Alleviation of Chilling Injury in Postharvest Sweet Basil (Ocimum basilicum L.) with Silicon and Abscisic Acid Applications
Round 1
Reviewer 1 Report
Comments and Suggestions for AuthorsThe manuscript demonstrates a clear understanding of the project at hand, though it still has some issues. A major revision is recommended before reconsideration for review. My detailed comments are as follows:
- In the 94th line, why is it necessary to arrange and rotate the planted sweet basil randomly? Does this ensure that all sweet basil plants receive the same amount of nutrients, water, and light?
- There is no need to repeatedly duplicate all the treatment methods.
- In the section of FWL (Fresh Weight Loss), the article indicates that Si-irrigation + DI and Si-spray+ DI have effective results in preventing fresh weight loss. However, according to the data in Table 2, DI-spray + DI shows values very close to those of Si-irrigation + DI and Si-spray + DI, and all three have a significant difference labeled as ‘c’. How does this demonstrate that Si-irrigation + DI and Si-spray + DI possess good efficacy in preventing fresh weight loss?
- In section 3.1.4, was the judgment that DI-spray + DI and Si-irrigation + DI show little difference based on the Log-Rank test? Is a numerical difference of 15 between the two not considered significant?Canthe log-rank test precisely express the association of a single factor?
- In section 3.2.4, was the observation of no significant difference made by the naked eye? Experimental conclusions should be supported by precise experimental procedures and data.
- In the discussion section of the manuscript, it is appropriate to condense the content slightly.
Author Response
Comment (C) 1. In the 94th line, why is it necessary to arrange and rotate the planted sweet basil randomly? Does this ensure that all sweet basil plants receive the same amount of nutrients, water, and light?
Response (R): Yes, it was to mitigate effects from potential environmental variations across a bench such as lighting differences.
C2: There is no need to repeatedly duplicate all the treatment methods.
R: The repeated treatment explanations have been removed from figure/table captions.
C3. In the section of FWL (Fresh Weight Loss), the article indicates that Si-irrigation + DI and Si-spray+ DI have effective results in preventing fresh weight loss. However, according to the data in Table 2, DI-spray + DI shows values very close to those of Si-irrigation + DI and Si-spray + DI, and all three have a significant difference labeled as ‘c’. How does this demonstrate that Si-irrigation + DI and Si-spray + DI possess good efficacy in preventing fresh weight loss?
R: Although the Si-irrigation+DI and Si-spray+DI treatments consistently performed better than the control treatment (CK) throughout much of the cold storage test (from day 6-14), they were not significantly different from the other treatments consistently. A few other treatments also showed significantly lower FWL compared to CK, although observed on fewer days, and DI-spray+DI performed on par with the Si treatments throughout most of cold storage. As such, it cannot be concluded whether Si applications have an impact on FWL in postharvest basil based on the results. It is possible there is another factor influencing these results which our study did not determine. This section and the discussion have been revised to better reflect this
C4. In section 3.1.4, was the judgment that DI-spray + DI and Si-irrigation + DI show little difference based on the Log-Rank test? Is a numerical difference of 15 between the two not considered significant? Can the log-rank test precisely express the association of a single factor?
R: Section 3.1.4 is about leaf electrolyte leakage (LEL), results pictured in Figure 4, and used ANOVA and Tukey’s test. If referring to these results, an ANOVA determined that there is a significant effect on LEL from the treatments and the Tukey’s post-hoc test determined that those two treatments did not significantly differ from one another.
The log-rank test was only used for the CII scores in section 3.1.2 and showed that the difference in survival (or in this case shelf life/when the acceptable CII score was exceeded) between those two treatments was significant. If referring to these results, the log-rank test determines whether the treatments significantly affected survival. While it does not quantify/estimate the effect size (how much a treatment affects shelf life) or magnitude (how much longer shelf life extends), it is sufficient for determining whether or not the treatments significantly extend shelf life and can compare their survival curves.
C5. In section 3.2.4, was the observation of no significant difference made by the naked eye? Experimental conclusions should be supported by precise experimental procedures and data.
R: This section has been reworded for better clarity. Leaf electrolyte leakage (LEL) was only measured if the visible symptoms (CII scores for leaf necrosis) showed significant differences among treatments. It was not LEL that showed no significant differences among treatments but the CII scores.
LEL can be an indication of membrane permeability and potentially explain differences in the severity of leaf necrosis as supporting evidence of what may be the cause/contributing factor to the differences. In the wollastonite trial, all the treatments exceeded the acceptable CII score of 2 by day 4 and had no significant differences among them. Thus, it was decided that LEL would not be measured since there was no alleviation in chilling injury observed.
C6. In the discussion section of the manuscript, it is appropriate to condense the content slightly.
R: This section has been revised to be shorter.
We thank you for your dedication and good advices for improving our manuscript!
Reviewer 2 Report
Comments and Suggestions for AuthorsThis manuscript presents the results of research on the influence of treatment with silicon and abscisic acid on the preservation of the quality of basil after harvest, especially during storage at a temperature of 3.5 °C.
Experiments were conducted to test the application of silicon in the form of a potassium-silicate solution (K₂SiO₃) through watering and spraying the leaves, with additional application of ABA before harvest. Also, an experiment was conducted adding wollastonite (natural calcium silicate) to the substrate in different concentrations. The experimental design is fully adequate. Evaluation of treatment effects was done based on cold injury index (CII), fresh weight loss (FWL) and cell membrane permeability (LEL).
