Review Reports - Particle Film Improves the Physiology and Productivity of Sweet Potato without Affecting Tuber’s Physicochemical Parameters

Round 1

Reviewer 1 Report

MDPI agriculture-1618117

In general, this is an interesting article, which shows that CaO film on sweet potato can increase yield. The English is poor in some places and should be improved prior to publication. Also, a number of measurements were made on the plants, but it is not clear what they tell us about the consequences of the CaO film. There should be a specific reason to measure each of the variables that were reported. Moreover, the results (Figures 3, 4 & 5, for example) are internally inconsistent (see specific comment below).

Line 21. There were actually four CaO concentrations. The authors should include 0 (control) as one of the four.

Lines 23-24. It is not clear to me what carboxylation is. In the materials and methods this quantity is given as μmol CO2 mol air-1, which is a concentration, not a content. Moreover, the authors do not specify where this quantity was measured and how it was measured or, for that matter, what meaning it has.

Line 33. Climate does not limit a niche. Climate preferences are one of many factors that help to define a niche. Organisms do not fit into niches. They possess niches. In other words, the niche is a property of the species, not a property of the habitat.

Line 40. Particle films cannot protect plants against high temperatures caused by high air temperatures. They can only protect plants against high temperatures caused by high irradiance

Line 41. “may” exhibit

Line 50. The word “rainfall” is problematic here. Obviously, rainfall can be a good thing. Rainfall is not always a stress.

Lines 80-81. “whenever when the luminosity was reduced on leaves” is not a very clear statement. How much luminosity reduction was necessary before the particle film was reapplied? When the suspensions were applied, were they applied until they began to runoff of the leaf surfaces? Would it be better to refer to luminosity as reflectance?

Line 103. What is meant by “carbon content”? Do they mean leaf intercellular CO2 concentration? If that is correct, the results are somewhat self contradictory. If the leaf intercellular CO2 concentration is higher in T3 than in control, this implies an impaired chloroplast, but then how is it possible to have increased yield?

Line 112. What is meant by instantaneous carboxylation efficiency? Again, I do not understand the concept of “carbon content”. You will have to explain this term.

Lines 121-138. The authors should explain why these variables were measured. Do they affect flavor, nutrition, marketability?

Figure 3. The units for the Y axes are usually given in the figures, not in the caption. I do not know what this journal requires. Someone should look into this. Some of these results do not make sense. First, the leaf temperature is lowest for T3, but these do not have the highest transpiration rates and therefore are not evaporating water the most rapidly. Second, the stomatal conductance is intermediate for T3, but photosynthesis rate is lowest. How do the authors make sense of this?

Figure 4. I do not see how it is possible for the pattern of “intrinsic WUE” and “WUE” to differ because stomatal conductance should be proportional to transpiration rate.

Figure 5. Productivity is lowest in the control and T1, and highest for T2 and T3. On the other hand, photosynthesis was highest in control and lowest in T3. How is that possible?

Discussion.

It is clear that the film can have a significant impact on productivity. Presumably the authors made many physiological measurements in order to determine the mechanism of this impact. But I feel that these physiological measurements were not interpreted correctly. For example, the authors write:

“The CaO particle films seem to protect sweet potato plants during warm conditions, such as luminous stress, maintaining their photosynthetic rate despite reducing stomatal conductance. For instance, control plants presented higher stomatal conductance, and in contrast, the photosynthetic rate remained similar for all CaO treatments, except at 15% w/v. This result indicates an improvement in light absorption and distribution in CaO treated sweet potato plants, reflecting visible and ultraviolet radiation, which reduced the leaves' thermal tension [22–24].”

These statements are self-contradictory. The authors seem to ignore the fact that T3 had significantly lower stomatal conductance and photosynthesis rate than the control and yet T3 had higher yield than the control. They do not seem to be able to explain this.

The authors also write:

“We observed an increase in carboxylation efficiency at CaO 10% w/v due to the high internal concentration of CO2 associated with a reduction of stomatal conductance that indicates an enhancement of the carboxylation [29].”

But this does not make sense. A high internal concentration of CO2 implies a problem with carboxylation, not an enhancement of carboxylation.

Author Response

Dear Reviewer 1, we did a more detailed reading of the manuscript and verified that some terms really needed to be changed so that the text could be better understood. We hope they are enough and that they meet your expectations. Below are the justifications related to its correction.

