Synergistic Effects of Supplemental Lighting and Foliar Phosphorus Application on Flowering in Passion Fruit (Passiflora edulis)

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

This paper presents valuable results concerning the effect of light and P supplementation on passiflora flowering. The introduction is well-written and correctly explains the study gaps and needs. This study has a good utility meaning and is well-written and clearly explained.

 

Keywords: Delete the keywords that appear in your title. Add other ones.

ln 35 including

ln 56 explain ATP

Field experiment, explain more

• how LED light was applied: in panels,
• For how long and in which plant phase?
• How high above the canopy were lights installed?

Figure 1, 1-cm-bar can be misleaded with all other white bars.

Methods: add and explain all chlorophyll fluorescence parameters you measured in the text or in the table.

Author Response

Horticulturae

 

Dear Reviewer:

 

I wish to resubmit our manuscript with ID: horticulturae-3601206 for publication in Horticulturae. The title “Synergistic Effects of Supplemental Lighting and Foliar Phosphorus Application on Flowering in Passion Fruit (Passiflora edulis)”.

 

We thank you for giving us the opportunity to resubmit a revised manuscript. We are grateful to the peer reviewers for providing us with their insightful comments, which have helped improve our manuscript. Please find our responses to the peer reviewers’ comments attached. We hope our manuscript is now ready for submission in Horticulturae.

 

Thank you for your reconsideration. I look forward to hearing from you again.

 

Sincerely,

 

Dongyu Sun

 

 

Comments and Suggestions for Authors: 

This paper presents valuable results concerning the effect of light and P supplementation on passiflora flowering. The introduction is well-written and correctly explains the study gaps and needs. This study has a good utility meaning and is well-written and clearly explained.

Response:

We are very grateful to you for your time and suggestion to improve our manuscript. This manuscript has been revised according to your comments and suggestions. The point by point comments and author response are given below. The author’s replies are listed below each comment in red.

 

Questions:

Point 1: Keywords: Delete the keywords that appear in your title. Add other ones.

Response 1: We are very grateful to you for your time and suggestion to improve our manuscript. We have carefully revised the keywords in our manuscript to avoid duplication with terms already present in the title. The updated keyword list now reads: "Keywords: photoperiod sensitivity; flowering control; nutrient management; abiotic stress mitigation" (see Page 1, line 31 in the revised manuscript). These terms were selected to better reflect the study’s focus on physiological mechanisms (photoperiod sensitivity, abiotic stress mitigation) and applied agronomic strategies (flowering control, nutrient management), while maintaining independence from the title’s phrasing.

 

 

Point 2: ln 35 including.

Response 2: Thank you for your comments. We have adjusted the manuscript formatting as suggested. The corrected section heading "1. Introduction" (see Page 1, line 34 in the revised manuscript). This modification ensures proper hierarchical structure and alignment with the journal's style guidelines.

 

Point 3: ln 56 explain ATP. 

Response 3: Thank you for your comments. We have specified the full term for ATP at its first occurrence. The text now reads "Adenosine Triphosphate (ATP)" (see Page 2, line 61 in the revised manuscript).

 

Point 4: Field experiment, explain more. 

Response 4: Thanks for your comments. We have expanded the description of field experimental protocols in the revised manuscript. Detailed information about plant materials, growth conditions, and treatment specifications can now be found in Section 2.1 Plant materials and growth conditions (see Page 2, line 80 in the revised manuscript).

 

Point 5: how LED light was applied: in panels.

Response 5: Thank you for your comments. We have incorporated detailed specifications regarding the LED light application protocol in the revised Section 2.1 Plant materials and growth conditions (see Page 2, line 80 in the revised manuscript).

 

Point 6: For how long and in which plant phase?

Response 6: Thank you for your comments. We have thoroughly revised Section 2.1 Plant materials and growth conditions to include comprehensive details about both the LED lighting implementation and the physiological status of the mature passion fruit plants (see Page 2, line 80 in the revised manuscript).