There are similar studies examining the influence of silicon (Si) and abscisic acid (ABA) on reducing cold damage and improving the postharvest quality of various plants, primarily vegetables. For example, Wu et al. (2017), Liu et al. (2009) Habibi (2015, 2016), Castro-Cegrí et al. (2023), Guo et al. (2012), while only Satpute et al. (2019) tested ABA on basil during storage at 3.5 °C and showed that it delayed cold damage symptoms.
Although there are studies that investigate silicon or ABA individually, few directly compare them, which adds value to this research.
In any case, I suggest accepting this manuscript for publication in Agriculture.
However, before that I ask the authors to do a major revision of the manuscript, according to the comments below.
In the Introduction, explain in more detail the economic consequences of cold damage in basil, particularly in the context of market supply and supply chain losses.
Although the effects of silicon have been analyzed in detail, it would be useful to explain in more depth why ABA has a weaker effect. Is the reason the frequency of application, the method of absorption or something else?
Regarding wollastonite, please consider whether a longer period of application or a different granulation may give better results.
Please indicate, are these methods practical for commercial application? Can adding silicon to irrigation water be economical for producers?
Graphs and tables are useful, but adding more illustrations or pictures showing differences in leaf damage between treatments may improve visual clarity (not necessary). However, Figures 2, 3 and 4 should be adapted to the rest of the manuscript. Figure 2 illustrates important information, however the individual figures are small and unclear, instead of 3x2, form them as 2x3, and enlarge them as you do so. Figure 3 is inappropriately large, please adjust. Figure 4 is particularly large, please adjust.
In terms of potential directions for further research, suggest experiments, for example with different storage temperatures or combining silicon with other treatments (eg controlled atmosphere, bio-preparations) to test the wider applicability of the results obtained in this research.
Author Response
Comment (C) 1. In the Introduction, explain in more detail the economic consequences of cold damage in basil, particularly in the context of market supply and supply chain losses.
Reply (R): Lines 30-33 discusses economic consequences from shorter shelf lives and lower marketability (lower commercial quality) due to the development of chilling injury symptoms. The symptoms inevitably lead to postharvest losses and reduced profits from product not meeting quality standards or lasting long enough to be sold.
Unfortunately, there are no studies or statistics found with exact numbers or estimates on postharvest losses for sweet basil from chilling injury. Estimating this is difficult since by the time products arrive to retailers, the exact cause of spoilage cannot be discerned. Although it has not been well quantified, based on what is known about chilling injury’s effect on shelf life and product quality of sweet basil, it is a believed to be a concern and contributor to the postharvest losses and thus economic losses.
C2. Although the effects of silicon have been analyzed in detail, it would be useful to explain in more depth why ABA has a weaker effect. Is the reason the frequency of application, the method of absorption or something else?
R: Good suggestions. Now, Lines 522-549 discusses the reason for the lower efficacy of ABA being potentially due to the frequency of the application (only once for ABA). It discusses that ABA has been shown in another study to induce leaf senescence. If true, this potentially limited ABA’s chilling injury alleviation effects, resulting in a lower efficacy compared to Si. Our results also showed that ABA caused leaf abscission and we have mentioned in the revised manuscript.
C3. Regarding wollastonite, please consider whether a longer period of application or a different granulation may give better results.
R: Lines 516-521 discusses the possibility of needing a finer formulation of wollastonite, such as micronized wollastonite, to provide better results.
In terms of a longer period of application, a longer cultivation period could potentially allow wollastonite more time to break down and release more silicic acid. However, greenhouse productions of basil will typically harvest basil within 6-8 weeks after seeding. As such, our study also harvested 8 weeks after seeding to best align with industry standards.
C4. Please indicate, are these methods practical for commercial application? Can adding silicon to irrigation water be economical for producers?
R: Yes, both foliar spray applications and amendments to irrigation solutions (water or nutrient solutions) are practical for commercial productions.
Greenhouse operations, such as the local greenhouse vegetable producer we are currently working with, already have the materials and infrastructure needed to use either method. Nutrient solutions used in greenhouse productions for irrigation are often mixed in tanks and delivered via subirrigation, drip irrigation, or boom. Silicon can be easily added to those solutions like how other nutrients/fertilizers are. Some productions may have automatic/mechanized system for foliar spraying, however even ones that do not can still manually spray the silicon solution using backpack sprayers or other similar products. This means the actual application process should not be a major financial burden or labour intensive.
The cost of the Si product used and the amount needed to make the solution are both on the low end. The foliar spray application was only done once a week while seeing positive results in postharvest cold storage. As such, we don’t expect there would be unreasonably high costs for growers using the described method in the study.
C5. Graphs and tables are useful, but adding more illustrations or pictures showing differences in leaf damage between treatments may improve visual clarity (not necessary). However, Figures 2, 3 and 4 should be adapted to the rest of the manuscript. Figure 2 illustrates important information, however the individual figures are small and unclear, instead of 3x2, form them as 2x3, and enlarge them as you do so. Figure 3 is inappropriately large, please adjust. Figure 4 is particularly large, please adjust.
R: Figure 2 has been revised to be arranged in 2x3, with the individual photos being more enlarged.
Figures 3 and 4 have been revised to be smaller in size.
C6. In terms of potential directions for further research, suggest experiments, for example with different storage temperatures or combining silicon with other treatments (eg controlled atmosphere, bio-preparations) to test the wider applicability of the results obtained in this research.
R: Conclusion has been revised to provide more detailed suggestions for future studies.
We thank you for your good work and advices for improving our manuscript!
Round 2
Reviewer 1 Report
Comments and Suggestions for AuthorsWell done！
Reviewer 2 Report
Comments and Suggestions for AuthorsFrom a review of the corrected paper, it is evident that the reviewer's comments have been taken into account and the manuscript has been improved in all key aspects.