L 80-81: To evaluate the luminosity, we use a device called a colorimeter, which measures the light reflected from objects at each wavelength or in specific bands. One of these parameters is luminosity (or *L), expressed on a scale from 0 (total light absorption) to 100 (total light reflection). This evaluation allows us to associate the reflective properties of the leaves. Regarding the change of the term, from luminosity to reflectance, it would certainly be more appropriate, but the equipment provides us with the variable as luminosity and that is why we follow the manufacturer's recommendations. It is worth mentioning that this evaluation allowed us to estimate the moment of reapplication of the particle film, which, as detailed in the materials and methods, took place every 15 days. Furthermore, the application was made so that the entire surface of the sheet was completely covered by the film. As it is a suspension, applied via spray, the leaves were well wet and after drying the product they were as shown in Figure 2.

L 103 and Figure 5: “Carbon content” refers to the internal carbon. We understand that photosynthesis is a complex process and that several variables contained in this process can help increase productivity. In fact, T3 has higher internal carbon compared to the control, which may be related to abiotic stress. However, it is possible to verify that in the control treatment the plants had higher leaf temperature, lower carboxylation efficiency and lower intrinsic efficiency of water use (Figures 3 and 4). This result suggests that although T3 increased internal carbon, there was also a reduction in leaf temperature, which in a way may have contributed to the increase in carboxylation efficiency and the intrinsic efficiency of water use, providing thermal comfort in the plants. leaves.

L 112: Carboxylation efficiency is a variable calculated by dividing the photosynthetic rate by the carbon content.

L 121: It is known that any stress, or change in management, performed on plants, consequently affect the fruits in a qualitative way. Therefore, we think it is important that in scientific studies that evaluate the effects of the application of products on the leaves, physical-chemical evaluations related to the quality of the fruit are included. Because, these variables provide important information for marketing, nutrition and storage of production.

Figure 3: The magazine does not specify how the figure axis should be placed. The results referring to Figure 3, were better discussed in the 2nd and 3rd paragraphs of the discussion.

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and recommendations

The authors have studied the issues of improving the elements of productivity management technology, as well as the search for mechanisms of adaptation of agricultural plants in the conditions of abiotic stressors

Few comments to improve the manuscript:

Whether preparations containing calcium or CaO have been used on root crops before and what preliminary results have been obtained.
Enhance the relevance of the studied problem
How correct is it to use CaO doses developed for coffee plants (perennial crops), for root crops (annual crops) and, in particular, for Sweet potato (Ipomoea batatas)?
If I understand correctly, the data you have is one-year and maybe it makes sense to talk about preliminary results?
I propose to replace paragraphs 2.3 and 3.2 with physiological and biochemical parameters
How will the authors be able to scientifically substantiate, due to which there is an increase in carbon content, high efficiency of carboxylation, increased productivity of Sweet potato and a decrease in its photosynthesis rate when using 10% CaO?
Some of the information "Discussion" is more related to "Results". In this regard, I propose in the Discussion section to add more information about the comparison of the data obtained by the authors with the results of other scientists in relation to root crops
It is too early to talk about recommendations in the conclusions. The positive result of using a 10% CaO solution should be confirmed by at least three-year data and on the 4-5 cultivars.

Author Response

Dear Reviewer 2, we reorganized the text to be better understood and answered your questions. We hope they are enough and that they meet your expectations. Below are the reasons for your observation.

Whether preparations containing calcium or CaO have been used on root crops before and what preliminary results have been obtained.

The sweet potato crop was the first we worked with as a root crop. But as previous results we have the following publications:

OLIVEIRA, ALEXANDRE PASSOS; FONTES, PRYANKA THUYRA ; MACIEL, LAILA BEATRIZ SANTOS ; FAGUNDES, JAILSON LARA ; CARNELOSSI, MARCELO AUGUSTO GUTIERREZ ; OLIVEIRA JÚNIOR, LUIZ FERNANDO GANASSALI DE . Physiological performance, bromatological quality, and productivity of sweet potato using calcium oxide particle film. PESQUISA AGROPECUÁRIA BRASILEIRA (ONLINE), v. 56, p. e01789, 2021.

OLIVEIRA, A.P; Santos, A. A. ; FONTES, P. T. N. ; CARNELOSSI, M. A. G. ; FAGUNDES, J. L. ; OLIVEIRA JUNIOR, L. F. G. . Calcium particle film improves sweet potato growth and partitioning. Pesquisa Agropecuaria Tropical (Online), v. 51, p. e67814,, 2021.

OLIVEIRA, ALEXANDRE PASSOS; DINIS, LIA-TÂNIA ROSA ; BARBOSA, NADJA TAMIRES BORGES ; DE MATTOS, ELOY COSTA ; FONTES, PRYANKA THUYRA NASCIMENTO ; CARNELOSSI, MARCELO AUGUSTO GUTIERREZ ; FAGUNDES, JAILSON LARA ; DA SILVA, ELIZAMAR CIRÍACO ; DE OLIVEIRA JUNIOR, LUIZ FERNANDO GANASSALI . Calcium particle films promote a photoprotection on sweet potato crops and increase its productivity. Theoretical and Experimental Plant Physiology, v. 33, p. 29-41, 2020.