 

Point 7: How high above the canopy were lights installed?

Response 7: Thank you for your comments. We have enhanced the LED lighting system description in Section 2.1 Plant materials and growth conditions to explicitly detail the spatial configuration relative to both the passion fruit plants and greenhouse structure (see Page 2, line 80 in the revised manuscript). 

 

Point 8: Figure 1, 1-cm-bar can be misleaded with all other white bars

Response 8: Thank you for your comments. We have modified Figure 1 to improve visual clarity by replacing all horizontal reference lines with vertical lines, creating clear distinction from the 1-cm-bar (see Page 3, line 122 in the revised manuscript). 

 

Point 9: Methods: add and explain all chlorophyll fluorescence parameters you measured in the text or in the table.

Response 9: Thank you for your comments. We have incorporated detailed chlorophyll fluorescence measurement protocols and parameter specifications in the revised Section 2.3 Measurement of photosynthetic characteristics, chlorophyll fluorescence parameters of the manuscript (see Page 3, line 131 in the revised manuscript). 

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

The main question addressed in this paper is how to reduce flowering instability in passion fruit. This question is especially relevant under adverse light conditions typical of subtropical climates. This paper fills a gap in our understanding of how to improve the tolerance of passion fruit cultivation under low light conditions. The paper describes an experiment combining supplemental lighting and targeted phosphorus fertilization. The authors showed that this approach not only increased photosynthetic efficiency but also improved flowering stability. The paper is well written and illustrated.
However, I have a few comments:
1. Sections 3.1 and 3.6 begin with the words “As shown in Figure…” - in my opinion, this is not the best way to start a section. It would be better to write a more general sentence first.
2. I would advise the authors to increase the number of experimental groups and test other variations in light intensity and fertilizer concentration.

Author Response

Horticulturae

 

Dear Reviewer:

 

I wish to resubmit our manuscript with ID: horticulturae-3601206 for publication in Horticulturae. The title “Synergistic Effects of Supplemental Lighting and Foliar Phosphorus Application on Flowering in Passion Fruit (Passiflora edulis)”.

 

We thank you for giving us the opportunity to resubmit a revised manuscript. We are grateful to the peer reviewers for providing us with their insightful comments, which have helped improve our manuscript. Please find our responses to the peer reviewers’ comments attached. We hope our manuscript is now ready for submission in Horticulturae.

 

Thank you for your reconsideration. I look forward to hearing from you again.

 

Sincerely,

 

Dongyu Sun

 

 

Comments and Suggestions for Authors: 

The main question addressed in this paper is how to reduce flowering instability in passion fruit. This question is especially relevant under adverse light conditions typical of subtropical climates. This paper fills a gap in our understanding of how to improve the tolerance of passion fruit cultivation under low light conditions. The paper describes an experiment combining supplemental lighting and targeted phosphorus fertilization. The authors showed that this approach not only increased photosynthetic efficiency but also improved flowering stability. The paper is well written and illustrated.

Response:

We are very grateful to you for your time and suggestion to improve our manuscript. This manuscript has been revised according to your comments and suggestions. The point by point comments and author response are given below. The author’s replies are listed below each comment in red.

 

Questions:

Point 1: Sections 3.1 and 3.6 begin with the words “As shown in Figure…” - in my opinion, this is not the best way to start a section. It would be better to write a more general sentence first.

Response 1: We are very grateful to you for your time and suggestion to improve our manuscript. We have revised the results section of the article, and provided detailed descriptions of the rationale for conducting this experiment in Sections 3.1 The effects of supplemental lighting and Plant-Prod spraying on the horticultural traits of passion fruit (see Page 4, line 146 in the revised manuscript). and 3.6 The effects of supplementary light and Plant-Prod spraying on the chlorophyll fluorescence parameters of passion fruit (see Page 7, line 236 in the revised manuscript), enriching the content of the paper.

 

Point 2: I would advise the authors to increase the number of experimental groups and test other variations in light intensity and fertilizer concentration.

