

· Did plants during whole experiment were fertilized?

· In Figs. 1, 2 and 3 Authors expressed content of pigments/sugars in µg/g or mg/g, respectively; it was (micro)grams pre fresh or dry weight? This information should be incorporate in 2.2. and 2.3 part of materials and methods, eg. The chlorophyll content was expressed in….

· Which level of plants the leaves for the experiment were collected from

· Number of biological replicates, number of plants per replicate, number of analytical replicates.

· To the experiments materials, especially leaves were collected always at the same period of day?

   5. Results

·       I do not know, why Authors showed ‘total sugar’ in leaves and fruits. It is  just a sum of fructose, glucose and sucrose. In both figures: 1A and 1D as well as 2A and 2D diagrams look almost the same, because the concentration of sucrose is markedly higher than other examined sugars. In my opinion this part of results should be removed.

·         Line 132: ‘after shadnig’ – MS or SS?

·         Line 137-138: ‘Shading promoted a significant decrease of chl a/b ratio in late developmental period’ is too general.

6. Discussion

Lines 257 and 330. Authors should change the titles of this part of Discussion. They did not measure the rate of photosynthesis as well as long distance sugar transport. This titles are speculative and mislead the reader.

Author Response

1. Line 42: Is Xu et al. 2021 should be Xu & Liesche 2021

A：It has been modified to "Xu & Liesche 2021" according to comments.

2. Lines: 440-441: this paper was not cited in manuscript.

A：This paper (Roopendra et al. 2019) is cited at Line 306 and Line 333.

3. There are several misformattings of plant Latin names. Latin name should be in Italic (eg. line 50, 68). Full name should be used only when it first mentioned in the text.

A: Line 50: It has been modified to “Ziziphus jujuba Mill.”. Line 68: It has been modified to “Jujube cultivar ‘Luojiangtiaoyuanzao’”.

4. In the manuscript were cited: Palmer et al. 2013 (line 30), Peavey et al. 2020 (line 31), (Li et al. 2019 (line 37) but above authors did not included in References.

A：Line 501-505: The two papers of “Palmer et al. 2013” and “Peavey et al. 2020” have been added to the literature list. Line 37: After verification, the correct literature is “Li et al. 2020”.

5. Materials and methods. There is a lack of crucial information to understand the experiments. Did plants during whole experiment were fertilized?

A: In order to eliminate the effects of fertilizers and pesticides on the plants, the plants were not fertilized or drugged during whole experiment period.

6. In Figs. 1, 2 and 3 Authors expressed content of pigments/sugars in µg/g or mg/g, respectively; it was (micro)grams pre fresh or dry weight? This information should be incorporate in 2.2. and 2.3 part of materials and methods, eg. The chlorophyll content was expressed in….

A: All the weights mentioned in this paper are fresh weight, e.g. sugar content and photosynthetic pigments content. Details are added as follows: Line 88: “Fresh leaf (0.5g) were ground with…”; Line 98: “ The fresh leaf or fruitsample (0.5g) …”

7. Which level of plants the leaves for the experiment were collected from…

A: Line 82: The leaves were collected at node 4-7 of fruit-bearing shoot.

8. Number of biological replicates, number of plants per replicate, number of analytical replicates.

A: Line 81-86: The experiment was repeated three times in the field with 30 leaves and 30 fruits per replicate. Three biological analytical replicates were performed for each analysis.

9. To the experiments materials, especially leaves were collected always at the same period of day?

A: Line 82-84: This experiment was to explore the effects of shading on sugar metabolism in leaves and fruits. Therefore, leaves and fruits were collected on the same day for five times, respectively 0d, 16d, 31d, 46d and 59d after shading.

10. I do not know, why Authors showed ‘total sugar’ in leaves and fruits. It is just a sum of fructose, glucose and sucrose. In both figures: 1A and 1D as well as 2A and 2D diagrams look almost the same, because the concentration of sucrose is markedly higher than other examined sugars. In my opinion this part of results should be removed.

A: Figure 2D and Figure 3D have been deleted according to the suggestion, and Figure 6 has been modified accordingly. In addition, the total sugar content in the “Results” and “Discussions” has been modified or deleted. See details in “Results 3.2, 3.3, 3.6” and “Discussions 4.2, 4.3”.

11. Line 132: ‘after shadnig’ – MS or SS?

A: Line 132: To avoid ambiguity, this sentence has been modified as follows: The contents of chl a, chl b and total chl were significantly higher with MS and SS treatment for 31d, 46d and 59d than with NS.

12. Line 137-138: ‘Shading promoted a significant decrease of chl a/b ratio in late developmental period’ is too general.

A: Line 138-140: Shading treatment promoted accelerated the decline of chl a/b ratio of leaves in late developmental period for 31d, 46d and 59d. Compared with NS, chl a/b ratio in MS and SS leaves significantly decreased 15.26% and 18.53% after shading for 59d, respectively.

13. Lines 257 and 330. Authors should change the titles of this part of Discussion. They did not measure the rate of photosynthesis as well as long distance sugar transport. This titles are speculative and mislead the reader.

A: The subtitle of Discussion has been amended to read as suggested by the reviewers: Line 257: Shading increased photosynthetic pigment contents of leaves, but decreased specific leaf weight. Line 330: Shading may affected sugar transport from leaf to fruit.

Author Response File: Author Response.docx

Reviewer 2 Report

The Manuscript shed light on an important aspect of jujuba plant management. The authors demonstrate that the use of shade  direct  impact on sugar content and transport on leaves and fruits  by modulating the photosynthesis and indicate that could be an important issue on crop management. The manuscript is well written and minor changes are requested.

First of all, I have some question about the plant phenotyping. Does the plant from the  MS or SS are chlorotic or clorophylled. Also, the authors have conducted additional anatomical section in order to verify changes in the leaf thickness and phloem cells organization? It seems a interesting target. 

The figures are well presented. I also have some suggestion regarding the label of figures 4 and 5. They are too small. There any possible way to improve the number os days label  separately from the  treatment. The authors can do some additional bars. It will help the reader.  Also de legend in figure 5 and 6 must come with the indication of the acronyms “ sucrose 201 synthase (SS), sucrose phosphosynthase (SPS), invertase (INV), fructokinase (FK), pyrophosphory- 202 lase (UGP), hexokinase (HK). “

Author Response

1. First of all, I have some question about the plant phenotyping. Does the plant from the MS or SS are chlorotic or clorophylled. Also, the authors have conducted additional anatomical section in order to verify changes in the leaf thickness and phloem cells organization? It seems a interesting target.

A: In this study, shading treatment increased the chlorophyll content of jujube leaves, but decreased the specific leaf weight. This paper did not explore the effect of shading on leaf anatomical structure to verify changes in the leaf thickness and phloem cells organization, while this may be the direction of future research.

2. The figures are well presented. I also have some suggestion regarding the label of figures 4 and 5. They are too small. There any possible way to improve the number os days label separately from the treatment. The authors can do some additional bars. It will help the reader.  Also de legend in figure 5 and 6 must come with the indication of the acronyms “ sucrose 201 synthase (SS), sucrose phosphosynthase (SPS), invertase (INV), fructokinase (FK), pyrophosphory- 202 lase (UGP), hexokinase (HK). “

A: Figure 4 and Figure 5 have been deleted according to the suggestion. Corresponding annotations have also been added in Figures 5 and 6.

Author Response File: Author Response.docx