How correct is it to use CaO doses developed for coffee plants (perennial crops), for root crops (annual crops) and, in particular, for Sweet potato (Ipomoea batatas)?

Our team has worked with different crops (tomatoes, grapes, coffee, mini squash, strawberries and soybeans) and not just coffee. Thus, to reference the concentrations used in this work, we took into account the experience in other cultures and preliminary tests involving photosynthesis.

If I understand correctly, the data you have is one-year and maybe it makes sense to talk about preliminary results?

We carried out preliminary tests to determine the best concentrations of particle film for the sweet potato crop, before these study.

I propose to replace paragraphs 2.3 and 3.2 with physiological and biochemical parameters.

Physiological and Biochemical Parameters

How will the authors be able to scientifically substantiate, due to which there is an increase in carbon content, high efficiency of carboxylation, increased productivity of Sweet potato and a decrease in its photosynthesis rate when using 10% CaO?

In fact, the photosynthetic rate did not differ statistically for the control, 5% and 10% of particle film (Figure 3), showed the same photosynthetic rate.

It is too early to talk about recommendations in the conclusions. The positive result of using a 10% CaO solution should be confirmed by at least three-year data and on the 4-5 cultivars.

We will exclude from the conclusion: Thus, we recommend its application to enhance sweet potatoes cultivation

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

The authors did not address many of my comments from the previous review, including these:

Line 112. What is meant by instantaneous carboxylation efficiency? Again, I do not understand the concept of “carbon content”. You will have to explain this term.

Lines 121-138. The authors should explain why these variables were measured. Do they affect flavor, nutrition, marketability?

Figure 3. The units for the Y axes are usually given in the figures, not in the caption. I do not know what this journal requires. Someone should look into this. Some of these results do not make sense. First, the leaf temperature is lowest for T3, but these do not have the highest transpiration rates and therefore are not evaporating water the most rapidly. Second, the stomatal conductance is intermediate for T3, but photosynthesis rate is lowest. How do the authors make sense of this?

Figure 4. I do not see how it is possible for the pattern of “intrinsic WUE” and “WUE” to differ because stomatal conductance should be proportional to transpiration rate.

Figure 5. Productivity is lowest in the control and T1, and highest for T2 and T3. On the other hand, photosynthesis was highest in control and lowest in T3. How is that possible?

Discussion.

The authors also write:

But this does not make sense. A high internal concentration of CO2 implies a problem with carboxylation, not an enhancement of carboxylation.

Author Response

JUSTIFICATIONS

To the Editor-in-Chief and Reviewer

Linhas 80-81.

when ``L`` showed 20% reduction in the initial application. To evaluate the luminosity, we use a device called a colorimeter, which measures the light reflected from objects at each wavelength or in specific bands. One of these parameters is luminosity (or *L), expressed on a scale from 0 (total light absorption) to 100 (total light reflection). This evaluation allows us to associate the reflective properties of the leaves. Regarding the change of the term, from luminosity to reflectance, it would certainly be more appropriate, but the equipment provides us with the variable as luminosity and that is why we follow the manufacturer's recommendations. It is worth mentioning that this evaluation allowed us to estimate the moment of reapplication of the particle film, which, as detailed in the materials and methods, took place every 15 days. Furthermore, the application was made so that the entire surface of the sheet was completely covered by the film. As it is a suspension, applied via spray, the leaves were well wet and after drying the product they were as shown in Figure 2.

Line 103.

Yes, carbon content is the intercellular carbon in the leaf measured by the IRGA. What happened with T3 (15%) was that the film promoted an excess of coverage reducing light absorption, which caused a drop in photosynthesis, which did not happen with T2 (10%). However, a reduction in leaf temperature was observed, with the reduction in temperature, it was not necessary to perform as much osmotic regulation (energy expenditure) as in T1, which was more exposed to solar radiation and temperature. Consequently, T3, because it needs less regulation, did not need greater stomatal conductance than T1, that is, it optimized stomatal opening. As for the photosynthesis-productivity relationship, it is known that many times it does not have a direct relationship, as it depends a lot on the needs of the plant at the moment. Like when they are experiencing stress, for example. As for a higher Ci rate, it may indicate that there is no strong demand for the biochemical (dark) phase, the plant is optimized. In this case, T3 is not the main focus of this article and we have already verified in other works that when the film concentration is very high, some adverse results occur, but we are already studying.

Line 112.