Response 2: We sincerely appreciate the reviewer's valuable suggestions. This study was specifically designed to address practical challenges in passion fruit cultivation under subtropical conditions. Our preliminary evaluation of four commercial high-phosphorus flowering-promoting fertilizers demonstrated that the Plant-Prod formulation (10:52:10 NPK) showed optimal efficacy due to its transparent composition and precise nutrient ratios. Considering that passion fruit flowering periods frequently coincide with overcast/rainy seasons, we focused on a representative low light intensity condition without testing intensity variations. The current research successfully addressed this specific agricultural scenario, achieving statistically significant flowering promotion effects that provide immediately applicable solutions for growers. We have identified light-phosphorus concentration gradient interactions as a key focus for future research.

Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

Please read the attached file. Include responses to my comments in the text of the manuscript. Thank you!

Comments for author File: Comments.pdf

Author Response

Horticulturae

 

Dear Reviewer:

 

I wish to resubmit our manuscript with ID: horticulturae-3601206 for publication in Horticulturae. The title “Synergistic Effects of Supplemental Lighting and Foliar Phosphorus Application on Flowering in Passion Fruit (Passiflora edulis)”.

 

We thank you for giving us the opportunity to resubmit a revised manuscript. We are grateful to the peer reviewers for providing us with their insightful comments, which have helped improve our manuscript. Please find our responses to the peer reviewers’ comments attached. We hope our manuscript is now ready for submission in Horticulturae.

 

Thank you for your reconsideration. I look forward to hearing from you again.

 

Sincerely,

 

Dongyu Sun

 

 

Comments and Suggestions for Authors: 

The presented work is devoted to studying the possibility of using phosphorus fertilization and supplementary lighting to increase the number of passion fruit flowers low illumination (lack of stress) is a really big limiting factor for obtaining a good fruit yield. The dual model proposed by the authors is promising and suitable for adaptation in the agricultural sector. The work is well constructed and the methods are adequate to the objectives. The authors focus on phenotypic evaluation of plants and analysis of photosynthesis efficiency. It can be concluded that phosphorus fertilizers improve photosynthesis settings.

Response:

We are very grateful to you for your time and suggestion to improve our manuscript. This manuscript has been revised according to your comments and suggestions. The point by point comments and author response are given below. The author’s replies are listed below each comment in red.

 

Questions:

Point 1: In the Introduction part, clarify crop losses from monsoons. Is there such data. Do passion fruit plants grow wherever there is monsoon? And how do they grow where there is good light?

Response 1: We appreciate the reviewer's insightful questions regarding monsoon impacts on passion fruit cultivation. Monsoon climates pose significant economic risks to subtropical fruit production, particularly for passion fruit, which is predominantly cultivated in southern China (e.g., Guangdong, Fujian, Guizhou, Guangxi, and Hainan). During the flowering period, heavy rainfall coincides with inadequate protective infrastructure in these regions, leading to substantial yield losses. Field studies in Guizhou demonstrate that rain-sheltering combined with supplemental lighting can mitigate these losses, improving yields by 20-23%. This context is now explicitly addressed in the revised Introduction (Section 1) of our manuscript, highlighting both the agroclimatic challenges and practical interventions (see Page 2, line 45 in the revised manuscript).

As a perennial vine, passion fruit thrives in optimal temperatures of 25-30°C, with its flowering process critically regulated by photoperiodic cues. Long-day (LD) conditions (16h light/8h dark) activate core flowering genes (e.g., FT), synchronizing environmental signals with endogenous developmental programs to initiate floral primordia. Field trials in Zhejiang (Lishui) demonstrated that LD treatment in ‘Tainong No. 1’ significantly enhanced flower bud differentiation, requiring 28 days from bud emergence to anthesis and 60-80 days to fruit maturity. Similarly, LD exposure increased floral initiation rates by 60% in ‘Huangjin’ passion fruit in Yunnan and Hainan, while short-day (SD) conditions (8h light/16h dark) delayed flowering. These results underscore photoperiod as a pivotal environmental determinant, where SD or insufficient light suppresses bud formation, leading to flower drop and yield losses.