The instantaneous efficiency of carboxylation (EiC) is closely related to the intracellular concentration of CO2 and the rate of assimilation of carbon dioxide.. It can also be determined by the speed at which the fixed CO2 is processed, being limited mainly by the amount and enzymatic activity and the availability of CO2, there are also other factors that influence the carboxylation efficiency, among them are the concentration of the acceptor, temperature, degree of hydration of the protoplasm, supply of mineral substances and degree of development and activity of the plant.

Lines 121-138.

Any treatment carried out in the field is extremely important that its reflection is evaluated in qualitative terms in the harvested product.. In this case, it is extremely important to check if there has been a change in the color of the product (sweet potato), as the consumer is demanding about the appearance (Colorimeter). Another extremely important attribute for sweet potatoes is firmness, (no one wants a soft, too hard or too hard potato) (Penetrometer). As for the taste, it is important to check the sweetness (Total Soluble Solids, Digital Refractometer) and acidity (Titratable Acidity By Titration). Another extremely important factor for sweet potatoes is the starch content. Thus, these variables provide important information for the marketing, nutrition and storage of sweet potato.

Figure 3.

T3 has a lower leaf temperature because the 15% particle film reflects more solar radiation and the temperature ends up decreasing (the film is white). Thus, there is no need for greater transpiration and consequently there is no greater need for greater stomatal conductance. The photosynthetic rate was reduced due to the greater barrier of the film (more space) due to the lower light absorption. We did pre-tests and verified that as the concentration of the film increases, photosynthesis decreases. That's how we got to these concentrations.

Figure 4.

Unfortunately or fortunately, the particle film causes some changes in the gas exchange of the plant, which we also verified in other works.

Figura 5.

Not all photosynthesis is converted into productivity. Often the plant may have another demand, such as relieving stress.... What happened in T2 and T3 (10 and 15%) was that the film promoted a coverage reducing the absorption of excess light, which caused a small drop in photosynthesis for T2 and greater for T3. However, a reduction in leaf temperature was observed, with the reduction in leaf temperature, the plant did not need to perform as much osmotic regulation (energy expenditure) as in T1, which was more exposed to higher solar radiation and temperature. Consequently, T3, because it needs less osmotic regulation, did not need greater stomatal conductance than T1, that is, the plant optimized the stomatal opening.

Discussion.

“The CaO particle films seem to protect sweet potato plants during warm conditions, such as luminous stress, maintaining their photosynthetic rate despite reducing stomatal conductance. For instance, control plants presented higher stomatal conductance, and in contrast, the photosynthetic rate remained similar for all CaO treatments, except at 15% w/v. This result indicates an improvement in light absorption and distribution in CaO treated sweet potato plants, reflecting visible and ultraviolet radiation, which reduced the leaves' thermal tension [22–24].”

The particle film manages to reduce the excess of solar radiation, here in Brazil, especially in the Northeast region, these rates are extremely high and harmful to C3 plants such as sweet potato. As for T3 (15%) it has a high concentration, an excessive barrier for the plant that ends up absorbing less light than we wanted. However, we also observed that the temperature of T3 was lower and this implies a lower energy expenditure for osmotic regulation and, therefore, lower transpiration and lower stomatal conductance.

The authors also write:

But this does not make sense. A high internal concentration of CO2 implies a problem with carboxylation, not an enhancement of carboxylation.

We believe that the T2 treatment, as it presents more favorable conditions for development and production, with a high photosynthetic rate, lower leaf temperature and lower incidence of solar radiation, the plant did not need to spend on osmotic regulation, combating free radicals, etc. Presenting energy surplus, not having so much demand for the biochemical phase (dark phase). Hence, the greatest accumulation of internal carbon.

Author Response File: Author Response.pdf

Reviewer 2 Report

The authors provided detailed information to the questions of the reviewer. The authors made the necessary edits. Although the question "How will the authors be able to scientifically substantiate, due to which there is an increase in carbon content, high efficiency of carboxylation, increased productivity of Sweet potato and a decrease in its photosynthesis rate when using 10% CaO?" I didn't get a scientifically sound answer. But I think that this question is for future research and the authors will be able to get an answer.

Author Response

JUSTIFICATIONS

To the Editor-in-Chief and Reviewer

Linhas 80-81.

Line 103.

Line 112.

Lines 121-138.

Figure 3.

Figure 4.

Unfortunately or fortunately, the particle film causes some changes in the gas exchange of the plant, which we also verified in other works.

Figura 5.

Discussion.

The authors also write:

But this does not make sense. A high internal concentration of CO2 implies a problem with carboxylation, not an enhancement of carboxylation.

Author Response File: Author Response.pdf