 

Point 2: How sensitive are they? Have you looked at the yield, do all the flowers produce fruit? This question is related to the fact that sometimes improving growing conditions will increase the number of flowers but not the number of fruits. That's also a question.

Response 2: Thanks for your comments. ‘Qinmi No. 9’ is a long-day responsive cultivar. Current literature reports indicate that passion fruit is a long-day crop, though our additional research reveals distinct differences in photoperiod sensitivity among varieties. Among these, ‘Tainong No. 1’ and ‘Qinmi No. 9’ exhibit the strongest responses to long-day conditions. In the market, ‘Qinmi No. 9’ has gained popularity due to its high sugar content, making it a favored variety among consumers.

The photoperiod sensitivity and fruit set efficiency of 'Qinmi No. 9' passion fruit were systematically evaluated in our study. While we did not measure final fruit yield per se, our classification of Stage IV flower buds (fully differentiated buds capable of anthesis) serves as a validated proxy for reproductive success.

Passion fruit exhibits a unique reproductive architecture where each node produces tendrils flanked by one or multiple floral primordia. Under suboptimal conditions (e.g., low light, temperature extremes), these primordia frequently abort, leading to significant yield losses. Our study specifically targeted this developmental bottleneck by investigating interventions to mitigate environmental stress-induced floral arrest and promote bud maturation to Stage IV. The combined supplemental lighting and foliar phosphorus treatment significantly enhancing bud enlargement and transition to reproductive competence.

 

Point 3: Clarify why you are applying potassium phosphate? You don't discuss this influence anywhere afterward and it's only in the first part of the experience.

Response 3: We sincerely appreciate the reviewer’s insightful question regarding the inclusion of potassium phosphate (KH₂PO₄) in our experimental design. The rationale for testing KH₂PO₄ alongside Plant-Prod (10:52:10 NPK) was to isolate the specific role of phosphorus (P) in flowering regulation, as KH₂PO₄ provided a standardized P-source (200 mg/L) for comparative analysis (see Page 2, line 96 in the revised manuscript).

 

Point 4: In Fig 2a, salt increases the index - new lateral branches . Is this how potassium works?

Response 4: Thanks for your comments. The observed increase in lateral branch formation under KH₂PO₄ treatment may be associated with K⁺-mediated osmotic regulation and the activity of sucrose transporters; however, this does not rule out the potential role of phosphorus (P) in this process. Since our study did not investigate this mechanism in depth, further experiments are needed to validate the respective contributions of K and P to this phenotypic response.

 

Point 5: Part Materials and methods are sufficiently presented. Is it possible to measure natural light ?

Response 5: We appreciate the reviewer's valuable suggestion regarding natural light measurement. In our study, due to daily weather variations, statistical analysis revealed that the light intensity inside the greenhouse was mostly below 200 μmol·m⁻²·s⁻¹.

 

Point 6: The green color and red color of the arrows in the graphic abstract is what, clarify.

Response 6: Thank you for your comments. We have revised the figure caption for Figure 8 in the revised manuscript (see Page 10, line 341 in the revised manuscript).

 

Point 7: Clarification and correction is required throughout the text. For example potassium phosphate. Yield losses due to lack of light, etc. This would emphasize the relevance of the study.

Response 7: Thank you for your comments. In the revised manuscript, revisions were made to the discussion of yield and the role of potassium dihydrogen phosphate (KH₂PO₄), which are reflected in Section 1. Introduction (see Page 2, line 45 in the revised manuscript) and Section 2.1. Plant materials and growth conditions (see Page 2, line 96 in the revised manuscript).

 

Author Response File: Author Response.pdf

Round 2

Reviewer 3 Report

Comments and Suggestions for Authors

The authors have done a great job. At this point, the article has become more understandable and the value of the research itself has been revealed. The authors have taken into account all my comments and remarks and included them in the text. This has satisfied all my requests.